1,722,689 research outputs found
Hydraulic simulations to evaluate and predict design and operation of the Chashma Right Bank Canal
Full text linkIrrigation systems / Irrigation canals / Flow control / Velocity / Canal regulation techniques / Hydraulics / Simulation models / Design / Operations / Crop-based irrigation / Distributary canals / Water delivery / Policy / Protective irrigation / Water allocation / Water requirements / Sedimentation / Water distribution / Equity / Water conveyance / Pakistan / Chashma Right Bank Canal
Simulation and microfabrication of MEMS vacuum electronic devices for terahertz technology
No full textNumerous applications explore the scarcely used terahertz (THz) band in the electromagnetic spectrum. However, widespread utilization of the THz band is technically challenging, due to the lack of power sources. The power level of the signal generators drastically drops as the frequency approaches the THz frequencies. Moreover, at this frequency range, the attenuation level of electromagnetic waves in the earth atmosphere increases. In vacuum electronics family, traveling wave tube (TWT) has gained particular interest for millimetre-wave and THz signal amplification for high-power and wideband applications. The characteristics of the TWT are mainly represented by the performance of a slow-wave structure (SWS). The SWS in TWT is used to facilitate the input THz signal which gets amplified by the process of the beam-wave interaction. Therefore, an efficient and reliable SWS is an essential aspect of a powerful TWT design.
This thesis proposes a novel SWS, which consists of metal corrugations in the Hplane and E-plane of the rectangular waveguide operated in the fundamental mode. The concept of H-plane and E-plane load shows potential benefits to the THz TWTs, such as excellent linear characteristics, an increased interaction impedance, ultrawide bandwidth, and high-power output. Furthermore, the geometry of the SWS made the fabrication easier by using the available microfabrication techniques. The thesis involves all elements of development from device design, simulations, through material growth and interactive device fabrication to extensive characterization, along with the prototype cold-testing of the scaled-up device.
The proposed SWS is investigated for TWT working at 400 GHz central frequency. The design and simulation of TWT involve three stages, which are high frequency electromagnetic study of a unit cell of the SWS using Eigenmode simulations, scattering parameters or S-parameters analysis of coupler design with the SWS usingtime-domain transient simulations, and beam-wave interaction study using particlein- cell (PiC). The PiC simulations found that this tube can produce an excess of 25 dB small-signal gain with 60 GHz 3-dB bandwidth at 400 GHz central frequency. The LIGA technique was employed to fabricate the 400-GHz E-plane and H-plane loaded SWS. In particular, the KMPR negative tone photoresist was used in the fabrication process. The KMPR mold produced the nearly perfect features of the mask designs, tolerance within the ±2.5 μm of the lateral features and maximum deviation of 20 in the vertical profiles. The experiments for surface roughness study revealed that the interior sidewall roughness of the LIGA-fabricated metal parts was achieved about 20 nm. A diffusion bonding method was employed to attach the two LIGA-fabricated copper parts of the SWS, producing a bonding strength of 25 MPa at 400 0C bonding temperature and with a void-free bonding interface.
A scale-up model of the H-plane and E-plane SWS together with input and output couplers at W-band (85-110 GHz) was designed, manufactured using CNC milling, and verified the electromagnetic characteristics experimentally. The test results of S-parameters agreed with the simulations, S11<-15 dB over a frequency range of 85 GHz - 98 GHz. PiC simulations were also performed to the 93.5-mm length SWS, demonstrating a gain about 24 dB over 89 GHz – 101 GHz. To mitigate the diocotron instability in the sheet-beam transmission, a modified geometry of the sheet beam was employed and analysed through PiC simulations. The robust design and high performance from the H-plane and E-plane loaded SWS suggests that this is a promising candidate for high-power and wideband TWT development in the millimetre and THz frequency ranges
CCDC 2043113: Experimental Crystal Structure Determination
No full textRelated Article: Muhammad Nadeem Akhtar, Murad A. AlDamen, Colin D. McMillen, Albert Escuer, Júlia Mayans|2021|Inorg.Chem.|60|9302|doi:10.1021/acs.inorgchem.0c0368
CCDC 2043111: Experimental Crystal Structure Determination
No full textRelated Article: Muhammad Nadeem Akhtar, Murad A. AlDamen, Colin D. McMillen, Albert Escuer, Júlia Mayans|2021|Inorg.Chem.|60|9302|doi:10.1021/acs.inorgchem.0c0368
CCDC 2043112: Experimental Crystal Structure Determination
No full textRelated Article: Muhammad Nadeem Akhtar, Murad A. AlDamen, Colin D. McMillen, Albert Escuer, Júlia Mayans|2021|Inorg.Chem.|60|9302|doi:10.1021/acs.inorgchem.0c0368
PRINCIPLES, NORMS AND STRATEGIES OF THE US GLOBAL CYBERSPACE GOVERNANCE
Full text linkThis study examines the United States\u27 (US) approach to global cyber governance, including the principles, strategies, and norms the US intends to promote in cyberspace. This also discusses why the US is unwilling to share cyberspace governance with other great powers. While utilizing the official policies and strategies of the US as primary sources, this study identifies that the core principles of US cyber governance encompass a free and open internet, a multi-stakeholder approach, collaboration with allies, and maintaining a stable and secure digital landscape. However, it is criticised for its approach to data privacy, the Internet Corporation for Assigned Names and Numbers (ICANN) control, mass surveillance programs against foes and allies, and its disagreement with other states on cyberspace governance.
Bibliography Entry
Ashraf, Nageen and Muhammad Nadeem Mirza. 2025. "Principles, Norms and Strategies of the US Global Cyberspace Governance." Margalla Papers 29 (1): 41-54
Direct Numerical Simulation of Turbulent Boundary Layer over Sparsely Spaced Rod Roughened Wall
No full textGeographical Variations in Implementing Result-Based Management to School Improvement Plans in Punjab's Public Secondary Schools
No full text<p>This research examines geographical variations in the implementation of School Improvement Plans (SIPs) utilizing a Results-Based Management (RBM) approach in public secondary schools across Punjab. The study aims to identify differences among districts, focusing on the practices and perceptions of head teachers and senior school teachers regarding the use of RBM in SIPs. Data was collected through surveys, employing a descriptive research methodology. The findings reveal significant success in central Punjab, where schools' physical and co-curricular environments have benefitted markedly from the application of RBM, fostering a positive perception of SIP achievements among educators. The study suggests enhancing alignment between RBM and SIP indicators and improving communication among schools, communities, and stakeholders, advocating the use of ICT technologies to facilitate these improvements.</p>
Monetary and fiscal policies coordination - Pakistan's experience
Full text linkThe paper explores how the monetary and fiscal policies have coordinated with each other in Pakistan. It argues that monetary and fiscal policies have been executed independently throughout the study period that is 1964-65 to 2008-09 and there have been very few instances of coordination between the two policies while addressing prevailing economic conditions. The paper does not find any difference between the behavior of monetary and fiscal policies before and after the establishment of Monetary and Fiscal Policies Coordination Board in 1994. Whatever instances of coordination were found were clustered in military regimes; which may be one of the reasons of macroeconomic stability in such regimes.Monetary Policy, Fiscal Policy,
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