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RISS 인기검색어
- 검색키워드
- 저자 : Nasir Saleem (검색결과 4 건)
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Polarisation insensitive multifunctional metasurfaces based on all-dielectric nanowaveguides
Mahmood, Nasir,Kim, Inki,Mehmood, Muhammad Qasim,Jeong, Heonyeong,Akbar, Ali,Lee, Dasol,Saleem, Murtaza,Zubair, Muhammad,Anwar, Muhammad Sabieh,Tahir, Farooq Ahmad,Rho, Junsuk The Royal Society of Chemistry 2018 Nanoscale Vol.10 No.38
<P>Metasurfaces, two dimensional (2D) metamaterials comprised of subwavelength features, can be used to tailor the amplitude, phase and polarisation of an incident electromagnetic wave propagating at an interface. Though many novel metasurfaces have been explored, the hunt for cost-effective, highly efficient, low-loss and polarisation insensitive applications is ongoing. In this work, we utilise an efficient and cost-effective dielectric material, hydrogenated amorphous silicon (a-Si:H), to create a ultra-thin transmissive surface that simultaneously controls phase. This material exhibits significantly lower absorption in the visible regime compared to standard amorphous silicon, making it an ideal candidate for various on-chip applications. Our proposed design, which works on the principle of index waveguiding, integrates two distinct phase profiles, that of a lens and of a helical beam, and is versatile due to its polarisation-insensitivity. We show how this metasurface can lead to highly concentrated optical vortices in the visible domain, whose focused ring-shaped profiles carry orbital angular momentum at the miniaturised scale.</P>
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Twisted non-diffracting beams through all dielectric meta-axicons
Mahmood, Nasir,Jeong, Heonyeong,Kim, Inki,Mehmood, Muhammad Qasim,Zubair, Muhammad,Akbar, Ali,Saleem, Murtaza,Anwar, Muhammad Sabieh,Tahir, Farooq Ahmad,Rho, Junsuk The Royal Society of Chemistry 2019 Nanoscale Vol.11 No.43
<P>We demonstrate transmission-based all-dielectric, highly efficient (≈73.4%) and polarization-insensitive meta-axicons (for the visible wavelength of 633 nm) to generate zero and higher order Bessel beams without using additional components. The Bessel beams, owing to their diverse applications and non-diffractive properties, attract great interest from the scientific community. It is shown that the propagation length can be increased through a lower numerical aperture (∼2600 <I>λ</I> for NA = 0.1) whereas a higher full width at half maximum (< 0.5 <I>λ</I>) can be obtained for a higher numerical aperture (for NA ≥ 0.7). Our dielectric material, hydrogenated amorphous silicon (a-Si:H), provides a significant efficiency advantage over plasmonic and other high-index all-dielectric (<I>e.g.</I>, TiO2 and GaN) metasurfaces in terms of cost, ease of fabrication, and CMOS compatibility. The finite difference time domain (FDTD) technique based numerically simulated and experimental results show excellent agreement. Due to the technological and scientific importance of the Bessel beams, the recommended material and meta-axicons provide an efficient and compact platform for realizing various advanced applications like optical manipulation, optical alignment, laser fabrication, imaging, and laser machining.</P>
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Hemnishil K. Marella,Nasir Saleem,Claudio Tombazzi 대한소화기내시경학회 2021 Clinical Endoscopy Vol.54 No.2
Background/Aims: The adenoma detection rate (ADR) is used as a quality indicator for screening and surveillance colonoscopy. Thestudy aimed to determine if moderate versus deep sedation affects the outcomes of the ADR and other quality metrics in the veteranpopulation. Methods: A retrospective review of colonoscopies performed at Memphis Veterans Affairs Medical Center over a one-year periodwas conducted. A total of 900 colonoscopy reports were reviewed. After exclusion criteria, a total of 229 index, average-risk screeningcolonoscopies were identified. Data were collected to determine the impact of moderate (benzodiazepine plus opioids) versus deep(propofol) sedation on the ADR, polyp detection rate (PDR), and withdrawal time. Results: Among 229 screening colonoscopies, 103 (44.9%) used moderate sedation while 126 (55%) were done under deep sedation. The ADR and PDR were not significantly different between moderate versus deep sedation at 35.9% vs. 37.3% (p=0.82) and 58.2% vs. 48.4% (p=0.13), respectively. Similarly, there was no significant difference in withdrawal time between moderate and deep sedation(13.4 min vs. 14 min, p=0.56) during screening colonoscopies. Conclusions: In veterans undergoing index, average-risk screening colonoscopies, the quality metrics of the ADR, PDR, andwithdrawal time are not influenced by deep sedation compared with moderate sedation.
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Muhammad Nabeel,Muhammad Ali Nasir,Mariyam Sattar,Rizwan Ahmed Malik,Meshal Alzaid,Muhammad Shoaib Butt,Mohsin Saleem,Hussein Alrobei 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.11
Flexural, tensile, and impact strength of hybrid Kevlar/glass reinforced epoxy composite is studied. Six different types of hybrid composite material were manufactured by hand layup process using different compositions of Kevlar and glass fiber. Tensile, flexural and impact strengths of manufactured samples were investigated using standard tests and compared. It is observed that tensile strength is greater for combinations with higher percentage (%) of Kevlar fabric and decreases with an increase in the glass fabric %age. Flexural strength is higher for combinations with greater %age of glass fabric and decreases with an increase in the Kevlar fabric %age. From drop weight test, it is found from visual inspection that damaged area is increased with an increase in the glass fabric percentage. Numerical simulation model incorporated with elastoplastic material data successfully predicts tensile and flexural experimental results.
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