Asif Khan - Academia.edu (original) (raw)

Papers by Asif Khan

IEEE Transactions on Microwave Theory and Techniques, 2003

Pakistan Journal of Botany, 2008

Eight photosynthetic Arabidopsis mutants were screened for co-segregation of a photosynthetic phe... more Eight photosynthetic Arabidopsis mutants were screened for co-segregation of a photosynthetic phenotype with the T-DNA insertion. These mutants were selected from 80 photosynthetic mutants with genetic background of Columbia-0. Two different screening approaches were used to study the T-DNA insertion in the genome of mutant Arabidopsis lines. The sulphonamide sulfadiazine was found to be an effective selective agent and a single copy of sulfonamide resistant gene was found to be completely resistant to the optimal concentration i.e., 5mg mL -1 . The maximum number of Arabidopsis mutant plants had confirmed insertions. Some of the plants did not show any amplification with gene specific primer combination, and it was assumed that either they were wild type plants or they had random T-DNA insertion and the insertion was not found in the gene under study but it could be found in any where in the genome. Some mutant plants were morphologically different from the wild type plants e.g., A...

The 11th IEEE International Symposium on Electron Devices for Microwave and Optoelectronic Applications, 2003. EDMO 2003.

Strain and polarization control achieved via strain energy band engineering is the key for achiev... more Strain and polarization control achieved via strain energy band engineering is the key for achieving stable and reliable operation of wide bad gap devices. In this paper, we consider the application of this approach to novel AlN/GaN/InN-based field effect transistors and ultraviolet light emitting diodes.

Complex Analysis and Operator Theory, 2016

In this paper, we introduce a Kantorovich type generalization of q-Bernstein-Stancu operators. We... more In this paper, we introduce a Kantorovich type generalization of q-Bernstein-Stancu operators. We study the convergence of the introduced operators and also obtain the rate of convergence by these operators in terms of the modulus of continuity. Further, we study local approximation property and Voronovskaja type theorem for the said operators. We show comparisons and some illustrative graphics for the convergence of operators to a certain function.

Mathematical Methods in the Applied Sciences, 2015

In the present research article, we introduce the King's type modification of q-Bernstein-Kantoro... more In the present research article, we introduce the King's type modification of q-Bernstein-Kantorovich operators and investigate some approximation properties. We show comparisons and present some illustrative graphics for the convergence of these operators to some function.

Genetics and molecular research : GMR, Jan 7, 2007

The degree of genetic divergence was estimated in seven wheat genotypes, six exotic genotypes and... more The degree of genetic divergence was estimated in seven wheat genotypes, six exotic genotypes and one local variety, through random amplified polymorphic DNA methodology. A total of 112 DNA fragments were generated by the 15 random primers, with an average of about 7.4 bands per primer. Among the 112, 50 fragments showed polymorphism among the seven wheat genotypes. Nei and Li's similarity matrix ranged from 86.2 to 93.0%, which indicated a narrow genetic base among the genotypes. The maximum similarity, 93.0%, was observed between 12WLRG/1-12 and WL-43. The local variety, Chenab-70, showed the lowest similarity with the exotic types. We conclude that random amplified polymorphic DNA analysis can be used for the characterization and grouping of wheat genotypes; these results will be helpful in our wheat breeding program.

2006 International Conference on Advances in Space Technologies, 2006

The stratosphere is one of the constituents of thermal structure of the atmosphere. The maximum c... more The stratosphere is one of the constituents of thermal structure of the atmosphere. The maximum concentration of ozone is found at the stratospheric region where it is interacted by many species including chemical and physical processes. Atmosphere as a whole is an open system that is regarded as a non linear system and that seems to be complex. Therefore, a non-linear trend is plausible to explain phenomenon of ozone layer depletion (OLD). In this manuscript we have paid our attention is the analysis of the major portion of historic data on stratospheric O3 based on ground-based measurements by the Dobson spectrophotometer. In this communication we have estimated parameters for describing non-linearity in the process using polynomial trend functions and predicted values are calculated for the period from 1960 to 1999. Future values for ozone depths are computed till 2006 and compared with the minor portion of the data set

Mathematical and Computer Modelling, 2012

The concepts of equi-statistical convergence, statistical pointwise convergence and statistical u... more The concepts of equi-statistical convergence, statistical pointwise convergence and statistical uniform convergence for sequences of functions were introduced recently by Balcerzak et al. [M. Balcerzak, K. Dems, A. Komisarski, Statistical convergence and ideal convergence for sequences of functions, J. Math. Anal. Appl. 328 (2007) 715-729]. In this paper, we use the notion of λ-statistical convergence in order to generalize these concepts. We establish some inclusion relations between them. We apply our new notion of λ-equistatistical convergence to prove a Korovkin type approximation theorem and we show that our theorem is a non-trivial extension of some well-known Korovkin type approximation theorems. Finally, we prove a Voronovskaja type approximation theorem via the concept of λ-equi-statistical convergence. Some interesting examples are also displayed here in support of our definitions and results.

Horticulture, Environment, and Biotechnology, 2013

For the perfume industry, Rosa damascena is the most important species used in the production of ... more For the perfume industry, Rosa damascena is the most important species used in the production of rose attar which is made by distilling volatile oils from the petals of flowers. It is also used widely in the manufacture of rose water, as a flavoring agent. Other species like Rosa gallica L., Rosa centifolia L., Rosa × borboniana Desp. and the rose cultivar Gruss an Teplitz also exhibit the fragrance that is sought by perfumeries in the world. The main rose oil producers in the world are Turkey and Bulgaria, and they are obtaining the rose oil almost exclusively from the single clone of R. damascena. In the recent studies a wide genetic diversity for R. damascena has been revealed in Iran, but there was a need to explore and evaluate the R. damascena in the neighboring areas of Iran. Thus the new research project was planned with the objective to evaluate the genetic diversity amongst R. damascena landraces grown in Pakistan and the subsequent comparison with tested germplasm grown in Iran. Further, the study is based on the collection of Damask and selected garden roses from Pakistan, Iran and USA, determining the characterization through microsatellite markers. The SSR markers confirmed the high level of diversity of the Rosa damascena germplasm within Iran and showed that the Pakistani genotypes were similar to those from the Iranian provinces of Isfahan, Kerman and Fars. The garden rose cultivars were distantly related.

Japanese Journal of Applied Physics, 2001

Novel, current collapse free, double heterostructure AlGaN/InGaN/GaN field effect transistors (DH... more Novel, current collapse free, double heterostructure AlGaN/InGaN/GaN field effect transistors (DHFETs) are fabricated on the insulating SiC substrates. The simulations show that a combined effect of the bandgap offsets and polarization charges provides an excellent 2D carrier confinement. These devices demonstrate output RF powers as high as 4.3 W/mm in CW mode and 6.3 W/mm in the pulsed mode, with the gain compression as low as 4 dB.

Japanese Journal of Applied Physics, 2007

We present a novel metalorganic hydride vapor phase epitaxy (MOHVPE) approach for lateral epitaxy... more We present a novel metalorganic hydride vapor phase epitaxy (MOHVPE) approach for lateral epitaxy of high-quality crackfree AlN layers over sapphire with thicknesses in excess of 20 mm. Feasibility of depositing thick AlN buffer layers and device quality Al x Ga 1Àx N heterojunctions in a single chamber and growth run using metalorganic chemical vapor deposition and hydride vapor phase epitaxy growths either sequentially or simultaneously is demonstrated. Transmission electron microscopy, atomic force microscopy, and cathodoluminescence analyses confirm the viability of the MOHVPE grown layers for subsequent device fabrication.

Japanese Journal of Applied Physics, 2006

We report the first ever room temperature (RT) stimulated emission at 214 nm using high quality A... more We report the first ever room temperature (RT) stimulated emission at 214 nm using high quality AlN layers that were grown over patterned sapphire substrates by pulsed lateral epitaxial overgrowth (PLOG) process. The PLOG process yielded fully coalesced layers with total thicknesses in excess of 10 mm resulting in a reduction in the threading dislocation density by several orders. The stimulated emission was achieved at 214 nm under pulsed optical pumping at RT. The RT threshold optical power density was approximately 9 MW/cm 2 and the stimulated edge-emission signal was strongly polarized with E k c.

$Research paper thumbnail of High-Temperature Performance of AlGaN/GaN MOSHEMT With <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><msub><mrow><mtext>SiO</mtext></mrow><mn>2</mn></msub></mrow><annotation encoding="application/x-tex">\hbox{SiO}_{2}</annotation></semantics></math>SiO2 Gate Insulator Fabricated on Si (111) Substrate$

IEEE Transactions on Electron Devices, 2012

ABSTRACT The dc operation of high-quality AlGaN/GaN metal-oxide-semiconductor high-electron-mobil... more ABSTRACT The dc operation of high-quality AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors (MOSHEMTs) on Si (111) substrates, fabricated using SiO2 as the gate insulator, is investigated for the first time as a function of ambient temperature (T). I-V and C-V characteristics of these depletion-mode devices are studied in the temperature range of 25-200 degrees C, and the results are compared to those of reference AlGaN/GaN HEMTs processed on the same wafer and of identical geometry. For devices with an 8-mu m drain-to-source separation and 1 x 2.5 x 100 mu m(2) gate dimensions, the maximum output current density was about 730 mA/mm at + 2 V gate bias for both types of transistors. The thermal behavior of the MOSHEMTs on Si was found to resemble that of devices grown on sapphire and silicon carbide with the gate leakage current exhibiting a rapid increase with T but remaining below the levels seen in the reference HEMTs. The maximum drain current also showed a relatively smaller degradation at elevated temperatures as compared to previously published data.

Applied Physics Letters, 1998

We investigated two-dimensional electron transport in doped AlGaN-GaN heterostructures ͑with the ... more We investigated two-dimensional electron transport in doped AlGaN-GaN heterostructures ͑with the electron sheet concentration n s Ϸ10 13 cm Ϫ2 ͒ grown on conducting 6H-SiC substrates in the temperature range Tϭ0.3-300 K. The electron mobility in AlGaN-GaN heterostructures grown on SiC was higher than in those on sapphire substrates, especially at cryogenic temperatures. The highest measured Hall mobility at room temperature was H ϭ2019 cm 2 /V s. At low temperatures, the electron mobility increased approximately five times and saturated below 10 K at H ϭ10250 cm 2 /V s. The experimental results are compared with the electron mobility calculations accounting for various electron scattering mechanisms.

Applied Physics Letters, 2002

Applied Physics Letters, 2001

We report on Pd/Ag/Au/Ti/Au alloyed metallic contact to p GaN. An 800°C anneal for 1 min in flowi... more We report on Pd/Ag/Au/Ti/Au alloyed metallic contact to p GaN. An 800°C anneal for 1 min in flowing nitrogen ambient produces an excellent ohmic contact with a specific contact resistivity close to 1ϫ10 Ϫ6 ⍀ cm 2 and with good stability under high current operation conditions. This high-temperature anneal forms an alloy between Ag, Au, and p GaN resulting in a highly p-doped region at the interface. Using x-ray photoelectron spectroscopy and x-ray diffraction analysis, we confirm that the contact formation mechanism is the metal intermixing and alloying with the semiconductor.

Applied Physics Express, 2011

Lateral-conduction, substrate-free flip-chip (SFFC) light-emitting diodes (LEDs) with peak emissi... more Lateral-conduction, substrate-free flip-chip (SFFC) light-emitting diodes (LEDs) with peak emission at 276 nm are demonstrated for the first time. The AlGaN multiple quantum well LED structures were grown by metal-organic chemical vapor deposition (MOCVD) on thick-AlN laterally overgrown on sapphire substrates. To fabricate the SFFC LEDs, a newly-developed laser-assisted ablation process was employed to separate the substrate from the LED chips. The chips had physical dimensions of 1100 Â 900 m 2 , and were comprised of four devices each with a 100 Â 100 m 2 junction area. Electrical and optical characterization of the devices revealed no noticeable degradation to their performance due to the laser-lift-off process.

Applied Physics Express, 2009

Nitek, Inc., 1804 Salem Church Road, Irmo, SC 29063, USA 1Department of Electrical Engineering, U... more Nitek, Inc., 1804 Salem Church Road, Irmo, SC 29063, USA 1Department of Electrical Engineering, University of South Carolina, Columbia, SC 29208, USA Received June 27, 2009; accepted July 30, 2009; published online September 4, 2009