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1

Numerical analysis of the compositional graded quaternary barrier AlGaN-based ultraviolet-C light-emitting diode

Malik S., Usman Muhammad, Hussain M., Munsif M., Khan S., Rasheed S., Ali S.

Opto-Electronics Review

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2021

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Vol. 29, No. 3

80--84

EN

The compositional graded quaternary barriers (GQBs) instead of ternary/conventional quantum barriers (QBs) have been used to numerically enhance the efficiency of AlGaN-based ultraviolet light-emitting diode (LED). The performance of LED with GQBs is examined through carrier concentrations, energy band diagrams, radiative recombination, electron and hole flux, internal quantum efficiency (IQE), and emission spectrum. As a function of the operating current density, a considerable reduction in efficiency droop is observed in the device with composition-graded quaternary barriers as compared to the conventional structure. The efficiency droop in case of a conventional LED is ~77% which decreased to ~33% in case of the proposed structure. Moreover, the concentration of electrons and holes across the active region in case of the proposed structure is increased to ~156% and ~44%, respectively.

2

Parametric study on cement treated aggregate panel under impact load

Ali S., Liu X., Thambiratnam D., Fawzia S., Gu Y., Wu J., Remennikov A.

Archives of Civil and Mechanical Engineering

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2018

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Vol. 18, no. 2

622--629

EN

The cement treated aggregate (CTA) is increasingly used as base or sub-base layer for pavement to withstand various traffic and dynamic loads. Under extreme events, the CTA layer of the pavement is expected to absorb significant amount of impact energies subjected to different loading conditions including accidents, mobile vehicles, heavy aircrafts, machinery, or even terrorist attack. However, no research has been found on the resistance of CTA under drop weight impact load. To fill up this gap, a detailed study was carried out to investigate the impact resistance of CTA under impact loading through both experimental and finite element analysis (FEA). Moreover, detailed parametric studies were carried out based on the validated model to determine the significance of selected key parameters on the impact resistance of CTA.

3

Effects of Triangular Core Rotation of a Hybrid Porous Core Terahertz Waveguide

Ali S., Ahmed N., Alwee S., Islam M., Rana S., Bhuiyan T.

International Journal of Electronics and Telecommunications

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2017

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Vol. 63, No. 1

25--31

EN

In this paper, we investigate the effects for rotating the triangular core air hole arrangements of a hybrid design porous core fiber. The triangular core has been rotated in anticlockwise direction to evaluate the impact on different waveguide properties. Effective Material Loss (EML), confinement loss, bending loss, dispersion characteristics and fraction of power flow are calculated to determine the impacts for rotating the triangular core. The porous fiber represented here has a hybrid design in the core area which includes circular rings with central triangular air hole arrangement. The cladding of the investigated fiber has a hexagonal array of air hole distribution. For optimum parameters the reported hybrid porous core fiber shows a flat EML of ±0.000416 cm⁻¹ from 1.5 to 5 terahertz (THz) range and a near zero dispersion of 0.4±0.042 ps/THz/cm from 1.25 to 5.0 THz. Negligible confinement and bending losses are reported for this new type of hybrid porous core design. With improved concept of air hole distribution and exceptional waveguide properties, the reported porous core fiber can be considered as a vital forwarding step in this field of research.

4

Leaching of manganese ores using corncob as reductant in H2SO4 solution

Ali S., Iqbal Y., Farooq U., Ahmad S.

Physicochemical Problems of Mineral Processing

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2016

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Vol. 52, iss. 1

56--65

EN

In this study, corncob was used as reductant for sulfuric acid leaching of manganese ore from Daweezi, Upper Mohmand Agency, Pakistan. X-ray diffraction of representative powdered samples revealed the presence of manganese silicate MnSiO(SiO4), calcite (CaCO3), and -quartz (SiO2). X-ray diffraction and energy dispersive spectroscopy analyses indicated that the examined manganese ore was siliceous in nature. Three process parameters were investigated in the present study including the particle size of the ore, leaching temperature, and amount of corncob. Manganese extraction of 92.48 wt% was achieved for a leaching time of 60 min at 90 oC using 1.9 mol/dm3 H2SO4 concentration and 4 g of corncob. The present results demonstrated that corncob is a low cost, renewable, and non-hazardous reducing agent for manganese leaching under mild acid conditions in comparison to the other available reagents.

5

Classification of EEG Signals Using Adaptive Time-Frequency Distributions

Khan N. A., Ali S.

Metrology and Measurement Systems

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2016

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Vol. 23, nr 2

251--260

EN

Time-Frequency (t-f) distributions are frequently employed for analysis of new-born EEG signals because of their non-stationary characteristics. Most of the existing time-frequency distributions fail to concentrate energy for a multicomponent signal having multiple directions of energy distribution in the t-f domain. In order to analyse such signals, we propose an Adaptive Directional Time-Frequency Distribution (ADTFD). The ADTFD outperforms other adaptive kernel and fixed kernel TFDs in terms of its ability to achieve high resolution for EEG seizure signals. It is also shown that the ADTFD can be used to define new time-frequency features that can lead to better classification of EEG signals, e.g. the use of the ADTFD leads to 97.5% total accuracy, which is by 2% more than the results achieved by the other methods.

6

Comparison study of the prosthetics interface pressure profile of air splint socket and ICRC polypropylene socket for upper limb prosthetics

Abd Razak N. A., Abu Osman N.A., Ali S., Gholizadeh H., Wan Abas W. A. B.

Biocybernetics and Biomedical Engineering

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2015

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Vol. 35, no. 2

100--105

EN

This study examined the interface pressure differences at the stump socket between an ICRC polypropylene socket and an air splint socket for a common wearer of transhumeral amputee using F-socket transducers. Two F-socket sensors arrays were attached to the residual limb. The subject was asked to complete the following tasks: Normal position, stand in a normal position without conducting any motion and shoulder movements, flexion/extension and abduction. The results revealed that the interface pressure applied using ICRC polypropylene socket was maximize at the end distal of the residual limb and give more pressure contact to any shoulder movements. Conversely, while using air splint socket, the socket was able to auto-adjust for required socket fitting even for any change while doing shoulder movements. Our result demonstrated how the comparison of pressure applied at the stump socket may lead in chosen the suitable prosthetic's socket for the amputee. The impending development of an auto-adjusted socket that uses an air splint system will provide the prosthetic socket with a less contact pressure at the residual limb.

7

Signatures of Late Neoproterozoic Gondwana assembly and Maronian glaciation in Lesser Himalaya: a palaeogeographical and stratigraphical approach

Umar M., Betts P., Khan M. M. S., Sabir M. A., Farooq M., Zeb A., Jadoon U. K., Ali S.

Acta Geologica Polonica

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2015

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Vol. 65, no. 1

1--19

EN

Stratigraphical and sedimentological analyses of Late Neoproterozoic successions in Lesser Himalaya are combined herein with palaeogeographical considerations and comparisons with equivalent successions in India and South China. The succession starts with the Hazara Formation, which contains complete and incomplete Bouma sequences suggesting its deposition in deep marine turbidite settings. The overlying Tanawal Formation, rich in massive sandstone, shale and siltstone, was deposited in shallow marine conditions, as indicated by the presence of parallel lamination, large scale tabular, trough cross- and hummocky cross-stratifications. The Tanawal Formation facies shift laterally from proximal (south-southeast) to distal (north-northwest). The glaciogenic Tanaki Boulder Bed, overlying the Tanawal Formation, was deposited during the Maronian glaciation. It is equivalent to the Blaini Formation of India, and to the Sinian diamictites of South China. The Abbottabad Formation of Cambrian age overlies the Tanaki Boulder Bed, and is composed of dolomite, chert nodules and phosphate-rich packages; similar successions are documented in India and South China at the same stratigraphical interval. The similarities of the Neoproterozoic successions of Lesser Himalaya (both in Pakistan and India) and South China suggests their possible proximity during the break-up of Rodinia and the assembly of the Gondwana Supercontinent.

8

Measuring Heavy Metals Content in Wastewater using Laser Induced Breakdown Spectroscopy

Ali S., Jamil H., Imran M.

International Letters of Chemistry, Physics and Astronomy

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2014

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Vol. 2

69-75

EN

In the present study, laser-induced breakdown spectroscopy (LIBS) has been applied for the determination of chromium and cadmium contents in wastewater of different canneries surrounding by leather factories. The plasma was generated with a Q-switched Nd:YAG laser having a fundamental wavelength of 1064 nm and delivers maximum pulse energy of 180 mJ. Experimental conditions were optimized to improve the sensitivity and to get a reasonable signal from the generated plasma. The results show that the concentration of chromium and cadmium are varying in different samples depending on the incoming flow of the wastewater from factories. The results from LIBS and standard analytical technique called flame atomic absorption spectroscopy (FAAS) were compared and found in good agreement within the experimental uncertainties.

9

Optimization Of Protocol For Biodiesel Production Of Linseed (Linum Usitatissimum L.) Oil

Ullah F., Bano A., Ali S.

Polish Journal of Chemical Technology

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2013

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Vol. 15, nr 1

74-77

EN

Attempts were made to optimize variables affecting the yield of linseed oil biodiesel in a base catalyzed transesterification reaction. The variables studied were reaction temperature (40-70oC), catalyst (NaOH) concentration (0.1-1.5%) and reaction time (30-180 min). The conversion of linseed oil into methyl esters was confirmed through analytical methods like 1H NMR, gas chromatography (GC) and refractometer. The maximum biodiesel yield (97š1.045% w/w) was obtained at 0.5% catalyst concentration, 65oC temperature, 180 min reaction time and 6:1 molar ratio of methanol to oil. 1H NMR confirmed the practically obtained % conversion of triglycerides into methyl esters which was further evidenced by refractometer analyses. The refractive index of biodiesel samples was lower than pure linseed oil. GC analysis confirmed the presence of linolenic acid (C18:3) as the dominant fatty acid (68 wt. %) followed by oleic acid (C18:1), linoleic acid (C18:2) and stearic acid (C18:0) respectively. The physical properties of linseed oil biodiesel like specific gravity (0.90 g/cm3) and flash point (177oC) were higher than American Society for Testing and Materials standards (ASTM 6751) for biodiesel. However, kinematic viscosity (3.752 mm2/s) was in the range of ASTM standards.

10

Identities with generalized derivations in semiprime rings

Dhara B., Ali S., Pattanayak A.

Demonstratio Mathematica

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2013

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Vol. 46, nr 3

453--460

EN

Let R be a semiprime ring. An additive mapping F:R  R is called a generalized derivation of R if there exists a derivation d : R  R such that F(xy) = F(x)y + xd(y) holds, for all x,y  R. The objective of the present paper is to study the following situations: (1) (...), for all x, y in some appropriate subset of R.

11

On left multipliers and the commutativity of prime rings

Ashraf M., Ali S.

Demonstratio Mathematica

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2008

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Vol. 41, nr 4

763-771

EN

Let R be an associative ring. An additive mapping H : R —> R is called a left multiplier if H(xy) = H(x)y, holds for all x, y e R. In this paper, we investigate commutativity of prime rings satisfying certain identities involving left multiplier. Some related results have also been discussed.

12

On horizontal and complete lifts of (1,1) tensor fields F satisfying the structure equation anFn+an-1Fn-1+an-2Fn-2+.......a2F2+a1F=0

Nivas R., Ali S., Srivastava S. K.

Demonstratio Mathematica

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2002

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Vol. 35, nr 1

155-163

EN

The horizontal and complete lifts from a differentiable manifold Mn of class C°° to its cotangent bundle T*(Mn) have been studied by Professors Yano and Patterson [5, 6]. Yano and Ishihara [7] studied lifts of f-structure in the tangent and cotangent bundles. F-structure manifolds of degree v > 3 have been studied by Kim [2]. Lifts of (1,1) tensor fields F satisfying Fv+2 - A2Fv-1 = 0 and Fv + (-l)v+1F = 0 have been studied by Srivastava [4]. The present paper deals with some problems on horizontal and complete lifts tensor fields satisfying polynomial equations of the type mentioned above. Integrability conditions are discussed, and prolongations in the third tangent space T3(Mn) are also considered.