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RISS 인기검색어
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- 저자 : Ahmad Imtiaz (검색결과 19 건)
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Hierarchical structure parameters in three dimensional turbulence: She-Leveque model
Imtiaz Ahmad,Lamjed Hadj-Taieb,Muzamal Hussain,Mohamed A. Khadimallah,Muhammad Taj,Adil Alshoaibi 국제구조공학회 2022 Smart Structures and Systems, An International Jou Vol.29 No.5
Hierarchical structure parameters, proposed in She-Leveque model, are investigated for velocity components obtained from different flow types over a large range of Reynolds numbers 255 < < 720. The values of intermittency parameter , with respect to a fixed velocity component, are observed nearly same for all four types of turbulence. The parameter , for streamwise velocity components is nearly the same but significantly different for vertical components in different flows. It is also observed that for both parameters, an obvious relation between the longitudinal and transverse components < (and < ) always holds. However, the difference between and is found very small in all types of turbulent flows, we studied here. It is evidenced that at low Reynolds numbers, the deviations from K41 scaling are mainly due to the most intense structures and slightly because of more heterogeneous hierarchy of fluctuation structures. However, at higher Reynolds numbers the deviations seem as a consequence of the most intense structures only. Over all, the study suggests that the hierarchy parameter may be consider as a universal constant.
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Size-Separation and Self-Assembly of Anisotropic Nanoparticles in a Coffee-Stain Ring
Imtiaz Ahmad,Rahim Jan 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.15 No.01
Nanoparticles deposition via droplet drying technique generally leads to a coffee-stain-like ring. In the case of different shapes and sizes of nanoparticles, such ring-like deposits also demonstrate various phases within the self-assembly superstructures. For broad spectrum sizes in suspension, size-separation effect has not been considered before. Herein, polydisperse gold anisotropic nanoparticles have been prepared via wet chemical synthesis technique. High-resolution scanning electron microscopy (HRSEM) at various positions of a coffee-stain ring displayed both size-separation and self-assembly of nanoparticles. Especially at the outer edges of a ring-like deposit, side-by-side organized arrays of anisotropic nanoparticles have been observed. Likewise, such ordered arrays generally begin with thin nanorods and the width of nanoparticles increases as one moves inward within such arrays. Also, assembly of deposited arrays is more orderly arranged at the periphery of the ring, whereas such order significantly decreases at the interior region of the ring. Furthermore, it has been observed for a mixture of thick–thin nanorods and spheres that only thick nanorods self-assemble into ordered arrays whereas thin rod-sphere was found disordered everywhere within the ring. Nanoscale interactions are quantified for these systems to understand self-assembly behavior of such anisotropic nanoparticles.
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Waqas Ahmad,Imtiaz Ahmad,Muhammad Yaseen 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.9
Catalytic oxidative desulfurization of the model oil or synthetic sulfur oil (SSO) and the different real/ industrial industrial oil fractions was investigated using air assisted hydrogen peroxide and formic acid oxidation in the presence of Fe-ZSM-5 as catalyst. The reactivity of the different model sulfur compounds increased in the order of thiophene< dibenzothiophene (BT)<4-methyl dibenzothiophene (4-MDBT). The desulfurization yield in case of the model oil was increased in the presence of Fe-ZSM-5 and the sulfur content of the model oil was reduced from 1275 to less than 50 ppm in 60 min at 60 oC temperature. The catalyst also performed efficiently in ODS of real industrial oil fractions, i.e., untreated naphtha (UN), light gas oil (LGO), cooker derived combined heavy gas oil (HGO) and Athabasca oil sands derived bitumen (At. Bit.), and sulfur removal of 80, 78, 62 and 60% was attained, respectively. Kinetic investigation revealed that the ODS catalyzed by Fe-ZSM-5 followed the first-order kinetics.
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Khan, Aftab Ahmad,Khan, Imtiaz Afzal,Siyal, Muhammad Irfan,Lee, Chang-Kyu,Kim, Jong-Oh Elsevier 2019 Environmental research Vol.170 No.-
<P><B>Abstract</B></P> <P>The goal of this study was to prepare a robust anti-wetting and anti-fouling polyethersulfone (PES) membrane for the rejection of a highly saline (NaCl and CaCl<SUB>2</SUB>·2H<SUB>2</SUB>O) feed solution containing humic acid (HA) in direct contact membrane distillation (DCMD). Response surface methodology (RSM) was used to determine the optimum formulation of the used materials. The variable factors selected were polydimethyl siloxane (PDMS) and silica (SiO<SUB>2</SUB>); liquid entry pressure (LEP) and contact angle (CA) were selected as responses. Scanning electron microscopy (SEM) analysis confirmed the SiO<SUB>2</SUB> deposition and Fourier-transform infrared spectroscopy (FTIR) test evidenced the new functional groups i.e., Si–OH, siloxane, and C–F bond vibrations at 3446, 1099 cm<SUP>−1</SUP>, and 1150–1240 cm<SUP>−1</SUP> respectively on the membrane surface. The average roughness (Ra) was increased four times for the coated membranes (0.202–0.242 µm) as compared to that for pristine PES membrane (0.053 µm). The optimum PES-13 membrane exhibited consistent flux of 12 LMH and salt rejection (> 99%) with anti-fouling characteristic in DCMD using the feed solution of 3.5 wt% NaCl + 10 mM CaCl<SUB>2</SUB>·2H<SUB>2</SUB>O + 10 mg L<SUP>−1</SUP> HA. The PES-13 membrane may therefore be a key membrane for application in DCMD against CaCl<SUB>2</SUB>·2H<SUB>2</SUB>O-containing salty solutions with HA.</P> <P><B>Highlights</B></P> <P> <UL> <LI> PES membrane was prepared for application in DCMD using silica nanoparticles. </LI> <LI> Response surface methodology was employed to optimize the coating formulation. </LI> <LI> Modified membranes were resistant to fouling against calcium-humic acid feed. </LI> <LI> The high fluxes for PES-13 membrane were recorded with all three feed solutions. </LI> </UL> </P>
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Biochemical and Trace Mineral Analysis of Silajit Samples From Pakistan
Shafiq Muhammad Imtiaz,Nagra Saeed Ahmad,Batool Nayab The Korean Nutrition Society 2006 Nutritional Sciences Vol.9 No.3
Silajit is a blackish brown pitch-like gummy substance. It is an important Unani and Ayurvedic medicine widely used in the treatment of many diseases and as nutritional supplement It is found in certain mountainous regions of Pakistan, Afghanistan, India, Nepal, Australia and Russia. Silajit samples of Pakistani origin were obtained from different sources and analyzed for their physical characteristics and biochemical & elemental composition. X-ray diffraction studies on Silajit showed that it is an amorphous substance and has no crystalline structure. Also, pH studies of Silajit (2 g/L of water) indicated that it was slightly acidic in nature and ranged from 3.45 to 7.23. Conductivity ranged from 157.7 to 330. Amino acid analysis revealed that Silajit contained lysine and alanine in higher amounts than all other amino acids and ranged from 1456 to 2240 and 68 to $1615{\eta}mole/g$, respectively. Mean concentration of arsenic, mercury, cadmium, lead, copper and zinc was 73.15, 104.92, 0.496, 3.89, 4.04 and 17.23 ppm, respectively. Silajit samples were also analyzed for calcium, potassium and sodium.
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Client Communication: A Major Issue in Agile Development
Tarek El-Najar,Imtiaz Ahmad,Mohammad Alkandari 보안공학연구지원센터 2016 International Journal of Software Engineering and Vol.10 No.12
Agile development model solved a lot of its predecessor the waterfall model problems like time, cost, resources and high risk of failure due to incomplete or inaccurate requirements. However, agile model introduced the client communication problem; due to the structure and nature of agile methodologies, it depends heavily on communicating with client. With four layers of communication that get repeated in almost every agile iteration, failing to handle client communication is one of the main reasons behind failure of agile based projects. In this paper, we survey the existing methods of communication which are classified into two main categories: physical meetings/workshops and software communication tools. Each category is assessed and compared based on certain attributes such as availability, productivity, cost, reliability, trust and project coverage. In addition, the available solutions to address the communication problem, which include enhanced physical meetings/workshops and software tools like requirement engineering tools, agile management tools and social media sites and applications, are analyzed and assessed based on attributes such as usability, formality and project coverage. The study revealed that the available solutions did not address all the aspects of the communication problem. Therefore, it is desirable to develop an integrated solution which utilized communication software tool using social media frameworks as its backbone and physical meetings to benefit from human interaction and relationships to solve the communication problem in agile environment.
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Hemodynamic Flow in a Vertical Cylinder with Heat Transfer
Farhad Ali,Anees Imtiaz,Ilyas Khan,Nadeem Ahmad Sheikh,Dennis Ling Chuan Ching 한국자기학회 2018 Journal of Magnetics Vol.23 No.2
In blood, the concentration of red blood cells varies with the arterial diameter. In the case of narrow arteries, red blood cells concentrate around the centre of the artery and there exists a cell-free plasma layer near the arterial wall due to Fahraeus-Lindqvist effect. Due to non-uniformity of the fluid in the narrow arteries, it is preferable to consider the two-phase model of the blood flow. The present article analyzes the heat transfer effects on the two-phase model of the unsteady blood flow when it flows through the stenosed artery under an external pressure gradient. The direction of the artery is assumed to be vertical and the magnetic field is applied along the radial direction of the artery. Blood is considered as a non-Newtonian Casson fluid with uniformly distributed magnetic particles. Both the blood and magnetic particles are moving with distinct velocities. This two-phase problem is modelled using the Caputo-Fabrizio derivative approach and then solved for an exact solution using joint Laplace & Hankel transforms. Effects of pertinent parameters such as Grashoff number, Prandtl number, Casson fluid parameter and fractional parameters, and magnetic field on blood velocity and particle velocity have been shown graphically for both large and small values of time. Both velocity profiles increase with the increase of Grashoff number and Casson fluid parameter and reduce with the increase of magnetic field and Prandtl number. The behaviour of temperature is studied for different values of the fractional parameter.
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