Autoignition and combustion characteristics of heptane droplets with the addition of aluminium nanoparticles at elevated temperatures

Javed, Irfan,Baek, Seung Wook,Waheed, Khalid Elsevier 2015 Combustion and Flame Vol.162 No.1

<P><B>Abstract</B></P> <P>We investigate the effects of high ambient temperatures and various concentrations of nanoparticles (NPs) on the autoignition and combustion characteristics of heptane-based nanofluid droplets. A single, heptane (<I>n</I>-C<SUB>7</SUB>H<SUB>16</SUB>) droplet containing 0.5%, 2.5%, or 5.0% by mass of aluminium (Al) NPs mounted on a silicon carbide fibre was exposed to a rapid increase in temperature (from room temperature to temperatures in the range 600–850°C) at atmospheric pressure and under normal gravity, and the autoignition and combustion characteristics were observed. The ignition delay, burn rate, and combustion characteristics of pure and stabilised heptane droplets were also examined for comparison. The results show that, as with the pure heptane droplets, the ignition delay of the NP-laden heptane droplets (<I>n</I>-Al/heptane) followed an Arrhenius temperature dependence. The reduction in the ignition delay time with increasing temperature depended on the loading of NPs in the droplet. The overall activation energy obtained for dilute NP concentrations (0.5% by mass) was smaller, and that for dense (2.5% and 5.0%) concentrations of NPs was larger, than that of the pure heptane droplets. Consequently, the addition of 0.5% Al NPs to heptane resulted in ignition at 600°C, which is not observed with stabilised heptane or 2.5% and 5.0% <I>n</I>-Al/heptane droplets. At higher temperatures, the ignition delay of the <I>n</I>-Al/heptane droplets was comparable to that of pure heptane droplets. The combustion of the <I>n</I>-Al/heptane droplets did not follow the classical <I>d</I> <SUP>2</SUP>-law, in contrast to the combustion of the pure and stabilised heptane droplets. Regardless of the NP concentration, the <I>n</I>-Al/heptane droplets exhibited disruptive burning behaviour, which was characterised by multiple expansions and ruptures or ‘microexplosions’. During these microexplosions, the NPs were ejected from the droplets, and the intensity of the microexplosions increased with increasing temperature; consequently, the burning time and total combustion time of the droplet was reduced. Due to these intense and frequent microexplosions, almost no residue from the Al NPs remained on the fibre following combustion, and a separate Al flame was not observed. The average gasification (burn) rate of the <I>n</I>-Al/heptane droplets remained equal to that of pure heptane droplets at relatively low temperatures (600–700°C); however, at higher temperatures (750–850°C), it was significantly faster than that of the pure heptane droplets.</P>

High performance corrosion resistant polyaniline/alkyd ecofriendly coatings

Javed Alam,Ufana Riaz,Sharif Ahmad 한국물리학회 2009 Current Applied Physics Vol.9 No.1

The growing environmental concerns have led to the formulation of new coating strategies by employing inherently conductive polymers (ICPs) as a key component in order to eliminate the toxic heavy metals from protective coatings. Also, the renewable resources are given increasing priority within chemical industry and the energy community. Emphasis is therefore, being laid on the production and processing of polymers from renewable resources which show advantages when compared with petrochemical raw materials and are regarded as an ideal raw material. The present work reports the investigations on the corrosion-resistance performance of soya oil alkyd, containing nano polyaniline (PANI) against mild steel (MS). The corrosion-protective performance was evaluated in terms of physicomechanical properties, corrosion rate, open circuit potential measurements (OCP) and scanning electron microscopy (SEM) studies. The performance was compared to the reported PANI coatings. The growing environmental concerns have led to the formulation of new coating strategies by employing inherently conductive polymers (ICPs) as a key component in order to eliminate the toxic heavy metals from protective coatings. Also, the renewable resources are given increasing priority within chemical industry and the energy community. Emphasis is therefore, being laid on the production and processing of polymers from renewable resources which show advantages when compared with petrochemical raw materials and are regarded as an ideal raw material. The present work reports the investigations on the corrosion-resistance performance of soya oil alkyd, containing nano polyaniline (PANI) against mild steel (MS). The corrosion-protective performance was evaluated in terms of physicomechanical properties, corrosion rate, open circuit potential measurements (OCP) and scanning electron microscopy (SEM) studies. The performance was compared to the reported PANI coatings.

Lightpaths Routing for Single Link Failure Survivability in IP-over-WDM Networks

Javed, Muhammad,Thulasiraman, Krishnaiyan,Xue, Guoliang(Larry) The Korea Institute of Information and Commucation 2007 Journal of communications and networks Vol.9 No.4

High speed all optical network is a viable option to satisfy the exponential growth of internet usage in the recent years. Optical networks offer very high bit rates and, by employing technologies like internet protocol over wavelength division multiplexing(IP-over-WDM), these high bit rates can be effectively utilized. However, failure of a network component, carrying such high speed data traffic can result in enormous loss of data in a few seconds and persistence of a failure can severely degrade the performance of the entire network. Designing IP-over-WDM networks, which can withstand failures, has been subject of considerable interest in the research community recently. Most of the research is focused on the failure of optical links in the network. This paper addresses the problem of designing IP-over-WDM networks that do not suffer service degradation in case of a single link failure. The paper proposes an approach based on the framework provided by a recent paper by M. Kurant and P. Thiran. The proposed approach can be used to design large survivable IP-over-WDM networks.

Effects of Foil Thickness to Grain Size (t/d) Ratio and Prestraining on Tensile Response, Microformability and Crystallographic Texture of Ultra-Low Carbon Steel Thin Foils

Javed S. Ibrahim,M. J. N. V. Prasad,Partha Sarkar,K. Narasimhan 대한금속·재료학회 2024 METALS AND MATERIALS International Vol.30 No.2

Ultra-low carbon (ULC) steels, containing a carbon content ~ 0.055 wt%, have been used in several applications in the formof thin foils. However, there are limited studies on the effects of foil thickness (t) to grain size (d) ratio and foil condition onthe tensile response and formability of thin ULC steel foils. In the present work, the tensile and forming behaviours of ULCsteel foils of thickness about 400 μm were evaluated in both annealed and prestrained (by cold reduction to 2–7%) conditionsas a function of t/d ratio and followed by detailed texture evolution analysis. Vacuum annealing was used to achievevarying t/d ratios in the specimens. Additionally, thin ULC steel foils of 100 μm thickness in annealed condition were alsoused for examining the thickness effect. Microstructural analysis was performed using the electron backscattered diffractiontechnique. Microformability was assessed by a miniaturised Nakazima test setup with specimen geometries designed toproduce three different strain paths. The annealed foils displayed a typical yield-point phenomenon, but the total yield-pointelongation decreased with decreasing thickness and grain size. The foils exhibited typical Hall–Petch strengthening, coldwork hardening, and forming limit curves; however, there were substantial reductions in both tensile strength and ductility,and consequently, the forming strains, with decreasing the t/d ratio. The tensile response and formability of the foils wereadversely affected by both thinning and prestraining. The texture studies revealed the formation of a γ-fibre i.e., < 111 >||normaldirection, and its intensity varied significantly with the t/d ratio and mode of strain path.

Autoignition and combustion characteristics of kerosene droplets with dilute concentrations of aluminum nanoparticles at elevated temperatures

Javed, Irfan,Baek, Seung Wook,Waheed, Khalid Elsevier 2015 Combustion and Flame Vol.162 No.3

<P><B>Abstract</B></P> <P>In this experimental study, we investigated the effects of high ambient temperatures and dilute concentrations of nanoparticles (NPs) on the autoignition and combustion characteristics of kerosene-based nanofluid droplets. An isolated kerosene droplet containing 0.1%, 0.5% or 1.0% by weight of aluminum (Al) NPs suspended on a silicon carbide (SiC) fiber was suddenly exposed to an elevated temperature (in range 400–800°C) at atmospheric pressure (0.1MPa) under normal gravity, and the autoignition and combustion characteristics were examined. The ignition delay time, burning rate constant and combustion characteristics of pure and stabilized kerosene droplets were also observed for comparison. The results indicate that, similar to pure kerosene droplets, the ignition delay time of NP-laden kerosene (<I>n</I>-Al/kerosene) droplets also followed the Arrhenius expression and decreased exponentially with increasing temperature. However, the addition of dilute concentrations of Al NPs to kerosene reduced the ignition delay and lowered the minimum ignition temperature to 600°C, at which pure kerosene droplets of the same initial diameter were not ignited. In contrast to the combustion of pure and stabilized kerosene droplets, the combustion of <I>n</I>-Al/kerosene droplets exhibited disruptive behavior characterized by sudden reductions in the droplet diameter without any prior expansions caused by multiple-time bubble formation and their subsequent rupture at or near the droplet’s surface. This bubble pop-up resulted in droplet trembling and fragmentation and ultimately led to enhancement in gasification, vapor accumulation and envelope flame disturbance. The NPs were also brought out of the droplets through these disruptions. Consequently, the burning time and total combustion time of the droplets were reduced, and almost no residue remained on the fiber following combustion. Thus, the combustion rate of <I>n</I>-Al/kerosene droplets was substantially enhanced compared with pure kerosene droplets at all tested temperatures.</P>

Associations between the Plasticity Region Genes of Helicobacter pylori and Gastroduodenal Diseases in a High-Prevalence Area

Javed Yakoob,Zaigham Abbas,Muhammad Islam,Shahab Abid,Wasim Jafri 거트앤리버 소화기연관학회협의회 2010 Gut and Liver Vol.4 No.3

Background/Aims: Genes associated with the Helicobacter pylori (H. pylori) plasticity region may play a role in the pathogenesis of H. pylori. We compared the genes jhp0940, jhp0947, and jhp0986 in H. pylori isolates from patients with different gastroduodenal diseases and in different age groups. Methods: The H. pylori hyperplasticity region genes jhp0940, jhp0947,and jhp0986 were studied by PCR. We also evaluated whether these genes were related to the cytotoxin-associated gene (cagA) and histology findings. Results: Of the patient cohort, 71 (62%) were positive for jhp0940, 67 (59%) for jhp0947, 12 (10%) for jhp0986, and 69 (60%) for cagA. jhp0940 (n=18,67%) and jhp0947 (n=23, 85%) were found more frequently in duodenal ulcer (DU) patients than in gastritis patients (n=14, 39%; p=0.029 and p<0.001, respectively). Gastric ulcer (GU) was more frequently associated with jhp0940 (17 patients, 77%; p=0.003)than with gastritis (14 patients, 39%). Gastric carcinoma (GC) was more strongly associated with both jhp0940 (22 patients, 76%; p=0.003) and jhp0947 (22patients, 76%; p=0.003) than was gastritis (14 patients,39%). jhp0947 was more frequently associated with chronic active inflammation (58 patients, 87%;p=0.009) than with chronic inflammation (9 patients,13%). Multivariate analysis demonstrated that jhp0947was associated with DU (odds ratio, 6.1; 95% confidence interval, 1.87-20). Conclusions: The genes jhp0947 and jhp0940 were identified in H. pylori isolates from patients with GC and DU, while jhp0940was also isolated from patients with GU. jhp0947 was independently associated with DU.

Spatiotemporal Low-Rank Modeling for Complex Scene Background Initialization

Javed, Sajid,Mahmood, Arif,Bouwmans, Thierry,Jung, Soon Ki IEEE 2018 IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDE Vol.28 No.6

<P>Background modeling constitutes the building block of many computer-vision tasks. Traditional schemes model the background as a low rank matrix with corrupted entries. These schemes operate in batch mode and do not scale well with the data size. Moreover, without enforcing spatiotemporal information in the low-rank component, and because of occlusions by foreground objects and redundancy in video data, the design of a background initialization method robust against outliers is very challenging. To overcome these limitations, this paper presents a spatiotemporal low-rank modeling method on dynamic video clips for estimating the robust background model. The proposed method encodes spatiotemporal constraints by regularizing spectral graphs. Initially, a motion-compensated binary matrix is generated using optical flow information to remove redundant data and to create a set of dynamic frames from the input video sequence. Then two graphs are constructed, one between frames for temporal consistency and the other between features for spatial consistency, to encode the local structure for continuously promoting the intrinsic behavior of the low-rank model against outliers. These two terms are then incorporated in the iterative <I>Matrix Completion</I> framework for improved segmentation of background. Rigorous evaluation on severely occluded and dynamic background sequences demonstrates the superior performance of the proposed method over state-of-the-art approaches.</P>

Background–Foreground Modeling Based on Spatiotemporal Sparse Subspace Clustering

Javed, Sajid,Mahmood, Arif,Bouwmans, Thierry,Soon Ki Jung IEEE 2017 IEEE TRANSACTIONS ON IMAGE PROCESSING - Vol.26 No.12

<P>Background estimation and foreground segmentation are important steps in many high-level vision tasks. Many existing methods estimate background as a low-rank component and foreground as a sparse matrix without incorporating the structural information. Therefore, these algorithms exhibit degraded performance in the presence of dynamic backgrounds, photometric variations, jitter, shadows, and large occlusions. We observe that these backgrounds often span multiple manifolds. Therefore, constraints that ensure continuity on those manifolds will result in better background estimation. Hence, we propose to incorporate the spatial and temporal sparse subspace clustering into the robust principal component analysis (RPCA) framework. To that end, we compute a spatial and temporal graph for a given sequence using motion-aware correlation coefficient. The information captured by both graphs is utilized by estimating the proximity matrices using both the normalized Euclidean and geodesic distances. The low-rank component must be able to efficiently partition the spatiotemporal graphs using these Laplacian matrices. Embedded with the RPCA objective function, these Laplacian matrices constrain the background model to be spatially and temporally consistent, both on linear and nonlinear manifolds. The solution of the proposed objective function is computed by using the linearized alternating direction method with adaptive penalty optimization scheme. Experiments are performed on challenging sequences from five publicly available datasets and are compared with the 23 existing state-of-the-art methods. The results demonstrate excellent performance of the proposed algorithm for both the background estimation and foreground segmentation.</P>

Anaerobic biodegradation of Benzene, Toluene, Ethylbenzene and Xylene (BTEX) and changes in microbial community by TRFLP analysis

Javed H. Niazi,Sun-Mi Lee,Byoung-In Sang 한국생물공학회 2007 한국생물공학회 학술대회 Vol.2007 No.4

Processing and Specimen Thickness to Grain Size (t/d) Ratio Effects on Tensile Behaviour and Microformability of Copper Foils

Javed S. Ibrahim ,Rohit T. Mathew,M. J. N. V. Prasad,K. Narasimhan 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.10

Owing to high heat flux ability and good mechanical strength, copper has been used for micro-electro-mechanical systems(MEMS) components with dimensions in micrometers processed by electrochemical methods. In the present study, finegrained copper foils of different thicknesses and grain sizes produced by pulsed electrodeposition under different controlledcurrent densities were used to investigate the effect of total number of grains across thickness of foil on its tensile responseand formability. For a comparative study, commercially available rolled Cu foils were also used. Vacuum annealing wasemployed to obtain a wide range of fully recrystallized grain sizes within same thickness of the foils. Detailed microstructuralcharacterization was carried out using scanning electron microscope attached with electron backscattered diffraction detector. The foils were subjected to uniaxial tensile testing and formability testing using a miniaturized Nakazima test setup. Asanticipated, finer the grain size higher was the yield strength. However, the strength of copper reduced with decreasing thetotal number of grains across thickness of the foil. The electrodeposited Cu foil exhibited relatively higher strength levelsbut reduced tensile ductility along with decreased strain hardening ability compared to the fully recrystallized Cu foils havingsimilar grain sizes. Furthermore, the number of grains across thickness and the prior history of foils played significantrole on the shape and trend in variation of the forming limit curve of Cu. An α-fiber (< 110 >) texture evolved in Cu duringdeformation and its volume fraction strengthened under biaxial deformation conditions.