Characteristic Changes in the Strengthening Western Disturbances over Karakoram in Recent Decades

Javed Aaquib,Kumar Pankaj 한국기상학회 2024 Asia-Pacific Journal of Atmospheric Sciences Vol.60 No.3

Western disturbances (WDs) are upper-tropospheric mid-latitude synoptic systems propagating eastward along the subtropical westerly jet stream. They are capable of causing extreme precipitation events and have strengthened their impact over the Karakoram part of the Himalayas in recent decades. They play a crucial role in the sustenance of the “Karakoram Anomaly,” which refers to the anomalous stability/surge of a few Karakoram glaciers in contrast to the other glaciers of the Himalayas. Using the existing WD-catalog derived from ERA5 and MERRA2 reanalysis datasets, we observed that the core genesis zone for Karakoram WDs had undergone a statistically significant shift of ~9.7oE, migrating towards more favourable conditions for cyclogenesis. The study proposes a new parameter to identify regions of potential extratropical cyclogenesis. The shift can be attributed to an enhanced genesis potential, convergence, and higher moisture availability along the WD path. Composite analysis suggests that moisture availability has risen significantly over the shifted zone. Moreover, the propagation speeds of these systems have significantly declined, which explains the recent intensification of precipitation events related to WDs over the Karakoram and hints toward a crucial synoptic influence on the anomalous regional mass-balance phenomenon.

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.

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>

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>

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.

Architecture of Task Manager for Real Time OS Explaining Real Time Operating Systems Issues

Javed Ahmad Shaheen MSCS 보안공학연구지원센터 2016 International Journal of Grid and Distributed Comp Vol.9 No.9

Complications of embedded applications are increasing. Within due time delivery to the market is also a pressure. So, the demand and use of real time operating systems is also increasing. However, it is an redundant fact that the Real Time Operating System (Real Time OS) can significantly degrade the performance. To face performance degradation, a Real-Time Task Manger (RTTM) has been presented in this paper. The Real-Time Task Manger is a hardware based extension to the processor that decreases performance bottleneck attributed to Real Time Operating System. Real-Time Task Manger decreases these performance bottlenecks introduced by Real Time Operating System by its hardware based architecture. The architecture of Real-Time Task Manger is being discussed in this paper provides an aid to deal with some common operations of Real Time Operating System that reason the performance degradation. For example event management, time management, and task scheduling. These operations have a property of some inborn parallelism. The Real-Time Task Manger uses this property to complete these operations in a constant time, and as a result, minimizes the overhead introduced by Real Time Operating System. The proposed architecture yields two benefits: It reduces the processor time taken by Real Time Operating System, and improves the response time to a considerable amount.

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>

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

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>