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

Papers by Sohaib Khan

Proceedings of the National Academy of Sciences, 2013

Lubricants

This research focuses on the study of the simulation capabilities of the lagrangian (LAG) model a... more This research focuses on the study of the simulation capabilities of the lagrangian (LAG) model and Smoothed Particle Hydrodynamics (SPH) model for the orthogonal dry machining of aluminum alloy Al6061-T6. A three-dimensional finite element model was developed and verified using experimental data from the published literature. The numerical models were developed using lagrangian boundary conditions via finite element modeling in ABAQUS/Explicit 6.14. The cutting simulations were carried out at low and medium cutting speeds. Johnson–Cook material constitutive law and Johnson–Cook damage law were used in both models. The numerical methodologies are compared based on cutting forces, chip morphology, shear angle, chip separation criterion, and chip thickness. The findings of the present work show that the LAG model is good for predictions regarding cutting forces and chip morphology, while the SPH model is good for predictions regarding the shear angle and chip thickness. The difference...

Crystals

In this paper, the cladding of pure aluminum and a low-carbon steel alloy was performed through f... more In this paper, the cladding of pure aluminum and a low-carbon steel alloy was performed through friction stir processing with minimal intermetallic compound formation. A 3 mm thick aluminum plate was clamped on top of a steel plate. A thick, pure copper plate was used as a backing plate. The tool pin length was adjusted to be the same as the upper plate’s thickness (3 mm) and longer than 3.2 mm. The effect of the tool pin length and the rotation speed (500–1500 rpm) on the cladding’s quality, microstructure, and the mechanical properties of the steel/aluminum interface were investigated using optical and scanning electron microscopy, a hardness test, and a peel test. The results showed that the bonding of pure aluminum and a low-carbon steel alloy can be successfully performed at a more than 500 rpm rotation speed. At a tool pin length of 3 mm and a rotation speed of 1000 rpm, sound and free-intermetallic compound–cladding interfaces were formed, while some Fel2Al5 intermetallics we...

Frontiers in Bioengineering and Biotechnology

Nanotechnology is considered one of the most significant advancements in science and technology o... more Nanotechnology is considered one of the most significant advancements in science and technology over the last few decades. However, the contemporary use of nanomaterials in bioenergy production is very deficient. This study evaluates the application of nanomaterials for biogas production from different kinds of waste. A state-of-the-art comprehensive review is carried out to elaborate on the deployment of different categories of nano-additives (metal oxides, zero-valent metals, various compounds, carbon-based nanomaterials, nano-composites, and nano-ash) in several kinds of biodegradable waste, including cattle manure, wastewater sludge, municipal solid waste, lake sediments, and sanitary landfills. This study discusses the pros and cons of nano-additives on biogas production from the anaerobic digestion process. Several all-inclusive tables are presented to appraise the literature on different nanomaterials used for biogas production from biomass. Future perspectives to increase bi...

Materials

Friction Stir Processing (FSP) was used to fabricate metal matrix composite, based on steel and r... more Friction Stir Processing (FSP) was used to fabricate metal matrix composite, based on steel and reinforced with nano-sized yttrium oxide powder. The powder was packed in a narrow longitudinal groove of 2 mm depth and 1 mm width cut in the steel plate’s rear surface. Different rotation speeds of 500–1500 rpm were used, at a fixed traveling speed of 50 mm·min−1. Single-pass and two passes, with the same conditions, were applied. The direction of the second pass was opposite to that of the first pass. After the first pass, complete nugget zones were obtained when the rotation speeds were more than 700 rpm with some particles agglomeration. The added particles showed as narrow elliptical bands, with a band pitch equal to the rotation speed over traveling speed. Performing the second FSP pass in the opposite direction resulted in better particles distributions. Almost defect-free composite materials, with homogenously distributed yttria nano-sized particles, were obtained after two passe...

Acta Odontologica Scandinavica

Abstract Objective To investigate whether self-reported smoking and serum cotinine levels associa... more Abstract Objective To investigate whether self-reported smoking and serum cotinine levels associate with periodontal pocket development and to determine the accuracy of self-reported smoking using serum cotinine. Materials and methods This 4-year prospective cohort study included data from 294 dentate adults, aged ≥30 years, who participated in both the Health 2000 Survey and the Follow-up Study of Finnish Adults’ Oral Health. Subjectively reported smoking status (daily smokers n = 62, occasional smokers n = 12, quitters n = 49, and never-smokers n = 171), serum cotinine levels, demographic factors, education level, dental behaviours and medical history were collected at baseline. The outcome measure was the number of teeth with periodontal pocketing ≥4 mm over 4 years. Results Self-reported daily smokers had 1.82 (95% CI: 1.32–2.50) higher incidence of deepened periodontal pockets than never-smokers. A positive association was observed between serum cotinine (≥42.0 μg/L) and the development of periodontal pockets. The misclassification rate of self-reported smoking was 6%. Conclusions Both self-reported daily smoking and higher serum cotinine were associated with periodontal pocket development. Self-reported smoking was fairly accurate in this study. However, higher cotinine levels among a few self-reported never-smokers indicated misreporting or passive smoking. Thus, self-reports alone are not enough to assess the smoking-attributable disease burden.

Cureus, 2022

Parastomal hernia (PH) is an abnormal herniation of tissue or intra-abdominal organ through the f... more Parastomal hernia (PH) is an abnormal herniation of tissue or intra-abdominal organ through the fascial defect created at the ostomy site. It is a common complication of stoma creation and usually contains bowel, intra-abdominal fat, or omentum. Herniation of a fixed organ like the stomach is very rare and can lead to significant morbidity and mortality. Here, we present a case of an 83-year-old female with a history of sigmoidectomy and subsequent development of parastomal hernia who presented with abdominal pain, nausea, and vomiting and was found to have stomach herniation into the parastomal hernia sac. She was managed conservatively with intravenous (IV) fluids, electrolyte replacement, and decompression with a nasogastric (NG) tube. In this article, we have discussed the incidence, clinical presentation, diagnosis, and management of gastric involvement in the parastomal hernia that can help clinicians identify and treat it early at the time of presentation.

Existing approaches to nonrigid structure from motion assume that the instantaneous 3D shape of a... more Existing approaches to nonrigid structure from motion assume that the instantaneous 3D shape of a deforming object is a linear combination of basis shapes, which have to be estimated anew for each video sequence. In contrast, we propose that the evolving 3D structure be described by a linear combination of basis trajectories. The principal advantage of this approach is that we do not need to estimate any basis vectors during computation. We show that generic bases over trajectories, such as the Discrete Cosine Transform (DCT) basis, can be used to compactly describe most real motions. This results in a significant reduction in unknowns, and corresponding stability in estimation. We report empirical performance, quantitatively using motion capture data, and qualitatively on several video sequences exhibiting nonrigid motions including piece-wise rigid motion, partially nonrigid motion (such as a facial expression), and highly nonrigid motion (such as a person dancing).

Figure S1. P. yezoensis healthy cells (A) and infected (B) with P. porphyrae image under a light ... more Figure S1. P. yezoensis healthy cells (A) and infected (B) with P. porphyrae image under a light microscope using 100X lens; the red arrow represents the pathogenic oomyceteous hyphae that elongates from one cell to another. Figure S2. Whole cell proteins electrophoresis of Pyropia yezoensis samples. The SDS-PAGE indicating the different samples with different band size, i.e. C1-C3 representing the control samples while T1-T3 showing the treated samples with oomycetes spores. Figure S3. Hierarchical clustering of differentially expressed proteins under infection stress; proteins related to defense response and signal transduction. I-1 to I-3 and H-1 to H-3 the three biological replicates for infected and healthy samples, respectively. Figure S4. Hierarchical clustering of differentially expressed proteins under infection stress; proteins related to energy metabolism and photosynthesis. I-1 to I-3 and H-1 to H-3 the three biological replicates for infected and healthy samples, respec...

Australian Journal of Mechanical Engineering, 2021

Heat exchangers have found extensive applications in the engineering sector owing to the crucial ... more Heat exchangers have found extensive applications in the engineering sector owing to the crucial need for heat transfer and temperature regulation in the process industry. The performance analysis of a heat exchanger can either be investigated experimentally or utilizing computational fluid dynamics (CFD). The simulation of flow conditions based on CFD principles is considered as a contemporary approach for conducting performance analysis and design optimization of the heat exchanger. The paper aims to present how the performance optimization parameters of shell and tube heat exchanger effect its performance in terms of the extent of heat transfer achieved and fall in the shell outlet temperature. A standard model (Model 1) was initially defined, and seven subsequent models were created with one varying parameter as compared to Model 1 to carry out the comparative analysis. The results showed that decrease in inlet velocity, increase in thermal conductivity of the heat exchanger material, reduction in baffle spacing and use of triangular tube bundle arrangement has significant influence on the reduction of the condensate temperature. The effects of the same parameters on the temperature distribution and heat transfer rate have also been discussed

2019 16th International Bhurban Conference on Applied Sciences and Technology (IBCAST), 2019

Image processing techniques can be utilized in analyzing amplitude and frequency of vibrating str... more Image processing techniques can be utilized in analyzing amplitude and frequency of vibrating structures. It is a form of non-contact method which is suitable for cases where application of contact devices could alter the frequency of structure. This paper covers the study based on vision system that performs amplitude and frequency measurement of a cantilever beam in near real time, using image processing and computer vision toolbox in MATLAB. The vision system then detects changes in amplitude followed by feedback mechanism to ensure operation at resonance frequency. The system includes a high speed camera which is able to detect amplitude and frequency of cantilever beam vibrating at a frequency with the help of mechanical exciter. The high speed camera captures images of the beam, that are processed by a MATLAB script for evaluation of amplitude and frequency. To locate amplitude of the vibrating beam, centroid recognition technique is used which tracks the centroids of the beam in consecutive frames and plots number of pixels moved by the centroid with respect to time. Later, frequency is found out on the basis of intensity change over the time. Amplitude analysis is done at different frequencies which are automatically adjusted with the help of microcontroller to determine the resonance point. Exciter continues to vibrate at the resonant frequency until a change in amplitude is detected, implying the formation of crack. At which point the system adjusts its vibrating frequency accordingly to adjust with the new resonant frequency. This paper covers proper experimental procedure backed with the results.

Applied Sciences, 2020

Fiber-reinforced polymer (FRP) composite bridges are usually constructed for rapid installation. ... more Fiber-reinforced polymer (FRP) composite bridges are usually constructed for rapid installation. The durability of the bridge is increased by stiffness, strength to weight ratio, and corrosion resistance. The main factors on which the design of the composite sandwiched bridge considerably depends are ply layers, material system, alignment of ply angles, and thickness of the core. In this work, a parametric design study for a bridge using finite element analysis (FEA) is presented. Two types of composite materials—carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP)—were used as the sandwich structure’s skin, and three different types of woods were used as a core. Different design configurations were acquired based on material and instability constraints by using Euro-codes. Failure criterion of Tsai-Hill, Tsai-Wu, MS, equivalent stress, and maximum shear stress were implemented to analyze the overall failure of the bridge deck under Ultimate Limit State (...

Proceedings of the 2001 IEEE Computer Society Conference on Computer Vision and Pattern Recognition. CVPR 2001

Video segmentation is different from segmentation of a single image. While several correct soluti... more Video segmentation is different from segmentation of a single image. While several correct solutions may exist for segmenting a single image, there needs to be a consistency among segmentations of each frame for video segmentation. Previous approaches of video segmentation concentrate on motion, or combine motion and color information in a batch fashion. We propose a maximum a posteriori probability (MAP) framework that uses multiple cues, like spatial location, color and motion, for segmentation. We assign weights to color and motion terms, which are adjusted at every pixel, based on a confidence measure of each feature. We also discuss the appropriate modeling of pdfs of each feature of a region. The correct modeling of the spatial pdf imposes temporal consistency among segments in consecutive frames. This approach unifies the strengths of both color segmentation and motion segmentation in one framework, and shows good results on videos that are not suited for either of these approaches.

From the library stairwell take a LEFT and walk straight ahead. If using the library elevator, ta... more From the library stairwell take a LEFT and walk straight ahead. If using the library elevator, take a left upon exiting, then another left and proceed to the glass doors. The Winkler Center will be open between 8 AM and 5 PM on both November 3rd and 4th.

In modern wireless communication systems, the number of wireless users is steadily increasing, re... more In modern wireless communication systems, the number of wireless users is steadily increasing, resulting in a necessary demand for more available radio spectrum. Cognitive Radio (CR) is an innovative solution toward the efficient use of spectrum, by using the same spectrum from Secondary User (SU) simultaneously with Primary User (PU) or exploiting the spectrum holes. In all the cases, important consideration for performance enhancement of secondary user network, is to protect PU's QoS. In this regard all resource management problems and solutions pertaining to normal wireless communications becomes more complicated. In this book two of the important link layer issues, i.e. power control in underlay CR paradigm and cooperate sensing in interweave paradigm are addressed, while considering a regional approach, which generally increases performance than conventional methods, and reduces complexity (and hence cost) than recent techniques/ algorithms.

ArXiv, 2017

The scared cities of Makkah Al Mukarramah and Madina Al Munawarah host millions of pilgrims every... more The scared cities of Makkah Al Mukarramah and Madina Al Munawarah host millions of pilgrims every year. During Hajj, the movement of large number of people has a unique spatial and temporal constraints, which makes Hajj one of toughest challenges for crowd management. In this paper, we propose a computer vision based framework that automatically analyses video sequence and computes important measurements which include estimation of crowd density, identification of dominant patterns, detection and localization of congestion. In addition, we analyze helpful statistics of the crowd like speed, and direction, that could provide support to crowd management personnel. The framework presented in this paper indicate that new advances in computer vision and machine learning can be leveraged effectively for challenging and high density crowd management applications. However, significant customization of existing approaches is required to apply them to the challenging crowd management situatio...