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Nanoscale investigation of charge transport at the grain boundaries and wrinkles in graphene film
Ahmad, Muneer,An, Hyosub,Kim, Yong Seung,Lee, Jae Hong,Jung, Jongwan,Chun, Seung-Hyun,Seo, Yongho IOP Pub 2012 Nanotechnology Vol.23 No.28
<P>The influence of grain boundaries and mechanical deformations in graphene film on the electric charge transport is investigated at nanoscale with conductive atomic force microcopy. Large area monolayer graphene samples were prepared by the chemical vapor deposition technique. Field emission scanning electron microscopy confirmed the formation of grain boundaries and the presence of wrinkles. The presence of the D-band in the Raman spectrum also indicated the existence of sharp defects such as grain boundaries. Extremely low conductivity was found at the grain boundaries and the wrinkled surface was also more resistive in comparison to the plain graphene surface. Many samples were experimented with to justify our findings by selecting different areas on the graphene surface. Uniform conductivity was found on grain boundary and wrinkle free graphene surfaces. We made channels of varied lengths by local anodic oxidation to confine the charge carrier to the smallest dimensions to better confirm the alteration in current due to grain boundaries and wrinkles. The experimental findings are discussed with reference to the implementation of graphene as transparent conductive electrode. </P>
Omar Ashour,Ahmad Muneer Alkhatib,Qusai Al Zureikat,Mustafa Al-Shaikhli,Basel Bani Ata,Talal Massad,Leen Al-Huneidy,Mohammed Qussay Al-Sabbagh,Abdallah Al-Ani 한국의학교육학회 2023 Korean journal of medical education Vol.35 No.1
Purpose: We aimed to evaluate the disparity between video-based learning and lecture-based learning on Jordanian medical students’ satisfaction. Methods: We conducted this cross-sectional study using a web-based questionnaire adapted from Student Evaluation of Educational Quality survey. Using convenience sampling, medical students studying at the University of Jordan and Jordan University Hospital were recruited. Participants in either clinical or basic-science years that have completed the entire survey were included in the final analysis. Results: We surveyed a total 487 participants among which male to female ratio was 1.19:1. Participants perceived greater benefit in terms of learning, instructor enthusiasm, content organization, breadth of teaching, and quality and number of assignments when using video-based learning (all p<0.01). In contrast, face-to-face learning was associated with significantly higher benefits in terms of group interactions (p<0.01) and capacity for rapport building (p<0.01). There was no significant difference in perceived examination performance between the two learning modalities (p=0.11). Conclusion: Video-based learning is the preferred learning modality among Jordanian medical students. Despite its dominance across multiple domains, it should be implemented as an adjunct to traditional classroom teaching for it is vital in the development of good communication skills and building rapport in medical students.
Analyzing the Impact of Social Distancing on the Stoning Ritual of the Islamic Pilgrimage
Qazi Mudassar Ilya,Muneer Ahmad,Noor Zaman Jhanjhi,Muhammad Bilal Ahmad 한국인터넷정보학회 2022 KSII Transactions on Internet and Information Syst Vol.16 No.6
The COVID-19 pandemic has resulted in a profound impact on large-scale gatherings throughout the world. Social distancing has become one of the most common measures to restrict the spread of the novel Coronavirus. Islamic pilgrimage attracts millions of pilgrims to Saudi Arabia annually. One of the mandatory rituals of pilgrimage is the symbolic stoning of the devil. Every pilgrim is required to perform this ritual within a specified time on three days of pilgrimage. This ritual is prone to congestion due to strict spatiotemporal requirements. We propose a pedestrian simulation model for implementing social distancing in the stoning ritual. An agent-based simulation is designed to analyze the impact of inter-queue and intra-queue spacing between adjacent pilgrims on the throughput and congestion during the stoning ritual. After analyzing several combinations of intra-queue and inter-queue spacings, we conclude that 25 queues with 1.5 meters of intra-queue spacing result in an optimal combination of throughput and congestion. The Ministry of Hajj in Saudi Arabia may benefit from these findings to manage and plan pilgrimage more effectively.
EPIS, DOMINIONS AND ZIGZAG THEOREM IN COMMUTATIVE GROUPS
Shah, Aftab Hussain,Nabi, Muneer,Ahanger, Shabir Ahmad The Kangwon-Kyungki Mathematical Society 2022 한국수학논문집 Vol.30 No.3
In this paper, we introduce the notion of tensor product in groups and prove its existence and uniqueness. Next, we provide the Isbell's zigzag theorem for dominions in commutative groups. We then show that in the category of commutative groups dominions are trivial. This enables us to deduce a well known result epis are surjective in the category of commutative groups.
Tailoring the Electrical Properties of Graphene Layers by Molecular Doping
Singh, Arun Kumar,Ahmad, Muneer,Singh, Vivek Kumar,Shin, Koo,Seo, Yongho,Eom, Jonghwa American Chemical Society 2013 ACS APPLIED MATERIALS & INTERFACES Vol.5 No.11
<P>It is an essential issue in graphene-based nanoelectronic and optoelectronic devices to tune the electrical properties of graphene layers, while preserving its unique band structure. Here, we report the tuning of electronic properties of single-, bi-, and trilayer mechanically exfoliated graphenes by <I>p</I>-toluenesulfonic acid (PTSA) molecular doping. Raman spectroscopy and charge transport measurements revealed that PTSA molecule imposes <I>n</I>-doping to single-, bi-, and trilayer graphenes. The shift of G and 2D peak frequencies and intensity ratio of single-, bi-, and trilayer graphenes are analyzed as a function of reaction time. The Dirac point is also analyzed as a function of reaction time indicates the <I>n</I>-type doping effect for all single-, bi-, and trilayer graphenes. Our study demonstrates that chemical modification is a simple approach to tailor the electrical properties of single-, bi-, and trilayer graphenes, while maintaining the important electrical assets.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2013/aamick.2013.5.issue-11/am401119j/production/images/medium/am-2013-01119j_0008.gif'></P>
Hussain, Sajjad,Iqbal, Muhmmad Waqas,Park, Jaehyun,Ahmad, Muneer,Singh, Jai,Eom, Jonghwa,Jung, Jongwan Springer 2014 NANOSCALE RESEARCH LETTERS Vol.9 No.1
<P>Hydrogen flow during low pressure chemical vapor deposition had significant effect not only on the physical properties but also on the electrical properties of graphene. Nucleation and grain growth of graphene increased at higher hydrogen flows. And, more oxygen-related functional groups like amorphous and oxidized carbon that probably contributed to defects or contamination of graphene remained on the graphene surface at low H<SUB>2</SUB> flow conditions. It is believed that at low hydrogen flow, those remained oxygen or other oxidizing impurities make the graphene films p-doped and result in decreasing the carrier mobility.</P>
Nur ‘Aisyah Binti Zakaria Adli,Muneer Ahmad,Norjihan Abdul Ghani,Sri Devi Ravana,Azah Anir Norman 한국인터넷정보학회 2024 KSII Transactions on Internet and Information Syst Vol.18 No.2
COVID-19 was declared a pandemic by theWorld Health Organization (WHO) on 30 January 2020. The lifestyle of people all over the world has changed since. In most cases, the pandemic has appeared to create severe mental disorders, anxieties, and depression among people. Mostly, the researchers have been conducting surveys to identify the impacts of the pandemic on the mental health of people. Despite the better quality, tailored, and more specific data that can be generated by surveys, social media offers great insights into revealing the impact of the pandemic on mental health. Since people feel connected on social media, thus, this study aims to get the people’s sentiments about the pandemic related to mental issues. Word Cloud was used to visualize and identify the most frequent keywords related to COVID-19 and mental health disorders. This study employs Majority Voting Ensemble (MVE) classification and individual classifiers such as Naïve Bayes (NB), Support Vector Machine (SVM), and Logistic Regression (LR) to classify the sentiment through tweets. The tweets were classified into either positive, neutral, or negative using the Valence Aware Dictionary or sEntiment Reasoner (VADER). Confusion matrix and classification reports bestow the precision, recall, and F1-score in identifying the best algorithm for classifying the sentiments.
Yong, Hyeondeuk,Kim, Kiyeol,Choi, Wooseok,Park, Joonkyu,Ahmad, Muneer,Seo, Yongho Elsevier 2012 Carbon Vol.50 No.12
<P><B>Abstract</B></P><P>A graphene cellular array on an insulating SiO<SUB>2</SUB> layer was fabricated by scanning probe lithography. The graphene layer was oxidized by an electric field which was applied between the cantilever tip and Si substrate without any electrode directly connected to the graphene layer. When the bias voltage was applied on a cell of patterned graphene through the cantilever tip, charge was accumulated on the cell and preserved for a long time without decay. The accumulated charge and the surface potential were measured by an electrostatic force microscope. The charge retention was measured as a function of time, and the decay time constant was estimated to be ∼70min.</P>
Electrical and Thermal Conductivities of Stycast 1266 Epoxy/Graphite Composites
D. Hoang Tien,Joonkyu Park,Sang A Han,Muneer Ahmad,서용호,Koo Shin 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.4
Nanocomposites composed of graphene flake and epoxy resin (Stycast 1266) were produced with different concentrations of graphene in the range of 0 to 15 wt.%. Direct-current conductivity of the composites complied with percolation behavior. The percolation threshold concentration p_c from the conductivity measurement was estimated as 8 wt.% and the critical exponent t = 1.85 ?0.23. Alternating-current conductivity of the composite was increased monotonically as the frequency increased in range of 1 to 10 MHz. The thermal conductivity k also exhibited the similar percolation behavior with highest value k = 0.73 W/m∙K for 12 wt.% composite, which corresponded to 350% enhancement of the thermal conductivity.