Rational hybrid modulation of P, N dual-doped holey graphene for high-performance supercapacitors

Nazarian-Samani, Masoud,Haghighat-Shishavan, Safa,Nazarian-Samani, Mahboobeh,Kim, Myeong-Seong,Cho, Byung-Won,Oh, Si-Hyoung,Kashani-Bozorg, Seyed Farshid,Kim, Kwang-Bum Elsevier Sequoia 2017 Journal of Power Sources Vol. No.

<P><B>Abstract</B></P> <P>A P, N dual-doped holey graphene (PNHG) material is prepared by a scalable, facile synthetic approach, using a mixture of glucose, dicyandiamide (DCDA), and phosphoric acid (H<SUB>3</SUB>PO<SUB>4</SUB>). H<SUB>3</SUB>PO<SUB>4</SUB> successfully functions as an “acid catalyst” to encourage the uniform breakage of C=C bonds to create large, localized perforations over the graphene monolith. Further acid treatment and annealing introduce in-plane holes. The correlation between the capacitance of the PNHG and its structural parameters during the fabrication process is comprehensively evaluated. A thermally induced sp<SUP>2</SUP>→sp<SUP>3</SUP> transformation occurs at high temperatures because of the substantial loss of graphitic sp<SUP>2</SUP>-type carbons, together with a dramatic reduction in capacitance. The target PNHG-400 electrode material delivers exceptionally high gravimetric capacitance (235.5 F g<SUP>−1</SUP> at 0.5 A g<SUP>−1</SUP>), remarkable rate capability (84.8% at 70 A g<SUP>−1</SUP>), superior capacitance retention (93.2 and 92.7% at 10 and 50 A g<SUP>−1</SUP> over 25000 cycles, respectively), and acceptable volumetric capacitance due to moderate density, when it is used with organic electrolytes in the voltage range between 0 and 3 V. These results suggest a pioneering defect-engineered strategy to fabricate dual-doped holey graphene with valuable structural properties for high-performance electric double layer supercapacitors, which could be used in next-generation energy storage applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Rationally designed P, N dual-doped holey graphene as an electrode in supercapacitors. </LI> <LI> Importance of synergistic ion transport with a high content of C=C bonds. </LI> <LI> Occurrence of sp<SUP>2</SUP>→sp<SUP>3</SUP> transition in graphene structure at temperatures higher than 400 °C. </LI> <LI> High capacitance, excellent rate capability and cyclic stability of the target PNHG-400. </LI> <LI> Novel approach to develop future supercapacitors with high energy and power densities. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Fabrication of well-designed defect-laden holey graphene counterparts for energy-related applications using a simple, up-scalable and cost-effective strategy.</P> <P>[DISPLAY OMISSION]</P>

Large-Scale Refinement of Metal−Organic Framework Structures Using Density Functional Theory

Nazarian, Dalar,Camp, Jeffrey S.,Chung, Yongchul G.,Snurr, Randall Q.,Sholl, David S. American Chemical Society 2017 Chemistry of materials Vol.29 No.6

<P>Efforts to computationally characterize large numbers of nanoporous materials often rely on databases of experimentally resolved crystal structures. The accuracy of experimental crystal structures used in such calculations has a significant impact on the reliability of the results. In this work, we report structures optimized using periodic density functional theory (DFT) for more than 800 experimentally synthesized metal-organic frameworks (MOFs). Many MOFs changed significantly upon structural optimization, particularly materials that were crystallographically resolved in their solvated form. For each MOF, we simulated the adsorption of CH4 and CO2 using grand canonical Monte Carlo both before and after DFT optimization. The DFT optimization has a large impact on simulated gas adsorption in some cases. For example, CO2 loading at 1 bar changed by more than 25% in over 25% of the MOFs we considered.</P>

A robust design of Ru quantum dot/N-doped holey graphene for efficient Li-O2batteries

Nazarian-Samani, Masoud,Lim, Hee-Dae,Haghighat-Shishavan, Safa,Kim, Hyun-Kyung,Ko, Youngmin,Kim, Myeong-Seong,Lee, Suk-Woo,Kashani-Bozorg, Seyed Farshid,Abbasi, Majid,Guim, Hwan-Uk,Kim, Dong-Ik,Roh, K The Royal Society of Chemistry 2017 Journal of Materials Chemistry A Vol.5 No.2

<P>Herein, we report a simple, versatile, defect-engineered method to fabricate Ru quantum dots (Ru QDs) uniformly anchored on a nitrogen-doped holey graphene (NHG) monolith. It uses<I>in situ</I>pyrolysis of mixed glucose, dicyandiamide (DCDA), and RuCl3, followed by an acid treatment, and a final heat treatment to introduce in-plane holes of various sizes. A novel transmission method in scanning electron microscopy was successfully implemented to directly visualize the holes with color contrast. A low accelerating voltage of 5 kV enabled prolonged observation without significant electron beam damage. The mechanisms of hole creation were examined in detail using various characterization techniques as well as control experiments. The Ru QDs had significant catalytic activity and resulted in larger in-plane holes through the graphene sheets. The mechanical strain and the chemical reactivity of Ru QDs significantly diminished the activation energy barrier for the oxidation of CC bonds in the graphene structure. The Ru QD/NHG hybrid material was utilized as an electrocatalyst for the oxygen evolution reaction in Li-O2batteries, showing much lower charge overpotentials compared to the bare NHG counterpart. The defect-laden holey graphene counterpart can be highly functionalized for multiple applications, leading to a new method of nanoengineering based on atomic scale defects.</P>

Various shadowing properties for time varying maps

Javad Nazarian Sarkooh 대한수학회 2022 대한수학회보 Vol.59 No.2

This paper is concerned with the study of various notions of shadowing of dynamical systems induced by a sequence of maps, so-called time varying maps, on a metric space. We define and study the shadowing, h-shadowing, limit shadowing, s-limit shadowing and exponential limit shadowing properties of these dynamical systems. We show that h-shadowing, limit shadowing and s-limit shadowing properties are conjugacy invariant. Also, we investigate the relationships between these notions of shadowing for time varying maps and examine the role that expansivity plays in shadowing properties of such dynamical systems. Specially, we prove some results linking s-limit shadowing property to limit shadowing property, and h-shadowing property to s-limit shadowing and limit shadowing properties. Moreover, under the assumption of expansivity, we show that the shadowing property implies the h-shadowing, s-limit shadowing and limit shadowing properties. Finally, it is proved that the uniformly contracting and uniformly expanding time varying maps exhibit the shadowing, limit shadowing, s-limit shadowing and exponential limit shadowing properties.

Intelligent Controller Design for a Blowdown Supersonic Wind Tunnel

A. Nazarian Shahrbabaki,M. Bazazzadeh,A. Shahriari,M. Dehghan Manshadi 보안공학연구지원센터 2014 International Journal of Control and Automation Vol.7 No.1

A Brief Review of Assembly Supply Chain Research

Ehsan Nazarian 대한산업공학회 2014 ie 매거진 Vol.21 No.3

Maxillo-mandibular Defect Reconstruction with Bilateral Free Fibula Flaps with Dental Implant Placement and Immediate Loading: A Case Report of the Three-team Approach

David Nazarian,Aleksei Dikarev,Mikhail Mokhirev,Georgy Zakharov,Alexander Fedosov,Maksim Potapov,Mikhail Chernenkiy,Yuriy Vasilev,Grigoriy Kyalov,Saniyat Chausheva,Arbak Khachatryan,Artur Tevosyan,Gev 대한성형외과학회 2022 Archives of Plastic Surgery Vol.49 No.5

Patients with advanced malignant tumors, including both jaws, is a challenging task for a head and neck surgeon. Current treatment landscape demonstrates good functional, anatomical, and aesthetic results in patients who could previously receive only palliative care. The extensive tissue defects resulting from oncological resections in the head and neck region require immediate reconstruction due to the exposure of vital structures and their contact with the external environment. A patient was operated using a three-team multidisciplinary approach involving simultaneous work of three specialized teams of maxillofacial and reconstructive microsurgeons, as well as an implantologist and a prosthodontist. This approach allowed simultaneous tumor resection with subsequent reconstruction of the intraoperative defect involving bilateral harvesting of two revascularized free fibular osteomusculocutaneous flaps with dental implantation and simultaneous rehabilitation of dentition with crowns.

Strong, persistent superficial oxidation-assisted chemical bonding of black phosphorus with multiwall carbon nanotubes for high-capacity ultradurable storage of lithium and sodium

Haghighat-Shishavan, Safa,Nazarian-Samani, Masoud,Nazarian-Samani, Mahboobeh,Roh, Ha-Kyung,Chung, Kyung-Yoon,Cho, Byung-Won,Kashani-Bozorg, Seyed Farshid,Kim, Kwang-Bum The Royal Society of Chemistry 2018 Journal of Materials Chemistry A Vol.6 No.21

<P>We report a new composite of black phosphorus and multiwall carbon nanotubes (BP-CNT) prepared <I>via</I> a surface oxidation-assisted chemical bonding procedure. The controlled air exposure successfully changed the naturally hydrophobic BP powder to the desired hydrophilicity, which was found indispensable to stable bond formation between the BP and the functionalized CNTs during ball milling. The BP-CNT composites were further fabricated into anodes for both Li- and Na-ion batteries, using a sodium carboxyl methyl cellulose-poly(acrylic acid) (NaCMC-PAA) binary polymeric binder. The hydrophilicity of BP also played a very important role in forming strong bonds with the hydroxyl groups of NaCMC and the carboxylic acid groups of PAA. The plausible mechanisms of stable bond formation were comprehensively examined, and the results revealed two types of strong connections: P-O-C bonds and dehydration cross links. Consequently, the material delivered outstanding electrochemical performance in the anode, with a high discharge capacity of 1681 mA h g<SUP>−1</SUP> after 400 cycles at a current density of 0.2C (1C = 2596 mA g<SUP>−1</SUP>) for Li-ion batteries. It also successfully delivered a first discharge capacity of 2073 and 850 mA h g<SUP>−1</SUP> at 0.2C and 2C for Na-ion batteries, respectively, with excellent capacity retentions at both rates after 200 cycles. These salient results, which originated from the modified hydrophilic BP, will give further impetus to explore BP-based composites for use as high-performance materials for advanced energy storage applications.</P>

Does computer-aided diagnostic endoscopy improve the detection of commonly missed polyps? A meta-analysis

Arun Sivananthan,Scarlet Nazarian,Lakshmana Ayaru,Kinesh Patel,Hutan Ashrafian,Ara Darzi,Nisha Patel 대한소화기내시경학회 2022 Clinical Endoscopy Vol.55 No.3

Background/Aims: Colonoscopy is the gold standard diagnostic method for colorectal neoplasia, allowing detection and resection ofadenomatous polyps; however, significant proportions of adenomas are missed. Computer-aided detection (CADe) systems in endoscopyare currently available to help identify lesions. Diminutive (≤5 mm) and nonpedunculated polyps are most commonly missed. This meta-analysis aimed to assess whether CADe systems can improve the real-time detection of these commonly missed lesions. Methods: A comprehensive literature search was performed. Randomized controlled trials evaluating CADe systems categorized bymorphology and lesion size were included. The mean number of polyps and adenomas per patient was derived. Independent proportionsand their differences were calculated using DerSimonian and Laird random-effects modeling. Results: Seven studies, including 2,595 CADe-assisted colonoscopies and 2,622 conventional colonoscopies, were analyzed. CADe-assistedcolonoscopy demonstrated an 80% increase in the mean number of diminutive adenomas detected per patient compared withconventional colonoscopy (0.31 vs. 0.17; effect size, 0.13; 95% confidence interval [CI], 0.09−0.18); it also demonstrated a 91.7% increasein the mean number of nonpedunculated adenomas detected per patient (0.32 vs. 0.19; effect size, 0.05; 95% CI, 0.02−0.07). Conclusions: CADe-assisted endoscopy significantly improved the detection of most commonly missed adenomas. Although thismethod is a potentially exciting technology, limitations still apply to current data, prompting the need for further real-time studies.

On topological entropy and topological pressure of non-autonomous iterated function systems

Fatemeh H. Ghane,Javad Nazarian Sarkooh 대한수학회 2019 대한수학회지 Vol.56 No.6

In this paper we introduce the notions of topological entropy and topological pressure for non-autonomous iterated function systems (or NAIFSs for short) on countably infinite alphabets. NAIFSs differ from the usual (autonomous) iterated function systems, they are given \cite{LGMU} by a sequence of collections of continuous maps on a compact topological space, where maps are allowed to vary between iterations. Several basic properties of topological pressure and topological entropy of NAIFSs are provided. Especially, we generalize the classical Bowen's result to NAIFSs ensures that the topological entropy is concentrated on the set of nonwandering points. Then, we define the notion of specification property, under which, the NAIFSs have positive topological entropy and all points are entropy points. In particular, each NAIFS with the specification property is topologically chaotic. Additionally, the $\ast$-expansive property for NAIFSs is introduced. We will prove that the topological pressure of any continuous potential can be computed as a limit at a definite size scale whenever the NAIFS satisfies the $\ast$-expansive property. Finally, we study the NAIFSs induced by expanding maps. We prove that these NAIFSs having the specification and $\ast$-expansive properties.