Sharif Digital Repository

Zeolitic imidazole frameworks (ZIFs) provide an exciting platform to design and fabricate non-precious-metal carbon-based catalysts for oxygen reduction/evolution reaction (ORR/OER). Herein, we elaborately design a facile enzyme-assisted synthetic strategy that enables to tailor the ZIFs precursors into structural stable decussation shape, which derived Co nanoislands grafted on decussate N-doped carbon nanoleaves (D-Co@NC) can well retain the interpenetrating nanostructure. Benefiting from the combined advantages of compositions and interpenetrating nanostructures, D-Co@NC possesses 5.2 times higher exposed electrochemical active area than the conventional dodecahedral one, thus endowing... 

Rockfall is a significant hazard to sites that are located at the foot of rock slopes. In such sites, there is a notable need to evaluate the potential for rockfall, estimate the extent of areas at risk, and design retaining structures to reduce the risk of rockfall-induced. This paper presents a probabilistic framework for predicting the formation and progression of rockfalls and for evaluating the performance of retaining walls under rockfalls. To this end, first a probabilistic model for the rock projectile motion on a slope is presented. The model accounts for prevailing uncertainties, i.e., the trigger points, rock shape, projectile path, and slope material properties, which include... 

In this paper, we consider a wireless cooperative network with a wireless-powered energy harvesting (EH) relay. The relay employs a time switching (TS) policy that switches between the EH and data decoding (DD) modes. Both energy and data buffers are kept at the relay to store the harvested energy and decoded data packets, respectively. In this paper, we derive static and dynamic TS policies that maximize the system throughput or minimize the average transmission delay. In particular, in the static policies, the EH or DD mode is selected with a pre-determined probability. In contrast, in a dynamic policy, the mode is selected dynamically according to the states of data and energy buffers. We... 

In the current work, the role of Co and Ag co-doping on the electric, optical, and sensing performance of tin dioxide nano particles was investigated. Hydrothermally (co-)precipitation of the dopants was utilized to fabricate pure SnO2 and Sn0.96-xCo0.04AgxO2 (x = 0, 0.02, 0.04) nanoparticles. The crystal structure and microstructure of SnO2 particles was almost unchanged although Co-Ag co-doping reduced particle size from 51.8 nm to 41.6 nm and the unit cell dimensions changed. Overall, Co and Ag resulted in significant rise in oxygen vacancy of SnO2 so that defects compensate unbalanced electron charge induced by dopants. It was also figured out that Co-Ag co-doping improved the... 

Microorganisms have been essential in the natural world for millions of years, contributing significantly to environmental interaction. It has been disoverd that some bacteria are potential in geotechnical and environmental engineering due to their outstanding ability of biomineralization. Therefore, how to train bacteria as special and professional “workers” for biomineralization is increasingly a key topic in related research fields. This article briefly introduces the methods that are commonly utilized to improve the environmental adaptability and mineralization efficiency of bacteria, including microbial domestication, microbial mutation breeding, microbial targeted screening, and... 

We study the problem of multi-user dynamic searchable symmetric encryption (DMUSSE) where a data owner stores its encrypted documents on an untrusted remote server and wishes to selectively allow multiple users to access them by issuing keyword search queries. Specifically, we consider the case where some of the users may be corrupted and colluding with the server to extract additional information about the dataset (beyond what they have access to). We provide the first formal security definition for the dynamic setting as well as forward and backward privacy definitions. We then propose SE, the first provably secure DMUSSE scheme and instantiate it in two versions, one based on oblivious... 

The effect of temperature on the short-range order (SRO) structures, deformation mechanisms and failure modes of metallic glasses (MGs) is of fundamental importance for their practical applications. However, due to lack of direct structural information at the atomistic level from experiments and the absence of previous molecular dynamics (MD) simulations to reproduce experimental observations over a wide range of temperature, this issue has not been well understood. Here, by carefully constructing the atomistic models of Cu64Zr36 and Fe80W20 MGs, we are able to reproduce the major deformation modes observed experimentally, i.e. single shear banding (SB) at low temperatures, multiple... 

The demonstration of high entropy alloys (HEAs), or more generally multi-principal-element alloys (MPEAs), which display a greater resistance to softening at elevated temperatures and embrittlement at cryogenic temperatures, has offered an accessible alternative alloying process for materials scientists and engineers. Although solidification is a fundamental process in synthesis of alloys which strongly affects their microstructure and properties, a firm understanding of this process in HEAs is scarce. Here, using molecular dynamics (MD) simulations, we study the rapid solidification of the multi-principal-element CoFeNiPd alloy as a prototypical single-phase HEA. Our simulations reveal an... 

We study the problem of multi-user dynamic searchable symmetric encryption (DMUSSE) where a data owner stores its encrypted documents on an untrusted remote server and wishes to selectively allow multiple users to access them by issuing keyword search queries. Specifically, we consider the case where some of the users may be corrupted and colluding with the server to extract additional information about the dataset (beyond what they have access to). We provide the first formal security definition for the dynamic setting as well as forward and backward privacy definitions. We then propose μSE, the first provably secure DMUSSE scheme and instantiate it in two versions, one based on oblivious... 

Human infertility is a multifactorial disease that affects 8%–12% of reproductive-aged couples worldwide. However, the genetic causes of human infertility are still poorly understood. Synaptonemal complex (SC) is a conserved tripartite structure that holds homologous chromosomes together and plays an indispensable role in the meiotic progression. Here, we identified three homozygous mutations in the SC coding gene C14orf39/SIX6OS1 in infertile individuals from different ethnic populations by whole-exome sequencing (WES). These mutations include a frameshift mutation (c.204_205del [p.His68Glnfs∗2]) from a consanguineous Pakistani family with two males suffering from non-obstructive... 

We report the development of an efficient, customized spherical indentation-based testing method to systematically estimate the hydraulic permeability of gelatin methacryloyl (GelMA) hydrogels fabricated in a wide range of mass concentrations and photocrosslinking conditions. Numerical simulations and Biot's theory of poroelasticity were implemented to calibrate our experimental data. We correlated elastic moduli and permeability coefficients with different GelMA concentrations and crosslinking densities. Our model could also predict drug release rates from the GelMA hydrogels and diffusion of biomolecules into the three-dimensional GelMA hydrogels. The results potentially provide a design... 

This article focuses on the impact of waviness and aggregation of nanofillers on wave dispersion behavior of the nanocomposite curved beam strengthened with multi-walled carbon nanotubes (MWCNTs). In fact, the aggregation phenomenon is an inevitable subject in the manufacturing process of strengthened nanocomposite materials. Furthermore, in reality, usage of straight nanoreinforcements is almost impossible. So, MWCNTs can be wavy. These noted topics can significantly affect mechanical behavior of reinforced nanocomposite structures. In the current investigation, aggregation and waviness factors are accounted for through a modified Halpin-Tsai micromechanical homogenization model. The... 

In a photoacoustic (PA) imaging system, the detectors are bandwidth-limited. Therefore, they capture PA signals with some unwanted ripples. This limitation degrades the resolution/contrast and induces sidelobes and artifacts in the reconstructed images along the axial direction. To compensate for the limited bandwidth effect, we present a PA signal restoration algorithm, where a mask is designed to extract the signals at the absorber positions and remove the unwanted ripples. This restoration improves the axial resolution and contrast in the reconstructed image. The restored PA signals can be considered as the input of the conventional reconstruction algorithms (e.g., Delay-and-sum (DAS) and... 

Nickel oxide (NiOx) is a promising hole transport material in inverted organic-inorganic metal halide perovskite solar cells. However, its low intrinsic conductivity hinders its further improvement in device performance. Here, we employ a trimercapto-s-triazine trisodium salt (TTTS) as a chelating agent of Ni2+ in the NiOx layer to improve its conductivity. Due to the electron-deficient triazine ring, the TTTS complexes with Ni2+ in NiOx via a strong Ni2+-N coordination bond and increases the ratio of Ni3+:Ni2+. The increased Ni3+ concentration adjusts the band structure of NiOx, thus enhancing hole density and mobility, eventually improving the intrinsic conductivity of NiOx. As a result,... 

Previous studies have shown that a small variation in the chemical composition of metallic glasses (MGs) can drastically alter their strength and ductility. However, the underlying structural origin and atomistic mechanisms remain unclear. Using large-scale molecular dynamics simulations, we studied the effect of chemical composition and affinity on the microstructure and deformation behaviour of Zr50Ni50 − xAlx MG by varying the value of x in the range of 5 ≤ x ≤ 25 (at.%). We show that an increase in x is able to strengthen and embrittle the material. In particular, a ductile (homogeneous deformation) to brittle (shear banding) transition occurs at x ~ 15. To reveal the structural origin,... 

This article intends to examine thermoelastic damping (TED) in circular cylindrical nanoshells by considering small-scale effect on both structural and thermal areas. To fulfill this aim, governing equations are extracted with the aid of nonlocal elasticity theory and dual-phase-lag (DPL) heat conduction model. Circular cylindrical shell is also modeled on the basis of Donnell–Mushtari–Vlasov (DMV) equations for thin shells. By inserting asymmetric simple harmonic oscillations of nanoshell into motion, compatibility and heat conduction equations, the size-dependent thermoelastic frequency equation is obtained. By solving this equation and deriving the frequency of nanoshell affected by... 

Plasma medicine, or the biomedical application of cold atmospheric plasma (CAP), is an expanding field within plasma research. CAP has demonstrated remarkable versatility in diverse biological applications, including cancer treatment, wound healing, microorganism inactivation, and skin disease therapy. However, the precise mechanisms underlying the effects of CAP remain incompletely understood. The therapeutic effects of CAP are largely attributed to the generation of reactive oxygen and nitrogen species (RONS), which play a crucial role in the biological responses induced by CAP. Specifically, RONS produced during CAP treatment have the ability to chemically modify cell membranes and... 

Lightweight shell-based lattice structures with various multifunctional applications can be fabricated with limited manufacturing constraints, thanks to the advancements of additive manufacturing technologies. However, there is always a geometric deviation between the 3D digital model and the additively manufactured lattice structure. In some cases, the geometric deviations may be as small as the machine accuracy, but they would cause a significant decrease in the strength of the lattice. In other cases, the lattice may not be so sensitive to geometric deviations. The sensitivity of lattice structures to the geometric deviations depends on their constituent material, loading condition,... 

The above article from IET Communications, published online on 16 December 2022 in Wiley Online Library (wileyonlinelibrary.com), has been retracted by agreement between the Interim Editor-in-Chief, Jian Ren, the Institution of Engineering and Technology (the IET) and John Wiley and Sons Ltd. This article was published as part of a Guest Edited special issue. Following an investigation, the IET and the journal have determined that the article was not reviewed in line with the journal's peer review standards and there is evidence that the peer review process of the special issue underwent systematic manipulation. Accordingly, we cannot vouch for the integrity or reliability of the content. As... 

In this paper, the problem of content caching in 5G cellular networks relying on social-aware device-to-device (D2D) communications is investigated. Our focus is on how to efficiently select important users (IUs) and how to allocate content files to the storage of these selected IUs to form a distributed caching system. We aim at proposing a novel approach for minimizing the downloading latency and maximizing the social welfare simultaneously. In particular, we first model the problem of maximizing the social welfare as a many-to-one matching game based on the social property of mobile users. We study this game by exploiting users’ social properties to generate the utility functions of the...