Sharif Digital Repository

Direct solvent exfoliation of bulk MoS2 with the assistance of poly(3-hexylthiophene) (P3HT) produces a novel two-dimensional organic/inorganic semiconductor hetero-junction. The obtained P3HT-MoS2 nanohybrid exhibits unexpected optical limiting properties in contrast to the saturated absorption behavior of both P3HT and MoS2, showing potential in future photoelectric applications  

Hybrid nanomaterials have different applications and scientists have presented different methods to enhance the thermal efficiencies of cooling and heating systems, improving energy resources, thermal managements, extrusion processes, chemical reactions, etc. Current investigation reports a thermal study based on hybrid nanofluid model via fractional approach. The hybrid nanofluid contains molybdenum disulphide (MoS2) and graphene oxide (GO) nanoparticles. Engine oil is used as a base liquid for which thermal properties need to be enhanced. Additionally, the impact of magnetic force is studied for electrically conducting hybrid nanofluid. Fractional computations are performed using... 

Although there is a common view that the impact of Covid-19 should be similar among stock markets globally, empirical examinations of this issue are lacking. This study investigates the impacts of Covid-19 on the stock markets of countries in Gulf Cooperation Council (GCC) between September 2019 to July 2020. The findings of conventional t-test and non-parametric Mann-Whitney tests suggest that Covid-19 had a negative short-term impact on stock markets in GCC. This study also found that the stock markets of GCC countries are comparatively less impacted as compared to the effects suffered by the global stock markets. Lastly, the findings have confirmed the bidirectional spill over effect on... 

The simple-shear condition is closer to reality than the direct-shear condition for simulating the mechanical behavior of vegetated soil slope under shallow failure. However, study on simple-shear characteristics for vegetated slope is still insufficient, and there lacks intuitive comparison of characteristics between these two shear conditions. In this study, large-scale simple-shear and direct-shear experiments were conducted on soil permeated by roots of Amorpha fruticosa to investigate the shear strength and stiffness. The stress-displacement relationship of each sample was obtained and further normalized to unify the influence of root content. The results reveal that the direct-shear... 

Passive steel dampers have shown favorable performance in last earthquakes, numerical and experimental studies. Although steel dampers are more affordable than other types of damper, they are not economically justified for ordinary buildings. Therefore, in this paper, an innovative steel damper with shear yielding mechanism is introduced, which is easy to fabricate also can be easily replaced after sever earthquakes. The main goal of implementing such a mechanism is to control the possible damage in the damper and to ensure the elastic behavior of other structural components. The numerical results indicate an enhancement of the hysteretic behavior of the concentrically braced frames... 

Travel demand information in the form of the origin–destination (OD) matrix plays an essential role in studying urban traffic management and network design. The present study takes a novel step toward urban traffic analysis using data mining of processed images of real-time traffic maps as a location-based data model, in which the data were analyzed by software programs such as KNIME and Python workspaces and comparing the results with the conventional traffic assignment results. Thus, we investigated a real-time OD matrix based on the trip-per-vehicle by automatic number-plate recognition (ANPR) cameras for the congestion charge zone (CCZ) of Tehran, Iran. The obtained matrix was assigned... 

The thickness of shallow landslides is generally less than 2 m, which is of the same order of magnitude as the growth range of vegetation roots. Vegetation roots can improve the stability of shallow soil through mechanical and hydraulic effects. Therefore, the landslide process is closely related to the plant roots growing on the slope surface. Plant roots play a dominant role in the regulation of soil suction through solar radiation induced transpiration. However, little is known about the correlation between cumulative solar radiation and soil suction. Moreover, the specific effects of fine roots on the suction distribution are not clear in most previous studies. In this study, a vegetated... 

The aeroelastic flutter characteristics of a functionally graded carbon nanotube reinforced composite (FG-CNTRC) truncated conical shell under simultaneous actions of a hydrostatic pressure and yawed supersonic airflow are scrutinized. The nonlinearity in geometry of the conical shell is considered in Green–Lagrange sense and the model is derived according to the Novozhilov nonlinear shell theory. The aerodynamic pressure is modeled based on the quasi-steady Krumhaar's modified supersonic piston theory by considering the effect of the panel curvature and flow yaw angle. Parametric studies are conducted to investigate the effects of boundary conditions, semi-vertex angle, distribution and... 

The present research deals with bifurcation and vibration responses of a composite truncated conical shell with embedded single-walled carbon nanotubes (SWCNTs) subjected to an external pressure and axial compression simultaneously. The distribution of reinforcements through the thickness of the shell is assumed to be either uniform or functionally graded. The equations of motion are established using Green-Lagrange type nonlinear kinematics within the framework of Novozhilov nonlinear shell theory. Linear membrane prebuckling analysis is conducted to extract the prebuckling deformations. The stability equations are derived by applying the adjacent equilibrium criterion to the prebuckling... 

A discussion regarding speech accents will be given while describing a set of statistical signal processing methods for the modeling, analysis, synthesis, and morphing of English language accents. Accent morphing deals with the changing of the accent of a speech to a different accent. Accent itself is a distinctive pattern of pronunciation of speech within a community of people who belong to a national, geographic, or socioeconomic grouping. Then, the signal processing methodology for speech accent processing will be reviewed while the concept of an accent profile has been presented  

We analyse optimal pricing for a retailer that sells two products using a mixed price bundling strategy. We consider substitutable products, where there is a disutility associated with jointly consuming both products. Mixed price bundling implies that customers can freely choose to buy one of the two products, both of them, or neither of them. The retailer determines the price of each product when it is sold separately, the bundle discount if these two products are sold in a bundle, and the inventory levels for each product. We first derive the optimal price and bundle discount when the store traffic is deterministic. Our results show that the mixed bundling strategy is the most beneficial... 

Addressing the challenges of enhancing water-splitting efficiency necessitates the exploration and rational design of high-performance and durable electrocatalysts with appealing nanoarchitectures. In this study, we present the design and fabrication of conjugated cMOF/LDH hetero-nano petals decorated with monodispersed Metal-N sites, which are uniformly shelled over tungsten oxynitride (WNO) nanowire arrays to form a unique core–shell architecture. For this rational engineering, WNO nanowire arrays were grown on carbon cloth. Then, a thin-layered Ru-Co-Fe layered double hydroxide (RuCoFe/LDH) was deposited around these wires, resulting in a highly porous three-dimensional array of... 

In this paper, the effect of joint separation on the shear behavior of planar non-persistent joints under high normal load has been investigated using PFC2D. Initially calibration of PFC was undertaken with respect to the data obtained from experimental laboratory tests to ensure the conformity of the simulated numerical models response. Furthermore, validation of the simulated models were cross checked with the results of direct shear tests performed on non-persistent jointed physical models. Through numerical direct shear tests, the failure process was visually observed, and the failure patterns were found reasonably similar to the experimentally observed trends. The discrete element... 

Porphyrin-POM hybrid materials with excellent NLO properties are supposed to be a worthy entrant for forthcoming telecommunication, optical fibers, optical data storage and optical limiting devices, but due to adverse solubility problems, they are replaced by polymeric materials. Herein, we assessed third order NLO and second hyperpolarizability of porphyrin-polyimide compounds (NH-PI and Zn-PI) synthesized from the reaction of 4,4ʹ-hexafluoroisopropylidene-diphthalic anhydride (6FDA) with C44H32N6 (NH-DATPP) and C44H30N4Zn (Zn-DATPP) porphyrins under ambient conditions. The Z-scan measurement of these compounds revealed reverse saturation absorption as well as self-defocusing performance.... 

We study the capacity region of the two-user binary fading (or erasure) interference channel, where the transmitters have no knowledge of the channel state information. We develop new inner bounds and outer bounds for this problem. We identify three regimes based on the channel parameters: weak, moderate, and strong interference regimes. Interestingly, this is similar to the generalized degrees of freedom of the two-user Gaussian interference channel, where transmitters have perfect channel knowledge. We show that for the weak interference regime, treating interference as erasure is optimal while for the strong interference regime, decoding interference is optimal. For the moderate... 

Many communities in arid and semi-Arid areas rely on groundwater for drinking water. However, anthropogenic activities such as the use of fertilizers and human waste disposal impose the risk of nitrate pollution to the aquifers. With over 8.5 million population, Tehran, the capital of Iran, has experienced rapid population growth during the past decades while the majority of the city did not have a sewerage network and the main way of wastewater disposal was individual cesspits inside houses. The long-Term discharge of raw wastewater in cesspits has increased nitrate concentration in the Tehran aquifer which serves as a source of one-Third of drinking water for the city. Although the... 

Having a prime significance in diagonsing and predicting the dangerous symptoms of chronic diseases in the early stages, special attention has been drawn by wearable glucose-sensing platforms in recent years. Herein, modified commercial cotton fabrics, decorated with binary Ni–Co metal-organic frameworks (NC-MOFs) through a one-pot scalable hydrothermal route, were directly utilized as flexible electrodes for non-enzymatic glucose amperometric sensing. Glucose sensitivities of 105.2 μA mM−1 cm−2 and 23 μA mM−1 cm−2 were acheived within two distinct linear dynamic ranges of 0.04–3.13 mM and 3.63–8.28 mM, respectively. Receiving benefits from a remarkable glucose sensitivity behavior in... 

Osteocalcin is the most abundant noncollagenous bone protein and the functions in bone remineralization as well as in inhibition of bone growth have remained unclear. In this contribution, we explain the dual role of osteocalcin in the nucleation of new calcium phosphate during bone remodeling and in the inhibition of hydroxyapatite crystal growth at the molecular scale. The mechanism was derived using pH-resolved all-atom models for the protein, phosphate species, and hydroxyapatite, along with molecular dynamics simulations and experimental and clinical observations. Osteocalcin binds to (hkl) hydroxyapatite surfaces through multiple residues, identified in this work, and the fingerprint... 

Understanding the population growth patterns of Spodoptera exigua on alternate host plants can provide valuable information for developing an effective pest management program. In this study, using age-specific lifetable indices, we evaluated the role of alternate crops commonly found in cotton agroecosystem of Pakistan to better understand population dynamics of S. exigua. The longest larval and pupal periods (16.35 and 9.95days, respectively) were observed on spinach, while the shortest periods were recorded on okra (13 days) and cauliflower (8.4 days), respectively. Relatively more female moths (61%) were produced on spinach with low rm (0.095) and λ (1.0997) while highest rm (0.120) and... 

Understanding the population growth patterns of Spodoptera exigua on alternate host plants can provide valuable information for developing an effective pest management program. In this study, using age-specific lifetable indices, we evaluated the role of alternate crops commonly found in cotton agroecosystem of Pakistan to better understand population dynamics of S. exigua. The longest larval and pupal periods (16.35 and 9.95days, respectively) were observed on spinach, while the shortest periods were recorded on okra (13 days) and cauliflower (8.4 days), respectively. Relatively more female moths (61%) were produced on spinach with low rm (0.095) and λ (1.0997) while highest rm (0.120) and...