Sharif Digital Repository

For the first time, in this article, stable/unstable zones of multi-directional functionally graded (MD-FG) sector disks under aerodynamic pressures are sought. Also, because of porous media, the system is modeled as a poroelastic system. The damping matrix, together with the aerodynamic stiffness matrix, is modeled upon Krumhaar's modified supersonic piston hypothesis. For more accuracy of the results, the Series-Fourier expansion of displacement fields in two-dimension is considered. To solve the partial differential equations, the singular convolution integration method with a singular convolution, as a numerical solver, is used. The precision of the outcomes is verified with those... 

The Ukrainian economic crisis began with the start of the war and grew over time. This is because trade between countries was spread out because of problems with the supply chain. However, the energy sector in Ukraine is largely disturbed by this armed conflict. The purpose of this study was to test the impact of infrastructure damage, trade sanctions, the economic crisis, and energy investments in green energy in Ukraine through the lens of sustainable development goals (SGDs). The data is collected from the Ukrainian public, and the sample size for this research is 384. This research has used the structural equation modeling method by using Smart PLS 3 for data analysis. The findings of... 

In analysing the structural organization of a social network, identifying important nodes has been a fundamental problem. The concept of network centrality deals with the assessment of the relative importance of a particular node within the network. Most of the traditional network centrality definitions have a high computational cost and require full knowledge of network topological structure. On the one hand, in many applications we are only interested in detecting the top-k central nodes of the network with the largest values considering a specific centrality metric. On the other hand, it is not feasible to efficiently identify central nodes in a large real-world social network via... 

One of the most relevant characteristics of social networks is community structure, in which network nodes are joined together in densely connected groups between which there are only sparser links. Uncovering these sparse links (i.e. intercommunity links) has a significant role in community detection problem which has been of great importance in sociology, biology, and computer science. In this paper, we propose a novel approach, called CS-ComDet, to efficiently detect the inter-community links based on a newly emerged paradigm in sparse signal recovery, called compressive sensing. We test our method on real-world networks of various kinds whose community structures are already known, and... 

Accelerated bridge construction is recognized as an important method for bridge owners to accelerate the delivery of highway bridge projects. While the potential advantages of accelerated bridge construction are recognized, it is difficult for transportation specialists to quantify the risks and benefits of using accelerated bridge construction compared with conventional construction for specific bridge replacement or rehabilitation projects. A tool set, based on the analytic hierarchy process, is prepared for transportation specialists and decision makers to determine whether accelerated bridge construction is more effective than traditional construction for a given bridge replacement or... 

Identifying communities has always been a fundamental task in analysis of complex networks. Many methods have been devised over the last decade for detection of communities. Amongst them, the label propagation algorithm brings great scalability together with high accuracy. However, it has one major flaw; when the community structure in the network is not clear enough, it will assign every node the same label, thus detecting the whole graph as one giant community. We have addressed this issue by setting a capacity for communities, starting from a small value and gradually increasing it over time. Preliminary results show that not only our extension improves the detection capability of the... 

Phase detector design for clock and data recovery (CDR) becomes challenging as the number of pulse amplitude modulation (PAM) levels increases. This paper presents a bang-bang phase detector (BBPD) architecture for PAM with N-level signaling (PAM-N) that balances the complexity and performance by utilizing an edge slicer whose threshold is adjusted according to the types of transitions. To accommodate high-speed applications, one-eight-rate architecture with carefully chosen timing is exploited. The validity of the proposed BBPD is examined for its PAM-4 and PAM-6 versions in 28 nm CMOS technology. © 2023 IEEE  

A limited assessment of the development process and various stages of machine learning (ML) based solutions for construction engineering (CE) problems are available in the literature. After critically reviewing 467 published articles from 2017 to 2022, sixteen areas of improvement at different stages of ML projects’ development cycle are identified and discussed with examples from past studies. These areas of improvement are categorized along different stages of the development cycle of an ML-based engineering solution: 1) Justification of applying ML models, 2) employing the proper data collection strategy, 3) using accurate data pre-processing techniques, 4) selecting and training a model... 

Traditional fluorescence switching molecules achieving the state change between on and off states commonly based on UV irradiation. However, it is worth noting that UV irradiation is harmful to both the cancer cells and the normal cells. To achieve fluorescence switching under visible wavelength and avoid complicate molecular design, a fluorophore of 2,4,5,6-tetrakis(carbazol-9-yl)-1,3-dicyanobenzene (4CzIPN) and a quencher of diarylethene (DAE) were physically incorporated within the biocompatible block copolymer poly(lactic-co-glycolic acid)-b-poly(ethylene glycol) (PLGA-b-PEG) to form 4CzIPN-DAE nanoparticles (NPs) through flash nanoprecipitation (FNP). By using the FNP method, the NPs... 

In real-world networks, nodes might have more than one type of relationship. Signed networks are an important class of such networks consisting of two types of relations: positive and negative. Recently, embedding signed networks has attracted increasing attention and is more challenging than classic networks since nodes are connected by paths with multi-types of links. Existing works capture the complex relationships by relying on social theories. However, this approach has major drawbacks, including the incompleteness/inaccurateness of such theories. Thus, we propose network transformation based embedding to address these shortcomings. The core idea is that rather than directly finding the... 

Pesticides are widely used to increase agricultural productivity, however, weak adhesion and deposition lead to low efficient utilization. Herein, we prepare a nanopesticide formulation (tebuconazole nanopesticides) which is leaf-adhesive, and water-dispersed via a rapid nanoparticle precipitation method, flash nanoprecipitation, using temperature-responsive copolymers poly-(2-(dimethylamino)ethylmethylacrylate)-b-poly(ε-caprolactone) as the carrier. Compared with commercial suspensions, the encapsulation by the polymer improves the deposition of TEB, and the contact angle on foliage is lowered by 40.0°. Due to the small size and strong van der Waals interactions, the anti-washing efficiency... 

Four 5-, 10-, 20- and 30-story moment frames, representing low-, mid-, and two high-rise structures, were subjected to a great number of idealized directivity pulses. The amplitudes and periods of pulses vary from 0.02 g to 1.0 g and 0.5 to 12 sec, respectively. Over 1400 nonlinear dynamic analyses of low- to high-rise moment frames were performed which were feasible through using modified fish-bone model. The distribution of interstory drift along the height was studied and two applied contours were proposed: (i) the maximum interstory drift contour, and (ii) the critical story contour. These contours were demonstrated versus the ratio of natural period of the structure to the pulse period... 

In this article singular points of a parallel manipulator are obtained based on a novel geometrical method. Here we introduce the constrained plain method (CPM) and some of its application in parallel mechanism. Given the definition of constraint plane (CP) and infinite constraint plane (ICP) the dependency conditions of constraints is achieved with the use of a new theorem based on the Ceva geometrical theorem. The direction of angular velocity of a body is achieved by having three ICPs with the use of another theorem. Finally, with the use of the above two novel theorems singularities of the 3UPF_PU mechanism are obtained. It should be emphasized that this method is completely geometrical,... 

An analytical model is proposed to study the effect of particle size on melting enthalpy and entropy of metallic nanoparticles (NPs). The Mott's and Regel's equations for melting entropy in the combination of core average coordination number (CAC) and surface average coordination number (SAC) of freestanding NPs are considered. Clusters of icosahedral (IC), body centered cubic (BCC), and body centered tetragonal (BCT) structure without any vacancies and defects are modeled. Using the variable coordination number made this model to be in good agreement with experimental and molecular dynamic (MD) results of different crystal structures. The model predicts melting entropy and enthalpy of... 

Grinding is widely used for manufacturing of components that require fine surface finish and good dimensional accuracy. In this study a thermo-mechanical finite element analysis is conducted to find out how grinding parameters can affect temperature and residual stress distribution in the workpiece. Results of parametric study presented in this work indicate, by carefully selecting the grinding parameters, minimum thermal and mechanical damage can be achieved. Higher workpiece velocities produce higher surface residual stress. By increasing depths of cut, depth of tensile residual stresses increases. Convection heat coefficient does not have any considerable effect on surface residual stress... 

Adaptive Noise Cancellation (ANC) is a well-known technique for background noise reduction in automobile and vehicular environments. The noise fields in automobile and other vehicle interior obey the diffuse noise field model closely. On the other hand, the ANC does not provide sufficient noise reduction in the diffuse noise fields. In this paper, a new multistage post-filter is designed for ANC as a solution to diffuse noise conditions. The designed post-filter is a single channel Linear Prediction (LP) based speech enhancement system. The LP is performed by an adaptive lattice filter and attempts to extract speech components by using intermediate ANC signals. The post-filter has no... 

Shot peening is widely used to improve the fretting fatigue strength of critical surfaces. Fretting fatigue occurs in contacting parts that are subjected to fluctuating loads and sliding movements at the same time. This paper presents a sequential finite element simulation to investigate the shot peening effects on normal stress, shear stress, bulk stress and slip amplitude, which are considered to be the controlling parameters of fretting damage. The results demonstrated that among the modifications related to shot peening, compressive residual stress has a dominant effect on the fretting parameters  

One-dimensional (1D) MgO structures were successfully synthesized via carbothermic reduction of mechanically activated mixture of MgO and graphite. Mechanical activation of source materials before carbothermic reduction can substantially enhance the formation of MgO products at a temperature (1000 °C) relatively lower than that required in previous approaches (≥1200 °C). However, the morphology of MgO formed is dependent on the degree of mechanical activation and the condition of the subsequent carbothermic reduction. Two distinctive morphologies were found for MgO products synthesized using our method: single crystalline nanorods with rectangular cross-sections whose diameters range from 50... 

Attitude and vibration control of a general form of flexible satellites is addressed in this paper. Partial differential dynamic equations are derived considering new details such as multi sectioned solar panels and elastic connections between main hub and solar panels. Boundary control approach is adopted to eliminate simplification errors of discrete models, using just one actuator in the hub. Asymptotic stability of attitude dynamics is proved for a group of boundary controllers and necessary conditions for asymptotic stability of vibrations are discussed. Being independent of modeling accuracy and using easily measurable feedbacks are among advantages of the proposed class of... 

Characterization and calcination behavior of a low-grade manganese ore, as a part of Mn ferroalloys production, was studied by XRF, ex-situ XRD, in-situ XRD, and SEM-EDS techniques. Calcination experiments were carried out at and up to 900 °C (1173 K) in air and argon atmospheres. The samples were in particles and powder forms. The results indicated that both quartz and calcite phases in the ore exhibit a bimodal spatial distribution; as relatively large regions and finely distributed in the Mn- and Fe-containing phases. By Rietveld analysis of the in-situ XRD data, the reactions occurring upon heating during the calcination process were deduced. Thermal decomposition and reactive diffusion...