Sharif Digital Repository

Printing technologies have opened larger windows of innovation and creativity to biomaterials engineers by providing them with the ability to fabricate complex shapes in a reasonable time, cost, and weight. However, there has always been a trouble with function adjusting in printing technologies in view of the multiplicity of materials and apparatus parameters. 3D printing, also known as additive manufacturing, revolutionized biomaterials engineering by the conversion of a digital subject into a printed object (implants, scaffolds, or diagnostics and drug delivery devices/systems). Inspired by the lessons learned from 3D printing, the concept of 4D printing (better called shape-morphing... 

Liquid impingement cooling in the form of jet or spray is an appropriate method to remove heat from small surfaces progressively utilized in industry. In this study, numerical simulations are conducted to investigate the effect of surface structure on heat transfer characteristics. Five different three-dimensional structured surfaces are investigated using Euler-Lagrangian approach. The effect of surface structures is discussed on the liquid film thickness, the liquid film velocity, and the heat flux with its uniformity for a given spray and temperature characteristics. The results show that the convective heat transfer strongly depends on both liquid film thickness and velocity. While the... 

Tissue engineering (TE) and regenerative medicine have held great promises for the repair and regeneration of damaged tissues and organs. Additive manufacturing has recently appeared as a versatile technology in TE strategies that enables the production of objects through layered printing. By applying 3D printing and bioprinting, it is now possible to make tissue-engineered constructs according to desired thickness, shape, and size that resemble the native structure of lost tissues. Up to now, several organic and inorganic materials were used as raw materials for 3D printing; bioactive glasses (BGs) are among the most hopeful substances regarding their excellent properties (e.g., bioactivity... 

Multilateral well is a promising technology in developing oil reservoirs. Because this technology may increase the production rate per well and reduce the costs of field development, it is rapidly replacing the old methods. This study uses a three-dimensional line-source model with direct search methods, including pattern search and genetic algorithms to optimize the well trajectories. This method was applied to several cases, with different forms of wells and reservoirs. In all cases, significant improvement was observed in the production rate. Furthermore, the production enhancement using the optimized well trajectories which have curved-paths is compared to the case with linear well... 

Polylactic acid (PLA) scaffolds produced by the fused deposition modeling (FDM) method have biocompatibility, close Young's modulus to that of bone, and the ability to make complex shapes. However, PLA has some drawbacks like brittleness, inappropriate mechanical strength and hydrophobicity, and a low degradation rate. In this study, polyethylene glycol (PEG) (5 and 10 wt%) by solving method and titanium (Ti) particles (5 wt%) by two different methods were mixed with PLA to address the mentioned problems. Extruded filaments were investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and fourier transform infrared (FTIR). Surface morphology of the produced filaments... 

The employment of tissue engineering scaffolds in the reconstruction of the damaged bone tissues has shown remarkable promise since they significantly facilitate the healing process. Fabrication of highly porous biocompatible scaffolds with sufficient mechanical strength is still challenging. In this regard, polymers have been widely utilized to construct three-dimensional (3D) porous scaffolds due to their excellent processability and biocompatibility. However, insufficient mechanical strength and inappropriate degradation rate of the monophasic polymer scaffolds in the bone regeneration process, as the main challenges, limit their extensive clinical application. The incorporation of... 

In this study, the nodal discontinuous Galerkin method is formulated in three-dimensions and applied to simulate three-dimensional non-cavitating/cavitating flows. For this aim, the three-dimensional preconditioned Navier-Stokes equations based on the artificial compressibility approach considering appropriate source terms to model cavitating phenomena are used. The spatial derivative terms in the resulting equations are discretized by utilizing the nodal discontinuous Galerkin method on tetrahedral elements and the derivative of the solution vector with respect to the artificial time is discretized by applying an explicit time integration method. An artificial viscosity method is formulated... 

In this study, a detailed numerical analysis of the fluid flow and heat transfer of a three-dimensional microchannel is performed to evaluate the effect of using periodic vertical porous and solid ribs with various geometrical shapes, including rectangular, elliptical, isosceles triangular, backward triangular and forward triangular on the walls of this microchannel. Darcy-Brinkman-Forchheimer equations are used to model transport through the porous medium. The results for microchannels with solid ribs and with porous ribs are compared to each other. It is found that at the lowest studied inlet velocity (uin=0.25m/s), for the rib heights of Hr=0.025mm,0.05mmand0.07mm, the average Nusselt... 

Abstract: The convection–diffusion process of carbon dioxide (CO2) dissolution in a saline reservoir is investigated to shed light on the effects of the permeability heterogeneity. Using sequential Gaussian simulation method, random permeability fields in two and three-dimension (2D and 3D) structures are generated. Quantitative (average amount of the dissolved CO2 and dissolution flux) and qualitative (pattern of the dissolved CO2 and velocity streamlines) measurements are used to investigate the results. A 3D structure shows a slightly higher dissolution flux than a 2D structure in the homogeneous condition. Results in the random permeability fields in 2D indicates an increase in the... 

In this study, a novel three-dimensional continuous-time integrated guidance and control (IGC) scheme is presented. The proposed method is developed on the basis of generalized model predictive control (GMPC) approach and super-twisting extended state observer (STESO). The GMPC is used to generate the optimal closed form control law for the interceptor and the STESO is applied to estimate the maneuvering target lateral accelerations as well as the lumped disturbances. To the aim of IGC design, a six-degrees-of-freedom model based on the interceptor-target kinematics and interceptor dynamics is constructed. Afterward, the GMPC control law formulation for a nonlinear system exposed to... 

This paper presents a case study and numerical simulations of a corner of a deep excavation in Tehran supported by soldier piles and ground anchors. This study focuses on the differences between 2D and 3D numerical modelling in estimating the wall deflection at the corner locations of the excavation. Furthermore, the performance of modelling with Mohr–Coulomb constitutive law was compared with the result of a hardening soil model. The modelling procedure was calibrated against a full-scale instrumented tieback wall at Texas A&M University and the monitoring data of the excavation project. The results indicated that the hardening soil model yields reasonable predictions of wall deflection in... 

Purpose: The purpose of this paper is to investigate the effects of geometrical parameters, eccentricity and perforated fins on natural convection heat transfer in a finned horizontal annulus using three-dimensional lattice Boltzmann flux solver. Design/methodology/approach: Three-dimensional lattice Boltzmann flux solver is used in the present study for simulating conjugate heat transfer within an annulus. D3Q15 and D3Q7 models are used to solve the fluid flow and temperature field, respectively. The finite volume method is used to discretize mass, momentum and energy equations. The Chapman–Enskog expansion analysis is used to establish the connection between the lattice Boltzmann equation... 

The objective of the research is to determine the effect of friction stir processing (FSP) parameters and vibration on the machining behavior of AZ91 alloy. The article displays the state of the art of AZ91 alloy machinability including chip formation, chip morphology, and cutting forces. In this method, the vibration was applied to the process line through the fixture under the workpiece during the FSP. The three-dimensional finite element (FE) modeling was applied for simulating the small-hole drilling process of AZ91 alloy. The large deformation of work and the chip formation in drilling process is realized by incorporating Johnson-Cook material constitutive model and material failure... 

Single-task learning in artificial neural networks will be able to learn the model very well, and the benefits brought by transferring knowledge thus become limited. In this regard, when the number of tasks increases (e.g., semantic segmentation, panoptic segmentation, monocular depth estimation, and 3D point cloud), duplicate information may exist across tasks, and the improvement becomes less significant. Multi-task learning has emerged as a solution to knowledge-transfer issues and is an approach to scene understanding which involves multiple related tasks each with potentially limited training data. Multi-task learning improves generalization by leveraging the domain-specific information... 

Anatomical image segmentation is one of the foundations for medical planning. Recently, convolutional neural networks (CNN) have achieved much success in segmenting volumetric (3D) images when a large number of fully annotated 3D samples are available. However, rarely a volumetric medical image dataset containing a sufficient number of segmented 3D images is accessible since providing manual segmentation masks is monotonous and time-consuming. Thus, to alleviate the burden of manual annotation, we attempt to effectively train a 3D CNN using a sparse annotation where ground truth on just one 2D slice of the axial axis of each training 3D image is available. To tackle this problem, we propose... 

Measurements of spinal segment ranges of motion (RoMs), movement coordination, and three-dimensional kinematics during occupational activities have implications in occupational/clinical biomechanics. Due to the large amount of adipose tissues, obese individuals may have different RoMs, lumbopelvic coordination, and kinematics than normal-weight ones. We aimed to measure/compare trunk, lumbar, and pelvis primary RoMs in all anatomical planes/directions, lumbopelvic ratios (lumbar to pelvis rotations at different trunk angles) in all anatomical planes/directions and three-dimensional spine kinematics during twelve symmetric/asymmetric statics load-handling activities in healthy normal-weight... 

Purpose: Spiral-wound heat exchangers (SWHEs) are widely used in different industries. In special applications, such as cryogenic (HEs), fluid properties may significantly depend on fluid temperature. This paper aims to present an analytical method for design and rating of SWHEs considering variable fluid properties with consistent shell geometry and single-phase fluid. Design/methodology/approach: To consider variations of fluid properties, the HE is divided into identical segments, and the fluid properties are assumed to be constant in each segment. Validation of the analytical method is accomplished by using three-dimensional numerical simulation with shear stress transport k-ω model, and... 

The effects of liquefaction induced lateral spreading on the piles of a dolphin-type berth were investigated using 1 g large scale shake table testing accompanied by numerical simulations. For this purpose, various aspects of the response of the soil and the pile group to lateral spreading were considered. The results indicated that large bending moments were induced in the piles during lateral spreading and the downslope piles of the group received greater bending moments than the upslope one. The monotonic components of bending moments in the piles were reasonably predicted by the displacement based numerical approach using p-y springs when they were properly tuned for strength reduction... 

The solar collectors absorb solar irradiation and then produce thermal energy; however, they cannot generate electrical power. Electricity and thermal energy can be produced by the photovoltaic thermal module, simultaneously, while the outlet temperature of the photovoltaic thermal module is not usually high enough to provide thermal requirements of a building such as hot water or space heating. This work proposes a novel compound system created by the connection of a solar collector in series with a photovoltaic thermal module to resolve the issue of low outlet temperature in the photovoltaic thermal module and lack of electrical power in solar collectors. To examine the feasibility of this... 

In this article, an integrated guidance and control design method for general nonlinear flexible hypersonic flight vehicles in the presence of dynamic uncertainties based on the (Formula presented.) adaptive state feedback control approach is presented. Initially, the 6-degree-of-freedom integrated guidance and autopilot dynamic model is organized using the combination of flexible uncertain hypersonic flight vehicle dynamic model and hypersonic flight vehicle-target relative motion model whereas aerodynamic and model uncertainties, cross-coupling effects, and disturbances are considered. The proposed integrated guidance and control method based on (Formula presented.) adaptive control scheme...