Lagrangian simulation of fiber orientation dynamics using random walk methods

This thesis focuses on developing a two-way coupled framework for the numerical simulation of fiber suspension flows. The influence of fibers on the flow is accounted for by evaluating a non-Newtonian stress term incorporated into the Navier-Stokes equations. The accuracy of the analysis depends on a second-order tensor field used to approximate the orientation distribution of fibers. In this context, the disperse phase can be treated in the Lagrangian or Eulerian manner. We conduct a comprehensive comparison of these frameworks for one-way coupled scenarios in both two- and three-dimensional homogeneous flows. With a special focus on the Lagrangian approach, the algorithm for solving the two-way coupled fiber suspension flow in a segregated manner is proposed by incorporating the fiber-induced stresses in the finite element formulation of the Navier-Stokes equations. In non-dilute suspensions, fiber-fiber interactions may cause spontaneous changes in the orientation of fibers. Applying the theory of rotary Brownian motion, the effect can be studied using a rotary diffusion term with a Laplace-Beltrami operator. In this work, we develop random walk methodologies to emulate the action of the diffusion term without evolving or reconstructing the so-called orientation distribution function. After deriving simplified forms of Brownian motion generators for rotated reference frames, several practical approaches to generating random walks on the unit sphere are discussed. Among the proposed methods, this research effort presents the projection of Cartesian random walks, as well as polar random walks on the tangential plane. The standard random walks are then projected onto the unit sphere. Moreover, we propose an alternative based on a tabulated approximation of the cumulative distribution function obtained from the exact solution of the spherical heat equation. In the last part of this work, the random walk approaches are compared through several numerical studies, including the study of the orientation distribution of fibers in a three-dimensional homogeneous flow. Then, the two-way coupled solver is validated in a simple geometry, followed by performing a few three-dimensional numerical simulations to study the rheological behavior of the fiber suspension flow through an axisymmetric contraction. The effect of fiber-fiber interactions is also incorporated using the random walk methodology

Seismic Collapse Assessment of Self-Centering Steel Moment Resisting Frame Systems with Web Friction Devices

The design method used for conventional steel special moment resisting frame (SMRF) with welded beam-to-column connections leads to significant inelastic deformations and formation of plastic hinges in the beams under the design earthquake for seismic resistant steel frame buildings. This may cause significant damage. A self-centering (SC) moment resisting frame (SC-MRF) is a viable alternative to a conventional SMRF. The beams in an SC-MRF are post-tensioned to the columns by high strength post-tensioning (PT) strands oriented horizontally to provide SC forces when gap opening occurs. An SC-MRF is characterized by gap opening and closing at the beam-column interface under earthquake loading. The SC-MRF is typically designed to meet several seismic performance objectives, including no structural damage under the DBE in order to perform in a resilient manner. Recent analytical and experimental research has shown that an SC-MRF can achieve this performance objective. Since an SC-MRF system is a new concept little is known about its collapse resistance under extreme seismic ground motions. For an SC-MRF to be accepted in practice, the collapse resistance of this type of structural system under extreme ground motions must be established to assess whether it is adequate. Incremental Dynamic Analysis (IDA) are performed using an ensemble of 44 far-field ground motions to determine the probability of collapse of a 4-story low-rise building with perimeter SC-MRFs. A model of the SC-MRF was developed that included both stress-resultant and continuum finite elements to enable the important limit states, including local buckling in the beams, to be accounted for in the IDA. In order to compare the collapse performance of an SC-MRF with an SMRF a 4-story SMRF was designed and IDA performed to determine the collapse resistance of the SMRF. The results show that the collapse resistance of an SC-MRF system can exceed that of a conventional steel SMRF. In addition, the design of the SC-MRF is modified to investigate the collapse resistance sensitivity to the PT strand detailing, by varying the number of PT strands and level of PT force. The results show that collapse resistance is affected by the level of PT force, where an increased number of strands lead to a higher post-gap opening stiffness resulting in larger axial forces and local buckling developing in the beams. This leads to a higher probability of collapse than the original design and comparable with the collapse resistance of SMRF.Structures are built where active faults may be in close proximity. The probability of collapse of a 4-story low-rise building with perimeter SC-MRFs subjected to near-field ground motions was studied and compared to the results for far-field ground motions. IDA are performed using an ensemble of 56 near-field ground motions. The results show that the SC-MRF built close to active faults has less collapse resistance in contrast to the one built in seismic zones away from active faults. The structure has larger spectral acceleration for near-field ground motions than far-field ground motions at the fundamental period, leading to excessive inelastic deformations that cause structure collapse earlier. The results obtained, however, show that an acceptable margin against collapse is still achieved and therefore indicate a potential for an SC-MRF to be used in seismic zones with active near-field faults

Random walk implementation of rotary diffusion in Lagrangian models of fiber orientation

A comprehensive comparison of the Lagrangian and Eulerian frameworks for one-way coupled simulations of fiber suspension flows is performed for 2D and 3D models of orientation dynamics. An alternative approach to modeling the interactions of fibers is proposed for the Lagrangian framework. The presented methodology is based on the idea of the random walk, which is commonly used for modeling diffusion-like processes due to the Brownian motion of molecules. It is shown that a restriction of the random walk to the unit sphere provides an accurate description of orientation changes caused by interactions between fibers

Silver and Gold Nanoparticles for Antimicrobial Purposes against Multi-Drug Resistance Bacteria

Several pieces of research have been done on transition metal nanoparticles and their nanocomplexes as research on their physical and chemical properties and their relationship to biological features are of great importance. Among all their biological properties, the antibacterial and antimicrobial are especially important due to their high use for human needs. In this article, we will discuss the different synthesis and modification methods of silver (Ag) and gold (Au) nanoparticles and their physicochemical properties. We will also review some state-of-art studies and find the best relationship between the nanoparticles’ physicochemical properties and potential antimicrobial activity. The possible antimicrobial mechanism of these types of nanoparticles will be discussed in-depth as well

Effective factors on the number of decayed and filled teeth using the Conway-Maxwell-Poisson count model

BACKGROUND AND AIM: Recognizing the factors affecting the number of decayed and filled teeth has a major role in oral health. Dental data usually suffer from over-dispersion and excess zero frequencies. The purpose of this study was to use the Conway-Maxwell-Poisson (COM-Poisson) model to determine some of the factors affecting the number of decayed and filled teeth. METHODS: In this cross-sectional study, a sample of 1000 people from a cohort study in Shahrekord City, Iran, aged 35-70 years, was selected through systematic sampling. The data were analyzed using the Bayesian approach through Markov chain Monte Carlo (MCMC) simulation by OpenBUGS. Zero-inflated Poisson (ZIP), COM-Poisson model, and zero-inflated Com-Poisson (ZICMP) model were fitted on the data and compared using the deviance information criterion (DIC). RESULTS: The mean numbers of decayed and filled teeth were 0.77 ± 1.63 and 4.37 ± 4.62, respectively. The Com-Poisson and ZICMP showed to be better fit for the number of decayed and filled teeth, respectively. Those people who were younger, male, smokers, diabetics, did not floss, and did not use mouthwash had significantly more number of decayed teeth (P < 0.05). Those people who were younger, female, non-diabetics, non-smokers, employed, literate, had less body mass index (BMI), flossed, and got higher score of quality of life had significantly more number of filled teeth (P < 0.05). CONCLUSION: By controlling such factors as education, BMI, flossing, using mouthwash, smoking, diabetes, and quality of life, we could improve the oral health. KEYWORDS: Bayes’ Theorem; Conway-Maxwell-Poisson Distribution; Decayed, Missing, and Filled Teeth; Zero-inflate

Comparing the Antiemetic Effects of Ondansetron and Metoclopramide in Patients with Minor Head Trauma

Introduction: Nausea and vomiting are the most common complications after minor head trauma that increases the risk of intracranial pressure rising. Therefore, the present study was aimed to compare the antiemetic effects of metoclopramide and ondansetron in the treatment of post-traumatic nausea and vomiting. Methods: The study was a controlled, randomized, double blind clinical trial, which was conducted in the first 6 months of 2014 in emergency department Al-Zahra and Kashani Hospitals in Isfahan, Iran. The patients with minor head trauma associated with nausea and vomiting were randomly divided into 2 groups: treatment with metoclopramide (10mg/2ml, slow injection) and treatment with ondansetron (4mg/2ml, slow injection). The comparison between the 2 groups was done regarding antiemetic efficacy and side effects using SPSS 21 statistical software. Results: 120 patients with minor head trauma were distributed and studied into two groups of 60 patients (mean age 35.6±14.1 years; 50.0% male). Administration of both ondansetron and metoclopramide significantly reduced the severity of nausea (P&lt;0.001). Changes in the severity of nausea in both groups before and after the treatment revealed that nausea had been decreased significantly in both groups (P &lt; 0.001). The incidence of fatigue (p=0.44), headache (p=0.58) and dystonia (p=0.06) had no significant difference in the two groups but the incidence of drowsiness and anxiety in the metoclopramide group was significantly higher (P &lt; 0.001). Conclusion: The present study indicated that the treatment effectiveness of ondansetron and metoclopramide are similar. However, incidence of drowsiness and anxiety in the metoclopramide was considerably higher. Since these complications can have adverse effects on the treatment of patients with brain injury, it is suggested that it may be better to use ondansetron in these patients

Vibration condition monitoring of planetary gears based on decision level data fusion using Dempster-Shafer theory of evidence

In recent years, due to increasing requirement for reliability of industrial machines, fault diagnosis using data fusion methods has become widely applied. To recognize crucial faults of mechanical systems with high confidence, indubitably decision level fusion techniques are the foremost procedure among other data fusion methods. Therefore, in this paper in order to improve the fault diagnosis accuracy of planetary gearbox, we proposed a representative data fusion approach which exploits Support Vector Machine (SVM) and Artificial Neural Network (ANN) classifiers and Dempster-Shafer (D-S) evidence theory for classifier fusion. We assumed the SVM and ANN classifiers as fault diagnosis subsystems as well. Then output values of the subsystems were regarded as input values of decision fusion level module. First, vibration signals of a planetary gearbox were captured for four different conditions of gear. Obtained signals were transmitted from time domain to time-frequency domain using wavelet transform. In next step, some statistical features of time-frequency domain signals were extracted which were used as classifiers input. The gained results of every fault diagnosis subsystem were considered as basic probability assignment (BPA) of D-S evidence theory. Classification accuracy for the SVM and ANN subsystems was determined as 80.5 % and 74.6 % respectively. Then, by using the D-S theory rules for classifier fusion, ultimate fault diagnosis accuracy was gained as 94.8 %. Results show that proposed method for vibration condition monitoring of planetary gearbox based on D-S theory provided a much better accuracy. Furthermore, an increase of more than 14 % accuracy demonstrates the strength of D-S theory method in decision fusion level fault diagnosis

Nondestructive evaluation of welding residual stresses in dissimilar welded pipes

This paper investigates the nondestructive capability of ultrasonic waves in residual stress evaluation of dissimilar welded pipes. Longitudinal critically refracted (L CR ) waves are employed to measure the residual stresses in a pipe-pipe joint of stainless steel 304 and carbon steel A106. Measuring the acoustoelastic constant is usually accomplished through the tensile test which needs cutting the tested material to extract tensile test specimens. However, cutting the tested pipe to complement the nondestructive ultrasonic measurement was not considered here. Instead, a dissimilar welded plate with the same welding specification, joint geometry, thickness and the same dissimilar materials is used to extract tensile test samples. The measured acoustoelastic constant of the plate along with the measured time of flight of the L CR wave on the pipe, are utilized for ultrasonic stress measurement. A finite element model of welding process validated by hole-drilling method is used to verify the ultrasonic results. The results show good agreement between finite element and ultrasonic measurements in the pipe measured without any destructive process

The role of intergenerational family in family functions and cultural values in Aligudarz, Iran in 2022

Background: Based on diversified intergenerational living in urban Iran, this study was conducted to determine the role of intergenerational family in family functions and cultural values in Aligudarz. Methods: This study was analytical cross-sectional based on questionnaire. The population were included over 18 years of age in Aligudarz, 376 people were selected as a sample using Cochran sampling by simple random sampling method. Library and survey methods were used to collect data. One-way analysis of variance and Pearson correlation tests were used to test the hypotheses. Results: Elderly people have better family functions than others (P=0.011) and adhere more to cultural values. Elderly people have more management in family crises with f value of 3.140 (p=0.019). The correlation coefficient between family cohesion and family functions is 0.152 with a direct correlation (P=0.003). As the level of family cohesion increases, family functions also increase. There is a direct correlation between kinship relations and family functions (P=0.777, -0.015). There is no relationship between the level of kinship and family functioning. Conclusion: It is possible to improve the current status given the level of adherence to cultural values, crisis management, and family cohesion, Kinship relationships among different generations, and the relationship between the variables of adherence to cultural values, crisis management and cohesion, and family functions