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Fatigue crack propagation is an important consideration in evaluating the design life of engineering components, especially in the energy and transport industries. Despite its importance, fatigue analyses are not usually supported by commercial Finite Element (FE) codes; in fact, most FE codes require the addition of costly plug-ins to perform fatigue crack growth simulations. Therefore, this paper introduces a new, freely distributed plug-in to simulate fatigue crack growth with the commercial FE code Abaqus. The plug-in includes five different fatigue crack growth models and relies on the extended FE method to simulate crack propagation. The plug-in is limited to 2D analyses, but covers all necessary steps for fatigue crack growth simulations, from creating the geometry to job submission and post-processing. The implementation of the plug-in is validated by comparing its predictions to analytical and experimental results. Finally, we hope that the simplicity of the plug-in and the fact that it is distributed freely will make it a useful simulation tool for industrial, research and educational purposes.

One of the cleanest and most accessible energy sources is solar energy. However, finding efficient ways to receive this energy source and convert it to electrical power for different applications is still a challenging problem. A parabolic trough solar collector (PTSC) is a type of concentrating solar technology which can be employed for producing electricity and heating simultaneously, which is one of the efficient techniques to produce electrical power from solar energy. After several decades of research, development, and construction of different types of PTSCs, the most recent studies focus on improving the efficiencies of these systems, both from structural/material (solid mechanics) and heat transfer (fluid mechanics) aspects. Improving the PTSC performance has led to enhancement in the electrical energy production. From a heat transfer point of view, there have been many approaches proposed to reach a better efficiency for the PTSC system, such as nanofluids, internal flow inserts, and an external magnetic field acting on the magnetic nanofluid. This chapter discusses PTSCs with detailed explanations on the corresponding heat transfer formulations, and at the end, a numerical example is being analyzed using the ANSYS FLUENT software.

Ovarian Cancer (OC), as the seventh most common cancer throughout the world, is one of the most lethal gynecologic malignancies in women. In addition to well-studied risk and prognostic factors of OC, such as age, obesity, stage, histology, etc., ABO blood groups associations with OC has been attracted the investigators’ focus in the recent decade. The objective of this study is to find any relationships between ABO blood groups and OC through a meta-analysis. The databases of PubMed, Embase, and Web of Science were systematically searched by available MeSh terms for “Ovarian Cancer”, and “ABO blood group” up to August 1, 2020. Hazard ratio (HR) or odds ratio (OR) were extracted and used from studies for outcome estimation whenever appropriate with 95% confident interval (CI). Data were analyzed using CMA v. 2.2.064. Fourteen papers, including 58,193 participants, entered in the systematic review. The meta-analysis indicated a substantially higher risk of developing OC in individuals with blood group A (OR 1.17, 95% CI 1.01–1.36) and AB (OR 1.27, 95% CI 1.02–1.59), but the subject was not significant in individuals with blood group B (OR 1.11, 95% CI 0.81–1.51). No associations were found between OC overall survival and blood group A (HR 1.14, 95% CI 0.79–1.64), AB (HR 1.00, 95% CI 0.69–1.45), and B (HR 0.88, 95% CI 0.58–1.33). Recurrence rates of OC for blood groups A, AB, B, and O were 30.8%, 34.3%, 33.6%, and 32.0%, respectively. Rates of mortality in different blood groups are as follows: A (31.8%), AB (31.1%), B (26.2%), and O (33.8%). This systematic review and meta-analysis revealed a considerably increased risk of developing OC among individuals with blood group A and AB. However, no substantial impacts were found for ABO blood groups on the overall survival of the OC patients.

Generally, the majority of the linear concentrating photovoltaic (LCPV) systems incorporated with active cooling systems use liquid water pump loop or conventional vapor compression refrigeration system. In this study, a new cooling system, so-called two-phase mechanical pumped loop (TMPL), is proposed to be used with LCPV system. The excess heat from photovoltaic (PV) cell is used to heat up water stored in a tank for residential purposes. The case study is Bogota in Colombia and we develop a dynamic simulation model for the LCPV-TMPL system. The design parameters of the TMPL system are the flow volumetric rate and saturation temperature of the refrigerant as well as the tube length of the condenser. Moreover, low global warming potential (GWP) refrigerants such as R1234yf and R1234ze(E) were evaluated, both showing the same performance compared to R134a. The results showed that the use of TMPL system to eliminate the generated heat of PV cell improves its temperature stability and efficiency. It also shows how the proposed model can be used to design the thermal/photovoltaic system for a local, showing also the expected performance before the system installation. In the case study region, the LCPV-TMPL system, using four PV cells with 5 m × 10 mm, produces power with an average monthly of 2 kW with a peak of 5 kW under average and peak monthly solar radiation of 400 W/m2 and 600 W/m2, respectively. The storage tank can heat up 2.2 m³ water per day from 8 °C to approximately 28 °C, in an average sense. This means that the LCPV-TMPL system could save 9000 kWh and 1900 kWh per year in electricity and thermal energies (water heating). This system can be used locally with low or medium solar radiation and cold weather.

BackgroundEvidence recommends that vitamin D might be a crucial supportive agent for the immune system, mainly in cytokine response regulation against COVID-19. Hence, we carried out a systematic review and meta-analysis in order to maximize the use of everything that exists about the role of vitamin D in the COVID-19.MethodsA systematic search was performed in PubMed, Scopus, Embase, and Web of Science up to December 18, 2020. Studies focused on the role of vitamin D in confirmed COVID-19 patients were entered into the systematic review.ResultsTwenty-three studies containing 11901participants entered into the meta-analysis. The meta-analysis indicated that 41% of COVID-19 patients were suffering from vitamin D deficiency (95% CI, 29%-55%), and in 42% of patients, levels of vitamin D were insufficient (95% CI, 24%-63%). The serum 25-hydroxyvitamin D concentration was 20.3 ng/mL among all COVID-19 patients (95% CI, 12.1-19.8). The odds of getting infected with SARS-CoV-2 is 3.3 times higher among individuals with vitamin D deficiency (95% CI, 2.5-4.3). The chance of developing severe COVID-19 is about five times higher in patients with vitamin D deficiency (OR: 5.1, 95% CI, 2.6-10.3). There is no significant association between vitamin D status and higher mortality rates (OR: 1.6, 95% CI, 0.5-4.4).ConclusionThis study found that most of the COVID-19 patients were suffering from vitamin D deficiency/insufficiency. Also, there is about three times higher chance of getting infected with SARS-CoV-2 among vitamin D deficient individuals and about 5 times higher probability of developing the severe disease in vitamin D deficient patients. Vitamin D deficiency showed no significant association with mortality rates in this population.

Introduction:The outbreak of new coronavirus has become a global public health challenge. Given a consequential liver function, and the high risk of death coming from liver disorders, the assessment of Novel Coronavirus Disease on liver function is importance. Hence, we carried out this meta-analysis to heightening insight into the occult features of COVID 19, which is likely to affect liver function. Method:This study was performed using databases of Web of Science, Scopus, and PubMed. We considered English cross-sectional and case-series papers, which reported available findings on the association between liver injury and COVID-19 infection. We used the STATA v.11 and random effect model for data analysis. Result:In this present meta-analysis, 52 papers, including 8,463 COVID-19 patients, were studied. The prevalence of increased liver enzymes among the patients, including Alanine aminotransferase, Aspartate aminotransferase, were 30% and 21% in non-severe patients, respectively, which were 38% and 48% in severe patients. The prevalence of increasing C-reactive protein, Lactate dehydrogenase, D-dimer, and Bilirubin were 55%, 39%, 28%, and 10% in non-severe patients respectively, which were 78%, 75%, 79% and 17% in sever patients.The prevalence of liver toxicity as a complication of COVID-19 was 20%.Also patients who have severe condition are 5.54, 4.22, 4.96, 4.13 and 4.34 times more likely to have elevated CRP, ALT, AST, LDH, D-dimer enzymes retrospectively. Conclusion:Elevation of some liver markers were higher in patients with severe COVID-19 infection. All to gather, we assumed that abnormal liver markers could act as a prognostic factor for a better survey of COVID-19.

Ferrofluid is defined as a magnetic fluid which is composed of magnetic nanoparticles immersed in the base fluid such as water and oil. Nanofluids under magnetic field were proposed as a novel working fluid for industrial applications. In this study, the convective heat transfer of Fe3O4/water ferrofluid under constant magnetic field is evaluated. For this purpose, computational fluid dynamics (CFD) simulation and adaptive neuro-fuzzy inference system optimized with particle swarm optimization (ANFIS-PSO) are applied. To develop the ANFIS-PSO model, inlet temperature of ferrofluid, volume fraction of nanoparticle (Fe3O4), Reynolds number and intensity of magnetic field are considered as input variables of the model and heat transfer coefficient (HTC) of Fe3O4/water ferrofluid is considered to be the target. The results demonstrated that the developed ANFIS-PSO model can successfully predict the HTC of ferrofluid in laminar and turbulent flows in terms of the correlation coefficient (R), root mean square error (RMSE) and mean absolute percentage error (MAPE) respectively with 0.9992, 117.19 (W/m2K) and 2.44% for testing phase of the network. Also, CFD simulation and ANFIS-PSO model illustrated that the amount of the HTC of ferrofluid increases by increasing in intensity of magnetic field and inlet temperature of ferrofluid.

One of the main issues with the cylindrical tubes is the propagation of cracks during their operational life wherein most of the cracks happen along the axial direction of the tube. This paper reports a 3D finite element simulation of the mechanical responses of an aluminum tube containing a longitudinal crack repaired with composite patches . After several loading-unloading cycles of the dynamic load, mechanical stresses at the crack tips may result in unstable crack propagation . Therefore, it is necessary to use a repair process to prevent the structure from final rupture. Glass/epoxy and boron/epoxy composite patches, with different number of patch layers, are considered in the analysis of the composite material repair effect on the crack tips stress distribution, evaluating the possibilities of crack propagation and patch delamination onset. Numerical simulations were partially compared with literature results to verify the modeling procedure, while a parametric study on the patch thickness was performed to verify the repair effectiveness. In general, boron and longer (140 mm) repair patches presented better performance than glass and shorter (70 mm) patches. Although thinner patches (2 layers) do not present the required resistance, thicker patches (16 layers) may precipitate delamination onset and thus should be avoided.

This work presents an object-oriented implementation of the G/XFEM to model the crack nucleation and propagation in structures made of either linear or nonlinear materials. A discontinuous function along with the asymptotic crack-tip displacement fields are used to represent the crack without explicitly meshing its surfaces. Different approach are explained in detail that are used to capture the crack nucleation within the model and also determine the crack propagation path for various problems. Stress intensity factor and singularity of the localization tensor (which provides the classical strain localization condition) can be used to determine the crack propagation direction for linear elastic materials and nonlinear material models, respectively. For nonlinear material model, the cohesive forces acting on the crack plane are simulated in the enrichment process by incorporating a discrete constitutive model. Several algorithms and strategies have been implemented, within an object-oriented framework in Java, called INSANE. This implementation will be presented in detail by solving different two-dimensional problems, for both linear and nonlinear material models, in order to show the robustness and accuracy of the proposed method. The numerical results are compared with the reference solutions from the analytical, numerical or experimental results, where applicable.

Solar energy is among the cleanest and most adaptable compared to other renewable energy sources. The major challenge is how to get this energy in efficient way to make it available for industrial applications such as electricity generation. One of the most efficient techniques to harvest solar energy and transform it into electrical energy is parabolic trough solar collector (PTSC), which is a type of concentrating solar power generation system. This system operates by concentrating solar irradiance onto a tubular receiver in which this centralized energy is absorbed by a heat transfer fluid and transported to the power cycle. Improving the performance of the PTSC can enhance efficiency as well as power generation of a PTS power plant. Hence, this issue has been considered as one of the major challenges for scholars in this field. One promising solution is finding more efficient heat transfer working fluids. In recent years, ferrofluids due to their heat transfer characteristics are proposed as working fluids for engineering systems. In this research, Fe3O4/Therminol 66 and CuO/Therminol 66 nanofluids as working fluids for a PTSC are proposed and appraised. The repercussion of the magnetic field on the thermal efficiency of the collector is carried out using computational fluid dynamics (CFD). To improve the heat transfer characteristics of the collector, receiver is designed with internal fins. This assessment is done by considering the different nanoparticle sizes on the friction factor, thermal efficiency, performance evaluation criteria (PEC) and convective heat transfer. The results depict that reducing the particle size and enhancing the nanoparticles volume fraction increase the convective heat transfer coefficient, Nusselt number, PEC and the collector efficiency. In addition, the collector efficiency rises in the attendance of the magnetic field and maximum efficiency of the collector was obtained for 4% Fe3O4/Therminol 66 working fluid.

A ferrofluid is a magnetic fluid which is composed of magnetic nanoparticles with the size of 5-15nm immersed in a base fluid (such as water, oil, etc.). Although the amount of thermal conductivity of the magnetic nanoparticles is lower than that of metallic and metallic oxide nanoparticles, their constructability by magnetic field makes them ideal to be used in heat transfer applications. In this study, the heat transfer coefficient (HTC) of the Fe3O4 nanoparticles dispersed in water under constant and alternating magnetic field is investigated by artificial intelligence methods and CFD simulation. Multilayer feed-forward neural network, group method of data handling type neural network, support vector regression model and adaptive neuro-fuzzy inference system are developed to predict the HTC of the Fe3O4-water ferrofluid under magnetic field. Volume fraction of nanoparticle, intensity of the magnetic field, frequency of the magnetic field, Reynolds number and dimensionless distance of the tube are selected as input variables of the networks and the HTC is selected as output variable of the network. The results show that artificial intelligence methods can successfully predict the target with very good accuracy.

Thermo-mechanical shock wave in tube has many applications in aerospace/petroleum structures that brings up many challenges in repetitive, traveling, impulsive loading, and thermo-mechanical fatigue. The mechanical shock waves can cause oscillating strains in the tube wall, which can be several times higher than the equivalent static strains. The overall thermo-mechanical stresses after several loading–unloading processes in the engine may produce some discontinuities which may result in catastrophic fracture. In the current study, the resulting mechanical and thermal stresses have been assessed using numerical simulations. An axisymmetric finite element model of thermo-mechanical shock wave was developed using capabilities of commercial package ABAQUS for the preliminary analysis presented in this paper. Also, effects of different boundary condition types on tube wall response were investigated. The temperature field inside the engine was determined and presented in the form of a fixed value. In the numerical simulations, the mechanical and thermal displacements were computed separately and they are compared with available numerical and experimental results. Finally, the combined effects of mechanical and thermal stresses caused by thermo-mechanical shock wave have been simulated. The results of simulating coupled thermal stress showed that thermal shock caused by internal thermo-mechanical shock wave in tubes produces significant thermal stress.

This paper reports the analysis and simulation of the catastrophic failure of a compressed natural gas (CNG) fuel tank. The initial analyses of the deformation and cracking patterns, along with the observed fractographic features, were indicative of an internal gaseous combustion. Accordingly, a set of transient-dynamic elasto-plastic finite element (FE) analyses was carried out to simulate the structural response of the tank to a special type of combustion-induced dynamic pressure. The FE model was composed of 3D brick elements equipped with interface cohesive elements for crack growth analysis. Excellent agreements were found between the final simulation results and the observed deformation and fracture patterns. The simulation results clearly revealed that the observed failure characteristics, like the overall asymmetric deformation and fracture patterns, initiation and partial growth of parallel cracks at the same section, multiple cracking at the neck, and the self-similar growth of the main axial crack were all caused by traveling of a deflagration-induced sonic pressure wave from the neck towards the bottom of the tank. Finally, a comparison was made between the characteristics of deflagration-induced and detonation-induced deformation and fracture behaviors of closed-end cylinders.

Detonation-driven fracture problems in tube under dynamic load have received plenty of attention because of various ranges of applications, such as oil and gas pipeline systems, new rocket engine such as pulse detonation engine, and pressurized aircraft fuselages. This paper reports the crack growth modeling in a thin aluminum tube under gaseous detonation load. Because of three-dimensional fracture dynamics with gas dynamics coupled phenomena, analytical modeling is complicated. Thus, a finite element method was applied. The finite element modeling and simulation of the tube under detonation moving load were performed using commercial code Abaqus. This simulation leads to obtain structural response of the tube to detonation load. The simulations were compared with experimental and analytical results from the literature for elasto-dynamic response of cylindrical shells with finite length under internal detonation loading. Cohesive element with traction–separation law was used for crack growth modeling along with crack tip opening displacement value obtained from experimental–numerical analysis from previous research. The final section of the paper is dedicated to investigating differences and comparisons between the numerical crack propagation simulations and experimental results reported in the literature. It has been demonstrated that using cohesive elements with some modifications can improve the numerical accuracy. The obtained results are more similar to the experimental results than numerical results available in literature.