Application of the Finite Element Method to Solve Coupled Multiphysics Problems for Subsurface Energy Extraction

Fractures are a source of extra compliance in the rock mass. Fracture compliance can estimate the fracture roughness and the type of fluid filling the fracture. The focus of this research study in chapter 2 is to illustrate how the compliance ratio of rough fractures can diverge from the compliance ratio of smooth fractures. The imperfect interface of the fracture is modeled with saw-tooth-like structures. The defined saw-tooth-like structures of contact asperities impose an in-plane asymmetry in the shear direction. The compliance ratio of the rough fracture is larger than the compliance ratio of the smooth fracture. Interlocking and riding up effects may explain our findings in chapter 2. Recovered core samples and extensive outcrops studies have proved the existence of natural fractures in many tight formations. These natural fractures are likely filled with digenetic materials such as clays, quartz or calcite. In chapter 3, this study suggests that small cemented natural fractures can be opened by the induced tensile stress due to the temperature difference between the cold fracturing fluid and hot formation. Cohesive zone model (CZM) is utilized here to simulate these natural fractures. Contribution of these micro natural fractures to cumulative gas production from a shale reservoir is investigated by modifying the transmissibility coefficient. Reservoir simulation results in chapter 3 suggest that reactivated natural fractures in the tight formations at early stages can improve gas production up to 25\%; however, their effect significantly reduces to 3\% in long term. Geothermal systems are identified as either open-loop systems (OLGS) or closed-loop systems (CLGS). The loss of working fluid, surface subsidence, formation compaction, and induced seismicity are major challenges in OLGS. To address the indicated challenges, CLGS can be considered as an alternative option. To improve the heat extraction from closed-loop wells, this research study in chapter 4 suggests highly conductive hydraulic fractures for CLGS to improve heat extraction rate. The results suggest that fractures significantly improve thermal power and cumulative extracted heat in CLGS. Thermal conductivity of the proppants is the key parameter enhancing heat extraction

Prediction of Thermo-Physical Properties of TiO2-Al2O3/Water Nanoparticles by Using Artificial Neural Network

In this paper, an artificial neural network is implemented for the sake of predicting the thermal conductivity ratio of TiO2-Al2O3/water nanofluid. TiO2-Al2O3/water in the role of an innovative type of nanofluid was synthesized by the sol–gel method. The results indicated that 1.5 vol.% of nanofluids enhanced the thermal conductivity by up to 25%. It was shown that the heat transfer coefficient was linearly augmented with increasing nanoparticle concentration, but its variation with temperature was nonlinear. It should be noted that the increase in concentration may cause the particles to agglomerate, and then the thermal conductivity is reduced. The increase in temperature also increases the thermal conductivity, due to an increase in the Brownian motion and collision of particles. In this research, for the sake of predicting the thermal conductivity of TiO2-Al2O3/water nanofluid based on volumetric concentration and temperature functions, an artificial neural network is implemented. In this way, for predicting thermal conductivity, SOM (self-organizing map) and BP-LM (Back Propagation-Levenberq-Marquardt) algorithms were used. Based on the results obtained, these algorithms can be considered as an exceptional tool for predicting thermal conductivity. Additionally, the correlation coefficient values were equal to 0.938 and 0.98 when implementing the SOM and BP-LM algorithms, respectively, which is highly acceptable. View Full-Tex

PSO BASED TAKAGI-SUGENO FUZZY PID CONTROLLER DESIGN FOR SPEED CONTROL OF PERMANENT MAGNET SYNCHRONOUS MOTOR

A permanent magnet synchronous motor (PMSM) is one kind of popular motor. They are utilized in industrial applications because their abilities included operation at a constant speed, no need for an excitation current, no rotor losses, and small size. In the following paper, a fuzzy evolutionary algorithm is combined with a proportional-integral-derivative (PID) controller to control the speed of a PMSM. In this structure, to overcome the PMSM challenges, including nonlinear nature, cross-coupling, air gap flux, and cogging torque in operation, a Takagi-Sugeno fuzzy logic-PID (TSFL-PID) controller is designed. Additionally, the particle swarm optimization (PSO) algorithm is developed to optimize the membership functions' parameters and rule bases of the fuzzy logic PID controller. For evaluating the proposed controller's performance, the genetic algorithm (GA), as another evolutionary algorithm, is incorporated into the fuzzy PID controller. The results of the speed control of PMSM are compared. The obtained results demonstrate that although both controllers have excellent performance; however, the PSO based TSFL-PID controller indicates more superiority

Down Regulation of Osteocalcin Gene in Chickens Treated with Cadmium

Background: Cadmium is one of the heavy metals with harmful effects on different body organs and systems. The aim of this study was to investigate the harmful effects of cadmium, as a heavy metal, on the histological structure of bone and the expression of osteocalcin gene. Methods: Forty chickens were obtained, anesthetized and their femurs were surgically removed. The real time polymerase chain reaction (PCR) was used to study the osteocalcin gene expression. Results: The osteocalcin gene expression rate were: 1.000± 0.1; 0.86± 0.01; 0.63± 0.09, and 0.41± 0.06 in the controls, experiment I, experiment II and experiment III groups, respectively (P < 0.05). Also, the nuclear pyknosis in osteocytes and decreased bone formation were observed in the histology slides of the chicken bones. Conclusions: We conclude that cadmium adversely affected the chicken bones as evident by the decreased osteocalcin gene expression and the adverse effects on the bone histology. We recommend that plans be developed to prevent the outbreak of cadmium and other heavy metals in animal and human environment

The prevalence of iron deficiency anemia during pregnancy in Iran (1991-2015): A systematic review and meta-analysis

Introduction: The prevalence of Iran Deficiency Anemia (IDA) in pregnant women is in Variable between 40-80 in developing countries. There are some differences among different studies on this disorder. So, this present study is been performed for evaluating the prevalence of IDA among pregnant Iranians with systematic review and Meta analysis method. Method: This study is based on received information achieved from Magiran, , Iran medex, SID, Med lib, IranDoc, Scopus, Pubmed, SceinceDirect, Cochrane, Embase, Medline, Springer, Online Library Wiley and Google Scholar in chronological order of 1 January 1991 to 31 march 2015 with using standard key words. Search and extraction of data were done by two independed reviewers. To pooled of results of studies random effects model in meta-analysis was used. Results: In the 32 eligible studies, the 63372 individuals were been evaluated. The prevalence of Anemia among pregnant Iranians was estimated 14.2 (95 CI: 12- 16.3). most prevalence of Anemia was seen in the study, which it is used the samples collected in several parts of country, (21.5) and the lowest prevalence was seen in the West of country(7). The prevalence of Anemia in urban and rural pregnant women was estimated 13.7 and 20 approximately, respectively. Conclusion: The prevalence of anemia among pregnant Iranians in current 24 years were less according to WHO system report for developing countries, that it is related to appropriate plan and care in pregnancy period in countries

Experimental investigation on energy absorption of auxetic structures

The human being has always been looking for optimal use of his surrounding materials and over the years, has managed to invent various structures with special properties. Lattice structures are widely used in various applications due to their lower weight and desirable compressive strength. An example of these structures is the honeycomb that is very popular and many studies have been done about it. A new type of lattice structures is auxetic structure that has negative Poisson’s ratio due to its geometry. This characteristic has caused auxetic structures to have unique properties such as high shear strength, indentation resistance and energy absorption. Investigation of energy absorption of auxetic structures is a subject that has not been studied in researches. In this study, the ability of some auxetic structure for absorbing energy is investigated at quasi-static and low velocity impact transverse loading. Specimens with three types of geometries (re-entrant, arrowhead and anti-tetra chiral) are fabricated using additive manufacturing method (3D printing). Discussion about energy absorption and failure mechanisms of all three structures were carried out and compared in both types of loading

Relationship between organizational intelligence and performance indicators of teaching hospitals: a case study in Iran

Background: One of the greatest managerial challenges is how to generate  intelligent organizations that can quickly adopt themselves according to environmental changes to guarantee their success and survival in a turbulent external environment.Objectives: Study objective was to assess the relationship between organizational intelligence and performance indicators of teaching hospitals affiliated by Shahid Sadoughi University of Medical Sciences (YUMS) in 2015.Design: This was a descriptive, cross-sectional study conducted in three teaching hospitals affiliated by YUMS in 2015. Data were collected using a standard questionnaire developed by Albrecht and analyzed by SPSS 16 using descriptive and correlation statistical tests.Setting of the study: Hospitals affiliated by Shahid Sadoughi University of Medical Sciences in Yazd, Iran.Subjects/ participants: A sample of 300 personnel working in under study hospitals who’ve been selected through stratified random sampling method.Results: Results confirmed that scores of organizational intelligence in understudy hospitals were in the optimum status. Conditions of three performance indicators including average length of stay, bed turnover and bed occupancy rate were analyzed to be appropriate. A significant statistical correlation between organizational intelligence and bed occupancy rate, total number of admitted and discharged patients and finally number of patients’ death was seen (p&lt;0.05).Conclusion: Having an appropriate plan or decision strategies to strengthen organizational intelligence can play an effective role in hospital performance improvement

Statistical and Numerical Study of Chipping and Cracking in Segmental Lining

Some of the most frequent damages of concrete segments in shield tunnels are chipping and cracking, which are followed by degradation of lining system. In this paper, these types of damages are studied in four subway and two water conveyance tunnels. More than 2100 concrete rings are examined for chipping inspection and another 3000 for determination of the cracking. Statistical analysis of the research data showed that corners of the key and counter-key segments carry the highest number of chipping, while most of the cracking occur in the middle zones and shape of the segments and number of trust jacks affect the cracking pattern. Two kinds of numerical models are used to examine the underlying damages, which are based on geometrical characteristics of tunnel lining and boring machine besides operational mistakes. Findings of the numerical simulation revealed that installation of segmental lining with the least amount of erection tolerances results in low amount of chipping, this is while using key-segments with 12–17 degrees of insertion angle reduces total magnitude of damage due to tensile and compressive stresses. Furthermore, the deviation angle of TBM’s jack and segment’s axis should never be more than 5 degrees; otherwise even high-quality concrete segments wouldn’t remain undamaged. Employment of boring machines with articulated system is proposed in this case