Sand production simulation under true-triaxial stress conditions

Sand production in weakly consolidated sandstone reservoirs could result in damaging the production and surface facilities. Sanding includes two stages: the failure of sandstone around the borehole and sand grains being transported into the borehole. The first stage is related to stresses around the borehole whereas the second one is controlled by drawdown pressure. In order to avoid sanding, the stresses around the borehole and the drawdown pressure which initiate sanding are studied.This research simulated sand production through laboratory experiments and numerical simulations. The effect of three independent far-field stresses was investigated which is contrary to most of the current studies being performed under a uniaxial or triaxial stress state. Accordingly, a unique experimental setup and procedure was introduced to conduct sand production experiments under true-triaxial stress conditions. The effect of drawdown pressure and state of far-field stresses on the sanding mechanism and development of the failure zone around a borehole were investigated. The experiments were conducted on 100×100×100 mm3 cubic samples of synthetic sandstones. The samples were manufactured using an established procedure developed to produce samples with properties similar to weakly consolidated sandstone. The properties of the synthetic sandstone samples were determined by conducting a series of standard rock mechanics tests on cylindrical plugs. Using a true-triaxial stress cell (TTSC), cubic samples were subjected to three independent boundary stresses and uniform lateral fluid flow from the outer boundaries. The fluid flows through the sample radially and discharges from a hole drilled at the centre of the sample: this allows the study of sanding initiation by changing the state of stress, sample material and fluid properties.In this research, firstly, the concept of sand production from a geomechanics point of view and a summary of previous sanding experiments are explained. Thereafter, the procedure to prepare a sample suitable for sand production experiments is provided. Subsequently, the experimental equipment, setup and procedure are explained in detail. This is followed by presenting the results of two sets of experiments performed at different states of stress. The effect of changing the lateral stresses on the development of the failure zone around borehole was investigated in these experiments. During these experiments it was observed that a minimum drawdown pressure is needed to initiate sand production, regardless of the state of the boundary stresses. In addition, it was observed that the geometry (i.e. width and depth) of the failure zone developed around the borehole is a function of the state of stresses.The experiments were also simulated numerically using ABAQUS in order to gain a better understanding of sand production mechanisms. The numerical modelling procedure and results are presented in a separate section in this thesis. Good agreement was obtained between the results of both experimental and numerical methods which confirm the importance of the state of stresses on the evolution of sanding. Based on the experimental and numerical observations, it was shown that the effect of the magnitude of the maximum lateral stress on the depth of failure is more significant than the minimum lateral stress

Effects of an adapted physical activity program in a group of elderly subjects with flexed posture: clinical and instrumental assessment

<p>Abstract</p> <p>Background</p> <p>Flexed posture commonly increases with age and is related to musculoskeletal impairment and reduced physical performance. The purpose of this clinical study was to systematically compare the effects of a physical activity program that specifically address the flexed posture that marks a certain percentage of elderly individuals with a non specific exercise program for 3 months.</p> <p>Methods</p> <p>Participants were randomly divided into two groups: one followed an Adapted Physical Activity program for flexed posture and the other one completed a non-specific physical activity protocol for the elderly. A multidimensional clinical assessment was performed at baseline and at 3 months including anthropometric data, clinical profile, measures of musculoskeletal impairment and disability. The instrumental assessment of posture was realized using a stereophotogrammetric system and a specific biomechanical model designed to describe the reciprocal position of the body segments on the sagittal plane in a upright posture.</p> <p>Results</p> <p>The Adapted Physical Activity program determined a significant improvement in several key parameters of the multidimensional assessment in comparison to the non-specific protocol: decreased occiput-to-wall distance, greater lower limb range of motion, better flexibility of pectoralis, hamstrings and hip flexor muscles, increased spine extensor muscles strength. Stereophotogrammetric analysis confirmed a reduced protrusion of the head and revealed a reduction in compensative postural adaptations to flexed posture characterized by knee flexion and ankle dorsiflexion in the participants of the specific program.</p> <p>Conclusion</p> <p>The Adapted Physical Activity program for flexed posture significantly improved postural alignment and musculoskeletal impairment of the elderly. The stereophotogrammetric evaluation of posture was useful to measure the global postural alignment and especially to analyse the possible compensatory strategies at lower limbs in flexed posture.</p

Numerical Modeling of Methane Decomposition for Hydrogen Production in a Fluidized Bed Reactor

The decomposition of methane for hydrogen production is an attractive alternative to the established method of reforming. This process considerably reduces the emission of greenhouse gases, and its overall efficiency and cost are competitive. The decomposition of methane is performed with a catalyst to produce a substantial amount of hydrogen, and decrease the operating temperature. Between different catalysts available, carbon is selected in this study due to its low rate of decay and advantages such as low cost and availability. Also, a fluidized bed reactor operating in the particulate regime is employed due to the efficient contact between the catalyst and the gas. Consequently, hydrogen production from the thermocatalytic decomposition of methane in a particulate fluidized bed reactor of carbon particles is investigated. To obtain an appropriate design and operation for this process, the effect of different operating parameters and catalyst properties should be investigated on the performance. This aim can be achieved by modeling. A number of models with different complexities have been proposed for this process. Considering the objective of this thesis, a complex kinetic model is required to represent the effect of the catalyst properties. In literature, the kinetics is generally modeled with a global equation using experimental parameters. Since investigation on the effect of the properties of the catalyst is not feasible with this method, the detailed kinetic model with a surface reaction mechanism is employed in this study. Investigation on this surface mechanism is very limited, and only one of the models available in literature is determined to be appropriate. Nevertheless, this model has some important drawbacks. The major problem is that the specific surface area is considered as the only catalyst property affecting the activity of carbon. Experimental studies suggest that the activity of this catalyst is a function of its specific surface area and number of active sites, and neglecting either of these properties can lead to a high inaccuracy. Consequently, a new kinetic model is developed where a modified form of the available mechanism is used, and the number of active sites and the specific surface area of the catalyst are considered in the rate equations. It is noted that although several experimental investigations have been performed on the origin of the active sites, their quantity has not been acceptably determined yet. A method is presented in this study to estimate the number of active sites with the developed model and experimental data. To the best knowledge of the author, this is the first model to incorporate the effect of this parameter for carbon catalysts in the decomposition of methane and quantify its value. Another important problem of the model available in literature is its dependency on experimental measurements for determining the hydrodynamic characteristics of the fluidized bed. In this study, the hydrodynamics of the reactor is modeled with empirical correlations to obtain a complete representation of the process within the required accuracy, with minimal experimental requirements. The model is used to investigate the effect of different operating parameters and catalyst properties on the amount of the initial methane conversion. The operating parameters studied are the temperature, residence time, gas velocity, and composition of the feed gas. The catalyst properties considered are the particle size and pore volume, the number of active sites, and the percentage of fine particles in the bed. The effect of the variations of each of these factors in a certain range is investigated for a fluidized bed reactor operating at the onset of fluidization at nominal condition. The onset of fluidization is maintained by changing the inlet flow rate in a reactor of a specific size. The results show that, considering the range of variations in this study, the procedures that cause the highest improvement in conversion are: increasing the residence time, decreasing the size of particles, adding fine particles to the bed, increasing the temperature, using catalysts with high surface areas or large number of active sites, changing the inlet gas composition, and using catalysts with large pore volumes, respectively. It is noted that all of these improvements are associated with higher initial or operating costs. Therefore, changing each of these factors beyond a certain value is faced with economic and technical barriers. Consequently, the possibility and efficiency of using two factors simultaneously for achieving higher conversions was also investigated. The results can be used as a guideline to choose between several catalysts considering their characteristics, or to suggest appropriate operating conditions.1 yea

Effects of Thiobacillus, Sulfur and Micronutrient Spray on Some Traits of Green Beans

A factorial experiment with the split plot arrangement using the complete randomized block design with three replications was carried out adjacent to the Agriculture School of Shahrood University of Technology in 2010-2011 to study the effects of sulfur and Thiobacillus application and zinc and molybdenum sprays on some traits of green beans. The treatments included three levels of sulfur (zero, 100 kg/ha of sulfur powder, and 100 kg/ha of sulfur powder + Thiobacillus bacteria) as the main factor, and three levels of zinc spray (0, 5, and 10g/l) and two levels of molybdenum spray (0 and 0.5 g/l) as the sub-main factors. The treatments that included sulfur were applied before seeding. Zinc (using zinc sulfate) and molybdenum (using sodium molybdate) were sprayed during the growing season and 5 weeks after planting. Results showed the treatment of applying sulfur at 100 kg/hectare and Thiobacillus bacteria increased leaf fresh and dry weights by 57 and 54%, mean pod length by 14%, and number of lateral branches by 25% compared to the control. Moreover, this treatment increased pod fresh and dry weights by 41.6 and 42.11%, respectively, compared to the treatment of not applying sulfur, and improved yield by 42% compared to the control. Considering the results concerning yield in response to sulfur, zinc, and molybdenum, it can be said that application of sulfur and Thiobacillus together with zinc spray can be very useful in growing green beans

Response of Agronomic and Phenological Characteristics of Bread Wheat (Triticum aestivum L.) Cultivars with Different Growth Habit to Delayed Planting

IntroductionWheat (Triticum aestivum L.) is one of the most important crops in the world as well as in Iran. It has experienced many improvements in terms of yield and quality traits during recent decades. Wheat, like energy, is known as a strategic commodity and is one of the important indicators of agriculture. This plant has the highest area under cultivation and production among other cereals in the world. Planting date is an important factor in crop production because meteorological parameters vary with changes in planting date. Delay in planting is one of the problems that is common in almost all wheat growing areas of Iran and is one of the main causes of reduced yields of wheat cultivars. Yield reduction rate varies depending on the delay in planting and cultivars, and the results of some experiments indicate that this amount sometimes reaches more than 35% of potential grain yield. Phenology and growth rate due to their effect on duration and the occurrence of different stages of development and the environmental conditions prevailing in each of these stages, are the key point of adaptation to various environmental conditions such as delayed planting date. This experiment was designed to identify the changes in yield and yield components and phenological stages of new bread wheat cultivars with different growth habits and to investigate the possibility of introducing cultivars compatible with delayed planting date in the region.Materials and MethodsThis research was conducted in two separate experiments based on a complete randomized block design with optimum planting date (6th November) and delayed planting date (6th December) on 10 new bread wheat cultivars with three replications on the research farm of the Seed and Plant Improvement Research Institute in Karaj in two years (2016-2018). The bread wheat cultivars include Pishgam, Heidari, Rakhshan, Sivand, Baharan, Sirvan, Parsi, Mehregan, Chamran 2 and Chamran. Yield and yield components such as number spike per m2, number of grain per spike, 1000-grain weight were measured at the end of the growing season to evaluate responses of the cultivars to the various planting dates. In addition, the phenological stage was recorded during the growing season.Results and DiscussionResults indicated that delayed planting date from 15th Nov. to 15th Dec. caused a significant reduction on grain yield (from 7485 to 6066 kg.ha-1), number of spikes per m2 (from 698 to 605), number of grain per spike (from 28.5 to 25.8 seed), and 1000 grain weight (from 41.1 to 38.4 g). The interaction effects of planting date and cultivars were significant on grain yield and yield components. The highest and lowest grain yield belonged to Pishgam (7436 kg. ha-1) on optimum planting date and Chamran (5842 kg.ha-1) on delayed planting date, respectively. Delayed planting date reduced duration of planting to double ridge (from 736 to 641 GDD), planting to terminal spikelet (from 982 to 886 GDD), planting to anthesis (from 1608 to 1457 GDD) and planting to maturity (from 2456 to 2265 GDD).ConclusionDuration of different developmental stage is very important for the formation of yield components that determine the final grain yield. Although these stages are a genetic trait, but they are affected by plant growth conditions and environmental stresses, climatic factors, especially temperature and day length. Our research showed that delay in planting reduced grain yield by 18% compared to the optimum planting date because of the reduced number of spikes per m2 and vegetative and grain-filling periods.Based on the results, in cases of delayed planting date (unfavorable weather conditions, insufficient planting equipment, etc.) in Karaj region or similar climatic regions, early maturity cultivars such as Mehregan and Chamran 2 and moderate maturity cultivar like Sivand are recommended in order to minimize yield loss

Maximum Sauter Mean Diameter and Terminal Velocity of Drops in a Liquid-liquid Spray Extraction Column

The effect of holdup on Sauter mean drop diameter, d32 and the effect of d32 on terminal velocity have been investigated in a spray extraction column. There are two different zones for the dependence of d32 on holdup. d32 increased with an increase in holdup at low holdup levels and decreased with increasing holdup at high holdup levels. Variations in the terminal velocity of drops were similar to the dependence of d32 on holdup. Furthermore, empirical correlations have been derived to predict d32max and terminal velocity and were in a good agreement with the experimental data. The derived correlations were compared with other researchers work and the results were in a satisfactory conformity

Effects of organic fertilizers and drought stress on Physiological traits in barley

Abstract Stress the most important factor limiting agricultural production in arid and semi-arid systems is considered. Distribution of rainfall in these areas (arid semi-arid), sometimes not consistent with crop needs and develop products that are temporary or prolonged drought. To study the effects of spray irrigation on winter barley trial at year 2011 in the field region of Damghan. These Split plot experiment in randomized complete block design with three replications. ) was. Rates Protein affected foliar Humax + Biomin both normal irrigation and water deficit stress conditions (41BBCH) solution were (11.42% and 11.53%) most of the proteins themselves. The study found that proline Nusrat victory both in normal irrigation and deficit stress conditions (41BBCH) , without spray (control) solution were (63.03 μmol/g and 80.33 μmol/g) more proline compared to other treatments showed. Farmers to increase their performance today acre foliar spray methods are used for fertilization. Foliar spray of plant response to fertilizer is fast methods. This approach makes the environment by fertilizing it in order to achieve sustainable agriculture is also very helpful. It was found that the variety kavir of normal watering with foliar Humax + Biomin potassium levels showed more than other treatments. The different effects on different plants using soil dry organic fertilizer such as Humax and Biomin can be drought resistant plants to rise

A Comparison of Metoclopramide and Ondansetron Efficacy for the Prevention of Nausea and Vomiting In Patients Suffered From Renal Colic

BACKGROUND: Renal stones are the third common disease of the urinary system after infections and diseases of the prostate. One of the most common manifestations of this disease after acute pain is nausea and vomiting. AIM: To compare the efficacy of metoclopramide and ondansetron in improving nausea and vomiting in patients referred to the emergency department with a chief complaint of nausea and vomiting. METHODS: This randomised double-blind clinical trial was conducted on patients referred to the emergency department of Vali-e Asr Hospital. Mg5 intravenous morphine and ketorolac ampoule were injected to control renal colic. Then, patients were randomly divided into two groups. Group 1 consisted of 90 subjects receiving 10 mg intravenous metoclopramide and group 2 including 90 subjects receiving 4 mg intravenous ondansetron. Vital signs were also measured and recorded. RESULTS: The mean and standard deviation of nausea in 0, 15, 30, 45, 60 and 120 minutes showed no significant difference between the two groups. Mean and standard deviation of vomiting at 0 minutes showed no significant difference between the two groups, but the remaining minutes, 15, 30, 45, 60 and 120, exhibited significant difference as a comparison of two groups, indicating that vomiting in the metoclopramide group was higher than ondansetron group. CONCLUSION: Our findings indicated that ondansetron was more effective than metoclopramide in preventing and improving vomiting in patients referred to emergency renal colic, where can be used with more efficacy and more acceptable side effects to improve nausea and vomiting