Levels Of Mechanical Stress Research Articles

Investigation of the Effect of High Shear Stress on Mesenchymal Stem Cells Using a Rotational Rheometer in a Small-Angle Cone-Plate Configuration.

Within the healthy human body, cells reside within the physiological environment of a tissue compound. Here, they are subject to constant low levels of mechanical stress that can influence the growth and differentiation of the cells. The liposuction of adipose tissue and the subsequent isolation of mesenchymal stem/stromal cells (MSCs), for example, are procedures that induce a high level of mechanical shear stress. As MSCs play a central role in tissue regeneration by migrating into regenerating areas and driving regeneration through proliferation and tissue-specific differentiation, they are increasingly used in therapeutic applications. Consequently, there is a strong interest in investigating the effects of shear stress on MSCs. In this study, we present a set-up for applying high shear rates to cells based on a rotational rheometer with a small-angle cone-plate configuration. This set-up was used to investigate the effect of various shear stresses on human adipose-derived MSCs in suspension. The results of the study show that the viability of the cells remained unaffected up to 18.38 Pa for an exposure time of 5 min. However, it was observed that intense shear stress damaged the cells, with longer treatment durations increasing the percentage of cell debris.

An experimental parametric analysis of the acoustic response in dielectric elastomer loudspeakers

This article presents an experimental parametric analysis of dielectric elastomer (DE) loudspeakers, which generate sound by means of soft lightweight electroactive polymer membranes, with no need for electromagnetic actuators. Attention is set on a simple topology, which consists of a DE actuator membrane deformed out-of-plane in a conical shape between fixed frames. Different scaled replicas of the system were built, featuring different diameters and elastomer membrane thickness, with the aim of highlighting the dependence of the acoustic response on the design parameters. An experimental analysis of the effect of different electrical and mechanical pre-loads was also carried out. Results suggest that the acoustic response is affected by both geometrical factors, possible effects of aero-elastic interactions, and the level of mechanical stress acting on the DE membrane. These findings provide valuable insights for the optimisation of DE loudspeaker design and operational parameters.

Blood flow restriction Exercise in the perioperative setting to Prevent loss of muscle mass in patients with pancreatic, biliary tract, and liver cancer: study protocol for the PREV-Ex randomized controlled trial

BackgroundPatients diagnosed with pancreatic, biliary tract, and liver cancer often suffer from a progressive loss of muscle mass. Given the considerable functional impairments in these patients, high musculoskeletal weight loads may not be well tolerated by all individuals. The use of blood-flow restricted resistance training (BFR-T) which only requires low training loads may allow for a faster recovery of muscle due to avoidance of high levels of mechanical muscle stress associated with high-load resistance exercise. This study aims to investigate whether BFR-T can prevent or slow down the loss of skeletal muscle mass and enhance the functional capacity and mental health of patients with pancreatic, biliary tract, and liver cancer.MethodsThe PREV-Ex exercise trial is a multicenter two-armed randomized controlled trial. Patients will be randomized to an exercise program consisting of home-based low-load BFR-T during a combined pre- and postoperative period for a total of 6–10 weeks (prehabilitation and rehabilitation), or to a control group. Protein supplementation will be given to both groups to ensure adequate protein intake. The primary outcomes, skeletal muscle thickness and muscle cross-sectional area, will be assessed by ultrasound. Secondary outcomes include the following: (i) muscle catabolism-related and inflammatory bio-markers (molecular characteristics will be assessed from a vastus lateralis biopsy and blood samples will be obtained from a sub-sample of patients); (ii) patient-reported outcome measures (self-reported fatigue, health-related quality of life, and nutritional status will be assessed through validated questionnaires); (iii) physical fitness/performance/activity (validated tests will be used to evaluate physical function, cardiorespiratory fitness and maximal isometric muscle strength. Physical activity and sedentary behavior (assessed using an activity monitor); (iv) clinical outcomes: hospitalization rates and blood status will be recorded from the patients’ medical records; (v) explorative outcomes of patients’ experience of the exercise program which will be evaluated using focus group/individual interviews.DiscussionIt is worthwhile to investigate new strategies that have the potential to counteract the deterioration of skeletal muscle mass, muscle function, strength, and physical function, all of which have debilitating consequences for patients with pancreatic, biliary tract, and liver cancer. The expected findings could improve prognosis, help patients stay independent for longer, and possibly reduce treatment-related costs.Trial registrationClinicalTrials.gov NCT05044065. Registered on September 14, 2021.

A comparative study of Newtonian and non-Newtonian blood flow through Bi-Leaflet Mechanical Heart Valve

The present study examines flow through Bi-Leaflet Mechanical Heart Valves (BMHV) at physiological conditions considering both Newtonian and non-Newtonian fluid models for blood rheology. It is well known that the non-Newtonian effects of blood are pronounced in small diameter arteries. Most of the earlier works on Mechanical Heart Valves (MHV) have considered blood as a Newtonian fluid as the flow involves large-diameter artery such as the aorta. In this work, we have reported the predicted parameters, such as leaflet kinematics, vortex structures, wall shear stress, and blood damage index for both blood models. It is found that the leaflet attributes smaller asynchronous motion in the case of non-Newtonian Carreau fluid model with slightly reduced angular velocity compared to the Newtonian assumption. Predictions on the blood damage index suggest a 21% higher damage while using non-Newtonian model than Newtonian model, which may be attributed to higher levels of mechanical stress within the fluid. However, vortex structures, time-averaged wall shear stress (TAWSS), and oscillatory shear index (OSI) are found to be similar in predictions using both the fluid models. We have used an in-house sharp interface immersed boundary method with fluid–structure interaction to simulate the coupled action of moving valves and pulsatile blood flow. Our findings suggest that the general consensus of using Newtonian model in large arteries may not be appropriate for prediction of leaflet kinematics and blood damage index in Mechanical heart valves.

Biomechanical considerations of semi-anatomic glass fiber-reinforced (GFRC) composite implant for mandibular segmental defects: A technical note

ObjectivesThe aim of this study was to investigate the selected biomechanical properties of semi-anatomic implant plate made of biostable glass fiber-reinforced composite (GFRC) for mandibular reconstruction. Two versions of GFRC plates were tested in vitro loading conditions of a mandible segmental defect model, for determining the level of mechanical stress at the location of fixation screws, and in the body of the plate. MethodsGFRC of bidirectional S3-glass fiber weaves with dimethacrylate resin matrix were used to fabricate semi-anatomic reconstruction plates of two GFRC laminate thicknesses. Lateral surface of the plate followed the contour of the resected part of the bone, and the medial surface was concave allowing for placement of a microvascular bone flap in the next stages of the research. Plates were fixed with screws to a plastic model of the mandible with a large segmental defect in the premolar-molar region. The mandible-plate system was loaded from incisal and molar locations with loads of 10, 50, and 100 N and stress (microstrain, με) at the location of fixation screws and the body of the plate was measured by strain gauges. In total the test set-up had four areas for measuring the stress of the plate. ResultsNo signs of fractures or buckling failures of the plates were found during loading. Strain values at the region of the fixation screws were higher with thick plate, whereas thin plates demonstrated higher strain at the body of the plate. Vertical displacement of the mandible-plate system was proportional to the loading force and was higher with incisal than molar loading locations but no difference was found between thin and thick plates. ConclusionGFRC plates withstood the loading conditions up to 100 N even when loaded incisally. Thick plates concentrated the stress to the ramus mandibulae region of the fixation screws whereas the thin plates showed stress concentration in the angulus mandibulae region of the fixation and the plate itself. In general, thin plates caused a lower magnitude of stress to the fixation screw areas than thick plates, suggesting absorption of the loading energy to the body of the plate.

The Impact of Knee and Ankle Injuries on National Basketball Association Player Performance Post-injury.

Athletes in the National Basketball Association (NBA) are subjected to high levels of mechanical stress increasing their risk of injury. The purpose of this study was to see how certain lower extremity injuries affect in-game performance in relation to each NBA athlete's demographics. The hypothesis was that NBA players' post-injury performance would differ depending on their demographics and the type of injury sustained. Descriptive epidemiology study of NBA injury list designations from the 2010/2011 season to the 2018/2019 season. About 255 lower leg injuries that met the inclusion criteria were selected from the injury lists spanning from the 2010/2011 season to the 2018/2019 season. These included ligamentous knee injuries, knee sprains, knee strains, knee hyperextensions, patellar injuries, ankle injuries, and Achilles injuries. The change in performance was determined by comparing mean game scores before and after injury with single-tailed, heteroscedastic t-testing and 95% confidence intervals for mean values. An overall statistically significant decrease in mean game score from 9.82 to 8.75 was seen in all included players (p = 0.01). Only athletes taller than the mean height (199.85 cm; p = 0.01) and heavier than the mean weight (101.63 kg;p = 0.02) showed a significant decline in performance. Ankle and knee injuries both resulted in a significant loss in game score (p = 0.04), with ankle injuries resulting in a greater average decline (-1.76 post-injury) than knee injuries (-1.34 post-injury). These findings suggest that treatment regimens should reflect the type of injury and demographics of the specific NBA player injured. Further research is warranted to determine if treatment may be more efficacious when streamlined based on player size and injury type.

Sex differences in mechanical stress and associated labor in Hellenistic–early Roman Menainon, Sicily

AbstractThis paper explores mechanical stress in the Hellenistic/early Roman community of Menainon (Sicily) to test the existence of sex‐based division of labor. For this purpose, human skeletal remains from 79 males and 65 females, dating to the 4th–1st ca. BCE, were examined for degenerative joint disease, intervertebral disc disease, cross‐sectional geometric properties, and entheseal changes. Our findings support an equal share of workload between males and females, who appeared to have experienced similar mechanical stress levels. In contrast, they do not support a systematically greater mechanical load among males, as would have been expected if females had been restricted indoors taking care of domestic tasks only, while men had dealt with most physically demanding outdoor activities. The patterns identified in the current study agree with a scenario where agriculture was a prominent subsistence activity (as attested historically for this region) and most members of this rural community engaged in agricultural tasks irrespective of sex. Our study has limitations regarding the available historical and archaeological information, which restrict our ability to formulate solid research hypotheses or fully contextualize the bioarchaeological results. Nonetheless, it does highlight the importance of critically assessing historical information regarding the role of men and women in the Greco‐Roman society.

Metal‐organic framework‐based nanofibrous film for two different modes of triboelectric nanogenerators

AbstractMetal‐organic frameworks (MOFs) are nanomaterials with engineered chemical structures, offering remarkable properties. However, their limited film‐formation capability hinders their integration into triboelectric nanogenerators (TENGs). This study proposes a simple yet effective solution to overcome this challenge by employing electrospinning techniques to integrate the zeolitic imidazolate framework (ZIF‐8) into an easy‐to‐use nanofibrous mat. ZIF‐8 has high surface potential, a unique cubical structure, and an easy fabrication process that makes it an ideal material for TENGs. By incorporating ZIF‐8 into the electrospinning solution, significant improvements are achieved in the electropositivity of the resulting nanofibers. It leads to notable changes in the shape, morphology, and roughness of electrospun fibers, consequently enhancing the overall performance of the TENG. The results indicate that utilizing the ZIF‐based electrospun mat as a tribo‐positive material can increase transferred charges between electrodes by more than 100%. Utilizing the MOF‐based nanofibrous mat, this study also introduces a novel rotary TENG that works based on a mode of TENG operation called rolling mode. The reliable charge generation by the proposed rolling system reveals that this mode of TENG operation could be a superb alternative for traditional TENG modes, like contact/separation or sliding, which cause high levels of mechanical stress due to harsh physical impact or friction.

Sustainable Energy Safety Management Utilizing an Industry-Relative Assessment of Enterprise Equipment Technical Condition

The study considers approaches to ensuring energy management for the safe operation of facilities and their equipment and ways to improve it. It has been established that to ensure effective safety management of industrial enterprises, one of the critical areas is the technical diagnostics of power equipment during operation. An assessment of the actual technical condition of power equipment of VVER-1000 power units is proposed based on establishing the aging mechanisms and determining the relative evaluation coefficients for the characteristics of individual equipment elements. The results of the calculations allowed us to conclude that the obtained results correspond to the coefficients of relative assessment Ki of the technical characteristics of the power equipment that determine its degradation. Studies indicates that when assessing the state of power equipment, it is necessary to consider the presence and impact of the following operational factors that are not considered in the design calculations: loads, high levels of mechanical stress, fatigue damage, and metal defects, which primarily indicate the presence of degradation changes. To assess the technical condition of the equipment, considering the degree of mechanical wear, 17 technical characteristics were selected to determine the aging mechanisms by signs of degradation. A mathematical model of the dependence of the relative evaluation coefficient K on changes in the operating parameters is presented, and it is noted that the most significant influence on the value of the coefficient is the temperature of the coolant at the inlet (K = 0.56). The developed approach makes it possible to improve the safety management system of power facilities by introducing the proposed model to assess the technical conditions of power equipment by defining the parameters in the overall safety management system.

Destabilization of Indomethacin-Paracetamol Co-Amorphous Systems by Mechanical Stress.

Using co-amorphous systems (CAMS) has shown promise in addressing the challenges associated with poorly water-soluble drugs. Quench-cooling is a commonly used CAMS preparation method, often followed by grinding or milling to achieve a fine powder that is suitable for subsequent characterization or further down-stream manufacturing. However, the impact of mechanical stress applied to CAMS has received little attention. In this study, the influence of mechanical stress on indomethacin-paracetamol CAMS was investigated. The investigation involved thermal analysis and solid-state characterization across various CAMS mixing ratios and levels of mechanical stress. The study revealed a negative effect of mechanical stress on stability, particularly on the excess components in CAMS. Higher levels of mechanical stress were observed to induce phase separation or recrystallization. Notably, samples at the optimal mixing ratio demonstrated greater resistance to the destabilization caused by mechanical stress. These results showed the significance of careful consideration of processing methods during formulation and the significance of optimizing mixing ratios in CAMS.

Assessment of Mechanical Damage and Germinability in Flaxseeds Using Hyperspectral Imaging.

The high demand for flax as a nutritious edible oil source combined with increasingly restrictive import regulations for oilseeds mandates the exploration of novel quantity and quality assessment methods. One pervasive issue that compromises the viability of flaxseeds is the mechanical damage to the seeds during harvest and post-harvest handling. Currently, mechanical damage in flax is assessed via visual inspection, a time-consuming, subjective, and insufficiently precise process. This study explores the potential of hyperspectral imaging (HSI) combined with chemometrics as a novel, rapid, and non-destructive method to characterize mechanical damage in flaxseeds and assess how mechanical stresses impact the germination of seeds. Flaxseed samples at three different moisture contents (MCs) (6%, 8%, and 11.5%) were subjected to four levels of mechanical stresses (0 mJ (i.e., control), 2 mJ, 4 mJ, and 6 mJ), followed by germination tests. Herein, we acquired hyperspectral images across visible to near-infrared (Vis-NIR) (450-1100 nm) and short-wave infrared (SWIR) (1000-2500 nm) ranges and used principal component analysis (PCA) for data exploration. Subsequently, mean spectra from the samples were used to develop partial least squares-discriminant analysis (PLS-DA) models utilizing key wavelengths to classify flaxseeds based on the extent of mechanical damage. The models developed using Vis-NIR and SWIR wavelengths demonstrated promising performance, achieving precision and recall rates >85% and overall accuracies of 90.70% and 93.18%, respectively. Partial least squares regression (PLSR) models were developed to predict germinability, resulting in R2-values of 0.78 and 0.82 for Vis-NIR and SWIR ranges, respectively. The study showed that HSI could be a potential alternative to conventional methods for fast, non-destructive, and reliable assessment of mechanical damage in flaxseeds.

Mekanik ventilasyon modlarının prematüre bebeklerin tükürük kortizol düzeylerine etkisi

Purpose: The aim of this study was to examine the relationship between mechanical ventilation modes and stress levels by measuring salivary cortisol levels in preterm infants.
 Materials and Methods: The study group comprised 65 preterm infants on respiratory support and 43 control preterm infants. The Neonatal Infant Pain Scale (NIPS) was used to evaluate pain. To determine the stress level, salivary cortisol levels were studied in saliva samples taken in the morning and evening on the 4th postnatal day.
 Results: In the study group, morning and evening cortisol levels of the infants were measured 8.33±5.7 ng/ml and 8.05±5.6 ng/ml, respectively. In the control group, morning and evening cortisol values of the infants were measured 1.50±0.7 ng/ml and 1.48±0.7 ng/ml, respectively. The morning and evening salivary cortisol levels of the infants in the study group were significantly higher than those of the infants in the control group. In the invasive mechanical ventilation group infants, morning and evening cortisol levels of the infants were measured 12.46±5,3 ng/ml and 12.0±5,2 ng/ml, respectively. In the non-invasive mechanical ventilation group, morning and evening cortisol values were measured 4.57±2.7 ng/ml and 4.41±2.7 ng/ml, respectively. Both morning and evening salivary cortisol levels of infants on invasive mechanical ventilation were higher than those of infants on non-invasive mechanical ventilation. 
 Conclusion: Increased salivary cortisol levels in invasive modes indicate that intubation causes pain and stress in newborns.

Wind erosion after steppe conversion in Kazakhstan

Semi-arid regions of Central Asia suffer from wind erosion due to expanding steppe conversion and unsustainable farming practices. Empirical data from field observations are needed to support the implementation of adapted management. In this study, a mobile wind tunnel was used for the first time in Kazakhstan to assess the soil's erodibility under real conditions. Field experiments were conducted on loamy sands with different initial conditions that are typical for the most erosive time of the year: a bare surface with a cloddy structure after recent steppe conversion, a weak crust on a plot with barley (Hordeum vulgare L.), and a plot with loose material in the rows of maize plants (Zea mays L.). Subsequently, different levels of mechanical stress (low, moderate, high) were considered to analyze the effect of disruptive forces soils experience during field cultivation (light cultivator, disc harrow, tractor tires) on possible soil losses. The results of wind tunnel experiments showed already great differences under initial conditions. The cloddy structure of the recent steppe conservation had the lowest susceptibility against wind erosion due to a good aggregation and a large roughness, resulting in soil loss of 12 g m−2. The plot grown with barley was less affected by wind erosion due to the weak crust, smaller distances between plants, and leaves close to the ground (soil loss of 34 g m−2). Maize was also the most problematic crop in the study area because wind can blow below the plant canopy without considerable resistance during the early growth stages. Additionally, existing deposits in the maize rows from previous erosion events led to the highest soil loss of 1609 g m−2. Mechanical stress by seedbed preparation generally increased the erodible fraction, resulting in higher soil losses (light cultivator: 198 ± 129 g m−2, disc harrow: 388 ± 258 g m−2). The most severe disruption of soil structure occurred on tractor tire tracks, causing a loss of 2767 ± 1810 g m−2. Consequently, the pulverizing effect of tractor tires on dry soil must be considered a serious emission source. Comparing the soil organic carbon content of topsoil and eroded material showed that organic carbon was enriched only in the aeolian sediments of the recently converted plot (+69%). We conclude that soils after steppe conversion need to be treated with particular care from the very beginning so that severe events from the past are not repeated.

Development of the Kinetic Equation of the Groove Corrosion Process for Predicting the Residual Life of Oil-Field Pipelines

One of the main reasons for oil-field pipeline failure is groove corrosion. The residual life of such pipelines is estimated based on defectoscopy corrosion rate—a ratio of the formed «groove» depth to the pipeline operation start time. In this case, it is supposed that, in the future, the «groove» will deepen at the same rate for the remaining period of the pipe’s operation. However, sometimes, oil-field pipeline operation experience shows that the remaining time of safe operation is much less than the calculated one. In this article, such a discrepancy is explained via the acceleration of the groove corrosion rate in the process of «groove» deepening due to the increasing level of mechanical stresses in the surrounding metal, which intensifies the corrosion process as a result of the mechanochemical effect. Based on a literature analysis and calculated data, the kinetic equation of the groove corrosion rate for an oil-field pipeline is proposed, which accounts for the acceleration of the process rate as the pipeline is operated and allows the more accurate estimation of its remaining service life.

Mechanical stress in the urbanized Roman Phoenician coast

ObjectiveSkeletal populations from Byblos, Beirut, and Tyre were studied to assess mechanical stress along the Roman Phoenician coast. MaterialsThe sample included 153 adult skeletons. MethodsSkeletal remains were macroscopically assessed for osteoarthritis, intervertebral disc disease (IDD), and Schmorl’s nodes. ResultsThe Byblos population experienced higher levels of mechanical stress than the Beirut and Tyre ones. Sex-based differences were also found in all skeletal assemblages with males likely engaging in physically more demanding tasks. ConclusionsThe variation in mechanical stress, and associated physically demanding tasks, between these populations can be attributed to their differing political and economic status during the Roman period; textual sources highlight the economic and political dominance of Beirut and Tyre, emanating from their status as coloniae. SignificanceThis study represents one of the first attempts to investigate mechanical stress in coastal Phoenicia during the Roman period. It provides valuable insights into the biocultural structure of understudied communities at the periphery of the Roman world, and can serve as a basis for further future research into the occupational patterns of Phoenician communities. LimitationsThe contextual information for these skeletal populations is very limited and does not allow secure conclusions regarding their representativeness. The sample sizes are also rather small, especially when divided per sex and age. Suggestions for Further ResearchFurther investigation employing complementary methods such as cross-sectional geometric properties and entheseal changes is needed to reconstruct the occupational patterns of these communities, taking into account cultural, environmental, and temporal factors.

DIAGNOSTICS OF THE PRESS POWER FRAME WITH THREADED CONNECTIONS OF LOAD-BEARING ELEMENTS BY STRAIN GAUGE METHOD

The distribution of tightening forces between several threaded connections of power elements of machines and mechanisms directly affects the strength and reliability of the entire structure. When operating heavily loaded mechanisms with threaded connections in excess of the deadlines set in the technical documentation, the likelihood of loosening the tightening increases. This negatively affects the distribution of stresses in the power frame and, under unfavorable conditions, can lead to an increase in the level of mechanical stresses to critical values. The purpose of the work is a strain gauge method for monitoring the power frame of a hydraulic stamping press with threaded connections to assess the operability of the structure and conclude on the feasibility of repairs. Using strain gauges and finite element modeling methods, the regularities of the distribution of deformations in the material of columns and press racks with a maximum workload of 10 thousand tons are established. It is shown that in the working cycle, deformations are determined by the force and moment of force associated with the eccentricity of the application of the working force. Criteria for assessing the quality of threaded connections based on the relative difference and simultaneity of changes in mechanical stresses in the material of columns and press racks have been developed. The immobility of the connections of the power frame of the press during operation with maximum effort is ensured by the uniformity of the stress distribution on the racks and columns, taking into account the error of the results of the strain gauge method of 5%. The influence of the sliding elements of the movable elements of the press on the experimentally established patterns of stress distribution is substantiated by the method of finite element modeling.

Progress on the R&D for the New Cable-in-Conduit Conductor Type of the MADMAX Dipole

The concept of Cable-in-Conduit Conductor (CICC) has been adopted for the large superconducting dipole of the MADMAX project. It is based on a multistage cable inserted in a potentially pre-hardened copper profile and then compacted together down to the final rectangular shape. NbTi technology and internal cooling with stagnant superfluid helium is kept in order to operate at 1.8 K. On the other hand, the use of copper instead of stainless steel as for common CICCs for fusion magnets led to an extensive R&D phase. The need to improve the mechanical properties of the conduit to withstand the high level of mechanical stress in the magnet requires significant level of cold working, which can be obtained by compacting a profile with a large initial cross-section. Manufacturing with high compaction over long lengths, within certain tolerances, represented a challenge to find the initial shape of the profile. To deal with it, different compaction scenarios were simulated by Finite Element Methods on two copper profiles eventually manufactured. A mechanical tests campaign aimed to investigate the properties of the processed samples was also carried out. In the present work, the main characteristics of the new MADMAX CICC will be summarized, the R&D phase will be presented and the results will be widely discussed.

Quantification and modeling of macroparticle-induced mechanical stress for varying shake flask cultivation conditions.

In biotechnological processes, filamentous microorganisms are known for their broad product spectrum and complex cellular morphology. Product formation and cellular morphology are often closely linked, requiring a well-defined level of mechanical stress to achieve high product concentrations. Macroparticles were added to shake flask cultures of the filamentous actinomycete Lentzea aerocolonigenes to find these optimal cultivation conditions. However, there is currently no model concept for the dependence of the strength and frequency of the bead-induced stress on the process parameters. Therefore, shake flask simulations were performed for combinations of bead size, bead concentration, bead density and shaking frequency. Contact analysis showed that the highest shear stresses were caused by bead-bottom contacts. Based on this, a newly generated characteristic parameter, the stress area ratio (SAR), was defined, which relates the bead wall shear and normal stresses to the total shear area. Comparison of the SAR with previous cultivation results revealed an optimum pattern for product concentration and mean product-to-biomass related yield coefficient. Thus, this model is a suitable tool for future optimization, comparison and scaling up of shear-sensitive microorganism cultivation. Finally, the simulation results were validated using high-speed recordings of the bead motion on the bottom of the shake flask.

Formulation of a Mechanical Stress Dependent Macroscopic Magnetic Model for Incremental Permeability Simulation

Electromagnetic based systems receive ever-growing interest for on-line assessment of steel strip properties for major manufacturers, especially when Advanced High Strength Steel (AHSS) products for automotive purposes are considered. Manufacturing AHSS need optimal control of the thermo-mechanical processing using in-line sensors for real time monitoring. IMPOC, 3MA and PropertyMon are some of the well-known electromagnetic sensors. Identification of a mechanical or metallurgical state from a magnetic signal is of great interest, requiring however sophisticated models to mimic the real behaviour and its sensitivity to many influencing parameters. Our paper presents a proposition to add the dependency of mechanical stress to the Jiles-Atherton hysteresis model. Experimental data consist of B(H) curves of carbon steels strips subjected to different levels of mechanical stress applied along the magnetic measurement direction. The JilesAtherton model has then been used to find out a set of stress-dependent coefficients. The variation of coefficients with stress is in close relationship with the variations of coercive field, remanent induction and permeability with stress. A coupled magneto-mechanical approach allows physics-based functions to be proposed to describe the evolution of JilesAtherton coefficients with stress. In this paper, experimental working conditions will be described, as well as the stressdependent Jiles-Atherton model. The model is finally implemented in FEM software, allowing more complex magneto-mechanical situations to be modelled. After matching with measurement, the new model is applied on 3MA modelling where magnetic transient analysis and magnetic AC steady state analysis are linked through incremental permeability.

Finite Element Simulation and Stress Analysis of Gas Turbine Blade Due to Centrifugal Force

Gas turbine always consider one of the most important system in the modern engineering applications, because it has continuous ability to generate electric power. In gas turbines the major portion of performance dependency lies upon turbine blade design ,the blades are considered one of the important and expensive parts in the gas turbines , where the blades of first stage from failure . Most studies indicate that 50% of failure and breakage accidents cannot be accurately determined due to the large number of variables .The blades of the gas turbine suffer from tensile stresses due to centrifugal forces resulting from the high rotational speed and because of the loading of dense gasses at a high temperature and speed ,as the centrifugal force is one of the problems that the designer of the turbine blades faces , as the designer aims to reduce stresses within the permissible limit . The current work is concerns with study and analysis of the stresses at the first stage blades in Al Mosul power station at Mosul city, AUTOCAD which is computer program has been an efficient software to draw and specify blade dimensions at the exact measurement, as well as the ANSYS 21 software program was also used as an effective tool in determining the stresses and deformation under the influence of centrifugal force. As the blade was considered root bound in all direction (X, Y and Z) and adding the special mechanical properties of (INCONEL738 alloy), After conducting a stress analysis in the program, it was found that the stress values of the posterior and anterior edge of the blade root region were high and these results were validated with the results carried out by some studies that dealing with study and analysis of the blades at the first stages in turbine stations. The static and modal analysis of the turbine blade is being considered. To analyze these aspects, the blade is represented using the 3D-Solid Brick element. The blade's geometric model is created by generating and then extruding them to form a solid model. An analytical approach is utilized to estimate the centrifugal forces. The objective of this presented work is to investigate the impact of mechanical analysis on the structure of gas turbine blades. The findings indicate lower levels of mechanical stress.