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The article discusses ways to increase the sensitivity of electromagnetic direct current (DC) converters. The devices and the principle of operation of the converter using two magnetic fields are shown: a constant measured field and an auxiliary modulation field created by an alternating current flowing through the modulation winding. The analysis of approximation formulas in the form of incomplete odd power polynomials of magnetic materials of open-core current converters depending on the type of modulation is carried out. To calculate the EMF at the output of the converter, expressions are obtained that take into account the magnetic tensions caused by the modulation current. Expressions for the comparative analysis of sensitivity, when modulated by a signal of sinusoidal, rectangular and triangular shapes, are given. The use of a rectangular modulation sbape allows you to increase sensitivity in relation to other types of modulation. [ABSTRACT FROM AUTHOR]

The paper deals with the analysis of the economic growth model with CES-production function. The elasticity parameter of this function varies up to its limit value of one. In the limit case of the unit elasticity, the production function turns into Cobb-Douglas type. A special attention in the paper is devoted to this limit transformation and its impact on the stabilized solutions. Numerical examples finalize the paper. [ABSTRACT FROM AUTHOR]

The subject of the article is a description of the procedure for determining the optimal values of the Tuned Mass Damper (TMD). Apply a TMD is one of the options to ensure that the serviceability criteria of a light bridge structure are met. The relations derived for the two-degree system are used to determine the stiffness, damping and mass of the shock absorber. This procedure cannot be used for moving loads. The damper reduces the response to only one eigen shape, it is generally ineffective for others. Therefore, the effort is to minimize the weight of the additional mass. The parameters depend on the selected optimized function, whether the goal is to minimize displacements or acceleration. Another aspect discussed in the article is the change of parameters due to the presence of pedestrians on the footbridge. The calculation model of the footbridge was made in ANSYS software technology. Sensitivity analysis was performed and managed by the OptiSlang module. This module controls the generation of inputs for a geometrically nonlinear computational model and is used to evaluate the sensitivity and robustness of the results. The article is limited to the solution of the dynamic response of moving persons. [ABSTRACT FROM AUTHOR]

In this paper, the population was divided into seven subpopulations, namely susceptible (S), vaccination (V), exposed (L), infected not reported (I1), infected reported (I2), quarantine (Q) and recovered (R) subpopulations. Analytical study on the COVID-19 model, to determine the non-endemic equilibrium point, reproduction number, and system stability. The model solution was determined by numerical analysis, and model sensitivity analysis by changing the values of the vaccination rate and treatment rate parameters. Based on numerical simulation results, if the value of the vaccination parameter or the value of the treatment parameter increases, the number of individuals in the subpopulation infected with COVID-19 decreases, and the number of individuals recovered from the subpopulation increases. [ABSTRACT FROM AUTHOR]

The core of this work presents an assembly method of EEG signals for the early detection of brain tumors using a novel support vector machine (SVM) algorithm compared with a decision tree algorithm Materials and methods: Collected from UCI repository 1472 samples contain 19 attributes. Early detection of brain tumors is performed using two groups, where group 1 is a SVM and group 2 is a decision tree. For the analysis of groups 1 and 2, 40 samples were used. Results: The accuracy of the SVM algorithm was 93%, while the accuracy of the decision tree was 82%. A significant value of 0.037 (P<0.05) was obtained and determined by independent samples test. Conclusion: The support vector machine algorithm has significantly higher accuracy than the decision tree algorithm. [ABSTRACT FROM AUTHOR]

A wide variety of models have been proposed to assess the effect of vortex shedding loads on the dynamics of bluff bodies. To the best of the authors' knowledge, a critical review of such models applied to wind turbine towers has not been carried out. A comparison is made in the present work of three well-known models, ranging from the simplest type A or forced system model, through type B or fluidelastic system model, to type C or coupled system model. Time-marching simulations are performed using classical modal analysis of an isolated wind turbine tapered tower subjected to a sheared and turbulent wind profile. Tower dynamics and vortex shedding-induced loads are limited to the cross-flow direction. Maximum tower top deflections are presented in the comparison, and a sensitivity analysis to type C parameters is performed. The results provide a comparison of the qualitative differences of the different modelling levels applied to a wind turbine tower. Further development of type C models seems to be a promising path to be used in the wind energy community to assess vortex-induced vibrations of wind turbine towers. [ABSTRACT FROM AUTHOR]

Nanoparticle production using microemulsion droplets has become a very interesting technique in the recent years. It allows a controlled adjustment of the particle size, which is an essential task due to the highly size-dependent properties of nanoparticles. The technical-scale production of nanoparticles with defined properties is of particular interest due to the increasing demand from industry. Efficient models are necessary for a fundamental understanding of this complex process. A sensitivity analysis about nucleation and growth order are simulated and resulted a qualitatively good agreement. [ABSTRACT FROM AUTHOR]

Workload fluctuation is one of the challenges facing contracting organizations. Previous studies balanced this fluctuation using capacity adjustment. Most of these studies ignored the simultaneous effect between the direct and indirect variables and the nondeterministic nature of these variables. Moreover, local decisions, i.e. project-based decisions, receive the most attention from contractors. Contrarily, its long-term effect on the organization and its influence on the future project's success receives little attention. This study utilizes a system dynamics approach to holistically address the workload fluctuation of contracting organizations. The model links the pre-award and after-award project phases at the portfolio level. The model is validated through extreme case analysis, units' consistency test, sensitivity analysis test, and industry experts. Results from model analysis inform that the internal behavior and mental model (soft logic) are significantly affecting the long-term performance of contractors more than the external (hard) factors. For instance, the quality level is more important than the initial cash. Also, overhead and markup percent have a significant impact on long-term behavior. Overheads have a relatively more effect on short-term behavior than the markup percent. This research is limited to representing the contracting organization in the execution phase and could be enhanced in the future by incorporating other phases such as design. [ABSTRACT FROM AUTHOR]

Crowd dynamics modeling plays a key role in planning and management large-scale gatherings, especially when it comes to improving pedestrian facility design and optimizing evacuation. This work deals with a sensitivity analysis to investigate the impact of domain quality, crowd density, and distribution, size of exits, layout and shape of obstacles, and exit size on evacuation times. Using a discrete kinetic model, pedestrian-pedestrian and pedestrian-environment interactions are taken into account. The framework is parameterized to assess the impact of the factors driving evacuation time in emergency situations, in particular, the position and shape of the obstacles. [ABSTRACT FROM AUTHOR]

A sustainable inventory system aims to increase the quality of its production and reduce its impact on the environment without increasing its costs. This study presents an economic production quantity (EPQ) model with a rework process where the production of good quality items is used to fulfil primary market demand, whereas the reworked defective items are used to fulfil secondary market demand. There are five cases being observed during the simultaneous production process and reworking process, and a generalised model that minimises the total cost per unit time (TCUT) is developed. The proposed model is experimented with using a variety of numerical examples, and a numerical sensitivity analysis that studies how different system parameters affect costs is performed. This analysis suggests that the proposed model is fairly robust to changes in parameters; however, the higher the proportion of defective items in a production lot size, the more serious the impact on the optimal cost. The results show that the TCUT is increasing exponentially with respect to the proportion of defective items in a production lot size. [ABSTRACT FROM AUTHOR]

Inventory models for stock-dependent demand have been developed continuously in recent years. In this paper, we develop inventory dependent model for multi-items by considering stock-dependent demand and stock-dependent holding rate for a rack that has a specific capacity. Two models are developed. The first model is an individual order quantity for each item and the second model is a joint replenishment model. The non-linear model with constraint is solved using an evolutionary algorithm. A numerical example and sensitivity analysis are conducted to show how the models work and to get some management insights. The sensitivity analysis shows that there is no dominant model. However, the joint replenishment order outperforms the individual order when the rack capacity is tight and there is a high ordering cost [ABSTRACT FROM AUTHOR]

The current research aimed to the nuclear fuel reflects the transformation of the power generation industry and consequences of the Fukushima accident. Accident tolerant fuel should handle load follow operation longer time irradiation time and in parallel withstand Design Basis Conditions. To reasonable predict and validate designed fuel performance it is necessary to benchmark the computational tools against high quality experimental data. Therefore, this paper demonstrates computational capabilities of the FEMAXI-6 code to predict thermomechanical parameters of ATF type fuel. Two rods with Cromium dopped fuel with large grain size were of interest within Halden High Initial Rating experiment, where the fuel was exhibited to high power rate at the level of 400 W/cm directly from the beginning of experiment. The calculations of FEMAXI-6 code were carried out with its standard capabilities and available models and sensitivity analyses was performed to identify the most representing definitions. Prediction of the fuel center temperature was in good agreement with measurements, where the main discrepancies were obtained in the first period of the irradiation. FGR as well as rod pressure were underpredicted in both rods and the code limitations were identified. [ABSTRACT FROM AUTHOR]

The toggle-type injection moulding machine is studied in this project to analyze the effect of tolerance stack-up of the toggle mechanism on the clamping unit of the injection moulding machine. The toggle mechanism comprises kinematic linkages with pin joints to transfer force and movements from the hydraulic cylinder to the platen for the closing and opening of the die. The dimensions of these links play a crucial role in the clamping force generation to hold the moulds in place. By determining the tolerance sensitivity of the components, critical component dimensions which affect the mechanism's straightness and product quality can be identified. In this study, analytical equations are derived from the geometrical analysis of the mechanism for calculating the middle pin deviation, and also CAD methods are implemented to verify the results. In the CAD method, a 2D line diagram of the mechanism is made in SolidWorks with proper constraints. The analysis is divided into two cases-in the first case, the pin deviation is calculated when the machine is under no tonnage condition (crosshead position fixed). The second case calculates the pin deviation under the tonnage condition (moving platen position fixed). Pin deviation is calculated by giving tolerance to all the link dimensions one at a time. Tolerance stack-up is carried out by identifying the worst case from the tolerance sensitivity analysis of individual components and links. By carrying out the analysis, it can be concluded that under no tonnage condition, short link (101.803 mm), tertiary link (65 mm), crosshead distance (170 mm), and rear platen distance (350 mm) have a significant effect on the pin deviation in comparison to the other link dimensions. While for tonnage conditions, the tertiary link (270 mm) and binary link (419.143 mm) significantly affect the pin deviation compared to the tolerance of other links. [ABSTRACT FROM AUTHOR]

Mathematical models appear in many forms, such as instantaneous dynamics (ordinary differential equations) or time-lags dynamics (delay differential equations). It is important to investigate the effect on the model outputs when a perturbation is applied to the initial or boundary conditions, time delay parameters, or any model parameters in the governing equations. In this paper, we study the general theory of sensitivity analysis based on the direct differential method for systems governed by delay differential equations. Problems governed by ordinary differential equations can also be considered as a particular case of delay differential equations with the absence of delays. The normalized forward sensitivity indices are then computed to identify the important model inputs. To show the efficiency of the methodology, we apply the theory and numerical computations to immunology and infectious disease models. [ABSTRACT FROM AUTHOR]

The spread of the Covid-19 virus has changed the social order and led to the emergence of a new era. One of the new habits that emerged is the use of video conferencing for meetings and learning. There are many alternatives to video conferencing that can be found today. This study aims to determine user preferences for video conferencing with criteria based on web equal 4.0. the method used is the Analytical Hierarchical Process (AHP) method with the help of super decision software, which is free and easy to use. Based on the results of this study, it was found that the highest criterion preference was for information criteria followed by interaction and usability. Based on criteria, Google meet is preferred by users, followed by BBB and Zoom. Based on the sensitivity analysis results, it can be concluded that the value of alternative preferences for criteria will not change, regardless of the value of the criteria. [ABSTRACT FROM AUTHOR]

Yarn is the main material that forms fabric. A quality yarn can be woven at high speed and high density. One of the indicators of yarn quality is the tensile strength of the yarn with the objective function of Larger the Better (LTB) and the size of the pickup of the yarn with the objective function of Smaller the Better (STB). Factors that are thought to affect the quality of the yarn are the concentration of a starch solution (A), the temperature of the starch solution (B), the depth of the roll in the starch bath (C), the pressure of the spinner roll (D), the speed of drawing the yarn (E), the temperature of the drying cylinder (F) and thread tension (G). The TOPSIS method is used to determine the optimal conditions for the factor level of the warp yarn testing process and reduce the number of experiments. A combination of factor levels was obtained in this study A2, B1, C1, D2, E1, F2, and G2. The combination of this optimal factor level decreased the quality of the tensile strength of the yarn by 0.60%. It increased the quality of the size pick-up by 26.89% against the initial conditions. In addition, four alternatives can be selected to improve the yarn's quality, both in tensile strength and pick-up size. To accommodate the dynamic weighting of product quality attributes, an analysis of the effect of weighting priority attributes of tensile strength and size of yarn pick-up is carried out under optimal conditions. Based on the sensitivity analysis, the results show that the optimal factor level combination will change if the weighting for the tensile strength of the yarn increases to ≥ 0.65744 or decreases to ≤ 0.27299. [ABSTRACT FROM AUTHOR]

The speed and completeness of the information provided by the internet is an attraction and a basic need for internet customers. Internet Service Providers (ISP) must provide a better quality of service or QoS and different to customers at a minimum cost. This service must be improved by using the variables Fair Network Traffic Management and Selfish customer. C-RAN is a centralized radio access network connected to a cellular antenna to process signals and transmit them to the core network. Determining and modeling C-RAN can be done by inserting a schema model for measuring internet network customer satisfaction with optimization of bandwidth consumption. Testing the sensitivity analysis can determine the optimal parameters that are solved with the help of Lingo 13.0 software. This study aims to analyze the sensitivity of the selfish customers and fair network models combined into the C-RAN model to the internet network scheme model on consumption bandwidth. This research data is secondary data obtained from the server of the Sriwijaya State Polytechnic building in Palembang. The results obtained from this study in a C-RAN model is then obtained with the optimal solution by using local server data shows better results compared the previous research without dealing with utility function by determining the initial consumption (QN) and the maximum bandwidth consumption (P0). Then, if the analysis of the model is explored in depth using sensitivity analysis, it is found that if the variable is infinity, the increase or decrease is not fixed and can change, while a variable with a value of 0.000 means that the increase or decrease is fixed, then the values cannot be changed. [ABSTRACT FROM AUTHOR]

Computational modelling technique represents the only method, how to assess a functionality of a designed nuclear wastes repository in a long term period that accounts for hundreds of year. Such a technique is based on exploitation of results of short-term experiments that work as input data. Since the modelling outputs are strongly dependent on input data, the material parameters in particular, the precision of these measurement together with a consistency and stability of the mathematical model used play an important role in the reliability of results produced. This paper therefore aims at sensitivity analysis of a selected diffusion mathematical model on the second Fick's law basis, that is used for a description of radionuclides transport (90Sr) in an existing radioactive waste repository concept when a hypothetical accident is assumed. Within the sensitivity analysis, the parameters of particular materials involved in the repository concept are varied by 10% which corresponds to common measurement uncertainties. The results provided by the model showed very low deviations as the envelope curves differed by up to 10.5%. Such a difference can be considered as a sign of very good model consistency, especially in the light of the logarithmic axis used for the radionuclide concentration plotting and very rough time axis that covers a period of 2000 years. Such factors, in general, do not require an increased precision and mathematical model analyzed was proved to be precise enough to be applied in further research in this field. [ABSTRACT FROM AUTHOR]

In this paper an advanced stochastic approach based a lattice rule with improved generating vector has been obtained and studied. The Unified Danish Eulerian Model (UNI-DEM) is a key element in our investigation since it is one of the most advanced large-scale mathematical models that describes adequately all physical and chemical processes. The calculations are done in a large spatial domain, which covers completely the European region and the Mediterranean, for certain time period. What is more, it studies the transportation of a number of pollutants and all these make it a perfect case study. The paper compares the described lattice rule and demonstrates its superiority over the plain Monte Carlo approach and Fibonacci based lattice rule. The proposed approach is robust and computationally efficient in estimating multidimensional integrals and thus sensitivity indices, which is vital in scientific computing. [ABSTRACT FROM AUTHOR]

Rudder is one of a primary flight control surface of an aircraft and have the function as directional control and directional trim. For multi-engine aircraft, critical function of the rudder is to be able to maintain aircraft direction in case of one engine inoperative. Due to aerodynamic load, the higher rudder deflection the higher hinge moment acting on the rudder. For the aircraft equipped with mechanical control system, load on the rudder can be feel by the pilot on the pedals. Excessive load received by the pilot in long duration of operation can make tired the pilot. Maximum load on the rudder allowed by regulation in VMCG with OEI is limited to 150 lbf. Current design of the rudder still produce load higher than limit value, even aerodynamic balance e.g., servo tab and rudder horn has been implemented. Sensitivity study of rudder horn balance was carried out to improve rudder hinge moment to reduce pedal force. This study was conducted by means wind tunnel testing in the NLST in Bandung, West Java. 6 rudder horn balance model was tested, the result are compared including basic or current horn design. Horn 8 provide the best result compared to basic horn and other modified horn, it is meet requirements both for load limit of 150 lbf and safety aspect. [ABSTRACT FROM AUTHOR]

Advanced stochastic approaches have been applied to perform variance-based sensitivity analysis (SA) of a particular air pollution model – the Unified Danish Eulerian Model (UNI-DEM). The following stochastic approaches for estimating sensitivity indices (SIs) are in the focus of our current study: algorithms based on optimal shifted Sobol' sequences, the van der Corput sequence (VDC), the Fibonacci based lattice sequences and a highly efficient optimal lattice rule. A comprehensive study of the behaviour and the efficiency of these algorithms to the large-scale model under consideration has been provided. [ABSTRACT FROM AUTHOR]

Cockpit temperature controlsystem requires maintaining the supply air temperature from the Air Cycle Machine (ACM) to havecomfortable condition inside the cockpit. The cockpit supply air temperature is influenced by many factors like bleed air flow & its rate of change, ambient condition and the attitude of the aircraft. In order to effectively design these sub systems, system simulation model has been created in AMESim. After validating the model for various static and dynamic cases in previous work, the model is then studied for sensitivity for various input and external factors. The results of the same are presented in this paper. From this analysis, the performance of ECS is studied and found that the system meets all the flight and environmental operating requirements. [ABSTRACT FROM AUTHOR]

In this paper for the first time a Hammersley and van der Corput sequences comparison for multidimensional sensitivity analysis has been done. Sensitivity analysis of model outputs to variation or natural uncertainties of model inputs is very significant for improving the reliability of these models. By definition, sensitivity analysis is a procedure for studying how sensitive are the output results of large-scale mathematical models to some uncertainties of the input data. The algorithms for multidimensional sensitivity analysis are applied to compute global Sobol sensitivity measures corresponding to the influence of several input parameters on the concentrations of important air pollutants. A deep experimental investigation is done to demonstrate the pros and cons of both approaches in the case study of the considered model. [ABSTRACT FROM AUTHOR]

A number of numerical experiments with a large-scale air pollution model (Unified Danish Eulerian Model, UNI-DEM) have been carried out to compute Sobol sensitivity measures. Sensitivity analysis of ozone concentrations according to variations of rates of chemical reactions is developed. The sensitivity study has been done for the areas of four European cities (Genova, Milan, Manchester, and Edinburgh) with different geographical locations. Sensitivity analysis of the output of UNI-DEM according to emission levels is also provided. The influence of emission levels on the concentrations of four important air pollutants (ammonia, ozone, ammonium sulphate and ammonium nitrate) over three European cities (Milan, Manchester, and Edinburgh) is considered. Variance-based methods are most often used for providing sensitivity analysis. Sobol variance-based approach for global sensitivity analysis has been applied to compute the corresponding sensitivity measures. Advanced stochastic methods based on modified Sobol sequences are used for computing the sensitivity measures. The numerical experiments show that the stochastic algorithms for the multidimensional integrals under consideration are one of the best stochastic techniques for computing the small in value sensitivity indices. [ABSTRACT FROM AUTHOR]

Presented is a mathematical model that outlines the population dynamics of Prymnesium parvum, a species of phytoplankton commonly referred to as golden algae. This phytoplankton is understood to exhibit dormancy. It can reside in either an active-motile or dormant-non-motile state. Far-reaching ecological processes, such as nutrient recycling, can also impact the population dynamics of golden algae. Thus, this model incorporates dormancy and nutrient recycling for further accuracy and complexity. Included is a complete stability and sensitivity analysis with supporting phase plane portraits. A set of numerical simulations is also provided to support the theoretical results. [ABSTRACT FROM AUTHOR]

The paper deals with the analysis of the current condition of the issue of independent wheel suspension of passenger cars and describes the foremost characteristics of wheel geometry. The current practice of manufacturing companies is proposed in such a way that in order to speed up the development on the one hand and to prepare a reliable product on the other hand, R&D departments try to comprise predictive simulations at the early stage of development. By dint of these simulations, they are able to numerically predict the dynamic behavior of vehicles in an extremely short stretch of time ahead of the real prototype production. Therefore, the presented paper likewise provides a description of an advanced simulation tool for MBD simulations, namely the Altair Motionview software. Furthermore, the authors present a selected reference vehicle, the Alfa Romeo 156. On the basis of the measurements performed, the important geometrical parameters of the reference vehicle were compiled, which are indispensable for the creation of the numerical model in the Motionview graphical environment. The made up model is functional, ready for producing analyses of sensitivity of the change in wheel camber depending on the vertical change in axle position. It will be possible to examine the behavior of structurally different front axle models, which will be created in the software and compared with simulations of the Alfa Romeo 156 model. [ABSTRACT FROM AUTHOR]

A sensitivity analysis of moving packed-bed heat exchanger models is presented. A heat exchanger symmetric half-plate geometry based on the Gen 3 Particle Pilot Plant (G3P3) is meshed and solved using a conjugate heat transfer model. Seven independent variables are sampled at random within prescribed limits and the model is run for up to 64 different combinations of the input parameters. The overall heat transfer coefficient is output for each simulation and the Sobol index is calculated and used to compare sensitivity levels of the inputs. The analysis is performed in two parts to provide insight from both an overall design and optimization perspective in addition to an operational standpoint for an existing heat exchanger. The first key finding is that the overall heat transfer coefficient sensitivity is almost entirely dominated by the particle channel width. The second insight is that for an existing heat exchanger where the geometric parameters are fixed, the overall heat transfer coefficient prediction still has a significant level of uncertainty that can be limited by better characterizing the packed-bed void fraction. [ABSTRACT FROM AUTHOR]

The transforming rainfall into discharge is a fairly complex phenomenon. The complexity is related to many factors that influence the rainfall-runoof transformation. Modelling watershed as a system for transforming volume runoff into hydrograph has a lot of uncertainty especially for ungagged watershed where there is no hydrograph data. This problem encourages the analysis of sensitivity watershed morphological parameters to the accuracy of the hydrograph of the geomorphological instantaneous unit hydrograph (GIUH) method using the Geographic Information System (GIS). Watershed Modeling System (WMS) 11.1 and Arcmap 10.4 used for physical analysis of watershed. The Nash model and curve S method were used to convert the triangular GIUH into IUH and UH, then compared with the observed UH using the Collins method. Parameter sensitivity analysis includes time concentration (Tc), stream length ratio (RL), stream area ratio (RA), bifurcation ratio (RB) and Nash model k parameters. The results showed that the GIS approach for modelling the Oyo watershed physical parameters could be easily carried out. The comparison of the measured unit hydrograph and the GIUH hydrograph based on time of concentration of modified Kirpich formula shows that Qp, RA, RBRL, k has error percentage of 14.8%, 8.24%, 8.58%, 8.34% and 14.68%, respectively. This inaccuracy occurs due to the limited number of flood events used to derive the observed UH and tributary modelling which is not the actual condition in the watershed. Further research is needed for calibration and verification, especially in watershed delineation so that the physical parameters of the watershed can mimic to the actual conditions. [ABSTRACT FROM AUTHOR]

This paper investigates the surface roughness and temperatures generated during metal machining processes such as lathe and orthogonal turn-mill operations on the most commonly used domestic material AISI 304 stainless steel. Grey relational analysis (GRA) is a tool for multi-response optimization that can be used in conjunction with the Taguchi approach is used for multi-response optimization. Furthermore, a sensitivity analysis utilizing regression models is performed to cross-check the consistency of GRA optimality with modifications in machining parameter levels. Use of sensitivity analysis resulted in much-finer machining parameter combinations for superior responses in environmentally friendly (dry and aerosol-mist conditions) machining in both the processes. [ABSTRACT FROM AUTHOR]

Shuaiba dome in the Zubair oil field demonstrated from the performance data a very high challenge of wellbore instability problem and these hole trouble caused increased in NPT non-productive time. This study can assist in developing management of the drilling wells with the least amount of non-productive time and more effectively for design wells. To achieve the goals of this study, a one-dimensional (1D) mechanical earth model was constructed. Gamma ray (GR), bit size, caliper log (CALI), density log, sonic compression log (DTCO), and sonic shear log (DTSM) are some of the logs that were used to build this model. Vertical stress, pore pressure, mechanical characteristics of the rock, and horizontal stress (max and min) were the components of the 1D model that were measured. The fundamental laboratory tests (Brazilin and Triaxle), repeated formation test, and minimum frac test are used to calibrate these results. The well bore stability study was then performed at real mud weight using three failure criteria (Mohr-Coulomb, Mogi-Coulomb, and Modified lade). These criteria were evaluated using caliper logs, which revealed that the optimum failure criteria is Mogi-coulomb. Ultimately, sensitivity analysis and new stability analysis are done to establish the most stable well trajectory and safe mud weight for future wells that may be drilled. The wellbore stability study results suggest that azimuth has no influence on mud window, however inclination more than 30 degrees causes the mud window to narrow. Azimuth 140 degrees is preferred for drilling wells because it is parallel to the minimum horizontal stress. In Shuaiba dome, drilling wells with an inclination of less than 40 degrees and mud weight between 12 and 12.8 ppg is successful, however drilling wells with an inclination of more than 50 degrees is unsuccessful. [ABSTRACT FROM AUTHOR]

Wellbore instability is the main problems that faced through drilling operations such as kick or blowout, stuck pipe and lost circulation which takes extra time to treatment, also increase time of nonproductive and expenditure of well drilling. The purpos of study is constructed one dimensional geomechanical model for Eridu oilfield by using open hole log measurements such as(Density, Sonic compression and Shear wave velocities, Gammaray, Caliper, and Bit size). These logs are incorporated into the software for computing componts of 1D-MEM (Rock mechanical characteristics, pore pressure, in-situ stress magnitudes and orientations). these parameters calibrate with field measurements tests such as repeated formation pressure,hydraulic fracturing and labatory core testing. Then validate the model by coupling with several failure criteria such as (Mogi Coulomb, Modified Lade and Mohr Coulomb) to detected best failurea criteria. The results showed the most suitable failure criterian for Eridu oilfield is Mogi Coulomb. The results of sensitivity stability analyses appeared the value of safe mud weight window was 10.5 ppg and become narrow with deviation higher than 35 degree, while breakout mud weight didn't had affected by wellbore azimuth becouse contrast of low-stress. Furthermore, to prevent shear failure should be drilling with inclination less than 35 degree and to prevent breakdown should be drilling with inclination between (25-65) degree both, in direction of mini-horizontal stress. These outcomes could be used to prevent wellbore instability occur and determine appropriate mud weight window when planning to drill nearby wells in future. Also, to achieve better drill effectiveness and use as cost-effective tools. [ABSTRACT FROM AUTHOR]

Several recent studies have revealed, that the structural resistance of stainless steel members under compressive loading determined in accordance with the current European standard does not satisfy sufficiently small level of failure probability. It has been observed, that currently utilized flexural buckling curves overestimate the ultimate structural resistance of stainless steel members of certain material grades and cross-sectional geometries. Not negligible differences have been achieved between the estimations based on standards and experimental data, mainly for specific range of member slenderness values. Compared to carbon steel, stainless steel has higher ductility, and in order to properly describe the stress-strain material behavior, higher numbers of material parameters are required. The subject of this article is to closely investigate the influence of these parameters (material, cross-sectional geometry and also parameters to describe global imperfection) on the ultimate resistance of the members exposed to flexural buckling. Previously validated numerical finite element models of the circular hollow cross-section (CHS) members are created in ANSYS Classic software utilizing parametric APDL macros. Statistical characteristics of all the input parameters along with their mutual correlations are obtained from recent comprehensive statistical research study. The sensitivity analysis is conducted for three different material grades of stainless steel: Austenitic, grade 1.4307, Ferritic 1.4003 and Duplex 1.4462, and for various values of the member slenderness. The purpose of the numerical models is to determine the ultimate limit state of the CHS members exposed to compressive loading utilizing geometrically and materially nonlinear analyses with initial geometrical imperfections. Influence of each input parameter on the model output (ultimate resistance) is investigated, and the results are well documented and discussed. The sensitivity analysis reveals, which of these parameters have the highest influence on the structural resistance, hence are the most significant for the monitored output, considering their statistical distribution and value range. Study also provides data for the subsequent optimization process of the flexural buckling curves, which can be feasibly conducted utilizing the first order reliability method. [ABSTRACT FROM AUTHOR]

Sensitivity analysis is a tool for measuring how the conclusion drawn from a model depends on changes in the parameters that enter it. Research on probabilistic reliability analysis in engineering disciplines shows that simply focusing on the model output is not sufficient. In stochastic models, the correlation between input and output, output variance analysis and other methods oriented only to model output are not directly related to reliability, which is one of the main objectives of structural design. The presented article provides a brief history on the development of sensitivity analysis methods, starting with methods oriented to model outputs and ending with the global sensitivity analysis of reliability oriented to the probability of failure or design quantiles. In the next part of the article, a case study examining the influence of loading, material and geometric characteristics on the probability of failure of a steel bar with a thin-walled closed cross-section subjected to torsion is presented. Sensitivity analysis is performed using two sensitivity measures that measure changes in the probability of failure due to changes in input variables. There are large differences between the proportion of first-order and higher-order sensitivity indices. Although the results of the sensitivity analysis are not the same, both sensitivity measures give similar values of total sensitivity indices and infer the same sensitivity ranking of the input variables. [ABSTRACT FROM AUTHOR]

The analysis of the influence of random initial imperfections on the static resistance of a hot-rolled steel beam with IPE cross-section is presented in the article. The resistance of the investigated IPE beam is exposed to the effects of lateral-torsional buckling resulting from the bending moment acting about its major principal axis. The resistance of the hot-rolled steel beam is studied using global sensitivity analysis. Initial geometrical and material imperfections are considered as random variables in the determination of the variability of the resistance. The SHELL finite elements and geometrical and material non-linear computational methods of the ANSYS software are used for the evaluation of the resistance. Sensitivity analysis is used to examine the influence of initial imperfections and residual stresses on the resistance (model output). The variance of the model output is evaluated using the Latin Hypercube Sampling method. The sensitivity order of the imperfections based on their influence on the resistance is then determined in the presented case study. [ABSTRACT FROM AUTHOR]

Several recent studies have revealed, that the structural resistance of stainless steel members under compressive loading determined in accordance with the current European standard does not satisfy sufficiently small level of failure probability. It has been observed, that currently utilized flexural buckling curves overestimate the ultimate structural resistance of stainless steel members of certain material grades and cross-sectional geometries. Not negligible differences have been achieved between the estimations based on standards and experimental data, mainly for specific range of member slenderness values. Compared to carbon steel, stainless steel has higher ductility, and in order to properly describe the stress-strain material behavior, higher numbers of material parameters are required. The subject of this article is to closely investigate the influence of these parameters (material, cross-sectional geometry and also parameters to describe global imperfection) on the ultimate resistance of the members exposed to flexural buckling. Previously validated numerical finite element models of the circular hollow cross-section (CHS) members are created in ANSYS Classic software utilizing parametric APDL macros. Statistical characteristics of all the input parameters along with their mutual correlations are obtained from recent comprehensive statistical research study. The sensitivity analysis is conducted for three different material grades of stainless steel: Austenitic, grade 1.4307, Ferritic 1.4003 and Duplex 1.4462, and for various values of the member slenderness. The purpose of the numerical models is to determine the ultimate limit state of the CHS members exposed to compressive loading utilizing geometrically and materially nonlinear analyses with initial geometrical imperfections. Influence of each input parameter on the model output (ultimate resistance) is investigated, and the results are well documented and discussed. The sensitivity analysis reveals, which of these parameters have the highest influence on the structural resistance, hence are the most significant for the monitored output, considering their statistical distribution and value range. Study also provides data for the subsequent optimization process of the flexural buckling curves, which can be feasibly conducted utilizing the first order reliability method. [ABSTRACT FROM AUTHOR]

Sensitivity analysis is a tool for measuring how the conclusion drawn from a model depends on changes in the parameters that enter it. Research on probabilistic reliability analysis in engineering disciplines shows that simply focusing on the model output is not sufficient. In stochastic models, the correlation between input and output, output variance analysis and other methods oriented only to model output are not directly related to reliability, which is one of the main objectives of structural design. The presented article provides a brief history on the development of sensitivity analysis methods, starting with methods oriented to model outputs and ending with the global sensitivity analysis of reliability oriented to the probability of failure or design quantiles. In the next part of the article, a case study examining the influence of loading, material and geometric characteristics on the probability of failure of a steel bar with a thin-walled closed cross-section subjected to torsion is presented. Sensitivity analysis is performed using two sensitivity measures that measure changes in the probability of failure due to changes in input variables. There are large differences between the proportion of first-order and higher-order sensitivity indices. Although the results of the sensitivity analysis are not the same, both sensitivity measures give similar values of total sensitivity indices and infer the same sensitivity ranking of the input variables. [ABSTRACT FROM AUTHOR]