Papers by Keyword: Uncertainty

Abstract: Flow forming of metastable austenites is an innovative, incremental metal forming process with special capabilities due to the TRIP effect. However, the TRIP effect during flow forming is significantly affected by disturbances and especially batch fluctuations leading to process uncertainty. This aspect is further analyzed and quantified in this paper to give insights on how to minimize the impact of uncertainty. For this purpose, semifinished parts and resulting flow forming workpieces are systemically characterized concerning their properties and the property uncertainty supported by mathematical methods like correlation analysis and error propagation. A result is that the most influencing impact factor on the strain induced α’-martensite volume fraction as a material property are batch fluctuations, specifically the variations of the chemical composition. Those especially appear from batch to batch, but also within a batch accompanied by e.g. temperature effects. To counter this challenge, different methods from control theory like closed-loop property control and adaptive control can be applied to flow forming. Thus, uncertainty will be reduced to increase process robustness and to enable industrial exploitation of the TRIP effect in flow forming of metastable austenitic steels.

Abstract: In this study, distributed generators (DGs) based on renewable energy sources (RESs), besides capacitor banks are optimally allocated in power distribution networks with a proposed multi-objective optimization approach. The proposed approach is used to maximize the hosting capacity (HC) of RES DGs besides decreasing energy loss and voltage deviation in power networks. Uncertainties of load demand and RESs are considered. To facilitate the optimization processes, reduction criterion is utilized for reducing the numerous numbers of uncertain data. The proposed approach is applied to practical and standard power networks for many cases under the uncertain scenarios. Comparative study with other algorithms is performed and robustness of proposed approach is verified in long-term dynamic environment. Also, impacts of changing parameters values on performance are investigated. Additionally, Wilcoxon statistical tests are applied with the proposed approach. Also, comparative study is carried out between weighted sum and Pareto front techniques. Results reveal efficacy of the proposed approach with distribution power networks.

Abstract: In the shipping industry, the measurements of the weights are also important as all the cargo weighs tons. cargo carried in a cargo unit shall be so packed and secured within the unit as to prevent, throughout the voyage, damage or hazard to the ship and the persons on board. Appropriate precautions shall be taken during the loading and transport of heavy cargoes or cargoes with abnormal physical dimensions to ensure that no structural damage to the ship occurs and to maintain adequate stability throughout the voyage. This report describes the results of the bilateral supplementary comparison COOMET.M.M-S4 The comparison measurements between the two participants Czech Metrology Institute (CMI) (pilot laboratory) and Azerbaijan Institute of Metrology (AzMI) were started. The transfer standards were OIML Class E2 standard weights with nominal mass values of 5 kg, 500 g, 20 g, 2 g and 100 mg. Agreement between the two participants is good.

Abstract: In this article, the evaluation of the behavior of a gravity retaining wall is analyzed by considering different modeling approaches. The influence of taking into account the spatial variability of soil parameters in modeling approaches on the response of a retaining wall, assessed through horizontal displacements behind the wall and vertical displacements at the base of the wall. The displacements were evaluated with the finite element software CESAR, developed by the Central Laboratory of Bridges and Roads in France (LCPC), and the statistical analysis of the results was performed with Microsoft Excel. The results indicated that the effects of modeling the soil as a heterogeneous case on the wall displacements were much more significant than when the soil is modeled considering the statistically homogeneous case or the analysis case of a multilayer. This influence of the modeling of the soil as being totally heterogeneous is expressed through the lower standard deviations of the displacements, and also through the narrowness of the band defined by the maximums and the minimums of the results of the displacements, with respect to the two other modeling cases. This result leads towards a gain in terms of accuracy of the results, considering the spatial variability of the soil parameters in both directions, horizontal and vertical.

Abstract: Capacity planning is the process of determining the production capacity needed by an organization to meet changing demands for its products. Production capacity planning is generally based on all capabilities determining that wireless production is stable, with no fluctuations in machine downtime, variable processing times, defective products, etc., and use the mean for cycle time. However, actual production not only has many fluctuations in human resources that affecting the production time on each stage, but also affected by defective products leading to inaccurate planning. Therefore, planning production capacity under uncertain conditions is essential for any manufacturing enterprise. This paper proposes a model of capacity planning in uncertain conditions using real-time observation and then distributing observation time from which to analyze production capacity. Uncertainty factor as labor and defective products will be considered in this model.

Abstract: The increasing penetration of RES and the intermittent nature of various distributed power generation (DG) resources have created uncertainty in variable power production and power systems. The overall energy output of a wind farm may be optimized by strategically positioning wind turbines. This paper proposes a three-step strategy to dealing with the difficult-to-control problem of wind farm layout optimization. To construct the non-wake and wake impacts at various levels, three case scenarios are studied. The proposed strategy is used to a particular Ant-Lion Optimization Algorithm (ALOA) as a novel approach to producing highly efficient optimal output power, as well as case studies using actual wind data assessing potential turbine site. Finally, the simulation results demonstrate that the suggested approach is robust in ALOA design because it further reduces the objective function on the best new outcomes to implement all network restrictions acquired via the analysis.

Abstract: Thermal conductivity is of high importance for insulating materials since it strongly influences the thermal performance of the building. Generally, it is recommended to measure this property with steady-state methods like guarded hot plate (GHP) or heat flow meter (HFM). These methods are reliable, but steady-state condition can take a long time to be reached. Therefore, transient methods were developed to speed-up the measurements. For instance, the hot disk transient plane source method is a widely used standard technique (ISO 22007-2) for measuring thermal conductivity of various materials. In the last 20 years, this technique has been applied also to bio-based insulating materials. However, overestimated thermal conductivity (compared to steady state method) are frequently measured. More generally, such differences are also observed for low thermal conductivity materials. The aim of this work is to evaluate the influence of numerous factors to explain the origin of these differences. The factors include the experimental setting parameters, the measurement analysis parameter or even the discrepancies between the theoretical model and the real experimental set-up. The analysis is performed for a light-earth biobased concrete made of raw earth and hemp shiv. Recommendations are proposed in conclusion.

Abstract: It is evident that the response of linear structures under dynamic loads depends to two important dynamics parameters of structures, namely, the natural periods and structural damping. These parameters always characterize the oscillation and the energy dissipation of buildings. In fact, the values of these parameters differ significantly, before, during and after an earthquake from values selected during the design phase. This phenomenon, among other, introduces uncertainty into the building simulation process, which remarkably influences the structural response and associated performance of the structure under dynamic loads. This paper develops a new methodology to estimate the maximum absolute response for linear structures with uncertain damping using the Artificial Neural Networks (ANN) and the Monte Carlo method. The proposed method is illustrated using the target design response spectra corresponding to the EC8 for linear structures exposed to seismic loads. The numerical results revealed the practical applicability of the proposed methodology and the crucial influence of accounting the damping uncertainty in structural dynamics. Additionally, the method can be used in practice, mainly for important and special structures where uncertainty could lead to significant changes in structural response.

Abstract: The validation method for determination of chemical oxygen demand (COD) with indirect UV-Vis spectrometry have been done. This method enable to easily perform highly sensitive, considerably faster and easier, and minimize the use of digestion solution. This method is the development of standard method of COD determination by closed reflux using UV-Vis spectrometry so it requires the method validation stage. The validation is used to ensure linearity, limit of detection, limit of quantification, precision, and accuracy values in accordance with quality control. This study was also carried out to formulate the uncertainty calculation modeling of COD on water analysis. The result of validation method show that the calibration curve linearity is 0.9994 with the linear regression equation Y = 0.0003X + 0.0005. The method is able to have high sensitivity in measuring COD value with low concentrations with limit of detection and limit of quantitation of 9.78 and 32.59 mg O₂/L. Indirect UV-Vis spectrometry has high precision with relative standard deviation of 0.66% and high accuracy with the percentage of recovery of 91.35%. The uncertainty formulation model on determination of COD from the source of standard uncertainty of sample volume, calibration curves, and repeatability.

Abstract: For the multiscale damage behaviour simulation of advanced materials with hierarchical and random heterogeneous microstructures such as fibrous composites by finite element method, the mathematical homogenization method has been extended to the stochastic nonlinear multiscale method. A first-order perturbation based stochastic homogenization method was developed to calculate the microscopic strain, as well as the homogenized macroscopic properties considering randomness in the mechanical properties of constituent materials. Based on the calculated stochastic microscopic strain, the damage simulation framework was proposed for fibrous composites. For a demonstrated application, a numerical example of a single short fiber reinforced plastic composite was carried out. The damage propagation in the interphase between fiber and matrix was predicted in a stochastic way considering the physical random parameters for the interphase material model. The influences of the randomness on damage volume fraction and damage propagation of the interphase were discussed.