Prediction Of Long-term Behavior Research Articles

Rheological Characteristics of the Rock Salt from Slanic Prahova, Horizon XIV Below Level of 200m

Abstract The long-term response and stability of underground mining works are crucial for ensuring the safety of workers, preventing costly accidents, and maintaining efficient operations. This is primarily due to the critical role these structures play in various industries, including mining, construction, and transportation. Understanding the long-term response and stability of such structures is an important factor for ensuring their durability and safety. Additionally, advancements in technology and engineering practices have allowed for more accurate assessments and predictions of long-term behaviour, leading to improved design and maintenance strategies. By examining the creep and relaxation behaviour, scientists can gain insights into the mechanical properties and stability of rocks under different conditions. The time-dependent experiments involve subjecting the rocks to varying rates of loading or deformation to understand their behaviour under different conditions. These methods provide valuable insights into the time-dependent properties of rocks, allowing researchers to better understand their response to various geological processes and engineering applications. This study was carried out in order to determine the rheological characteristics of the rock salt from Slanic Prahova mine, horizon XIV, and to analyse the local stability and the general stability of the resistance structures. The results of the experimentally determined rheological characteristics showed that the analysed salt has a pronounced tendency to creep, being able to be classified in creep category 5, which is a pronounced creep. The values obtained for the dilatancy threshold confirm the fact that salt is a material system that exhibits dilatancy.

Cure-dependent loading rate effects on strength and stiffness of particle-reinforced thermoset polymers

Thermoset polymers are widely used in the civil engineering field, especially as adhesives, coatings, and matrices for composite materials. During the in-situ application of these materials, thermal activation is typically not possible, resulting in an undefined curing state of the system, which depends on the reaction kinetics and ambient conditions. These resins can also react at low temperatures; however, a certain amount of time is needed to reach a fully cured state. This characteristic complicates the assessment of the mechanical properties and the prediction of long-term behavior. In this work, primarily the loading rate effect on strength is analyzed for different curing states, which are derived from relevant in-situ conditions while also the effect of stiffness is discussed. The degrees of cure have been assessed by means of DSC measurements after submitting the samples to specific curing and post-curing protocols. Two products, one epoxy-based and one vinyl ester-based, have been studied. The tensile strength of these materials was characterized at various loading rates, monitoring the strain using digital image correlation (DIC). The results reveal that the loading rate effect on strength and stiffness strongly depends on the polymer’s curing degree. Finally, simplified models able to describe the dependencies between the degree of cure of the thermosets and the rate effects on strength and stiffness are proposed as an essential element for realistic numerical simulations of incompletely cured thermosets in real world applications. • The post-curing of thermoset polymers leads to improved mechanical properties. • Epoxy with a high degree of cure presents a more ductile behavior. • The rate effect on strength and stiffness depends on the curing of the thermoset. • The loading rate effect increases with the degree of cure of the thermoset for the epoxy. • The loading rate effect decreases with post-curing treatments for the vinyl ester.

Long-Term Behavior Prediction of HDPE Containing Postconsumer Recycled Material Using Stepped Isostress Method

Long-Term Behavior Prediction of HDPE Containing Postconsumer Recycled Material Using Stepped Isostress Method

A hybrid approach for prediction of long-term behavior of concrete structures

A hybrid approach for prediction of long-term behavior of concrete structures

Moment approximation of individual-based models. Application to the study of the spatial dynamics of phytoplankton populations

The objective of this paper is to analyze the efficiency of a spatial moments model (SMM) in approximating an individual-based model (IBM) dedicated to the study of the aggregation phenomenon in a phytoplankton population. The dynamic system of spatial moments consists of a system of integro-differential equations derived from a phytoplankton IBM. The later is built on the basis of stochastic processes describing the dynamics of phytoplankton cells and their interactions. These processes are: (1) the movement of cells, which takes into account the random dispersion of cells in water and the attraction between cells due to their chemosensory abilities, (2) the demographical process (cell division or cell death) in which, the effect of local competition for nutrient resources on the cell’s division process is taken into account through the use of density dependent division rate.We solve numerically the SMM and then simulate the two models (IBM and SMM), for a set of scenarios chosen to analyze the aggregation and the different interactions in the population. The numerical results have led to the conclusion that in contrast to the mean-field model (MFM), the method of spatial moments is efficient to capture the dynamics of the IBM. Further, the SMM easily permits the prediction of long term behavior of phytoplankton cells and their spatial structure, namely that the aggregation behavior of the cells is very much related to their cellular diffusion and the perceptual radius.Concerning competition on resources, this process has a short and medium-term effect on aggregation, since regardless of its intensity, in the long term the population tends to be stable with formation of aggregates, as a result of the equilibrium between different mechanisms, including reproduction, competition, diffusion and cells attractions due to chemosensory abilities.

Structure Monitoring and Long-Term Behavior Prediction of Wall-Piloti Structure

In Korean residential building, wall – piloti structures have been frequently used in the ground floor. For cost-effective design, a new wall – piloti structure where the walls are directly connected with the columns without transfer girder was suggested in the previous study. In this study, the proposed structure was applied to actual residential building. To verify the structure safety, structural monitoring and long-term behavior prediction was carried out. Strain gauge and displacement meters was installed to measure the strain of re-bars and the deflection of slab. During the construction period, in all wall – piloti structures, compressive strain was less than the allowable strain and relative deflection of slab satisfied the serviceability criteria. Further, in the long-term behavior, the maximum vertical strains of the re-bar were less than allowable strain under the service load condition.

Ageing of Dental Composites Based on Methacrylate Resins-A Critical Review of the Causes and Method of Assessment.

The paper reviews the environmental factors affecting ageing processes, and the degradation of resins, filler, and the filler-matrix interface. It discusses the current methods of testing materials in vitro. A review of literature was conducted with the main sources being PubMed. ScienceDirect, Mendeley, and Google Scholar were used as other resources. Studies were selected based on relevance, with a preference given to recent research. The ageing process is an inherent element of the use of resin composites in the oral environment, which is very complex and changes dynamically. The hydrolysis of dental resins is accelerated by some substances (enzymes, acids). Bonds formed between coupling agent and inorganic filler are prone to hydrolysis. Methods for prediction of long-term behaviour are not included in composite standards. Given the very complex chemical composition of the oral environment, ageing tests based on water can only provide a limited view of the clinical performance of biomaterial. Systems that can reproduce dynamic changes in stress (thermal cycling, fatigue tests) are better able to mimic clinical conditions and could be extremely valuable in predicting dental composite clinical performance. It is essential to identify procedure to determine the ageing process of dental materials.

Prediction of Long-Term Behavior for Dynamically Loaded TPU

Prediction of Long-Term Behavior for Dynamically Loaded TPU

Experimental investigation on effects of track configurations on long-term behavior of ballasted track

ABSTRACTThe track settlement causes the deterioration of track geometry structure. Analysis of track settlement is a significant condition for determining the maintenance cycle. The long-term behavior of ballasted track may vary depending on the combination of the track configurations. In the present study, four ballasted tracks are studied through full-scale experiments to evaluate their respective performance in terms of track settlement. A load condition simulating a vehicle speed of 230 km/h is applied to the ballast tracks with a cyclic load of up to 1.5 million cycles. The long-term behavior prediction equations for the ballasted tracks used in Korea are presented in this study. The size of the sleeper and the thickness of ballast are analyzed to be the most influential track configurations for the long-term behavior of ballasted track. Results of the full-scale test showed that the effective area between ballast and subgrade is related to the long-term behavior of ballasted track. The track settlement decreases as the effective area between ballast and subgrade increases. Therefore, it is necessary to properly consider the effective area of the sleeper and the ballast thickness to inhibit the track settlement.

Theoretical evaluation of the interaction between C5-PFK molecule and Cu (1 1 1)

C5-PFK has drawn much attention in recent years as an environmental friendly gas-insulated medium. Many studies have proved that it has the potential to replace SF6 using in medium voltage electrical equipment. However, there are few reports about the compatibility between C5-PFK and materials used in the gas-insulated switchgear. C5-PFK may react with materials such as metal inside the equipment due to the strong activity of carbonyl group (C = O) in its molecular structure. Investigations about the material compatibility between C5-PFK and the materials are required to decide about a long term behavior. In this paper, the interaction between C5-PFK and copper, a common metallic material in electrical equipment, is discussed based on the density functional theory. We found that the interaction between the O atom in the C5-PFK molecule and Cu (1 1 1) surface is strong. The interaction between F atom and Cu (1 1 1) surface is weak, which belongs to physical adsorption. Relevant results not only clarify the compatibility between C5-PFK and copper but also provide guidance for prediction of long-term behavior of C5-PFK gas mixture and the selection or modification of materials used in the equipment.

Natural analogue approaches to prediction of long-term behaviour of Ca2UO5∙2-3H2O X-phase: case study from Tulul Al Hammam site, Jordan

The Tulul Al Hammam area in central Jordan is an advantageous natural analogue site to study long-term U(VI) retention in ~ 1 Ma old U-bearing combustion metamorphic marbles with clinker-like mineralogy exposed to prolonged supergene alteration for at least ~ 100 kyr. The marbles contain abundant grains of high-temperature (ca. 800–850 °C) primary double Ca-U(VI) oxides (mainly Ca3UO6 and CaUO4), which are commonly replaced by hydrated calcium uranates with various impurities (Si, Fe, Al and F). A more hydrous natural analogue of X-phase (Ca2UO5·2-3H2O) occurs as a predominant secondary U compound after primary Ca-U(VI) oxides. The phase was studied by single-crystal XRD, SEM/EDX and electron microprobe (EPMA) analyses and Raman spectroscopy. It is a non-crystalline phase with a specific finger-like microtexture consisting of thin (no wider than 1–2 μm) lamellar particles. Its Raman spectrum shows a single strong band at 706–713 cm−1, sometimes coexisting with up to three weak diffuse bands (ν ~ 390, ~ 540 and 1355–1400 cm−1). The find of the natural X-phase (Ca2UO5·2-3H2O) is evidence of its long-term stability in a natural environment. It proves explicitly that the compound Ca2UO5·nH2O is a solubility-limiting phase in aged cements. The results have implications for geological disposal of radioactive wastes.

Convex Parameterizations and Fidelity Bounds for Nonlinear Identification and Reduced-Order Modelling

Model instability and poor prediction of long-term behavior are common problems when modeling dynamical systems using nonlinear “black-box” techniques. Direct optimization of the long-term predictions, often called simulation error minimization , leads to optimization problems that are generally nonconvex in the model parameters and suffer from multiple local minima. In this paper, we present methods which address these problems through convex optimization, based on Lagrangian relaxation, dissipation inequalities, contraction theory, and semidefinite programming. We demonstrate the proposed methods with a model order reduction task for electronic circuit design and the identification of a pneumatic actuator from experiment.

Extreme event characterization for the river basins of Eastern Indian Gangetic Plains

Abstract The Eastern Indian Gangetic Plains are characterized by a primarily nature-dependent region blessed with an enormous supply of mineral resources. The region is witnessing a rapid transition in its demographic structure because of rapid industrialization. The region provides a classic example of an area which shows a trend reverse to that observed globally, as far as the frequency of extreme precipitation events is concerned. This paper provides a risk characterization of the entire region, based on the empirical behavior shown by data available so far, in addition to predictions based on theory of extreme values. The long-term behavior prediction is made with an aim to provide policy makers ample time and direction to develop suitable disaster prevention measures. The focus is primarily on extremely high rainfall events, their frequency, trend and estimated long-term behavior. The study corroborates the stability assumption behind the Indian monsoon, and also provides an indication of the expected long-term as well as short-term threats. This study provides a unique application of the extreme value theory to help in developing a threat map for a region whose population is known to be highly impacted by any significant deviations from a normal monsoon.

Prediction of Long-Term behavior of polyethylene pipe buried underground

Prediction of Long-Term behavior of polyethylene pipe buried underground

Nuclear Corrosion: Achievements and Challenges

Corrosion science faces new challenges in various nuclear environments. Three main areas may be identified where increases of knowledge and understanding have been done and are still needed to face the technical needs: (i) the extension of the service time of nuclear power plants from 40 years, as initially planned, to 60 years and probably more as expected now, (ii) the prediction of long term behaviour of metallic materials in nuclear waste disposal where the corrosion processes have to be predicted over large periods of time, some thousands years and more, (iii) the choice of materials for use at very high temperatures as expected in Generation IV power plants in environments like gas (helium), supercritical water, liquid metals or salts. Service time extension, deep geological waste repositories and high temperature reactors sustain researches and developments to model corrosion phenomena at various scales, from atoms to components.

The influence of natural trace element distribution on the mobility of radionuclides. The exemple of nickel in a clay-rock

The natural distribution of nickel (Ni) in the Callovian–Oxfordian clay-rich rock of Bure (France) was investigated, together with that of cobalt (Co), zinc (Zn) and lead (Pb). The most Ni-enriched phases are pyrite (∼400×10−6gg−1 Ni), sphalerite (∼300×10−6gg−1), chlorite (∼285×10−6gg−1), organic matter (∼300×10−6gg−1), muscovite (100–200×10−6gg−1) and possibly carbonate minerals (mainly calcite and minor dolomite, ∼10×10−6gg−1). Despite their high abundance (up to ∼80% in the upper part of the formation), carbonate minerals are quantitatively a minor Ni reservoir; most of the Ni is borne by chlorite and pyrite, which are minor mineral phases. Co and Ni have a similar distribution, whereas Pb and Zn have partly different reservoirs (e.g. sphalerite – ZnS).In parallel, the equilibrium between rock and pore water was investigated, and importance of pyrite (or reduced sulfur minerals) as Ni reservoir in the formation was confirmed from an in situ experiment perturbed by oxidation processes. Under unperturbed conditions (laboratory kinetics experiments and in situ pore water sampling), Ni solubility ranges from ∼0.2 to 1×10−6molL−1. The rock sorption capacities with regards to radioactive Ni (in the range of ∼1.5×10−10molL−1 to ∼1.5×10−9molL−1 of spiked 63Ni) were also tested using batch experiments. Sorption kinetics of 63Ni on the Callovian–Oxfordian clay-rich rock was explained by two mechanisms: fast and reversible sorption onto clay minerals and slow incorporation in another phase. Indirect evidences point out the likely major role of calcite in this latter process albeit pyrite and organic matter may also be involved. Reversible sorption of Ni onto clay minerals surfaces is shown to be hindered by competition processes with other naturally occurring bivalent metals (e.g. naturally-occurring Ni and Zn), thus decreasing the 63Ni Rd value as compared to the value predicted from a bottom-up approach considering only 63Ni sorption on clay minerals. At longer time scale, irreversible 63Ni trapping is observed and compensates the competition processes. These two mechanisms were implemented in a reactive transport model to illustrate their influence on the prediction of long-term behavior of radioactive Ni. Migration distances are increased by the effect of cation competition, and reduced in a comparable extent by irreversible trapping in the time frame investigated.

Failure analysis of the cement mantle in total hip arthroplasty with an efficient probabilistic method

Accurate prediction of long-term behaviour of cemented hip implants is very important not only for patient comfort but also for elimination of any revision operation due to failure of implants. Therefore, a more realistic computer model was generated and then used for both deterministic and probabilistic analyses of the hip implant in this study. The deterministic failure analysis was carried out for the most common failure states of the cement mantle. On the other hand, most of the design parameters of the cemented hip are inherently uncertain quantities. Therefore, the probabilistic failure analysis was also carried out considering the fatigue failure of the cement mantle since it is the most critical failure state. However, the probabilistic analysis generally requires large amount of time; thus, a response surface method proposed in this study was used to reduce the computation time for the analysis of the cemented hip implant. The results demonstrate that using an efficient probabilistic approach can significantly reduce the computation time for the failure probability of the cement from several hours to minutes. The results also show that even the deterministic failure analyses do not indicate any failure of the cement mantle with high safety factors, the probabilistic analysis predicts the failure probability of the cement mantle as 8%, which must be considered during the evaluation of the success of the cemented hip implants.

Teaching Clinical (and Nonclinical) Psychology Through Applications to the Legal System

The prediction of dangerousness and the insanity defense are two areas where psychologists provide research-based expertise to the courts. Teachers of psychology can use these topics to capture the attention of students and to show how psychological research and theory can inform and influence the legal system. Specifically, teachers can use the issue of violence risk assessment to teach basic statistical concepts, the low base rate problem, the limits of long-term behavior prediction, and the superiority of scientific approaches over intuitive approaches. Teachers can use the issue of the insanity defense to show students how clinical psychologists and the legal system differ in their conceptions of mental disorder, how attributions about intentionality drive sentencing decisions, and how modern conceptions of “free will” informed by cognitive neuroscience challenge fundamental assumptions of the criminal justice system. The topics of risk assessment and the insanity defense can stimulate student discussion by linking basic psychological concepts to an area with which students are already familiar: the legal system.

Physical model of dielectric charging in MEMS

Dielectric charging is a key failure mechanism in radio frequency (RF) microelectromechanical systems (MEMS). To date we lack suitable physical models for the prediction of long-term behavior of RF MEMS switches, susceptible to dielectric charging. In this paper, we present an original approach of studying dielectric charging including modeling of long-term behavior of RF MEMS switches based only on physical dielectric properties that are experimentally characterized. For the first time, we introduce explicitly the trapping kinetics in the model of charging in RF MEMS. In this study, the conduction mechanism and trapping properties of the plasma enhanced chemical vapor deposition (PECVD) SiNx and SiO2 dielectric layers used for the fabrication of RF MEMS switches are characterized. The conduction is determined from I–V sweeps in metal–insulator–metal (MIM) capacitors, whereas the trapping properties are determined from constant current injections in MIM capacitors. The SiNx material shows Poole–Frenkel conduction while Schottky conduction is found to be the best fitting model for the SiO2 dielectric material. The trapping properties of the SiNx layer is best fitted with a logarithmic model of repulsive trapping, while SiO2 fits better with an exponential model of first-order trapping. These extracted physical properties serve as input parameters to our model of pull-in voltage drift in RF MEMS switches. The results of modeling are verified against the pull-in voltage drifts measured on real fabricated capacitive-type RF MEMS switches. It is concluded that the simulated switch lifetime results are very consistent with experimental data obtained for electrostatic MEMS switches either made with PECVD SiNx or SiO2 dielectric materials.

Experimental study of creep-damage coupling in concrete by acoustic emission technique

In order to design reliable concrete structures, prediction of long term behaviour of concrete is important by considering a coupling between creep and damage. An experimental investigation on the fracture properties of concrete beams submitted to creep bending tests with high levels of sustained load is reported. The influence of creep on the residual capacity and the fracture energy of concrete is studied. The progression of fracture is followed by the measurement of the crack mouth opening displacement during a three-point bending test. The sustained loading seems to increase the flexural strength of concrete, probably because of the consolidation of the hardened cement paste. The acoustic emission (AE) technique is used to perform the characterization of the influence of creep on the crack development. Results give wealth information on the fracture process zone (FPZ) and the propagation of the crack. A decrease in the amplitude distribution of AE hits is observed in the post-peak region for creep specimens. The width of the FPZ also decreases in this later indicating that the material has a more brittle behaviour which may be due to the development of microcracking under creep and the prestressing of the upper zone of the beam.