Experimental Modeling Techniques Research Articles

Modeling and experimental approaches for elucidating multi-scale uterine smooth muscle electro- and mechano-physiology: A review.

The uterus provides protection and nourishment (via its blood supply) to a developing fetus, and contracts to deliver the baby at an appropriate time, thereby having a critical contribution to the life of every human. However, despite this vital role, it is an under-investigated organ, and gaps remain in our understanding of how contractions are initiated or coordinated. The uterus is a smooth muscle organ that undergoes variations in its contractile function in response to hormonal fluctuations, the extreme instance of this being during pregnancy and labor. Researchers typically use various approaches to studying this organ, such as experiments on uterine muscle cells, tissue samples, or the intact organ, or the employment of mathematical models to simulate the electrical, mechanical and ionic activity. The complexity exhibited in the coordinated contractions of the uterus remains a challenge to understand, requiring coordinated solutions from different research fields. This review investigates differences in the underlying physiology between human and common animal models utilized in experiments, and the experimental interventions and computational models used to assess uterine function. We look to a future of hybrid experimental interventions and modeling techniques that could be employed to improve the understanding of the mechanisms enabling the healthy function of the uterus.

Analysis of Seepage Through The Dam Considering Various Soil Characteristics Using an Experimental and The Finite Element Modeling Technique

In this study, the rate of seepage flow through the dam was investigated using both experimental and numerical modeling techniques. Two different types of soil samples were collected at a depth of 1m from the Auchi site in Edo State, Nigeria. The soil samples were subjected to preliminary tests such as the sieve analysis, the limit state (liquid limit, plastic limit and plasticity index), and the specific gravity test. Notable differences in the Geotechnical properties of two samples of soils were observed. The sieve analysis indicated that the particles passing through a 200-sieve number of size 0.075mm were 14.32% and 13.48% respectively. The liquid limit of sample 1 and sample 2 was determined to be 35% and 30%, the plastic limit 20.5% and 24.3%, the plasticity index 14.5% and 5.7% and the specific gravity of the two samples 2.63 and 2.65 respectively. Shear test was conducted to obtain the bearing capacity of soil using Terzaghi principle thereafter, the finite element analysis was used by applying SEEP/W of the Geo Studio program to determine the rate of flow of seepage through the dam. The result of the analysis showed that earthen dam without considering the core gave 12% difference in the seepage through the earthen material, the core of hydraulic conductivity 10 times less than that of the homogenous material gave 19.06% percentage difference seepage rate of flow with consideration of core with k 10 times less than homogenous material and the core of hydraulic conductivity 100 times less results gave 17.86% percentage difference for core of k 100 times less than homogenous material. Recommendations were made based on these results to reduce the rate of flow of seepage through the dam.

Deformation Mechanics of Fuel Cell Gas Diffusion Layer: Cyclic Response and Constitutive Model

The deformation mechanics of a typical gas diffusion layer using experimental and advanced modelling technique is reported. The experimental cyclic response is observed similar to pseudo-elastic materials with highly nonlinear loading/unloading. The cyclic compressive mechanical response of gas diffusion layer (GDL) is modelled to be the outcome of cumulative changes in deformation kinematics of matrix and fiber fractions. The individual mechanisms necessitating the energy dissipation, residual strain, and stress softening during cyclic mechanical response are related to nonlinear hyperelastic matrix with the damage function and inelastic activation function at the interface of constituents. The model predicts highly nonlinear elastic loading, residual strain, hysteresis, and damage quotient associated with stress softening as a function of several cycles. The significant takeaway from this study is in terms of quantifying strength, inelastic nature of individual constituents. The proposed model is simulated for low-level altering stresses of up to twenty cycles. The results show the build-up of residual strains and hysteresis as a function of fuel cell clamping pressure.

Modelling of Hydroabrasive Erosion in Pelton Turbine Injector

Sand particle-led erosion in the turbine parts of hydropower projects (excluding storage type projects) based on Himalaya-originated Rivers is one of the key operational challenges for concerned hydropower stations. Researchers have made multiple attempts to understand the nature of erosion and its combating technique by using numerical and experimental modelling techniques. This study relates to numerical and experimental modelling of sand particle-led erosion in the injector of the most preferred high head turbine, i.e., the Pelton turbine, followed by a comparative analysis of both techniques. This article attempts to compare erosion qualitatively and quantitatively, thus adding to the current state of the art of turbine erosion modelling. The results direct that the erosion-prone area is the needle seat in the nozzle and the region between the needle tip and nozzle exit in the needle, similar to findings reported by authors performing field setting research. The innovative aspect of the study is that by mapping the shape of the initial and eroded needle, mass lost in the erosion-prone area (as indicated by numerical erosion modelling) is calculated and compared against numerical modelling results. With the Oka erosion model employed for numerical modelling, the error in computation is about 31%. The nature of erosion in a partially open injector reveals that erosion in the needle increases with the nozzle’s partial opening. Nozzle erosion spreads away from the needle seat to the whole nozzle body. As commonly understood, the erosion of turbine parts gives rise to mechanical vibrations (especially in rotating parts) and energy loss. Numerical modelling results of injector erosion’s effect on jet energy are also presented. With uniformly spread erosion of 0.5 mm in both the needle and nozzle, loss in jet energy is 5.63%.

Comparative Study of Experimental and Modeling of Fly Ash-Based Concrete.

The application of supplementary cementitious materials (SCMs) in concrete has been reported as the sustainable approach toward the appropriate development. This research aims to compare the result of compressive strength (C-S) obtained from the experimental method and results estimated by employing the various modeling techniques for the fly-ash-based concrete. Although this study covers two aspects, an experimental approach and modeling techniques for predictions, the emphasis of this research is on the application of modeling methods. The physical and chemical properties of the cement and fly ash, water absorption and specific gravity of the aggregate used, surface area of the cement, and gradation of the aggregate were analyzed in the laboratory. The four predictive machine learning (PML) algorithms, such as decision tree (DT), multi-linear perceptron (MLP), random forest (RF), and bagging regressor (BR), were investigated to anticipate the C-S of concrete. Results reveal that the RF model was observed more exact in investigating the C-S of concrete containing fly ash (FA), as opposed to other employed PML techniques. The high R2 value (0.96) for the RF model indicates the high precision level for forecasting the required output as compared to DT, MLP, and BR model R2 results equal 0.88, 0.90, and 0.93, respectively. The statistical results and cross-validation (C-V) method also confirm the high predictive accuracy of the RF model. The highest contribution level of the cement towards the prediction was also reported in the sensitivity analysis and showed a 31.24% contribution. These PML methods can be effectively employed to anticipate the mechanical properties of concretes.

Data-driven prediction of in situ CO2 foam strength for enhanced oil recovery and carbon sequestration.

Carbon dioxide foam injection is a promising enhanced oil recovery (EOR) method, being at the same time an efficient carbon storage technology. The strength of CO2 foam under reservoir conditions plays a crucial role in predicting the EOR and sequestration performance, yet, controlling the strength of the foam is challenging due to the complex physics of foams and their sensitivity to operational conditions and reservoir parameters. Data-driven approaches for complex fluids such as foams can be an alternative method to the time-consuming experimental and conventional modeling techniques, which often fail to accurately describe the effect of all important related parameters. In this study, machine learning (ML) models were constructed to predict the oil-free CO2 foam apparent viscosity in the bulk phase and sandstone formations. Based on previous experimental data on various operational and reservoir conditions, predictive models were developed by employing six ML algorithms. Among the applied algorithms, neural network algorithms provided the most precise predictions for bulk and porous media. The established models were then used to compute the critical foam quality under different conditions and determine the maximum apparent foam viscosity, effectively controlling CO2 mobility to co-optimize EOR and CO2 sequestration.

Multistep Experimental Calibration of Mechanical Parameters for Modelling Multilayer Antishatter Safety Films in Structural Glass Protection

Glass material is largely used in buildings and facilities due to various motivations. Besides, glass still represents a vulnerable component for building occupants. Careful attention is required especially for glass elements that may be subjected to extreme design loads, such as impact, vibrations, etc. Among various approaches and techniques to prevent danger for people in case of glass breakage, multilayer antishatter safety films (ASFs) are commercially available for the retrofit of existing monolithic glass members. In the present research study, a multistep experimental program is presented to obtain the characterization of key input mechanical parameters that are required for the numerical analysis of glass elements protected by ASFs. Relevant characteristics are derived for the definition of an equivalent material and monolithic tape able to reproduce the ASF experimental outcomes. On the side of experiments, artificially aged specimens (healing process) are investigated. A major advantage is taken from small-scale peel and tensile tests on ASF samples, as well as Operational Modal Analysis (OMA) techniques for nondestructive vibration measurements on preliminary fractured specimens of ASF-bonded glass elements. Efficient Finite Element (FE) numerical models calibrated with the support of experimental data and Cohesive Zone Modelling (CZM) techniques are presented for discussion of comparative results, giving evidence of rather good estimates and possible extension of the multistep experimental procedure.

Framework for Predicting Failure in Polymeric Unidirectional Composites through Combined Experimental and Computational Mesoscale Modeling Techniques

As composites continue to be increasingly used, finite element material models that homogenize the composite response become the only logical choice as not only modeling the entire composite microstructure is computationally expensive but obtaining the entire suite of experimental data to characterize deformation and failure may not be possible. The focus of this paper is the development of a modeling framework where plasticity, damage, and failure-related experimental data are obtained for each composite constituent. Mesoscale finite elements models consisting of multiple repeating unit cells are then generated and used to represent a typical carbon fiber/epoxy resin unidirectional composite to generate the complete principal direction stress-strain curves. These models are subjected to various uniaxial states of stress and compared with experimental data. They demonstrate a reasonable match and provide the basic framework to completely define the composite homogenized material model that can be used as a vehicle for failure predictions.

Hydration of ferrite-rich Portland cement: Evaluation of Fe-hydrates and Fe uptake in calcium-silicate-hydrates

The hydration process in ferrite-rich cement (FC) and its pore structure have been investigated by experimental and thermodynamic modelling techniques. X-ray diffraction (XRD)/Rietveld analysis, thermogravimetry (TG), and mercury intrusion porosimetry (MIP) were performed to study the hydration process, pore volume-pore size distributions, and Fe uptake in calcium-silicate-hydrate (C-S-H). Similar phases were found in both FC and ordinary Portland cement (OPC). The hydration degree of FC was higher at the early stage compared with that of OPC; however, the hydration of OPC exceeded that of FC after 14 days because the high amount of C2S in OPC promoted the late hydration. The XRD-TG results revealed relatively similar Fe uptake by C-S-H in both FC and OPC. The thermodynamic model confirmed the formation of a high amount of Fe phases in FC. Moreover, the model predictions agreed well with the experimental results, demonstrating the accuracy of the proposed model for FC.

2D X-ray diffraction and molecular modelling of the crystalline structure of polyesters under uniaxial stress

Studying the crystalline structure of uniaxially and biaxially drawn polyesters is of great importance due to their wide range of applications. In this study, we shed some light on the behaviour of PET and PEN under uniaxial stress using experimental and molecular modelling techniques. Comparing experiment with modelling provides insights into polymer crystallisation with extended chains. Experimental x-ray diffraction patterns are reproduced by means of models of chains sliding along the c-axis leading to some loss of three-dimensional order, i.e. moving away from the condition of perfect register of the fully extended chains in triclinic crystals of both PET and PEN. This will help us understand the mechanism of polymer crystallisation under uniaxial stress and the appearance of mesophases in some cases as discussed herein.

Finite Element Modelling of a Parabolic Trough Collector for Concentrated Solar Power

Nowadays the design of large-scale structures can be effectively improved by the adoption of numerical models. Even if experimental tests still play a fundamental role, a methodological approach that combines experimental testing and modelling technique can significantly improve the understanding of the matter. This, in fact, would result in a more reliable optimization process, drastically reducing efforts and uncertainties towards the implementation of the final product. The present work deals with the development of a finite element model for the analysis of a full-scale prototype of an innovative parabolic trough collector. The collector is analysed under several load conditions in order to evaluate its structural behaviour. Each load configuration is also numerically reproduced. Moreover, it is demonstrated that the model is capable of reproducing both the global (stiffness) and local (strain state) behaviour of the structure. Specifically, the comparison between experimental data and numerical results show a good agreement for the global parameter torsional stiffness. Local strain values are also well reproduced in high-stressed zone. Thus, the model can be used as a reliable “virtual tool” for designers to evaluate the suitability of layout modifications, thereby replacing and reducing the amount of commonly needed experimental tests and, consequently, reducing time and costs. Finally, an example of the potentiality of the finite element model adopted for a computer-aided engineering approach is shown to determine the most promising solution for increasing the torsional stiffness of the trough, while simultaneously limiting the required experimental tests.

Testing of Explosion-Proof Coatings in Cylindrical and Conical Shock Tubes

In experiments using cylindrical and conical shock tubes, the parameters of the shock-wave load transmitted to the rigid wall through the layers of a nonwoven covering made of aramid fibers are determined. The effect of amplifying the amplitude of the pressure wave depending on the layer’s thickness is demonstrated. The developed experimental modeling technique and the results obtained show that a conical shock tube is an effective tool for studying the interaction of spherical shock waves (SWs) with layers of explosion-proof coatings.

A Lumped Parameter Model of a Fibre-Reinforced Composite Plate with Temperature Dependence Based on Thermal Vibration Measurements

Background: Experimental modelling techniques are still rare for composite structures under complex thermal environments. Objective: In this paper, by taking a fibre-reinforced composite plate (FRCP) as an example, a lumped parameter model of the FRCP with temperature dependence is developed from an experimental perspective. Methods: Initially, a series of thermal vibration measurements are performed under different temperatures to characterize the temperature-dependent vibration behaviours of the FRCP, in which the natural frequencies and modal damping ratios are identified via the variational mode decomposition method. Then, according to the degree of freedom division criterion of the half-wave number, a mass-spring-damper lumped parameter model of this type of composite plate considering additional thermal stiffness is established. Finally, a novel method of determining the lumped stiffness and damping parameters in this model is proposed based on the above experimental data. Results: The developed model is verified by comparing the theoretical natural frequencies, modal shapes and resonant responses with the test results at 40, 120, 220 and 300 °C, for which the calculation errors are within an acceptable range. Conclusions: It has been found that the accuracy of this lumped parameter model can be further improved by applying a larger number of modes to inversely calculate the lumped stiffness and damping parameters. Meanwhile, the efficiency can also be increased by adopting an appropriate step size in the iterative calculation of the additional thermal stiffness.

Mechanical performance and crashworthiness of plates and extrusions subjected to cutting: An overview

Abstract Understanding the mechanical response of structures such as plates and thin-walled extrusions subjected to cutting and tearing by hardened wedges (blades) is of great interest to scientists and engineers. This complex problem arises in a plethora of disciplines, including but not limited to the broad spectrums of manufacturing, construction and engineering design. Furthermore, studying this topic is a comprehensive endeavor which incorporates advanced concepts within stress analysis and materials science. Despite these challenges, a multitude of advancements were achieved through extensive physical testing, followed by the subsequent development of theoretical explanations and modeling efforts. This paper reviews the major contributions in recent decades towards understanding cutting-induced plastic deformation through experimental, analytical and numerical modeling techniques. The plate tearing problem was historically of interest to the ocean engineering community as an approximation for ship grounding incidents. More recently, the potential for cutting to serve as a means of energy dissipation for enhanced vehicular safety was identified due to the characteristic near-constant force response. Experimental studies were conducted from quasi-static to high rate blast loading conditions (V > 100 m/s). Numerical modeling with Eulerian mechanics and meshfree element formulations were identified as the most accurate techniques, although these schemes are computationally expensive. Analytical solutions are highly sought after since they provide valuable information almost instantaneously. Early modeling efforts yielded purely empirical relationships with gradual improvement, followed by the development of fully analytical formulations which rely upon approximations of the strain fields in combination with the principle of virtual power to obtain resultant forces.

Experimental Harmonization of Shape Intuitive Interaction

Abstract With the increasing functionality and complexity of the material environment it is becoming important to universally improve the quality of its shape design for people with different knowledge. When the material environment shape does not match its value content or acquire unpredictable meaning, it creates disharmony between the function and user that requires intellectual and / or emotional effort for interaction. The intuitive design improves user’s interaction because the information is presented on the subconscious level, hence it is accepted as a natural part of our environment and demands less effort to grasp and evaluate it. In this study, the scientific context of intuition is examined to determine methods and values of shape intuitive expression modeling. The goal of the study is to assess the effectiveness of shape experimental intuitive harmonization methodology using qualitative and quantitative methods. Functional and interaction restrictions are integrated into the object’s shape by employing experimental modeling techniques. Surveys, controlled observations and MaxDiff analysis were used to monitor intuitive harmonization effects on car body split-line and box shape physical models. Experimental results show that the majority of participants consider conceptual shape models to be more intuitively attractive and informative. The study concludes that it is possible and viable to employ a proposed shape intuitive harmonization variable to achieve a universally positive effect.

Modeling and Implementation of Quadcopter Autonomous Flight Based on Alternative Methods to Determine Propeller Parameters

To properly simulate and implement a quadcopter flight control for intended load and flight conditions, the quadcopter model must have parameters on various relationships including propeller thrust-torque, thrust-PWM, and thrust--angular speed to a certain level of accuracy. Thrust-torque modeling requires an expensive reaction torque measurement sensor. In the absence of sophisticated equipment, the study comes up with alternative methods to complete the quadcopter model. The study also presents a method of modeling the rotational aerodynamic drag on the quadcopter. Although the resulting model of the reaction torque generated by the quadcopter's propellers and the model of the drag torque acting on the quadcopter body that are derived using the methods in this study may not yield the true values of these quantities, the experimental modeling techniques presented in this work ensure that the derived dynamic model for the quadcopter will nevertheless behave identically with the true model for the quadcopter. The derived dynamic model is validated by basic flight controller simulation and actual flight implementation. The model is used as basis for a quadcopter design, which eventually is used for test purposes of basic flight control. This study serves as a baseline for fail-safe control of a quadcopter experiencing an unexpected motor failure.

Uncertainty quantification of machining simulations using an in situ emulator

ABSTRACTUnderstanding the uncertainty in simulation outputs is important for careful decision-making regarding a machining process. However, Monte Carlo–based methods cannot be used for evaluating the uncertainty when the simulations are computationally expensive. An alternative approach is to build an easy-to-evaluate emulator to approximate the computer model and run the Monte Carlo simulations on the emulator. Although this approach is very promising, it becomes inefficient when the computer model is highly nonlinear and the region of interest is large. Most machining simulations are of this kind because the output is affected by several quantitative factors—such as the workpiece material properties, cutting tool parameters, and process parameters whose effects can change depending on other qualitative factors such as the type of materials, tool designs, and tool paths. Because the number of levels of the qualitative factors can range from tens to thousands, building an accurate emulator is not an easy task. This article proposes a new approach, called an in situ emulator, to overcome this problem. The idea is to build an emulator for the user-specified levels of the qualitative factors and inside the local region defined by the input uncertainty distribution of the quantitative factors. Efficient experimental design and statistical modeling techniques are used for constructing the in situ emulator. The approach is illustrated using the simulations of two solid end milling processes.

Probing the interaction of the phytochemical 6-gingerol from the spice ginger with DNA

6-Gingerol [5-hydroxy-1-(4-hydroxy-3-methoxyphenyl) decan-3-one], the bio-active ingredient of the popular Indian spice ginger (Zingiber officinale Roscoe), is well-known for its pharmacological and physiological actions. The potent antioxidant, antiemetic, antiulcer, antimicrobial, analgesic, hypoglycemic, antihypertensive, antihyperlipidemic, immunostimulant, anti-inflammatory, cardiotonic, and cancer prevention activities of 6-Gingerol has been investigated and explored. 6-Gingerol is a good candidate for the treatment of various cancers including prostrate, pancreatic, breast, skin, gastrointestinal, pulmonary, and renal cancer. In this study we report for the first time the molecular recognition of 6-Gingerol with calf thymus DNA (ctDNA) through experimental and molecular modeling techniques confirming a minor groove binding mode of 6-Gingerol with ctDNA. Fluorescence and UV–vis spectroscopic studies confirm the complex formation of 6-gingerol with ctDNA. The energetics and thermodynamics of the interaction of 6-Gingerol with ctDNA was explored by Isothermal Titration Calorimetry (ITC) and Differential Scanning Calorimetry (DSC). The ctDNA helix melting upon 6-Gingerol binding was examined by melting temperature Tm analysis. Further the electrophoretic mobility shift assay confirms a possible groove binding of 6-Gingerol with ctDNA. Molecular docking and Molecular dynamics (MD) studies provide a detailed understanding on the interaction of 6-Gingerol binding in the minor groove of DNA which supports experimental results.

Determination of Geochemical Bio-Signatures in Mars-Like Basaltic Environments.

Bio-signatures play a central role in determining whether life existed on early Mars. Using a terrestrial basalt as a compositional analog for the martian surface, we applied a combination of experimental microbiology and thermochemical modeling techniques to identify potential geochemical bio-signatures for life on early Mars. Laboratory experiments were used to determine the short-term effects of biota on the dissolution of terrestrial basalt, and the formation of secondary alteration minerals. The chemoorganoheterotrophic bacterium, Burkholderia sp. strain B_33, was grown in a minimal growth medium with and without terrestrial basalt as the sole nutrient source. No growth was detected in the absence of the basalt. In the presence of basalt, during exponential growth, the pH decreased rapidly from pH 7.0 to 3.6 and then gradually increased to a steady-state of equilibrium of between 6.8 and 7.1. Microbial growth coincided with an increase in key elements in the growth medium (Si, K, Ca, Mg, and Fe). Experimental results were compared with theoretical thermochemical modeling to predict growth of secondary alteration minerals, which can be used as bio-signatures, over a geological timescale. We thermochemically modeled the dissolution of the basalt (in the absence of biota) in very dilute brine at 25°C, 1 bar; the pH was buffered by the mineral dissolution and precipitation reactions. Preliminary results suggested that at the water to rock ratio of 1 × 107, zeolite, hematite, chlorite, kaolinite, and apatite formed abiotically. The biotic weathering processes were modeled by varying the pH conditions within the model to adjust for biologic influence. The results suggested that, for a basaltic system, the microbially-mediated dissolution of basalt would result in “simpler” secondary alteration, consisting of Fe-hydroxide and kaolinite, under conditions where the abiotic system would also form chlorite. The results from this study demonstrate that, by using laboratory-based experiments and thermochemical modeling, it is possible to identify secondary alteration minerals that could potentially be used to distinguish between abiotic and biotic weathering processes on early Mars. This work will contribute to the interpretation of data from past, present, and future life detection missions to Mars.

A Comprehensive Clinical Decision Support Application Software Tool for Dose Management Procedure in SPECT

SPECT is a nuclear medicine tomographic imaging technique which uses gamma rays to produce images from a radioactive source. The source is either administered or injected into the patient and an attached computer process the information as an image. In medical imaging procedure, patients radiation dose are manage through appropriate dose optimisation protocol by various imaging centers. The protocol is designed to establish a balance between the injected activity and the quality of images produced. The aim of the study is to determine and design a GUI of the relationship between patient’s radiation dose from the injected activities and the image quality based on the signal to noise ratio. The study procedure involved three processes, the injected activities, which is administered to patients based on age, weight and gender, the process imaging technique based on image reconstruction method and the image quality, based on signal to noise ratio. Minitab statistical application tool was used to design a comprehensive clinical support application software based on mathematical model of patient’s preclinical information and administered activity. This was done by using experimental analytical modeling technique to determine BSI, from measured body height and weight based on age and gender. The Minitab regression modeling technique was then used to model the relationship between administered activities (potential patient dose) based on age and weight and image quality based on signal to noise ratio (SNR). So that with known patient’s height and weight and the injected activity, pre-imaging input parameters are determined, enabling dose estimate parameters to be predicted before the beginning of the imaging procedure. These were done in order to predict the expected SNR that will be good enough to answer all the clinical questions from the administered activities. This enable dose optimisation protocol to be established using a comprehensive clinical decision support application software for clinical application in SPECT imaging.