Parametric Simulation Study Research Articles

Effect of Type of Adhesive Material on the Strength of Bullet-Proof Glass: A Parametric Study

Laminated glass armors play key roles in defense and architecture due to its high aesthetics and inviolability. Armor designing is based upon Wave propagation phenomena produced during a high velocity impact. Laminated glass or bulletproof glass usually comprises of two or more glass sheets bonded by an interfacial layer of adhesives and backed with a high strength ductile polymer (polycarbonate). Typical bonding agents include either high performance adhesives or synthetic resins such as Polyurethane or Polyvinyl butyral (PVB). Recent literature review infers that the ballistic performance of armors is markedly influenced by both the type and thickness of bonding agents, which may be explained by the acoustic impedance mismatch between laminate materials. This paper documents a novel simulation parametric study, considering the material of adhesive layer and thus concluding that, type of adhesive layer plays an important role in maintaining the strength of the bullet-resistant glass. This study took into account the effect of three types of bonding agents (epoxy, polyurethane and PVB) having constant thickness of 1.50 mm, on the ballistic performance of the laminated glass, against AK-47 ammunition projectiles. Simulations were performed in Ansys Explicit Dynamics using a finite element method approach.

Modeling analysis on solar steam generator employed in multi-effect distillation (MED) system

Recently the porous bilayer wood solar collectors have drawn increasing attention because of their potential application in solar desalination. In this paper, a thermodynamic model has been developed to analyze the performance of the wood solar collector. A modeling analysis has also been conducted to assess the performance and operating conditions of the multiple effect desalination (MED) system integrated with the porous wood solar collector. Specifically, the effects of operating parameters, such as the motive steam temperature, seawater flow rate, input solar energy and number of effects on the energy consumption for each ton of distilled water produced have been investigated in the MED desalination system combined with the bilayer wood solar steam generator. It is found that, under a given operating condition, there exists an optimum steam generation temperature of around 145°C in the wood solar collector, so that the specific power consumption in the MED system reaches a minimum value of 24.88 kWh/t. The average temperature difference is significantly affected by the solar heating capacity. With the solar capacity increasing from 50 kW to 230 kW, the average temperature difference increases from 1.88°C to 6.27°C. This parametric simulation study will help the design of efficient bilayer wood solar steam generator as well as the MED desalination system.

Parametric simulation study for green roof retrofit over high performance solar house prototype “EFdeN Signature”

The advantages of green roofs are well documented, ranging from heat island reduction, thermal comfort, air quality, stormwater management and energy savings for buildings. However, it has been shown that green roof retrofits are more effective in old, low efficiency buildings. This paper studies the possibility of retrofitting a high efficiency solar house with a green roof system being partially shaded, optimising its characteristics by means of parametric simulation. The input variables of the green roof system are: growth medium thickness, LAI (leaf area index) and height of plants. The output variables by which the different green roof systems are compared are: annual energy demand for heating and for cooling. The study concluded that the average reductions of energy consumption when retrofitting an efficient building with an extensive green roof are of 1.01% for heating and 4.61% for cooling, but optimising parameters (low LAI in winter, high LAI and height of plants in summer) can get reductions to 1.55% for cooling and 5.95% for cooling.

Predicting grain boundary structure and energy in BCC metals by integrated atomistic and phase-field modeling

We predict structure and energy of low-angle (11¯0) pure twist grain boundaries (GBs) in five BCC transition metals (β-titanium, molybdenum, niobium, tungsten, and tantalum) using a combination of atomistic and microscopic phase-field (MPF) modeling. The MPF model takes as inputs solely the generalized stacking fault energy surfaces (i.e., the γ-surface) and elastic constants obtained from the atomistic simulations. Being an energy-based method, the MPF model lifts the degeneracy of the geometric models in predicting GB structures. For example, the multiple indefinite solutions offered by the Frank-Bilby equation are shown to converge to exactly the same equilibrium structure. It predicts a transition of the equilibrium GB structure from a pure screw hexagonal network (Mo and W) to mixed hexagonal networks (Nb and Ta) to a rhombus network (β-Ti) of dislocations. Parametric simulation studies and detailed analyses of the underlying dislocation reactions that are responsible for the formation of the rhombus and hexagonal structures reveal a close correlation between material properties (including the elastic anisotropic ratio and the local curvature on the γ-surface) and the GB structure and energy in BCC metals. This integrated approach allows one to explore, through high throughput calculations, the potential to tailor the structure and energy of special GBs in BCC metals by alloying.

Modeling Pulmonary Gas Exchange and Single-Exhalation Profiles of Carbon Monoxide.

Exhaled breath carbon monoxide (eCO) is a candidate biomarker for non-invasive assessment of oxidative stress and respiratory diseases. Standard end-tidal CO analysis, however, cannot distinguish, whether eCO reflects endogenous CO production, lung diffusion properties or exogenous sources, and is unable to resolve a potential airway contribution. Coupling real-time breath gas analysis to pulmonary gas exchange modeling holds promise to improve the diagnostic value of eCO. A trumpet model with axial diffusion (TMAD) is used to simulate the dynamics of CO gas exchange in the respiratory system and corresponding eCO concentrations for the first time. The mass balance equation is numerically solved employing a computationally inexpensive routine implementing the method of lines, which provides the distribution of CO in the respiratory tract during inhalation, breath-holding, and exhalation with 1 mm spatial and 0.01 s temporal resolution. Initial estimates of the main TMAD parameters, the maximum CO fluxes and diffusing capacities in alveoli and airways, are obtained using healthy population tissue, blood and anatomical data. To verify the model, mouth-exhaled expirograms from two healthy subjects, measured with a novel, home-built laser-based CO sensor, are compared to single-exhalation profiles simulated using actual breath sampling data, such as exhalation flow rate (EFR) and volume. A very good agreement is obtained in exhalation phases I and III for EFRs between 55 and 220 ml/s and after 10 and 20 s of breath-holding, yielding a unique set of TMAD parameters. The results confirm the recently observed EFR dependence of CO expirograms and suggest that measured end-tidal eCO is always lower than alveolar and capillary CO. Breath-holding allows the observation of close-to-alveolar CO concentrations and increases the sensitivity to the airway TMAD parameters in exhalation phase I. A parametric simulation study shows that a small increase in airway flux can be distinguished from an increase in alveolar flux, and that slight changes in alveolar flux and diffusing capacity have a significantly different effect on phase III of the eCO profiles.

The impact of facade materials on the thermal comfort and energy efficiency of offices buildings

In order to improve thermal comfort conditions of tertiary buildings through the facades of buildings, a research has been undertaken with the intention of developing a contextually appropriate and energetically efficient facade under the conditions of a hot and arid climate. The study has taken as its starting point the analysis of comfort conditions of a set of office buildings located in Biskra. These buildings were distinguished from standpoints of the treatment of their facades and the materials used. The study proposes to evaluate the thermal functioning of the different materials of the facade, then to optimize their behavior by acting on their material characteristics and the walls composition. The facade, indeed, represents a place of interaction and exchange between the inside and the outside, the performance of which is due to factors that are formal, material and technical. This article presents the main results of the analytical work. The investigation is based on an empirical approach (measurements in situ on real cases) as well as on a parametric simulation study. The results show that the facade represents with excellence the place of interaction and exchange between the interior and the exterior, the performance of which is due to factors that are both material and conceptual. Through a set of recommendations, this study tries to develop a material composition of high-performing facade that can respond optimally to the requirements of a tertiary building in a desert climate, while ensuring a pleasant thermal ambience and low consumption energy.

The impact of facade materials on the thermal comfort and energy efficiency of offices buildings

In order to improve thermal comfort conditions of tertiary buildings through the facades of buildings, a research has been undertaken with the intention of developing a contextually appropriate and energetically efficient facade under the conditions of a hot and arid climate. The study has taken as its starting point the analysis of comfort conditions of a set of office buildings located in Biskra. These buildings were distinguished from standpoints of the treatment of their facades and the materials used. The study proposes to evaluate the thermal functioning of the different materials of the facade, then to optimize their behavior by acting on their material characteristics and the walls composition. The facade, indeed, represents a place of interaction and exchange between the inside and the outside, the performance of which is due to factors that are formal, material and technical. This article presents the main results of the analytical work. The investigation is based on an empirical approach (measurements in situ on real cases) as well as on a parametric simulation study. The results show that the facade represents with excellence the place of interaction and exchange between the interior and the exterior, the performance of which is due to factors that are both material and conceptual. Through a set of recommendations, this study tries to develop a material composition of high-performing facade that can respond optimally to the requirements of a tertiary building in a desert climate, while ensuring a pleasant thermal ambience and low consumption energy.

Precast self-compacting concrete (PSCC) panel with added coir fiber: An overview

Self-compacting concrete (SCC) is the alternative way to reduce construction time and improve the quality and strength of concrete. The panel system fabricated from SCC contribute to the IBS system that is sustainable and environmental friendly. The precast self-compacting concrete (PSCC) panel with added coir fiber will be overview in this paper. The properties of SCC and coir fiber are studied and reviewed from the previous researches. Finite element analysis is used to support the experimental results by conduction parametric simulation study on PSCC under flexure load. In general, it was found that coir fiber has a significant influence on the flexural load and crack propagation. Higher fiber incorporated in SCC resulted with higher ultimate load of PSCC.

Numerical and Experimental Analysis of Spinning Process for Gas Spring Tube

In this study a methodology was developed for performing 3D finite element (FE) simulation of metal tube spinning process for automotive application. Modelling of the process was related to the experimental setup. The latter provides input parameter as well as geometrical data of the specimen used for a validation of the simulation results. Solid works was used for modelling the spinning setup, hyper mesh was used for creating finite element modelling. Explicit FE model was used for spinning simulation using LS-DYNA. Numerical results were compared with experimentally obtained tube dimensions to validate the spinning simulation Parametric study was done to improve the spinning process without any failure.

Quadrupolar asymmetry in shifted-stem vane-shaped-rod radio frequency quadrupole accelerator

Quadrupolar Asymmetry (QA), which has been a rampant problem for rod-type Radio Frequency Quadrupole (RFQ) Linacs, arises due to the geometry of resonant structure. A systematic parametric simulation study has been performed to unravel their effect on Figure of Merit (FoM) quantities namely Quality Factor (Q), Shunt Impedance (Rsh) and Quadrupolar Asymmetry (QA). A novel stem and cavity shape is proposed, which caters to the profile of electromagnetic fields of the resonant structure. A design methodology is formulated, which demonstrates that Quadrupolar Asymmetry can be annihilated, and a symmetric electric field can be produced in all four quadrants of rod-type RFQ accelerator.

Evaluating the effects of CO2 capture benchmarks on efficiency and costs of membrane systems for post-combustion capture: A parametric simulation study

Membrane separation is considered to be the most promising alternative to chemical absorption for decarbonizing fossil fuel power generating systems. However, the implementation of a membrane system has several implications for the energy and economic performances of power plants. Indeed, membrane systems allow for the non-negligible reduction of power plant capacity, which can negatively affect its efficiency. This aspect, combined with the additional capital and operating expenses, is also responsible for an increase in the electricity generation costs.Currently, the majority of studies neglected to investigate the influence of CO2 separation targets on costs, thus limiting their investigation to the case of geological storage or enhanced oil recovery (EOR) that mean CO2 purity levels after compression higher than 95%. But for certain valorization aims, like CO2 hydrogenation or solar thermochemical conversion, lower CO2 quality standards may be sufficient; to the best of our knowledge there is currently no study allowing to know the cost of CO2 capture in this unusual framework.The aim of this paper was to analyze the effects of CO2 purity targets on the energy requirement for the separation and compression operations and costs of membrane systems, considering as a study case the recovery of CO2 from flue gases of a coal-fired power plant and using a Polyactive membrane. The CO2 separation process was first investigated by exploring several membrane system concepts. Then, by focusing on dual-stage configurations, the entire carbon capture and storage (CCS) chain was analyzed. From an energy view point, the study quantified the impact of CO2 capture retrofit intervention on the power plant’s net efficiency and the extent of CO2 emissions reduction. Besides, the economic analysis allowed for an evaluation of the specific cost of the CO2 capture and the mitigation cost with or without credits for EOR. Finally, an energy and economic comparison was made with the CO2 capture based on chemical scrubbing.With a CO2 separation cost of 20÷33 $/tonne, a single stage membrane system with feed compression and permeate vacuum pumping represents the most interesting option to be used in combination with CO2 recycling technologies requiring a medium-low CO2 purity level (70÷80%). Simulation results also revealed that dual stage membrane systems envisaged are economically competitive compared to amine absorption processes in the case of geological storage, involving a cost of CO2 capture of 36÷41 $/tonne.

Influence of surface form deviations on friction in mixed lubrication

Abstract The focus of this study is on the effect of form deviations of a partial journal bearing's sliding surface on the friction force in mixed lubrication conditions. The measured friction varied considerably when the bearing was rotated in the opposite direction at the same speed and normal load. This unexpected observation motivated the presented simulation study. The overall form deviations of the surface of the test bearing were measured with white light interferometry and used as simulation input. The two-scale simulation approach considers the effect of the surface roughness on a microscopic and the global bearing geometry with the surface form deviations on a macroscopic scale. Simulation results show that the surface form deviations can have a noticeable effect on the pressure distribution of the lubricant and hence on the size of the asperity contact area which leads to the differences in friction. The influence of the lubricant viscosity, the clearance gap and the surface roughness were analysed in a parametric simulation study. Results show that the clearance and the surface roughness control the impact of the surface form deviations on the friction force. All in all, the results show the necessity to include all scales of surface form deviations in the simulation of journal bearings in a mixed lubrication regime.

On the Performance of EHL Contacts with Textured Surfaces

The effect of surface patterns created by laser on the running-in and the steady-state behavior of ST37 disk is studied both experimentally and analytically using a mixed-lubrication model. Experiments are conducted using a pin-on-disk apparatus. Circular dimples with a radius of 200 µm and depth of 30 µm are textured via a laser on the surface of the disk. The geometry of the dimples is selected based on the optimum size of dimples reported in the literature. The head of the pin is shaped such that the pin and the disk form a line contact configuration. Each experiment was performed using a new contact pair to investigate the running-in as well as the steady-state behavior of textured disks. The results indicate that by means of surface texturing the friction coefficient and wear rate can be reduced by 12–23 and 50%, respectively. The usefulness of the dimples highly depends on the speed, which has a tremendous effect on the film thickness. Increasing the velocity and decreasing the applied load result in a reduction in the wear rate. A parametric simulation study was also performed to gain insight into the relationship between the input parameters such as speed, applied load, and the size of dimples on the film thickness, pressure distribution, and the load-carrying capacity. The model is also able to predict the friction coefficient in the mixed-lubrication regime. Comparison of the friction coefficient values obtained experimentally is found to be in good agreement with the results predicted by the computational model.

Simulation Optimization and Parametric Study of a Grid Connected Solar Power Plant for Commercial Rooftop as well as on Utility Scale

Simulation Optimization and Parametric Study of a Grid Connected Solar Power Plant for Commercial Rooftop as well as on Utility Scale

HELICAL KINK INSTABILITY IN A CONFINED SOLAR ERUPTION

ABSTRACT A model for strongly writhing confined solar eruptions suggests an origin in the helical kink instability of a coronal flux rope that remains stable against the torus instability. This model is tested against the well observed filament eruption on 2002 May 27 in a parametric MHD simulation study that comprises all phases of the event. Good agreement with the essential observed properties is obtained. These include the confinement, terminal height, writhing, distortion, and dissolution of the filament, and the flare loops. The agreement is robust against variations in a representative range of parameter space. Careful comparisons with the observation data constrain the ratio of the external toroidal and poloidal field components to and the initial flux rope twist to . Different from ejective eruptions, two distinct phases of strong magnetic reconnection can occur. First, the erupting flux is cut by reconnection with overlying flux in the helical current sheet formed by the instability. If the resulting flux bundles are linked as a consequence of the erupting rope’s strong writhing, they subsequently reconnect in the vertical current sheet between them. This reforms the overlying flux and a far less twisted flux rope, offering a pathway to homologous eruptions.

3-D Vector Flow Estimation With Row-Column-Addressed Arrays.

Simulation and experimental results from 3-D vector flow estimations for a 62 + 62 2-D row-column (RC) array with integrated apodization are presented. A method for implementing a 3-D transverse oscillation (TO) velocity estimator on a 3-MHz RC array is developed and validated. First, a parametric simulation study is conducted, where flow direction, ensemble length, number of pulse cycles, steering angles, transmit/receive apodization, and TO apodization profiles and spacing are varied, to find the optimal parameter configuration. The performance of the estimator is evaluated with respect to relative mean bias ~B and mean standard deviation ~σ . Second, the optimal parameter configuration is implemented on the prototype RC probe connected to the experimental ultrasound scanner SARUS. Results from measurements conducted in a flow-rig system containing a constant laminar flow and a straight-vessel phantom with a pulsating flow are presented. Both an M-mode and a steered transmit sequence are applied. The 3-D vector flow is estimated in the flow rig for four representative flow directions. In the setup with 90° beam-to-flow angle, the relative mean bias across the entire velocity profile is (-4.7, -0.9, 0.4)% with a relative standard deviation of (8.7, 5.1, 0.8)% for ( vx, vy, vz ). The estimated peak velocity is 48.5 ± 3 cm/s giving a -3% bias. The out-of-plane velocity component perpendicular to the cross section is used to estimate volumetric flow rates in the flow rig at a 90° beam-to-flow angle. The estimated mean flow rate in this setup is 91.2 ± 3.1 L/h corresponding to a bias of -11.1%. In a pulsating flow setup, flow rate measured during five cycles is 2.3 ± 0.1 mL/stroke giving a negative 9.7% bias. It is concluded that accurate 3-D vector flow estimation can be obtained using a 2-D RC-addressed array.

On some statistical models with a random number of observations

We extend some classical statistical inference to the case of a random number of observations with a stabilized distribution: namely, in the normal model, inference for the mean with known and unknown variance and inference for the variance. We describe some useful models for the number of observations obtained by truncation or translation of usual models given by integer-valued random variables: Poisson, binomial, geometric, and negative binomial. We present an efficient random search algorithm for the computation of the quantiles of the relevant statistics, we describe an interval estimation procedure for the extended model, and we propose a parametric bootstrap simulation study to validate the proposed procedure.

A Parametric Study of Reservoir Cooling for Enhanced Recovery by Carbon Dioxide Flooding

SummarySlimtube experiments and analytical calculations show that minimum miscibility pressure (MMP) can significantly decrease with a relatively modest reduction in temperature. Compositional simulation, however, is often made under isothermal conditions even though a prior waterflood may have reduced reservoir temperature in the swept zones of the reservoir. This study uses computer simulation to examine how cooling by a prior waterflood can affect recovery during a carbon dioxide (CO2) flood by lowering the MMP in the swept zones.The results show that for the cases considered, injection of cooler water can increase incremental oil recovery (IOR) significantly because of MMP reduction in the zones swept by the solvent. A parametric simulation study demonstrates how injection temperature, initial reservoir pressure, formation heterogeneity, formation thickness, heat transfer with the overburden/underburden formations, and water-alternating-gas (WAG) ratio may affect the IOR. The simulations are conducted by a long waterflood of up to 2.0 pore volumes injected before CO2 injection. The water during the secondary recovery is injected at several temperatures for selected 1D, 2D, and 3D flow models. CO2 solvent is then injected continuously, or in WAG mode, at the same waterflood-injection temperature. The increase in IORs (greater than what would have been obtained by a standard CO2 flood at original reservoir temperature) varied greatly depending on the flow dimension, initial reservoir pressure, level of heterogeneity, formation thickness, degree of energy gain from the surroundings, and injection temperature. Increases in recovery by CO2 flooding varied from a few percent to nearly 30% of original oil in place, with the highest recoveries occurring in 1D flow. For the same flow dimension, the largest increase in recoveries is achieved when the MMP is sufficiently reduced by temperature so that an otherwise immiscible or near-miscible flood becomes a multicontact miscible flood. The results demonstrate that including temperature variations in the simulations is important for floods that are nearly miscible because recoveries are most affected in that region. Further, including temperature variations could be very important to improve the quality of history matches used to understand the reservoir.

A simulation study of parameters for the censored shifted Gompertz mixture distribution: A Bayesian approach

The Bayesian estimation of unknown parameters of shifted Gompertz mixture model under type-I censorship, assuming both the informative and noninformative priors is investigated using different loss functions to obtain the Bayes estimates. It is seen that the closed-form expressions for the Bayes estimators cannot be obtained under shape and scale parameters. Some properties of the model with some graphs of the mixture density are discussed. These properties include Bayes estimators, posterior risks and reliability function under simulation scheme. The prior belief of the mixture model is represented by the uniform, and gamma prior. Bayes estimates are obtained considering two cases: (a) when the shape parameter is known and (b) when all parameters are unknown. A detailed simulation study is carried out to investigate the performance of the proposed set of estimators of the mixture model parameters. Posterior risks of the Bayes estimators are evaluated and compared to explore the effect of prior belief and loss functions.

THE LAUNCHING OF COLD CLOUDS BY GALAXY OUTFLOWS. II. THE ROLE OF THERMAL CONDUCTION

ABSTRACT We explore the impact of electron thermal conduction on the evolution of radiatively cooled cold clouds embedded in flows of hot and fast material as it occurs in outflowing galaxies. Performing a parameter study of three-dimensional adaptive mesh refinement hydrodynamical simulations, we show that electron thermal conduction causes cold clouds to evaporate, but it can also extend their lifetimes by compressing them into dense filaments. We distinguish between low column-density clouds, which are disrupted on very short times, and high-column density clouds with much longer disruption times that are set by a balance between impinging thermal energy and evaporation. We provide fits to the cloud lifetimes and velocities that can be used in galaxy-scale simulations of outflows in which the evolution of individual clouds cannot be modeled with the required resolution. Moreover, we show that the clouds are only accelerated to a small fraction of the ambient velocity because compression by evaporation causes the clouds to present a small cross-section to the ambient flow. This means that either magnetic fields must suppress thermal conduction, or that the cold clouds observed in galaxy outflows are not formed of cold material carried out from the galaxy.