ЦИФРОВАЯ ПЛАТФОРМА КАК ТЕХНИКО-ТЕХНОЛОГИЧЕСКИЙ ФЕНОМЕН И ЕГО ПРАВОВОЕ ЗНАЧЕНИЕ

Experimental, theoretical and numerical modelling of the deterioration and failure process of sandstones subject to freeze–thaw cycles

The design of noise-free, low-pollutant combustion devices requires the understanding and the prediction of the combustion noise. The noise originates from the coupling between perturbations in the heat release rate with the oscillating gas (acoustic velocity). Prediction of combustion noise requires the transfer function (TF) that correlates the variation in the heat release rate of the ame with the perturbation (acoustic velocity). Computational costs prohibit an e??cient calculation of the TF by simulating all combustion phenomena associated with the ame dynamics. Simpli??ed theoretical models, such as the hydrodynamic models, allow a signi??cant reduction of the computation time and capture the main features of the ame front dynamics. The fundamental assumption of the hydrodynamic models is that the Bunsen ame, which is described as a thin layer ( ame front) separating the burnt from the unburnt gas, is attached at the burner rim. Within the thin layer approximation, the computation of the TF requires the ame area and, consequenctly, the time-dependent ame front position. By de??ning the ame front as the zero-level set of a distance function, the evolution of the ame front is described by a level set equation. The existent experiments and theoretic kinematic models based on the thin layer approximation (e.g., the G-equation model) provide contradictory information on the phase of the TF. Experiments suggest a low-pass ??lter behaviour of the gain of the TF and an increase of the TF's phase up to several ?? as the frequency increases. In contrast, most of the theoretical models indicate a saturation of the phase of the TF at the level of ??/2. Although the use of a convective wave model for the ow [80] leads to a better agreement between theory and experiments, the origin of the convective wave remains little understood. The discrepancies between theory and experiments most likely reside in the simpli??cations employed in the theoretical models. To understand the behaviour of the experimental TF, here we extend the theoretical models based on the G-equation approach. In the ??rst step, we extend the models by addressing ames that have an arbitrary cone angle and a burning velocity with variable direction. To carry out this ??rst extension we analyse the evolution of a Bunsen ame in a Poiseuille ow from an initially at pro??le to a stationary conical shape. The analysis leads to the correct derivation of the boundary conditions in the extended model employed for the ame evolution in a perturbed Poiseuille ow. We demonstrate that the new model proposed here improves the description of the front close to the boundary and, hence, the behaviour of the ame response to velocity perturbations. Because recent measurements [52] suggest that a better understanding of the TF's phase behaviour requires a hydrodynamic model that accounts for the moving edge of the ame, in the second step we extend the hydrodynamic model to account for non-attached ames. We model the ame front as an open curve by using two level set functions whose zero-level sets are locally normal at the edge point. The movement of the edge along the ame front is accounted for via a novel model for the edge speed. During computer simulations of the ame kinematics with the new extended model the local orthogonality of the level sets is preserved by employing a novel algorithm. The simulations demonstrate that our extended model qualitatively accounts for the ame stabilisation, the ame front and edge kinematics, and the stand-o?? distance of the ame above the burner rim.

In the present paper, the heat transfer process of the braking resistor is analyzed. The corresponding theoretic model is proposed and solved numerically. The standard laminar model and constant heat flux method are employed to compute the heat transfer in the parallel channels between the braking resistor strips. The numerical computations for different conditions are performed. The corresponding heat transfer relationships among the convective heat transfer coefficient, thermal boundary layer thickness, cooling air outlet temperature and braking resistor surface temperature are studied according to the computed results. Finally, the theoretical heat transfer model of flow in the braking resistor case is used to investigate the variety of the resistor temperature of the practical braking resistor applied in some type hybrid electric armored vehicle. The vehicle operating test result shows that the uncertainty of the theoretic calculation model is within 15%, which can fulfill the engineering design requirement.

Antibodies against 2,4,5-trichlorophenol have been prepared after theoretical and molecular modeling chemical studies of three potential immunizing haptens with the aim to find out the one mimicking best the target analyte. Competitive direct and indirect ELISAs have been developed after screening a battery of haptenized enzyme tracers and coating antigens, respectively. The relation between the degree of heterology of the competitor and the resulting immunoassay detectability has been investigated according to the electronic similarities of the competitor haptens with the target analyte taking in consideration their pK(a) values. These studies have been performed using theoretical and molecular modeling tools to find out their electronic distribution at their minimum energetic levels. The results suggest that the competitors should have a high homology to produced assays with good detectability values. On the other hand detectability improves when lowering the hapten density of the competitors. An indirect competitive ELISA has been finally selected for further investigation. The immunoassay has an IC(50) value of 0.6 microg L(-)(1) and a limit of detection of 0.084 microg L(-)(1). The selectivity of the assay is high in relation to other chlorophenols frequently present in real samples. In contrast, the brominated analogues may also be recognized with this assay.

Due to the confinement and strong adsorption to the pore wall in meso- and nano- pores, fluid phase behavior in the confined media, such as the tight and shale reservoirs, can be significantly different from that in the bulk phase. A large amount of work has been done on the theoretical modeling of the phase behavior of hydrocarbons in the confined media. However, there are still inconsistencies in the theoretical models developed and validations of those models against experimental data are inadequate. In this study, we conducted a comprehensive review of experimental work on the phase behavior of hydrocarbons under confinement and analyzed various theoretical phase-behavior models. Emphasis was given to the modifications to the Peng-Robinson equation of state (PR EoS). Through the comparative analysis, we developed a modified alpha-function in PR EoS for accurate prediction of the saturation pressures of hydrocarbons in porous media. This modified alpha-function accounts for the pore size and was derived based on the regression results through minimizing the deviation between the experimentally measured and numerically calculated saturation pressure data. Meanwhile, the thermodynamic properties of propane were calculated in the bulk phase and in the nanopores. Finally, we validated the newly developed model using the experimental data generated within our research group. By applying the modified PR EoS, a more accurate representation of the experimentally measured saturation pressure data in confined nanopores was achieved. This newly developed model not only enhanced the accuracy of the predictions but also provided valuable insights into the confinement effects on the phase behavior of hydrocarbons in nanopores. Notably, we observed significant changes in the properties of propane within confined nanopores, including suppressed saturation pressure and fugacity, indicating a greater tendency for the gas to remain in the liquid phase. Additionally, the gas compressibility factor and enthalpy of vaporization were found to increase highlighting increased difficulty in transitioning from liquid to gas phase under confinement. To validate its applicability, the newly developed model was applied to the experimental data obtained in real rock samples. Interestingly, it was observed that the phase change in these samples predominantly occurred in the smallest pores. This finding highlights the importance of considering the pore size distribution when studying the phase behavior of hydrocarbons in a capillary medium even if the rock has high permeability. This study provided a simple and easy-to-implement modification to the PR EoS for accurate prediction of the phase behavior of petroleum fluids under confinement. The modification to PR EoS was more straightforward and simplified compared to the modifications available in the literature.

We try to understand the difficulties in using both theoretical modelling of turbulence and the theoretical essentialization of extreme climate events for the practical prediction calculations of the climate phenomena. We conceptually understand what contributes to rapid intensification of natural phenomena like heatwaves, floods, tornadoes or hurricanes. Predicting their rapid intensification is a completely different matter. This paper is devoted to the sudden and not frequent occurrence of extremely violent events that appear randomly in space and time in which turbulence is generally the main physical support. Coherence and regularities in this case are not yet clearly delineated. A close analogy between the theory of turbulence and the quantum theory of fields seems to me very attractive. On one hand we do have a rough, practical, working understanding of many turbulence phenomena but certainly far from a theory capable of describing them completely. On the other hand, there are hardwired patterns in nature (the well known tornado funnel pattern, for instance) and also systematic perturbations, induced by factors external to the local weather system. Under a critical combination of initial conditions and interactions an extreme event is triggered. Theoretical models available in physics, injected in the study of extreme climate phenomena could be of great use in resolving the immediacy to the consequences of global warming. We are compelled to adjust to wildly unpredictable circumstances and radical uncertainty. We try to achieve a better understanding of why the respective fields of climate (extreme events) models and theoretical mathematical models of turbulence physics are not sufficiently if not even essentially overlapping as they should be normally.

The Seismic Acoustics Laboratory (SAL) has as its principal research facility a physical modeling system. Experiments conducted with this system in the area of 3D seismic profiling have led to practical applications of physical modeling for both exploration and production geophysicists. The physical models, which are scanned in a large water tank, have been fabricated to represent various structural and stratigraphic traps. Across these models, the scanning source and receiver are independently controlled which allows for an infinite number of data acquisition schemes. To insure proper scaling of the model to the earth prototype, the large transducer source is focused to a point and the subsequent propagating wavelet is consistent enough to allow wavelet processing of the data. The resulting time sections from the physical models have a high enough signal-to-noise ratio to allow comparisons to both theoretical models and field seismic data. Time sections which profile in the modeling tank a simple anticline and also a more complicated faulted delta compare favorably with theoretical time sections. Using these two geological models, we describe various applications and pitfalls of modeling which will be of interest to interpreters working in problem areas. Introduction Practical applications of physical modeling have been discussed in the past by several authors. l, 2,3,4,7 This paper is a non-mathematical update and overview of how geophysicists can use physical modeling, along with theoretical modeling, as an interpretational tool. Because many seismic processing techniques are based on the scalar wave equation, it will be interesting to note the differences between theoretical and physical model data. These differences will provide us with insight as to when our processing and/or interpretation might be incorrect with reference to different geological structures and lithology. The Physical Modeling System The physical modeling system at SAL was based on the system described by Frenchl and exact details are given in SAL Annual Reports. 5,6 Working with the scale factors which are given in Figure 1, an 8x6x5 ft water tank was designed and built in 1977. The tank's large size insured that reflections from the sides, top or bottom would be outside the time window of signals reflecting from the physical model in the middle of the water tank. Resting on top of the tank are the computer-controlled positioning mounts (Figure 2), one for the source and the other for the receiver. These mounts control the xyz-coordinates of the source and receiver within a .01 tolerance (equivalent prototype 10 ft). Figure 3 is a top view of the tank with the source and receiver positioned over a geological model resting on thin wires. The models built to date have been approximately 16 in square and up to 4 in thick. Multi-layer models are fabricated by pouring RTV silicone rubber into a plaster cast and after the rubber hardens, the second layer with its different RTV properties is poured between a second plaster cast and the first RTV layer. Models with four-layers have been built in this manner.

Velocity measurements of cylindrical surface waves with a large aperture line-focus acoustic transducer

Microforming which exploits the advantages of metal-forming processes has been considered to be a very promising manufacturing technology for microparts. However, the fundamental understandings on microforming have not been well established yet since the extensive findings and know-how of conventional forming cannot be simply transferred to the microscale. This article attempts to offer an effective theoretical and experimental modelling to describe the so-called ‘size effect’ on the behaviour of metals in microforming. A theoretical model was developed based on the dislocation theory to quantify the grain size and feature size effects on the flow behaviour of polycrystalline materials. Tensile tests of copper sheets of various specimen thicknesses and grain sizes were carried out, and thus the effectiveness of the theoretical model can be confirmed by comparing the predicted flow stress, dislocation density, and Hall–Petch constant with experimental measurements. The general trend of decreasing flow stress with increasing grain size and decreasing specimen thickness was observed. The ratio of feature size to grain size was identified as an important parameter to characterize the flow stress level, grain boundary strengthening, and failure characteristics in microscale deformation processes.

The exporting of theoretical concepts and modelling methods from physics and mechanics to the world of biomolecules and cell biology is increasing at a fast pace. The role of mechanical forces and stresses in biology and genetics is just starting to be appreciated, with implications going from cell adhesion, migration, division, to DNA transcription and replication, to the mechanochemical transduction and operation of molecular motors, and more. Substantial advances in experimental techniques over the past 10 years allowed to get unprecedented insight into the elasticity and mechanical response of many different proteins, cytoskeletal filaments, nucleic acids, both in vitro and, more recently, directly inside the cell. In a parallel effort, also theoretical models and computational methods are evolving into a rather specialized toolbox. However, several key issues need to be addressed when applying to life sciences the theories and methods typically originating from the fields of condensed matter and solid mechanics. The presence of a solvent and its dielectric properties, the many subtle effects of entropy, the non-equilibrium thermodynamics conditions, the dominating role of weak forces such as Van der Waals dispersion, hydrophobic interactions, and hydrogen bonding, impose a special caution and a thorough consideration, up to possibly rethinking some basic physics concepts. Discussing and trying to elucidate at least some of the above issues is the main aim of the present, partial and non-exhaustive, contribution.KeywordsBiomoleculesMechanical propertiesConfigurational entropyMolecular dynamicsJarzynski identity

Theoretical guidance for fabricating higher flux hydrophobic/hydrophilic dual-layer membranes for direct contact membrane distillation

Theoretical Modeling and Experimental Verification of Mechanical Properties of Natural Fiber Reinforced Thermoplastics

Rigid airport pavements generally comprise 4 m to 6 m approximately square plain concrete slabs separated by joints. The joints form the interface between construction Lots, relieve shrinkage stresses that develop during curing, allow movement during thermal and moisture changes, and isolate different areas of pavement from each other and from other structures. Aside from from isolation joints, all these joints rely on load transfer, most commonly through aggregate interlock at sawn contraction joints, and via steel dowels at smooth interfaced construction joints. Importantly, the determination of the concrete slab thickness depends on the assumed load transfer between adjacent slabs, and this load transfer relies on the effectiveness of the joints. To allow future analysis of the factors affecting joint load transfer, a theoretical model was developed in the finite element software ABAQUS. The development of the theoretical model is detailed, including the rigid pavement, aircraft loading and subase support characteristics, the joint types being considered, and the characteristics of those joints being theoretically represented. The developed model was calibrated against falling weight deflectometer testing of full scale rigid airport pavements performed by the Federal Aviation Administration and the resulting model was used to perform a sensivity analysis of joint response under various loading conditions. In the future, the model will be used to determine the joint detailing factors that affect joint load transfer ability, including concrete mixture aggregate size, joint gap width, underlying concrete slab support, dowel size and spacing, and concrete mixture strength. Conclusions address issues identified for future theoretical modelling of rigid airport pavement joints.

Theoretical modeling and experimental study in femtosecond Bessel beam ablation of α-quartz

PurposeThe purpose of this paper is to discuss the construction of the theoretic model of systematic knowledge creation in the healthcare process according to professionals' collaboration using clinical‐pathways.Design/methodology/approachHealthcare is a knowledge‐intensive service conducted by professionals. A clinical‐pathway is an effective tool in the knowledge management aspect of this service. The theoretic model of the medical knowledge management which used the clinical‐pathway from case studies in two hospitals is constructed.FindingsThe theoretical model shows the interaction between explicit knowledge and tacit knowledge in the healthcare process using clinical‐pathways. This theoretical model is a knowledge creation model which creates new knowledge continuously. Therefore, the clinical‐pathways are suggested as an effective tool for knowledge management in healthcare.Practical implicationsPromotion of knowledge communication between healthcare professionals by clinical‐pathways activities is important for excellent healthcare management.Originality/valueThis paper will be valuable for sustained improvement of healthcare quality by knowledge management with clinical‐pathways. In this paper, the detailed theoretic model which explains medical knowledge management with clinical‐pathways has been constructed.