Use Of Analytical Models Research Articles

Retrieval of chromophore concentration changes in a digital human head model using analytical mean partial pathlengths of photons.

Continuous-wave functional near-infrared spectroscopy has proved to be a valuable tool for assessing hemodynamic activity in the human brain in a non-invasively and inexpensive way. However, most of the current processing/analysis methods assume the head is a homogeneous medium, and hence do not appropriately correct for the signal coming from the scalp. This effect can be reduced by considering light propagation in a layered model of the human head, being the Monte Carlo (MC) simulations the gold standard to this end. However, this implies large computation times and demanding hardware capabilities. In this work, we study the feasibility of replacing the homogeneous model and the MC simulations by means of analytical multilayered models, combining in this way, the speed and simplicity of implementation of the former with the robustness and accuracy of the latter. Oxy- and deoxyhemoglobin (HbO and HbR, respectively) concentration changes were proposed in two different layers of a magnetic resonance imaging (MRI)-based meshed model of the human head, and then these changes were retrieved by means of (i)a typical homogeneous reconstruction and (ii)a theoretical layered reconstruction. Results suggest that the use of analytical models of light propagation in layered models outperforms the results obtained using traditional homogeneous reconstruction algorithms, providing much more accurate results for both, the extra- and the cerebral tissues. We also compare the analytical layered reconstruction with MC-based reconstructions, achieving similar degrees of accuracy, especially in the gray matter layer, but much faster (between 4 and 5 orders of magnitude). We have successfully developed, implemented, and validated a method for retrieving chromophore concentration changes in the human brain, combining the simplicity and speed of the traditional homogeneous reconstruction algorithms with robustness and accuracy much more similar to those provided by MC simulations.

Scanning Probe Microscopy Techniques for Studying the Cell Glycocalyx.

The glycocalyx is a brush-like layer that covers the surfaces of the membranes of most cell types. It consists of a mixture of carbohydrates, mainly glycoproteins and proteoglycans. Due to its structure and sensitivity to environmental conditions, it represents a complicated object to investigate. Here, we review studies of the glycocalyx conducted using scanning probe microscopy approaches. This includes imaging techniques as well as the measurement of nanomechanical properties. The nanomechanics of the glycocalyx is particularly important since it is widely present on the surfaces of mechanosensitive cells such as endothelial cells. An overview of problems with the interpretation of indirect data via the use of analytical models is presented. Special insight is given into changes in glycocalyx properties during pathological processes. The biological background and alternative research methods are briefly covered.

Performance‐based testing specifications for seismic isolators

AbstractThis paper presents a study that determines the conditions of testing for determining the bounding properties of seismic isolators for use in analysis and design in a test that is meant to be a replacement of tests Items 2(a) and 3 of ASCE/SEI‐7. Then separately, the study determines the conditions of testing for determining the adequacy of isolators in the maximum considered earthquake in a test is meant to be a replacement of test Item 4 of ASCE/SEI‐7. The test conditions are determined by performing analyses with models that account for the time‐variant properties of the isolators and by computing the resultant isolator displacements. In performing the work, a large number of isolation systems (total of 96 systems, single friction pendulum, triple friction pendulum and lead‐rubber), three different seismic hazards as measured by the spectral acceleration at the period of one second, and a large collection of bi‐directional ground motions with short‐ and long‐duration characteristics (71 pairs of each duration, 96 systems, three seismic hazards) were considered. Fundamental in this methodology is the use of analysis models in which the properties of the isolators (friction or characteristic strength) are dependent on the instantaneous temperature at the sliding interfaces or in the lead core.

Analytical and computer modeling of surfaces with the curvilinear projection method

The article discusses the shaping of surfaces by analytical methods and their visualization by means of computer graphics. This topic attracts the attention of architects, engineers and mechanical scientists, for whom it is important to see the surfaces in the structures of machines for various purposes and in the forms of structures, to approximate complex surfaces with simpler ones - analytical ones; choose a rational form of the shell from several options, taking into account the functional, technological and ergonomic requirements for the product. The purpose of the work is to study the methods of formation of surface shapes. The research method is the general analytical theory of applied surface shaping, which meets modern requirements for the use of computer technology. In this paper, parametric equations of the cyclic surface of Joachimsthal are obtained, the possibilities of shaping such surfaces, which are recommended for practical use, are shown. Using examples of visualization of surfaces by means of computer graphics (Maple program), the use of analytical models is shown, which makes it possible to quickly and reliably assess the constructive and aesthetic qualities of the shell in scientific research, design, and manufacture. The ways of developing an analytical apparatus are determined, which allows modeling the process of curvilinear projection and the formation of surfaces as a system of projecting rays passing through a given surface projection. The purposeful choice of the parametric form of analytical modeling of surfaces contributes to the direct use of models in automated design systems, pre-production systems and in modern computer graphics packages (Kompas 3D, Renga, Revit, Ansys, Lira Sapr, Scad, etc.).

Attenuation of Tollmien–Schlichting waves using resonating surface-embedded phononic crystals

A novel method for control of convective boundary layer instabilities using metamaterial concepts is investigated. Attenuation of Tollmien–Schlichting (TS) waves with surface-embedded one-dimensional phononic crystals (PCs) is theoretically and numerically modeled, capitalizing on the inherent frequency band stop of PCs. The PC is tuned to the targeted TS wave characteristics through the use of analytical models derived from transfer matrix and interface response theories, verified using a finite elements analysis. The interaction between TS waves and a single PC is investigated using coupled two-dimensional fluid structure interaction simulations in the frequency domain. It is shown that TS waves are either amplified or attenuated depending on whether the PC free-face surface displacement and unsteady perturbation pressure at the wall are in-phase or out-of-phase, respectively. The perturbation pressure acts solely as the driver for the mechanical oscillation of the PC. The emerging hydrodynamic coupling between TS waves and the PC is found to be governed by a combination of the Orr mechanism and wall-normal velocity linear superposition near the wall. Finally, a metasurface comprised of an array of streamwise-distributed PCs is evaluated, resulting in an amplitude growth delay of 11.3% of the TS wavelength along the metasurface extent.

Effects of the tributary channel and water catchment area on rinnenkarren development (Totes Gebirge, Austria)

ABSTRACT The goal of this study is to interpret the cross-sectional increases of rinnenkarren systems with the use of analytical model and CFD simulation. In rinnenkarren, water accumulation from the catchment was approximated using an analytical method based on field data. The length of eddies appearing at tributary junctions was studied by CFD in model channels. The results of the analytical and numerical models were compared against morphometrical parameters of rinnenkarren surveyed in the Totes Gebirge (Austria). It is found that there is a relationship between catchment size and channel development. Along small catchments, channel development is random. However, channel development along large catchments is controlled by water concentration. Decrease in the slope angle of the catchment results in an increase in the volume of water entering the channel and development of tributary channels. When water inflow is not concentrated in a single place, several smaller tributary channels emerge. When it is concentrated, only one large-sized and long tributary develops. At the junctions of large tributaries significant vorticity was identified in the CFD models. In addition to the previous model studies, the similarity between the lengths of the simulated vorticity sections and the local field hollowings was revealed.

Peukert Generalized Equations Applicability with Due Consideration of Internal Resistance of Automotive-Grade Lithium-Ion Batteries for Their Capacity Evaluation

In this paper, the applicability of the Peukert equation and its generalizations were investigated for capacity evaluation of automotive-grade lithium-ion batteries. It is proved that the classical Peukert equation is applicable within the range of the discharge currents from 0.2Cn to 2Cn (Cn is the nominal battery capacity). As a rule, the operating currents of many automotive-grade lithium-ion batteries are exactly within this range of the discharge currents. That is why, successfully, the classical Peukert equation is used in many analytical models developed for these batteries. The generalized Peukert equation C = Cm/(1 + (i/i0)n) is applicable within the discharge currents range from zero to approximately 10Cn. All kinds of operating discharge currents (including both very small ones and powerful short-term bursts) fall into this discharge currents range. The modified Peukert equation C = Cm(1 − i/i1)/((1 − i/i1) + (i/i0)n) is applicable at any discharge currents. This equation takes into account the battery’s internal resistance and has the smallest error of experimental data approximation. That is why the discussed modified Peukert equation is most preferable for use in analytical models of automotive-grade lithium-ion batteries. The paper shows that all the parameters of the generalized Peukert equations have a clear electrochemical meaning in contrast to the classical Peukert equation, where all the parameters are just empirical constants.

Wake flow patterns and turbulence around naturally deposited and installed trees in a gravel bed river

AbstractLarge wood structures, such as wood fragments, debris jams, or entire trees, create flow and habitat diversity in rivers. A key flow feature associated with such structures is the wake, characterised by a core zone of reduced velocity and shear layers at its margins. Wakes are largely controlled by geometric and structural properties of the wood. In the present study, the flow patterns and turbulence created by different wood structures were compared at two study sites: naturally eroded and fragmented oaks (Site A) and artificial poplar installations (Site B). Flow and turbulence were quantified using pointwise velocity measurements with acoustic Doppler velocimeters (ADVs) and surface particle tracking velocimetry (SPTV). The measured flow patterns exhibited similarities with shallow porous wakes that feature fluid advection through the structure into the wake core downstream. Two additional features of wood structures were identified in the present study: (i) the growth of the shear layers was hindered by bed friction like for shallow mixing layers and (ii) the presence of a tree stem and sediment deposit in the wake centre delayed or even suppressed the interaction of the shear layers and vortex street formation similar to a wake‐splitter plate. Methodologically, the combined ADV/SPTV measurement approach and the use of analytical models for shallow mixing layers proved to be highly valuable to decipher the complex flow patterns around wood structures in the field.

Автоматизация процесса экологического мониторинга в особо охраняемых природных территориях Российской Федерации на базе системы управления контентом Directum RX

For organizations that execute control over specially protected natural areas of the Russian Federation, the task of consolidating data on ongoing observations is relevant. These data, called the chronicles of nature, for a long time were kept in a simplified, paper form and did not have a clear structure. The task of automating business processes for collecting data and exchanging this data between members of the scientific community, as well as building models necessary for the scientific departments of parks and reserves, is important and relevant. In this connection, we see it relevant to consider automating the process of environmental monitoring by developing an electronic document management module based on the integration platform Directum RX business solutions. The purpose of the research is to automate the eco-monitoring process based on the Directum RX platform, which allows to build a corporate content management system, as well as create a full-fledged data storage and retrieval system for collecting information about observations. The article describes the role model for working with the system, the system architecture and the developed components of the "Ecomonitoring" module based on the Directum RX platform. For this, a structural method was used, by dividing the task into many independent stages available for understanding and solving and hierarchical ordering. Integration with the Yandex weather service has been developed for further use in analytical models. A solution has been developed to manage the universal classifier of animals in accordance with the classifier of biological taxonomy accepted in the world. The automation of user actions for collecting and processing information about observations is demonstrated. As a result, the process of environmental monitoring was automated in one of the reserves of the Russian Federation.

Nurses’ Perception of Clinical Decision Making Ability: A CrossSectional Survey

Nursing practice today is becoming more complex with advancement in technology and changing health care needs of the population. There is an increased demand on the health care service requirements and competencies from the health care professionals. Nurses being the key health care providers are expected to be specialised in task of decision making. Hence, understanding the type of clinical decision making (CDM) abilities in solving problems in practice may be helpful in education and research. This study emphasises on the CDM ability used by nurses in practice and its association with their demographic variables. A crosssectional survey was carried out among 94 nurses in a selected tertiary care hospital of Udupi district (Karnataka). A 24-item CDM instrument was used for evaluation when caring for a patient with post-operative pain. Nurses’ decision making was categorised as analytical (79). The collected data were analysed with descriptive frequencies and one way ANOVA. All the participants reported the use of analytical model of decision making. Age was associated with analytical model of clinical decision making (F=2.063, p=0.012). Incorporation of the kinds of decision making abilities used by nurses will help bring improvement in the nursing curriculum thus expanding the clinical decision making abilities of future nurses.

77.3-GHz Standing-Wave Oscillator Based on an Asymmetrical Tunable Slow-Wave Coplanar Stripline Resonator

In this paper, the design of a 77.3 GHz Standing-Wave oscillator (SWO) is presented. The proposed SWO relies on the distribution of varactors along an asymmetrical slow-wave coplanar stripline, which enables the improvement of the quality factor of the tunable resonator, resulting in superior performance in terms of phase noise and DC-to-RF efficiency. The design methodology, based on the use of analytical models and abaci, is presented in detail and applied to a design in a 55-nm CMOS technology. With a core consumption of 15.1 mW, the proposed SWO operates from 76.09 GHz to 78.60 GHz and presents a phase noise of -115.1 dBc/Hz at 10 MHz offset, leading to a Figure of Merit (FOM) of -181 dBc/Hz. The DC-to-RF efficiency obtained is 3.1%.

Analytical models to estimate the structural behaviour of fused deposition modelling components

PurposeThe purpose of this study is to evaluate the capability and performance of analytical models to predict the structural mechanical behaviour of parts fabricated by fused deposition modelling (FDM).Design/methodology/approachA total of eight existing and newly proposed analytical models, tailored to satisfy the structural behaviour of FDM parts, are evaluated in terms of their capability to predict the ultimate tensile stress (UTS) and the elastic modulus (E) of parts made of polylactic acid (PLA) by the FDM process. This evaluation is made by comparing the structural properties predicted by these models with the experimental results obtained from tensile tests on FDM specimens fabricated with variable infill percentage, perimeter layers and build orientation.FindingsSome analytical models are able to predict with high accuracy (prediction errors smaller than 5%) the structural behaviour of FDM and categories of similar additive manufactured parts. The most accurate model is Gibson’s and Ashby, followed by the efficiency model and the two new proposed exponential and variant Duckworth models.Research limitations/implicationsThe study has been limited to uniaxial loading conditions along three different build orientations.Practical implicationsThe structural properties of FDM parts can be predicted by analytical models based on the process parameters and material properties. Product engineers can use these models during the design for the additive manufacturing process.Originality/valueExisting methods to estimate the structural properties of FDM parts are based on experimental tests; however, such methods are time-consuming and costly. In this work, the use of analytical models to predict the structural properties of FDM parts is proposed and evaluated.

A deterministic semi-infinite global optimization method to design slotless permanent magnet machines

PurposeIn this work, a method to design a slotless permanent magnet machine (SPMM) based on the joint use of an analytical model and deterministic global optimization algorithms is addressed. The purpose of this study is to propose to include torque ripples as an extra constraint in the optimization phase involving de facto the study of a semi-infinite optimization problem.Design/methodology/approachBased on the use of a well-known analytical model describing the electromagnetic behavior of an SPMM, this analytical model has been supplemented by the calculus of the dynamic torque and its ripples to carry out a more accurate optimized sizing method of such an electromechanical converter. As a consequence, the calculated torque depends on a continuous variable, namely, the rotor angular position, resulting in the definition of a semi-infinite optimization problem. The way to solve this kind of semi-infinite problem by discretizing the rotor angular position by using a deterministic global optimization solver, that is to say COUENNE, via the AMPL modeling language is addressed.FindingsIn this study, the proposed approach is validated on some numerical tests based on the minimization of the magnet volume. Efficient global optimal solutions with torque ripples about 5% (instead of 30%) can be so obtained.Research limitations/implicationsThe analytical model does not use results from the solution of two-dimensional field equations. A strong assumption is put forward to approximate the distribution of the magnetic flux density in the air gap of the SPMM.Originality/valueThe problem to design an SPMM can be efficiently formulated as a semi-infinite global optimization problem. This kind of optimization problems are hard to solve because they involve an infinity of constraints (coming from a constraint on the torque ripple). The authors show in this paper that by using analytical models, a discretization method and a deterministic global optimization code COUENNE, this problem is efficiently tackled. Some numerical results show that the deterministic global solution of the design can be reached even if the step of discretization is small.

Analytical Models of Axially Loaded Blind Rivets Used with Sandwich Beams

The paper presents the novel use of analytical models of a beam on an elastic foundation. The one-parameter model (Winkler model) and the two-parameter models (Filonenko-Borodich and Pasternak models) were investigated. These models were used to describe the elastic response of axially loaded blind rivets used with sandwich structures. The elastic response related to the elastic strain energy is mentioned in the paper as the resilience modulus of the connection. The databases from laboratory pull-out tests were used to verify these models. One type of blind rivet (aluminum, with three clamping arms) and one type of sandwich beam were used. The sandwich beams used in the experiments consisted of two thin-walled and stiff external facings (zinc-coated steel) and a thick, soft core (polyisocyanurate foam—PIR). In the test the sandwich beams were subjected to static, axial pull-out loading. The research provides the quantitative comparison between the laboratory experiment and the analytical solutions from models adopted for this type of connection. Additionally, the failure mechanisms, the secant stiffness at the ultimate capacity, and the strain energy capacity of the elastic foundation at failure are considered. To the author’s knowledge, this approach has not been described in the literature so far.

Discriminatory models as a tool for bankruptcy risk assessment industrial capital groups – the chemical sector

The article presents research on the use of discriminatory models in the assessment of the risk of bankruptcy of industrial capital groups operating in the Polish chemical sector. The research work was focused on examining the efficiency and effectiveness of the use of analytical models in forecasting bankruptcies of multi-entity organizations by tally and comparing the results calculated for the capital group and the parent company. The analysis uses models for assessing and forecasting the economic and financial condition of enterprises by Polish scientists, which are dedicated to domestic companies operating in the Polish economic realities. Research works on their development were carried out in the main research and development centers of universities.

Web Scraping for Hospitality Research: Overview, Opportunities, and Implications

As consumers increasingly research and purchase hospitality and travel services online, new research opportunities have become available to hospitality academics. There is a growing interest in understanding the online travel marketplace among hospitality researchers. Although many researchers have attempted to better understand the online travel market through the use of analytical models, experiments, or survey collection, these studies often fail to capture the full complexity of the market. Academics often rely upon survey data or experiments owing to their ease of collection or potentially to the difficulty in assembling online data. In this study, we hope to equip hospitality researchers with the tools and methods to augment their traditional data sources with the readily available data that consumers use to make their travel choices. In this article, we provide a guideline (and Python code) for how to best collect/scrape publicly available online hotel data. We focus on the collection of online data across numerous platforms, including online travel agents, review sites, and hotel brand sites. We outline some exciting possibilities regarding how these data sources might be utilized, as well as discuss some of the caveats that have to be considered when analyzing online data.

Automatic classification of nuclear physics data via a Constrained Evolutionary Clustering approach

This paper presents an automatic method for data classification in nuclear physics experiments based on evolutionary computing and vector quantization. The major novelties of our approach are the fully automatic mechanism and the use of analytical models to provide physics constraints, yielding to a fast and physically reliable classification with nearly-zero human supervision. Our method is successfully validated using experimental data produced by stacks of semiconducting detectors. The resulting classification is highly satisfactory for all explored cases and is particularly robust to noise. The algorithm is suitable to be integrated in the online and offline analysis software of existing large complexity detection arrays for the study of nucleus–nucleus collisions at low and intermediate energies.

Kinetic Monte Carlo simulations of ionic conductivity in oxygen ion conductors

Ionic conductivities of solid-state materials are crucial for the performance of various applications ranging from batteries and fuel cells to resistive switching devices. The macroscopic ionic conductivity results directly from the microscopic energy landscape of ion diffusion. Lattice site energies and migration barriers depend on lattice defects such as vacancies and dopant ions in the local environment. The multiplicity of possible defect interactions with the migrating ion impedes the use of analytic models. While ab initio methods allow the calculation of the microscopic energy barriers for individual jumps, calculations of the macroscopic conductivity are computational very demanding, especially for more than 250 different materials and their possible ionic configurations as presented in this study. Kinetic Monte Carlo simulations allow the simulation of the ionic conductivity based on ab initio data and bridge the gap between microscopic jump events and the macroscopic conductivity. In this work, we discuss the Kinetic Monte Carlo method and its application to oxygen ion conductors for the example of doped ceria. We demonstrate how Kinetic Monte Carlo simulations can be accelerated to be 100 times faster with preserved high accuracy. Moreover, we report how the accuracy of Kinetic Monte Carlo simulations is improved with a large interaction radius and minimal computational expenses.

Tooling-up for infectious disease transmission modelling

In this introduction to the Special Issue on methods for modelling of infectious disease epidemiology we provide a commentary and overview of the field. We suggest that the field has been through three revolutions that have focussed on specific methodological developments; disease dynamics and heterogeneity, advanced computing and inference, and complexity and application to the real-world. Infectious disease dynamics and heterogeneity dominated until the 1980s where the use of analytical models illustrated fundamental concepts such as herd immunity. The second revolution embraced the integration of data with models and the increased use of computing. From the turn of the century an emergence of novel datasets enabled improved modelling of real-world complexity. The emergence of more complex data that reflect the real-world heterogeneities in transmission resulted in the development of improved inference methods such as particle filtering. Each of these three revolutions have always kept the understanding of infectious disease spread as its motivation but have been developed through the use of new techniques, tools and the availability of data. We conclude by providing a commentary on what the next revoluition in infectious disease modelling may be.

The behaviour of geosynthetic-reinforced pile foundation under long-term dynamic loads: model tests

In order to reduce the effects of the low strength and high compressibility of soft soil, geosynthetic-reinforced pile foundations (GRPF) are widely applied for the construction of high-speed railways. Though its reinforcement effect is proved acceptable in practices so far, it is unclear whether it will keep this performance as the train speed continues increasing. Since it is impossible to study the problem in field tests, only mathematical and physical models can be used. However, the nonlinear behaviour of the soft soil complicates the use of analytical models. Therefore, this paper presents a small-scale model test to study the possible changes in stress distribution and deformation in the GRPF under increasing dynamic loads. One test with a natural foundation, without piles or geosynthetic, shows the difference with a similar construction with GRPF foundation. Furthermore, three GRPF tests show the influence of the embankment thickness. The results show the long-term dynamic loading significantly affects the dynamic stress and displacements of the subsoil between the piles of the GRPF. This effect can be divided into three stages with an increasing level of load amplitude: no impact, advantageous impact, and adverse impact. When the dynamic load reaches the adverse impact stage, the long-term dynamic loads reduce the dynamic pile–soil stress ratio, which means that more soil settlement will develop, because more dynamic stress is applied to the soft soil. The test results show that the reduction in dynamic stress on the subsoil in the GRPF construction is clearly lower than the dynamic stress on the natural foundation, due to the existence of rigid piles. Moreover, a thicker embankment gives significantly lower dynamic stresses on the subsoil between the piles. For the thickest embankment tested, the adverse impact stage was not found at all: the arching kept enhancing under long-term dynamic loading with high load amplitudes.