Dimensionless Index Research Articles

On the Computational Study of a Fully Wetted Longitudinal Porous Heat Exchanger Using a Machine Learning Approach.

The present study concerns the modeling of the thermal behavior of a porous longitudinal fin under fully wetted conditions with linear, quadratic, and exponential thermal conductivities surrounded by environments that are convective, conductive, and radiative. Porous fins are widely used in various engineering and everyday life applications. The Darcy model was used to formulate the governing non-linear singular differential equation for the heat transfer phenomenon in the fin. The universal approximation power of multilayer perceptron artificial neural networks (ANN) was applied to establish a model of approximate solutions for the singular non-linear boundary value problem. The optimization strategy of a sports-inspired meta-heuristic paradigm, the Tiki-Taka algorithm (TTA) with sequential quadratic programming (SQP), was utilized to determine the thermal performance and the effective use of fins for diverse values of physical parameters, such as parameter for the moist porous medium, dimensionless ambient temperature, radiation coefficient, power index, in-homogeneity index, convection coefficient, and dimensionless temperature. The results of the designed ANN-TTA-SQP algorithm were validated by comparison with state-of-the-art techniques, including the whale optimization algorithm (WOA), cuckoo search algorithm (CSA), grey wolf optimization (GWO) algorithm, particle swarm optimization (PSO) algorithm, and machine learning algorithms. The percentage of absolute errors and the mean square error in the solutions of the proposed technique were found to lie between to and to , respectively. A comprehensive study of graphs, statistics of the solutions, and errors demonstrated that the proposed scheme’s results were accurate, stable, and reliable. It was concluded that the pace at which heat is transferred from the surface of the fin to the surrounding environment increases in proportion to the degree to which the wet porosity parameter is increased. At the same time, inverse behavior was observed for increase in the power index. The results obtained may support the structural design of thermally effective cooling methods for various electronic consumer devices.

Application of multi-kernel relevance vector machine and data pre-processing by complementary ensemble empirical mode decomposition and mutual dimensionless in fault diagnosis

Resistance signals of a faulty building electrical system contain a large amount of information about the electrical systems operating status. However, it is difficult to extract the fault features completely because of their characteristics of nonlinearity and non-stationarity which brings a problem of a relatively low fault identification rate of the current fault diagnosis methods based on pattern recognition. Aiming at improving the accuracy of fault diagnosis further, this paper proposes a fault diagnosis method of a building electrical system based on the complementary ensemble empirical mode decomposition and mutual dimensionless index extraction (CEEMD-MDI) combined with the multi-kernel relevance vector machine (MK-RVM). First, the resistance signals of a faulty building electrical system are decomposed into a series of intrinsic mode functions (IMFs) by using an adaptive decomposition ability of the CEEMD. Second, the IMFs are used to extract the MDI and to form a feature vector with the resistance signal. Finally, the processed feature vector is input into the MK-RVM for modeling, and the fault diagnosis result of the building electrical system is provided in the form of a probability output. The experimental results show that the fault diagnosis accuracy rate of the proposed method based on CEEMD-MDI and MK-RVM can reach 97.22%, which has better fault diagnosis performance compared with other methods.

Site Selection for a Deep Geological Repository in Switzerland: The Role of Performance Assessment Modeling

In the development of deep geological repositories (DGRs), performance assessment modeling is used to evaluate the integrity and performance of the engineered and geological barriers for thousands or millions of years of evolution of the disposal system. To evaluate the suitability of a site for a DGR, geoscientific data from dedicated site investigation programs are integrated into site-specific assessments. This paper presents the development and implementation of a modeling workflow aimed at comparing three potential siting areas for a DGR in Switzerland from the viewpoint of long-term safety and technical feasibility. The workflow follows the guidelines of the national regulator addressing safety relevant criteria such as the barrier efficiency of the host rock and its mechanical and chemical integrity in response to repository-induced influences and the long-term stability of the repository site over geological scales. In the regulatory requirements, the role of parametric, conceptual, and scenario uncertainty has been identified as an issue of special importance in the site selection process. The assessment approach comprises a portfolio of numerical models for the simulation of solute, gas and heat transport in the repository nearfield. The modeling was performed with deterministic as well as probabilistic variants integrated in an indicator-based approach that allows the consistent comparison of the candidate sites using quantitative dimensionless performance indices. The model-based assessment of the sites allows a traceable, transparent, and verifiable implementation of the site selection process.

Dissociation of dark matter and gas in cosmic large-scale structure

ABSTRACT The partial spatial separation of cold dark matter (DM) and gas is a ubiquitous feature in the formation of cosmic large-scale structure. This separation, termed dissociation, is prominent in galaxy clusters that formed through collisions of massive progenitors, such as the famous ‘Bullet’ cluster. A direct comparison of the incidence of such dissociated structures with theoretical predictions is challenged by the rarity of strongly dissociated systems and the difficulty to quantify dissociation. This paper introduces a well-defined dimension-less dissociation index S ∈ [ − 1, 1] that encodes the quadrupole difference between DM and gas in a custom region. Using a simulation of cosmic large-scale structure with cold DM and ideal non-radiating gas, in ΛCDM cosmology, we find that 90 per cent of the haloes are positively dissociated (S > 0), meaning their DM is more elongated than their gas. The spatial density of highly dissociated massive structures appears consistent with observations. Through idealized N-body + SPH simulations of colliding gaseous DM haloes, we further explore the details of how ram-pressure causes dissociation in binary collisions. A suite of 300 such simulations reveals a scale-free relation between the orbital parameters of binary collisions and the resulting dissociation. Building on this relation, we conclude that the frequency of dissociated structures in non-radiative cosmological simulations is nearly fully accounted for by the major (mass ratio >1:10) binary collisions predicted by such simulations. In principle, our results allow us to constrain the orbital parameters that produced specific observed dissociated clusters.

Assessment of the landslide dams in Western Austria, Bavaria and Northern Italy (part of the Eastern Alps): Data inventory development and application of geomorphic indices

Landslide dams pose significant hazards towards their upstream and downstream areas due to damming and flooding. Case studies and the use of geomorphic indices, which are developed based on large datasets, are two common approaches in the stability assessment of landslide dams. To gain an insight into the evolution of landslide dams within a part of the Eastern Alps and to provide a basis for further studies on this topic, a data inventory including 73 landslide dams is presented. The database covers sites in Western Austria, Bavaria and Northern Italy, containing 39 descriptive and quantitative parameters gathered in five categories of location, landslide, dam, lake, and catchment. The methodologies utilized for parameter definition follow a simple and consistent procedure described in detail for one case study, the Wiese landslide in Tyrol (Austria). Statistical assessment of the geometric parameters indicated an acceptable collation between mean values of the developed inventory and dataset of other geographical regions. Moreover, by developing a correlation matrix of the quantitative fields, landslide dam parameters showed a fairly strong correlation with the landslide and backwater lake parameters. However, they appear to be statistically independent of the catchment area characteristics. The applicability of the previously developed geomorphic indices is evaluated by plotting the current data and determining the upper and lower bounds of the stable and unstable domains regarding a 95 % confidence level of the mean value. The best applicability is obtained out of the blockage and dimensionless blockage indices. Further, a set of catchment ruggedness-based indices are developed based on the collected data. The indices act upon the catchment properties as driving forces and three different sets of characteristics of the dam and landslide as resisting forces. The reliability of these indices is confirmed by obtaining the adjusted R2 within 70–85 %, narrowing down the uncertain domain on the graphs in comparison to the reviewed literature, and the applicability of them on the current database. Each catchment ruggedness-based index is suitable to predict the evolution of the dams and backwater lakes at the time of occurrence depending on the available data.

Three-dimensional stress rotation and control mechanism of deep tunneling incorporating generalized Zhang–Zhu strength-based forward analysis

Deep rock tunneling exhibits a significant three-dimensional (3D) space effect. The complex stress path and extrusion deformation during excavation are the most significant and decisive factors in the stability and construction safety of a deep tunnel. 3D and forward numerical analyses based on generalized Zhang–Zhu (GZZ) strength criterion are performed to investigate the principal stress rotation behavior and active control mechanism during deep tunneling. The surrounding rock element experiences significant stress rotations because of the sharply increased shear stress (τry) near the tunnel face. A dimensionless stress index (τry/I1) is proposed to quantitatively evaluate the principal stress rotation during excavation. τry/I1 increases with increasing buried depth, and the deep tunnel presents significant principal stress rotation that reaches a large τry/I1 value. The mechanical behavior of the advanced core rock is primarily affected by the strengthening parameter, geological strength index (GSI). Strengthening of the core rock can greatly improve the stress conditions and mechanical behavior, increase the strength of the rock mass, and reduce the stress rotation. The pre-extrusion deformation of the core rock and pre-convergence of the surrounding rock are discovered to follow a consistency law, which suggests that the pre-convergence deformation and surrounding rock stability near the tunnel face depend on the extrusion deformation of the tunnel face. The GZZ strength-based 3D forward analysis and stress control method proposed in this study can enhance the design and construction of deep and ultra-deep tunnels by weakening the 3D space effect (e.g., tunnel face extrusion and stress rotation) and exerting the strength potential (self-bearing capacity) of a rock mass.

Parallel computing of building fire using a domain decomposition method based on load balancing

Parallel computing can provide a practical way in performing building fire simulation which often contains an immense amount of grids. Four dimensionless indices were presented for the evaluation of the load balance. According to the four indices, an empirical load description function was established based on the orthogonal experimental method. A domain decomposition method based on load balancing (DDMBLB) was then proposed. A preprocessing tool based on the DDMBLB method was developed, which can decompose the domain automatically with load balancing. Parallel numerical simulations based on the DDMBLB method were performed on an express logistics center fire. The comparison of DDMBLB method and the commonly-used Recursive Coordinate Dichotomy (RCB) method was done to analyze the computing time, speedup ratio and parallel efficiency. The DDMBLB method can significantly reduce the fire simulation time compared to the RCB method. It has a better domain decomposition effect than the RCB method with a greater speedup ration and a higher parallel efficiency.

High-throughput screening of surface roughness during additive manufacturing

Smooth surfaces in the printed parts are essential for long fatigue life and high dimensional accuracy. They are currently achieved by post-process machining and grinding of external surfaces that add extra costs. Mitigating the surface roughness of internal channels remains a challenge. Here we use a high-throughput screening approach that analyzes the value of a dimensionless index for many experiments and provides a pathway for reducing the surface roughness without the need for post-processing. The index is derived by dimensional analysis of causative variables that affect the roughness of the surface such as heat input, powder diameter, layer thickness, pool aspect ratio, Marangoni force, contact angle, and enthalpy of melting of alloys. Using the results of high-throughput screening, we develop easy-to-use process maps that are consistent with the experimental observations. Among the causative variables, heat input and the contact angle of the molten material with the substrate have the highest and lowest influence on the smoothness of printed surfaces. An aluminum alloy, AlSi10Mg is found to be the best choice for printing smooth surfaces among the four alloys considered here. These findings can improve the surface quality of additively manufactured parts that now significantly hinder their wider industrial adaptation.

Relaxation Dynamics of Biomass-Derived Copolymers With Promising Gas-Barrier Properties.

This article presents an experimental study on the relaxation dynamics of a series of random copolymers based on bio-friendly comonomers with interesting gas barrier properties. We analyze the relaxation response in the glassy and ultraviscous regime of poly (trimethylene furanoate/sebacate) random copolymers via dielectric spectroscopy. We report lower values of dynamic fragility [a dimensionless index introduced in 1985 (Angell, Relaxations in Complex Systems, 1985)] in comparison to popular polyesters widely used in industry, such as poly (ethylene terephthalate), suggesting that the amorphous phase of these furanoate-based polyesters adopt an efficient chain packing. This is consistent with their low permeability to gases. We also discuss on different equations (phenomenological and theory-based approaches) for fitting the temperature-evolution of the alpha relaxation time.

Using the space debris flux to assess the criticality of the environment in low Earth orbit

In this paper we introduce a new index for evaluating the likelihood of accidental collisions leading to the complete destruction of intact objects in a volume of space in low Earth orbit (LEO). The proposed index is therefore not intended to assess the criticality of individual objects or missions, but rather to estimate the global impact of space activities on a given region of space. Moreover, the new index has been designed to be objective, as simple as possible, built from easily accessible data, as well as smoothly reproducible by third parties. Named “volumetric collision rate index”, it has been developed starting from analytical equations expressing the collision rate as a function of the fluxes of intact objects and cataloged debris pieces. The application of reasonable simplifying assumptions and approximations has finally made it possible to define a dimensionless index that explicitly depends only on the spatial densities of intact objects and cataloged debris pieces. It has therefore been applied to the LEO environment, analyzing its evolution from mid-2008 to mid-2020, a crucial period characterized by an impressive change of space activity patterns, with the launch of lots of small satellites and mega-constellations. We also discuss how the index can be further improved, taking into account the maneuverable satellites, which do not contribute to the collision rate, and the increasing number of cubesats, which in many respects are more similar to debris, finally presenting a preliminary analysis in this direction.

Quantitative assessment of a pediatric nociception monitor in children under sevoflurane anesthesia

IntroductionIntraoperative monitoring of nociception has recently made substantial progress in adult anesthesia. In contrast, pediatric data are scarce. Newborn-Infant Parasympathetic Evaluation (NIPE index, Mdoloris Medical Systems, Loos, France) is the...

Resilience deficit index for quantification of resilience

After a brief overview of how the dimensionless resilience index has been calculated in the past for buildings, and some of the shortcomings of that approach, the use of a resilience deficit index is advocated to overcome some of these shortcomings. An example is provided and the pros and cons of each approach are discussed, with broad recommendations applicable to the quantification of building resilience.

A width‐based approach to estimating historical changes in coarse sediment fluxes at river reach and network scales

AbstractKnowledge about historical changes in sediment fluxes in most coarse‐bedded rivers worldwide is extremely limited. In consideration of this deficiency, we developed a width‐based approach to estimating multi‐decade changes in coarse sediment fluxes occurring at reaches of the Po River and 21 of its tributaries in northern Italy. The estimation was based on temporal variations in the reach‐averaged width of the river's active channel, and such width was expressed through a dimensionless index of coarse bed material load (Iq). The index was determined in two periods: 1954–1998 and 1998–2020. Statistically significant relationships were found between temporal variations in Iq occurring in reaches of the Po River and at key locations of each specific reach (i.e., upstream reaches and tributaries). Such evidence of coherent changes in sediment transfer through space and time led us to conclude that Iq variations can be regarded as a reliable proxy for historical changes in sediment transport in a river reach. The application of the approach to the investigation of the Po River catchment provided new insights into the historical changes characterizing coarse sediment fluxes along the river and its major tributaries. From 1954 to 1998, an average decrease in coarse sediment fluxes of about −20% and −30% occurred along the river and the terminal sectors of its tributaries, respectively. The estimations showed that coarse sediment fluxes exhibited a slightly lower decrease in the last two decades, with sediment flux recovery occurring only in some tributaries. The results suggest that a profound change in sediment dynamics and fluxes has occurred, and is likely still ongoing, in the Po River system, despite the decrease in human disturbances (e.g., in‐channel sediment mining) in more recent times.

The enhancement of fault detection for rolling bearing via optimized VMD and TQWT based sparse code shrinkage

A typical vibration signal of fault bearing is composed of periodic repetitive transient impulses, multiple vibration disturbance and background noise. Variational mode decomposition (VMD) represents a potential tool for analyzing such signals. However, the reasonable selection of VMD algorithm parameters hinders its application in mechanical signal processing to a certain extent. According to the specific characteristics of rolling bearing fault signal, the composite dimensionless index is constructed as the objective function to ensure the optimal decomposition of VMD. To further enhance the fault characteristics, the tunable Q-factor wavelet transform (TQWT) along with sparse code shrinkage is proposed to denoise the modal components containing periodic impulses, which further highlights the impulses and improves the sparseness of fault signal. Simulation and experimental signal analysis verify the effectiveness and reliability of this method. The results show that the use of optimized VMD and TQWT based sparse code shrinkage dramatically sharpens the impulses from the mixed signal with noise interference and increases the sparseness to a level.

Proposed Conceptual Framework to Design Artificial Reefs Based on Particular Ecosystem Ecology Traits.

Simple SummaryArtificial reefs improve the yield of artisanal fishing grounds by creating habitats with enhanced productivity, similar to those of natural reefs. For an adequate definition of an artificial reef, all its pathways of interaction with the ecosystem must be quantitatively assessed. In this way, the final design will lead to an increase in the production of services. Therefore, this study presents the MEEM tool as well as the AREIT index. Through the former, it is possible to obtain different reef solutions, while the index allows the user to select the best alternative by taking into account the specific situation of the ecosystem to be enhanced. The AREIT index facilitates the decision-making process by means of a three-dimensional graphical representation, based on the three aspects of greatest relevance for the ecosystem: energy, nutrient circulation and the presence of cavities for the shelter of species, in particular those of fishing interest. The definition process ends with the application of a procedure for calculating the stability of the final design under the action of waves and currents.Overfishing and pollution have led to marine habitat degradation, and as a result, marine fisheries are now in decline. Consequently, there is a real need to enhance marine ecosystems while halting the decline of fish stocks and boosting artisanal fishing. Under these circumstances, artificial reefs (ARs) have emerged as a promising option. Nevertheless, their performance is traditionally assessed years after installation, through experimental and field observations. It is now necessary to adopt an alternative approach, adapting the design of artificial reefs to the specific characteristics of the ecosystem to be enhanced. In this way, it will be possible to determine the potential positive impacts of ARs before their installation. This paper presents a general and integrated conceptual framework to assist in the design of AR units by adopting an ecosystem ecology (EE) perspective. It consists of three main parts. In the first one, starting from an initial geometry, EE principles are used to include modifications with the aim of improving autotrophic resource pathways (additional substrata and increased nutrient circulation) and leading to a habitat enhancement (more shelter for individuals). The second part of the framework is a new dimensionless index that allows the user to select the best AR unit design from different alternatives. The potential impacts on the ecosystem in terms of energy, nutrient cycling and shelter are considered for such a purpose. Finally, a general hydrodynamic methodology to study the stability of the selected AR unit design, considering the effect of high waves under severe storms, is proposed. The framework is applied through a case study for Galician estuaries.

Tracking the location of bearing outer raceway defects using multidimensional synchronous signal fusion and tensor Rank-1 decomposition

A generalised Warblet tensor rank-1 decomposition (GWTTR1) method is developed in this study to realise location diagnosis for bearing outer raceway defects in low signal-to-noise ratio (SNR) scenarios. Firstly, a novel third-order tensor model (channel–time–frequency) with comprehensive information is established to reveal key information hidden in multidimensional signals and realise feature fusion among two-channel signals. Secondly, the defect characteristic frequency and correlation coefficient between rank-1 tensors are introduced as optimal selection indices for the factor matrix to decompose the tensor model effectively and overcome the inherent shortcomings of decomposition. Thirdly, a novel location diagnosis dimensionless index, namely, the horizontal-vertical synchronisation factor (HVSF), is proposed for the optimised tensor model. Finally, the performance of the proposed GWTTR1 method and novel HVSF index in location diagnosis for bearing outer raceway defects and noise interference elimination is evaluated comprehensively with low SNR dynamic simulation and experimental signals. The comparison results reveal that the GWTTR1 method outperforms existing noise reduction techniques.

Prognosis of Paradoxical Low-Flow Low-Gradient Aortic Stenosis: A Severe, Non-critical Form, With Surgical Treatment Benefits.

ObjectivesTo determine the risk of mortality and need for aortic valve replacement (AVR) in patients with low-flow low-gradient (LFLG) aortic stenosis (AS).MethodsA longitudinal multicentre study including consecutive patients with severe AS (aortic valve area [AVA] < 1.0 cm2) and normal left ventricular ejection fraction (LVEF). Patients were classified as: high-gradient (HG, mean gradient ≥ 40 mmHg), normal-flow low-gradient (NFLG, mean gradient < 40 mmHg, indexed systolic volume (SVi) > 35 ml/m2) and LFLG (mean gradient < 40 mmHg, SVi ≤ 35 ml/m2).ResultsOf 1,391 patients, 147 (10.5%) had LFLG, 752 (54.1%) HG, and 492 (35.4%) NFLG. Echocardiographic parameters of the LFLG group showed similar AVA to the HG group but with less severity in the dimensionless index, calcification, and hypertrophy. The HG group required AVR earlier than NFLG (p < 0.001) and LFLG (p < 0.001), with no differences between LFLG and NFLG groups (p = 0.358). Overall mortality was 27.7% (CI 95% 25.3–30.1) with no differences among groups (p = 0.319). The impact of AVR in terms of overall mortality reduction was observed the most in patients with HG (hazard ratio [HR]: 0.17; 95% CI: 0.12–0.23; p < 0.001), followed by patients with LFLG (HR: 0.25; 95% CI: 0.13–0.49; p < 0.001), and finally patients with NFLG (HR: 0.29; 95% CI: 0.20–0.44; p < 0.001), with a risk reduction of 84, 75, and 71%, respectively.ConclusionsParadoxical LFLG AS affects 10.5% of severe AS, and has a lower need for AVR than the HG group and similar to the NFLG group, with no differences in mortality. AVR had a lower impact on LFLG AS compared with HG AS. Therefore, the findings of the present study showed LFLG AS to have an intermediate clinical risk profile between the HG and NFHG groups.

Effectiveness and Efficiency of Externally Bonded CFRP Sheets for Shear Strengthening of RC Beam-Column Joints.

To develop feasible carbon fiber reinforced polymer (CFRP) retrofit schemes for the shear strengthening of real three-dimensional reinforced concrete (RC) beam-column joints, a series of parameters in relation to the contributions of the CFRP sheets externally bonded to joint panels was numerically investigated in this study. The parameters include CFRP reinforcement ratio, CFRP layout, transverse beam-to-joint panel width ratio, transverse beam-to-joint panel height ratio, location of transverse beam, and number of transverse beams. Strengthening efficiency, a new dimensionless index, was introduced to evaluate the residual effect of a CFRP-strengthening system weakened by the presence of transverse beams in comparison with the increase in joint shear capacity in relation to the one-way counterpart. The results obtained from 44 nonlinear finite element models, which were calibrated against experimental observations, confirmed the effectiveness of the CFRP strengthening technique with regard to the relatively wide ranges of the parameters. The significant differences among the roles of the parameters were revealed, and the reasons behind the differences were analyzed. Furthermore, the shear mechanism of the CFRP-retrofitted joint panels was discussed with the proposed strut-and-tie model.

Fuzzy AHP-Based Design Performance Index for Evaluation of Ferries

Within waterborne public transportation (WPT), one often observes a mismatch between the operational requirements and ferry characteristics. A method to holistically evaluate ferries with respect to local requirements could lead to tailored procurement and targeted refurbishment of existing fleet. In this study, we develop a structure for operational requirements and use it as a basis for a ferry evaluation methodology. The requirements’ structure follows a three-level hierarchy starting from broad vessel design to mandatory requirements to performance requirements. The performance requirements are based on the three pillars of sustainability, aided by commuter surveys carried out in Stockholm ferries, interviews with public transport providers (PTP) and previous literature. The evaluation of the ferry is performed using analytic hierarchic process (AHP) to convert the PTP’s subjective preferences and ferry performance into a single dimensionless index. Rules for quantification of performance metrics including social performance are proposed. The uncertainties associated with AHP are addressed by employing fuzzy AHP based on extent analysis and fuzzy AHP in combination with particle swarm optimization. Two applications including performance assessment of existing ferries and assembly of a modular ferry are discussed. The method can lead to objective decision making in ferry evaluation, potentially leading to a more efficient WPT.

Runout and deflection of granular flow past an array of obstacles on a slope

The interaction between granular flow and an array of obstacles is an important research subject in geological disaster prevention. We used a numerical model for the depth-integrated equations formulated in a bed-fitted coordinate system to simulate the runout and deflection of granular flow past an array of simple obstacles. Numerical simulations of granular flow encountering arrays of square columns and tetrahedral pyramids gave a lot of interesting and fascinating deposits. We then proposed a new dimensionless index called deflection efficiency (DE), together with the runout efficiency (RE) to quantify the comprehensive effects of the obstacle system on the runout and deflection behavior. There are three physical effects, a dissipation effect through bow shock, a deflection effect by splitting the granular flow, and a retention effect via trapping some granular mass, the combinations of which determine the mobility and deposit of granular flow. We found that RE decreases as either the height or number of rows of obstacles increases because of the dissipation effect, while DE increases as height increases due to the deflection effect for both tetrahedral and square column obstacles. However, if the retention effect was as important as the deflection effect, the DE could be reduced when the row numbers increase further. These findings provide some constructive help for the design of obstacle arrays and complement the understanding of subsequent flow after interaction between granular flow and obstacle arrays.