Similarity Hypothesis Research Articles

A review on turbulent flow over rough surfaces: Fundamentals and theories

• Townsend hypothesis can explain large-scale motions near rough and smooth walls. • Is unable to describe all roughness regimes and does not scale d-type roughness. • Wall similarity hypothesis faces both supporting and conflicting evidence. • Roughness function can be scaled with height and effective slope of roughness. • Available models do not point to agreed conclusions or trends for all roughness types, Surface roughness can significantly influence the fluid dynamics and heat transfer in convective flows by inducing perturbations in the velocity profile which affect surface drag, turbulent mixing and heat transfer. While surface roughness can often negatively affect the performance of systems, it can also lead to performance improvements, such as in convective flows where roughness elements have been shown to enhance heat transfer. Turbulent flows over rough surfaces have been studied for about a century leading to significant developments in this field. Direct Numerical Simulation (DNS) has made significant contributions to the knowledge of turbulent flows over rough surfaces as well as evaluation of the developed theories. Moreover, the turbulent closures model has seen wide use for simulation of rough-wall turbulent flows in practical applications where DNS is hindered by its complexity and computational resources. Despite a significant number of experimental and CFD studies and the latest advances in this field, a recent review was not available. Therefore, this review surveys the past and recent experimental and numerical studies to address the fundamentals and theories related to the structure of turbulent flows over rough walls. This study chiefly investigates the structure of mean flow profile over rough surfaces, and its correlation with smooth wall mean flow profile. This review study can contribute to prospective experimental and CFD work, and for characterising rough-wall turbulent flows and heat transfer in different academic and engineering applications such as aerodynamics, hydraulics, meteorology, and manufacturing. The review concludes that despite significant progress, the structure of turbulent flow is still not fully understood. This is mainly due to a lack of systematic studies on the structure of turbulent flow and also due to the variety of roughness which influence the dynamics of the flow in the roughness sublayers. The current roughness scale (sand-grain roughness height) fails to completely characterise roughness in many cases. Therefore, there is a need for a universal roughness scale that can describe every type of roughness and be used in any rough-flow regimes, including fully rough and transitionally rough regimes.

Deformed contour segment matching for multi-source images

Robust and accurate multi-source matching is a difficult task due to significant nonlinear radiometric differences, background clutter, and geometric deformation in corresponding regions. Motivated by these existing problems, a discriminating yet robust combined descriptor for multi-source image matching, called deformed contour segment similarity (DCSS), is proposed in this work. First, the proposed DCSS, which is constructed by histogram of the combined contour features rather than the commonly used corner point and gradient, presents the accurate correspondence between image pairs and improves the descriptive ability to radiometric differences. Second, the deformed curve is presented via a finite-dimensional matrix Lie group to determine the similarity metric with an explicit geodesic solution. The geodesic distance, which indicates the nearest distance between curves in fluid space, is defined as the weight coefficient of the constructed histogram to enhance the robustness of the descriptor. The proposed algorithm utilizes the holistic contour information for the scoring and ranking of the shape similarity hypothesis, which can effectively reduce the influence of partially missing contours. Finally, a precise bilateral matching rule is used to perform the matching between the corresponding contour segments. Some experiments are carried out on various infrared-visible image data sets. The results demonstrate that the proposed DCSS achieves more robust and accurate matching performance than many popular multi-source image matching methods.

A solution to the dilemma `limiting similarity vs. limiting dissimilarity' by a method of transparent artificial intelligence

Ecological hypotheses of ‘limiting similarity’ and ‘limiting dissimilarity’ formulate the alleged conditions for implementing the competitive exclusion. The limiting similarity hypothesis assumes that exceeding a threshold of interspecific similarity leads to competitive exclusion. The hypothesis of limiting dissimilarity states the opposite - a condition of implementing competitive exclusion is exceeding of a threshold of interspecific dissimilarity. These hypotheses clearly contradict each other and we tested them on the model of competition at different values of relative competitiveness of the species. The model of competition under study we implemented as automatic deductive inference by a method of a completely transparent and completely explainable artificial intelligence. In order to strictly verify the hypotheses, we have excluded different possible factors promoting competitive coexistence. We have achieved that by ensuring that all conditions for the studied complete competitors were equal, with the exception of competitiveness of the species. Using our individual-based cellular automata model we demonstrate that two trophically identical species aggressively competing for a single limiting resource, all other things being equal, may coexist in one limited habitat until the threshold of differences in competitiveness exceeds 31%. The obtained results reject the hypothesis of limiting similarity and confirm the hypothesis about the limiting dissimilarity. The results are of importance for evolution theory and for finding pathways to ecological sustainability. Our individual-based modelling approach, based on the transparent and explainable artificial intelligence, opens up great prospects for a variety of theoretical and applied fields.

Turbulence cascade model for viscous vortex ring-tube reconnection

The reconnection of a vortex ring and a vortex tube in a viscous fluid with the effects of two vortex core sizes (σ0=0.12r0 and 0.24r0, where r0 are initial ring radius) and three initial flow configurations (left-offset, center, and right-offset) at Reynolds number (ReΓ) of 10 000 was investigated using a high-order vortex-in-cell method combined with a large-eddy simulation model. For the left-offset case, a large part of the ring, slipping over the tube, associates with a small part of the tube to establish a new vortex ring, whereas the rest of the tube is reconnected by another part of the ring. For the center case, half of the ring joins with a part of the tube to construct an elliptical vortex ring while the rest connects because of viscosity. The reconnected ring and tube become more stable and are like the initial ones in the ultimate stage. For the right-offset case, both the ring and tube's reconnection occurs, and the reconnected elliptical vortex ring is rapidly distorted. The proportion of reconnected ring increases, and then this ring section loses its integrity, decaying into a complex cluster of various-scales vortex structures in different shapes. At σ0=0.12r0, the secondary vortex structures surrounding the tube and ring appear in three cases, while they are only observed for the center case at σ0=0.24r0. For three flow configurations and two vortex core sizes, after the reconnection, the energy cascade of the flow approaches a k−5/3 slope of Kolmogorov's similarity hypotheses and a k−3 slope in the ranges of wavenumbers (k) from 3 to 10 and from 10 to 40, respectively. The highest population of small-scale coherent vortex structures is observed for the right-offset, followed by the center and left-offset. In addition, a larger number of these structures was observed for a smaller core size. This validates that the mixing performance is the best at a small vortex core and in the right-offset configuration.

Response to Invited Commentaries on “Consonance Preferences Within an Unconventional Tuning System”

Response to Invited Commentaries on “Consonance Preferences Within an Unconventional Tuning System”

Consonance Preferences Within an Unconventional Tuning System

Recently, Bowling, Purves, and Gill (2018a), found that individuals perceive chords with spectra resembling a harmonic series as more consonant. This is consistent with their vocal similarity hypothesis (VSH), the notion that the experience of consonance is based on an evolved preference for sounds that resemble human vocalizations. To rule out confounding between harmonicity and familiarity, we extended Bowling et al.’s (2018a) procedure to chords from the unconventional Bohlen-Pierce chromatic just (BPCJ) scale. We also assessed whether the association between harmonicity and consonance was moderated by timbre by presenting chords generated from either piano or clarinet samples. Results failed to straightforwardly replicate this association; however, evidence of a positive correlation between harmonicity and consonance did emerge across timbres following post hoc exclusion of chords containing intervals that were particularly similar to conventional equal-tempered dyads. Supplementary regression analyses using a more comprehensive measure of harmonicity confirmed its positive association with consonance ratings of BPCJ chords, yet also showed that spectral interference independently contributed to these ratings. In sum, our results are consistent with the VSH; however, they also suggest that a composite model, incorporating both harmonicity as well as spectral interference as predictors, would best account for variance in consonance judgments.

Satisfying and stable couple relationships: Attachment similarity across partners can partially buffer the negative effects of attachment insecurity.

Insecure attachment in couples is negatively associated with relationship functioning. Similarity of partner attachment on the other hand might attenuate such relationship outcomes. We tested the opposing insecurity and similarity hypotheses by examining associations of attachment with relationship satisfaction and instability in a representative community sample of couples (N = 1,014). We expected: (a) negative effects of insecure attachment (main effects of actor and partner avoidance and anxiety, and interaction effects consistent with fearful‐avoidance and demand‐withdraw patterns); and (b) positive effects of similarity in avoidance and anxiety. Actor‐Partner‐Interdependence Models showed clear support for the insecurity hypothesis. Main effects of avoidance and anxiety, explained 46.2% of the variance of satisfaction, and 17.9% of instability. We conclude that reducing insecurity of attachment, in particular avoidance, must be a central target in couple therapy. Interestingly, similarity of attachment can partially buffer the negative effects of attachment insecurity. Clinical implications are discussed.

Using Particle Image Velocimetry to Determine Turbulence Model Parameters

The primary parameter of a standard model, , was calculated from stereoscopic particle image velocimetry (PIV) data for a supersonic jet exhausting into a transonic crossflow. This required the determination of turbulent kinetic energy, turbulent eddy viscosity, and turbulent energy dissipation rate. Image interrogation was optimized, with different procedures used for mean strain rates and Reynolds stresses, to produce useful turbulent eddy viscosity fields. The eddy viscosity was calculated by a least-squares fit to all components of the three-dimensional strain-rate tensor that were available from the PIV data. This eliminated artifacts and noise observed when using a single strain component. Local dissipation rates were determined via Kolmogorov’s similarity hypotheses and the second-order structure function. The eddy viscosity and dissipation rates were then combined to determine . Considerable spatial variation was observed in , with the highest values found in regions where turbulent kinetic energy was relatively low but where turbulent mixing was important, e.g., along the high-strain jet edges and in the wake region. This suggests that use of a constant in modeling may lead to poor Reynolds stress predictions at mixing interfaces. A data-driven modeling approach that can predict this spatial variation of based on known state variables may lead to improved simulation results without the need for calibration.

Turbulent swirl flow analysis by Kolmogorov's similarity hypotheses

AbstractTurbulent swirl flow generated by the axial fans in pipe is investigated in this paper by using Kolmogorov's similarity hypotheses. It is shown that energy in the inertial subrange is divided among eddies after the “−5/3” law, i.e. Φww ∝ f−5/3, where Φww is spectral density for circumferential velocity and f is the frequency. This is presented for two various axial fans, of which one is carefully designed to generat Rankine vortex, while the second one has solid body circumferential velocity profile.

Competitive Approaches And Mergers and Acquisitions

Using textual analysis and the firm life-cycle theory to proxy for a company's competitive strategy, this paper empirically examines the strategic similarity hypothesis. The findings show that mergers and acquisitions deals are more likely between companies implementing the same strategy. Moreover, same strategy deals yield higher announcement returns, asset and sales growth. The effect is more pronounced in a highly competitive environment and within an industry, confirming that strategic misalignment acts as a constraint to the merged company's optimal response to investment opportunities and market threats. Overall, the results reveal that synergies obtained from the overlapping strategies constitute an important determinant of public mergers and acquisitions.

Contending Remaining Useful Life Algorithms

Operational readiness, reliability and safety are all enhanced through condition monitoring. That said, for many assets, there is still a need for a prognostic capability to calculate remaining useful life (RUL). RUL allows operation and maintenance personnel to better schedule assets, and logisticians to order long lead time part to help improve balance of plant/asset availability. While a number of RUL techniques have been reported, we have focused on fatigue crack growth models (as opposed to physics or deep learning of based models). This paper compares the performance of stress intensity models (linear elastic model, e.g. Paris’ Law), to Head’s theory (geomatical similarity hypothesis) and to Dislocation/Energy theories of crack growth. It will be shown that these models differ mainly in the crack growth exponent, and that this leads to large differences in the estimation of RUL during early state fault propagation, though the results of all three models converge as the RUL is shorted.

Calculation of a Half-life Period of a Scientific Journal in the Case of Incomplete Data in the Journal Citation Reports

The goal of this study was to investigate the dynamics of two journals indicators (Cited Half-life and Citing Half-life) in the case of incomplete or inaccuracy data in the Journal Citation Reports. A detailed analysis of these data for the CdHL and CgHL indicators for 1997–2018 was performed. The previously formulated similarity hypothesis on journal distribution by half-life period was clarified. Methods for determining the weighted average values of half-life indicators were developed in detail. The test of the similarity hypothesis had identified the time frame within which its objectivity was certain. Results of our study revealed that the dynamics of half-life indicators were positive; moreover, and these dynamics are much more pronounced for permanently retentive journals, i.e., journals that were present in the JCR during the entire 22-year study period.

Broadening Vision Around Values: An Integrative Two-Factor Theory of Workplace Value Congruence

Value congruence is an important determinant of human behavior in organizations. It influences positive states for workers (e.g., a sense of belonging, job satisfaction, and positive affect) and is beneficial for organizational work practices (e.g., commitment, citizenship behaviors, and tenure). Conversely, value incongruence leads to negative states (e.g., out-groups, organizational exit, and depressive symptoms). To date, values have been conceptualized context-free (e.g., human or personal values) or disaggregatedly in the work environment (e.g., work values, political values, leadership values, and cultural values) and value congruence has been viewed almost exclusively as a positive construct. Based on the underlying theories of variation theory, salient value similarity hypothesis, self-categorization theory, and signaling theory, and adopting the ‘similarity leads to attraction’ and ‘dissimilarity leads to repulsion’ hypotheses, we develop an integrative two-factor theory of value congruence. This model integrates work, political, cultural, and leadership values, and conceptualizes the impact of congruency and incongruency as two separate psychological processes. We conclude with a discussion of directions for future research.

Experimental verification of hydrodynamic similarity in hot flows

This paper examines a common hypothesis in the design of internal combustion engine exhaust lines, namely that the ratio of the total pressure drop across the line to the inlet dynamic head should be a function only of the Reynolds number. While incompressible flow theory, provided that some simplifications are considered, is often used in support of this hypothesis, detailed experimental verification in actual exhaust lines is absent from the literature. Production exhaust lines contain non-trivial flow complexities such as muffler devices and catalytic converters and, in the case of high-performance engines, often operate at high temperature and high mass flow conditions, thereby rendering the usual theoretical simplifications doubtful. In this work, a production exhaust line composed of cold and hot ends, featuring a muffler and a catalytic converter, is tested at a variety of conditions. Analysis of the results shows that compressibility corrections must be factored in at certain conditions routinely found in actual high-performance engines, and that for hot ends, laminar flow at the converter monolith channels may pose a challenge to the hydrodynamic similarity hypothesis.

STUDI KOMPARASI HASIL BELAJAR MATEMATIKA MENGGUNAKAN MODEL PEMBELAJARAN KOOPERATIF TIPE NUMBERED HEADS TOGETHER (NHT) DAN STUDENT TEAMS ACHIEVEMENT DIVISION (STAD)

Abstract 
 This study aims to find out which is better between mathematics learning outcomes in Cokroaminoto Batang Junior High School students who are taught using the Cooperative learning model Numbered Head Together (NHT) or those who are taught using the Cooperative learning model type Student Teams Achievement Division (STAD) in the material mathematics field rectangular. The sample of this study consisted of 2 classes, namely experimental class 1 and experimental class 2 using the NHT and STAD methods. This study used qualitative research methods. Data collection methods used are documentation and test methods. Research instruments in the form of learning tools and mathematics test results. Data analysis performed was a prerequisite test using the average similarity test and hypothesis testing by calculating the average. The results showed that the average learning outcomes of experimental class 1 students amounted to 76,875 and experimental class 2 amounted to 72,56667 which means that classroom learning outcomes taught by NHT type cooperative learning models were better than classroom learning outcomes taught by the STAD type cooperative learning models. From the results of the study, it can be concluded that the NHT type of cooperative learning model is more effective when compared to the STAD type cooperative learning model on the subject of quadrilateral in class VII students of Cokroaminoto Batang Middle School Academic Year 2018/2019
 Keywords: STAD type cooperative learning model, NHT type cooperative learning model, learning outcomes
 .

STUDI KOMPARASI HASIL BELAJAR MATEMATIKA MENGGUNAKAN MODEL PEMBELAJARAN KOOPERATIF TIPE NUMBERED HEADS TOGETHER (NHT) DAN STUDENT TEAMS ACHIEVEMENT DIVISION (STAD)

Abstract 
 This study aims to find out which is better between mathematics learning outcomes in Cokroaminoto Batang Junior High School students who are taught using the Cooperative learning model Numbered Head Together (NHT) or those who are taught using the Cooperative learning model type Student Teams Achievement Division (STAD) in the material mathematics field rectangular. The sample of this study consisted of 2 classes, namely experimental class 1 and experimental class 2 using the NHT and STAD methods. This study used qualitative research methods. Data collection methods used are documentation and test methods. Research instruments in the form of learning tools and mathematics test results. Data analysis performed was a prerequisite test using the average similarity test and hypothesis testing by calculating the average. The results showed that the average learning outcomes of experimental class 1 students amounted to 76,875 and experimental class 2 amounted to 72,56667 which means that classroom learning outcomes taught by NHT type cooperative learning models were better than classroom learning outcomes taught by the STAD type cooperative learning models. From the results of the study, it can be concluded that the NHT type of cooperative learning model is more effective when compared to the STAD type cooperative learning model on the subject of quadrilateral in class VII students of Cokroaminoto Batang Middle School Academic Year 2018/2019
 Keywords: STAD type cooperative learning model, NHT type cooperative learning model, learning outcomes
 .

A direct comparison of pulsatile and non-pulsatile rough-wall turbulent pipe flow

Pulsatile rough-wall turbulent pipe flow is compared against its non-pulsatile counterpart using data obtained from direct numerical simulation. Results are presented at a mean friction Reynolds number of 540 for a set of three geometrically scaled roughness topographies at a single forcing condition, which, based on existing classifications, falls into the current-dominated very-high-frequency regime. By comparing the pulsatile data against an equivalent non-pulsatile dataset (Chan et al. , J. Fluid Mech. , vol. 854, 2018, pp. 5–33), the key differences (and similarities) between the forced and unforced configurations are identified. A major finding of this study is that the flow in the outer region retains its self-similar functional form under pulsatile rough-wall conditions, and, as a result, Townsend’s outer-layer similarity hypothesis holds for the roughness-forcing combinations considered here. On the other hand, the unsteady cases exhibit a rich array of flow physics in the region beneath the roughness crests not observed in the steady case. These differences are examined using a Moody chart, which encapsulates how the hydraulic properties of pulsatile rough-wall pipe flow differ from their non-pulsatile counterpart.

Perceptions of pubertal timing relative to peers: Comparison targets and social contexts of comparison.

In studies measuring pubertal timing multiple ways, perceived timing relative to peers is more strongly associated with adverse outcomes in girls. However, girls' comparison targets (those to whom they compare) and the contexts in which comparison occurs is unclear. This study examined perceived relative pubertal timing to identify the comparison target (ethnicity-race) and the contexts (schools, neighborhoods) of these comparisons. We assessed perceived relative pubertal timing in a diverse sample of 511 late-adolescent girls aged 17-19 years (49% White) recruited from a range of U.S. universities. Girls more often made in-group comparisons. Latina, Asians, and Middle Easterners were more likely to use White comparisons than Blacks. Latinas also more often used Black comparisons, and Latina and Whites more often used Asian comparisons. Early developers (collapsed across ethnicity-race) more often used Latina and Black comparisons. There were no significant differences based on ethnicity-race or pubertal timing groups on the context of comparisons. The study findings support the similarity hypothesis tenet of social comparison theory, such that most girls compare their development with other girls within their own ethnic-racial group, and limited out-group comparisons occur. Moreover, comparison contexts often take place in classrooms/schools. Given research is scant regarding the mechanisms that link puberty and negative outcomes, this study offers new insights into potential social mechanisms for future research to explore. Greater attention might be placed on ethnic-racial identity exploration and critical media literacy to help pubertal girls explore the role of media in their identity development and body ideal. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Scaling of the turbulent energy dissipation correlation function

We examine the scaling of the two-point correlation function for , the energy dissipation rate, over a range of values of the separation between the two points and the Taylor microscale Reynolds number . The correlation function is estimated from hot-wire measurements in grid turbulence, along the axes of wakes and jets, and along the centreline of a fully developed channel flow. When exceeds a value of approximately 300, a condition which is achieved for both plane and circular jets, the correlation function collapses over nearly all values of when the normalization uses Kolmogorov scales. However, there is no collapse in either the power-law range or dissipative range when the normalization is on the integral (or external) length scale, which indicates that there is no self-similarity based on external scales. Although the maximum value of is not much larger than , the behaviour of the energy dissipation correlation function on the axes of plane and circular jets seems consistent with the first similarity hypothesis of Kolmogorov (Dokl. Akad. Nauk SSSR, vol. 30, 1941, pp. 299–303) but not with the revised phenomenology of Kolmogorov (J. Fluid Mech., vol. 13, 1962, pp. 82–85).

Do d/Deaf and Hard of Hearing Children Need Access to a Spoken Phonology to Learn to Read? A Narrative Meta-Analysis.

A meta-analysis was conducted to investigate phonology's role in d/Deaf and hard of hearing (d/Dhh) children's development of reading, and their ability to access spoken-language phonology. A systematic search of databases and journals identified 27 studies, 7 of which met the inclusion criteria. The included studies, experimental or quasi-experimental in nature, were conducted over a 20-year period (1995-2016) with students ages 3-18 years. Other literature was identified to enhance the discussion and support the interpretations. The review showed that spoken language's phonology is one of the literacy skills d/Dhh students must possess in order to learn to read. Further, the study found that d/Dhh students can access phonology using techniques like Visual Phonics and Cued Speech. These findings support the qualitative similarity hypothesis, which states that phonology is important for reading development and that d/Dhh children have the ability to access it.