Hasil untuk "Descriptive and experimental mechanics"

M. Keller

Marielle de Oliveira, Fábio Saltara, Adrian Jackson et al.

The flow around circular cylinders is a classic problem in fluid mechanics with significant implications for offshore engineering. While extensive numerical and experimental research has focused on the subcritical and critical Reynolds regimes, the supercritical and postcritical regimes remain challenging and relatively unexplored, primarily due to the complex nature of turbulence and the high computational requirements. In this study, we perform three-dimensional detached eddy simulations using the finite volume method in OpenFOAM v1906, employing Menter’s k-<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>ω</mi></semantics></math></inline-formula> SST turbulence model, to systematically investigate the flow past an infinitely long smooth cylinder from the subcritical through the postcritical regimes. The numerical setup ensures accurate near-wall resolution and reliable representation of unsteady flow features. We present a detailed analysis of vortex shedding patterns, wake evolution, and statistical properties of lift and drag coefficients for selected Reynolds numbers representative of each regime. The simulation results are benchmarked against experimental data from the literature, demonstrating good agreement for Strouhal number and mean drag. Special emphasis is placed on the evolution of wake topology and force coefficients as the flow transitions from laminar to fully turbulent conditions. The findings contribute to the limited numerical literature on flow around circular cylinders across subcritical, critical, supercritical, and postcritical Reynolds number regimes, providing insights that are fundamentally relevant to the broader scope of understanding vortex shedding phenomena.

Richard Healey

Applications of quantum mechanics have led to many successful predictions and explanations of puzzling phenomena, and we now apply quantum mechanics to gain, process, and communicate information in novel ways. We can understand quantum mechanics by understanding how we have applied it. We should not seek agreement on the nature of the world it represents, because this theory does not itself represent the physical world (though its applications do help us to represent it better). When applied to a quantum state, quantum mechanics yields probabiities for physical events: both state and probability are objective--not because they represent elements of phyiscal reality, but because each exerts norrmative authority over the beliefs of anyone who accepts quantum mechanics and applies it relative to a physical situation they may (but need not) occupy. These events may be described by statements that are meaningful in an appropriate environmental context, and quantum mechanics can help one to say when that is. Measurement creates an appropriate context, so here the Born rule indirectly yields probabilities of measurement outcomes. The quantum state of a system does not "collapse" on measurement: a new state must be assigned relative to a physical situation in which information about the outcome is accessible. Understood this way, there is no measurement problem, and violations of Bell inequalities does not demonstrate "spooky" non-local action. Quantum field theories have no physical ontology of their own: a quantum field is a mathematical object in a model whose application helps us to improve and extend our descriptions of the world in other terms. We cannot realise the scenario of Wigner's friend and its recent extensions: but the data that provide overwhelming evidence for quantum mechanics are objective in the same sense as the relative measurement outcomes described in those scenarios.

Yuriy Romasevych, Oleksandr Zarivnyi

Для підтвердження застосовності теоретичного методу синтезу оптимального керування рухом пристрою для транспортування малогабаритних вантажів постає питання проведення експериментального дослідження такого керування на практиці. В даній роботі описано методику проведення експериментального дослідження процесу стабілізації положення пристрою для транспортування малогабаритних вантажів та методи оцінки якості такої стабілізації. Очікуваним результатом було отримати експериментальні дані перевірки якості розробленого керування для 11 наборів коефіцієнтів ПІД-регулятора. Надалі з них обрано коефіцієнти регулятора, які найкраще себе показали в процесі стабілізації положення пристрою. Також отримано експериментальні дані роботи пристрою з мінімальною похибкою при порівнянні з теоретичними даними. При проведенні експериментального дослідження використано фізичну модель двоколісного пристрою для транспортування малогабаритних вантажів. Було перевірено якість реалізації регулювання положення пристрою на одинадцяти наборах коефіцієнтів ПІД-регулятора. Зібрано масиви експериментальних даних роботи пристрою, проведено порівняння з теоретичними даними та проведено оцінку якості процесу стабілізації положення пристрою. При співставленні теоретичних і експериментальних даних отримано показники максимальних та середньоквадратичних похибок кута нахилу пристрою, показники похибок максимальної та середньоквадратичної кутової швидкості нахилу пристрою. Декремент згасання коливань знаходився в межах 0,25…2,11. Серед усіх розв’язків обрано найкращим з практичної точки зору є результат набору наступних коефіцієнтів ПІД-регулятора: пропрорційний k1=-2,112, інтегральний k2=-1,756, диференціальний k3=-1,38·10-7. Цей результат відповідає найбільшому декременту згасання коливань (λ=2,11). Отриманий результат дав підстави вважати методику синтезу оптимального керування дієвою, а задачу експериментальної перевірки виконаною.

Zihan Sun, Jianguo Lin, Dong Wang et al.

Wall-thickness deformation is a critical indicator of fatigue risk in flexible risers exposed to vortex-induced vibration (VIV), especially under combined internal and external flow conditions. This study examines the spanwise evolution and distribution of wall-thickness deformation in a riser traversing air and water. The effects of external flow velocity, internal flow velocity, and internal fluid density on in-line (IL) and cross-flow (CF) wall deformation are systematically analyzed at characteristic positions. The results show that wall deformation exhibits strong spatial variability and media property dependence: IL deformation in the air-exposed segment is amplified under lock-in conditions due to lower damping, while the submerged segment experiences consistently larger deformation driven by added-mass effects. Internal flow influences wall-thickness response in a non-monotonic manner, and increased internal fluid density suppresses deformation while shifting the dominant frequency. These findings demonstrate that wall-thickness deformation is a sensitive and integrative response to fluid–structure interaction, offering a direct basis for identifying high-risk zones and improving fatigue-resistant design in deep-sea riser systems.

Nuno M. C. Martins, Dídia I. C. Covas, Bruno Brunone et al.

Partial blockages in pressurised pipe systems present significant challenges for precise detection, characterisation, and ongoing monitoring. Transient test-based techniques, which utilise sharp but small pressure waves, have shown considerable potential due to their safety and diagnostic capabilities. This paper investigates the transient response of an extended partial blockage—an evolution of a discrete partial blockage that protrudes longitudinally—an increasingly complex condition which has a greater impact on the behavior of pipe systems. Through Computational Fluid Dynamics simulations, the interaction of pressure waves with extended partial blockages of different severity and lengths is examined to assess the resulting pressure response. The results confirm that the pressure signature, generated by extended partial blockages, differs markedly from those of discrete partial blockages. In particular, the magnitudes of the first and second pressure peaks enable accurate characterisation of the severity and extent of the extended partial blockage. These results demonstrate that transient test-based techniques can play a significant role in managing water pipe systems, facilitating more targeted maintenance interventions. Broader implementation of these techniques could enable water utilities to reduce energy consumption, maintain water quality with lower chlorine dosing, and prevent the progression of partial blockages to total pipeline blockage.

Hassan Alfaifi, Hossein Bonakdari

A new approach to predicting the geometrical characteristics of the mixing behavior of an inclined dense jet for angles ranging from 15° to 85° is proposed in this study. This approach is called the group method of data handling (GMDH) and is based on the artificial neural network (ANN) technique. The proposed model was trained and tested using existing experimental data reported in the literature. The model was then evaluated using statistical indices, as well as being compared with analytical models from previous studies. The results of the coefficient of determination (<i>R</i>²) indicate the high accuracy of the proposed model, with values of 0.9719 and 0.9513 for training and testing for the dimensionless distance from the nozzle to the return point <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>x</mi><mi>r</mi></msub><mo>/</mo><mi>D</mi></mrow></semantics></math></inline-formula> and 0.9454 and 0.9565 for training and testing for the dimensionless terminal rise height <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>y</mi><mi>t</mi></msub><mo>/</mo><mi>D</mi></mrow></semantics></math></inline-formula>. Moreover, four previous analytical models were used to evaluate the GMDH model. The results showed the superiority of the proposed model in predicting the geometrical characteristics of the inclined dense jet for all tested angles. Finally, the standard error of the estimate (SEE) was applied to demonstrate which model performed the best in terms of approaching the actual data. The results illustrate that all fitting lines of the GMDH model performed very well for all geometrical parameter predictions and it was the best model, with an approximately 10% error, which was the lowest error value among the models. Therefore, this study confirms that the GMDH model can be used to predict the geometrical properties of the inclined negatively buoyant jet with high performance and accuracy.

Lee A. Rozema, Teodor Strömberg, Huan Cao et al.

In the past decade, the toolkit of quantum information has been expanded to include processes in which the basic operations do not have definite causal relations. Originally considered in the context of the unification of quantum mechanics and general relativity, these causally indefinite processes have been shown to offer advantages in a wide variety of quantum information processing tasks, ranging from quantum computation to quantum metrology. Here we overview these advantages and the experimental efforts to realise them. We survey both the different experimental techniques employed, as well as theoretical methods developed in support of the experiments, before discussing the interpretations of current experimental results and giving an outlook on the future of the field.

Premika S. Thasu, Gaurav Kumar, Subrahmanyam Duvvuri

Recent experimental studies reveal that the near-wake region of a circular cylinder at hypersonic Mach numbers exhibits self-sustained flow oscillations. The oscillation frequency was found to have a universal behavior. Experimental observations suggest an aeroacoustic feedback loop to be the driving mechanism of oscillations. An analytical aeroacoustic model which predicts the experimentally observed frequencies and explains the universal behavior is presented here. The model provides physical insights and informs of flow regimes where deviations from universal behavior are to be expected.

Marcin Maździarz

The paper gathers and unifies mechanical stability conditions for all symmetry classes of 3D and 2D materials under arbitrary load. The methodology is based on the spectral decomposition of the fourth-order stiffness tensors mapped to second-order tensors using orthonormal (Mandel) notation, and the verification of the positivity of the so-called Kelvin moduli. An explicit set of stability conditions for 3D and 2D crystals of higher symmetry is also included, as well as a Mathematica notebook that allows mechanical stability analysis for crystals, stress-free and stressed, of arbitrary symmetry under arbitrary loads.

Elke Schubert-Hjalmarsson, A. Fasth, K. Ickmans et al.

Background Pain is a major symptom in adolescents with hypermobility spectrum disorder or hypermobile Ehlers-Danlos syndrome. Although the underlying mechanism causing generalized pain in children with hypermobility spectrum disorder or hypermobile Ehlers-Danlos syndrome is unclear, central sensitization has been suggested as a possible explanation. The aim of this study was to explore the feasibility of a study protocol for a future case–control study, investigating features of central sensitization in adolescents with hypermobility spectrum disorder or hypermobile Ehlers-Danlos syndrome. Methods Central sensitization features were measured in ten patients and nine healthy controls aged 13–17 years via experimental pain measurement quantifying primary and secondary hyperalgesia, endogenous pain modulation, and exercise-induced hyperalgesia. Descriptive statistics were used. Frequency, median, and range values were calculated. Results Eleven out of 57 patients chose to participate. No control could be recruited through public schools. Therefore, a convenience sampling strategy was used for the recruitment of the control group. The process of assessing primary and secondary hyperalgesia, endogenous pain modulation, and exercise-induced hyperalgesia was well tolerated by all participants (patients and controls). When assessing endogenous pain modulation via conditioned pain modulation, two participants in the patient group and three in the control group did not achieve a pain experience ≥ 3 on the numerical rating scale when immersing their hands in cold water. Conclusion This study investigated the feasibility, safety, and toleration of experimental pain measurements in adolescents with hypermobility spectrum disorder or hypermobile Ehlers-Danlos syndrome. Although the test protocol proved to be sufficiently feasible for use with the participant group, it will need to be adapted in the main study in order to obtain more reliable data. Recruitment, especially of participants for the control group, can be a major obstacle for future studies and requires careful planning. Trial registration Researchweb.org, 270,501. Registered on 9 May 2019.

S. Nukeshev, D. Eskhozhin, I. Mamyrbayeva et al.

Abstract A universal conical spreader for uniform distribution of granular fertilizers and seeds of grain crops, grasses is proposed. The developed universal conical spreader is designed for subsurface application of above-mentioned granular materials using seed drills and can be used as a passive distributor in a wide variety of applications. The methods of theoretical mechanics and descriptive geometry, particularly the method of replacement of projection plane have been applied to arrive at the design of the cone – the shape of conical spreader. A parametric equation was derived for the truncated part of the cone, which is an ellipse. The unique design of the cone-shaped distributor has a truncating form in the direction transverse to the movement of the seeder. In order to determine the interval of variability of spreader parameters more precisely, an analysis was carried out using a Mathcad-15 software. The results of theoretical research were confirmed in the laboratory and field conditions. The width of seed distribution, uniformity, and stability of distribution were studied to arrive at the most effective cone distributor design. The smallest values of non-uniformity and instability of material distribution of experimental coulter are reached at the values of factors D = 117–119 mm, h = 17–18 mm, and H = 32–35 mm.

Sriati Usman, Budi Budi, A. Kamaruddin et al.

ABSTRACTThis research analyzes the implementation of the "bits and pieces" game on students' learning outcomes in writing English descriptive texts. A quasi-experimental design with Junior High School students as the population and a cluster random sampling technique used to draw the sample. Furthermore, two groups were administered pre- and post-test to collect the data. According to the data analysis, a noteworthy disparity existed in the post-test outcomes between the two groups. The experimental group had an average score of 86.60, whereas the control group had 62.43 score. By setting a significance level of 0.05 and degree of freedom (df) of 40 (21+21-2), the t-test demonstrated that the calculated t-value (6.487) surpassed the critical value (1.684), thereby indicating the acceptance of the research hypothesis. This implied that bits and pieces games have an effect on enhancing students’ learning outcomes. Therefore, the game can be a great contribution for English teachers in teaching English descriptive text, in terms of improving content, mechanics, organization, sentence structure, and grammar. ABSTRAKPenelitian ini menganalisis implementasi permainan bits dan pieces terhadap hasil belajar siswa dalam menulis teks deskriptif dalam bahasa Inggris. Desain penelitian yang digunakan adalah eksperimen semu. Populasinya siswa SMP dan teknik pengambilan sampel melalui cluster random sampling. Data diambil dari hasil pre- dan post-test pada kelompok kontrol dan eksperimen yang menunjukkan terdapat pengaruh atau peningkatan pada kelompok kontrol dan eksperimen. Nilai rata-rata dari post-test pada kelompok eksperimen sebesar 86.60 dan kelompok kontrol sebesar 62.43 dengan menerapkan tingkat signifikansi 0.05 dan derajat kebebasan (df) 40 (21+21-2), hal ini menunjukkan nilai t-hitung (6.487) lebih besar dari nilai t- tabel (1.684) yang bermakna bahwa hipotesa penelitian ini diterima. Dengan demikian permainan bits dan pieces berpengaruh terhadap peningkatan hasil belajar siswa dalam menulis teks deskriptif. Oleh karena itu, hasil penelitian ini sangat berkontribusi kepada guru Bahasa Inggris yang mengajarkan keterampilan menulis teks deskriptif Bahasa Inggris yang berkaitan dengan peningkatan isi, penggunaan tanda baca, huruf besar dan kecil, pengorganizatian teks deskriptif, dan aturan kata dalam kalimat.How to Cite: Hairul, M.A., Nurhayati. (2023). Exploring Teacher Educators’ Understanding of Critical Pedagogy and its Implementation in the English Reading Class. IJEE (Indonesian Journal of English Education), 10(1), 207-220. doi:10.15408/ijee.v10i1.32312

Aizel Joy Salvador, Dr. Edilberto Z. Andal

One of the most effective means of empowering someone with knowledge and skills that bring about change and support their economic development is education. According to an article written by Leverage (2021), education helps to create a better society. Understanding the value of education in today’s culture is crucial. Learning or acquiring knowledge, skills, values, morals, beliefs, and habits is the education process. With the correct teaching strategies, teachers can make the classroom fun and effective for students to gain vital intellectual and social skills that will serve them for the rest of their lives (Indeed, 2023). Among such teaching methods is the use of experiential learning, wherein the students use experiences to learn a certain topic or subject (Institute for Experiential Learning, 2021). Hence, this study aims to determine the effectiveness of using an experiential learning strategy in teaching hip-hop to enhance dance performance among Grade 10 students. A descriptive-experimental research design method was employed wherein a pre and post-test was given among the respondents and their perception of the experiential learning strategy was assessed. Considering this, the results revealed a significant difference in the performance of the respondents before and after employing the experiential learning strategy in terms of knowledge, comprehension, ability, and attitude. It was also found that there is no significant relationship between the respondents' perception of the respondents in connection with the experiential learning strategy when compared to their performance.

Marlene Crone, Michael Türk

Supercritical fluid reactive deposition is an environmentally friendly technique for the synthesis of supported mono- or bimetallic nanoparticles. Experimental results show that the adsorption of a precursor on a substrate is the crucial process step that controls the loading and the size of the deposited metal nanoparticles. In this review, an overview of experimental and modeling work is given and selected experimental data were correlated with the following adsorption isotherm models: Henry, Freundlich, Langmuir, Toth, and Langmuir–Freundlich equations. As a result, in the case of precursors with a low CO₂ solubility and therewith low uptake, the adsorption behavior can be described with sufficient accuracy by the Henry approach. Furthermore, the Freundlich and Langmuir equations enable sufficiently accurate descriptions of the experimental data. In the end, strategies for overcoming the knowledge gaps for essential future research directions are suggested.

Oleg Sazhin

The size of micro- and nanofluidic devices accounts for their operation in modes that differ significantly from those for the corresponding macroscopic counterparts. Deep understanding of gas-dynamic processes occurring in micro- and nanofluidic systems opens new opportunities for the practical use of molecular transport at the micro- and nanoscale. Models and simulation methods with high reliability are described. The article also outlines the important flow parameters which must be considered in the first place to correctly simulate gas-dynamic processes in micro- and nanofluidic systems. The review will be useful as a reference for researchers interested in implementing preliminary analysis in the development and optimization of micro- and nanofluid devices.

Garrett Blum, Ryan Doris, Diego Klabjan et al.

Stress-strain curves, or more generally, stress functions, are an extremely important characterization of a material's mechanical properties. However, stress functions are often difficult to derive and are narrowly tailored to a specific material. Further, large deformations, high strain-rates, temperature sensitivity, and effect of material parameters compound modeling challenges. We propose a generalized deep neural network approach to model stress as a state function with quantile regression to capture uncertainty. We extend these models to uniaxial impact mechanics using stochastic differential equations to demonstrate a use case and provide a framework for implementing this uncertainty-aware stress function. We provide experiments benchmarking our approach against leading constitutive, machine learning, and transfer learning approaches to stress and impact mechanics modeling on publicly available and newly presented data sets. We also provide a framework to optimize material parameters given multiple competing impact scenarios.

Anton Žnidarčič, Tomaž Katrašnik

Increasing power densities of electric machines in e-vehicles in addition to the resulting quest for enhanced cooling concepts are bringing forward the importance of defining adequate heat transfer correlations in air gaps. This is a highly challenging topic, as there exist no generally applicable flow and heat transfer phenomena descriptions for air gaps due to their highly variable geometrical properties and operating conditions. As an answer to this challenge, this paper presents a workflow that defines an adequate 3D CFD model for an arbitrary air-gap design that includes its system-dependent boundary conditions. The workflow is built on the recognition of underlying air-gap flow phenomena, which are used to steer the subsequent design of the 3D CFD model in a systematic step-by-step manner. Consequently, the complexity of the 3D CFD model gradually increases to the point where it provides an adequate flow and heat transfer description. Validation of the workflow is presented for a wide range of air-gap designs and flow conditions. It is demonstrated that the 3D CFD models obtained with the workflow match the experimentally obtained data from various flow cases that have been documented in the literature. Considerable optimization of computational costs, offering potentially an order-of-magnitude reduction in computational time, is achieved as a result of computational domain span optimization and transient simulations being applied only when required. The validation confirms that this workflow facilitates construction of valid 3D CFD models without the prior knowledge of flow and heat transfer phenomena in a specific air gap. This workflow thus provides a reliable and computationally efficient tool for valorization of convective heat transfer, and opens up prospects for time- and cost-efficient optimizations of electric machines’ cooling system designs.

Fernando M. López-Aguilar, Fernando I. López-Bara

The low energy excitation states in frustrated magnetic structures can generate quasiparticles that behave as if they were magnetic charges. These excited states produce, in the so-called spin-ice materials, two different peaks of specific heat at temperatures less than 1.5 K. In this paper, we consider that the first structure is caused by the formation of fluid of magnetic dipoles configured by the dumbbell model with a boson nature in consonance with that described by Witten for mesons. The second structure, wider than the first one, corresponds to a plasma state that comes from the breaking of a great number of dipoles, which provokes the appearance of free magnetic charges, which constitute a cool magnetic plasma fluid. In this paper, we determine thermodynamic analytical functions: the thermo-potential and internal energy and their respective derivative physical magnitudes: entropy, and magnetic specific heat. We obtain results in a good concordance with the experimental data, which allow us to explain the phase transitions occurred in these spin-ice materials at very low temperatures.

Leandro Marques, Gustavo R. Anjos

The present work aims at developing a numerical study on the drug diffusion in the bloodstream in a coronary artery with drug-eluting stent implanted. The blood was modeled as a single-phase, incompressible and Newtonian fluid and the Navier–Stokes equation was approximated according to the Finite Element Method (FEM). The dynamics of drug-eluting concentration in bloodstream was investigated using four drug-eluting stents with different mass diffusivities in microchannels with variable cross sections, including a real coronary artery geometry with atherosclerosis. The results reveal complex drug concentration patterns and accumulation in the vicinity of the fat buildup.