Hasil untuk "Descriptive and experimental mechanics"

Matthew R. McConnell, Jason Knight, James M. Buick

Curved surfaces are a feature of many engineering applications, and as such, the accurate prediction of separation and reattachment from a curved surface is of great engineering importance. In this study, improved delayed detached eddy simulation (IDDES) is used, in conjunction with synthetic turbulence injection using the synthetic eddy method (SEM), to investigate the boundary layer separation from a curved backward-facing step for which large eddy simulation (LES) results are available. The commercial code Star CCM+ was used with the k-ω shear stress transport (SST) variation of the IDDES model to assess the accuracy of the code for this class of problem. The IDDES model predicted the separation length within 10.4% of the LES value for the finest mesh and 25.5% for the coarsest mesh, compared to 36.2% for the RANS simulation. Good agreement between the IDDES and LES was also found in terms of the distribution of skin friction, velocity, and Reynolds stress, demonstrating an acceptable level of accuracy, as has the prediction of the separation and reattachment location. The model has, however, found it difficult to capture the pressure coefficient accurately in the region of separation and reattachment. Overall, the IDDES model has performed well against a type of geometry that is typically a challenge to the hybrid RANS-LES method (HRLM).

Esteban Aedo-Muñoz, Pablo Merino Muñoz, Luciano Bernardes Leite et al.

<b>Background/Aims:</b> Asymmetry of the internal (IR) and external (ER) shoulder rotators can increase the risk of injuries in judokas. Discrete analyses are usually performed in time series data, but they can have biases by removing trends, so other approaches have been proposed to avoid these biases such as statistical parametric mapping (SPM) and principal component analysis (PCA). This study analyzed the asymmetry in the shoulder rotators in female judokas, comparing dominant (D) vs. non-dominant (ND) upper limbs. <b>Methods:</b> For this, 11 elite athletes (age: 20.1 ± 2.9 yrs.; experience: 4.0 ± 0.5 yrs.; body mass: 66.0 ± 14.6 kg; height: 1.6 ± 0.1 m; BMI: 24.8 ± 4.3 kg/m²), were evaluated in an isokinetic dynamometer (Cybex^® Humac/Norm Dynamometer CSMI, 502140, Stoughton, MA, USA). All participants performed the concentric (CON/CON) isokinetic evaluations of internal and external rotation of the shoulder in 60°/s and 180°/s angular velocities. <b>Results</b>: There was no significative asymmetry between IR vs. ER at 60°/s; similar results were observed at 180°/s when analyzed by PCA or SPM methods (<i>p</i> > 0.05 for all comparison). There was no difference between peak torque at 60°/s or 180°/s (<i>p</i> > 0.05 for all comparison). <b>Conclusions:</b> no asymmetry was observed in IR and ER in elite female athletes, regardless of the analysis method.

Ahad M. Rauf, Sean Follmer

Electroadhesive clutches are electrically controllable switchable adhesives commonly used in soft robots and haptic user interfaces. They can form strong bonds to a wide variety of surfaces at low power consumption. However, electroadhesive clutches in the literature engage to and release from substrates several orders of magnitude slower than a traditional electrostatic model would predict. Large release times, in particular, can limit electroadhesion's usefulness in high-bandwidth applications. We develop a novel electromechanical model for electroadhesion, factoring in polarization dynamics, the drive circuitry's rise and fall times, and contact mechanics between the dielectric and substrate. We show in simulation and experimentally how different design parameters affect the engagement and release times of centimeter-scale electroadhesive clutches to metallic substrates, and we find that the model accurately captures the magnitude and trends of our experimental results. In particular, we find that higher drive frequencies, narrower substrate aspect ratios, and faster drive circuitry output stages enable significantly faster release times. The fastest clutches have engagement times less than 15 us and release times less than 875 us, which are 10x and 17.1x faster, respectively, than the best times found in prior literature on centimeter-scale electroadhesive clutches.

J. Sanchidrián, F. Ouchterlony

The size-energy fan concept formulation is developed into a prediction model of the fragment size distribution from blast design and rock mass variables. The fragment size is scaled with a characteristic size of the blast and the rock mass discontinuity spacing and orientation. The energy is scaled with the rock strength and the cooperation degree between adjacent holes. A cooperation function is introduced that modifies the energy with the in-row delay, non-dimensionalized with the P-wave velocity and the holes spacing. The cooperation increases as the delay increases up to a certain value, beyond which the cooperation decreases and the fragmentation is coarser. Several prediction models are presented, using the Swebrec-based fan slopes function of the percent passing as starting point, with subsequent improvements involving alternative formulations of that function, that encompass a non-Swebrec underlying distribution of the fragment size. The models include 12 to 14 parameters, controlling the effect on fragmentation of the variables describing the rock mass, the explosive and initiation sequence, and the blast geometry. The parameters are determined from fits to the data base that was used for the xP-frag model, expanded with seventeen additional blasts. All fragmentation data used are mass size distributions determined by sieving and weighing of blasted muckpiles. The different models are introduced sequentially and discussed. The models presented improve the performance of xP-frag, while including a much smaller number of parameters and, unlike xP-frag, keeping the physically sound size-energy fan pattern, effectively extending its nature from a descriptive frame of the fragmentation-energy relations, to a predictive tool. A new fragmentation prediction model is developed from experimental, sieved data employing the fragment size – energy fan concept. The rock mass discontinuities and strength properties are incorporated to the model as modifiers of the fan focal coordinates. The cooperation between delayed holes is incorporated to the model as a modifier of the specific energy, a function of the delay. A 4-parameter distribution derived from the Swebrec function is introduced, that provides an excellent description of fragment size distributions. The accuracy of the predictions from the new model improves the existing state-of-the-art models of fragmentation from blasting. A new fragmentation prediction model is developed from experimental, sieved data employing the fragment size – energy fan concept. The rock mass discontinuities and strength properties are incorporated to the model as modifiers of the fan focal coordinates. The cooperation between delayed holes is incorporated to the model as a modifier of the specific energy, a function of the delay. A 4-parameter distribution derived from the Swebrec function is introduced, that provides an excellent description of fragment size distributions. The accuracy of the predictions from the new model improves the existing state-of-the-art models of fragmentation from blasting.

Annisa Syauqina Kadar, Muthia Mutmainnah Darmuh, Winda Ayu Utami R

English language proficiency is crucial in the global context as it serves as a medium to share ideas and information across nations. Recognizing the significance of English as an international language, the government of Indonesia has mandated English education from elementary school to university. Writing is one of the essential language skills that students must master, allowing them to express their feelings, opinions, and thoughts effectively. However, the study finds that many students lack interest and face challenges when it comes to writing. They struggle to generate ideas, choose appropriate topics, and organize their thoughts into coherent sentences. To address this issue, the researcher explores the implementation of the Extended Writing Project (EWP) method as a potential solution to improve students' writing proficiency. The research employs a pre-experimental method with a one-group pretest-posttest design to assess the effectiveness of the EWP method. The study is conducted at SMA Negeri 1 Polewali during the 2016/2017 academic year, with 24 students from one of the tenth-grade classes chosen as the sample through cluster random sampling. Throughout the research, the researcher guides students in proposing their own topics or selecting from a provided list, creating preliminary outlines, and clustering or listing ideas before organizing them into paragraphs. The EWP method emphasizes revision and editing, encouraging students to make multiple drafts and take responsibility for improving linguistic correctness. The results demonstrate a significant improvement in students' writing ability after the application of the EWP method. Notably, improvements are observed in content, organization, vocabulary, language use, and mechanics. Students show enhanced coherence, relevance, and use of appropriate words, leading to better-organized paragraphs and improved language correctness. In conclusion, the Extended Writing Project method proves to be effective in enhancing students' writing skills in descriptive texts at SMA Negeri 1 Polewali. The method encourages students to take ownership of their writing process, resulting in significant progress in their writing abilities. To overcome challenges related to limited vocabulary, the use of dictionaries with active vocabulary-building activities is suggested. This research contributes valuable insights to the field of English language teaching and offers a potential solution to enhance students' writing proficiency in Indonesian schools.

Nguyen Tien Khiem, Tran Thanh Hai, Le Khanh Toan et al.

The frequency response function (FRF) is a fruitful attribute that includes almost all dynamical characteristics of a structure such as natural frequencies and modes, damping coefficients, or resonance and antiresonance conceptions. However, the complex feature of FRF has not been thoroughly employed for structural damage detection. In the present study, a novel indicator extracted from FRFs of beam structures is developed for crack identification. The damage indicator originated from the well-known mode assurance criterion (MAC) and therefore it is termed spectral assurance criterion (SAC). First, a coherence coefficient calculated from FRFs of intact and damaged beams and called herein spectral damage index (SDI) is analyzed for examining sensitivity of FRFs to crack. Then, SAC calculated for different FRFs of the same damaged structure is employed for crack detection by the so-called contour method. Results obtained in numerical examples of the crack detection problem show that SAC is really a novel and efficient criterion for crack identification in beams from measured FRFs.

Rahul Arun, Tim Colonius

We simulate the head-on collision between vortex rings with circulation Reynolds numbers of 4000 using an adaptive, multiresolution solver based on the lattice Green's function. The simulation fidelity is established with integral metrics representing symmetries and discretization errors. Using the velocity gradient tensor and structural features of local streamlines, we characterize the evolution of the flow with a particular focus on its transition and turbulent decay. Transition is excited by the development of the elliptic instability, which grows during the mutual interaction of the rings as they expand radially at the collision plane. The development of antiparallel secondary vortex filaments along the circumference mediates the proliferation of small-scale turbulence. During turbulent decay, the partitioning of the velocity gradients approaches an equilibrium that is dominated by shearing and agrees well with previous results for forced isotropic turbulence. We also introduce new phase spaces for the velocity gradients that reflect the interplay between shearing and rigid rotation and highlight geometric features of local streamlines. In conjunction with our other analyses, these phase spaces suggest that, while the elliptic instability is the predominant mechanism driving the initial transition, its interplay with other mechanisms, e.g. the Crow instability, becomes more important during turbulent decay. Our analysis also suggests that the geometry-based phase space may be promising for identifying the effects of the elliptic instability and other mechanisms using the structure of local streamlines. Moving forward, characterizing the organization of these mechanisms within vortices and universal features of velocity gradients may aid in modelling turbulent flows.

Dai Yang, Meng-Yao Lu, Chi-Wen Chen et al.

Background Preschool-aged children with acute lymphoblastic leukemia (ALL) receive long-term treatment according to the Taiwan Pediatric Oncology Group (TPOG)–ALL 2013 protocol. Severe anxiety and noncompliance ahead of frequent invasive therapies leads to an increase in health care costs. Previous studies have shown that therapeutic video games (TVGs) can decrease the anxiety experienced by children who are ill. To our knowledge, no existing TVG has been designed specifically for preschool-aged children with ALL in Taiwan. Objective The purpose of this study was to develop a TVG using the popular Mechanics, Dynamics, and Aesthetics (MDA) framework for game design and to investigate the effect of this TVG on the reduction of therapy-related anxiety among preschool-aged children with ALL. Methods This study used a mixed methods approach over three phases: (1) develop a TVG using the MDA framework, (2) test the reliability of the TVG among three certified children’s art therapists, and (3) evaluate the reduction of therapy-related anxiety among participants after using the TVG for 6 weeks, using a two-group, stratified randomized controlled trial at a medical center in northern Taiwan. Eligible preschool-aged children with ALL were randomly assigned 1:1 into an experimental group or a control group. The two groups of subjects received the same usual care, and only the experimental group had access to and used the TVG. The children’s anxiety responses were reported by their family caregivers using the face rating scale (FRS). Descriptive analyses, the Fisher exact test, the Pearson chi-square test, and the Mann-Whitney U test were used to statistically analyze the variables. Results Six mechanics rules supported the dynamics of the TVG using four main features—character, nursery, tasks, and market—in order to complete all of the therapy-related anxiety reduction scenarios and to achieve eight aesthetics goals. The results of reliability test showed that participants found the TVG to be useful and trustworthy for preschool-aged children with ALL (Cronbach α=.98). A total of 15 participants were enrolled and randomly allocated to the experimental group (n=7) or the control group (n=8). The average number of TVG log-ins was 37.9 (SD 15.30, range 14-62) in the experimental group. The demographic data showed homogeneity across the two groups regarding age (3 to 5 years), sex (male), risk classification (standard risk), and treatment status (continuation therapy). The mean FRS score was 6.16 (SD 3.31) for the experimental group as compared to 7.45 (SD 2.71) for the control group (P=.04), which represented a significant difference between the groups at the 6-week follow-up. Conclusions This research provides evidence that using a TVG can decrease anxiety in preschool-aged children with ALL in Taiwan. The TVG could be used to support clinical professionals before they perform invasive therapies. However, it is recommended to increase the statistical power for inference. Trial Registration ClinicalTrials.gov NCT04199637; https://www.clinicaltrials.gov/ct2/show/NCT04199637

Abdulaziz Sanosi

The importance of Corrective Feedback (CF) to language learners has been a controversial topic for a long time. While some studies recognised CF's importance for accurate language use, others considered it deterrent to the meaningful acquisition of a second language. Recently, modern types of corrective feedback that utilise the vast advance in IT and Artificial Intelligence (AI) have emerged. This advancement has opened new investigation areas. Up to now, researchers have acknowledged the role of Automated Written Evaluation (AWE) in enhancing students’ writing and motivating them. Other studies have focused on students’ and teachers’ perceptions of such tools. However, the particular variance between this type of CF and the traditional one is still an area to explore. Accordingly, the present study aimed to compare CF provided by teachers to that offered by a well-known writing assistant Grammarly. The descriptive design was used to analyse the CF instances provided by five college professors to the Grammarly suggestions on a corpus of 115 texts, 23700 words, written by college students. The descriptive statistics method was adopted to summarise the findings. The study's main results indicated no significant difference in the number of errors detected by the two techniques. However, human raters outperformed Grammarly in detecting grammatical errors and were more accurate in identifying structure-related mistakes. On the other hand, Grammarly was found more effective in detecting errors related to spelling and punctuation. These findings imply using focused CF to exploit both methods. Teachers can implement their regular CF approach to develop structural aspects of language. Further, they can encourage students to adopt sophisticated writing assistants to develop their writing mechanics. To account for the potential limitations of the current study, further research that employs a larger sample size and is conducted on longitudinal and experimental bases is required.

Lidia Deviga, Radian Arum Ardhani

The aim of this research was to find out the using picture series in teaching writing skill for the second  semester students of medical record program in STIKES Bhakti Husada Mulia Madiun. This study was done on April 2022. The method that was used in this research was descriptive research design. The techniques for collecting data were observation, interview, and documentation. The data were analyzed by displaying the data and  verification of the data. During the research, the researcher acted as the teacher and acted as an observer during the implementation of picture series. The findings of observation shows that there is good interaction between lecturer and students. The lecturer gives the task to make the students understand the material well. The finding of interview shows that By using picture series, the students can have the ideas how to start writing recount text well. They can arrange the picture series to help them in composing the writing. By using picture series the students can improve their writing based on the criteria asked by the lecturers. The criteria of the writing are based on the content, organization, vocabulary, language use and mechanics. The finding of documentation shows that the use of picture series in teaching writing recount text make the students are interested and enthusiastic, pay attention and focus on lecturers’ explanation about the material. Thus, the learning process is supported that the students are better to write from the results of their experiences to compose recount text. Thus, the use of picture series is effectively used in helping students’ improve their performance in writing recount text. The future researcher can conduct the use of picture series in other skill of English such as on speaking skill.  Furthermore, the researcher can do this study by using the other design such as the experimental research design to find better media in teaching English writing skill.

Michael Carraro, Francesco De Vanna, Feras Zweiri et al.

The present work compares 2D and 3D CFD modeling of wind turbine blades to define reduced-order models of eroded leading edge arrangements. In particular, following an extensive validation campaign of the adopted numerical models, an initially qualitative comparison is carried out on the 2D and 3D flow fields by looking at turbulent kinetic energy color maps. Promising similarities push the analysis to consequent quantitative comparisons. Thus, the differences and shared points between pressure, friction coefficients, and polar diagrams of the 3D blade and the simplified eroded 2D setup are highlighted. The analysis revealed that the inviscid characteristics of the system (i.e., pressure field and lift coefficients) are precisely described by the reduced-order 2D setup. On the other hand, discrepancies in the wall friction and the drag coefficients are systematically observed with the 2D model consistently underestimating the drag contribution by around 17% and triggering flow separation over different streamwise locations. Nevertheless, the proposed 2D model is very accurate in dealing with the more significant aerodynamics performance of the blade and 30 times faster than the 3D assessment in providing the same information. Therefore the proposed 2D CFD setup is of fundamental importance for use in a digital twin of any physical wind turbine with the aim of carefully and accurately planning maintenance, also accounting for leading edge erosion.

Narges Tabatabaei, Majid Hajipour, Fermin Mallor et al.

Wake analysis plays a significant role in wind-farm planning through the evaluation of losses and energy yield. Wind-tunnel tests for wake studies have high costs and are time-consuming. Therefore, computational fluid dynamics (CFD) emerges as an efficient alternative. An especially attractive approach is based on the solution of the Reynolds-averaged Navier–Stokes (RANS) equations with two-equation turbulence closure models. The validity of this approach and its inherent limitations, however, remain to be fully understood. To this end, detailed wind-tunnel experiments in the wake of a NACA4412 wing section profile are compared with CFD results. Two- and three-dimensional RANS simulations are carried out for a range of angles of attack up to stall conditions at a chord- and inflow-based Reynolds number of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>R</mi><msub><mi>e</mi><mi>c</mi></msub><mo>=</mo><mn>4</mn><mo>×</mo><msup><mn>10</mn><mn>5</mn></msup></mrow></semantics></math></inline-formula>. Here, we aim to investigate the wake characteristics and self-similar behaviour, both from the experimental and numerical perspectives. The measurements are carried out by means of hot-wire anemometry capturing the wake pattern in several planes. The sensitivity of the CFD model to different configurations of the setup and the considerations required for reliable simulation are discussed. The agreement between CFD, experiments, and the literature is fairly good in many aspects, including the self-similar behaviour and wake parameters, as well as the flow field. Comparison of experiments with URANS/RANS data indicates that the latter is an adequate methodology to characterize wings and their wakes once the CFD setup is designed appropriately and the limitations due to discretization and turbulence modelling are considered.

Federico Califano, Ramy Rashad, Stefano Stramigioli

A description of thermodynamics for continuum mechanical systems is presented in the coordinate-free language of exterior calculus. First, a careful description of the mathematical tools that are needed to formulate the relevant conservation laws is given. Second, following an axiomatic approach, the two thermodynamic principles will be described, leading to a consistent description of entropy creation mechanisms on manifolds. Third, a specialisation to Fourier-Navier-Stokes fluids will be carried through.

Femi Olawale, Opeyemi Iwaloye, O. Elekofehinti

Abstract The over-expression of Polo-like kinase-1 (PLK1) is associated with cancer prognosis due to its pivotal role in cell proliferation. The N-terminal catalytic domain (NCD) and C-terminal polo box domain (PBD) of PLK1 are critical for the activity of the protein. Drugs that inhibit PLK1 by targeting these domains are on clinical trials, but so far, none has been approved by FDA. Thus, this study targets the two domains of PLK1 to identify compounds with inhibitory potential. Four validated e-pharmacophore models from NCD (PDB ID: 2OU7 and 4J52) and PBD (PDB ID: 5NEI and 5NN2) were used to screen over 26,000 natural compounds from NPASS database. Hits were identified after the well-fitted compounds were subjected to molecular docking study and ADME prediction. The pIC50 and electronic behaviour of the identified hits selectively targeting NCD and PBD of PLK1 were predicted via an externally validated QSAR model and quantum mechanics. The results showed that CAA180504, CAA197326, CAA74619, CAA328856 modulating PLK1 at NCD, and CBB130581, CBB230713, CBB206123, CBB12656 and CBB267117 modulating PLK1 at PBD had better molecular docking scores, pharmacokinetics and drug-like properties than NCD (volasertib) and PBD (purpurogallin) reference inhibitors. The compounds all had satisfactory inhibitory (pIC50) values which range from 6.187 to 7.157. The electronic behaviours of understudied compounds using HOMO/LUMO and global descriptive parameters revealed the atomic portion of the compounds prone to donating and accepting electrons. In conclusion, the hit compounds identified from the library of natural compounds are worthy of further experimental validation. Communicated by Ramaswamy H. Sarma

G. Burwood, W. He, A. Fridberger et al.

Cochlear distortions afford researchers and clinicians a glimpse into the conditions and properties of inner ear signal processing mechanisms. Until recently, our examination of these distortions has been limited to measuring the vibration of the basilar membrane or recording acoustic distortion output in the ear canal. Despite its importance, the generation mechanism of cochlear distortion remains a substantial task to understand. The ability to measure the vibration of the reticular lamina in rodent models is a recent experimental advance. Surprising mechanical properties have been revealed. These properties merit both discussion in context with our current understanding of distortion, and appraisal of the significance of new interpretations of cochlear mechanics. This review focusses on some of the recent data from our research groups and discusses the implications of these data on our understanding of vocalization processing in the periphery, and their influence upon future experimental directions. This article is part of the Special Issue Outer hair cell Edited by Joseph Santos-Sacchi and Kumar Navaratnam.

Ana Camila Nobre de Lacerda Brito, Maria Danielly Lima DE Oliveira, César Augusto Souza de Andrade et al.

Abstract Background  Animal models are commonly used to assess the efficacy of new materials to be employed in the surgical repair of a nerve injury. However, there is no published surgical repair protocol for sciatic nerve neurotmesis in rats. Objective  To produce and evaluate a protocol for the tubing technique using a polyvinyl alcohol biofilm after sciatic nerve neurotmesis. Methods  Eighteen rats were randomized into 3 groups ( n  = 6 per group): control group - CG, neurotmesis group - NG, and neurotmesis biofilm group - NBG. The NG and NBG animals were submitted to neurotmesis of the sciatic nerve at 60 days of life, followed by suture of the nerve stumps; in the NBG, the animals had the suture involved by polyvinyl alcohol biofilm. A descriptive evaluation of the surgical technique was performed after the experimental period. The Shapiro-Wilk normality test was used for body weight, and analysis of variance (ANOVA) with Bonferroni posthoc ( p  < 0.05) was applied. Results  All groups showed good repair of the skin and muscle sutures; however, 33.30% of the CG presented disruption of skin points. Furthermore, 16.70% of the stumps were not structurally aligned and 33.30% had neuromas in the NG, while in the NBG, all stumps were aligned and none of them had neuroma . Conclusions  The present study was able to produce a protocol with high reproducibility in view of the mechanical stability, targeting of the nerve stumps, muscle healing, the low frequency of skin breakage and the low complexity level of the technique, and it can be used in future studies that aim to evaluate other biomaterials for nerve repair in rats.

Abdelkader Mojtabi, Khairi Sioud, Alain Bergeon et al.

This paper studies the species separation of a binary fluid in a porous cavity between two horizontal concentric cylinders, submitted to a temperature gradient. The thickness of the cavity is <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>e</mi><mo>=</mo><msub><mi>R</mi><mi>o</mi></msub><mo>−</mo><msub><mi>R</mi><mi>i</mi></msub></mrow></semantics></math></inline-formula>, where <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>R</mi><mi>i</mi></msub></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>R</mi><mi>o</mi></msub></mrow></semantics></math></inline-formula> are the internal and external radius, respectively. The numerous previous experiments performed in thermogravitational vertical columns (TGCs) showed that in order to obtain a significant separation, the thickness of the cell must be very small, compared with its height. Therefore, in our configuration, we considered <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>e</mi><mo>≪</mo><msub><mi>R</mi><mi>i</mi></msub></mrow></semantics></math></inline-formula>. The solution is assumed to be axisymmetric. Under the assumptions of parallel flow and forgotten effect, an analytical solution is obtained using Maple software, and the results are compared with those found numerically using Comsol Multiphysics. In natural convection, our results are in very good agreement with those evaluated with a regular perturbation method in powers of the dimensionless gap width <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>ε</mi><mo>=</mo><mfrac><mi>e</mi><mrow><msub><mi>R</mi><mi>i</mi></msub></mrow></mfrac><mo> </mo></mrow></semantics></math></inline-formula> of order 15, and with the Galerkin method. The species separation calculated for our configuration is very close to the one obtained in a TGC column of height: <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>H</mi><mo>=</mo><mi>π</mi><msub><mi>R</mi><mi>i</mi></msub><mo>.</mo></mrow></semantics></math></inline-formula> One of the main interests of the analytical solution presented here is that it can be used as a basic solution for a stability study analysis.

Seyed Amin Nabavizadeh, Himel Barua, Mohsen Eshraghi et al.

A multi-distribution lattice Boltzmann Bhatnagar–Gross–Krook (BGK) model with a multiple-grid lattice Boltzmann (MGLB) model is proposed to efficiently simulate natural convection over a wide range of Prandtl numbers. In this method, different grid sizes and time steps for heat transfer and fluid flow equations are chosen. The model is validated against natural convection in a square cavity, since extensive benchmark solutions are available for that problem. The proposed method can resolve the computational difficulty in simulating problems with very different time scales, in particular, when using extremely low or high Prandtl numbers. The technique can also enhance computational speed and stability while keeping the simplicity of the BGK method. Compared with the conventional lattice Boltzmann method, the simulation time can be reduced up to one-tenth of the time while maintaining the accuracy in an acceptable range. The proposed model can be extended to other lattice Boltzmann collision models and three-dimensional cases, making it a great candidate for large-scale simulations.

Balqis Fajarrina Utami, Warsono, Zulfa Sakhiyya

In Indonesia, students face more challenges in learning English as a foreign language, which means that the students face difficulties such as in mechanics, mastering grammar or vocabulary and also the topics. Every student has different learning style in writing skill. To help them solve their problems, the teacher can apply the strategy that make them easy to construct a text. The aim of this study is to investigate the effectiveness of Peer Editing and Think-Pair-Share strategy to teach writing descriptive text to Visual and Read-Write learning styles students. The objectives of this study are : (1) to explain the effectiveness of Peer Editing strategy to teach writing descriptive text to Visual learning style students. (2) to explain the effectiveness of Peer Editing strategy to teach writing descriptive text to Read-Write learning style students. (3) to explain the effectiveness of Think-Pair-Share strategy to teach writing descriptive text to Visual learning style students. (4) to explain the effectiveness of Think-Pair-Share strategy to teach writing descriptive text to read-write learning style students. (5) to evaluate which one is more effective between Peer Editing and Think-Pair-Share strategy to teach writing descriptive text to Visual and Read-Write learning style students. This research used 2x2 factorial experimental design. The result reveals that Peer Editing strategy was more effective than Think-Pair-Share strategy. The suggestion about this study is that teacher should consider the implementation of Peer Editing or Think-Pair-Share strategies to improve writing descriptive text both for Visual and Read-Write learning styles. English teachers can use the result of this study as a feedback on teaching writing activities so that the aims and goals of writing can be achieved

J. S. Langer, K. Le

Significance Conventional theories of the deformation of crystalline solids assume that the second law of thermodynamics is inapplicable to dislocations. As a result, they have been only descriptive and nonpredictive. In contrast, the thermodynamic dislocation theory (TDT), based directly on the second law, has proven capable of solving problems that are out of reach of conventional approaches. Examples include strain hardening, elastic–plastic yielding, shear banding, etc. We show that the fundamental assumptions of TDT predict a scaling relation and that this relation is confirmed by experiment. Our increased confidence in the TDT leads us to raise issues that need to be addressed for both basic and applied reasons. One example is the unsolved problem of fracture toughness in crystalline solids. The thermodynamic dislocation theory (TDT) is based on two highly unconventional assumptions: first, that driven systems containing large numbers of dislocations are subject to the second law of thermodynamics and second, that the controlling inverse timescale for these systems is the thermally activated rate at which entangled pairs of dislocations become unpinned from each other. Here, we show that these two assumptions predict a scaling relation for steady-state stress as a function of strain rate and that this relation is accurately obeyed over a wide range of experimental data for aluminum and copper. This scaling relation poses a stringent test for the validity of the TDT. The fact that the TDT passes this test means that a wide range of problems in solid mechanics, previously thought to be fundamentally intractable, can now be addressed with confidence.