Mechanical Engineering

A new simple “four-variable shear deformation” plate model is proposed in this work to demonstrate the hygro-thermal environment effects on dynamic and buckling of functionally graded material “sandwich plates” supported by “Winkler–Pasternak” elastic foundations. Equations of motion are obtained from Hamilton’s principle containing the hygro-thermal influences. This model uses only “four variables” and considers trigonometric variation of “transverse shear stress.” In addition, these stresses become zero at the upper and lower surfaces of the “sandwich plate.” The novelty of this formulation is the addition of the integral term in the field of displacement, which leads to a reduction of the number of unknowns and basic equations. Various kinds of functionally graded material “sandwich plates” are examined in this study. To verify the validity of the model, the calculated results are compared with the existing results. Comparison investigations reveal that the computed results of th...

We report on a Chirped Pulse Amplification (CPA)-based Titanium:Sapphire (Ti:Al2O3 or Ti:Sapphire) amplifier that uses a single grating stretcher and compressor configuration. The 8-pass amplifier configuration is able to yield 70 μJ pulse energy at 10 Hz repetition rate, which corresponds to a gain of 7000 times. The amplified pulses are expected to be transform-limited with pulse duration of 85 fs. This amplifier will expand the application of our Ti:Sapphire laser at the Vietnam Academy of Sciences (VAST).

Purpose This paper aims to investigate the role of shapes of containers (nine different containers) on entropy generation minimization involving identical cross-sectional area (1 sq. unit) in the presence of identical heating (isothermal). The nine containers are categorized into three classes based on their geometric similarities (Class 1: square, tilted square and parallelogram; Class 2: trapezoidal type 1, trapezoidal type 2 and triangular; Class 3: convex, concave and curved triangular). Design/methodology/approach Galerkin finite element method is used to solve the governing equations for a representative fluid (engine oil: Pr = 155) at Ra = 103–105. In addition, finite element method is used to solve the streamfunction equation and evaluate the entropy generation terms (Sψ and Sθ). Average Nusselt number ( Nub¯) and average dimensionless spatial temperature ( θ^) are also evaluated via the finite element basis sets. Findings Based on larger Nub¯, larger θ^ and optimal Stotal v...

This study compared the metabolic, cardiopulmonary and inflammatory responses of novel acute machine based concentrically-focused resistance exercise (CON RX) and eccentrically-focused resistance exercise (ECC RX). Twenty healthy adults (26.8 ± 5.9 yrs; 25.4 ± 4.0 kg/m(2)) performed two work-matched RX exercise sessions. Cardiopulmonary responses, rating of perceived exertion (RPE), soreness, oxygen consumption; (VO2) were collected during each session. Blood lactate and levels of inflammatory cytokines interleukin-1 alpha (IL1α), interleukin-6 (IL6) and tumor necrosis factor-alpha (TNFα) were analyzed pre, post ad 24 hours post-exercise. HR were higher (5-15bpm) during ECC RX (p<.05). Soreness ratings were consistently higher post-ECC RX compared to CON RX. VO2 area under the curve was higher during ECC than CON (31,905 ml/kg/min vs 25,864 ml/kg/min; p<.0001). Post-ECC RX, TNFα levels increased compared to CON RX 23.2 ± 23.9% versus 6.3 ± 16.2% ( p=.021). ECC RX induced great...

This paper investigates the air bubble size and its transitions in a horizontal tube of 700 mm. The tube is assembled with a bubble generator. The present study varies the flow-rates of water and air. The data collection mainly uses a high speed camera to capture the bubbles at different distances along the horizontal tube. Image processing uses MATLAB for evaluating the bubble size. The data interpretation uses Yw dimensionless parameter in representing the level of the bubbles vertical rise in the horizontal tube. The bubble generator produces bubbles in the range of 0.8-3.1 mm at the inlet of horizontal tube using water flow-rates (Qw) of 120-170 litre per min (LPM) and air flow-rates (Qa) of 2-10 LPM. The diameter of the bubble increases as it moves horizontally from the inlet to the outlet of the horizontal tube and this finding is statistically significant. The bubble vertical rise is visually obvious and has been quantified along the horizontal tube. The YW increases axially ...

Towards industry 4.0, monitoring the degradation of machine tools’ components becomes a key feature so that smooth productivity is achieved. To preserve the functionality and performance of the machine tools, proper maintenance activities must be planned and carried out. V-belt is important component in machine tools that transmits power from the electric motor spindle in order to machine to work and cut desired material properly. The purpose of this research is to develop a predictive maintenance system for v-belt milling machine Krisbow 31N2F using machine learning. The machine learning algorithm models using multiple and simple linear regression algorithm was developed in an open-source program. The test results show that the machine learning model has a high accuracy value in both the training data and the testing data. The multiple linear regression model has MSE value of 5.8830x10-6 and MAE value of 0.002. The Simple linear regression model has an MSE value of 0.0004x10-6 and ...

We hypothesized that student-athletes’ athletic identity and motivation are influenced by their own institutions sport policies. The aim of the study is twofold: a) to validate a measure of athletic identity among Portuguese college students; b) to analyze the effects of 3 different types of college policies on identity and motivation. This study used a quantitative design. 201 Portuguese student-athletes answered to two questionnaires, BIMS (Baller Identity Measurement Scale) and SAMSAQ (Student Athletes Motivation towards Sports and Academics Questionnaire). To comparative purposes, three types of university were considered according to their institutions’ sport policies: type 1 (i.e sport organized exclusively by higher education institutes (HEIs)), type 2 (i.e organized by HEIs and/or student associations) and type 3 (i.e organized outside the HEIs). The CFA showed the adjustment of the model of BIMS with two factors for Portuguese student-athlete (emotions and exclusivity) (CFI...

Relative age effect (RAE) is considered to bias the selection of young athletes and a cause of exclusion of many participants. The goal of the study was to unveil the effects of the birth quarter on physical performances and a set of psychological constructs in the age groups corresponding to the specialization years. A set of surveys with cross-sectional data collected from 2015 to 2019 in youth basketball was used. Three hundred and twenty-seven Brazilian players (127 females, 100 males), mean age 14.0 years, participated in the study. Counter-movement jump, line-drill, yoyo intermittent test, achievement goals, motivation for deliberate practice, and enjoyment were measured. Bayesian multilevel regression was performed. RAE was observed but its advantages did not persist and did not differentiate the players in the variables under scrutiny. The only predictor of athletic and psychological outcomes was chronological age. The initial advantage that triggered the coaches' decisi...

We considered identity variation among Brazilian university student-athletes in relation to their gender, sport type, competition level, and university type. Participants were 506 student-athletes (219 males and 287 females) from public and private Brazilian universities, competing in team and individual sports, at local, state, and national levels. We used multilevel regression and poststratification to estimate each participant’s identity from the aforementioned variables. Gender and sport type were not associated with any substantial identify variation, but there were higher values on Baller Identity Measurement Scale dimensions for student-athletes from public versus private universities, and student-athletes competing at the highest level had lower Baller Identity Measurement Scale values compared to peers competing at lower levels. Overall, university type and sport competitive level were the contextual factors that most influenced Brazilian student-athletes’ identities.

The study examined the validity of the Line Drill test (LD) in male adolescent basketball players (10-15 years). Sensitiveness of the LD to changes in performance across a training and competition season (4 months) was also considered. Age, maturation, body size and LD were measured (n = 57). Sensitiveness of the LD was examined pre- and post-competitive season in a sub-sample (n = 44). The time at each of the four shuttle sprints of the LD (i.e. four stages) was modelled with Bayesian multilevel models. We observed very large correlation of performance at stage 4 (full LD protocol) with stage 3, but lower correlations with the early LD stages. Players' performance by somatic maturity differed substantially only when considering full LD protocol performance. Substantial improvements in all stages of the protocol were observed across the 4-month competitive season. The LD protocol should be shortened by the last full court shuttle sprint, remaining sensitive to training exposure,...