bluuebunny/crossref_metadata_2025_split huggingface dataset:
US trade deficit, a reality check: New evidence incorporating asymmetric and non‐linear effects of exchange rate dynamics
Authors: Nasir Muhammad Ali , Leung Mary 
Published: May 2020

AbstractIn the context of the debate on theglobal imbalances, this study investigates the determinants of US trade balance in a non‐linear ARDL framework, which accounts for the asymmetric and non‐linear effects of real effective exchange rate dynamics. Drawing on the data from 1994Q1 to 2018Q1, our key empirical findings suggest significant evidence of short‐ and long‐run asymmetries in the relationship between the real effective exchange rate, US trade balance and its determinants. An asymmetric cumulative dynamic multiplier analysis shows evidence of anasymmetric J‐curve. Furthermore, we find that the price stability, productivity, domestic savings and fiscal deficit/discipline are crucial for the US trade balance in the short to long term. Empirical findings of this study contribute to the contemporary debate on the US trade deficit and have profound policy implications for the competitiveness of the US economy and its external balance.
Comparisons of Thermodynamic Performance of Three Types of Air-Conditioning Systems Under Ideal Processing Procedure
Authors: Peng Donggen , Luo Danting , Fu Yuting 
Published: May 2020

Abstract
As the substitution of the traditional heat pump system, the heat pump driven liquid dehumidification hybrid system and the temperature-humidity independent control system have great application potentials. In this paper, the ideal reversible processes of the three types of systems are built theoretically with their mathematical models, in order to compare their maximum coefficients of performance COPs. The results show that the COP1 of the ideal heat pump driven liquid dehumidification hybrid system is the maximum and the COP2 of the temperature-humidity independent control system is the minimum with the COP3 of the heat pump system falling between both. The COP1 increases by 100% with an increase in the indoor design temperature and relative humidity while the COP1 decreases with the increase in the ambient temperature and relative humidity. The COP2 of the temperature-humidity independent control system can be affected more significantly by supply air temperature difference and angle scale. In an ideal heat pump system, low-grade heat source utilized to reheat the processed air is a superior choice. The study results in this paper have guiding significance for the selection of three types of systems in practical applications.
Validation of Numerical Models of the Offshore Wind Turbine From the Alpha Ventus Wind Farm Against Full-Scale Measurements Within OC5 Phase III
Authors: Popko Wojciech , Robertson Amy , Jonkman Jason , Wendt Fabian , Thomas Philipp , Müller Kolja , Kretschmer Matthias , Hagen Torbjørn Ruud , Galinos Christos , Le Dreff Jean-Baptiste , Gilbert Philippe , Auriac Bertrand , Oh Sho , Qvist Jacob , Sørum Stian Høegh , Suja-Thauvin Loup , Shin Hyunkyoung , Molins Climent , Trubat Pau , Bonnet Paul , Bergua Roger , Wang Kai , Fu Pengcheng , Cai Jifeng , Cai Zhisong , Alexandre Armando , Harries Robert 
Published: May 2020

Abstract
The main objective of the Offshore Code Comparison Collaboration Continuation, with Correlation (OC5) project is validation of aero-hydro-servo-elastic simulation tools for offshore wind turbines (OWTs) through comparison of simulated results to the response data of physical systems. Phase III of the OC5 project validates OWT models against the measurements recorded on a Senvion 5M wind turbine supported by the OWEC Quattropod from the alpha ventus offshore wind farm. The following operating conditions of the wind turbine were chosen for the validation: (1) idling below the cut-in wind speed, (2) rotor-nacelle assembly (RNA) rotation maneuver below the cut-in wind speed, (3) power production below and above the rated wind speed, and (4) shutdown. A number of validation load cases were defined based on these operating conditions. The following measurements were used for validation: (1) strains and accelerations recorded on the support structure and (2) pitch, yaw, and azimuth angles, generator speed, and electrical power recorded from the RNA. Strains were not directly available from the majority of the OWT simulation tools; therefore, strains were calculated based on out-of-plane bending moments, axial forces, and cross-sectional properties of the structural members. The simulation results and measurements were compared in terms of time series, discrete Fourier transforms, power spectral densities, and probability density functions of strains and accelerometers. A good match was achieved between the measurements and models setup by OC5 Phase III participants.
The Development and Applications of a Loading Distribution Based Tip Leakage Loss Model for Unshrouded Gas Turbines
Authors: Yang Hongkai , Zhang Weihao , Zou Zhengping , Zhang Shaowen , Zeng Fei , Xu Wenqi 
Published: May 2020

Abstract
The prediction of tip leakage flow aerothermal loss plays a crucial role in turbine preliminary design, which strongly affects the turbine performance. A new tip leakage loss model for unshrouded turbine is developed in this paper, considering the compressible flow aerothermal process inside the clearance. By coupling with a parameterized loading distribution model proposed in this work, in which the blade loading can be described by four independent parameters, Zweifel coefficient (Zw), diffusion factor (DF), peak velocity location (PVL), and leading edge acceleration (LEA), the loss model can evaluate the tip leakage loss in aerodynamic design process conveniently and accurately. The proposed models are validated by numerical simulations and the results show that, compared with the other acknowledged loss models, the loss model can reduce the deviations by more than 50%. Based on the models, the effects of blade loading design parameters on tip leakage losses are discussed via analysis of variance (ANOVA). The results show that Zw has the most significant influence. As Zw decreases from 1.0 to 0.7, tip leakage losses can be reduced by about 16%. Under lower Zw conditions, the joint effect of PVL and LEA is remarkable. However, under higher Zw conditions, the joint effect of the DF and PVL is more important.
Muscle Contributions to Balance Control During Amputee and Nonamputee Stair Ascent
Authors: Harper Nicole G. , Wilken Jason M. , Neptune Richard R. 
Published: May 2020

Abstract
Dynamic balance is controlled by lower-limb muscles and is more difficult to maintain during stair ascent compared to level walking. As a result, individuals with lower-limb amputations often have difficulty ascending stairs and are more susceptible to falls. The purpose of this study was to identify the biomechanical mechanisms used by individuals with and without amputation to control dynamic balance during stair ascent. Three-dimensional muscle-actuated forward dynamics simulations of amputee and nonamputee stair ascent were developed and contributions of individual muscles, the passive prosthesis, and gravity to the time rate of change of angular momentum were determined. The prosthesis replicated the role of nonamputee plantarflexors in the sagittal plane by contributing to forward angular momentum. The prosthesis largely replicated the role of nonamputee plantarflexors in the transverse plane but resulted in a greater change of angular momentum. In the frontal plane, the prosthesis and nonamputee plantarflexors contributed oppositely during the first half of stance while during the second half of stance, the prosthesis contributed to a much smaller extent. This resulted in altered contributions from the intact leg plantarflexors, vastii and hamstrings, and the intact and residual leg hip abductors. Therefore, prosthetic devices with altered contributions to frontal-plane angular momentum could improve balance control during amputee stair ascent and minimize necessary muscle compensations. In addition, targeted training could improve the force production magnitude and timing of muscles that regulate angular momentum to improve balance control.
Improving Steady Computational Fluid Dynamics to Capture the Effects of Radial Mixing in Axial Compressors
Authors: Cozzi Lorenzo , Rubechini Filippo , Arnone Andrea , Schneider Andrea , Astrua Pio 
Published: May 2020

AbstractThe compressors of power-generation gas turbines (GTs) have a high stage count, blades with low aspect ratios, and large clearances. These features promote strong secondary flows. An important outcome deriving from the convection of intense secondary flows is the enhanced span-wise transport of fluid properties mainly involving the rear stages, generally referred to as “radial mixing.” An incorrect prediction of this key phenomenon may result in inaccurate performance evaluation and could mislead designers. In the rear compressor stages, the stream-wise vorticity associated with tip clearance flows is one of the main drivers of the span-wise transport phenomenon. Limiting it by averaging the flow at row interfaces is the reason why a steady analysis underpredicts radial mixing. To properly forecast the span-wise transport, an unsteady analysis should be adopted. However, this approach has a computational cost not yet suitable for industrial purposes. Currently, only the steady simulation can fit in a lean design chain and any model upgrade improving its radial mixing prediction would be highly beneficial. To attain some progresses in Reynolds-averaged Navier–Stokes (RANS) model, its lack of convection of stream-wise vorticity must be addressed. This can be done by acting on another mixing driver that is turbulent diffusion; by enhancing turbulent viscosity, one can promote span-wise diffusion, thus improving the radial mixing prediction. In this paper, this strategy to update the RANS model and its application on an existing compressor is presented, together with the model tuning that has been performed using unsteady results as the target.
Training Load and Carbohydrate Periodization Practices of Elite Male Australian Football Players: Evidence of Fueling for the Work Required
Authors: Routledge Harry E. , Graham Stuart , Di Michele Rocco , Burgess Darren , Erskine Robert M. , Close Graeme L. , Morton James P. 
Published: May 2020

The authors aimed to quantify (a) the periodization of physical loading and daily carbohydrate (CHO) intake across an in-season weekly microcycle of Australian Football and (b) the quantity and source of CHO consumed during game play and training. Physical loading (via global positioning system technology) and daily CHO intake (via a combination of 24-hr recall, food diaries, and remote food photographic method) were assessed in 42 professional male players during two weekly microcycles comprising a home and away fixture. The players also reported the source and quantity of CHO consumed during all games (n = 22 games) and on the training session completed 4 days before each game (n = 22 sessions). The total distance was greater (p < .05) on game day (GD; 13 km) versus all training days. The total distance differed between training days, where GD-2 (8 km) was higher than GD-1, GD-3, and GD-4 (3.5, 0, and 7 km, respectively). The daily CHO intake was also different between training days, with reported intakes of 1.8, 1.4, 2.5, and 4.5 g/kg body mass on GD-4, GD-3, GD-2, and GD-1, respectively. The CHO intake was greater (p < .05) during games (59 ± 19 g) compared with training (1 ± 1 g), where in the former, 75% of the CHO consumed was from fluids as opposed to gels. Although the data suggest that Australian Football players practice elements of CHO periodization, the low absolute CHO intakes likely represent considerable underreporting in this population. Even when accounting for potential underreporting, the data also suggest Australian Football players underconsume CHO in relation to the physical demands of training and competition.
Effect of Tethered Swimming as Postactivation Potentiation on Swimming Performance and Technical, Hemophysiological, and Psychophysiological Variables in Adolescent Swimmers
Authors: Abbes Zied , Haddad Monoem , Bibi Khalid W. , Mujika Iñigo , Martin Cyril , Chamari Karim 
Published: May 2020

Objectives: To investigate whether tethered swimming (TS) performed 8 minutes before a 50-m freestyle swimming sprint could be an effective postactivation potentiation method to improve performance in young swimmers. Methods: Fourteen regional-level male adolescent swimmers (age 13.0 [2.0] y; height 161.1 [12.4] cm; body mass 52.5 [9.5] kg) underwent 2 trial conditions in a randomized and counterbalanced order (1 experimental [TS], 1 control) on different days. During the experimental session, the participants performed a standard warm-up of 1200 m followed by a TS exercise, which consisted of 3 × 10-second maximal efforts of TS with 1-minute rests between bouts. In the control condition, the warm-up phase was immediately followed by 200 m at a moderate pace (same duration as the TS in the experimental session). Performance (time trial); biomechanical (stroke length), physiological (blood lactate concentrations), and psychophysiological (ratings of perceived exertion) variables; and countermovement-jump (CMJ) flight time were collected. Results: TS warm-up had no significant effect on 50-m swimming performance (P = .27), postexercise ratings of perceived exertion, stroke length, or CMJ flight time (P ≥ .05). Blood lactate concentrations significantly increased at the end of the warm-up in the TS condition only (interaction effect: F1.91,29.91 = 4.91, P = .01, η2 = .27) and after the 50-m trial in both conditions (F1.57,20.41 = 62.39, P = .001, η2 = .82). Conclusions: The present study demonstrated that 3 × 10-second TS exercises performed 8 minutes prior to the event did not affect ratings of perceived exertion, stroke length, or CMJ flight time. In addition, tethered swimming did not affect 50-m freestyle sprint performance in young swimmers.
Effect of a Marathon on Skin Temperature Response After a Cold-Stress Test and Its Relationship With Perceptive, Performance, and Oxidative-Stress Biomarkers
Authors: Priego-Quesada Jose Ignacio , Pérez-Guarner Alejandro , Gandia-Soriano Alexis , Oficial-Casado Fran , Galindo Carlos , Cibrián Ortiz de Anda Rosa M. , Piñeiro-Ramos José David , Sánchez-Illana Ángel , Kuligowski Julia , Gomes Barbosa Marco A. , Vento Máximo , Salvador Palmer Rosario 
Published: May 2020

Context: Although skin-temperature assessment has received much attention in recent years as a possible internal-load measurement, scientific evidence is scarce. Purpose: To analyze baseline skin temperature and its rewarming through means of a cold-stress test before and after performing a marathon and to study the association between skin temperature and internal/external-load measurements. Methods: A total of 16 runners were measured 48 and 24 h before and 24 and 48 h after completing a marathon. The measurements on each day of testing included urine biomarkers of oxidative stress, pain and fatigue perception, skin temperature (at baseline and after a cold-stress test), and jump performance. Results: Reduced jump performance (P < .01 and effect size [ES] = 0.5) and higher fatigue and pain perception were observed 24 h after the marathon (P < .01 and ES > 0.8). Although no differences in baseline skin temperature were observed between the 4 measuring days, posterior legs presented lower constant (P < .01 and ES = 1.4) and higher slope (P = .04 and ES = 1.1) parameters in the algorithmic equations fitted for skin-temperature recovery after the cold-stress test 24 h after the marathon than on the day before the marathon. Regressions showed that skin-temperature parameters could be predicted by the ratio of ortho-tyrosine isomer to phenylalanine (oxidative stress biomarker) and body fat composition, among others. Conclusions: Although baseline skin temperature was not altered 24 or 48 h after a marathon, the application of cold stress after the marathon would appear to be a good method for providing information on vasoconstriction and a runner’s state of stress.
Multiyear Square Dancing Is Associated With Superior Mental Processing Capacity But Not Memory in Middle-Aged and Older Chinese Women: A Cross-Sectional Propensity Score Matching Analysis
Authors: Liao Jing , Yang Yung-Jen , Xu Dong (Roman) 
Published: May 2020

Background: Evidence suggests the importance of physical activity and social engagement in cognitive preservation. Group-based dancing combining exercise and prosocial features may generate physical and cognitive benefits.Objectives: To investigate the association between multiyear habitual square dancing and domain-specific cognitive function, and assess the relative importance and joint impact of physical activity and social activity on cognition.Methods: Using the cross-sectional propensity score matching method, the study compared the mental status, episodic memory, and overall cognitive performances of 145 amateur female square-dancing participants (aged ≥45 y) to their sociodemographic- and health-status–matched 222 nondancing counterparts, selected from the China Health and Retirement Longitudinal Study.Results: The authors found a positive association between multiyear square dancing (average 8 y) and overall cognitive performances (mean difference = 2.84; 95% confidence interval [CI], 1.65 to 4.02), which was apparent in processing capacity (2.29; 95% CI, 1.51 to 3.07) but not in memory (0.55; 95% CI, −0.13 to 1.23). The hypothesized synergic effect of physical activity and social activity on cognition was only observed in group-based exercises embodying these 2 components simultaneously.Conclusions: Long-term square dancing as one type of physically and socially engaging activities may preserve cognition. Future longitudinal and interventional studies are needed to further clarify the causal relationship.
Fitness-Related Self-Conscious Emotions and Risk for Exercise Addiction: Examining the Mediating Role of Passion
Authors: Sicilia Alvaro , Alcaraz-Ibáñez Manuel , Dumitru Delia C. , Paterna Adrian , Griffiths Mark D. 
Published: May 2020

Fitness-related self-conscious emotions (SCEs) have been proposed as antecedents of exercise addiction (EA). However, the potential mechanisms underlying such a relationship remain unexplored. The present study examined the relationship between fitness-related SCEs and risk of EA, as well as the mediating role of passion for exercise. A total of 296 male runners (M = 40.35 years, SD = 10.69) completed a survey assessing weekly exercise frequency/hours, fitness-related SCEs, passion for exercise, and the risk of EA. The relationships between the study variables were examined using structural equation modeling. After controlling for age and weekly exercise frequency/hours, fitness-related SCEs of shame, guilt, and hubristic pride were positively associated with risk of EA. However, while guilt had direct effects on risk of EA, shame and hubristic pride showed indirect effects via obsessive passion. The results of the study are discussed, and some practical implications and future research directions are presented.
The Relationship Between Injury-Related Fear and Visuomotor Reaction Time in Individuals With a History of Anterior Cruciate Ligament Reconstruction
Authors: Genoese Francesca , Baez Shelby E. , Heebner Nicholas , Hoch Matthew C. , Hoch Johanna M. 
Published: May 2020

Context: Deficits in reaction time, decreased self-reported knee function, and elevated levels of injury-related fear have been observed in individuals who sustain anterior cruciate ligament injury. Understanding the relationship between these variables may provide the impetus to further investigate effective intervention strategies to address these deficits in individuals after anterior cruciate ligament reconstruction (ACLR). Objective: To examine the relationship between injury-related fear and lower-extremity visuomotor reaction time (VMRT) in individuals with a history of ACLR. A secondary purpose was to determine the relationship between self-reported knee function and lower-extremity VMRT in individuals with a history of ACLR. Design: Cross-sectional study. Setting: Laboratory. Participants: Twenty participants between the ages of 18–35 years, with history of unilateral ACLR within the last 10 years, who injured their knee playing or training for organized or recreational sports. Main Outcome Measures: Scores on the athlete fear avoidance questionnaire, the fear-avoidance beliefs questionnaire (FABQ), the knee injury and osteoarthritis outcome score, and reaction time (in seconds) on the lower-extremity VMRT task using the FitLight Trainer™, bilaterally. Spearman Rho correlations examined the relationship between the dependent variables. Results: There was a moderate positive correlation between VMRT and FABQ-total (r = .62, P < .01), FABQ-sport (r = .56, P = .01), and FABQ-physical activity (r = .64, P < .01) for the injured limb. Correlations between FABQ scores and VMRT for the uninjured limb were weak positive correlations (r = .36–.41, P > .05). Weak correlations between the osteoarthritis outcome score subscales, athlete fear avoidance questionnaire, and VMRT were observed for the injured limb (P > .05). Conclusions: Individuals with a history of ACLR who exhibited elevated levels of injury-related fear demonstrated slower VMRT. There were no relationships between self-reported knee function and VMRT. Future research should explore interventions to address injury-related fear and VMRT in individuals after ACLR.