bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Correlation for Heat Transfer Coefficient Prediction of Supercritical Pressure Water Flowing in Vertical Upward Tubes
Authors: Kong Xiangfei , Li Huixiong , Liao Changjiang , Lei Xianliang , Zhang Qian
Published: November 2016

Supercritical pressure water has been widely used in many industrial fields, such as fossil-fired power plants and nuclear reactors because mainly of its high thermal efficiencies. Although many empirical correlations for heat transfer coefficients of supercritical pressure water have been proposed by different authors based on different experimental data base, there exist remarkable discrepancies between the predicted heat transfer coefficients of different correlations under even the same condition. Heat transfer correlations with good prediction performance are of considerable significance for developing supercritical (ultra-supercritical) pressure boilers and SCWRs. In this paper, the experimental data (about 7389 experimental data points) and 30 existing empirical correlations for heat transfer of supercritical pressure water (SCW) flowing in vertical upward tubes are collected from the open literatures. Evaluations of the prediction performance of the existing correlations are conducted based on the collected experimental data, and a detailed multi-collinearity analysis has been made on different correction factors involved in the existing correlations, and then based on the collected experimental data, a new heat transfer correlation is developed for the supercritical pressure water flowing in vertical upward tubes under normal and enhanced heat transfer mode. Compared with the existing correlations, the new correlation exhibits good prediction accuracy, with a mean absolute deviation (MAD) of 9.63%.
Numerical Modeling of Chevron Plate Heat Exchangers for Thermal Management Applications
Authors: Tamakuwala Harsh , Von Ness Ryan , Banerjee Debjyoti
Published: November 2016

Plate-fin heat exchangers are widely used in industries especially aerospace, cryogenics, food and chemical process industries where high heat flux surface area per unit volume is of prime importance. These heat exchangers consists of series of corrugated plates (herringbone or chevron), separated by gasket sealing. Chevron angled plates are one of the most commonly used type of geometry. The complex design of chevron plate heat exchanger, induces high turbulence and flow reversals causing high heat transfer through the plates. This paper discusses about the computational fluid dynamics simulations conducted over a simplified geometry of Chevron Plate Heat Exchanger to understand the formulation of vortices at different Reynold’s number for various aspect ratios. A single phase laminar flow with periodic boundary condition is used for analysis of the fluid behavior in a unit pattern of the corrugation geometry. Based on different flow and geometric conditions, varying amounts of swirl-flows are observed and different behavior of shear stress and heat transfer plot along the length of the plate is observed. At higher Reynolds numbers (Re), the re-circulations and mixing by the induced vortices causes significant rise of heat flux, with marginal increase in friction factor.
An Experimental Study of Inward Solidification of Nano-Enhanced Phase Change Materials (NePCM) Inside a Spherical Capsule
Authors: Liu Min-Jie , Zhu Zi-Qin , Fan Li-Wu , Yu Zi-Tao
Published: November 2016

Nano-enhanced phase change materials (PCM), referred to as NePCM, have been proposed by doping highly thermally-conductive nanofillers into matrix PCM to prepare composites that have enhanced thermal conductivity. The classical problem of inward solidification of PCM inside a spherical capsule, with applications to thermal energy storage, was revisited in the presence of nanofillers. In this work, the model NePCM samples were prepared with 1-tetradecanol (C14H30O) possessing a nominal melting point of 37 °C as the matrix PCM. Graphite nanoplatelets (GNPs) were synthesized and utilized as the nanofillers at loadings up to 1% by weight. The transient phase change and heat transfer during solidification were characterized by means of an indirect method that is based on the knowledge of transient volume shrinkage of the PCM. The experimental results showed that the total solidification time becomes shorter with increasing the loading of GNPs, in accordance to the increased effective thermal conductivity of the NePCM samples.
Dynamics of Droplet Motion Induced by Electrowetting
Authors: Lu Yi , Sur Aritra , Liu Dong , Pascente Carmen , Ruchhoeft Paul
Published: November 2016

Electrowetting has drawn significant interests due to the potential applications in electronic displays, lab-on-a-chip devices and electro-optical switches, etc. Current understanding of electrowetting-induced droplet dynamics is hindered by the inadequacy of available numerical and theoretical models in properly handling the dynamic contact angle at the moving contact line. A combined numerical and experimental approach was employed in this work to study the spatiotemporal responses of a droplet subject to EW with both direct current and alternating current actuating signals. The time evolution of the droplet shape was measured using high-speed photography. Computational fluid dynamics models were developed by using the Volume of Fluid-Continuous Surface Force method in conjunction with a selected dynamic contact angle model. It was found that the numerical models were able to accurately predict the key parameters of the electrowetting-induced droplet dynamics.
Effects of Field Plate on the Maximum Temperature and Temperature Distribution for GaN HEMT Devices
Authors: Kara Dogacan , Donmezer Nazli , Canan Talha Furkan , Sen Ozlem , Ozbay Ekmel
Published: November 2016

Field plated GaN high electron mobility transistors (HEMTs) are widely preferred amongst other GaN HEMT devices because of their ability to regulate electric field at high power densities. When operated at high power densities, GaN HEMTs suffer significantly from the concentrated heating effects in a small region called hotspot located closer to the drain edge of the gate. Although; the stabilizing effect of field plate on the electrical field distribution in HEMTs is known by researchers, its effect on temperature distribution and the hotspot temperature is still not studied to a greater extend. For this purpose, finite element thermal modelling of devices with different sizes of field plates are performed using the joule heating distribution data obtained from 2D electrical simulations. Results obtained from such combined model show that the existence of a field plate changes the electrical field, therefore the heat generation distribution within device. Moreover; increasing the size of the field plate has an effect on the maximum temperature at the hotspot region. The results are used to analyze these effects and improve usage of field plates for high electron mobility transistors to obtain better temperature profiles.
Pore-Scale Modeling of Natural Convection in Reconstructed Porous Media
Authors: Liu Zhenyu , Wu Huiying
Published: November 2016

The utilization of porous media can enhance the heat transfer process due to its large heat transfer area within limited space. The natural convection in porous media widely exists in various heat transfer equipment and the related flow and heat transfer in porous spaces is one complicated transport phenomenon, for which the accurate prediction is challenging. Pore-scale models can predict transport phenomena in porous media in pore space, which can be used in the modeling of flow and heat transfer in porous media under local thermal non-equilibrium condition. The pore-scale study includes the reconstruction of porous structure and the direct numerical simulation of transport phenomena in the pore spaces. In this paper, the geometrical reconstruction approach was developed to generate the porous region using the tomographic reconstruction, which is one nondestructive imaging technique. The porous sample was scanned on a micro-CT scanner with micrometer resolution. 2D sliced scan images were obtained and then stacked to reconstruct the 3D porous geometry. A double-population thermal lattice Boltzmann model was established to predict the natural convection in reconstructed porous media at pore scale.
Numerical Study of Heat Conduction of High Porosity Open-Cell Metal Foam/Paraffin Composite at Pore Scale
Authors: Yao Yuanpeng , Wu Huiying , Liu Zhenyu
Published: November 2016

In this paper, a numerical model employing 3D foam structure represented by Weaire-Phelan foam cell is developed to study the steady heat conduction of high porosity open-cell metal foam/paraffin composite at the pore-scale level. Two conduction problems are considered in the cubic representative computation unit of the composite material: one with constant temperature difference between opposite sides of the cubic unit (that can be used to determine the effective thermal conductivity (ETC)) and the second with constant heat flux at the interface between metal foam and paraffin (that can be used to determine the interstitial conduction heat transfer coefficient (ICHTC)). The effects of foam pore structure parameters (pore size and porosity) on heat conduction are investigated for the above two problems. Results show that for the first conduction problem, the effect of foam structure on heat conduction (i.e. the ETC) is related to porosity rather than pore size. The essential reason is due to the thermal equilibrium state between metal foam and paraffin indicated by the negligible interstitial heat transfer. While for the second conduction problem with inherent thermal non-equilibrium effect, it shows that both porosity and pore size significantly influence the interstitial heat conduction (i.e. the ICHTC). Furthermore, the present ETC and ICHTC data are compared to the results in the published literature. It shows that our ETC data agree well with the reported experimental results, and are more accurate than the numerical predications based on body-centered-cubic foam cell in literature. And our ICHTC data are in qualitative agreement with the published numerical results, but the present results are based on a more realistic foam structure.
Sweating-Boosted Air Cooling With Water Dripping
Authors: Wang Pengtao , Dawas Raikan , Alwazzan Mohammad , Stefik Morgan , Khan Jamil , Li Chen
Published: November 2016

In power plants, the condenser section plays an important role in total thermal efficiency. Extensive considerations by researchers are put toward increasing the heat dissipation efficiency while maintaining low cost and water consumption. One way to archive such situation is to consider replacing the water cooled condenser (WCC) with an air cooled condenser (ACC), but resulting in a significant increase in the condenser size due to the relatively low heat transfer coefficient (HTC = 20–50 W/m2K) of the air compared to that of the water. Inspired by the phase change heat transfer of water during the perspiration of mammals, a sweating boosted air cooling approach is proposed herein to dramatically increasing the HTC and minimizing the water consumption. In this experimental study, a wind tunnel and distilled water dripping system were used to examine the thermal performance of copper samples with a tested surface area of 2 in by 2 in. Two surface enhancement approaches were adapted herein. In the first approach, the testing samples were integrated with microchannels, copper woven meshes (200 meshes/in) that were sintered on top of the surface, and finally nanostructures that was synthesized by a hot alkaline oxidation process. In the second approach, the tested samples were coated with TiO2 via an atomic layer deposition (ALD) process.

This method allows for rapidly spreading of the dripping water droplets over the whole tested surface. This rapid spreading behavior is due to two main reasons, first the low resistance flow of microchannel which delivered the water globally; second the high capillary pressure generated by the micro-/nano-structures which delivered the water locally. Three different flat-surface samples were developed in this study, as flat surface with sintered copper meshes (design A), grooved surface with sintered copper meshes (design B); and grooved surface with sintered copper meshes coated with ALD TiO2 film (design C).

The performance of the surfaces of this approach was quantitatively characterized with the wick testing. The heat transfer performances for all samples were also examined. The experimental results showed that the convection heat transfer plays a limited role in the heat dissipation. In addition, HTC was enhanced by increasing the dripping water rate consumption until the surface reached the flooding condition. The results showed that the evaporation rate of water was augmented with the increase of Reynolds number. The maximum HTC was 182.45 W/m2K with a water dripping rate of 12 ml/h, resulting in an enhancement approximately 214.07% compared to the case without water dripping. Further research on a higher HTC requires an optimized combination of Reynolds number and water consumption.
A Numerical Parametric Study of Flow and Heat Transfer in Circular and Zig-Zag Square Microchannel Heat Sinks
Authors: Li Wenming , Yang Fanghao , Alam Tamanna , Ren Congcong
Published: November 2016

This paper aims to study the overall performance of circular and zig-zag square microchannel heat sinks with single phase liquid flow via a numerical parametric study. Thermal resistance and pressure drop when subjected to key geometric parameters such as hydraulic diameter, orientation, and connector length is numerically investigated with Reynolds number ranging from 50 to 500. Specifically, the hydraulic diameter is varied from 100 μm to 300 μm with an increment of 100 μm; the orientation angle of 10°, 20° and 30° is studied. A figure of merit (FOM) involving both the thermal resistance and pressure drop is introduced to evaluate the performance. Results show that hydraulic diameter is critical to thermal resistance and pressure drop compared to orientation angle. Zig-zag microchannel heat sink shows better performance compared with heat sinks with circular microchannel. FOM varies considerably with the change in hydraulic diameter and flow rate.
Application of Inverse Heat Conduction Method and Method of Lines in Spray Cooling of Heated Surface
Authors: Soujoudi Ramin
Published: November 2016

This paper investigates application of Method of Lines (MOL) and Inverse Heat Conduction techniques in spray cooling process. A flat face of a heated cylinder is cooled by using a nozzle spray and using room temperature water as a cooling fluid. The numerical analysis is done using MOL to estimate exposed surface temperature, surface heat flux, and convection heat transfer coefficient [3],[4]. Since there is no exact solution to verify the approximation result, for the verification purpose and accuracy of the result, the numerical result from this study is compared to other approximation results with experimental research done by Chen-Lee and Qiao-Chandra [1]. The results illustrate that disparity between the outcome of MOL and the one generated by Chen and Lee’s raw data is very insignificant throughout the whole time domain. This discrepancy between these two estimated results proves that MOL is a very reliable approximation technique compared to other finite element methods which require a finer mesh size and significant amount of calculations[2],[5]. However, comparing the results obtained through MOL with Qiao and Chandra shows that the difference between the estimated heat transfer coefficient and estimated heat flux converges rapidly for the short times of 0 < t < 60, but as the time passes, the MOL approximation results diverge slowly until it reaches its maximum value at ninety seconds, and the variance remains almost constant for the rest of the time period.
Suspended Particle Streaming in an Oscillatory Mini/Micro Bifurcation Network Flow
Authors: Zhang Zongqin , Liu Chandler , Meyer D. M. L. , Zhang Weixing , Zheng Yi
Published: November 2016

Using of oscillatory flow and phase change material (PCM) microcapsules to enhance heat transport efficiency in micro-/minichannels are among many new methodologies that have been proposed. In this paper, we propose a novel and simple heat spreader concept that integrates the technologies of oscillating flow streaming and PCM microcapsules. Phenomena of the flow streaming can be found in oscillating, zero-mean-velocity flows in many channel configurations. The pumpless flow can be generated by simple heating or by channel wall vibration. Discrepancy in velocity profiles between the forward and backward flows causes fluid and particles suspended in fluids near the walls to drift toward one end while particles near the centerline drift to the other end. Preliminary work of computer simulations on fluid and suspended particle streaming in multichannel mini-bifurcation networks flows has been conducted and verified by visualization experiments. Results show that flow streaming with PCM microcapsules entrainment has the potential to be used as a cost-effective technology in a heat spreader.
Influence of ambient gas pressure and carbon adsorption on dark current emission from a cathode
Authors: Márquez-Mijares Maykel , Lepetit Bruno , Lemoine Didier , Almaksour Khaled , Kirkpatrick Mike J. , Dessante Philippe , Odic Emmanuel , Alamarguy David , Bayle Fabien , Teste Philippe , Karlický František.
Published: November 2016

Electronic field emission current (dark current) from surfaces under vacuum at high field strengths can be reduced by the injection of gas into the ambient volume. A possible reversible mechanism responsible for this gas effect is proposed. The mechanism involves the formation of nanoscale emitter structures by polymerization of hydrocarbon contamination with low-flux ion bombardment at low pressure, and the destruction of these structures by high flux ion bombardment at sufficiently high pressure. Experimental evidence, in particular, x-ray photoelectron spectroscopy analysis of the electrode, is provided in support of this mechanism. Density functional theory calculations are presented to show that the morphology of the carbon layer, not its chemical composition, is the important parameter influencing dark current levels.
Etch stop improvement using a roof mask structure in a magnetic material etched by CO/NH3 plasma
Authors: Satake Makoto , Yamada Masaki , Matsumoto Eiji
Published: November 2016

The etching rate difference of magnetic materials with respect to the aspect ratio (AR) has been investigated using CO/NH3 plasma with a Ta mask for high-density integration of magnetic random access memory devices. The etching depth difference of magnetic stack films as a function of etching times reveals that the etching rate is suddenly reduced at AR > 0.7, and the occurrence of etch stop has been confirmed. From the scanning transmission electron microscope–energy dispersive x-ray spectroscopy results, Ta deposition, which proceeds from the Ta mask to the bottom space of the pattern, induces this etch stop. The roof mask structure, which has a concavity directly under the Ta mask to reduce the amount of Ta deposition, can improve the etch stop, and a fine magnetic stack film pattern with AR = 2.3 can be fabricated.
Examining credentialing criteria and poor performance indicators for IROC Houston's anthropomorphic head and neck phantom
Authors: Carson Mallory E. , Molineu Andrea , Taylor Paige A. , Followill David S. , Stingo Francesco C. , Kry Stephen F.
Published: November 2016

Purpose:

To analyze the most recent results of the Imaging and Radiation Oncology Core Houston Quality Assurance Center's (IROC‐H) anthropomorphic head and neck (H&N) phantom to determine the nature of failing irradiations and the feasibility of altering credentialing criteria.

Methods:

IROC‐H's H&N phantom, used for intensity‐modulated radiation therapy credentialing for National Cancer Institute–sponsored clinical trials, requires that an institution's treatment plan agrees within ±7% of measured thermoluminescent dosimeter (TLD) doses; it also requires that ≥85% of pixels pass ±4 mm distance to agreement (7%/4 mm gamma analysis for film). The authors re‐evaluated 156 phantom irradiations (November 1, 2014–October 31, 2015) according to the following tighter criteria: (1) 5% TLD and 5%/4 mm, (2) 5% TLD and 5%/3 mm, (3) 4% TLD and 4%/4 mm, and (4) 3% TLD and 3%/3 mm. Failure rates were evaluated with respect to individual film and TLD performance by location in the phantom. Overall poor phantom results were characterized qualitatively as systematic errors (correct shape and position but wrong magnitude of dose), setup errors/positional shifts, global but nonsystematic errors, and errors affecting only a local region.

Results:

The pass rate for these phantoms using current criteria was 90%. Substituting criteria 1–4 reduced the overall pass rate to 77%, 70%, 63%, and 37%, respectively. Statistical analyses indicated that the probability of noise‐induced TLD failure, even at the 5% criterion, was <0.5%. Phantom failures were generally identified by TLD (≥66% failed TLD, whereas ≥55% failed film), with most failures occurring in the primary planning target volume (≥77% of cases). Results failing current criteria or criteria 1 were primarily diagnosed as systematic >58% of the time (11/16 and 21/36 cases, respectively), with a greater extent due to underdosing. Setup/positioning errors were seen in 11%–13% of all failing cases (2/16 and 4/36 cases, respectively). Local errors (8/36 cases) could only be demonstrated at criteria 1. Only three cases of global errors were identified in these analyses. For current criteria and criteria 1, irradiations that failed from film only were overwhelmingly associated with phantom shifts/setup errors (≥80% of cases).

Conclusions:

This study highlighted that the majority of phantom failures are the result of systematic dosimetric discrepancies between the treatment planning system and the delivered dose. Further work is necessary to diagnose and resolve such dosimetric inaccuracy. In addition, the authors found that 5% TLD and 5%/4 mm gamma criteria may be both practically and theoretically achievable as an alternative to current criteria.
Objective and perceptual evaluation of distance-dependent scattered sound effects in a small variable-acoustics hall
Authors: Shtrepi Louena , Astolfi Arianna , D'Antonio Gianluca , Guski Martin
Published: November 2016

Performance spaces are characterized by a complex sound field, due to the presence of absorptive and diffusive surfaces. In situ evaluations of the acoustic effects that these surfaces have on the objective acoustic parameters and on sound perception have not yet been fully understood. To this aim, acoustic measurements have been performed in a variable-acoustic concert hall, the Espace de Projection, at the Institut de Recherche et Coordination Acoustique/Musique. These measurements have allowed the effects of one single wall to be determined. A diffusive and a reflective condition of one of the long lateral walls of the shoebox-like hall have been considered, while the other surfaces have been fixed in absorptive mode. Measurements have been carried out at different distances from the test wall, using an artificial head and an array of omnidirectional microphones. Objective acoustic parameters, such as early decay time, reverberation time (T30), clarity (C80), definition (D50), and interaural cross correlation, have been compared between both conditions. In addition to the objective indexes, a perceptual evaluation has been performed using listening tests that had the purpose of determining the maximum distance from a diffusive surface at which acoustic scattering effects are still audible.
Volterra model of the parametric array loudspeaker operating at ultrasonic frequencies
Authors: Shi Chuang , Kajikawa Yoshinobu
Published: November 2016

The parametric array loudspeaker (PAL) is an application of the parametric acoustic array in air, which can be applied to transmit a narrow audio beam from an ultrasonic emitter. However, nonlinear distortion is very perceptible in the audio beam. Modulation methods to reduce the nonlinear distortion are available for on-axis far-field applications. For other applications, preprocessing techniques are wanting. In order to develop a preprocessing technique with general applicability to a wide range of operating conditions, the Volterra filter is investigated as a nonlinear model of the PAL in this paper. Limitations of the standard audio-to-audio Volterra filter are elaborated. An improved ultrasound-to-ultrasound Volterra filter is proposed and empirically demonstrated to be a more generic Volterra model of the PAL.
Word-specific effects on sound change of the lexical pitch accent in Kyungsang Korean
Authors: Lee Hyunjung
Published: November 2016

This study investigated word-specific effects for the on-going sound change of the lexical pitch accent of Kyungsang Korean, arguably induced by influence from the standard Seoul Korean. This study tested whether Kyungsang speakers produced and perceived words used only in Kyungsang areas differently from the words used both in Seoul and Kyungsang areas. In production and perception experiments, Kyungsang speakers exhibited more conservative patterns for the word used only in the Kyungsang area compared to the other type of words. Implications on the sound change of the lexical pitch accent in Kyungsang Korean were discussed based on an exemplar framework.
Single and Combined Effects of Beetroot Crystals and Sodium Bicarbonate on 4-km Cycling Time Trial Performance
Authors: Callahan Marcus J. , Parr Evelyn B. , Hawley John A. , Burke Louise M.
Published: November 2016

When ingested alone, beetroot juice and sodium bicarbonate are ergogenic for high-intensity exercise performance. This study sought to determine the independent and combined effects of these supplements. Eight endurance trained (VO2max 65 mL·kg·min-1) male cyclists completed four × 4-km time trials (TT) in a doubleblind Latin square design supplementing with beetroot crystals (BC) for 3 days (15 g·day-1 + 15 g 1 h before TT, containing 300 mg nitrate per 15 g), bicarbonate (Bi 0.3 g·kg-1 body mass [BM] in 5 doses every 15 min from 2.5 h before TT); BC+Bi or placebo (PLA). Subjects completed TTs on a Velotron cycle ergometer under standardized laboratory conditions. Plasma nitrite concentrations were significantly elevated only in the BC+Bi trial before the TT (1520 ± 786 nmol·L-1) compared with baseline (665 ± 535 nmol·L-1, p = .02) and the Bi and PLA conditions (Bi: 593 ± 203 nmol·L-1, p < .01; PLA: 543 ± 369 nmol·L-1, p < .01). Plasma nitrite concentrations were not elevated in the BC trial before the TT (1102 ± 218 nmol·L-1) compared with baseline (975 ± 607 nmol·L-1, p > .05). Blood bicarbonate concentrations were increased in the BC+Bi and Bi trials before the TT (BC+Bi: 30.9 ± 2.8 mmol·L-1; Bi: 31.7 ± 1.1 mmol·L-1). There were no differences in mean power output (386–394 W) or the time taken to complete the TT (335.8–338.1 s) between any conditions. Under the conditions of this study, supplementation was not ergogenic for 4-km TT performance.
Positional Differences in External On-Field Load During Specific Drill Classifications Over a Professional Rugby League Preseason
Authors: Cummins Cloe , McLean Blake , Halaki Mark , Orr Rhonda
Published: November 2016

Purpose:

To quantify the external training loads of positional groups in preseason training drills.

Methods:

Thirty-three elite rugby league players were categorized into 1 of 4 positional groups: outside backs (n = 9), adjustables (n = 9), wide-running forwards (n = 9), and hit-up forwards (n = 6). Data for 8 preseason weeks were collected using microtechnology devices. Training drills were classified based on drill focus: speed and agility, conditioning, and generic and positional skills.

Results:

Total, high-speed, and very-high-speed distance decreased across the preseason in speed and agility (moderate, small, and small, respectively), conditioning (large, large, and small) and generic skills (large, large, and large). The duration of speed and generic skills also decreased (77% and 48%, respectively). This was matched by a concomitant increase in total distance (small), high-speed running (small), very-high-speed running (moderate), and 2-dimensional (2D) BodyLoad (small) demands in positional skills. In positional skills, hit-up forwards (1240 ± 386 m) completed less very-high-speed running than outside backs (2570 ± 1331 m) and adjustables (2121 ± 1163 m). Hit-up forwards (674 ± 253 AU) experienced greater 2D BodyLoad demands than outside backs (432 ± 230 AU, P = .034). In positional drills, hit-up forwards experienced greater relative 2D BodyLoad demands than outside backs (P = .015). Conversely, outside backs experienced greater relative high- (P = .007) and very-high-speed-running (P < .001) demands than hit-up forwards.

Conclusion:

Significant differences were observed in training loads between positional groups during positional skills but not in speed and agility, conditioning, and generic skills. This work also highlights the importance of different external-load parameters to adequately quantify workload across different positional groups.
External Match Workloads During the First Week of Australian Open Tennis Competition
Authors: Whiteside David , Reid Machar
Published: November 2016

Purpose:

With a view to informing athlete preparation leading into tournament play, this study examined external hitting and movement workloads during the first week of the 2012–2016 Australian Open tournaments.

Methods:

Using Hawk-Eye, on-court movement and stroke data were captured for 39 players (21 women, 18 men) during the first 4 rounds of singles competition. Hitting and movement workloads were compared between sexes and rounds of competition.

Results:

On average, men traversed approximately 4 km greater distance and hit 785 more shots than women hit across the first 4 rounds of the Australian Open. Women hit significantly more first serves, forehand returns, and backhand groundstrokes per game than men did. Total distance covered per game did not exhibit a significant sex effect, although men covered a significantly greater proportion of that distance at speeds greater than 3 m/s. Game-level hitting and movement workloads, and effective playing time, increased significantly between rounds 1 and 4 of the tournament in both sexes.

Conclusion:

When preparing athletes for competition, tennis practitioners should be aware that men may need to withstand aggregated hitting and movement (specifically, high-speed exertion) workloads that are 52% and up to 281% greater than women, respectively. Moreover, the evidence demonstrated that these workloads increased as players progressed deeper into the tournament. These novel insights can be used to improve the specificity of training prescription and physical-testing protocols in professional tennis.
Athlete Self-Report Measures in Research and Practice: Considerations for the Discerning Reader and Fastidious Practitioner
Authors: Saw Anna E. , Kellmann Michael , Main Luana C. , Gastin Paul B.
Published: November 2016

Athlete self-report measures (ASRM) have the potential to provide valuable insight into the training response; however, there is a disconnect between research and practice that needs to be addressed; namely, the measure or methods used in research are not always reflective of practice, or data primarily obtained from practice lacks empirical quality. This commentary reviews existing empirical measures and the psychometric properties required to be considered acceptable for research and practice. This information will allow discerning readers to make a judgment on the quality of ASRM data being reported in research papers. Fastidious practitioners and researchers are also provided with explicit guidelines for selecting and implementing an ASRM and reporting these details in research papers.
Very-Heavy Sled Training for Improving Horizontal-Force Output in Soccer Players
Authors: Morin Jean-Benoît , Petrakos George , Jiménez-Reyes Pedro , Brown Scott R. , Samozino Pierre , Cross Matt R.
Published: November 2016

Background:

Sprint running acceleration is a key feature of physical performance in team sports, and recent literature shows that the ability to generate large magnitudes of horizontal ground-reaction force and mechanical effectiveness of force application are paramount. The authors tested the hypothesis that very-heavy loaded sled sprint training would induce an improvement in horizontal-force production, via an increased effectiveness of application.

Methods:

Training-induced changes in sprint performance and mechanical outputs were computed using a field method based on velocity–time data, before and after an 8-wk protocol (16 sessions of 10- × 20-m sprints). Sixteen male amateur soccer players were assigned to either a very-heavy sled (80% body mass sled load) or a control group (unresisted sprints).

Results:

The main outcome of this pilot study is that very-heavy sled-resisted sprint training, using much greater loads than traditionally recommended, clearly increased maximal horizontal-force production compared with standard unloaded sprint training (effect size of 0.80 vs 0.20 for controls, unclear between-groups difference) and mechanical effectiveness (ie, more horizontally applied force; effect size of 0.95 vs –0.11, moderate between-groups difference). In addition, 5-m and 20-m sprint performance improvements were moderate and small for the very-heavy sled group and small and trivial for the control group, respectively.

Practical Applications:

This brief report highlights the usefulness of very-heavy sled (80% body mass) training, which may suggest value for practical improvement of mechanical effectiveness and maximal horizontal-force capabilities in soccer players and other team-sport athletes.

Results:

This study may encourage further research to confirm the usefulness of very-heavy sled in this context.
Differential Strength and Endurance Parameters of the Craniocervical and Cervicothoracic Extensors and Flexors in Healthy Individuals
Authors: O’Leary Shaun , Fagermoen Charlotte Loraas , Hasegawa Hiroyuki , Thorsen Ann-Sofi Slettevold , Van Wyk Luke
Published: November 2016

This study examined isometric strength (maximal voluntary contraction [MVC]) and endurance of cervical flexor and extensor muscles in healthy individuals at the craniocervical (CC) and cervicothoracic (CT) axes. MVC and endurance measures (time to task failure in seconds [s]) at 50% MVC were recorded in 4 directions (CC flexion, CC extension, CT flexion, and CT extension) in 20 males and 20 females, and 6 strength and endurance ratios were calculated. The findings showed that the cervical extensor muscles are not only much stronger than the flexors (1.3–2 times greater MVC), but also have greater capacity for endurance (2–2.4 times greater). While males produced significantly greater MVC recordings than females (P < .003), strength ratios (P > .06) and endurance measures (P > .11) were similar. Endurance ratios were also similar except the CT extension to CC flexion ratio, which was significantly larger in females compared with males (P = .03). These findings demonstrate that substantial but normal variation exists in strength and endurance parameters between cervical flexor and extensor muscles. This is informative to clinicians when evaluating the performance of these neck muscles or when deciding on exercise parameters (eg, load, duration) when training their performance.
Comprehensive Gait Analysis of Healthy Older Adults Who Have Undergone Long-Distance Walking
Authors: Elhadi Mustafa M.O. , Ma Christina Z. , Wong Duo W.C. , Wan Anson H.P. , Lee Winson C.C.
Published: November 2016

Many older adults do not adhere to the recommended physical activity levels. This study examines the gait changes upon long-distance walking among healthy older adults. Gait tests of 24 adults aged 65 or more were conducted at baseline and at the end of 30 and 60 min of treadmill walking. Spatial temporal, kinematic, and kinetic gait data were computed. Perceived level of exertion was evaluated for each subject. Ten subjects (group B) perceived higher exertion levels than the remaining 14 subjects (group A). After walking, group B had significant reductions in dominant-side ankle joint range of motion and power, suggesting lower-leg muscle fatigue, which appeared to be compensated by significantly increased nondominant-side knee and hip motions. These changes were not observed in group A. Differences in gait parameters between groups A and B implied that some biomechanical factors might contribute to the lack of walking of some older adults.
The Relationships Between Muscle Power and Physical Activity in Older Men With Chronic Obstructive Pulmonary Disease
Authors: Hernández María , Zambom-Ferraresi Fabrício , Cebollero Pilar , Hueto Javier , Cascante José Antonio , Antón María M.
Published: November 2016

The purpose of this study was to determine the potential relationship between muscle power of the lower extremities and the physical activity in older men with chronic obstructive pulmonary disease (COPD). Forty-four men (70.3 ± 6.7 years old) with moderate-to-severe COPD completed the 6-min walk test (6MWT), BODE (body mass index, obstruction, dyspnea, and exercise), a one-repetition maximum strength of the quadriceps femoris (1RMQF), and muscle power at 50% and 70% 1RMQF. Physical activity was measured using an accelerometer. The 6MWT was associated with muscle power at 50% 1RMQF (r = .40; P = .013) but not muscle power at 70% 1RMQF (r = .24; P = .15) or 1RMQF (r = .13; P = .44). Light-intensity activity was positively correlated with muscle power at 50% 1RMQF (r = .52; P = .001). Lower limb muscle power is associated with the 6MWT and light-intensity activities in older men with COPD.
An Exercise in Resistance: Inoculation Messaging as a Strategy for Protecting Motivation During a Monotonous and Controlling Exercise Class
Authors: Dimmock James A. , Gagné Marylène , Proud Lauren , Howle Timothy C. , Rebar Amanda L. , Jackson Ben
Published: November 2016

Sustained attention has been devoted to studying the factors that support (or thwart) individuals’ enjoyment of, interest in, and value judgments regarding their exercise activities. We employed a resistance-inducing (i.e., inoculation theory) messaging technique with the aim of protecting these desirable perceptions in the face of environmental conditions designed to undermine one’s positive exercise experiences. Autonomously motivated exercisers (N = 146, Mage = 20.57, SD = 4.02) performed a 25-min, group-based, instructor-led exercise circuit, in which the activities were deliberately monotonous, and during which the confederate instructor acted in a disinterested, unsupportive, and critical manner. Shortly before the session, participants received either a control message containing general information about the exercise class or an inoculation message containing a forewarning about potential challenges to participants’ enjoyment/interest/value perceptions during the class, as well as information about how participants might maintain positive perceptions in the face of these challenges. Despite there being no between-conditions differences in presession mood or general exercise motives, inoculated (relative to control) participants reported greater interest/enjoyment in the exercise session and higher perceptions of need support from the instructor. Perceptions of need support mediated the relationship between message condition and interest/enjoyment.
Differentiating Concussion From Intracranial Pathology in Athletes
Authors: Cripps Andrea , Livingston Scott C.
Published: November 2016

Clinical Scenario:

A cerebral concussion is a traumatically induced transient disturbance of brain function characterized by a complex pathophysiologic process and is classified as a subset of mild traumatic brain injury. The occurrence of intracranial lesions after sport-related head injury is relatively uncommon, but the possibility of serious intracranial injury (ICI) should be included in the differential diagnosis. ICIs are potentially life threatening and necessitate urgent medical management; therefore, prompt recognition and evaluation are critical to proper medical management. One of the primary objectives of the initial evaluation is to determine if the concussed athlete has an acute traumatic ICI. Athletic trainers must be able promptly recognize clinical signs and symptoms that will enable them to accurately differentiate between a concussion (ie, a closed head injury not associated with significant ICI) and an ICI. The identification of predictors of intracranial lesions is, however, relatively broad.

Focused Clinical Question:

Which clinical examination findings (ie, clinical signs and symptoms) indicate possible intracranial pathology in individuals with acute closed head injuries?
The Effectiveness of Neuromuscular Electrical Stimulation in Improving Voluntary Activation of the Quadriceps: A Critically Appraised Topic
Authors: Bremner Cody B. , Holcomb William R. , Brown Christopher D. , Perreault Melanie E.
Published: November 2016

Clinical Scenario:

Orthopedic knee conditions are regularly treated in sports-medicine clinics. Rehabilitation protocols for these conditions are often designed to address the associated quadriceps strength deficits. Despite these efforts, patients with orthopedic knee conditions often fail to completely regain their quadriceps strength. Disinhibitory modalities have recently been suggested as a clinical tool that can be used to counteract the negative effects of arthrogenic muscle inhibition, which is believed to limit the effectiveness of therapeutic exercise. Neuromuscular electrical stimulation (NMES) is commonly accepted as a strengthening modality, but its ability to simultaneously serve as a disinhibitory treatment is not as well established.

Clinical Question:

Does NMES effectively enhance quadriceps voluntary activation in patients with orthopedic knee conditions?

Summary of Key Findings:

Four randomized controlled trials (RCTs) met the inclusion criteria and were included. Of those, 1 reported statistically significant improvements in quadriceps voluntary activation in the intervention group relative to a comparison group, but the statistical significance was not true for another study consisting of the same sample of participants with a different follow-up period. One study reported a trend in the NMES group, but the between-groups differences were not statistically significant in 3 of the 4 RCTs.

Clinical Bottom Line:

Current evidence does not support the use of NMES for the purpose of enhancing quadriceps voluntary activation in patients with orthopedic knee conditions.

Strength of Recommendation:

There is level B evidence that the use of NMES alone or in conjunction with therapeutic exercise does not enhance quadriceps voluntary activation in patients with orthopedic knee conditions (eg, anterior cruciate ligament injuries, osteoarthritis, total knee arthroplasty).
The Reliability and Discriminative Ability of the Overhead Squat Test for Observational Screening of Medial Knee Displacement
Authors: Post Eric G. , Olson Matthew , Trigsted Stephanie , Hetzel Scott , Bell David R.
Published: November 2016

Context: The overhead squat test (OHS) is a functional screening exam that is used to identify high-risk movement profiles such as medial knee displacement (MKD). The reliability and discriminative ability of observational screening during the OHS to identify MKD have yet to be established. Objectives: To investigate the reliability and discriminative ability of observational screening for MKD during the OHS. Study Design: Clinical measurement, cross-sectional. Participants: 100 college students were video-recorded performing the OHS. Three certified athletic trainers classified the knee posture of each subject during the OHS on 2 different occasions using screening guidelines. Main Outcome Measures: Ratings were evaluated by calculating kappa coefficients for intra- and interrater levels of agreements. MKD was measured using motion analysis. Results: Intrarater reliability ranged from .60-.76 with an average value of .70. Interrater reliability was substantial (kappa > .60) for both observation sessions (Fleiss kappa session 1 = .69, session 2 = .70). Sensitivity ranged was .58-.83, while specificity ranged was .70-.88. The MKD group displayed significantly more displacement than the no-MKD group (P < .001). There was a moderate positive correlation (r = .48, P < .001) between knee-posture group and MKD assessed using motion analysis. Conclusion: The OHS has substantial reliability and is able to assess the presence of MKD. The OHS should be used as part of a comprehensive examination that evaluates multiple movement patterns and risk levels.
A Treatment-Based Classification Algorithm to Treat Achilles Tendinopathy: An Exploratory Case Series
Authors: Syvertson Patti , Dietz Emily , Matocha Monica , McMurray Janet , Baker Russell , Nasypany Alan , Reordan Don , Paddack Michael
Published: November 2016

Context:

Achilles tendinopathy is relatively common in both the general and athletic populations. The current gold standard for the treatment of Achilles tendinopathy is eccentric exercise, which can be painful and time consuming. While there is limited research on indirect treatment approaches, it has been proposed that tendinopathy patients do respond to indirect approaches in fewer treatments without provoking pain.

Objective:

To determine the effectiveness of using a treatment-based-classification (TBC) algorithm as a strategy for classifying and treating patients diagnosed with Achilles tendinopathy.

Participants:

11 subjects (mean age 28.0 ±15.37 y) diagnosed with Achilles tendinopathy.

Design:

Case series.

Setting:

Participants were evaluated, diagnosed, and treated at multiple clinics.

Main Outcome Measures:

Numeric Rating Scale (NRS), Disablement in the Physically Active Scale (DPA Scale), Victorian Institute of Sport Assessment–Achilles (VISA-A), Global Rating of Change (GRC), and Nirschl Phase Rating Scale were recorded to establish baseline scores and evaluate participant progress.

Results:

A repeated-measures ANOVA was conducted to analyze NRS scores from initial exam to discharge and at 1-mo follow-up. Paired t tests were analyzed to determine the effectiveness of using a TBC algorithm from initial exam to discharge on the DPA Scale and VISA-A. Descriptive statistics were evaluated to determine outcomes as reported on the GRC.

Conclusion:

The results of this case series provide evidence that using a TBC algorithm can improve function while decreasing pain and disability in Achilles tendinopathy participants.