bluuebunny/crossref_metadata_2025 huggingface dataset:
Compressor Turbine Vane Ring (PT6 Engine) Repair Development
Authors: Sourial N.
Published: March 2015

In today’s aerospace industry there is a trend, which was probably started by economic factors, to donate more time and effort establishing viable salvage repairs of high priced items. This not only creates a competitive edge for the individual who initiates the repair but also stimulates industry to utilize other conceptions or improvements of existing techniques.

This paper will deal with one such item which for some years was considered “unrepairable” due to the complexity of its design.

The compressor turbine vane ring in the PT6 Engine was selected because it is located in the heart of the engine. It is subjected to a very severe environment and damages occuring to it are a common problem in all gas turbine engines. Consequently this repair, which brings the part back to its new condition for a fraction of the replacement cost, involves a great deal of state of the art technology.
Influence of Ambient Air Pressure on Pressure-Swirl Atomization
Authors: Wang X. F. , Lefebvre A. H.
Published: March 2015

The spray characteristics of six simplex atomizers are examined in a pressure vessel using a standard light diffraction technique. Attention is focused on the effects of liquid properties, nozzle flow number, spray cone angle, and ambient air pressure on mean drop size and drop-size distribution. For all nozzles and all liquids it is found that continuous increase in air pressure above the normal atmospheric value causes the SMD to first increase up to a maximum value and then decline. An explanation for this characteristic is provided in terms of the measurement technique employed and the various competing influences on the overall atomization process. The basic effect of an increase in air pressure is to improve atomization, but this trend is opposed by contraction of the spray angle which reduces the relative velocity between the drops and the surrounding air, and also increases the possibility of droplet coalescence.
Experimental Study on Atomization of Plain Jet Injector Under High Pressure Co-Axial Air Flow
Authors: Yang Gui Xiang , Chin J. S.
Published: March 2015

An experimental study has been conducted on the effect of high back pressure on the spray characteristics of a plain jet injector under coaxial high velocity air flow. The air pressures tested range from 1 to 16 atm, the range of air velocity is 60–120 m/s, the pressure drops of injector tested are 200–2000 kpa. Working fluid is water. Injector hole diameter is 0.5 mm. The key feature of the experiment is using a convergent-divergent nozzle to maintain a high air pressure inthe test chamber and at the same time to maintain a high velocity air flow in the atomization zone. Such an experimental arrangement totally eliminates air and droplets recirculation in the test chamber and problem related to slow droplet settling in a commonly used pressurized vessel for high back pressure atomization research. The results show that SMD decreases monotonicly with the increase of back pressure or air velocity, at different air velocities, the effect of air pressure is different. The drop size distribution parameter N in Rosin-Rammler distribution decreases slightly with increase of back pressure or air velocity.
Degradation of MCrA1Y Coatings by Interdiffusion
Authors: Mazars P. , Manesse D. , Lopvet C.
Published: March 2015

Coatings such as NiCrA1Y, CoCrA1Y and FeCrA1Y are deposited by plasma spraying under partial pressure on commercial f.c.c. alloys of nickel, cobalt, and iron. The interdiffusion between coating and substrate is limited in the cases of NiCrA1Y/Ni base and CoCrA1Y/Co base. On the other hand, rapid diffusion of the aluminium into the substrate occurs in the system FeCrA1Y/Fe base.

When mixed systems MCrA1Y/M’ base are studied, an interdiffusion is usually observed between the elements M and M’ except in the case of the systems NiCrA1Y/Co base and FeCrA1Y/Co base where carbide diffusion barriers are formed.
The HF “Fluoride-Ion” Cleaning Technique for Superalloys
Authors: Pochet Louis F. , Clavel Alfred L.
Published: March 2015

Fluoride-ion cleaning, using Hydrogen Fluoride gas as the active agent, is rapidly becoming established as a cost effective method to prepare nickel and cobalt based superalloys for braze repair.

Background and comparative information on the four basic processes currently in use are discussed. The latest process using hydrogen fluoride gas directly is described in detail including the methods used for precise process control and safe handling of the HF input gas, as well as the off-gas fluoride compounds. Alloys successfully prepared for braze repair are listed. Other uses for the process and potential uses for the manufacture of new components are suggested.
Low Frequency Noise Emission From a Natural Gas Compressor Station
Authors: Sieminski Manfred , Schneider Manfred
Published: March 2015

Low Frequency Noise at Gas Turbines

A natural gas compressor station that was equipped with Hispano Suiza Turbines THM 1202 emitted high intensity noise between 20 Hz and 40 Hz, causing window vibrations and standing waves within the living rooms of a nearby residential area.

Since additional sound attenuation by increasing the volume of the exhaust silencers was impossible, further investigations were carried out to explain the mechanism of this low frequency noise emission. By changing the flame pattern inside the combustion chambers of the turbines it was possible to achieve a remarkable reduction at 31.5 Hz amounting to 15 dB. The investigation procedure leading to the final results will be the subject of this presentation.
Development of a Catalytic Combustor for Small Gas Turbines
Authors: Mori K. , Kitajima J. , Kajita S. , Ichihara S.
Published: March 2015

To reduce NOx emissions significantly, a catalytic combustor was developed. Full scale tests of catalytic combustors designed for application in Kawasaki S1A-O2 type gas trubines were conducted. The combustor consisted of a pre-combustion zone, a premixing zone, a catalytic combustion zone, and a variable geometry dilution zone. Liquefied Natural Gas (LNG) was burned in combustor rig tests and results indicated low NOx emissions and high combustion efficiencies over a wide range of air/fuel ratios and that the catalytic combustor can be applied to the engine tests.
Prediction of NO and CO Distribution in Gas Turbine Combustors
Authors: Kajita Shinichi , Matumoto Ryuichi
Published: March 2015

An experimental and numerical investigation was conducted to assess the validity of a prediction procedure of NO and CO formed in gas turbine combustors.

A premixed gas turbine combustor burning propane was used in the experimental program, and the flow, temperature and pollutants fields were measured.

The prediction procedure solves the governing conservation equations of mass, momentum, energy and chemical species simultaneously by means of finite difference solution algorithm. Two main mathematical models were employed in the procedure to represent the turbulent nature of the flow and the chemical reaction rates. For the turbulence model, the two-equation k-ε model was applied. The chemical reaction model assumed a two step reaction, and the effect of turbulence on reaction rates is taken into account by employing the modified eddy-break-up model which considers the dissipation rate of eddy and the concentrations of fuel and combustion products. The reaction rate is considered to be the smaller of the two expressions given by the Arrhenius equation and the modified eddy-break-up model. For NO formation, the extended Zeldovich mecanism was assumed. The prediction results were compared with those obtained from the corresponding expreiment.

The prediction results showed the correct overall features, but a quantitative agreement was not obtained for NO and CO concentrations.
Development of Dry Two-Stage Low-NOx Combustor for a Gas Turbine
Authors: Kuroda M. , Ishibashi Y. , Iizuka N. , Uchiyama Y. , Sato I. , Wada K. , Tokunaga K. , Hata T.
Published: March 2015

A dry two-stage low NOx combustor for a 73 MW gas turbine has been developed to meet stringent NOx limitations in Japan. This combustion system has a fuel-air control mechanism to ensure stable switching from one-stage combustion to two-stage combustion.

NOx emission is very low not only at full load but also in the entire gas turbine operating range.

The NOx characteristics have proved to be within the goal in full scale, full pressure combusion tests.

This paper outlines the development plan and describes the structure and combustion characteristics of the low NOx combustor.
Experimental Analysis of the Flow in a Two Stage Axial Compressor at Off-Design Conditions
Authors: Massardo Aristide , Satta Antonio
Published: March 2015

The experimental analysis of the flow that develops in a two stage axial flow compressor at off-design conditions is presented. The measurements are performed upstream, between and downstream of the four blade rows of the compressor. The analysis shows the off-design effects on the local conditions of the flow field. Low energy flow zones are identified, and the development of annulus boundary layer, secondary and tip clearance flows, are shown. The tip clearance flows are also present in the stator rows with various outlying conditions (stationary or rotating hub).
An Influence of the Thickness of a Laminar Sublayer and Mixing Length Model on the Skin Friction and Heat Transfer in the Boundary Layer Flow
Authors: Polkowski Janusz W.
Published: March 2015

An influence of the thickness of the laminar sub-layer and mixing length profile on skin friction and heat transfer in the incompressible boundary layer is studied. Solution of the momentum and energy equations for different algebraic expressions for the mixing length is presented. Relationships between the specific forms of Reynolds analogy and boundary conditions (temperature or heat flux) as well as the limitations of Reynolds analogy are discussed.
Development of Ceramic Hot Section Components for AGT 100 Gas Turbine
Authors: Turner D. A. , Holtman R. L.
Published: March 2015

The development of the AGT 100 gasifier turbine components in structural ceramic materials is described. Development is defined as the complete and iterative cycle from design, analysis, test, and design refinement culminating in successful demonstration of the design requirements. The components are analyzed by a linear elastic probabilistic approach, which involves finite element (3D and/or 2D) simulation of the component combined with a Weibull characterization of the brittle ceramic material strength distribution to calculate a probability of survival for the component in the operating environment. Component test failure investigation has resulted in design modifications, and an improvement in component reliability has been demonstrated. Engine testing (five hundred plus hr to date) continues to assess design/development of structural ceramics.
Stress Rupture of Ceramics: Time-Temperature Relationships
Authors: Jones David I. G.
Published: March 2015

Ceramic materials, such as Silicon Carbide and Silicon Nitride, have been considered as replacements for metals in many components of modern engines, as opportunities have arisen to make use of their unique properties. Improved production capabilities and end-product defect control have contributed to this progress, but limited information on the effect of these parameters on long term behavior, such as creep and stress rupture, may have contributed to some of the difficulties. This paper will examine the stress-rupture behavior of some ceramic materials, to demonstrate a unique relationship between the time to failure, at a given stress, and the temperature. The outcome is a single parameter combining the time to failure and temperature variables, which can allow designers to predict the useful life of ceramic components more accurately than insufficient data would otherwise allow.
Three-Dimensional Calculation of Wall Boundary Layer Flows in Turbomachines
Authors: Lindsay W. L. , Carrick H. B. , Horlock J. H.
Published: March 2015

An integral method of calculating the three-dimensional turbulent boundary layer development through the blade rows of turbomachines is described. It is based on the solution of simultaneous equations for

(i) & (ii) the growth of streamwise and cross-flow momentum thicknesses;

(iii) entrainment;

(iv) the wall shear stress;

(v) the position of maximum cross-flow.

The velocity profile of the streamwise boundary layer is assumed to be that described by Coles. The cross-flow profile is assumed to be the simple form suggested by Johnston, but modified by the effect of bounding blade surfaces, which restrict the cross-flow. The momentum equations include expressions for “force-defect” terms which are also based on secondary flow analysis.

Calculations of the flow through a set of guide vanes of low deflection show good agreement with experimental results; however, attempts to calculate flows of higher deflection are found to be less successful.
Comparison Between Empirical and Numerical Labyrinth Flow Correlations
Authors: Zimmermann H. , Wolff K. H.
Published: March 2015

An improved analytical approach for the correlation of labyrinth flow is put forward. This method modifies the standard labyrinth characteristics in a way, that the first fin has individual loss coefficients. The comparison with test results is very satisfactory for a wide range of geometries.
Electronic Trend Monitoring and Exceedance Recording Systems: A Means to Improved Turbine Engine Reliability
Authors: Moore Michael G.
Published: March 2015

Current technology has yielded engine mountable, compact microprocessor-based recording systems that can record information that will aid in maintenance planning and, thus, yield improved reliability. Among data available are:

1) Trend Recording - revealing deviations from non indicating engine performance deterioration

2) Exceedance Recording - documenting time, date, duration, and severity of exceedances for parameters such as temperature, torque, N1, N2, etc.

3) Power Ratings - power (“hit”) checks are available instantaneously and through the through the exercise of power cycle, go or no-go determination made through real time analysis of current sensor outputs against defined tolerances adjusted to density altitude.

4) Run Data - total time duration within each scale of the operating range for each engine and airframe parameter

5) Cycle Counts - start, power, life fatigue, creep life, and improper cool down cycles are tracked based upon engine manufacturer formulae

These engine recorders primarily utilize the existing engine sensors with no effect on signals to established instrument.

Current technology allows these engine recorders to be universal to many different engines, with limit thresholds entered at the factory through a computer keyboard.
Composite Mechanics for Engine Structures
Authors: Chamis Christos C.
Published: March 2015

Recent research activities/accomplishments at Lewis Research Center on composite mechanics for engine structures are reviewed in summary form. The activities mainly focused on developing procedures for the computational simulation of composite intrinsic and structural behavior. The computational simulation encompasses all aspects of composite mechanics, advanced 3-D finite element methods, damage tolerance, composite structural/dynamic response and structural tailoring/optimization.
Al capping layers for nondestructive x-ray photoelectron spectroscopy analyses of transition-metal nitride thin films
Authors: Greczynski Grzegorz , Petrov Ivan , Greene J. E. , Hultman Lars
Published: March 2015

X-ray photoelectron spectroscopy (XPS) compositional analyses of materials that have been air exposed typically require ion etching in order to remove contaminated surface layers. However, the etching step can lead to changes in sample surface and near-surface compositions due to preferential elemental sputter ejection and forward recoil implantation; this is a particular problem for metal/gas compounds and alloys such as nitrides and oxides. Here, the authors use TiN as a model system and compare XPS analysis results from three sets of polycrystalline TiN/Si(001) films deposited by reactive magnetron sputtering in a separate vacuum chamber. The films are either (1) air-exposed for ≤10 min prior to insertion into the ultrahigh-vacuum (UHV) XPS system; (2) air-exposed and subject to ion etching, using different ion energies and beam incidence angles, in the XPS chamber prior to analysis; or (3) Al-capped in-situ in the deposition system prior to air-exposure and loading into the XPS instrument. The authors show that thin, 1.5–6.0 nm, Al capping layers provide effective barriers to oxidation and contamination of TiN surfaces, thus allowing nondestructive acquisition of high-resolution core-level spectra representative of clean samples, and, hence, correct bonding assignments. The Ti 2p and N 1s satellite features, which are sensitive to ion bombardment, exhibit high intensities comparable to those obtained from single-crystal TiN/MgO(001) films grown and analyzed in-situ in a UHV XPS system and there is no indication of Al/TiN interfacial reactions. XPS-determined N/Ti concentrations acquired from Al/TiN samples agree very well with Rutherford backscattering and elastic recoil analysis results while ion-etched air-exposed samples exhibit strong N loss due to preferential resputtering. The intensities and shapes of the Ti 2p and N 1s core level signals from Al/TiN/Si(001) samples do not change following long-term (up to 70 days) exposure to ambient conditions, indicating that the thin Al capping layers provide stable surface passivation without spallation.
Automatic learning‐based beam angle selection for thoracic IMRT
Authors: Amit Guy , Purdie Thomas G. , Levinshtein Alex , Hope Andrew J. , Lindsay Patricia , Marshall Andrea , Jaffray David A. , Pekar Vladimir
Published: March 2015

Purpose:

The treatment of thoracic cancer using external beam radiation requires an optimal selection of the radiation beam directions to ensure effective coverage of the target volume and to avoid unnecessary treatment of normal healthy tissues. Intensity modulated radiation therapy (IMRT) planning is a lengthy process, which requires the planner to iterate between choosing beam angles, specifying dose–volume objectives and executing IMRT optimization. In thorax treatment planning, where there are no class solutions for beam placement, beam angle selection is performed manually, based on the planner's clinical experience. The purpose of this work is to propose and study a computationally efficient framework that utilizes machine learning to automatically select treatment beam angles. Such a framework may be helpful for reducing the overall planning workload.

Methods:

The authors introduce an automated beam selection method, based on learning the relationships between beam angles and anatomical features. Using a large set of clinically approved IMRT plans, a random forest regression algorithm is trained to map a multitude of anatomical features into an individual beam score. An optimization scheme is then built to select and adjust the beam angles, considering the learned interbeam dependencies. The validity and quality of the automatically selected beams evaluated using the manually selected beams from the corresponding clinical plans as the ground truth.

Results:

The analysis included 149 clinically approved thoracic IMRT plans. For a randomly selected test subset of 27 plans, IMRT plans were generated using automatically selected beams and compared to the clinical plans. The comparison of the predicted and the clinical beam angles demonstrated a good average correspondence between the two (angular distance 16.8° ± 10°, correlation 0.75 ± 0.2). The dose distributions of the semiautomatic and clinical plans were equivalent in terms of primary target volume coverage and organ at risk sparing and were superior over plans produced with fixed sets of common beam angles. The great majority of the automatic plans (93%) were approved as clinically acceptable by three radiation therapy specialists.

Conclusions:

The results demonstrated the feasibility of utilizing a learning‐based approach for automatic selection of beam angles in thoracic IMRT planning. The proposed method may assist in reducing the manual planning workload, while sustaining plan quality.
Feasibility and robustness of dose painting by numbers in proton therapy with contour‐driven plan optimization
Authors: Barragán A. M. , Differding S. , Janssens G. , Lee J. A. , Sterpin E.
Published: March 2015

Purpose:

To prove the ability of protons to reproduce a dose gradient that matches a dose painting by numbers (DPBN) prescription in the presence of setup and range errors, by using contours and structure‐based optimization in a commercial treatment planning system.

Methods:

For two patients with head and neck cancer, voxel‐by‐voxel prescription to the target volume (GTVPET) was calculated from 18FDG‐PET images and approximated with several discrete prescription subcontours. Treatments were planned with proton pencil beam scanning. In order to determine the optimal plan parameters to approach the DPBN prescription, the effects of the scanning pattern, number of fields, number of subcontours, and use of range shifter were separately tested on each patient. Different constant scanning grids (i.e., spot spacing = Δx = Δy = 3.5, 4, and 5 mm) and uniform energy layer separation [4 and 5 mm WED (water equivalent distance)] were analyzed versus a dynamic and automatic selection of the spots grid. The number of subcontours was increased from 3 to 11 while the number of beams was set to 3, 5, or 7. Conventional PTV‐based and robust clinical target volumes (CTV)‐based optimization strategies were considered and their robustness against range and setup errors assessed. Because of the nonuniform prescription, ensuring robustness for coverage of GTVPET inevitably leads to overdosing, which was compared for both optimization schemes.

Results:

The optimal number of subcontours ranged from 5 to 7 for both patients. All considered scanning grids achieved accurate dose painting (1% average difference between the prescribed and planned doses). PTV‐based plans led to nonrobust target coverage while robust‐optimized plans improved it considerably (differences between worst‐case CTV dose and the clinical constraint was up to 3 Gy for PTV‐based plans and did not exceed 1 Gy for robust CTV‐based plans). Also, only 15% of the points in the GTVPET (worst case) were above 5% of DPBN prescription for robust‐optimized plans, while they were more than 50% for PTV plans. Low dose to organs at risk (OARs) could be achieved for both PTV and robust‐optimized plans.

Conclusions:

DPBN in proton therapy is feasible with the use of a sufficient number subcontours, automatically generated scanning patterns, and no more than three beams are needed. Robust optimization ensured the required target coverage and minimal overdosing, while PTV‐approach led to nonrobust plans with excessive overdose. Low dose to OARs can be achieved even in the presence of a high‐dose escalation as in DPBN.
FEM design and simulation of a short, 10 MV, S‐band Linac with Monte Carlo dose simulations
Authors: Baillie Devin , Aubin J. St. , Fallone B. G. , Steciw S.
Published: March 2015

Purpose:

Current commercial 10 MV Linac waveguides are 1.5 m. The authors’ current 6 MV linear accelerator–magnetic resonance imager (Linac–MR) system fits in typical radiotherapy vaults. To allow 10 MV treatments with the Linac–MR and still fit within typical vaults, the authors design a 10 MV Linac with an accelerator waveguide of the same length (27.5 cm) as current 6 MV Linacs.

Methods:

The first design stage is to design a cavity such that a specific experimental measurement for breakdown is applicable to the cavity. This is accomplished through the use of finite element method (FEM) simulations to match published shunt impedance, Q factor, and ratio of peak to mean‐axial electric field strength from an electric breakdown study. A full waveguide is then designed and tuned in FEM simulations based on this cavity design. Electron trajectories are computed through the resulting radio frequency fields, and the waveguide geometry is modified by shifting the first coupling cavity in order to optimize the electron beam properties until the energy spread and mean energy closely match values published for an emulated 10 MV Linac. Finally, Monte Carlo dose simulations are used to compare the resulting photon beam depth dose profile and penumbra with that produced by the emulated 10 MV Linac.

Results:

The shunt impedance, Q factor, and ratio of peak to mean‐axial electric field strength are all matched to within 0.1%. A first coupling cavity shift of 1.45 mm produces an energy spectrum width of 0.347 MeV, very close to the published value for the emulated 10 MV of 0.315 MeV, and a mean energy of 10.53 MeV, nearly identical to the published 10.5 MeV for the emulated 10 MV Linac. The depth dose profile produced by their new Linac is within 1% of that produced by the emulated 10 MV spectrum for all depths greater than 1.5 cm. The penumbra produced is 11% narrower, as measured from 80% to 20% of the central axis dose.

Conclusions:

The authors have successfully designed and simulated an S‐band waveguide of length of 27.5 cm capable of producing a 10 MV photon beam. This waveguide operates well within the breakdown threshold determined for the cavity geometry used. The designed Linac produces depth dose profiles similar to those of the emulated 10 MV Linac (waveguide‐length of 1.5 m) but yields a narrower penumbra.
Growth, Maturation, and Exercise
Authors: Jürimäe Jaak
Published: March 2015

This study attempted to validate an anthropometric equation for predicting age at peak height velocity (APHV) in 193 Polish boys followed longitudinally 8-18 years (1961-1972). Actual APHV was derived with Preece-Baines Model 1. Predicted APHV was estimated at each observation using chronological age (CA), stature, mass, sitting height and estimated leg length. Mean predicted APHV increased from 8 to 18 years. Actual APHV was underestimated at younger ages and overestimated at older ages. Mean differences between predicted and actual APHV were reasonably stable between 13 and 15 years. Predicted APHV underestimated actual APHV 3 years before, was almost identical with actual age 2 years before, and then overestimated actual age through 3 years after PHV. Predicted APHV did not differ among boys of contrasting maturity status 8-11 years, but diverged among groups 12-15 years. In conclusion, predicted APHV is influenced by CA and by early and late timing of actual PHV. Predicted APHV has applicability among average maturing boys 12-16 years in contrast to late and early maturing boys. Dependence upon age and individual differences in actual APHV limits utility of predicted APHV in research with male youth athletes and in talent programs.
Aerobic Fitness and Training in Children
Authors: Armstrong Neil
Published: March 2015

Purpose:

The presence of a maturational threshold that modulates children’s physiological responses to exercise training continues to be debated, not least due to a lack of longitudinal evidence to address the question. The purpose of this study was to investigate the interaction between swim-training status and maturity in nineteen trained (T, 10 ± 1 years, −2.4 ± 1.9 years prepeak height velocity, 8 boys) and fifteen untrained (UT, 10 ± 1 years, −2.3 ± 0.9 years prepeak height velocity, 5 boys) children, at three annual measurements.

Methods:

In addition to pulmonary gas exchange measurements, stroke volume (SV) and cardiac output (Q) were estimated by thoracic bioelectrical impedance during incremental ramp exercise.

Results:

At baseline and both subsequent measurement points, trained children had significantly (p < .05) higher peak oxygen uptake (year1 T 1.75 ± 0.34 vs. UT 1.49 ± 0.22; year 2 T 2.01 ± 0.31 vs. UT 1.65 ± 0.08; year 3 T 2.07 ± 0.30 vs. UT 1.77 ± 0.16 l min−1) and Q (year 1 T 15.0 ± 2.9 vs. UT 13.2 ± 2.2; year 2 T 16.1 ± 2.8 vs. UT 13.8 ± 2.9; year 3 T 19.3 ± 4.4 vs. UT 16.0 ± 2.7 l min−1). Furthermore, the SV response pattern differed significantly with training status, demonstrating the conventional plateau in UT but a progressive increase in T. Multilevel modeling revealed that none of the measured pulmonary or cardiovascular parameters interacted with maturational status, and the magnitude of the difference between T and UT was similar, irrespective of maturational status.

Conclusion:

The results of this novel longitudinal study challenge the notion that differences in training status in young people are only evident once a maturational threshold has been exceeded.
Resistance Training in Children
Authors: Falk Bareket
Published: March 2015

Children develop lower levels of muscle force, and at slower rates, than adults. Although strength training in children is expected to reduce this differential, a synchronous adaptation in the tendon must be achieved to ensure forces continue to be transmitted to the skeleton with efficiency while minimizing the risk of strain- related tendon injury. We hypothesized that resistance training (RT) would alter tendon mechanical properties in children concomitantly with changes in force production characteristics. Twenty prepubertal children (age 8.9 ± 0.3 yr) were equally divided into control (nontraining) and experimental (training) groups. The training group completed a l0-week RT intervention consisting of 2–3 sets of 8–15 plantar flexion contractions performed twice weekly on a recumbent calf-raise machine. Achilles tendon properties (cross-sectional area, elongation, stress, strain, stiffness, and Young’s modulus), electromechanical delay (EMD; time between the onset of muscle activity and force), rate of force development (RFD; slope of the force-time curve), and rate of electromyographic (EMG) increase (REI; slope of the EMG time curve) were measured before and after RT. Tendon stiffness and Young’s modulus increased significantly after RT in the experimental group only (~29% and ~25%, respectively); all other tendon properties were not significantly altered, although there were mean decreases in both peak tendon strain and strain at a given force level (14% and 24%, respectively; not significant) which may have implications for tendon injury risk and muscle fiber mechanics. A decrease of ~13% in EMD was found after RT for the experimental group, which paralleled the increase in tendon stiffness (r = −0.59); however, RFD and REI were unchanged. The present data show that the Achilles tendon adapts to RT in prepubertal children and is paralleled by a change in EMD, although the magnitude of this change did not appear to be sufficient to influence RFD. These findings are of importance within the context of the efficiency and execution of movement.
Elite Youth Sports
Authors: Williams Craig A.
Published: March 2015

Youth sport participation offers many benefits including the development of self-esteem, peer socialization, and general fitness. However, an emphasis on competitive success—often driven by goals of elite-level travel team selection, collegiate scholarships, Olympic and National team membership, and even professional contracts—has seemingly become widespread. This has resulted in increased pressure to begin high intensity training at young ages. Such an excessive focus on early intensive training and competition at young ages rather than skill development can lead to overuse injury and burnout.
Physical Activity, Inactivity, and Health
Authors: Rowlands Alex V.
Published: March 2015

Background:

The total activity volume performed is an overall measure that takes into account the frequency, intensity, and duration of activities performed. The importance of considering total activity volume is shown by recent studies indicating that light physical activity (LPA) and intermittent moderate-to-vigorous physical activity (MVPA) have health benefits. Accelerometer-derived total activity counts (TAC) per day from a waist-worn accelerometer can serve as a proxy for an individual’s total activity volume. The purpose of this study was to develop age- and gender-specific percentiles for daily TAC, minutes of MVPA, and minutes of LPA in U.S. youth ages 6-19 y.

Methods:

Data from the 2003-2006 NHANES waist-worn accelerometer component were used in this analysis. The sample was composed of youth aged 6-19 years with at least 4 d of ≥10 hr of accelerometer wear time (N = 3698). MVPA was defined using age specific cutpoints as the total number of minutes at ≥4 metabolic equivalents (METs) for youth 6-17 y or minutes with ≥2020 counts for youth 18-19 y. LPA was defined as the total number of minutes between 100 counts and the MVPA threshold. TAC/d, MVPA, and LPA were averaged across all valid days.

Results:

For males in the 50th percentile, the median activity level was 441,431 TAC/d, with 53 min/d of MVPA and 368 min/d of LPA. The median level of activity for females was 234,322 TAC/d, with 32 min/d of MVPA and 355 min/d of LPA.

Conclusion:

Population referenced TAC/d percentiles for U.S. youth ages 6-19 y provide a novel means of characterizing the total activity volume performed by children and adolescents.
Endocrinology and Metabolism
Authors: Eliakim Alon
Published: March 2015

Introduction:

Competitive female athletes restrict energy intake and increase exercise energy expenditure frequently resulting in ovarian suppression. The purpose of this study was to determine the impact of ovarian suppression and energy deficit on swimming performance (400-m swim velocity).

Methods:

Menstrual status was determined by circulating estradiol (E2) and progesterone (P4) in ten junior elite female swimmers (15-17 yr). The athletes were categorized as cyclic (CYC) or ovarian-suppressed (OVS). They were evaluated every 2 weeks for metabolic hormones, bioenergetic parameters, and sport performance during the 12-week season.

Results:

CYC and OVS athletes were similar (p > .05) in age (CYC = 16.2 ± 1.8 yr, OVS = 17 ± 1.7 yr), body mass index (CYC = 21 ± 0.4 kg·m, OVS = 25 ± 0.8 kg·m), and gynecological age (CYC = 2.6 ± 1.1 yr, OVS = 2.8 ± 1.5 yr). OVS had suppressed P4 (p < .001) and E2 (p = .002) across the season. Total triiodothyronine (TT3) and insulin-like growth factor (IGF-1) were lower in OVS (TT3: CYC = 1.6 ± 0.2 nmol·L, OVS = 1.4 ± 0.1 nmol·L, p < .001; IGF-1: CYC = 243 ± 1 μg·mL, OVS = 214 μg·mL p < .001) than CYC at week 12. Energy intake (p < .001) and energy availability (p < .001) were significantly lower in OVS versus CYC. OVS exhibited a 9.8% decline in Δ400-m swim velocity compared with an 8.2% improvement in CYC at week 12.

Conclusions:

Ovarian steroids (P4 and E2), metabolic hormones (TT3 and IGF-1), and energy status markers (EA and EI) were highly correlated with sport performance. This study illustrates that when exercise training occurs in the presence of ovarian suppression with evidence for energy conservation (i.e., reduced TT3), it is associated with poor sport performance. These data from junior elite female athletes support the need for dietary periodization to help optimize energy intake for appropriate training adaptation and maximal sport performance
Cardiovascular Physiology and Disease in Youth
Authors: Rowland Thomas
Published: March 2015

Introduction:

Patients with repaired tetralogy of Fallot have good long-term survival but less is known about the subjectively assessed quality of life or objectively measured functional status of those who have not required subsequent pulmonary valve replacement. We assessed these parameters in a group of children and adults free from pulmonary valve replacement after tetralogy of Fallot repair.

Methods and Results:

A random sample of 50 subjects—16 children and 34 adults, aged 4.1-56.7 years—who had undergone tetralogy of Fallot repair and were free from subsequent pulmonary valve replacement underwent cardiopulmonary exercise testing and completed standardized questionnaires assessing health related quality of life and resilience. Patients were generally asymptomatic (median New York Heart Association class = 1). Exercise capacity was within two standard deviations of normal for most children and adults (mean z VO2max: 0.20 + 1.5; mean z VO2max: 0.20 + 1.5; mean z VE/VCO2 −0.9 + 1.3). Children reported a total health-related quality of life score similar to healthy norms (78 + 10 versus 84 + 1, p = .73). Adult survivors also reported quality of life scores comparable to healthy norms. Resilience was highly correlated with all domains of health-related quality of life (r = .713, p < .0001).

Conclusions:

Patients who have undergone tetralogy of Fallot repair in childhood and have not required pulmonary valve replacement have a good long-term health-related quality of life. The finding that patients with greater resilience had better health-related quality of life suggests that it may be beneficial to implement interventions to foster resilience.
Chronic Diseases, Exercise, and Physical Activity in Childhood: Off the Beaten Track
Authors: Takken Tim
Published: March 2015

The one million dollar question in our discipline might be how to get kids with chronic disease moving. Most of the current strategies are focused on children in our general population; However, children with disability are in desperate need of our attention since inactivity might be a bigger issue compared with their “healthy” peers. What we can learn (among others) from this year’s released Global Matrix on Physical Activity for Children and Youth (1), that many countries struggle to get their children moving. To get children with chronic disease or disability moving is even more challenging. In the current year, The Year That Was, I want to focus on two studies that might help us further on this topic.
The societal burden of chronic liver diseases: results from the COME study
Authors: Scalone Luciana , Fagiuoli Stefano , Ciampichini Roberta , Gardini Ivan , Bruno Raffaele , Pasulo Luisa , Lucà Maria Grazia , Fusco Francesco , Gaeta Laura , Del Prete Anna , Cesana Giancarlo , Mantovani Lorenzo Giovanni
Published: March 2015

Objective

Chronic liver diseases (CLDs) impose a significant socioeconomic burden on patients and the healthcare system, but to what extent remains underexplored. We estimated costs and health-related-quality-of-life (HRQoL) among patients with CLDs at different stages and with different aetiologies.

Design

A cost-of-illness study was conducted. Direct costs, productivity loss and HRQoL were estimated in patients with chronic hepatitis, cirrhosis hepatocellular carcinoma (HCC) or where orthotopic liver transplantation (OLT) had been performed, for hepatitis C virus (HCV) infection, hepatitis B virus (HBV) infection, or in those with liver disease from other causes. Patients were retrospectively observed for 6 months. The societal perspective was adopted to calculate costs.

Results

In total, 1088 valid patients (median age=59.5 years, 60% men) were enrolled. 61% had chronic hepatitis, 20% cirrhosis, 8% HCC and 12% underwent OLT. HCV infection was identified in 52% and HBV infection in 29% of the patients. Adjusted mean direct costs increased from <€200/patient-month in HCV-infected patients with hepatitis to >€3000/patient-month in HBV infected patients with OLT. Antiviral treatment was the cost driver in patients with hepatitis, while hospital costs were the driver in the other subgroups. Absenteeism increased from HBV-infected patients with hepatitis (0.7 day/patient-month) to patients with OLT with other aetiologies (3.7 days/patient-month). HRQoL was on average more compromised in cirrhosis and patients with HCC, than in hepatitis and patients with OLT. HBV-infected patients generated higher direct costs, patients with other aetiologies generated the highest productivity loss and HCV-infected patients reported the worst HRQoL levels.

Conclusions

The present study can be considered a benchmark for future research and to guide policies aimed at maximising the cost-effective of the interventions.
Delay Line as a Chemical Reaction Network
Authors: Moles Josh , Banda Peter , Teuscher Christof
Published: March 2015

Chemistry as an unconventional computing medium presently lacks a systematic approach to gather, store, and sort data over time. To build more complicated systems in chemistries, the ability to look at data in the past would be a valuable tool to perform complex calculations. In this paper we present the first implementation of a chemical delay line providing information storage that can reliably capture information over an extended period of time. The delay line is capable of parallel operations in a single instruction, multiple data (SIMD) fashion.

Using mass action and Michaelis-Menten kinetics, we describe the chemical delay line implementation featuring enzymes acting as a means to reduce copy errors. We also discuss how information is randomly accessible from any element on the delay line. Our work shows how the chemical delay line retains and provides a value from a previous cycle. The system's modularity allows for integration with existing chemical systems. We exemplify the delay line capabilities by integration with a threshold asymmetric signal perceptron to demonstrate how it learns all 14 linearly separable binary functions over a sliding window of size two. The delay line has applications in biomedical diagnosis and treatment, such as smart drug delivery.
Calculating Voronoi Diagrams Using Simple Chemical Reactions
Authors: De Lacy Costello Ben
Published: March 2015

This paper overviews work on the use of simple chemical reactions to calculate Voronoi diagrams and undertake other related geometric calculations. This work highlights that this type of specialised chemical processor is a model example of a parallel processor. For example increasing the complexity of the input data within a given area does not increase the computation time. These processors are also able to calculate two or more Voronoi diagrams in parallel. Due to the specific chemical reactions involved and the relative strength of reaction with the substrate (and cross-reactivity with the products) these processors are also capable of calculating Voronoi diagrams sequentially from distinct chemical inputs.

The chemical processors are capable of calculating a range of generalised Voronoi diagrams (either from circular drops of chemical or other geometric shapes made from adsorbent substrates soaked in reagent) , skeletonisation of planar shapes and weighted Voronoi diagrams (e.g., additively weighted Voronoi diagrams, Multiplicitavely weighted Crystal growth Voronoi diagrams). The paper will also discuss some limitations of these processors.

These chemical processors constitute a class of pattern forming reactions which have parallels with those observed in natural systems. It is possible that specialised chemical processors of this general type could be useful for synthesising functional structured materials.
Mechanisms Inducing Parallel Computation in a Model of Physarum polycephalum Transport Networks
Authors: Jones Jeff
Published: March 2015

The giant amoeboid organism true slime mould Physarum polycephalum dynamically adapts its body plan in response to changing environmental conditions and its protoplasmic transport network is used to distribute nutrients within the organism. These networks are efficient in terms of network length and network resilience and are parallel approximations of a range of proximity graphs and plane division problems. The complex parallel distributed computation exhibited by this simple organism has since served as an inspiration for intensive research into distributed computing and robotics within the last decade. P. polycephalum may be considered as a spatially represented parallel unconventional computing substrate, but how can this ‘computer’ be programmed? In this paper we examine and catalogue individual low-level mechanisms which may be used to induce network formation and adaptation in a multi-agent model of P. polycephalum. These mechanisms include those intrinsic to the model (particle sensor angle, rotation angle, and scaling parameters) and those mediated by the environment (stimulus location, distance, angle, concentration, engulfment and consumption of nutrients, and the presence of simulated light irradiation, repellents and obstacles). The mechanisms induce a concurrent integration of chemoattractant and chemorepellent gradients diffusing within the 2D lattice upon which the agent population resides, stimulating growth, movement, morphological adaptation and network minimisation. Chemoattractant gradients, and their modulation by the engulfment and consumption of nutrients by the model population, represent an efficient outsourcing of spatial computation. The mechanisms may prove useful in understanding the search strategies and adaptation of distributed organisms within their environment, in understanding the minimal requirements for complex adaptive behaviours, and in developing methods of spatially programming parallel unconventional computers and robotic devices.
Physarum-Inspired Applications in Graph-Optimization Problems
Authors: Zhang Xiaoge , Mahadevan Sankaran , Deng Yong
Published: March 2015

In the past decade, we have witnessed the rapid development of a increasing body of research focused on Physarum polycephalum, which has been employed to solve many complicated problems in real-world applications. In this paper, we give an overview towards the developments of Physarum-inspired models for graph-optimization problems. Specifically, we reported the applications of Physarum in the following graph-optimization problems: influential nodes identification, shortest path tree problem, biobjective shortest path problem, improved Physarum algorithm and approximating the transport network.
Hardware Acceleration of Cellular Automata Physarum polycephalum Model
Authors: Dourvas Nikolaos , Tsompanas Michail-Antisthenis , Sirakoulis Georgios Ch. , Tsalides Philippos
Published: March 2015

During the past decades, computer science experts were inspired from the study of biological organisms. Moreover, bio-inspired algorithms were produced that many times can give excellent solutions with low computational cost in complex engineering problems. In our case, the plasmodium of Physarum polycephalum is capable of finding the shortest path solution between two points in a labyrinth. In this study, we implement a Cellular Automata (CA) model in hardware, which attempts to describe and, moreover, mimic the behavior of the plasmodium in a maze. Beyond the successful implementation of the CA-based Physarum model in software, in order to take full advantage of the inherent parallelism of CA, we focus on a Field Programmable Gate Array (FPGA) implementation of the proposed model. Namely, two different implementations were considered here. Their difference is on the desired precision produced by the numerical representation of CA model parameters. Based on the corresponding results of the shortest path in the labyrinth,the modeling efficiency of both approaches was compared depending on the resulting error propagation. The presented FPGA implementations succeed to take advantage of the CA's inherit parallelism and improve the performance of the CA algorithm when compared with software in terms of computational speed and power consumption. As a result, the implementations presented here, can also be considered as a preliminary CA-based Physarum polycephalum IP core which produces a biological inspired solution to the shortest-path problem.