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TBCs for Gas Turbines under Thermomechanical Loadings： Failure Behaviour and Life Prediction

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Journal of Energy and Power Engineering 2013年第4期7卷 647-653页

作者： Tilmann Beck Olena Trunova roland herzog Lorenz Singheiser Forschungszentrum Juelich GmbH Institute of Energy and Climate Research Juelich 52425 Germany RM-Material Technology MAN Diesel & Turbo SE Oberhausen 46145 Germany

The present contribution gives an overview about recent research on a TBC (thermal barrier coating) system consisted of (1) an intermetallic MCrAlY-alloy BC (bond coat) applied by VPS (vacuum plasma spraying) and (2) an YSZ (yttria stabilised zirconia) top coat APS (air plasma sprayed) at Forschungszentrum Juelich, Institute of Energy and Climate Research (IEK-2). The influence of high temperature dwell time, maximum and minimum temperature on crack growth kinetics during thermal cycling of such plasma sprayed TBCs is investigated using scanning electron microscopy and AE (acoustic emission) analysis. Thermocyclic life in terms of accumulated time at maximum temperature decreases with increasing high temperature dwell time and increases with increasing minimum temperature. AE analysis proves that crack growth mainly occurs during cooling at temperatures below the ductile-to-brittle transition temperature of the BC. Superimposed mechanical load cycles accelerate delamination crack growth and, in case of sufficiently high mechanical loadings, result in premature fatigue failure of the substrate. A life prediction model based on TGO growth kinetics and a fracture mechanics approach has been developed which accounts for the influence of maximum and minimum temperature as well as of high temperature dwell time with good accuracy in an extremely wide parameter range.

关键词：热障涂层寿命预测失效行为机械载荷燃气轮机空气等离子喷涂氧化钇稳定氧化锆真空等离子喷涂

The secrets to running economy

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Journal of Sport and Health Science 2022年第3期11卷 273-274页

作者： Walter herzog Human Performance Laboratory Faculty of KinesiologyUniversity of CalgaryCalgaryAB T2N 1N4Canada

Every once in a while,a sport is revolutionized by a discovery or a new invention.In the mid-1980s,cross-country skiing was changed forever by the introduction of the skating technique.Dick Fosbury revolutionized high-jumping when he won the Olympic Games by crossing the bar“backwards”,and the development of the“klapp-skate”led to vast improvements of world records in speed skating.

关键词： technique. backward revolution

The Journal of Sport and Health Science:Commemorating a decade of publishing milestones and impact

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Journal of Sport and Health Science 2022年第4期11卷 415-417页

作者： Peijie Chen Walter herzog JSHS

The year 2022 marks the 10th anniversary of the Journal of Sport and Health Science(JSHS),which was launched in May 2012.The journal’s initial vision was to provide a peerreviewed,high-value,top-quality,reputable journal that would uphold the same high publication standards as other leading scientific journals dedicated to promoting excellence in the field.In just 10 years,JSHS,operating on a genuine openaccess and free-of-charge platform,has grown to become one of the most highly ranked journals in the field.In 2021,JSHS witnessed a major improvement in the journal’s Impact Factor,with a score of 13.077,placing it second among 87 journals in the Sport Sciences category;and in CiteScore,with a score of 10.8,ranking it fifth among 284 journals in the Orthopedics and Sports Medicine category(Fig.1).

关键词： journal category Sport

Does eccentric exercise stimulate sarcomerogenesis?

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Journal of Sport and Health Science 2022年第1期11卷 40-42页

作者： Walter herzog Heiliane de Brito Fontana Human Performance Laboratory Faculty of KinesiologyUniversity of CalgaryAB T2N 1N4Canada Department of Morphological Sciences School of Biological SciencesFederal University of Santa CatarinaFlorianopolis88040-900Brazil

Eccentric exercise has been associated with an increase in serial sarcomere number in some studies,1 but not in others.2 Similarly,increasing excursion of muscles resulted in sarcomerogenesis in some studies using growing animals,3 but not in others using skeletally mature animals.4 However,chronic elongation and chronic shortening appears to be a strong regulator of sarcomere number increase5,6 and decrease,5,7 respectively,in animal models.Despite an abundance of research on the regulation of sarcomerogenesis under a variety of conditions,the mechanisms underlying in series sarcomere number adaptations in skeletal muscles remain a puzzle,especially in non-invasive human studies where measurements of sarcomerogenesis following interventions have not been possible to date.

关键词： spite has exercise

Observations regarding open access publishing in hybrid journals in sport sciences

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Journal of Sport and Health Science 2023年第1期12卷 1-2页

作者： Philip X.Fuchs Tzyy-Yuang Shiang Walter herzog Department of Athletic Performance “National”Taiwan Normal UniversityTaipei 11677China Human Performance Laboratory Faculty of KinesiologyUniversity of CalgaryCalgaryAB T2N 1N4Canada

Hybrid journals are journals that provide both of 2 common publication options:(a)the traditional approach,where either institutions pay for a subscription or readers purchase individual articles(free of charge for the submitting author);and(b)open access,where articles are accessible without a subscription and free of charge for the reader(the submitting author typically pays an article processing charge).Hybrid journals earn a fixed amount of money from subscriptions,and they earn additional income from the article processing charges associated with their open access option.A hybrid journal can increase its income by publishing a greater number of open access articles.

关键词： individual income submit

Why are muscles strong, and why do they require little energy in eccentric action?

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Journal of Sport and Health Science 2018年第3期7卷 255-264页

作者： Walter herzog Human Performance Laboratory Faculty of Kinesiology University of Calgary

It is well acknowledged that muscles that are elongated while activated(i.e.,eccentric muscle action)are stronger and require less energy(per unit of force)than muscles that are shortening(i.e.,concentric contraction)or that remain at a constant length(i.e.,isometric contraction).Although the cross-bridge theory of muscle contraction provides a good explanation for the increase in force in active muscle lengthening,it does not explain the residual increase in force following active lengthening(residual force enhancement),or except with additional assumptions,the reduced metabolic requirement of muscle during and following active stretch.Aside from the cross-bridge theory,2 other primary explanations for the mechanical properties of actively stretched muscles have emerged:(1)the so-called sarcomere length nonuniformity theory and(2)the engagement of a passive structural element theory.In this article,these theories are discussed,and it is shown that the last of these—the engagement of a passive structural element in eccentric muscle action—offers a simple and complete explanation for many hitherto unexplained observations in actively lengthening muscle.Although by no means fully proven,the theory has great appeal for its simplicity and beauty,and even if over time it is shown to be wrong,it nevertheless forms a useful framework for direct hypothesis testing.

关键词： Cross-bridge theory Eccentric Force-length relationship Residual force enhancement Titin

Residual force enhancement in human skeletal muscles:A systematic review and meta-analysis

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Journal of Sport and Health Science 2022年第1期11卷 94-103页

作者： Daiani de Campos Lucas B.R.Orssatto Gabriel S.Trajano Walter herzog Heiliane de Brito Fontana Biomechanics Laboratory Federal University of Santa CatarinaFlorianopolis 88040-001Brazil Faculty of Health School of Exercise and Nutrition SciencesQueensland University of TechnologyBrisbane QLD 4030Australia Human Performance Laboratory Faculty of KinesiologyUniversity of CalgaryAB T2N 1N4Canada School of Biological Sciences Federal University of Santa CatarinaFlorianopolis 88040-900Brazil

Objective:We reviewed and appraised the existing evidence of in vivo manifestations of residual force enhancement in human skeletal muscles and assessed,through a meta-analysis,the effect of an immediate history of eccentric contraction on the subsequent torque capacity of voluntary and electrically evoked muscle contractions.Methods:Our search was conducted from database inception to May 2020.Descriptive information was extracted from,and quality was assessed for,45 studies.Meta-analyses and metaregressions were used to analyze residual torque enhancement and its dependence on the angular amplitude of the preceding eccentric contraction.Results:Procedures varied across studies with regards to muscle group tested,angular stretch amplitude,randomization of contractions,time window analyzed,and verbal command.Torque capacity in isometric(constant muscle tendon unit length and joint angle)contractions preceded by an eccentric contraction was typically greater compared to purely isometric contractions,and this effect was greater for electrically evoked muscle contractions than voluntary contractions.Residual torque enhancement differed across muscle groups for the voluntary contractions,with a significant enhancement in torque observed for the adductor pollicis,ankle dorsiflexors,ankle plantar flexors,and knee extensors,but not for the elbow and knee flexors.Meta-regressions revealed that the angular amplitude of the eccentric contraction(normalized to the respective joints full range of motion)was not associated with the residual torque enhancement observed.Conclusion:There is evidence of residual torque enhancement for most,but not all,muscle groups,and residual torque enhancement is greater for electrically evoked than for voluntary contractions.Contrary to our hypothesis,and contrary to generally accepted findings on isolated muscle preparations,residual torque enhancement in voluntary and electrically evoked contractions does not seem to depend on the angular amplitude of the preceding eccentric contraction.

关键词： Cross-bridge theory Eccentric contraction Force-length relationship Isometric force Muscle properties

Preservation of aberrant right hepatic arteries does not affect safety and oncological radicality of pancreaticoduodenectomy-own results and a systematic review of the literature

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Hepatobiliary Surgery and Nutrition 2022年第1期11卷 25-37页

作者： Cedrik Pyras Carsten Lukas Monika Janot-Matuschek Torsten herzog Andrea Tannapfel Waldemar Uhl Orlin Belyaev Department of Surgery St.Josef HospitalRuhr University BochumBochumGermany Institute of Radiology St.Josef HospitalRuhr University BochumBochumGermany Institute of Pathology Ruhr University BochumBochumGermany

Background:Aberrant right hepatic arteries(aRHA)are frequently encountered during pancreaticoduodenectomy(PD).Their effects on surgical morbidity and resection margin are still debated.This study aimed to compare the short term and long term outcomes in patients with and without aRHA.Methods:A single-center retrospective analysis of 353 consecutive PD during a 5-year period was done.The type of arterial supply was determined preoperatively by CT and confirmed at surgery.Hiatt types III-VI included some type of aRHA and comprised the study group.Hiatt types I and II were considered irrelevant for PD and used as controls.Primary endpoints were the rates of major postoperative complications and the rate of R0-resection in cases of malignant disease.Secondary endpoints included duration of surgery,postoperative stay,number of harvested lymph nodes and survival in patients with pancreatic cancer.Own results were compared to existent data using a systematic review of the literature.Results:No aRHA had to be sacrificed or reconstructed.Surgical morbidity and specific complications such as post-pancreatectomy hemorrhage(PPH),pancreatic fistula and bile leak were the same in patients with and without aRHA.There was no significant difference in operative time,blood loss,length of ICU-and hospital stay.Patients with malignancy had similar high rates of R0-resection and identical number of harvested lymph nodes.Survival of patients with pancreatic cancer was not affected by aRHA.Conclusions:aRHA may be preserved in virtually all cases of PD for resectable pancreatic head lesions without increasing surgical morbidity and without compromising oncological radicality in patients with cancer,provided the variant anatomy is being recognised on preoperative CT and a meticulous surgical technique is used.

关键词： Replaced hepatic artery accessory hepatic artery pancreatic cancer pancreatic surgery resection margin complications vascular anomalies

Eccentric vs. concentric muscle contraction： That is the question

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Journal of Sport and Health Science 2017年第2期6卷 128-129页

作者： Walter herzog Human Performance Laboratory Faculty of KinesiologyUniversity of Calgary

In their recent papers in the Journal of Sport and Health Science on hamstring injuries in sprinting,^(1,2)and their corresponding commentaries on each other's research,3,4Yu et al.and Liu et al.proposed different views of the mechanisms of muscle injuries in general,and hamstring injuries in sprinting specifically.While Yu et al.^(1,3)argued that muscle injuries are primarily,if not exclusively,caused by muscle strain magnitude in eccentric contractions,and thus hamstring injuries occur primarily

关键词：心肌收缩偏心肌肉损伤收缩应变受伤短跑