Littérature scientifique sur le sujet « Force-time metrics »
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Articles de revues sur le sujet "Force-time metrics"
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Evans, Sarah E., et Gregory Steeger. « Deployment-to-dwell metrics and supply-based force sustainment ». Journal of Defense Analytics and Logistics 2, no 1 (29 juin 2018) : 2–21. http://dx.doi.org/10.1108/jdal-05-2017-0009.
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Purpose In the present fast-paced and globalized age of war, special operations forces have a comparative advantage over conventional forces because of their small, highly-skilled units. Largely because of these characteristics, special operations forces spend a disproportionate amount of time deployed. The amount of time spent deployed affects service member’s quality of life and their level of preparedness for the full spectrum of military operations. In this paper, the authors ask the following question: How many force packages are required to sustain a deployed force package, while maintaining predetermined combat-readiness and quality-of-life standards? Design/methodology/approach The authors begin by developing standardized deployment-to-dwell metrics to assess the effects of deployments on service members’ quality of life and combat readiness. Next, they model deployment cycles using continuous time Markov chains and derive closed-form equations that relate the amount of time spent deployed versus at home station, rotation length, transition time and the total force size. Findings The expressions yield the total force size required to sustain a deployed capability. Originality/value Finally, the authors apply the method to the US Air Force Special Operations Command. This research has important implications for the force-structure logistics of any military force.
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Macdermid, Paul William, et Telmo Olazabal. « The Relationship between Stroke Metrics, Work Rate and Performance in Slalom Kayakers ». Biomechanics 2, no 1 (28 janvier 2022) : 31–43. http://dx.doi.org/10.3390/biomechanics2010005.
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The purpose of this study was to assess the relationship between work rate, stroke metrics, and performance in whitewater slalom. Twelve Spanish, nationally competitive whitewater slalom kayakers took part in a simulated competition while using an instrumented kayak paddle to record stroke metrics over a simulated race, total duration and sectional splits. Performance time was highly correlated to overall power output (r2 = 0.511, p < 0.001), where kayakers demonstrated a positive pacing strategy with power output significantly decreasing over successive sectional splits (158 ± 40, 112 ± 32 and 65 ± 33 W, p < 0.001). This resulted in an increased stroke duration (p < 0.001), time to peak force (p < 0.001), a decrease in stroke peak force (p < 0.001), and rate of peak force development (p < 0.001) over elapsed time. As such, work rate is deemed an objective metric to monitor performance, prescribe training, and ascertain optimal pacing strategies in canoe slalom.
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Merrigan, Justin J., Jason D. Stone, W. Guy Hornsby et Joshua A. Hagen. « Identifying Reliable and Relatable Force–Time Metrics in Athletes—Considerations for the Isometric Mid-Thigh Pull and Countermovement Jump ». Sports 9, no 1 (31 décembre 2020) : 4. http://dx.doi.org/10.3390/sports9010004.
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The purpose of this study was to evaluate intrasession reliability of countermovement jump (CMJ) and isometric mid-thigh pull (IMTP) force–time characteristics, as well as relationships between CMJ and IMTP metrics. Division I sport and club athletes (n = 112) completed two maximal effort CMJ and IMTP trials, in that order, on force plates. Relative and absolute reliability were assessed using intraclass correlation coefficients (ICCs) > 0.80 and coefficients of variation (CVs) < 10%. Intrasession reliability was acceptable for the majority of the CMJ force–time metrics except for concentric rate of force development (RFD), eccentric impulse and RFD, and lower limb stiffness. The IMTP’s time to peak force, instantaneous force at 150 ms, instantaneous net force, and RFD measures were not reliable. Statistically significant weak to moderate relationships (r = 0.20–0.46) existed between allometrically scaled CMJ and IMTP metrics, with the exception of CMJ eccentric mean power not being related with IMTP performances. A majority of CMJ and IMTP metrics met acceptable reliability standards, except RFD measures which should be used with caution. Provided CMJs and IMTPs are indicative of distinct physical fitness capabilities, it is suggested to monitor athlete performance in both tests via changes in those variables that demonstrate the greatest degree of reliability.
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Philipp, Nicolas M., Dimitrije Cabarkapa, Ramsey M. Nijem et Andrew C. Fry. « Changes in countermovement jump force-time characteristic in elite male basketball players : A season-long analyses ». PLOS ONE 18, no 9 (27 septembre 2023) : e0286581. http://dx.doi.org/10.1371/journal.pone.0286581.
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Basketball is a sport that is characterized by various physical performance parameters and motor abilities such as speed, strength, and endurance, which are all underpinned by an athlete’s efficient use of the stretch-shortening cycle (SSC). A common assessment to measure SSC efficiency is the countermovement jump (CMJ). When performed on a force plate, a plethora of different force-time metrics may be gleaned from the jump task, reflecting neuromuscular performance characteristics. The aim of this study was to investigate how different CMJ force-time characteristics change across different parts of the athletic year, within a sample of elite collegiate male basketball players. Twelve basketball players performed CMJ’s on near-weekly basis, combining for a total of 219 screenings. The span of testing was broken down into four periods: pre-season, non-conference competitive period, conference competitive period, and post-season competitive period. Results suggest that basketball players were able to experience improvements and maintenance of performance with regards to various force-time metrics, transitioning from the pre-season period into respective later phases of the in-season period. A common theme was a significant improvement between the pre-season period and the non-conference period. Various force-time metrics were subject to change, while outcome metrics such as jump height remained unchanged, suggesting that practitioners are encouraged to more closely monitor how different force-time characteristics change over extended periods of time.
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Petrovic, Milos, Dimitrije Cabarkapa, Jelena Aleksic, Damjana V. Cabarkapa, Jorgelina Ramos, Thrainn Hafsteinsson et Thordis Gisladottir. « Sex-Specific Differences in Vertical Jump Force–Time Metrics in Youth Basketball Players ». Biomechanics 4, no 4 (23 décembre 2024) : 805–11. https://doi.org/10.3390/biomechanics4040059.
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Objective: The purpose of this study was to investigate differences in countermovement jump (CMJ) force–time metrics between male and female youth basketball players. Methods: Twenty-two female and seventeen male basketball players (ages 12–16) performed CMJs on a portable force plate system (VALD Performance). The data collected were analyzed for differences in force–time characteristics, specifically during the concentric and eccentric phases of the CMJ. Results: The results showed no statistically significant differences in anthropometric characteristics between the sexes. However, male athletes demonstrated better performance in several force–time metrics during the concentric phase of the CMJ, including concentric impulse, peak velocity, and mean power, ultimately leading to higher vertical jump heights. Sex-specific differences in the eccentric phase were less pronounced, though males exhibited greater relative eccentric mean power. Conclusions: The findings suggest that male players tend to display greater force and power-producing capabilities during the propulsive (concentric) phase of the CMJ. These differences highlight the importance of tailoring training programs to address specific needs, particularly focusing on enhancing concentric force and power production in female basketball players.
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Cabarkapa, Damjana V., Dimitrije Cabarkapa, Shay M. Whiting et Andrew C. Fry. « Fatigue-Induced Neuromuscular Performance Changes in Professional Male Volleyball Players ». Sports 11, no 6 (16 juin 2023) : 120. http://dx.doi.org/10.3390/sports11060120.
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The purpose of the present study was to assess pre-post practice changes in countermovement vertical jump (CVJ) force-time metrics and to determine the relationship between internal and external load variables within a cohort of professional male volleyball players. Ten elite athletes competing in one of the top professional European leagues participated in the present study. While standing on a uni-axial force plate, each athlete performed three CVJs immediately prior to the regular training session. Each athlete wore an inertial measurement unit (VertTM) through an entire practice from which the following external load metrics were obtained: Stress (i.e., an algorithm-derived metric used to quantify the percentage of high-impact movements), Jumps (i.e., the total number of jumps performed during the practice session), and Active Minutes (i.e., the total amount of time performing dynamic movements). Immediately post-practice, each athlete completed another set of three CVJs and reported their subjective measure of internal load using a Rating of Perceived Exertion (RPE) scale (Borg CR-10). While no statistically significant differences were observed in any of the force-time metrics examined in the present study pre-post practice (e.g., eccentric and concentric peak and mean force and power, vertical jump height, contraction time, countermovement depth), our findings indicate a strong positive association between RPE and Stress (r = 0.713) and RPE and Jumps (r = 0.671). However, a weak non-statistically significant correlation was observed between RPE and Active Minutes (r = −0.038), indicating that internal load seems to be more dependent on the intensity rather than the duration of the training session for this sport.
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Shen, Zhongmin. « Finsler Metrics with K = 0 and S = 0 ». Canadian Journal of Mathematics 55, no 1 (1 février 2003) : 112–32. http://dx.doi.org/10.4153/cjm-2003-005-6.
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AbstractIn the paper, we study the shortest time problem on a Riemannian space with an external force. We show that such problem can be converted to a shortest path problem on a Randers space. By choosing an appropriate external force on the Euclidean space, we obtain a non-trivial Randers metric of zero flag curvature. We also show that any positively complete Randers metric with zero flag curvature must be locally Minkowskian.
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Cabarkapa, Damjana V., Dimitrije Cabarkapa, Nicolas M. Philipp et Andrew C. Fry. « Competitive Season-Long Changes in Countermovement Vertical Jump Force-Time Metrics in Female Volleyball Players ». Journal of Strength and Conditioning Research 38, no 2 (février 2024) : e72-e77. http://dx.doi.org/10.1519/jsc.0000000000004713.
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Abstract Cabarkapa, DV, Cabarkapa, D, Philipp, NM, and Fry, AC. Competitive season-long changes in countermovement vertical jump force-time metrics in female volleyball players. J Strength Cond Res 38(2): e72–e77, 2024—Although force plates remain one of the most widely used tools for neuromuscular performance assessment in applied sports-specific settings, there is still a lack of scientific literature focused on studying changes in countermovement vertical jump (CVJ) performance in team sports such as volleyball, especially within the female athlete population. Thus, the purpose of the present study was to examine season-long neuromuscular performance changes in volleyball players. Eighteen National Association of Intercollegiate Athletics Division-I collegiate female athletes performed 3 maximal-effort CVJs while standing on a uniaxial force plate system sampling at 1,000 Hz at 5 different testing timepoints throughout a competitive season span (∼11 weeks). The testing sessions were separated 2–3 weeks apart and performed at the approximately same time of the day (12:00 hours). Repeated-measures analysis of variance revealed that both concentric and eccentric force-time metrics remain relatively unchanged throughout a regular season span (e.g., concentric peak force and power, eccentric impulse and duration). However, the eccentric metrics such as peak and mean power and peak velocity displayed a slight improvement after a brief tapering period purposely implemented before the post-season competition to optimize the athlete's recovery (∼15, 18, and 14% increase, respectively). In addition, the outcome metrics such as vertical jump height and reactive strength index-modified did not display notable fluctuations across the competitive season span. These findings can help coaches, sports scientists, and strength and conditioning practitioners to obtain a deeper insight into collegiate female athletes' force-time characteristics that may aid with developing adequate training regimens targeted toward optimizing on-court performance.
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Merrigan, Justin J., Jason D. Stone, Joel R. Martin, William Guy Hornsby, Scott M. Galster et Joshua A. Hagen. « Applying Force Plate Technology to Inform Human Performance Programming in Tactical Populations ». Applied Sciences 11, no 14 (16 juillet 2021) : 6538. http://dx.doi.org/10.3390/app11146538.
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Force plate assessments, such as countermovement jumps and isometric mid-thigh pulls, examine performances (e.g., jump height, force, power) and movement strategies (e.g., asymmetries, durations), and are best suited to characterize and monitor physical capabilities, not predict injuries. To begin applying force plate technologies, users must first; (1) develop a data management plan to visualize and capture data over time; (2) select appropriate force plates for their scenario; (3) design appropriate testing protocols to ensure valid and reliable data. Force plate assessments may be added to existing testing, serve as separate testing batteries for annual profile testing to compare individuals and understand initial physical capabilities, or for more frequent testing (i.e., monthly or weekly) to monitor training-related adaptations or neuromuscular fatigue. Although these assessments inform evidence-based program designs, human performance practitioners must understand the considerations for conducting appropriate force plate testing, as well as proper visualizations and management of force plate data. Thus, the aim of this review is to provide evidence-based practices for utilizing force plates in tactical populations (e.g., military, firefighters, police). This includes best practices to implement testing for performance profiling, training adaptations, and monitoring neuromuscular fatigue and force asymmetries. Of note, due to the large amount of force-time metrics to choose from, this article provides general examples of important metrics to monitor and training recommendations based on changes to these force-time metrics, followed by specific examples in three case studies.
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Philipp, Nicolas, Dimitrije Cabarkapa, Drake Eserhaut, Damjana Cabarkapa et Andrew Fry. « COUNTERMOVEMENT JUMP FORCE-TIME METRICS AND MAXIMAL HORIZONTAL DECELERATION PERFORMANCE IN PROFESSIONAL MALE BASKETBALL PLAYERS ». Journal of Applied Sports Sciences 2, no 2022 (20 décembre 2022) : 11–27. http://dx.doi.org/10.37393/jass.2022.02.2.
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Basketball is a sport that relies heavily on an athlete’s ability to rapidly decelerate in order to change direction, avoid a defender, or create space. Recent literature has proposed novel ways of measuring maximal horizontal deceleration using radar technology. The aim of this study was to investigate the relationships between different countermovement jump (CMJ) force-time characteristics and metrics related to maximal horizontal deceleration for a sample of professional male basketball players. To gain further insight into performance qualities that influence horizontal deceleration performance, athletes were separated into high- and low-performance groups for all horizontal deceleration metrics, using a median split analysis, and differences in CMJ force-time metrics were investigated between groups. The results revealed no significant correlations between any CMJ force-time metrics and horizontal deceleration performance. However, athletes’ height and body mass were correlated with different deceleration performance measures, such as average deceleration, horizontal deceleration impulse, and time to stop. Higher performing athletes with regards to average horizontal deceleration and horizontal braking impulse relative to body mass generated greater concentric power (effect size (ES) = 1.04, ES = 0.86) and concentric velocities (ES = 1.17, ES = 0.97), as well as greater jump heights (ES = 1.19, ES = 0.99). Reactive Strength Index modified values were also greater in the higher performing group for horizontal braking impulse relative to body mass (ES = 1.06). On the other hand, higher-performing athletes with regard to horizontal braking impulse generated greater eccentric deceleration force (ES = 0.81) and eccentric power values (ES = 0.88) in the CMJ. Findings may be of interest to practitioners physically preparing basketball players for the sport-specific deceleration actions they may encounter.
Thèses sur le sujet "Force-time metrics"
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Hauser, John. « Metrics Thermostat ». 2001. http://hdl.handle.net/1721.1/3960.
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The explosion of information and information technology has led many firms to evolve a dispersed product development process with people and organizations spread throughout the world. To coordinate such dispersed processes managers attempt to establish a culture that implicitly rewards product development teams based on their ability to perform against a set of strategic metrics such as customer satisfaction, time to market, defect reduction, or platform reuse. Many papers have focused on selecting the right metrics and establishing the culture. In this paper we focus on a practical method to fine-tune a firm's relative emphasis on the metrics that they have chosen. In particular, we seek to advise a firm whether to increase or decrease their emphasis on each metric such that the change in emphasis improves profits. Using a thermostat analogy we apply an adaptive control feedback mechanism in which we estimate the incremental improvements in priorities that will increase profits. Iterations of adaptive control seek to maximize profits even if the environment is changing. We demonstrate the metric thermostat’s use in an application to a firm with over $20 billion in revenue. In developing the metric thermostat we recognize that there are hundreds of detailed actions, such as the use of the house of quality and the use of robust design, among which the product development team must choose. We also recognize that they will act in their own best interests to choose the actions that maximize their own implicit rewards as determined by the metrics. Management need not observe or dictate these detailed actions, but rather control the process by establishing the culture that sets the implicit weights on the metrics. The thermostat works by changing those implicit weights. We define the problem, introduce the adaptive control mechanism, modify “agency” theory to deal with incremental changes about an operating point, and derive methods that are practical and robust in light of the data that firms have available. Our methods include statistical estimation and internal surveys. The mathematics identify the critical few parameters that need be determined and highlight how to estimate them. Both the measures and the estimation are illustrated in our initial application to a large officeequipment firm. The metrics thermostat suggests that this firm has about the right emphasis on timeto- market, but has overshot on platform reuse and has lost its focus on customer satisfaction. We describe how the firm reacted to the recommendations and changed its organization. We describe additional ongoing applications with the US Air Force, the US Navy, and a major automobile and truck manufacturer.This research was funded by the Center for Innovation in Product Development (CIPD) and the International Center for Research on the Management of Technology (ICRMOT), M.I.T.
Livres sur le sujet "Force-time metrics"
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The Action as Natural Force and the Origin of Time, Space, Dimensions, Natural Forces, and Laws of Logics, Geometry and Physics at the Origination of the World. Cayenne : Werner Landgraf, 2011.
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Die Wirkung als Naturkraft und die Herkunft von Zeit, Raum, Dimensionen, Naturkräften, und Gesetzen von Logik, Geometrie und Physik bei der Entstehung der Welt. Cayenne : Werner Landgraf, 2011.
Trouver le texte intégralChapitres de livres sur le sujet "Force-time metrics"
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Kelly, Ashley Scott, et Xiaoxuan Lu. « Western Alternative Development and Chinese Development ». Dans Critical Landscape Planning during the Belt and Road Initiative, 127–58. Singapore : Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-4067-4_6.
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AbstractThis chapter, Western alternative development and Chinese development, presents two strategic planning proposals that are generated from frictions between rural development as construed by western aid agencies and forms of Chinese aid, especially regarding the speed of development and their cache of neoliberal ideologies. These programs dominated northern Laos in the 1990s and 2000s and have resulted in a patchwork landscape of development assistance and foreign investment. One featured strategic planning proposal references these earlier programs in Laos’s Muang Sing valley to help guide a strategy for basin-scale agricultural pollution remediation and increased water security, while the other proposal traces the legacies of opium’s replacement, primarily via Chinese investment, with rubber in northern Laos and the how the resultant patchwork of rubber, subsistence and cash crops, and ethnic diversity might deal with increasing rural–urban migration and significant associated strain on the rural agricultural labor force. These proposals exhibit the difficult balancing act between participating in the language and valuation metrics of development but with design concepts and approaches that actively resist easy constitution or reduction. The emphasis of alternative development on livelihood security, environmental sustainability and social development may be commendable, but the building of social capital takes time.
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Moskovitz, Elad, et Adir Even. « The Impact of a BI-Supported Performance Measurement System on a Public Police Force ». Dans Police Science, 509–27. IGI Global, 2019. http://dx.doi.org/10.4018/978-1-5225-7672-3.ch025.
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Performance measurement, as an effective tool for implementing organizational strategy and assisting ongoing control and surveillance, is broadly adopted today. The performance measurement system (PMS) explored in this case study was implemented, using business intelligence (BI) technologies, for a public police force. The system lets police commanders view and analyze the performance scores of their own units and get feedback on the success of their activities. The study examines the system's impact, through analysis of the metric results over a time period of five years. The results show that the vast majority of the metrics examined indeed improved. Further, the results underscore the moderation effect of relative metrics weights, as well as the different behavior of metrics that reflect activity versus those that reflect outcomes. The study underscores both the positive and the negative aspects of those results, and discusses their implications for future PMS implementation with BI technologies.
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Sameer Babu, M., Naresh Babu Karunakaran, P. Selvakumar, R. Sethumadhavan et Pankaj Singh Chandel. « The Role of Chatbots in Educational Leadership ». Dans Chatbots in Educational Leadership and Management, 321–46. IGI Global, 2025. https://doi.org/10.4018/979-8-3693-8734-4.ch013.
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In recent years, the integration of chatbots into the education sector has emerged as a transformative force, redefining how educational institutions approach both leadership and learning. Their potential to revolutionize education is grounded in their ability to provide real-time support, personalized learning experiences, and streamlined administrative functions, ultimately leading to more dynamic and responsive educational practices.The application of chatbots in education serves as a catalyst for enhanced leadership by streamlining communication channels between educators, students, and administrators. Traditional methods of managing educational tasks and responding to inquiries can often be cumbersome and slow. Chatbots can address this issue by offering instant, automated responses to frequently asked questions. For educational leaders, chatbots represent a tool that can improve operational efficiency, enabling them to better allocate resources, monitor performance metrics, and implement data-driven decision-making processes.
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Kerstein, Robert B. « Disclusion Time Reduction (DTR) With the Synchronized T-Scan 10/BioEMG III Technologies to Treat Chronic Muscular Temporomandibular Disorder (TMD) ». Dans Advances in Medical Technologies and Clinical Practice, 1107–376. IGI Global, 2024. https://doi.org/10.4018/978-1-6684-9313-7.ch010.
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This chapter discusses chronic Occluso-Muscle Disorder, which is a myogenous subset of Temporomandibular Disorder (TMD) symptoms resultant from occlusally activated muscle hyperactivity. It also describes the computer-guided Occluso-Muscle Disorder treatment known as Disclusion Time Reduction (DTR), that studies since the early 1990s and continuing up to the present day, repeatedly show reduces many common muscular Temporomandibular Disorder symptoms. T-Scan I-based research determined that a significant etiologic component of Occluso-Muscle Disorder is prolonged (in time) posterior occlusal surface contact shared between opposing occluding teeth during mandibular excursions. This phenomenon, known as excursive friction, occurs in both normal chewing function and during parafunction, and results in prolonged pulpal flexure and prolonged compressions of the periodontal ligament (PDL) fibers of the involved teeth, which together neuroanatomically trigger excess muscle contractions to occur within the masticatory muscles and the muscles associated with swallowing. It is this unique peripheral nervous system (PNS) posterior tooth reflex arc that incites and perpetuates chronic muscular TMD symptomatology, that can be readily resolved in patients that meet the diagnostic criteria for DTR candidacy, using the Immediate Complete Anterior Guidance Development (ICAGD) coronoplasty. ICAGD is a measured occlusal adjustment procedure that is distinctly different from unmeasured Occlusal Equilibration, in that ICAGD requires time and force-based metrics to determine that optimum occlusal adjustment outcomes were met. And importantly, ICAGD is performed in the maximum intercuspal position (MIP) without requiring bimanual manipulation to centric relation, pre-treatment splints, deprogrammers, appliances, orthotics, TENS, or any mandibular repositioning to obtain therapeutic efficacy. The Specific Aims of this chapter are to describe in detail the unique posterior tooth neuroanatomy that is etiologic for muscular Temporomandibular symptoms, explain the Disclusion Time Reduction patient candidacy criteria; outline the ICAGD protocol and the needed treatment appointment sequencing, illustrate a few differing DTR clinical cases, and highlight some of the newest Disclusion Time Reduction therapy (DTR) research with natural teeth and dental implants that supports the clinical implementation of this highly effective, digitally measured occlusal treatment for many chronic muscular TMD symptoms.
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Riess Jones, Mari. « Learning Time Patterns ». Dans Time Will Tell, 206–27. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780190618216.003.0010.
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This chapter is important in that it lays a foundation for claims throughout this book that entrainment serves a platform for learning. In this chapter, this idea is developed in the context of learning categories of meter (e.g., duple meter vs. triple meter). The key difference is that entrainment depends on coupling parameters supplied by external driving rhythm force, whereas learning depends on a binding parameter which is strengthened simply by repeated synchronous activity of two or more oscillations. Against a backdrop of evidence indicating that musicians especially possess skill in recognizing metric categories, this chapter develops the coupling–binding distinction with the aim of showing that what people learn when exposed to metrical time patterns are global attractors instilled by learning a variety of different instances in a given metric category.
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Joshi, Pankaj S. « Singularities in general relativity ». Dans Global Aspects in Gravitation and Cosmology, 157–80. Oxford University PressOxford, 1994. http://dx.doi.org/10.1093/oso/9780198539667.003.0005.
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Abstract In this chapter, we consider the question of nature and existence of spacetime singularities in the general theory of relativity. After Einstein proposed the general theory describing the gravitational force in terms of space-time curvature and proposed the field equations relating the geometry and matter content of the space-time manifold, the earliest solutions found for the field equations were the Schwarzschild metric representing the gravitational field around an isolated body such as a spherically symmetric star, and the Friedmann cosmological models. Each of these solutions contained a space-time singularity where the curvatures and densities were infinite and the physical description would break down.
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Steane, Andrew M. « Life in a rotating world ». Dans Relativity Made Relatively Easy Volume 2, 32–39. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780192895646.003.0004.
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We imagine a group of people living on the inner surface of a huge rotating cylinder in flat spacetime. Their experiences are described and calculated. Thus we introduce gravimagnetic effects and the connection between gravitational time dilation and gravitational acceleration. Gravimagnetic effects such as the force on moving particles and the precession of gyroscopes are derived. The Thomas precession is obtained. These observations illustrate GR ideas that are applicable more generally. Some properties of the general stationary metric are introduced.
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Searle, Mike. « The Day the Earth Shook : The Sumatra–Andaman Earthquake 2004 ». Dans Colliding Continents. Oxford University Press, 2013. http://dx.doi.org/10.1093/oso/9780199653003.003.0018.
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At 00.58 GMT (7.58 local time) on Sunday, 26 December 2004 a massive earthquake occurred off the north-west coast of Sumatra. The earthquake measured between magnitude 9.0 and 9.3 on the Richter scale with its epicentre at 3.32oN, 95.85oE, and occurred at a depth of approximately 30 kilometres. It was the second largest earthquake recorded since instrumental records began and was the deadliest natural disaster in recorded history. The earthquake and the resulting tsunami are estimated to have killed at least 228,000 people across fifteen countries bordering the Indian Ocean. The worst affected countries were Indonesia, Sri Lanka, India, Thailand, Burma, the Maldives, and Somalia. The earthquake occurred on the subduction zone interface between the down-going Indian Ocean plate and the overriding Burma–Andaman–Sumatra plate. It ruptured approximately 1600 kilometres’ length of the plate boundary from Sumatra all the way north to the Burmese coast, travelling at 2–3 kilometres per second. Aftershocks continued unrelentingly for over four months after the earthquake, several reaching magnitude 7.5 as far north as the northern Andaman Islands. The seismic waves indicated a thrust fault earthquake that tilted the surface up to the south-west and down to the north-east. The ground surface was elevated as much as 11 metres at the epicentre, with the tilted surface sinking up to one metre further to the north-east, offshore Sumatra. During the rupture, the Burma plate slipped as much as 15 metres horizontally as the Indian Ocean plate slipped beneath. The force of the quake perceptibly shifted the Earth’s axis, raised sea level globally and speeded Earth’s rotation. It has been suggested that the earthquake shortened the length of the day by 2.68 microseconds, because of the decrease in oblateness of the Earth. The earthquake caused the Earth to wobble on its axis by up to 2.5 cm in the direction of 145o east longitude. The natural ‘Chandler wobble’, a small motion in the Earth’s axis of rotation (the motion that occurs when the spinning object is not a perfect sphere) can be up to 9 metres over 433 days, so this eventually offsets the comparatively minor wobble produced by the earthquake.
Actes de conférences sur le sujet "Force-time metrics"
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Schmidt, Sven, Daniel Greiwe et Tim Jusko. « Pilots' Gaze Behavior During Simulated Helicopter Air-to-Air Refueling ». Dans Vertical Flight Society 80th Annual Forum & Technology Display, 1–16. The Vertical Flight Society, 2024. http://dx.doi.org/10.4050/f-0080-2024-1294.
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Refueling mid air is considered as important force multiplier for e.g. conducting search and rescue operations. Due to close proximity to the tanker, the refueling hose and drogue as well as the receiver can be strongly affected by the tanker's wake. Thus, the refueling drogue extended from the tanker by a hose is often oscillating from turbulence. Contact with the tanker has to be established by positioning the receiver's refueling probe within the tanker's drogue. During qualification training pilots are instructed to not focus on the drogue, due to its oscillations. This is done since chasing the drogue often leads to over-controlling and therefore mostly to a failed contact attempt. The presented research aims for improving today's Helicopter Air-to-Air Refueling (HAAR) as well as related training efficiency by a gain of understanding in this phenomenon. Therefore, the HAAR real-time simulation scenario at German Aerospace Center's (DLR) Air Vehicle Simulator (AVES) was extended with a multi body hose and a probe/drogue contact model to enable realistic contact initiation. During a piloted campaign, a total of six pilots with different levels of HAAR experience conducted the maneuver. This paper presents an analysis of obtained eye tracking data with regards to gaze entropy, total fixation duration on defined areas of interest and corresponding time history of control inputs. Potential links between gaze entropy and perceived workload that might be observed in the data are also discussed. Results show that the metrics can highlight differences in successful and unsuccessful attempts for contact of HAAR experienced and inexperienced pilots.
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DeVogel, Nicholas, Anjishnu Banerjee, Frank A. Pintar et Narayan Yoganandan. « Ranking of Biomechanical Metrics to Describe Human Response to Impact-Induced Damage ». Dans ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-88007.
Texte intégralRésumé :
Determination of human tolerance to impact-induced damage or injury is needed to assess and improve safety in military, automotive, and sport environments. Impact biomechanics experiments using post mortem human surrogates (PMHS) are routinely used to this objective. Risk curves representing the damage of the tested components of the PMHS are developed using the metrics gathered from the experimental process. To determine the metric that best explains the underlying response to the observed damage, statistical analysis is required of all the output response metrics (such as peak force to injury) along with the examination of potential covariates. This is conducted by parametric survival analysis. The objective of this study is to present a robust statistical methodology that can be effectively used to achieve these goals by choosing the best metric explaining injury and provide a ranking of the metrics. Previously published data from foot-ankle-lower leg experiments were used with two possible forms of censoring: right and left censoring or right and exact censoring, representing the no injury and injury data points in a different manner. The statistical process and scoring scheme were based on the predictive ability assessed by the Brier Score Metric (BSM) which was used to rank the metrics. Response metrics were force, time to peak, and rate. The analysis showed that BSM is effective in incorporating different covariates: age, posture, stature, device used to deliver the impact load, and the personal protective equipment (PPE), i.e., military boot. The BSM-based analysis indicated that the peak force was the highest ranked metric for the exact censoring scheme and the age was a significant covariate, and that peak force was also the highest ranked metric for the left censored scheme and the PPE covariate was statistically significant. IRCs are presented for the best metric.
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Huynh, Dan, J. Josiah Steckenrider et Gregory Freisinger. « Probabilistic Estimation of Posture Metrics Using Novel Loadsols ». Dans ASME 2021 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/imece2021-69409.
Texte intégralRésumé :
Abstract This paper presents an original technique for estimating human posture metrics using Novel Loadsols®. Under the proposed technique, center of pressure (COP) metrics are derived by combining physics- and data-driven estimates to achieve reasonably high accuracy at relatively low cost. To develop a training set upon which the probabilistic data model was constructed, 79 trials were conducted in which participants stood comfortably still for 30 seconds at a time simultaneously on a force plate and a pair of Loadsols, where the force plate is considered to be the gold-standard of COP measurement. These data were then used to generate Gaussian mixture models (GMMs) of pairwise combinations of force plate and Loadsol metrics. The GMMs can then be conditioned on Loadsol measurements and fused using Bayesian inference. When the training set was re-processed by converting 12 Loadsol metrics into estimated force plate metrics, it was found that the converted metrics matched ground-truth more accurately on average than raw Loadsol metrics. Furthermore, there was improvement in the r2 values of the regression lines after conversion for 75% of the metrics. Given some experiment and algorithm refinement, the proposed probabilistic approach has potential to offer the accuracy of force plate COP estimation at a fraction of the cost.
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Nguyen, Son Hai, et David Chelidze. « Characteristic Lengths and Distances : Fast and Robust Features for Nonlinear Time Series ». Dans ASME 2012 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/detc2012-71281.
Texte intégralRésumé :
Estimation of most of the metrics used to characterize dynamical systems’ output require fairly long time series (e.g., Lyapunov Exponents, Fractal Dimensions), or substantial computational resources (e.g., phase space warping metrics, sensitivity vector fields). In many practical applications, when there is abundance of data (e.g., in Atomic Force Microscopy) fast and simple features are needed, and when there is sparsity of data (e.g., in many Structural Health Monitoring situations) robust features are needed. Here, we propose a new class of features based on Birkhoff Ergodic Theorem, which are fast to calculate and do not require large data or computational resources. Applications of these metrics, in conjunction with the smooth orthogonal decomposition, to identifying underlying processes causing nonstationarity both in simulations and actual experiments are demonstrated.
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Chirvi, Sajal, Frank A. Pintar et Narayan Yoganandan. « An Examination of Isolated and Interaction-Based Biomechanical Metrics for Potential Lower Neck Injury Criteria ». Dans ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-52108.
Texte intégralRésumé :
Lower neck injuries inferior to C4 level, such as fractures and dislocations, occur in motor vehicle crashes, sports, and military events. The recently developed interaction criterion, termed Nij, has been used in automotive safety standards and is applicable to the upper neck. Such criterion does not exist for the lower neck. This study was designed to conduct an analysis of data of lower neck injury metrics toward the development of a mechanistically appropriate injury criterion. Axial loads were applied to the crown of the head of post mortem human subject (PMHS) head-neck complexes at different loading rates. The generalized force histories at the inferior end of the head-neck complex were recorded using a load cell and were transformed to the cervical-thoracic joint. Peak force and peak moment (flexion or extension) were quantified for each test from corresponding time histories. Initially, a survival analysis approach was used to derive injury probability curves based on peak force and peak moment alone. Both force and moment were considered as primary variables and age a covariate in the survival analysis. Age was found to be a significant (p<0.05) covariate for the compressive force and flexion moment but insignificant for extension moment (p>0.05). A lower neck Nij formulation was done to derive a combined interactive metric. To derive cadaver-based metrics, critical intercepts were obtained from the 90% injury probability point on peak force and peak moment curves. The PMHS-based critical intercepts derived from this study for compressive force, flexion, and extension moment were 4471 N, 218 Nm, and 120 Nm respectively. The lower cervical spine injury criterion, Lower Nij (LNij), was evaluated in two different formulations: peak LNij and mechanistic peak LNij. Peak LNij was obtained from the LNij time history regardless of when it occurred. Mechanistic peak LNij was obtained from the LNij time history only during the time when the resulting injury mechanism occurred. Injury mechanism categorization included compression-flexion, compression-extension, and those best represented by a more pure compression-related classification. Mechanistic peak LNij was identified based on the peak timing of the injury mechanism. Peak LNij and mechanistic peak LNij were found to be significant (p<0.05) predictors of injury with age as a covariate. The 50% injury probability was 1.38 and 1.13 for peak LNij and mechanistic peak LNij, respectively. These results provide preliminary data based on PMHS tests for establishing lower neck injury criteria that may be used in automotive applications, sports and military research to advance safety systems.
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Samuel, Robello, Kiran Kumar et Amol Nakhle. « Casing (Tubular) Runnability Indicator While Drilling With Real Time Drilling Data ». Dans SPE/IADC Asia Pacific Drilling Technology Conference and Exhibition. SPE, 2024. http://dx.doi.org/10.2118/219666-ms.
Texte intégralRésumé :
Abstract In drilling operations, the quality of the borehole used for casing installation significantly influences the overall smoothness of the drilling process, connecting the geometric aspects of the wellbore with the mechanical system employed. Complex equations, grounded in practical knowledge and real-time drilling parameters, offer a feasible approach to assess the suitability of a given borehole for casing installation in a specific hole size. Key factors such as wellbore tortuosity, borehole torsion, wellprofile energy, casing push-through force, margin of slack-off force, and overpull margin collectively contribute to evaluating the viability of a proposed wellpath for casing installation. The understanding of the expected running conditions during drilling itself will provide opportunities to correct the well conditions rather than running clean out runs or short landing the casing string. In scenarios requiring casing running in curved trajectories or extending to significant lateral lengths, amalgamating operational insights with trajectory parameters has proven effective in gauging operational risks. This approach leverages both experience and quantitative data to estimate the feasibility of casing installation. Moreover, this study delves into the dynamic adjustments of runnability metrics in response to real-time drilling conditions and survey data, enhancing the accuracy of operational assessments. Furthermore, this study extends beyond casing runnability assessments to explore the predictive capabilities of these metrics. By leveraging runnability measurements, operators can anticipate and address various challenges, including intricate stimulation tasks, optimizing artificial lift operations, and identifying potential issues with well servicing. These challenges often stem from undesirable borehole characteristics such as curvature, torsion, and drift, highlighting the multifaceted utility of runnability metrics in optimizing drilling operations and ensuring well integrity.
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Samuel, Robello, et Kiran Kumar. « Real Time Well Engineering : String (Drillstring/ Casing/Completion) Runnability Monitor While Drilling ». Dans SPE/IADC Middle East Drilling Technology Conference and Exhibition. SPE, 2023. http://dx.doi.org/10.2118/214615-ms.
Texte intégralRésumé :
Abstract The objective of this study is to monitor and forecast how well the casing string can be run during the drilling of the well's particular hole section. The runnability of the casing is measured by the use of a comprehensive index supported by real-time monitoring of multiple features with estimated indicators. The methodology developed by combining geometrical and mechanical calculations provides an assessment of whether the casing can be run without a short landing. This provides more opportunities for adjustments that can be made during drilling itself. In general, the "smoothness" that connects the wellbore geometry and mechanical system is related to the borehole quality utilized to run the casing. With real-time drilling parameters and complex equations represented with common sense, it is possible to assess the runnability of the casing for a given hole size. When taken together, wellbore tortuosity, borehole torsion, wellprofile energy, well curvature passage through force, margin of slack off force and overpull margin support the evaluation of a proposed wellpath to determine the casing's runnability. Combining operational experience and trajectory metrics in a methodology has proven to be effective in assessing operational risk for tasks like running casing in curve construction sections or to total depth on prolonged laterals. In addition, this paper discusses how the runnability metrics can help to anticipate or diagnose other challenges such as complex stimulation work, artificial lift performance and possible well servicing complications that may arise because of unwanted curvature, borehole torsion and wellbore drift. Presently there is no method to predict the runnability of casing to bottom while the well is being drilled. A new and practical method of quantifying the runnability of casing during drilling has been analyzed and proposed in this paper.
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Rovinelli, Andrea, Mark C. Messner et T. L. Sham. « Investigating the Correlation Between Different Effective Stress Measures and the Service Life of Actual High-Temperature Structural Components ». Dans ASME 2020 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/pvp2020-21471.
Texte intégralRésumé :
Abstract Effective stress measures are utilized by engineers to correlate uniaxial and biaxial experimental rupture data to creep failure in real components. Different effective stress formulations are used in various high temperature design codes, such as the Section III Division 5 of the ASME Boiler and Pressure Vessel code and the French RCC-MRx, and in different fitness for service provisions, such as the British R5 and the American FFS-1. Under uniaxial and biaxial stress states all the investigate metrics predict similar rupture times and provide similar safety margins, however there is no guarantee that when these metrics are extrapolated to predict the creep life for triaxial state they will remain conservative. In this work we use the real geometry of a Grade 91 end-plate that failed prematurely and finite element simulations to investigate the variability in creep life predictions obtained utilizing different effective stress as creep-damage driving force. Results show that for triaxial stress states the time to crack nucleation, the crack initiation site and the crack path are extremely sensitive to the effective stress measure.
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Tawata, Shohei, Keiichi Watanuki et Kazunori Kaede. « Time-Series Segmentation Based on Video Images of Cutting Operations with a Lathe in Virtual Reality Space ». Dans 13th International Conference on Applied Human Factors and Ergonomics (AHFE 2022). AHFE International, 2022. http://dx.doi.org/10.54941/ahfe1001789.
Texte intégralRésumé :
Due to the shortage of labor force in Japan, skill transfer and training education are becoming increasingly important in the manufacturing industry. In recent years, virtual reality (VR) technology has attracted attention in work-related training, enabling simplified training, but there is a problem that human and time resources cannot be sufficiently allocated to training due to a lack of educators and an immature training system. In this study, we developed a method to automatically recognize tasks and actions to improve the efficiency of education and training. To recognize tasks and actions, we adopted a deep learning model that can recognize actions from videos in time series, and we pre-trained the model on a large open-source dataset. We evaluated the performance of the model on unlearned procedures and people by preparing a dataset with three different procedures and 10 participants. The overall validation metrics all exceeded 90%. Specifically, results of more than 90% were achieved for unlearned people, but a drop of more than 5% was observed for all unlearned procedures, suggesting that issues must be addressed for application to task training.
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Samuel, Robello, Kiran Kumar et Amol Nakhle. « Casing Runnability Indicator While Drilling : Adaptive Threading of Engineering with Real Time Data ». Dans IADC/SPE International Drilling Conference and Exhibition. SPE, 2024. http://dx.doi.org/10.2118/217660-ms.
Texte intégralRésumé :
Abstract This paper aims to track and predict the best way to run the casing string while the specific hole segment of the well is drilled. Several variables with estimated indications are monitored in real-time, and a comprehensive index is used to measure the runnability of the casing. An evaluation of whether the casing can be run without a short landing is provided by the approach created by combining geometrical and mechanical parameter calculations. This gives the opportunity to make more modifications while the well is being drilled. Generally speaking, the borehole quality used to run the casing has an impact on the "smoothness" that links the wellbore geometry and mechanical system used to drill the portion of the well. It is feasible to determine the runnability of the casing for a particular hole size using complex equations represented with common sense and real-time drilling parameters. Wellbore tortuosity, borehole torsion, wellprofile energy, casing push through force, margin of slackoff force, and overpull margin all work together to facilitate the assessment of a suggested wellpath in order to ascertain the runnability of the casing. For operations like running casing in curve building sections or to total depth on lengthy laterals, combining operational experience and trajectory parameters in a methodology has shown to be an effective way to estimate operational risk. Furthermore, this study addresses the ways in which the runnability metrics can be adjusted in realtime with actual drilling and survey details. Furthermore, this study addresses the ways in which runnability measurements can be used to predict or identify other difficulties, such as intricate stimulation tasks, artificial lift functionality, and potential well servicing issues that could result from undesired curvature, borehole torsion, and wellbore drift.
Rapports d'organisations sur le sujet "Force-time metrics"
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Fee, Kyle D. Does Job Quality Affect Occupational Mobility ? Federal Reserve Bank of Cleveland, août 2022. http://dx.doi.org/10.26509/frbc-cd-20220804.
Texte intégralRésumé :
Job quality, a well-known topic in workforce development circles, is an underutilized but useful lens with which to examine labor market conditions. The Aspen Institute (2020), a long-time advocate for job quality, defines it as “a range of attributes that drive worker experiences: wages, benefits, scheduling, legal rights, equity and inclusion, opportunity to build skills and advance, supportive work environment, and worker voice.” Given the record number of resignations and available job openings, especially in the lower-paid industry sectors, along with popular labor market narratives around the Great R’s (Resignation, Renegotiation, Reshuffle), I wonder to what extent job quality plays a role in the occupational mobility of workers. Occupational mobility includes all potential outcomes an individual has when holding a job. For instance, in addition to the option of changing to another occupation, an individual can remain in that occupation, become unemployed, or leave the labor force. Occupational mobility metrics are an appealing way to explore labor market conditions because they provide a dynamic perspective, while traditional metrics such as unemployment and labor force participation rates tend to be static observations.