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Artykuły w czasopismach na temat "Swimming – Starts and turns"
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de Jesus, Karla, Luis Mourão, Hélio Roesler, Nuno Viriato, Kelly de Jesus, Mário Vaz, Ricardo Fernandes i João Paulo Vilas-Boas. "3D Device for Forces in Swimming Starts and Turns". Applied Sciences 9, nr 17 (30.08.2019): 3559. http://dx.doi.org/10.3390/app9173559.
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Biomechanical tools capable of detecting external forces in swimming starts and turns have been developed since 1970. This study described the development and validation of a three-dimensional (six-degrees of freedom) instrumented block for swimming starts and turns. Seven force plates, a starting block, an underwater structure, one pair of handgrips and feet supports for starts were firstly designed, numerically simulated, manufactured and validated according to the Fédération Internationale de Natation rules. Static and dynamic force plate simulations revealed deformations between 290 to 376 µε and 279 to 545 µε in the anterior-posterior and vertical axis and 182 to 328.6 Hz resonance frequencies. Force plates were instrumented with 24 strain gauges each connected to full Wheatstone bridge circuits. Static and dynamic calibration revealed linearity ( R 2 between 0.97 and 0.99) and non-meaningful cross-talk between orthogonal (1%) axes. Laboratory and ecological validation revealed the similarity between force curve profiles. The need for discriminating each upper and lower limb force responses has implied a final nine-force plates solution with seven above and two underwater platforms. The instrumented block has given an unprecedented contribution to accurate external force measurements in swimming starts and turns.
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Qiu, Xiao, Blanca De la Fuente, Alberto Lorenzo i Santiago Veiga. "Comparison of Starts and Turns between Individual and Relay Swimming Races". International Journal of Environmental Research and Public Health 18, nr 9 (29.04.2021): 4740. http://dx.doi.org/10.3390/ijerph18094740.
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The present study investigated swimmers’ performances on the starting and turning segments between individual and relay races. A total number of 72 race performances of the same swimmers in both relay 4 × 100 m finals (freestyle, medley, and mixed freestyle) and individual 100 m finals or semi-finals (butterfly, breaststroke, and freestyle) from the LEN European Swimming Championships were compared with repeated measures MANOVA. Swimmers performed 5–7% faster starts in the relay than in the corresponding individual events, despite no differences in the flight phase and a lower performance (shorter distances and slower velocities) on the underwater start section. The 15 m turn times were slower in the butterfly relay races although no specific differences in the underwater parameters were observed. These results suggest that specific training of the starting and turning segments should be performed under relay conditions to optimise pacing and performance in the underwater sections.
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Hermosilla, Francisco, Ross Sanders, Fernando González-Mohíno, Inmaculada Yustres i José M. González-Rave. "Effects of Dry-Land Training Programs on Swimming Turn Performance: A Systematic Review". International Journal of Environmental Research and Public Health 18, nr 17 (3.09.2021): 9340. http://dx.doi.org/10.3390/ijerph18179340.
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Swimming coaches have prescribed dry-land training programs over the years to improve the overall swimming performance (starts, clean swimming, turns and finish). The main aim of the present systematic review was to examine the effects of dry-land strength and conditioning programs on swimming turns. Four online databases were scrutinised, data were extracted using the Preferred PRISMA guidelines and the PEDro scale was applied. A total of 1259 articles were retrieved from database searches. From the 19 studies which were full-text evaluated, six studies were included in the review process. The review indicated that plyometric, strength, ballistic and core training programs were implemented for improving swimming turn performance. Strength, ballistic and plyometric training focusing on neural enhancement seem to be effective for improving swimming turn performance. The data related to training of the core were not conclusive. Coaches should consider incorporating exercises focusing on improving the neuromuscular factor of the leg-extensor muscles into their daily dry-land training programs. More researches are needed to provide a better understanding of the training methods effects and training organisations for improving swimming turn performance.
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Krause, Daniel. "Effects of additional knowledge of results on modifying highly practiced acyclic swimming techniques with knowledge of performance". International Journal of Sports Science & Coaching 12, nr 6 (2.11.2017): 737–46. http://dx.doi.org/10.1177/1747954117738894.
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The author investigated the effects of additional knowledge of results on modifying swimming starts and turns with video-based knowledge of performance. A total of 18 swimming experts (15–18 years of age) learned modifications of start and turn techniques with knowledge of performance or a combination of knowledge of performance and knowledge of results. The feedback condition was switched between the groups from experiment 1 to experiment 2. Both experiments contained 50 trials with augmented feedback distributed over five sessions. Both experiments revealed no detrimental effects of additional knowledge of results on process-related performance variables. With respect to the result-related variables (start time and turn time), only the groups without knowledge of results exhibited temporary impairment in the immediate retention tests. The results are largely replicated in both experiments. Knowledge of results seems to have positive effects on modifying with knowledge of performance. The presence of knowledge of results might reduce the deautomatizing conscious control processes that are induced by knowledge of performance and might cause temporary performance impairments.
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Šťastný, Jan. "Porovnání závodní rychlosti plaveckého způsobu kraul a rychlosti dosažené během intervalů bez vlivu startu a obrátek". Studia sportiva 10, nr 1 (11.07.2016): 110–16. http://dx.doi.org/10.5817/sts2016-1-11.
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The race at 50 meters in freestyle swimming technique can be divided into four main phases -start, swimming at the surface, turn, and finish. With the usage of our measuring system called Tachograph, we mainly analyse the speed of swimming at the surface. Measuring principle does not allow accurate measurement of the speed after starts and turns, for that reason we evaluate the particular sections without the influence of the start and finish. We focused on the evaluation of the ratio of the measured mean swimming speed measured by the system Tachograph with the results of the current best racing performance from the 50 metre distance. For comparison we have processed the results of swimmers who participated in the semi-finals of 2010 European Championship. Our goal was to establish which results of the swimmers measured by Tachograph are at a sufficient level. The objective of the work has been accomplished with the help of statistical methods. Furthermore, we have ascertained that our recorded results differ from the results of elite swimmers whose results have been gained from the evaluation of the sections of swimming at the European Championship. We assume that the race results of our measured swimmers will differ as well. The error may be caused not only by the lack of motivation of the swimmers but also due to the constraints that our measurement system causes.
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Olstad, Bjørn Harald, Henrik Wathne i Tomohiro Gonjo. "Key Factors Related to Short Course 100 m Breaststroke Performance". International Journal of Environmental Research and Public Health 17, nr 17 (27.08.2020): 6257. http://dx.doi.org/10.3390/ijerph17176257.
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Background and aim: To identify kinematic variables related to short course 100 m breaststroke performance. Methods: An automatic race analysis system was utilized to obtain start (0–15 m), turn (5 m before the wall until 10 m out), finish (95–100 m), and clean swimming (the rest of the race) segment times as well as cycle rate and cycle length during each swimming cycle from 15 male swimmers during a 100 m breaststroke race. A bivariate correlation and a partial correlation were employed to assess the relationship between each variable and swimming time. Results: Turns were the largest time contributor to the finishing time (44.30 ± 0.58%), followed by clean swimming (38.93 ± 0.50%), start (11.39 ± 0.22%), and finish (5.36 ± 0.18%). The finishing time was correlated (p < 0.001) with start segment time (r = 0.979), clean swimming time (r = 0.940), and 10 m turn-out time (r = 0.829). The clean swimming time was associated with the finishing time, but cycle rate and cycle length were not. In both start and turns, the peak velocity (i.e., take-off and push-off velocity) and the transition velocity were related to the segment time (r ≤ −0.673, p ≤ 0.006). Conclusions: Breaststroke training should focus on: (I) 15 m start with generating high take-off velocity, (II) improving clean swimming velocity by finding an optimal balance between cycle length and rate, (III) 10 m turn-out with maintaining a strong wall push-off, and (IV) establishing a high transition velocity from underwater to surface swimming.
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Li, Gen, Ulrike K. Müller, Johan L. van Leeuwen i Hao Liu. "Escape trajectories are deflected when fish larvae intercept their own C-start wake". Journal of The Royal Society Interface 11, nr 101 (6.12.2014): 20140848. http://dx.doi.org/10.1098/rsif.2014.0848.
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Fish larvae may intercept their own wake during sharp turns, which might affect their escape performance. We analysed C-starts of larval zebrafish ( Danio rerio , Hamilton, 1822) using a computational fluid dynamics approach that simulates free swimming (swimming trajectory is determined by fluid forces) by coupling hydrodynamics and body dynamics. The simulations show that fish may intercept their own wake when they turn by 100–180°. During stage 1 of a C-start, the fish generates a strong jet at the tail that is shed into the wake. During stage 2, the fish intercepts this wake. Counterfactual simulations showed that wake interception increased the lateral force on the fish and reduced the fish's turning angle by more than 5°. Wake interception caused no significant acceleration tangential to the trajectory of the fish and did not affect total power output. While experimental and simulation evidence suggests that fish larvae can either undershoot or intercept but not overshoot their wake, our simulations show that larger fish might be able to avoid intercepting their wake by either under- or overshooting. As intercepting its own wake modifies the fish's escape trajectory, fish should account for this effect when planning their escape route.
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Marinho, Daniel, Tiago Barbosa, Abel Rouboa i António Silva. "The Hydrodynamic Study of the Swimming Gliding: a Two-Dimensional Computational Fluid Dynamics (CFD) Analysis". Journal of Human Kinetics 29, nr 1 (1.09.2011): 49–57. http://dx.doi.org/10.2478/v10078-011-0039-4.
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The Hydrodynamic Study of the Swimming Gliding: a Two-Dimensional Computational Fluid Dynamics (CFD) AnalysisNowadays the underwater gliding after the starts and the turns plays a major role in the overall swimming performance. Hence, minimizing hydrodynamic drag during the underwater phases should be a main aim during swimming. Indeed, there are several postures that swimmers can assume during the underwater gliding, although experimental results were not conclusive concerning the best body position to accomplish this aim. Therefore, the purpose of this study was to analyse the effect in hydrodynamic drag forces of using different body positions during gliding through computational fluid dynamics (CFD) methodology. For this purpose, two-dimensional models of the human body in steady flow conditions were studied. Two-dimensional virtual models had been created: (i) a prone position with the arms extended at the front of the body; (ii) a prone position with the arms placed alongside the trunk; (iii) a lateral position with the arms extended at the front and; (iv) a dorsal position with the arms extended at the front. The drag forces were computed between speeds of 1.6 m/s and 2 m/s in a two-dimensional Fluent® analysis. The positions with the arms extended at the front presented lower drag values than the position with the arms aside the trunk. The lateral position was the one in which the drag was lower and seems to be the one that should be adopted during the gliding after starts and turns.
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Born, Dennis-Peter, Joris Kuger, Marek Polach i Michael Romann. "Turn Fast and Win: The Importance of Acyclic Phases in Top-Elite Female Swimmers". Sports 9, nr 9 (31.08.2021): 122. http://dx.doi.org/10.3390/sports9090122.
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The aim of the study was to investigate the effect of start and turn performances on race times in top-elite female swimmers and provide benchmarks for all performance levels, all swimming strokes, and all race distances of the European Short-Course Championships (EC). The individual races (n = 798) of all female competitors (age: 20.6 ± 3.9 years, FINA points: 792 ± 78) were video-monitored for subsequent analysis of start and turn performances. Benchmarks were established across all competitors of each event based on the 10th, 25th, 50th, 75th, and 90th percentiles. Start and turn performances contributed up to 27.43% and 56.37% to total race time, respectively. Mechanistic analysis revealed that the fastest swimmers had the lowest contribution of the acyclic phases to race time. Therefore, relative to their faster race times, these swimmers were even faster during starts and turns. Multiple linear regression analysis showed large effects of turn performance on 50, 100, 200, 400, and 800 m race times (β = 0.616, 0.813, 0.988, 1.004, and 1.011, respectively), while the effect of start performance continuously decreased the longer the race distance. As turn performance may be the distinguishing factor in modern short-course races, benchmarks should be used to set goals and establish training guidelines depending on the targeted race time.
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Slawson, S. E., P. P. Conway, L. M. Justham i A. A. West. "The development of an inexpensive passive marker system for the analysis of starts and turns in swimming". Procedia Engineering 2, nr 2 (czerwiec 2010): 2727–33. http://dx.doi.org/10.1016/j.proeng.2010.04.058.
Pełny tekst źródłaRozprawy doktorskie na temat "Swimming – Starts and turns"
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Lindley, Steven L. "Kinematic analysis of freestyle and backstroke flip-turns in competitive swimming". Virtual Press, 2001. http://liblink.bsu.edu/uhtbin/catkey/1221279.
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The primary purpose of this study was to gain a better understanding of the turn interval and the factors that influence turn performance. A secondary purpose was to investigate the relationship between turn time, the components that influence turn time, and performance in competitive swimming. Fifty-eight swimmers (24 female, 34 male) from four NCAA Division I schools were videotaped in the 100 and 200 yd freestyle and backstroke events during three collegiate competitions. The freestyle was shown to be significantly different from the backstroke in race time, turn time, and time during the in phase of the turn for both genders in the 100 and 200 yard events. Significant positive correlations were found between turn time and race time across both genders and all four events. Inspecting the velocity curves of the turns allowed the key outphase variables to be defined. Turn time is an important determinant of race time in collegiate swimming. Using the dolphin kick technique during a turn causes large fluctuations in velocity during the active glide phase of the turn.School of Physical Education
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Clothier, Peter University of Ballarat. "Underwater kicking following the freestyle tumble-turn". University of Ballarat, 2004. http://archimedes.ballarat.edu.au:8080/vital/access/HandleResolver/1959.17/12776.
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Swim turns are a component of competitive swimming where considerable advantage can be gained or lost. This thesis investigates underwater dolphin and flutter kicking techniques and their application to exits following the turn in freestyle swimming. Five separate investigations were conducted to examine the kinetics and kinematics of each underwater kicking technique and are presented in expanded journal manuscript form. Studies one, two and three involved the comparison of freestyle turns when using flutter and dolphin kicking wall exit techniques. The results obtained indicated that freestyle turns using flutter kicking were faster than dolphin kicking in age-group swimmers. For this group, significant and equal improvements were made to flutter and dolphin kick turn performances following six weeks of dolphin kick and dolphin kick turn training. However, no difference in turn times were observed between kicking conditions by older and more highly skilled swimmers. Study four involved a kinematical comparison of maximal underwater free-swimming dolphin and flutter kicking. Results showed dolphin kick to be a superior underwater free-swimming technique. Greater foot width, increased ankle range of movement and greater vertical displacement of the ankle and foot during kicking were shown to be highly predictive of faster underwater dolphin kicking. Investigation five compared the drag forces and kinematics between the dolphin and flutter kicking techniques while subjects were towed at velocities representing those experienced following wall turn push-off. Results favour the dolphin kick as a superior underwater technique at these higher velocities. Increased underwater dolphin kicking efficiency, as measured by decreased net towing force, was found to be associated with larger kick amplitude – rate ratios, and higher kick amplitude – streamline length ratios.Doctor of Philosophy
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Clothier, Peter. "Underwater kicking following the freestyle tumble-turn". University of Ballarat, 2004. http://archimedes.ballarat.edu.au:8080/vital/access/HandleResolver/1959.17/14612.
Pełny tekst źródłaStreszczenie:
Swim turns are a component of competitive swimming where considerable advantage can be gained or lost. This thesis investigates underwater dolphin and flutter kicking techniques and their application to exits following the turn in freestyle swimming. Five separate investigations were conducted to examine the kinetics and kinematics of each underwater kicking technique and are presented in expanded journal manuscript form. Studies one, two and three involved the comparison of freestyle turns when using flutter and dolphin kicking wall exit techniques. The results obtained indicated that freestyle turns using flutter kicking were faster than dolphin kicking in age-group swimmers. For this group, significant and equal improvements were made to flutter and dolphin kick turn performances following six weeks of dolphin kick and dolphin kick turn training. However, no difference in turn times were observed between kicking conditions by older and more highly skilled swimmers. Study four involved a kinematical comparison of maximal underwater free-swimming dolphin and flutter kicking. Results showed dolphin kick to be a superior underwater free-swimming technique. Greater foot width, increased ankle range of movement and greater vertical displacement of the ankle and foot during kicking were shown to be highly predictive of faster underwater dolphin kicking. Investigation five compared the drag forces and kinematics between the dolphin and flutter kicking techniques while subjects were towed at velocities representing those experienced following wall turn push-off. Results favour the dolphin kick as a superior underwater technique at these higher velocities. Increased underwater dolphin kicking efficiency, as measured by decreased net towing force, was found to be associated with larger kick amplitude – rate ratios, and higher kick amplitude – streamline length ratios.Doctor of Philosophy
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Hardt, Julie E. "Optimization of the competitive swimming track start based on lower limb asymmetry". University of Western Australia. School of Sport Science, Exercise and Health, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0192.
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The swimming track start is a complex motor skill that utilizes asymmetric lower limb action. The purpose of this study was to explore whether it could be optimized by applying the commonly accepted view that there are asymmetries in the function and behaviors of the lower limbs. Initially, the study aimed to examine the relationship between various measures of lower limb asymmetry and the swimmers' preferences for forward foot placement in the swimming track start. Participants underwent a 7 week training period whereby both the left foot forward (LFF) and the right foot forward (RFF) track starts were practiced. The philosophy behind this training protocol was to ensure that participants received equal practice with the preferred and non-preferred stance so that a dominant stance, if it existed, could emerge. Consequently, the relationships between the dominant track start stance and the lower limb asymmetry measures could be determined more accurately. Participants were male (N=11) and female (N=11) swimmers, aged 12-16 years, from the UWA-Uniswim National Age Squad. Kinetic and kinematic data were collected for the track start prior to and following the 7 week training intervention. The intervention was finished when a participant had completed approximately 14 dive sessions where both the LFF and RFF track starts were practiced. The performance criterion measure was time to 5 m. Despite significant differences in vertical force and velocity contributions following the intervention, time to 5 m did not improve for either the LFF or the RFF track start. Four different measures of lower limb asymmetry were collected, including footedness, the preferred track start stance, and the dominant take-off limb for the unilateral and bilateral counter-movement jump (CMJ). Sixteen of 22 participants displayed changes in their dominant track start stance. Eleven participants showed biases for one stance (6 for the LFF & 5 for the RFF), and 11 participants remained or became more symmetrical. Results indicated that the preferred track start stance was the only measure of asymmetry that was significantly related to track start performance (x2[2]= 6.71, p=.04 for pre-intervention & x2[2]=7.77, p=.02 for post-intervention). All other measures of lower limb asymmetry were shown to be unrelated to track start preference and performance. It was suggested that the 7 week training intervention did not provide a sufficient amount of time to see conclusive effects on 5 m time or to make conclusive comparisons between the dominant track start stance and measures of asymmetry. Since the preferred track start corresponded with better performance less than 50% of the time, it was suggested that swimmers and coaches experiment with different dive techniques to find the start which is most effective for them and spend more time on them during training.
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Farrell, Matthew Todd. "Angular momentum in turns and abrupt starts : strategies for bipedal balance control". Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/51660.
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Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2009.Includes bibliographical references (p. 81-83).
Transients occur in human walking during a transition to, from, and between steady state walking and act as an impulse destabilizing an otherwise normal gait cycle. Turns and accelerated starts are all common transients encountered and managed intelligently by humans everyday. The population of elderly has increased and understanding balance control in healthy subjects will be more important. In addition, humanoid bipeds are rapidly becoming a more common part of our everyday life. Therefore, they must also be able to navigate our environments adroitly if they are to assist us in our daily living. This thesis takes biomechanical principals of angular momentum and applies them to healthy subjects in an effort to elucidate human balance control strategies. Each transient task is unique, and despite large segmental contributions to whole-body angular momentum during movement, the whole-body angular momentum remains tightly regulated. A analysis of segmental contributions to the principal components explaining more than 90% makes clear the balance control strategy used by healthy humans during these transients.
by Matthew Todd Farrell.
S.M.
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Smithdorf, Gareth. "Effect of tumble turns on swimming performance in level 3 swimmers". University of the Western Cape, 2018. http://hdl.handle.net/11394/6847.
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Magister Artium (Sport, Recreation and Exercise Science) - MA(SRES)Swimming, as a sport, is constantly developing, both through the resources employed in training and assessment, and through the technological development of the fundamental aspects of swimming. In the freestyle events, swimmers spend between 38% and 50% of their competition time executing turns in short pool competitions over distances that vary from 50 m to 1500 m. The importance of the turn has been noted and analyzed for several decades, where it was found that the final turn velocity was second only to mid-pool swimming velocity for determining a medal finish in the men’s race. Due to the impact that the tumble turn has on swimming performance, the present study investigated the importance of the tuck index, foot-plant index and wall-contact time (WCT) on swimming performance. Therefore, the aim of this study was to determine the effect of the tuck index, foot-plant index, and WCT on the round trip time (RTT) in the tumble turn performance in level 3 swimmers in the freestyle swimming stroke. A quantitative cross-sectional and descriptive design was used in this study. A convenient sample of ten (10) swimmers were tested, five male and five female, all being level 3 swimmers affiliated to the high performance team of Swimming South Africa (SSA). Video analyses of the turns were recorded. Each subject performed thirty (30) trials, each consisting of a 50 m freestyle swim with flip turns at race pace. Descriptive statistics and multiple stepwise regression analyses were used to analyse the data. A p-value of below 0.05 indicated statistical significance. The mean tuck index was 0.57 ± 0.14°. The mean foot-plant index was 0.45 ± 0.10 cm. The mean WCT was 74.31 ± 11.57 %. The mean RTT was 2.47 ± 0.40 s. A significant negative correlation was found between tuck index and RTT (r = -0.41; p < 0.05). No significant relationship was found between foot-plant and WCT. Further regression analysis showed that the tuck index was a significant predictor of RTT (F = 21.745, p < 0.001). Following the freestyle tumble turn, the flutter kick technique remained the superior method of exiting the wall, based on the 5 m RTT. Therefore, the introduction of optimal turning practice for age-group swimmers is likely to result in significant reductions in turning times and should be noted by coaches and swimmers alike.
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Lyttle, Andrew. "Hydrodynamics of the human body during the freestyle tumble turn". University of Western Australia. Dept. of Human Movement and Exercise Science, 2000. http://theses.library.uwa.edu.au/adt-WU2006.0126.
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This thesis contains three cross-sectional studies and an equipment development study, presented in the form of journal submissions, regarding the hydrodynamics experienced by swimmers during the various phases of the freestyle tumble turn.
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Li, Jason. "Swimming in four goldfish (Carassius auratus) morphotypes: understanding functional design and performance through artificial selection". Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/223.
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Although artificially selected goldfish exhibit swimming performance decrements, with the most derived morphotypes more affected, they can be utilized to explore functional design and movement pattern principles in aquatic vertebrates. Drag, steady swimming kinematics (tailbeat frequency, amplitude, stride length), energetics (standard and active metabolic rate), fast-start performance (average and maximum velocity and acceleration), stability in yaw and roll and propulsive muscle ultrastructural characteristics (mitochondrial volume density and spacing, myofibril diameter and capillary to fibre ratio in red and white muscle) were measured for four morphotypes: common, comet, fantail and eggfish, of comparable length (≈ 5 cm). A performance “pairing” (common and comet; fantail and eggfish) was a recurrent theme for most performance parameters. Vertebral numbers (30), segment lengths (≈ 0.85 mm) and standard metabolic rates (≈ 140 mg O2 kg-1 hr-1) are exceptions where values are the same. Fantail and eggfish drag and drag coefficients (referenced to frontally projected area ≈ 0.6 - 0.9) were higher (requiring more thrust at any given velocity) than those for the more streamlined common and comet (≈ 0.3 - 0.6; P < 0.05). This is reflected in kinematics; tailbeat frequency and stride length at any given velocity for the common and comet are lower and higher respectively than that of the fantail and eggfish (P < 0.05). Common and comet fatigue times are not significantly different from that of their ancestor, Crucian carp (P > 0.05), and are lower than those of the fantail and eggfish (P < 0.05). The cost of transport of the common and comet (≈ 0.6 mg O2 kg-1 m-1) is accurately predicted from the mass scaling relationship for fish (P > 0.05), but values for the fantail and eggfish (≈ 1.3 mg O2 kg-1 m-1) are not (P < 0.05). Eggfish steady swimming (dorsal fin absent) was characterized by rolling and yawing motions associated with significant energy losses. Common and comet fast-start performance (average velocity ≈ 0.45 m s-1, maximum velocity ≈ 1.2 m s-1, average acceleration ≈ 7.5 m s-2, maximum acceleration ≈ 35 m s-2) was similar to that of other locomotor generalists (e.g. trout). Eggfish maximum acceleration (≈ 5 m s-2) is poor due to the absence of inertial and lifting contributions to thrust from the dorsal fin and energy wasting rolling motions. Artificially selected fish can bear upon fitness related adaptations associated with form and movement, providing insights into the “performance envelope” of natural systems subject to ecological speciation.
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Hubert, Marcel. "Determinação do procedimento para coleta de dados biomecânicos da saída no nado crawl". Universidade do Estado de Santa Catarina, 2005. http://tede.udesc.br/handle/handle/377.
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Previous issue date: 2005-08-09Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
It aimed to determine a procedure to evaluate the swimming starts through biomechanical methods. For this descriptive and exploratory study one analyzed the starts of 4 s tate andnational level swimmers, members of the swimming team from Doze de Agosto Club (Florianópolis, SC). Data were collected in the swimming pool of Doze de Agosto Club and treated in the Aquatic Biomechanics Research Laboratory of Santa Catarina State University. An underwater force plate was used. The force plate was fixed as a starting block in the opposite side of the original blocks. Two video cameras placed outside and inside the water were used in order to provide a lateral view of the starting block and of the swimming pool up to 15m (according to swimming rules it is the maximum distance for the swimmer to be completely submerged after the start). Light-emitting diodes were placed in the image field of the video cameras and connected to a signal synchronizer. Starting procedures conformed to the swimming rules of an official Freestyle event. Data were post-processed by SAD 32 System. For kinematic data InterVideo WinProducer 3 e CorelDraw software were used. Descriptive statistics was used to characterize data and Pearson s correlation was used to verify the relationship between the variables and the start performance (α=0,05). One verified there is a relationship between the variables angle of entry, flight distance and time in 5m and the start performance in the three different measured distances (10m, 15m and distance of the beginning of the stroke); the vertical force peak and the time in 10m were correlated to the performance measured in 15m and in the beginning of the stroke; the horizontal force peak, the resultant force, the takeoff angle, the distance of the beginning of the stroke and time of the underwater phase were only correlated to the time of the beginning of the stroke; there was a relationship between the block time and the time in 15m; there was also a relationship between the time of the beginning of the stroke and the time in 10m. The flight time was the only variable that did not present any correlation to the performance. One verified that the most adequate distance to evaluate the start performance was 10m; and three executions were enough to analyze the start variables.
Esta pesquisa teve como objetivo determinar um procedimento para se realizar avaliações das saídas na natação, através de medições biomecânicas.Participaram deste estudo 4 nadadores de níveis estadual e nacional, integrantes da equipe de natação do Clube Doze de Agosto, Florianópolis, SC. Os dados foram coletados na piscina do clube Doze de Agosto e tratados no Laboratório de Biomecânica Aquática do Centro de Educação Física, Fisioterapia e Desportos - CEFID/UDESC. Para a coleta de dados foi utilizada uma plataforma de força subaquática fixada sobre um suporte simulando o bloco de partida, posicionada na borda contrária a dos blocos da piscina. Simultaneamente, foram utilizadas duas câmeras de vídeo posicionadas dentro e fora da piscina, de forma que proporcionassem uma visão lateral e superior do bloco de partida e da piscina, até uma distância de 15m (distância máxima permitida pelas regras para que o nadador permaneça submerso). Um emissor de sinal luminoso (LED) ligado a um sincronizador de sinais foi enquadrado no campo de imagem de todas as câmeras e o sinal de partida foi dado seguindo procedimentos oficiais de partida de uma prova de nado Livre. Os dados obtidos por dinamometria foram pós-processados pelo sistema SAD-32. Para a cinemetria foram utilizados os softwares de edição de imagens InterVideo WinProducer 3 e CorelDRAW. Para a caracterização dos dados foi utilizada a estatística descritiva e para a verificação da relação entre as variáveis e a performance foi utilizada a correlação de Pearson (α=0,05). Verificou-se que as variáveis: ângulo de entrada, distância de vôo e tempo em 5 m têm relação com a performance na saída nas três distâncias testadas, já as variáveis pico máximo de força vertical e tempo em 10 m têm relação com a performance apenas nas distâncias de 15 m e de início do nado. As variáveis: pico máximo de força horizontal, força resultante, ângulo de saída, distância de início de nado e tempo submerso têm relação somente com o tempo de início de nado. O tempo de bloco tem relação com o tempo em 15 m e o tempo de início de nado com o tempo em 10 m. Das variáveis testadas somente para o tempo de vôo não foi encontrada correlação. A distância determinada como mais adequada para obtenção do tempo de performance foi 10 metros. O número mínimo e suficiente de execuções encontrado para analise das saídas foi de três.
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Howe, Stephen P. "Exploring the Kinematics and Performance of Routine Maneuvers Using Live Fish and Robotic Models". University of Akron / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron1595875843391269.
Pełny tekst źródłaKsiążki na temat "Swimming – Starts and turns"
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The science of a flip turn. Ann Arbor, Michigan: Cherry Lake Publishing, 2016.
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Wake me when the band starts playing. New York: E.P. Dutton, 1988.
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Jenkins, Mark Peter. A cinematographical analysis of two types of backstroke turn. Cardiff: S.G.I.H.E., 1985.
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Juergens, Cheryl A. A kinetic and kinematic comparison of the grab and track starts in competitive swimming. 1994.
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A comparison among the track and grab starts in swimming and a stand-up response task. 1990.
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A comparison among the track and grab starts in swimming and a stand-up response task. 1988.
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A comparison among the track and grab starts in swimming and a stand-up response task. 1990.
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A comparison among the track and grab starts in swimming and a stand-up response task. 1990.
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Barbira-Freedman, Françoise. Water Babies: Safe Starts in Swimming. Southwater, 2004.
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Hopper, Nancy J. Wake Me When the Band Starts Playing. E P Dutton, 1992.
Znajdź pełny tekst źródłaCzęści książek na temat "Swimming – Starts and turns"
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Adema, Willem, Chris Clarke i Olivier Thévenon. "Family Policies and Family Outcomes in OECD Countries". W The Palgrave Handbook of Family Policy, 193–217. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-54618-2_9.
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AbstractFamilies in OECD member countries have changed dramatically in recent decades. Across almost all OECD countries, couples are marrying and starting a family later than ever before. Fertility rates are low. Divorce and re-partnering have become much more common, giving rise to a diversity of new family forms. The (male) single-earner family model, previously dominant, is now largely a thing of the past. This chapter examines how families and family policies have changed in OECD countries in recent decades. It starts with an overview of changes in families, in partnering behaviours, in family living arrangements, and in family work arrangements. The chapter then turns to the evolution of family policy and the policy response to changing families, such as increases in public Early Childhood Education and Care (ECEC) support and the provision of fathers-only paid parental leave. It concludes by highlighting important key challenges ahead, including how policy must adapt to growing inequalities between families.
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Cristani, Federica. "The Role of Sub-Regional Systems in Shaping International Investment Law-Making: The Case of the Visegrád Group". W Public Actors in International Investment Law, 135–53. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-58916-5_8.
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AbstractThe present chapter focuses on the role of the Visegrád group (or V4, comprising Slovakia, Hungary, Poland and the Czech Republic) in international investment law-making. The chapter starts with a brief overview of the V4 group as a sub-regional system in Europe, including its modus operandi and main achievements in the field of economic cooperation. Subsequently, it turns to the regulation of foreign direct investment (FDI), both at the level of each V4 state and at EU level—with particular regard to the implication of the EU’s exclusive competence on FDI. Special attention is paid to the approach of the V4 countries towards the question of termination of intra-EU bilateral investment treaties (BITs)—including an overview of the related objections to jurisdiction that the four countries have raised over the years in investor-state arbitrations based on intra-EU BITs—and to the relationship of the V4 group with non-EU countries—especially with (selected) East Asian countries. The main question is whether—and to what extent—the V4 group as a sub-regional system has a role to play in international investment law-making. The chapter highlights the proactive and advocacy role that the V4 group has traditionally played in manifold subject-matters, including the promotion and protection of FDI, and supports the positive “soft power” the V4 may exercise in this respect.
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Rietjens, Sebastiaan. "Intelligence in Military Missions: Between Theory and Practice". W Handbook of Military Sciences, 1–20. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-02866-4_96-1.
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AbstractIntelligence is the primary mechanism that military organizations use to generate understanding and its main purpose is to provide information to decision-makers such as commanders that may help illuminate their decision options. This chapter assesses the role of intelligence in military missions, more specifically the counterinsurgency and stabilizations missions that took place in, for example, former Yugoslavia, Iraq, Afghanistan, and Mali.The chapter starts by addressing the changing and increasingly complex nature of many of the conflicts from the 1990s onwards. It explores how this has influenced the use of intelligence and presents two distinct schools of thought. The first school of thought, referred to as Jominian intelligence, tries to unravel the operational environment in a systematic way and regards the intelligence challenges as a series of problems with definite solutions. The second school of thought, referred to as Clausewitzian intelligence, argues that the goal of intelligence is to assess uncertainty and reach a deliberate judgment.The main body of the chapter then analyzes the intelligence process and identifies several of the main intelligence issues within military missions. The intelligence process starts with the direction phase in which policy makers, military commanders, or planners state their needs, often referred to as information requirements. Several issues complicate such direction, including (1) the comprehensive focus of many current military missions, (2) their abstract and ambiguous strategic objectives and expectations, and (3) the military’s unfamiliarity with the area of operations.In the second phase of the intelligence process, the necessary information is collected. In addition to consulting their archives and databases, military units often have a plethora of means, both technical and human, available to collect information. Cross-cultural competencies are of crucial importance, in particular, during the collection phase.The third phase of the intelligence process, labeled processing, turns raw data into intelligence. During the processing phase, the data are analyzed in order to gain understanding or insight. This exceeds the registration of events, but includes understanding the meaning of these events as well as their importance.The fourth and final phase is dissemination of intelligence. Here, the relationship between the producers and consumers of intelligence during military missions is explored. This includes the reasons why consumers sometimes do not fully accept the intelligence they receive.The chapter concludes with an agenda for research on military intelligence. It calls, for example, for a more eclectic author base; multidisciplinary as well as comparative research; increased attention to oversight, ethics, and open source intelligence; and more emphasis on intelligence within the navy, special forces, and constabulary forces.
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Cohen, Jonathan H., i Charles E. Epifanio. "Response to Visual, Chemical, and Tactile Stimuli". W Developmental Biology and Larval Ecology, 333–60. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780190648954.003.0012.
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Early life history in marine benthic crustaceans often includes externally brooded eggs that hatch into free-swimming planktonic larvae. These larvae are relatively strong swimmers, and movement in the vertical plane provides a number of advantages, including modulation of horizontal transport and assurance of favorable predator–prey interactions. Swimming behavior in larval crustaceans is regulated by predictable external cues in the water column, primarily light, gravity, and hydrostatic pressure. Light-regulated behavior depends upon the optical physics of seawater and the physiology of light-detecting sensory structures in the larvae, which overall vary little with ontogeny. Swimming in response to light contributes to ecologically significant behaviors in planktonic crustacean larvae, including shadow responses, depth regulation, and diel vertical migration. Moreover, the photoresponses themselves, and in turn the evoked behaviors, change with the needs of larvae as development progresses. Regarding other sensory modalities, crustacean embryos and larvae respond to chemical cues using bimodal sensilla (chemosensory and mechanosensory) as contact receptors, and aesthetascs for detection of water-soluble cues. Processes and behaviors are stimulated by larval detection of chemical cues throughout ontogeny, including egg-hatching, avoidance of predators during free-swimming stages, and, ultimately, settlement and metamorphosis in juvenile habitats. The latter process can also involve tactile cues. The sensory-mediated behaviors described here for crustacean larvae have parallels in numerous arthropod and nonarthropod taxa. Emerging directions for future research on sensory aspects of behavior in crustacean larvae include multimodal sensory integration and behavioral responses to changing environmental stressors.
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Lowe, N. V., G. Douglas, E. Hitchings i R. Taylor. "13. Who has Parental Responsibility?" W Bromley's Family Law, 471–97. Oxford University Press, 2021. http://dx.doi.org/10.1093/he/9780198806691.003.0013.
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Having considered the content of parental responsibility in chapter 12, this chapter turns to its allocation. The chapter starts by explaining the allocation of parental responsibility automatically at the child’s birth and through registration on the birth certificate. It then turns to consider applications by unmarried, unregistered fathers for parental responsibility orders. The acquisition of parental responsibility by non-parents, including step-parents and local authorities is then outlined. Finally, it discusses the question of shared parental responsibility and how that responsibility may be exercised in the case of disagreement.
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Schmaltz, Tad M. "Epilogue". W The Metaphysics of the Material World, 267–74. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780190070229.003.0008.
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These brief concluding remarks return to Bayle’s critique of Spinoza. The assessment of his objection that Spinoza’s God cannot be immutable insofar as extended substance is the subject of changing modes draws on the history of the notion of a mode that starts with Suárez, proceeds through Descartes, and ends in Spinoza. The assessment of Bayle’s objection that Spinoza’s God cannot be indivisible insofar as extended substance is composed of distinct parts focuses rather on a line of thought that starts with Suárez’s conception of accidental quantity. It turns out that the substantial quantity that Spinoza posits is at some remove not only from the composite though unified quantity that functions as a fundamental accident in Suárez, but also from the collection of substantial parts that plays the role of Descartes’s extended substance.
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Morgan, Polly. "3. Ending a Marriage or Civil Partnership". W Family Law, 97–160. Oxford University Press, 2021. http://dx.doi.org/10.1093/he/9780198834243.003.0003.
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This chapter starts with a brief history of divorce. The chapter then considers the current law on divorce, its historical origins and strengths, and its weaknesses. It then turns to the new law on divorce which is due to come into effect in the autumn of 2021. The chapter asks: Why was reform needed? What role does divorce play in our society? What does divorce say about marriage as an institution? The chapter uses a real-life scenario to answer these questions.
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Morgan, Polly. "2. Marriage and Civil Partnership". W Family Law, 8–96. Oxford University Press, 2021. http://dx.doi.org/10.1093/he/9780198834243.003.0002.
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This chapter starts by considering how people get married, tracing the institution of marriage through history. It looks at the evolving popularity of marriage to the present day. The chapter then addresses the social and legal significance of marriage. It asks: Why does the state encourage people to marry? The chapter also looks at other ways in which relationships can be formalised under the law. Finally, the chapter turns to civil partnerships and looks at the changes in legal status to such partnerships over time. It also considers public perceptions of civil partnerships. Finally the chapter asks: Is there a future for marriage?
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Essler, Fabian H. L. "Applications of integrable models in condensed matter and cold atom physics". W Integrability: From Statistical Systems to Gauge Theory, 319–51. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198828150.003.0007.
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This chapter starts with a discussion of approximate physical realizations of 1+1-dimensional integrable models in solids and systems of ultra-cold trapped atoms. It then turns to local properties of energy eigenstates away from the edges of the spectrum. In generic models these states are thermal, while in integrable models non-thermal states with finite entropy densities coexist with thermal states. It discusses how to construct these atypical states by means of the Bethe Ansatz in the Heisenberg model. Finally, it outlines the crucial role these states play in describing the stationary states reached at late times after quantum quenches to integrable theories.
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Cardoso, Rui Costa, i Abel Gomes. "Security Issues in Massively Multiplayer Online Games". W Handbook of Research on Serious Games as Educational, Business and Research Tools, 290–314. IGI Global, 2012. http://dx.doi.org/10.4018/978-1-4666-0149-9.ch016.
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Massively Multiplayer Online Games (MMOGs) have been steadily growing in interest over the past decade. Their economic value turns them into one of the main targets of malware and cheating in Internet. This chapter presents and discusses security issues in MMOG environments. The study starts with a preliminary characterization of MMOGs, highlighting their main features. Afterwards, the authors present the security approaches that are applicable to MMOGs, exposing the implications of security breaches and the need for better protection mechanisms. Next, the chapter presents current safety measures and solutions to tackle specific security issues. Finally, security trends that can be relevant in the future are described.
Streszczenia konferencji na temat "Swimming – Starts and turns"
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Wärmefjord, Kristina, Rikard Söderberg, Lars Lindkvist, Björn Lindau i Johan S. Carlson. "Inspection Data to Support a Digital Twin for Geometry Assurance". W ASME 2017 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/imece2017-70398.
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Geometrical variation is a problem in all complex, assembled products. Recently, the Digital Twin concept was launched as a tool for improving geometrical quality and reduce costs by using real time control and optimization of products and production systems. The Digital Twin for geometry assurance is created together with the product and the production systems in early design phases. When full production starts, the purpose of the Digital Twin turns towards optimization of the geometrical quality by small changes in the assembly process. To reach its full potential, the Digital Twin concept is depending on high quality input data. In line with Internet of Things and Big Data, the problem is rather to extract appropriate data than to find data. In this paper, an inspection strategy serving the Digital Twin is given. Necessary input data describing form and shape of individual parts, and how this data should be collected, stored and utilized is described.
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Fu, Juan, Bengt Sunden i Xiaoqian Chen. "Analysis of Self-Pressurization Phenomenon in a Cryogenic Fluid Storage Tank With VOF Method". W ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-63209.
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The self-pressurization phenomenon is studied numerically with the Volume of Fluid (VOF) method in a cryogenic fluid tank. Heat and mass transfer modelling is used for the phase change calculation at the interface. Transient simulations of the vaporization and pressure rise in a cylindrical liquid hydrogen tank are performed. The computations are carried out by using the CFD software package, Ansys Fluent, and an in-house developed code to calculate the source term associated with the phase change. Effects of the heat flux, fill level and gravity acceleration are investigated. Numerical results indicate that the pressure starts to rise after a certain time of sidewall heating and pressure rises gradually once the vaporization occurs. The rise rate increases as time elapses and is larger at higher heat flux at the same time. Multiple loops are observed in the fluid flow and thermal stratification is developed. The stratification degree is nearly the same for different fill levels at the same heat flux while the pressure rise rate increases as the fill fraction becomes larger. High temperature area appears when the fluid mixing becomes weaker as gravity acceleration decreases. Heat transfer turns to nucleate boiling at the wall from convection as evaporation occurs at the interface.
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Waniczek, P., P. Jeschke, H. Schoenenborn i T. Metzler. "Investigation of the Surge Behavior of a Multi-Stage Axial Compressor With a Multi-Sensor Probe". W ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-46219.
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The surge behavior of the first rotor of an eight-stage aero engine high pressure compressor has been investigated experimentally. For that purpose, a new multi-hole pressure probe was developed and adapted to the axial compressor test rig. Due to the high time resolution measurements (more than 45000 measuring points per surge cycle) it is possible to investigate the dynamic flow field of a surge cycle in a time-accurate manner. The results especially show the complex flow field structure at the surge inception. At the rotor leading edge the flow shows perturbations with high amplitudes and initiates the surge event, whereas the flow at the rotor trailing edge is less influenced. The inflow vector turns around the leading edge of the blade relatively slowly. During that turn around three different characteristic flow conditions have been identified. These are ‘zero rotor turning’, ‘turbine-like flow’ and ‘no flow’. ‘No flow’ means, that the absolute velocity vector reaches a flow angle where it consists of a pure tangential velocity component. That is the point where the reverse flow phase is initiated. A 180° shift of the flow direction at the rotor trailing edge is the consequence. After a quasi-steady reverse flow the acceleration of the flow starts. In total, this paper gives new and fundamental insights into the unsteady flow field phenomena during various surge cycles. Especially the transient velocity vector imparts a good idea of the flow field structure of a surging compressor.
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Xu, Changxue, Zhengyi Zhang, Yong Huang i Heqi Xu. "Phase Diagram of Pinch-Off Behaviors During Drop-on-Demand Inkjetting of Alginate Solutions". W ASME 2019 14th International Manufacturing Science and Engineering Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/msec2019-2915.
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Abstract Viscoelastic polymer solutions have been extensively utilized in drop-wise manufacturing (such as inkjet printing) for a variety of biomedical applications. The pinch-off of viscoelastic jets is a key step towards generation of droplets in inkjet printing. This complex process is governed by interplay of four stresses including inertial stress, capillary stress, viscous stress, and elastic stress. Depending on polymer solution properties and process conditions, four types of pinch-off phenomenon were observed during inkjetting of viscoelastic alginate solutions. In this study, material properties of alginate solutions with different concentrations have been characterized, and three dimensionless numbers (Ohnesorge number Oh, Deborah number De and Weber number We) have been proposed to analyze different pinch-off behaviors. Phase diagram in terms of these three dimensionless numbers has been constructed to classify the regimes for different pinch-off types during inkjetting of viscoelastic alginate solutions. It is found that: 1) At low De and Oh, the viscoelastic effect is small. The capillary stress is mainly balanced by the inertial stress, resulting in front pinching. 2) At medium De and low Oh, the capillary stress is still mainly balanced by the inertial stress, but the elastic effect starts to show its effect by delaying the ligament thinning near the front-pinching location. With the increase of We, the pinch-off type may change from front pinching to hybrid pinching to exit pinching. 3) At low Oh and high De, the viscous and inertial effects are small. The capillary stress is mainly balanced by the elastic stress, resulting in exit pinching. 4) At high Oh and De, the viscoelastic effect is dominant. The capillary stress is mainly balanced by the viscous and elastic stresses. With the increase of We, middle pinching turns to be exit pinching due to the increase of the initial ligament diameter near the forming droplet.
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Fangbo, Jing, Lai Qiang, Wei Dongliang, Chen Xianhui i Yuan Yongqiang. "Economic Analysis for Nozzle Governing With Overload Valve Regulation Technology". W ASME 2017 Power Conference Joint With ICOPE-17 collocated with the ASME 2017 11th International Conference on Energy Sustainability, the ASME 2017 15th International Conference on Fuel Cell Science, Engineering and Technology, and the ASME 2017 Nuclear Forum. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/power-icope2017-3322.
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With the implementation of low-carbon economy policy, clean energy (such as wind and solar energy) has been developing rapidly, and the percentage is increasing year by year; On the other hand, with a steadily growing percentage of residential electricity consumption and commercial electricity consumption, resulting in large electricity load difference between peak and valley, the load related requirements of modern steam power plants are noticeably changing. Whereas the past units being designed in base load now have to take part in peak load, and usually in a low load operation, unable to play its advantages of high efficiency in design load. In the article the current three main governing methods (i.e. nozzle governing, throttling governing and bypass governing) for steam turbine will be discussed and evaluated under economical criteria focused on the above described challenges for future power generating technologies. A new governing method is Nozzle governing with Overload Valve Regulation, which keeps the advantage that main steam pressure of the Nozzle governing steam turbine is higher under partial load conditions, and weakens the influence of the low efficiency of governing stage on high pressure turbine, effectively improves the efficiency of steam turbine unit under partial load conditions. In the turbine adopted the new governing method of Nozzle governing with Overload Valve Regulation, the first stage is governing stage, divided into several groups. Main steam from boiler goes through the main stop valve and main steam control valve in sequence, and then turns to the governing stage. When the load is below 85%THA, main steam control valve I, II and III are fully opened, main steam control valve IV is fully closed, and the unit is in sliding pressure operation. When the load is 85%THA, the main steam pressure can reach the rated pressure. With the load increasing, main steam control valve IV starts to open, but the main steam pressure maintains the rated pressure, adjusted to THA when main steam control valve IV is fully opened and the flowrate of governing stage reaches the maximum. In the load more than THA condition, the bypass valve starts to open, the main steam goes through the bypass steam room into the certain stage (as fourth), to meet the requirements of the super load, adjusted to VWO (about 108%THA) when the bypass valve is fully opened. Through the detailed description about the scheme set and calculation analysis about economy benefit of the new regulation technology of Nozzle governing with Overload Valve Regulation, it shows that with the annual load range of 40%THA–85%THA, the economy of turbine adopted the new regulation technology is better than bypass governing by about 21.6 kJ/kW.h. (CSPE)
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Yin, Yue, LianShui Guo, Ning Han, Ji Zheng i Pengpeng Zhang. "A New Strategy of Cavity Cutting Trajectory Generation in High Speed Machining". W ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-53700.
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High speed machining is widely used in manufacturing. For its high cutting speed, high feeding rate, and high machining accuracy, its requirements for cutting trajectory in high speed machining are so strict that only continuous and smooth trajectories with even cutting loads can lead to high machining efficiency and accuracy. The traditional row or ring machining trajectory fails to meet these requirements. In order to acquire the continuous and smooth machining trajectories, and to avoid load mutation in the machining process, some researchers developed a curvilinear cutting trajectory generating method based on partial differential equation. This trajectory, however, is still made up from free form curve segment, and unable to completely eliminate the effects on smoothness by line segment interpolation, which has a very adverse effect on the efficiency, tool life and machining accuracy. A new strategy to generate a continuous and smooth cavity cutting trajectories in high speed machining is introduced in this article. The new trajectory determines the necessity-nodes from outside (the boundary) to inside in the way of spiral cutting. It starts from the cavity center with spiral expanding, and each cutting loop adopts end connection between straight line and the tangent arc, meeting continuous first-order constraint satisfaction. The smooth trajectory reduces the amplitude and directing mutation of cutting force, thus effectively avoids the impact on the machining efficiency and machining accuracy by speeding down in the corner. The strategy also, by controlling the row space, ensures that there is no cutting residual. A cavity machining programming system based on this strategy is developed on Siemens UG-CAM module. The manufacturing of triangle cavities is studied as a case. It turns out that the new trajectory improves efficiency by 26.23% compared with the traditional one. It ensures a stable operation of the cutting tool in machining, therefore effectively extends the tool life. The main advantages are that the new strategy adopts the geometrical drawing strategy and the trajectories are all made up from the straight lines and the tangent arcs. The trajectory can greatly reduce NC code. It thoroughly removes the effort to mind the smooth, continuity and even cutting load of the tool-path.
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Lockan, Michael, Dieter Bestle, Christian Janke i Marcus Meyer. "Optimization of Coupled System Components Using Approximations of Interface Quantities". W ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-64135.
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Optimization of complex systems like jet engines is a process where discipline experts from several departments or even different companies have to work together. Thus, a complete system analysis code usually does not exist preventing an overall system optimization. Therefore, the system is typically split into components, and interface parameters between components are decided and fixed in early design stages based on low-fidelity information. Finally the components are optimized separately according to these fixed settings which, however, may prohibit an overall optimal system behavior even if sophisticated subsystem optimization is performed. Consequently, interface parameters should be varied in an overall coupled system optimization process and adapted to subsystem needs. This may be supported by utilizing collaborative optimization strategies. Basically there are two types of such optimization approaches: global strategies with nested optimization loops and local subsystem optimization strategies supported by sensitivity-based approximations of other subsystems. The multidisciplinary optimization approach presented here combines the benefits of both strategies: efficient global optimization and approximations of subsystem quantities without the need of sensitivity information. It starts with an initial design of experiments for each component by varying all input parameters and evaluating the associated outputs. Due to the fact that these quantities consist of shared design parameters and outputs of other components, not all of the used input parameter combinations are feasible for the coupled system. In order to enforce consistency for the entire system, the interface regions are characterized by feasibility criteria acting as approximated constraints for further component optimizations. Beside that an approximation of the overall system objective is provided to all components to drive component design towards an overall optimal system performance. The developed approach is demonstrated by an application to a jet engine turbine consisting of a high and low pressure part where the goal is to maximize the overall turbine efficiency. On the one hand the turbine is optimized with the proposed approach by splitting it into two coupled components; on the other hand the turbine is optimized as a complete system. It turns out that the proposed approach yields equally good results in much shorter time than overall optimization.
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Dieu, Donavan, Yves Deletrain, Raphaël Van Liefferinge i Charles Hirsch. "A Strategy for Parameterization and Optimization of Turbine Cooling Channels". W ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-42212.
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Cooled turbine blades represent a major component of gas turbine technology due their potential for enhancing overall cycle performance. Due to the difficulty of performing detailed experiments on these complex internal configurations, the only option is to rely intensively on high fidelity CFD modeling and subsequent optimization to enhance the heat transfer coefficient (HTC) by exploration of a broad design space. The optimization strategy relies on the following steps: parametric modeling of cooling passages; automatic grid generation; validation of the most reliable turbulence models and boundary conditions; optimization process based on genetic algorithms. The parametric blade modeler AutoBlade™ has been upgraded to generate CAD geometries of cooling channels, including ribs, different section shapes, U-turns. From those geometries, the full hexahedral mesher HEXPRESS™ is able to automatically generate high quality unstructured meshes with the possibility to insert viscous sublayers to provide adequate resolution in boundary layer regions. The mesh generator can also deal with multi-domain problems allowing conjugate heat transfer (CHT) method. CFD options were analyzed in order to obtain numerical results as accurate as possible for the optimization process. It appears that low Reynolds grids were necessary to reproduce the thermal effects due to the strong temperature gradient near solid walls. The preconditioning technique seems to be essential for density based flow to obtain realistic results for flows at low Mach number. The anisotropic EARSM turbulence model appears to provide good heat transfer predictions. In addition, the question to include or not CHT is raised: the study also compares the heat transfer obtained in case of imposed static temperature conditions on the coolant to the ones obtained by means of CHT. The results highlight that CHT is more realistic. Optimization of HTC is performed on three baseline configurations by variation of geometric parameters including the aspect ratio of the channel cross section, the shape, position and size of the ribs. The main objective consists in maximization the heat fluxes while limiting the head loss. The optimization process starts from an initial database of high-fidelity CHT simulations obtained by design of experiment methods. To predict a potential optimum, an evolutionary algorithm is run on an artificial neural network for a very quick evaluation of the objectives from the database. The process is iterative: starting from potential candidates, the CFD process is launched to validate the guess and populate the database. Results and optimized geometries will be presented in the full paper.
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Aldana, Andrés F., Helio Sneyder Esteban Villegas i Sebastián Roa Prada. "Iterative Modeling of a Small Underwater Tethered Remotely Operated Vehicle". W ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-88501.
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Remotely operated vehicles, ROV, are highly versatile robotic systems, which are currently the best alternative to carry out deep-sea tasks, that otherwise could compromise the safety of human lives. These vehicles are commonly used by several industries such as offshore oil companies, offshore wind energy companies and environmental organizations. These underwater vehicles may be classified as Free-Swimming Systems, FSS, or Tether Management Systems, TMS. Tether Management Systems use the cable to transmit data and steering commands, and as a mean for power supply. It is known that the cable has a strong influence on the dynamics and maneuverability of a ROV. To improve the motion accuracy and stability of the control of a ROV, it is necessary to understand the nature and to estimate the value of the mutual reaction forces between the ROV and the cable. This research seeks the modeling of the overall underwater tethered vehicle, by iteratively coupling the results from the finite element analysis, FEA, of the cable with the dynamic model of the ROV, as obtained by using the standard Newton-Euler formulation. Morison equation is employed to obtain the cable transient response. In this work, the ROV tether is defined as a flexible, slender cylinder, with circular cross section and made of a material with nonlinear elastic behavior. The cable is assumed to be in a specific extended initial configuration, with one of its ends fixed in ground. The FEA analysis of the cable is performed with the help of the commercial software COMSOL Multiphysics. A commercial small ROV is selected as the case study to apply the Newton-Euler method, considering the location of its actuators and other actual parameters such as mass, matrix of mass moments of inertia and drag coefficients. To include the cable forces into the dynamic model of the ROV, it is necessary to perform an iterative process between the cable analysis results and the ROV open loop response. The modeling approach starts with an FSS system initial velocity, which is fed into the cable FEA analysis. Both analyses are iterated, following a mutual feedback scheme, until results converge, obtaining the complete tethered vehicle model. The main achievement of this investigation is to observe the cable influence on the ROV, providing results that prove to be extremely useful for future work on the control system design, taking into account the disturbances introduced by the cable.
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Yang, Dong, Zhi Shen, Xin Nie, Wanyu Liu, Fengjun Wang i Ying Huang. "Hydraulic Resistance of Subcritical and Supercritical Water Flowing in a Rifled Tube". W ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-65597.
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Large capacity supercritical boiler is at the leading edge of efficiency boost for thermal power plant. Water wall design is a key issue for a supercritical boiler. To ensure successful design and safe operation of water wall, studying hydraulic resistance of water is significant. Considerable work on frictional pressure drop of gas-liquid two-phase flow in tubes has been done and various correlations have been proposed to predict it. However, these correlations are restricted to particular rib geometries and flow conditions. Because of significant variations in thermo physical properties near the critical and pseudo-critical points, pressure drop at supercritical pressures is different from that at subcritical pressures. However, limited studies have been devoted to estimate hydraulic resistance of supercritical water. More work need be conducted to develop prediction method for pressure drop at supercritical pressures. Therefore, to accumulate fundamental experimental data for the design of a supercritical boiler, an experiment on hydraulic resistance of water was performed in a vertical upward rifled tube. The experiment was carried out in the high-temperature and high-pressure steam-water test loop at Xi’an Jiaotong University. Based on the experimental data, the two-phase frictional multiplier was calculated to analyze the two-phase frictional pressure drop. At low to moderate vapor quality, the two-phase frictional multiplier increases rapidly and reaches a peak. When the vapor quality exceeds a certain value, the two-phase frictional multiplier starts to decrease with increasing vapor quality. It is because the tube wall is covered by liquid film at low to moderate vapor quality. Within the high vapor quality region, the high-speed vapor tears the liquid film and the flow pattern turns to mist flow with lower frictional pressure drop. Increasing pressure decreases the two-phase frictional multiplier and when the pressure approaches the critical pressure, the multiplier is close to 1. The effect of mass flux on the multiplier is so weak that it can be neglected. At supercritical pressures, the pressure drops due to frictional resistance and flow acceleration both increase with bulk fluid enthalpy. Increasing pressure decreases the frictional pressure drop. This result is mainly attributed to pressure approaching the critical point. Frictional pressure drop is significantly affected by fluid property variations; in particular, severe density decreases with increasing bulk fluid enthalpy. Acceleration pressure drop increases with decreasing pressure and increasing heat flux. When heat flux increases, the density difference between the inlet and the outlet increases with the same mass flux, which results in a considerable acceleration pressure drop. Decreasing pressure results in a similar acceleration pressure drop variation because of the same reason. The frictional resistance coefficient was calculated to analyze the supercritical frictional pressure drop. In the large specific heat region, the frictional resistance coefficient peaks at a certain enthalpy in the vicinity of the pseudo-critical point, and increasing mass flux reduces the magnitude of the peak value.