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1.
This paper is concerned with boundary control of a linear distributed parameter bioprocess. Huang's result (Ann. Differential Equations 1(1) (1985) 43) on the spectrum determined growth assumption is applied to prove that the closed-loop system becomes exponentially stable under a certain condition with respect to the feedback gain. Moreover, it is shown that the decay rate of the open-loop system is given by letting the feedback gain tend to zero.  相似文献   
2.
Abstract

The purpose of this study was to clarify factors to perform the hole-entry technique in the backstroke start. A total of 16 well-trained Japanese competitive swimmers were divided into two groups (backstroke specialists and non-specialists) to compare their backstroke start motions. Their backstroke motions were videotaped, and two-dimensional co-ordinates for the swimmers were obtained from the video images using direct linear transformation methods. A non-paired t-test and Mann–Whitney U-test were used to analyse the statistical difference of the kinematic variables between the groups. Backstroke specialists showed a significantly shorter 5 m time (P = 0.009, effect size = –1.54), a significantly higher position of the toe (P = 0.010, effect size = 1.47) at signal and of the hip at toe-off (P = 0.002, effect size = 1.94), a significantly larger hip joint angle at toe-off (P = 0.007, effect size = 1.60) and a significantly higher angular velocities of the hip joints (45–85%; P < 0.05) for the normalised time as compared to that of non-specialists. An earlier initiation of the extension and the maintenance of a higher extension speed at the hip joints were important factors in achieving an arched-back posture, which facilitated and water entrance with a small entry range.  相似文献   
3.
This paper reviews unsteady flow conditions in human swimming and identifies the limitations and future potential of the current methods of analysing unsteady flow. The capability of computational fluid dynamics (CFD) has been extended from approaches assuming steady-state conditions to consideration of unsteady/transient conditions associated with the body motion of a swimmer. However, to predict hydrodynamic forces and the swimmer’s potential speeds accurately, more robust and efficient numerical methods are necessary, coupled with validation procedures, requiring detailed experimental data reflecting local flow. Experimental data obtained by particle image velocimetry (PIV) in this area are limited, because at present observations are restricted to a two-dimensional 1.0 m2 area, though this could be improved if the output range of the associated laser sheet increased. Simulations of human swimming are expected to improve competitive swimming, and our review has identified two important advances relating to understanding the flow conditions affecting performance in front crawl swimming: one is a mechanism for generating unsteady fluid forces, and the other is a theory relating to increased speed and efficiency.  相似文献   
4.
The high quality evaluation of generated summaries is needed if we are to improve automatic summarization systems. Although human evaluation provides better results than automatic evaluation methods, its cost is huge and it is difficult to reproduce the results. Therefore, we need an automatic method that simulates human evaluation if we are to improve our summarization system efficiently. Although automatic evaluation methods have been proposed, they are unreliable when used for individual summaries. To solve this problem, we propose a supervised automatic evaluation method based on a new regression model called the voted regression model (VRM). VRM has two characteristics: (1) model selection based on ‘corrected AIC’ to avoid multicollinearity, (2) voting by the selected models to alleviate the problem of overfitting. Evaluation results obtained for TSC3 and DUC2004 show that our method achieved error reductions of about 17–51% compared with conventional automatic evaluation methods. Moreover, our method obtained the highest correlation coefficients in several different experiments.  相似文献   
5.
This study examines the hand and foot reaction force recorded independently while performing the kick-start technique. Eleven male competitive swimmers performed three trials for the kick-start with maximum effort. Three force platforms (main block, backplate and handgrip) were used to measure reaction forces during starting motion. Force impulses from the hands, front foot and rearfoot were calculated via time integration. During the kick-start, the vertical impulse from the front foot was significantly higher than that from the rearfoot and the horizontal impulse from the rearfoot was significantly higher than that from the front foot. The force impulse from the front foot was dominant for generating vertical take-off velocity and the force impulse from the rearfoot was dominant for horizontal take-off velocity. The kick-start’s shorter block time in comparison to prior measurements of the grab start was explained by the development of horizontal reaction force from the hands and the rearfoot at the beginning of the starting motion.  相似文献   
6.
Surface roughness is an important parameter for ensuring that the dimension of geometry is within the permitted tolerance.The ideal surface roughness is determined by the feed rate and the geometry of the tool.However,several uncontrollable factors including work material factors,tool angle,and machine tool vibration,may also influence surface roughness.The objective of this study was to compare the measured surface roughness (from experiment) to the theoretical surface roughness (from theoretical calculation) and to investigate the surface roughness resulting from two types of insert,‘C’ type and ‘T’ type.The experiment was focused on the turning process,using a lathe machine Colchester 6000.The feed rate was varied within the recommended feed rate range.We found that there were large deviations between the measured and theoretical surface roughness at a low feed rate (0.05 mm/r) from the application of both inserts.A work material factor of AISI D2 steel that affects the chip character is presumably responsible for this phenomenon.Interestingly,at a high feed rate (0.4 mm/r),the ‘C’ type insert resulted in 40% lower roughness compared to the ‘T’ type due to the difference in insert geometry.This study shows that the geometry of an insert may result in a different surface quality at a particular level of feed rate.  相似文献   
7.
在发展中国家和一些有多种文化背景的发达国家里,民族数学已经获得了一定水平的发展动力。另一方面,起源于发达国家的批判性数学教育特别关注民族数学研究的批判性观点。在这种研究中,为了把民族数学和学校数学连接起来,并把它作为教育尝试,批判性数学教育和民族数学之间相辅相成的关系已被详细考虑。因此,为了通过互惠方式加强批判性本质和发展以民族数学为基础的数学教育,一个基础性的框架被建立。  相似文献   
8.
This study addresses the hypothesis that stagnation of soybean yield on the farm can be improved by selection of a physiological trait favoring carbon assimilate partitioning to terminally placed pods versus genotypes having axillary pods at close plant spacing. 13C was fed to source-sink units comprising a leaf, axillary/terminal pods, and petioles at upper and lower positions of the stem axis in two soybean cultivars, namely Shakujo and Enrei, at different densities of populations. The cultivars differ significantly in architecture, Shakujo bearing a few hundreds of pods in close succession to one another in a terminally placed raceme, in contrast to Enrei having axillary racemes. Pod yield per plant was higher in Enrei than in Shakujo at low density, but Shakujo out-yielded Enrei at close spacing. Population density decreased yield per plant and altered the pattern of assimilate partitioning significantly within the plants for both varieties. At high density more assimilates moved to the upper parts at the cost of the lower parts. The terminally placed pods of Shakujo were advantaged to receive assimilates under density stress. No benefit was accrued to pod filling of Enrei, however, under this condition.  相似文献   
9.
The purpose of this study was to analyse stroke phases, arm-leg coordination and trunk motion fluctuation during breaststroke in elite male and female 50, 100 and 200 m events at the 9th FINA World Swimming Championships, Fukuoka 2001. Four phases of the arm stroke and three phases of the leg kick as well as phases of simultaneous arm and leg propulsion and recovery were identified from video of swimmers' motions below the surface. The duration of each phase was expressed as a proportion of the whole stroke cycle. Three measures of the arm-leg coordination, percent simultaneous arm-leg recovery time (%SRT), percent arm lag time (%ALT) and percent simultaneous arm-leg propulsion time (%SPT) were calculated. Mean mid-pool swimming hip velocity (V), stroke rate (SR) and stroke length (SL) were also calculated. In addition, the intra-cycle hip velocity of the swimmers was obtained by cinematographic analysis. The SR decreased and SL increased significantly as the event distance increased. For the arm-leg coordination the %ALT, %SPT and %SRT indicated significant differences between event, gender and performance level. In particular, for increasing event distance and for the higher performing swimmer the lower the %SPT and the higher the %SRT. In addition, the range of the intra-cycle hip velocity fluctuation in the lower performing group was greater than the higher performing group. The non-propulsive phase seems to be a key factor for better performance. The breaststroke swimmers must avoid rapid deceleration during the non-propulsive phase by adopting a low resistance posture and stroking technique.  相似文献   
10.
The purpose of this study was to investigate joint kinetics of the throwing arms and role of trunk motion in skilled elementary school boys during an overarm distance throw. Throwing motions of 42 boys from second, fourth, and sixth grade were videotaped with three high-speed cameras operating at 300 fps. Seven skilled boys from each grade were selected on the basis of throwing distance for three-dimensional kinetic analysis. Joint forces, torques, and torque powers of the throwing arm joints were calculated from reconstructed three-dimensional coordinate data smoothed at cut-off frequencies of 10.5–15 Hz and by the inverse dynamics method. Throwing distance and ball velocity significantly increased with school grade. The angular velocity of elbow extension before ball release increased with school grade, although no significant increase between the grades was observed in peak extension torque of elbow joint. The joint torque power of shoulder internal/external rotation tended to increase with school grade. When teaching the overarm throw, elementary school teachers should observe large backward twisting of trunk during the striding phase and should keep in mind that young children, such as second graders (age 8 years), will be unable to effectively utilise shoulder external/internal rotation during the throwing phase.  相似文献   
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