排序方式： 共有26条查询结果，搜索用时 203 毫秒
11.
Nasim Daemi Scott Henning James Gibert Philip Yuya Goodarz Ahmadi 《Sports Engineering》2016,19(1):35-46
This paper seeks to address the implications on putting a golf ball with an off-center mass by analyzing the effect of unbalanced mass of ball on its impact and subsequent rolling. We present the general formulation of a rigid golf ball rolling with slip that is able to transition to rolling friction on an arbitrary surface. Particular attention is given to the effects of the offset center of mass on the golf ball’s path. An experimental setup based on a USGA Stimpmeter is used to calibrate the position of contact point as the ball rolls on the green. The trajectories of the ball due to the mass imbalance were studied by numerically solving the equations of motion during putting. Theoretical predictions show that a mass imbalance has little effect on the launch conditions of the ball. However, on a level green a mass offset center of 0.2 % of the ball’s radius can impact the path of the ball with the consequences of missing the hole in a 5.8 m putt. Changing golf ball trajectories with mass offset center has implications on the development of balls and putting. 相似文献
12.
This paper examines three methods to measure the upper arm rotation, the main contributor to produce a fast first serve in
tennis. Accepted videography techniques were compared with a novel inertial gyroscope system and marker-based technique. A
network of two inertial sensors on the upper arm and the chest was used to measure upper arm rotation angle and remove body
artifacts. A marker-based virtual gyroscope (MBVG) was derived from Vicon marker positions in the standard Plug-in-Gait model
using a vector-based method of marker trajectories and a series of geometric transformations. The results indicate that there
is a close temporal feature match for all three methods when applied to the tennis serve. This paper shows that gyroscopes
as well as the MBVG can be advantageous for tennis serve assessment. 相似文献
13.
Matthew N. Ahmadi Karin A. Pfeiffer Stewart G. Trost 《Measurement in physical education and exercise science》2020,24(2):129-136
ABSTRACTThis study developed and evaluated machine learning algorithms to predict children’s physical activity category from raw accelerometer data collected at the hip. Fifty participants (mean age = 13.9 ± 3.0 y) completed 12 activity trials that were categorized into 5 categories: sedentary (SED), light household activities and games (LHHAG), moderate-vigorous games and sports (MVGS), walking (WALK), and running (RUN). Random Forest (RF) and Logistic Regression (LR) classifiers were trained with features extracted from the vector magnitude using 10?s non-overlapping windows. Classification accuracy was evaluated using leave-one-subject-out cross validation. Overall accuracy for the RF and LR classifiers was 95.7% and 94.3%, respectively. Classification accuracy was excellent for SED (96.3% – 98.1%), LHHAG (92.3% – 95.2%), WALK (94.5% – 97.1%), RUN (99.5% – 99.6%); and MVGS (87.5% – 92.7%). The results indicate that classifiers trained on features in the raw acceleration from the hip can be used for activity recognition in young people.Abbreviations: VM: Vector Magnitude; RF: Random Forest; LR: Logistic Regression; LOSO: Leave-One-Subject-Out 相似文献
14.
Matthew N. Ahmadi Nicole Nathan Rachel Sutherland Luke Wolfenden Stewart G. Trost 《Journal of sports sciences》2020,38(4):399-404
ABSTRACTDetection of non-wear periods is an important step in accelerometer data processing. This study evaluated five non-wear detection algorithms for wrist accelerometer data and two rules for non-wear detection when non-wear and sleep algorithms are implemented in parallel. Non-wear algorithms were based on the standard deviation (SD), the high-pass filtered acceleration, or tilt angle. Rules for differentiating sleep from non-wear consisted of an override rule in which any overlap between non-wear and sleep was deemed non-wear; and a 75% rule in which non-wear periods were deemed sleep if the duration was < 75% of the sleep period. Non-wear algorithms were evaluated in 47 children who wore an ActiGraph GT3X+ accelerometer during school hours for 5 days. Rules for differentiating sleep from non-wear were evaluated in 15 adults who wore a GeneActiv Original accelerometer continuously for 24 hours. Classification accuracy for the non-wear algorithms ranged between 0.86–0.95, with the SD of the vector magnitude providing the best performance. The override rule misclassified 37.1 minutes of sleep as non-wear, while the 75% rule resulted in no misclassification. Non-wear algorithms based on the SD of the acceleration signal can effectively detect non-wear periods, while application of the 75% rule can effectively differentiate sleep from non-wear when examined concurrently. 相似文献
15.
The evolvable multiprocessor （EvoMP）, as a novel multiprocessor system-on-chip （MPSoC） machine with evolvable task decomposition and scheduling, claims a major feature of low-cost and efficient fault tolerance. Non-centralized control and adaptive distribution of the program among the available processors are two major capabilities of this platform, which remarkably help to achieve an efficient fault tolerance scheme. This letter presents the operational as well as architectural details of this fault tolerance scheme. In this method, when a processor becomes faulty, it will be eliminated of contribution in program execution in remaining run-time. This method also utilizes dynamic rescheduling capability of the system to achieve the maximum possible efficiency after processor reduction. The results confirm the efficiency and remarkable advantages of the proposed approach over common redundancy based techniques in similar systems. 相似文献
16.
作为高等教育网络学习中心的帕亚米·努尔大学应该采取措施来建立质量管理系统.并且改革或改变教育服务的机构.在2005～2006年帕亚米·努尔大学中心组织使用EFQM模型作了自我评估,目的是为了建立质量管理系统.为了重新评估该组织,为了通过比较连续两年的成绩来监控该组织发挥作用的效果、为了检测去年进行的第一次试验结果的不足的改进程度,我们又进行了第二次试验,题目相同,试验方法稍作更改.试验的主要目的是为了重新评估该组织通过使用EFQM模型后如何提高了自己的作用并比较这两次试验的结果.本实验除了进行文献搜索以外,还进行了实地调查. 相似文献
17.
Drawing on sociocultural theory, and a large number of empirical studies conducted on the effectiveness of scaffolding on second or foreign language learning, the authors investigated the application of different forms of scaffolding to improve listening comprehension of the Iranian intermediate English as a foreign language (EFL) learners. To this end, 90 intermediate EFL learners were randomly assigned to 2 experimental groups and a control group. During 15 treatment sessions of listening comprehension instruction, expert peers in the first experimental group assisted their less knowledgeable peers in their listening comprehension tasks. The participants in the second experimental group were asked to assist their coequal peers while doing the listening comprehension tasks, but the participants in group 3 did not interact with each other or even their teacher and no scaffolding scheme was used when they were doing the listening comprehension tasks. One-way analysis of variance and post hoc analyses revealed that the expert peers' scaffolding was the most effective procedure for the intermediate EFL learners' listening comprehension development. Furthermore, coequal peers' scaffolding was proved to be the second effective procedure for the listening comprehension improvement. The findings underscore the relative efficacy of different forms of scaffolding procedure and the superiority of the expert peers' scaffolding over coequals' scaffolding. The qualitative analysis of the recorded data indicated that the implicit scaffolding strategies were more frequently used by the expert peers. However, the explicit scaffolding strategies were more frequently used to by the coequals. The findings of the study underscore the positive potentiality of scaffolding in its different forms for the EFL learners' listening comprehension development. 相似文献
18.
V. Ramachandran C.S. Gargour M. Ahmadi M.T.H. Boraie 《Journal of The Franklin Institute》1984,318(6):407-413
In this paper we present an alternative approach to the direct design of 1-D recursive digital filters satisfying prescribed magnitude specifications with or without constant group delay characteristic. This method uses an iterative method to calculate the coefficients of the filter's transfer function and guarantees the stability of the designed filter using a new stability test reported by Ramachandran and Gargour. To illustrate the usefulness of the technique, examples are given. 相似文献
19.
M. H. Meshkibaf A. Ebrahimi R. Ghodsi A. Ahmadi 《Indian journal of clinical biochemistry : IJCB》2006,21(1):161-164
A number of newly developed antiepileptic drugs are currently in use, among them Lamotrigine (LTG) is more common. Despite
the extensive use of this drug, it has not been possible to predict the side effects especially the hepatotoxic reactions
after long-term treatment. The present study was designed to find out alterations in the activities of liver enzymes after
chronic exposure of rats to different dose of LTG. Adults male (Wistar) rats were treated orally with LTG [5 mg/kg body weight
or 25 mg/kg body wt.] for 60 days. After the experimental period, auto analyzer carried out liver function tests. The liver
histopathology was obtained after scarifying the rats. There was a significant increase in the level of ALP, AST, ALT and
bilirubin at therapeutic dose of LTG. The increase level of these enzymes and bilirubin at toxic dose were much higher and
significant. However, the total protein and albumin significantly decreased at toxic dose of LTG. Elevation of liver enzymes
and bilirubin after chronic exposure of rats to high dose of LTG reflects hepatocellular damage that may lead to hepatitis.
It is concluded that regular liver function and drug monitoring should follow the treatment with LTG. 相似文献
20.
The stability of stochastic chemical system is considered. The definitions of almost sure stability and mean square stability and the corresponding stability theorems are presented and discussed. Examples concerning the stability of a two tank water heating system and a well-stirred reactor tank with random flows are studied in detail. 相似文献