It is believed that human ancestors evolved the ability to run bipedally approximately 2 million years ago. This form of locomotion may have been important to our survival and likely has influenced the evolution of ou...It is believed that human ancestors evolved the ability to run bipedally approximately 2 million years ago. This form of locomotion may have been important to our survival and likely has influenced the evolution of our body form. As our bodies have adapted to run, it seems unusual that up to 79% of modern day runners are injured annually. The etiology of these injuries is clearly multifactorial. However, 1 aspect of running that has significantly changed over the past 50 years is the footwear we use. Modern running shoes have become increasingly cushioned and supportive, and have changed the way we run. In particular, they have altered our footstrike pattern from a predominantly forefoot strike(FFS) landing to a predominantly rearfoot strike(RFS) landing. This change alters the way in which the body is loaded and may be contributing to the high rate of injuries runners experience while engaged in an activity for which they were adapted. In this paper, we will examine the benefits of barefoot running(typically an FFS pattern),and compare the lower extremity mechanics between FFS and RFS. The implications of these mechanical differences, in terms of injury, will be discussed. We will then provide evidence to support our contention that FFS provides an optimal mechanical environment for specific foot and ankle structures, such as the heel pad, the plantar fascia, and the Achilles tendon. The importance of footwear will then be addressed, highlighting its interaction with strike pattern on mechanics. This analysis will underscore why footwear matters when assessing mechanics. Finally, proper preparation and safe transition to an FFS pattern in minimal shoes will be emphasized. Through the discussion of the current literature, we will develop a justification for returning to running in the way for which we were adapted to reduce running-related injuries.展开更多
The hard tissues of squid can provide important information for species identification. In this study, we used statolith and beak to identify three squid species including Uroteuthis duvaucelii, Loliolus beka, and U. ...The hard tissues of squid can provide important information for species identification. In this study, we used statolith and beak to identify three squid species including Uroteuthis duvaucelii, Loliolus beka, and U. edulis in the South China Sea. Because of the highly overlapping habitat and similar body morphology of the three squid species, we explored four different ways to identify them, by using statolith, upper beak, lower beak and a combination of statolith and beak. An outline geometric morphometric method and stepwise discriminant analysis were used to evaluate the most suitable method for the identification. We found that the combination of statolith and beak had the highest cross validation rate that was 75.0%, 87.5% and 88.7% for U. duvaucelii, L. beka and U. edulis, respectively. Using two beaks had similar results and the lowest cross validation rate was 60.0%, 50.0%, and 73.7% for the upper beak, 46.9%, 58.5% and 75.3% for the lower beak of U. duvaucelii, L. beka and U. edulis, respectively. Analyzing with the statolith had moderate cross validation which was 72.2%, 80.0%, and 87.7% for U. duvaucelii, L. beka and U. edulis, respectively. From the results it is suggested when the entire body of a squid is available, a combination of statolith and beak should be used for the identification. When only one hard tissue is available, species identification can be subjected to large errors.展开更多
This paper considers the pose synchronization problem of a group of moving rigid bodies under switching topologies where the dwell time of each topology may has no nonzero lower bound. The authors introduce an average...This paper considers the pose synchronization problem of a group of moving rigid bodies under switching topologies where the dwell time of each topology may has no nonzero lower bound. The authors introduce an average dwell time condition to characterize the length of time intervals in which the graphs are connected. By designing distributed control laws of angular velocity and linear velocity,the closed-loop dynamics of multiple rigid bodies with switching topologies can be converted into a hybrid dynamical system. The authors employ the Lyapunov stability theorem, and show that the pose synchronization can be reached under the average dwell time condition. Moreover, the authors investigate the pose synchronization problem of the leader-following model under a similar average dwell time condition. Simulation examples are given to illustrate the results.展开更多
文摘It is believed that human ancestors evolved the ability to run bipedally approximately 2 million years ago. This form of locomotion may have been important to our survival and likely has influenced the evolution of our body form. As our bodies have adapted to run, it seems unusual that up to 79% of modern day runners are injured annually. The etiology of these injuries is clearly multifactorial. However, 1 aspect of running that has significantly changed over the past 50 years is the footwear we use. Modern running shoes have become increasingly cushioned and supportive, and have changed the way we run. In particular, they have altered our footstrike pattern from a predominantly forefoot strike(FFS) landing to a predominantly rearfoot strike(RFS) landing. This change alters the way in which the body is loaded and may be contributing to the high rate of injuries runners experience while engaged in an activity for which they were adapted. In this paper, we will examine the benefits of barefoot running(typically an FFS pattern),and compare the lower extremity mechanics between FFS and RFS. The implications of these mechanical differences, in terms of injury, will be discussed. We will then provide evidence to support our contention that FFS provides an optimal mechanical environment for specific foot and ankle structures, such as the heel pad, the plantar fascia, and the Achilles tendon. The importance of footwear will then be addressed, highlighting its interaction with strike pattern on mechanics. This analysis will underscore why footwear matters when assessing mechanics. Finally, proper preparation and safe transition to an FFS pattern in minimal shoes will be emphasized. Through the discussion of the current literature, we will develop a justification for returning to running in the way for which we were adapted to reduce running-related injuries.
基金the National Natural Science Foundation of China (No. NSFC41476129)the Shanghai Leading Academic Discipline Project (Fisheries Discipline)supported by Shanghai Ocean University International Center for Marine Studies and Shanghai 1000 Talents Program
文摘The hard tissues of squid can provide important information for species identification. In this study, we used statolith and beak to identify three squid species including Uroteuthis duvaucelii, Loliolus beka, and U. edulis in the South China Sea. Because of the highly overlapping habitat and similar body morphology of the three squid species, we explored four different ways to identify them, by using statolith, upper beak, lower beak and a combination of statolith and beak. An outline geometric morphometric method and stepwise discriminant analysis were used to evaluate the most suitable method for the identification. We found that the combination of statolith and beak had the highest cross validation rate that was 75.0%, 87.5% and 88.7% for U. duvaucelii, L. beka and U. edulis, respectively. Using two beaks had similar results and the lowest cross validation rate was 60.0%, 50.0%, and 73.7% for the upper beak, 46.9%, 58.5% and 75.3% for the lower beak of U. duvaucelii, L. beka and U. edulis, respectively. Analyzing with the statolith had moderate cross validation which was 72.2%, 80.0%, and 87.7% for U. duvaucelii, L. beka and U. edulis, respectively. From the results it is suggested when the entire body of a squid is available, a combination of statolith and beak should be used for the identification. When only one hard tissue is available, species identification can be subjected to large errors.
基金supported by the National Natural Science Foundation of China under Grant Nos.61473189 and 61621003the National Key Basic Research Program of China(973 program)under Grant No.2014CB845302
文摘This paper considers the pose synchronization problem of a group of moving rigid bodies under switching topologies where the dwell time of each topology may has no nonzero lower bound. The authors introduce an average dwell time condition to characterize the length of time intervals in which the graphs are connected. By designing distributed control laws of angular velocity and linear velocity,the closed-loop dynamics of multiple rigid bodies with switching topologies can be converted into a hybrid dynamical system. The authors employ the Lyapunov stability theorem, and show that the pose synchronization can be reached under the average dwell time condition. Moreover, the authors investigate the pose synchronization problem of the leader-following model under a similar average dwell time condition. Simulation examples are given to illustrate the results.
