Auto clustering of the variety of pulse signals based on their symbolic description

In a number of applied studies of geophysics, medicine, cosmophysics, atomic physics and other fields of knowledge, useful information is often hidden in the character of the behavior of a stream of frequency modulated pulses, which are represented by a large variety of forms, significantly different from each other up to several orders value of magnitude amplitude and durations. Noise is often present in the signal. Under these conditions, the problem arises of identifying both individual pulses and groups of pulses to assess the connection between their dynamic characteristics and the state of system. To solve the problem by a method is proposed that includes signal cleaning from interference, the operation of extracting and converting pulses into a code representing a sequence of invariant amplitude and time transformations of similar pulses combined by a single graphic pattern called “symbol”. All symbols extracted from the signal make up the alphabet. A procedure for narrowing the dimension of the alphabet is shown, which allows you to automatically divide it into clusters according to the degree of coincidence of the code. The results of the practical application of the developed method for the selection of base classes of the geoacoustic emission (GAS) signals related to the objective data of the state of the signal-generating medium are presented. The study used data from the archives of observations IKIR FEB RAS.

Training Shoes do not Decrease the Negative Work of the Lower Extremity Joints

Different types of running shoes may have different influence on the negative work of each lower extremity joint. Clarifying this influence can reduce the potential risk of muscle injury. The present study examined the difference in the negative work and associated kinetic and kinematic parameters of the lower extremity joints between training shoes and racing flats during the contact phase of running. Participants were asked to run on a runway at a speed of 3.0 m·s-1 for both training shoes and racing flats. The negative work and associated kinetic and kinematic parameters of each lower extremity joint were calculated. No difference was found in the negative work of the hip and ankle joints between the two types of running shoes. Meanwhile, the negative work of the knee joint was significantly greater for training shoes than for racing flats. This aspect was related to a longer duration of the negative power of the knee joint with the invariant amplitude of the negative power, moment, and angular velocity. These results suggest a higher potential risk of muscle injury around the knee joint for training shoes than for racing flats.