Analysis of kinematic data and determination of ground reaction force of foot in slow squat

In the present paper, the ground reaction force （GRF） acting on foot in slow squat was determined through a force measuring system, and at the same time, the kinematic data of human squat were obtained by analyzing the photographed image sequences. According to the height and body weight, six healthy volunteers were selected, three men in one group and the other three women in another group, and the fundamental parameters of subjects were recorded, including body weight, height and age, etc. Based on the anatomy characteristics, some markers were placed on the right side of joints. While the subject squatted at slow speed on the force platform, the ground reaction forces on the forefoot and heel for each foot were obtained through calibrated force platform. The analysis results show that the reaction force on heel is greater than that on forefoot, and double feet have nearly constant force. Moreover, from processing and analyzing the synchronously photographed image sequences in squat, the kinematic data of human squat were acquired, including mainly the curves of angle, angular velocity and angular acceleration varied with time for knee, hip and ankle joints in a sagittal plane. The obtained results can offer instructive reference for photographing and analyzing the movements of human bodies, diagnosing some diseases, and establishing in the future appropriate mathematical models for the human motion.

Elliptical distortion of the Milky Way＇s rotation traced by high-mass star-forming regions

The gravitational potential of the Milky Way is non-axisymmetric, caused by a bar or triaxial halo, which dominates elliptical rotation of the Milky Way. Employing a likelihood analysis, we exploit the astrometric data of masers thoroughly and constrain the elliptical rotation of the Galaxy. Masers in high-mass star-forming regions, observed by VLBA, are more distant tracers than stars observed in the optical bandpass, and thus are more appropriate for studying the global feature of the Milky Way＇s rotation. A clear elliptical potential of the Milky Way is detected, with an ellipticity of ε0-0.09 at the Sun, and the ellipticity increases towards the outer disk. The minor axis of the elliptical potential （the major axis of the rotation orbit） is found to be near the Sun with a displacement of -32°. Based on the rotation model assumed for an elliptical potential, we also make a kinematical calibration of the Galactocentric distance of the Sun, which gives R0 = 7.63±0.34 kpc.

Multicolor photometry of the nearby galaxy cluster A119

This paper presents multicolor optical photometry of the nearby galaxy cluster Abell 119 （z = 0.0442） with the Beijing-Arizona-Taiwan-Connecticut system of 15 intermediate bands. Within the BATC field of view of 58＇× 58＇, there are 368 galaxies with known spectroscopic redshifts, including 238 member galaxies （called sample I）. Based on the spectral energy distributions of 1376 galaxies brighter than iBATC ---- 19.5, the photometric redshift technique and the color-magnitude relation of early-type galaxies are applied to select faint member galaxies. As a result, 117 faint galaxies were selected as new member galaxies. Combined with sample I, an enlarged sample （called sample II） of 355 member galaxies is obtained. Spatial distribution and localized velocity structure for two samples demonstrate that A119 is a dynami- cally complex cluster with at least three prominent substructures in the central region within 1 Mpc. A large velocity dispersion for the central clump indicates a merging along the line of sight. No significant evidence for morphology or luminosity segrega- tions is found in either sample. With the PEGASE evolutionary synthesis model, the environmental effect on the properties of star formation is confirmed. Faint galaxies in the low-density region tend to have longer time scales of star formation, smaller mean stellar ages, and lower metallicities in their interstellar medium, which is in agreement with the context of the hierarchical cosmological scenario.