Identification of line-source transfer mobility and force density by ground acceleration measurements.

Ground-borne vibration caused by railway traffic has been a research concern due to its possible side effects on nearby residences. The force density and line-source mobility can effectively characterize the generation and transmission of train-induced vibrations, respectively. This research proposed a frequency-domain method for identifying the line-source transfer mobility and force density using measured vibrations at the ground surface, which was on the basis of the least-square method. The proposed method was applied to a case study at Shenzhen Metro in China, where a total of seven fixed-point hammer impacts with 3.3 m equal intervals were used to represent the train vibration excitations. Line-source transfer mobility of the site and force density levels of the metro train were identified, respectively. Causes for different dominant frequencies can be traced by separating the dynamic characteristics of vibration excitation and transmission. It was found in the case study that at a location 3 m away from the track, the peak at 50 Hz was caused by excitations, while that at 63 Hz was attributed to transmission efficiency related to the soil properties. Subsequently, numerical validations of the fixed-point loads' assumption and identified force density levels were carried out. Good comparisons between numerically predicted and experimentally identified force density levels indicated the feasibility of the proposed method. At last, the identified line-source transfer mobility and force density levels were applied to the forward problem, i.e., making predictions of train-induced vibrations. The predicted ground and structural vibrations at different locations were compared to corresponding measurements, with good agreement, which experimentally validated the identification method. The identification results of the case study can be employed by similar railway systems as a good reference.

Optimization of Data Acquisition Link of University Students' Physical Health Testing System.

University students' physical health test is an important part of university physical education. The data obtained by the physical health test play an extremely important role in the field of students' physical health research. This paper clarifies the current situation of data collection of the physical health test for college students by sorting out the development status and trend of the physical health test system in China. To further ensure the accuracy and validity of the physical health test data, this article puts forward the corresponding optimization measures for the data collection link of the existing physical health testing system given the problems existing in the implementation of university students' physical health tests. Optimization measures are as follows: (1) add a test data collection type for test video collection; (2) optimize the authentication process to increase face recognition; and (3) enhance posttest test data management by stamping time.