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127. STUDY ON STRUCTURAL-ACOUSTIC CHARACTERISTICS OF CYLINDRICAL SHELL BASED ON WAVENUMBER SPECTRUM ANALYSIS METHOD

Author

Guan Huiren, Lou Jingjun, Liu Wenxi, and Zhou Qidou

Subjects
Physics, Mechanical Engineering, wavenumber spectrum, Naval architecture. Shipbuilding. Marine engineering, Shell (structure), structural vibration, VM1-989, Ocean Engineering, Computational physics, radiated noise, Wavenumber, cylindrical shell, thrust bearing supporting system, Spectrum analysis
Abstract

By the finite element method, the structural vibration response is calculated under the action of the axial exciting force and the moment with different distribution form, and then the transfer function of the mean square normal velocity is analyzed. The wavenumber spectrum analysis method is used to separate and quantify the shell vibration in the wavenumber domain, and then the relation between the structural vibration characteristics and the structural wavelength is summarized. It is concluded that the structural vibration and radiated noise can be reduced under the symmetric action of axial exciting force and the moment. Based on the above conclusion, a symmetrical thrust bearing supporting system is designed and the stiffness of the supporting structure in the axial direction is controlled by selecting suitable size of structural members, therefore, the structural vibration and radiated noise of the submarine is reduced significantly.

Published
2021

128. Acute Effects of Virtual Reality Exercise Biking on College Students' Physical Responses.

Author

Zeng, Nan, Liu, Wenxi, Pope, Zachary C., McDonough, Daniel J., and Gao, Zan

Subjects
*CYCLING, *VIRTUAL reality, *COLLEGE students, *RATE of perceived exertion, *BICYCLES
Abstract

Purpose: Current evidence regarding the use of commercially available immersive virtual reality (VR) headsets and compatible VR exercise apparatus in the promotion of individuals' physical activity (PA) is lacking. This exploratory study investigated the acute effects of a VirZoom VR exercise bike (vBike) on college students' physical responses compared to an exergaming bike (eBike) and a traditional stationary exercise bike (tBike). Method: Forty-eight college students (34 females, Xage = 23.58 ± 3.39; XBMI = 23.81 ± 3.57) completed three separate 20-minute cycling sessions on the vBike, eBike, and tBike in a counterbalanced order. Outcomes included rating of perceived exertion (RPE), assessed at 4-minute intervals throughout each cycling session, and overall PA, operationalized as pedal revolution counts (PRC) during each session. Results: Linear models indicated significant group differences between exercise modalities for RPE (F (2,138) = 14.76–27.30, all p <.001, η2 = 0.17–0.27) and PRC (F (2,138) = 74.862, p <.001, η2 = 0.48). Pairwise comparisons revealed that RPE was reported significantly higher at each time point (i.e., 4th minute, 8th minute, 12th minute, 16th minute, and 20th minute) during the tBike session vs. the vBike and eBike sessions (p <.001) and that participants had higher PRC during the vBike session vs. the eBike and tBike sessions (p <.001). Conclusion: A commercially available VR exercise bike would trigger greater overall PA as compared to exergaming and traditional cycling while being perceived less intense. Future intervention studies conducted in real-world settings to determine cause and effect relationship are warranted. [ABSTRACT FROM AUTHOR]

Published
2022
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136. Effects of Physical Activity on Children’s Motor Skill Development: A Systematic Review of Randomized Controlled Trials

Author

McDonough, Daniel J., Liu, Wenxi, and Gao, Zan

Subjects
Article Subject, education
Abstract

Objective. This systematic review synthesized current randomized controlled trials (RCTs) examining casual evidence regarding the effects of traditional and exergaming-based physical activity (PA) interventions on motor skill development in typically developed children (i.e., those aged 6-12 years). Methods. We adhered to the PRISMA-P statement and searched electronic databases (Medline, PsycInfo, Web of Science, PubMed, ERIC, Scopus, and SportDiscus) from inception through July 2020. We screened for peer reviewed RCTs published in English between 2000 and 2020 examining the effect of PA on motor skill development in healthy children. Results. A total of 25 RCTs were included, 20 (80%) of which reported significant improvements in children’s motor skill performance. Specifically, 18 studies examined traditional PA interventions and 7 studies examined exergaming-based PA interventions, 83% and 71% of which observed statistically significant improvements in children’s motor skill development, respectively. Conclusions. Findings support the causal evidence regarding the effects of PA on motor skill development in children. Notable limitations of this review included heterogeneity of measurement protocols and assessment tools used to test children’s motor skills across studies, a wide range of PA intervention dose across studies, and the lack of power analyses and long-term follow-up assessments in individual studies to discern appropriate sample sizes and long-term effectiveness, respectively. To further strengthen the evidence in this emerging field, we advocate for future RCTs to employ a priori power analyses, long-term follow-up measurements, and more exergaming-based interventions to allow for comparisons with traditional PA interventions, to explore the dose response and moderating relationships between PA and motor skill development in childhood, and to utilize homogenous assessment instruments to allow for more rigorous, quantitative syntheses.

Published
2020
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137. Urban Change Detection in TerraSAR Image Using the Difference Method and SAR Coherence Coefficient

Author

HE Shuguang, Zhang Xuedong, Architecture , Beijing , China, and Liu Wenxi

Subjects
010504 meteorology & atmospheric sciences, Computer science, 0211 other engineering and technologies, General Engineering, 02 engineering and technology, 01 natural sciences, lcsh:TA1-2040, Urban change, lcsh:Technology (General), Coherence (signal processing), lcsh:T1-995, lcsh:Engineering (General). Civil engineering (General), 021101 geological & geomatics engineering, 0105 earth and related environmental sciences, Remote sensing
Published
2018

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