Response of seated human subject to ship structure motion caused by the combined effect of shock wave and bubble pulsation

2021 ◽  
pp. 110666
Author(s):  
Yongbo Jiang ◽  
Xiaofei Cao ◽  
Yongzhen Wang ◽  
Cheng Wu ◽  
Ying Li
2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Jihad E. Alqasimi ◽  
Hassen M. Ouakad

This paper focuses on the influence of sudden drop tests on the nonlinear structural behavior of electrically actuated bi-table shallow microelectromechanical system (MEMS) arches. The assumed structure consists of an initially bell-shaped doubly clamped microbeam with a rectangular cross section. The Euler–Bernoulli beam theory is assumed to model the nonlinear structural behavior of the bistable system under the combined effect of both the direct current (DC) actuating load and the shaking waves. Moreover, the structural model takes into account both geometric midplane stretching and electric actuation nonlinear terms. A multimode Galerkin-based decomposition is used to discretize the beam equations to extract a reduced-order model (ROM). The convergence of the ROM simulations are first verified and furthermore compared to published experimental data. A thorough ROM parametric study showed that the effect of increasing the shallow arch initial rise alter drastically the system behavior from undergoing a uninterrupted snap-through motion to a sudden snap-through instability. Moreover, the arch rise relationship with its shock spectrum response (SSR) is investigated and it was concluded that as increasing the rise value can cause the system to collapse under the combined DC and shock wave loadings if the shock wave duration is lower or near the system fundamental natural period. All the presented graphs in this investigation represent some robust numerical approaches and design tools to help MEMS designers in improving both the reliability and efficiency of these bistable-based microdevices under shaking dynamic environments.


2021 ◽  
Vol 66 (1) ◽  
pp. 26-31
Author(s):  
Balázs András-Tövissi ◽  
László Kajtár

If the draught and the radiant thermal asymmetry caused by the warm ceiling appear simultaneously, will women and men be affected in the same way? This research aims to answer this question, by clarifying the understanding of the joint mechanism of action of the two local discomfort factors with the help of instrumental and human subject measurements. The most important result of the present research is identifying that if PPD < 6%, radiant thermal asymmetry varies in the range of 5–15 °C and the draught rate DR = 15% or DR = 25%, then at a given range of the interval men are significantly more dissatisfied with warm ceilings than women; women’s AMV votes are significantly lower than men's; In the case of DR = 15%, the work accuracy of women is significantly higher, while in the case of men, the work accuracy is higher at DR = 25%.


2019 ◽  
Vol 2019 ◽  
pp. 1-19
Author(s):  
Qiusheng Wang ◽  
Shicong Liu ◽  
Haoran Lou

The centrifugal underwater explosion tests and corresponding numerical simulations were carried out to study the laws of shock wave and bubble pulsation. A semiempirical method to determine JWL state equation parameters was given. The influence on numerical results caused by factors such as state equation of water, boundary condition, and mesh size was analyzed by comparing with the centrifugal underwater explosion test results. The results show that the similarity criterion is also suitable in numerical simulation; the shock wave peak pressure calculated by polynomial state equation is smaller than that of shock state equation. However, the maximum bubble radius and the pulsation period calculated by the two equations are almost the same. The maximum bubble radius is mainly affected by the boundary simulating the test model box, and the pulsation period is mainly affected by the artificial cutoff boundary. With the increase of standoff distance of measuring point, the mesh size required for the numerical calculation decreases; the size of the two-dimensional model is recommended to take 1/30 ∼ 1/10 explosion radius. In three-dimensional models, when mesh size is 2 times larger than explosion radius, the bubble motion change in the second pulsation period is not obvious. When mesh size is smaller than 1 time explosive radius, the full period of bubble pulsation can be well simulated, but calculation errors increase slowly and computation time greatly increases, so the three-dimensional mesh size is suggested to take the charge radius. Shock wave peak pressure is basically unaffected by gravity. As the gravity increases, the bubble maximum radius and the first pulsation period both decrease.


2011 ◽  
Author(s):  
Y. Liu ◽  
J. Ding ◽  
B. L. Zhang ◽  
W. H. Chen ◽  
Z. Q. He ◽  
...  

2020 ◽  
Vol 28 (2) ◽  
pp. 43-49
Author(s):  
Balázs András-Tövissi ◽  
László Kajtár

AbstractHuman resources are the most important elements of economic units; thus, the efficiency of human work is of crucial importance. Work efficiency can be achieved only in an environment offering optimal thermal comfort. The present study makes use of human subject experiments in order to investigate the joint effect of draughts and warm ceilings on work performance. During the experiments, 10 thermal environments with 5 radiant thermal asymmetries and 2 draught rates were investigated. The most important outcome of the research is the presentation of the combined effect of a draught and a warm ceiling on work performance.


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