Educational Friction: Striated Routes, Transition Velocity, and Value Recuperation among Singaporean Private Degree Students

2018 ◽  
Vol 39 (6) ◽  
pp. 642-657 ◽  
Author(s):  
Yi’En Cheng
Keyword(s):  
Materials ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 1
Author(s):  
Miao Sun ◽  
Wuxiong Cao ◽  
Diqi Hu ◽  
Nana Zhang ◽  
Runqiang Chi

The interface defeat and dwell can effectively improve the ballistic performance of ceramic armors under high velocity impact of long rod projectiles. Confinement conditions along both axial and radial directions of ceramic armors can affect these behaviors. With the aim of giving an insight into the effect of cover plate thickness and connection mode of cover plates with confining tubes on these behaviors, numerical simulations were performed in which the confined silicon carbide (SiC) targets with cover plates were impacted by tungsten rods. The pressure on the surfaces of SiC targets with fixed cover plates are compared to that with free cover plates, showing that the plates fixed with the confining tubes can produce higher pressure by way of wedging. With the increase in cover plate thickness, the dwell duration of the tungsten rods on the ceramic interface gradually grows. In addition, the upper and lower limits of transition impact velocities for the SiC targets with cover plates in different connection modes (i.e., free or fixed) were obtained and analyzed. The results show that the increase rate of the transition velocity region for the cover plate with the fixed-mode is relatively stable and lower than with the free-mode. On this basis, the fixed cover plate contributes higher ballistic performances to the SiC target than the free cover plate. It is also noteworthy that the size of transition velocity region does not enlarge linearly with the increase in cover plate thickness due to the slow growth of the upper limit. Accordingly, thickness thresholds exist, which are 5 mm and 6 mm for the fixed and free cover plates, respectively. Considering the ballistic performance and economy, the cover plate with the thickness ranging from 3 mm to 5 mm, i.e., 1.5~2.5 times of the tungsten rod diameter, is ideal for the structural dimensions in this paper.


2021 ◽  
Vol 165 ◽  
pp. 409-425
Author(s):  
Stoyan Nedeltchev ◽  
Friedemann Mörs ◽  
Adam Mühlbauer ◽  
Mark W. Hlawitschka ◽  
Frank Graf ◽  
...  

Author(s):  
Bjørn Harald Olstad ◽  
Henrik Wathne ◽  
Tomohiro Gonjo

Background and aim: To identify kinematic variables related to short course 100 m breaststroke performance. Methods: An automatic race analysis system was utilized to obtain start (0–15 m), turn (5 m before the wall until 10 m out), finish (95–100 m), and clean swimming (the rest of the race) segment times as well as cycle rate and cycle length during each swimming cycle from 15 male swimmers during a 100 m breaststroke race. A bivariate correlation and a partial correlation were employed to assess the relationship between each variable and swimming time. Results: Turns were the largest time contributor to the finishing time (44.30 ± 0.58%), followed by clean swimming (38.93 ± 0.50%), start (11.39 ± 0.22%), and finish (5.36 ± 0.18%). The finishing time was correlated (p < 0.001) with start segment time (r = 0.979), clean swimming time (r = 0.940), and 10 m turn-out time (r = 0.829). The clean swimming time was associated with the finishing time, but cycle rate and cycle length were not. In both start and turns, the peak velocity (i.e., take-off and push-off velocity) and the transition velocity were related to the segment time (r ≤ −0.673, p ≤ 0.006). Conclusions: Breaststroke training should focus on: (I) 15 m start with generating high take-off velocity, (II) improving clean swimming velocity by finding an optimal balance between cycle length and rate, (III) 10 m turn-out with maintaining a strong wall push-off, and (IV) establishing a high transition velocity from underwater to surface swimming.


2013 ◽  
Vol 819 ◽  
pp. 398-403
Author(s):  
Yue Zhang ◽  
Qing Jian Liu ◽  
Lu Liu ◽  
Tai Yong Wang

In order to obtain better speed and high accuracy, real-time curve fitting and fitting processing at transition points are often necessary when machining complex contours. Based on the quadratic trigonometric Bézier curve, a new algorithm is presented to realize curve fitting only between transition segments. This method ensures the machining precision and increases the maximum allowable speed at the transition points. Simulation and experiment results show that the transition velocity changes smoothly and steadily as well as the processing efficiency is promoted.


Polymers ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 855 ◽  
Author(s):  
Bin Huang ◽  
Xinyu Hu ◽  
Cheng Fu ◽  
Chongjiang Liu ◽  
Ying Wang ◽  
...  

In order to solve the problem of the low production degree of oil layers caused by an excessively large permeability difference between layers during polymer flooding, we propose partial pressure injection technology using a partial pressure tool. The partial pressure tool controls the injection pressure of a polymer solution through a throttling effect to improve the oil displacement effect in high- and low-permeability reservoirs. In order to analyze the influence of the partial pressure tool on the rheological property of the polymer solution, a physical model of the tool is established, the rheological equation of the polymer solution in the partial pressure tool is established according to force balance analysis, the transition velocity equation for the polymer solution is established based on the concept of stability factor, and the influence of varying the structural parameters of the partial pressure tool on the rheological property of the polymer solution is analyzed. The results show that the pressure drop of the polymer solution increases with the decrease of the front groove angle of the partial pressure tool (from 60° to 30°), reaching a maximum of 1.77 MPa at a front groove angle of 30°. Additionally, the pressure drop of the polymer solution increases with the decrease of the outer cylinder radius (from 25 to 24 mm), reaching a maximum of 1.32 MPa at a radius of 24 mm. However, the apparent viscosity of the polymer solution before and after flowing through the partial pressure tool does not change for any of the studied parameters. These research results are of great significance to research on partial pressure injection technology and enhanced oil recovery.


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