Numerical simulation on ionic wind in circular channels

Ionic wind induced by direct-current corona discharge has attracted considerable interest because of its low energy consumption, low noise emission, flexible designs, and lack of moving parts. The purpose of this study is to investigate the configuration parameters to improve the velocity of the ionic wind. Accordingly, this study develops a three-dimensional(3 D) model of circular tube with multi-needle-to-mesh electrode configurations, in this model, the influences of various parameters were explored,such as the mesh gap, the distribution of needle electrodes, the number of needle electrodes,and the radius of the circular channel. The numerical research results showed that the mesh gap, the distribution of needle electrodes, and the radius of the circular tube significantly affected the velocity of the ionic wind. When mesh gap is 12 mm,which indicates that there is an optimal mesh gap which can enhance the velocity of the ionic wind. What is more, changing the distribution of needle electrodes and increasing the number of needle electrodes can effectively improve the velocity of the ionic wind, the optimum distribution α of needle electrodes is 0.7–0.9, which greatly increase the velocity of the ionic wind. However, for multi-needle-to-mesh structure, the improvement of the radius of the circular channel is conducive to enhance the velocity and improve the velocity distribution.

On the Scalable Fairness and Efficient Active Queue Management of RED

Internet routers generally see packets from a fast flow more often than a slow flow. This suggests that network fairness may be improved without per-flow information. In this paper, we propose a scheme using Most Recently Used List (MRUL)-a list storing statistics of limited active flows that sorted in most recently seen first mode-to improve the fairness of RED. Based on the list, our proposed scheme jointly considers the identification and punish of the fast and unresponsive fast flows, and the protection of slow flows. Its performance improvements are demonstrated with extensive simulations. Different from the previous proposals, the complexity of our proposed scheme is proportional to the size of the MRUL list but not coupled with the queue buffer size or the number of active flows, so it is scalable and suitable for various routers. In addition, another issue we address in this paper is queue management in RED. Specifically, we replace the linear packet dropping function in RED by a judicially designed nonlinear quadratic function, while original RED remains unchanged. We call this new scheme Nonlinear RED, or NLRED. The underlying idea is that, with the proposed nonlinear packet dropping function, packet dropping becomes gentler than RED at light traffic load but more aggressive at heavy load. As a result, at light traffic load, NLRED encourages the router to operate in a range of average queue sizes rather than a fixed one. When the load is heavy and the average queue size approaches the pre-determined maximum threshold (i.e. the queue size may soon get out of control), NLRED allows more aggressive packet dropping to back off from it. Simulations demonstrate that NLRED achieves a higher and more stable throughput than RED and REM. Since NLRED is fully compatible with RED, we can easily upgrade/replace the existing RED implementations by NLRED.

An MDP Based Energy Efficient Transmission Policy for Wireless Terminals

In wireless network, terminals are usually energy constrained. In order to extend the lifetime of the terminal, the limited energy must be utilized in an efficient manner. In this paper, under the constant transmission power scenario, we propose an Energy Efficient Transmission Policy (EETP) which is derived by using Markov Decision Process (MDP). The simulation results show that compared with the Threshold Transmission Policy (TTP), the proposed policy can reduce the energy consumption significantly, while satisfying the performance demand at the same time.

Investigation and analysis of the status of nutritional status of adolescents aged 13-18 in Sanya City

Objective: To analyze the status and distribution characteristics of malnutrition, overweight and obesity among adolescents aged 13-18 years in Sanya City, Hainan Province in 2018, and provide evidence for prevention of adolescent obesity. Methods: A stratified cluster sampling method was used to select 2305 young people aged 13-18 years old in Sanya City, Hainan Province in 2018. The height and weight of the subjects were measured and the body mass index (BMI) was calculated. The 'overweight and obesity screening body weight index classification criteria for Chinese school-age children and adolescents' was used to screen for overweight and obesity rates, and the detection rates of different age groups were analyzed. Results: The malnutrition rate of young people aged 13-18 years in Sanya City was 12.3%, the overweight rate was 10.9%, and the obesity rate was 3.2%. The overweight rates of male and female students were 16.0% and 6.3%, respectively, and the obesity rates for boys and girls were 4.9% and 1.7%, respectively. There were significant differences in the rates of overweight and obesity among adolescents of different genders. Compared with the national students aged 13-18 in 2014, the overweight and obesity rates of boys in the 13-16 age group in Sanya City were higher than those in the same age group in the country, while the overweight and obesity rates of girls in the 13-18 age group were lower than those in the same age group in the country. Conclusion: The overweight and obesity rate of male students aged 13-18 in Sanya City is significantly higher than that of female students. The overweight and obesity rate of boys aged 13-15 years is higher than that of other regions in the country, which is close to the level of developed countries. Obesity prevention and treatment should be listed as the focus of the school health department.

Microstructure and improved mechanical properties of Mo-12Si-8.5B alloys with lanthanum oxide addition

Mo-12 Si-8.5 B alloys with different La2 O3 contents were fabricated by mechanical alloying and then hot pressing.The effects of La2 O3 on microstructure,room and elevated temperature mechanical properties of Mo-12 Si-8.5 B alloys were studied.The microstructure of Mo-12 Si-8.5 B alloy with La2 O3 additions exhibits a continuous α-Mo matrix,where the spherical Mo3 Si and Mo5 SiB2 intermetallic phases are distributed inside the grains and along the grain boundaries.The detailed microstructure shows that some nanoscale La2 O3 particles are dispersed mainly in the a-Mo grains and partially in the intermetallics.These La2 O3 particles can refine the grain sizes of a-Mo matrix and intermetallic,but the refining effect is limited with the La2 O3 addition further increasing.The mechanical testing results show that the La2 O3 addition simultaneously improves the compression strength and fracture toughness of Mo-12 Si-8.5 B alloy,due to that theα-Mo matrix is strengthened and toughened at ambient temperature and intermetallics are strengthened at elevated temperatures.The enhancing effect is sensitive to the amount of La2 O3 additions,and the Mo-12 Si-8.5 B alloy can obtain a better combination of strength and toughness when the content of La2 O3 is 0.9 wt%.