Suchergebnisse

<p>A shaped charge was produced with a wave shaper that can transform dual-mode penetrators by changing the single-point detonation location. Specifically, the theory of denotation wave formation was applied to analyze changes in the liner surface pressure in different initiation situations. An analytical model was established of the projectile explosively formed by denotation at the top of the liner and jetting projectile charge formed by denotation at the center of charge. LS-DYNA finite element simulation software was used to study the effects of the liner configuration parameters on the formation of dual-mode penetrators, and orthogonal optimizing design and simulation calculation was conducted to obtain suitable structural parameters of a uniform-thickness eccentric hemisphere liner. X-ray imaging and penetration experiments were then conducted. The penetration depth of the explosively formed projectile in a steel target was 0.64<em>D</em>_k(the charge diameter),while that of the jetting projectile charge was 2.42<em>D</em>_k when the burst height was approximately 13<em>D</em>_k.</p>

One-only children have long been a research concern and previous studies have consistently found that one-only children posed academic advantages. However, we know very little about why one-only children scored higher in school examinations than their peers with siblings. Parental involvement might be the reason underlies this difference. This study compares the relationship between parental involvement and students' academic achievement in families with only one child and families with more than one child in China. The results indicate that parents with only one child are more involved in their children's learning compared with their counterparts with more than one child. The findings also suggest that parent-child communication and parent-child activities can positively predict one-only children's academic performance, whereas parent-school contact negatively predicts non-only children's academic performance. These findings highlight the complexity and importance of parental involvement in academic achievement and presents implications for future practice.

The outbreak of coronavirus disease 2019 (COVID-19) has been spreading rapidly in China and the Chinese government took a series of policies to control the epidemic. Studies found that severe COVID-19 is characterized by pneumonia, lymphopenia, exhausted lymphocytes and a cytokine storm. Studies have showen that SARS-CoV2 has significant genomic similarity to the severe acute respiratory syndrome (SARS-CoV), which was a pandemic in 2002. More importantly, some diligent measures were used to limit its spread according to the evidence of hospital spread. Therefore, the Public Health Emergency of International Concern (PHEIC) has been established by the World Health Organization (WHO) with strategic objectives for public health to curtail its impact on global health and economy. The purpose of this paper is to review the transmission patterns of the three pneumonia: SARS-CoV2, SARS-CoV, and MERS-CoV. We compare the new characteristics of COVID-19 with those of SARS-CoV and MERS-CoV.

AbstractThis study documents the COVID-19 disease-control measures enacted in rural China and examines the economic and social impacts of these measures. We conducted two rounds of surveys with 726 randomly selected village informants across seven provinces. Strict disease-control measures have been universally enforced and appear to have been successful in limiting disease transmission in rural communities. The infection rate in our sample was 0.001 per cent, a rate that is near the national average outside of Hubei province. None of the villages reported any COVID-19-related deaths. For a full month during the quarantine, the rate of employment of rural workers was essentially zero. Even after the quarantine measures were lifted, nearly 70 per cent of the villagers still were unable to work owing to workplace closures. Although action has been taken to mitigate the potential negative effects, these disease-control measures might have accelerated the inequality between rural and urban households in China.