硝酸的不稳定性

[问题由来] 硝酸在中学化学中具有重要的地位,硝酸的化学性质特别是硝酸与铜反应的习题在中学化学书籍中随处可见,但考查硝酸不稳定性的习题却并不多见.硝酸在见光或加热的条件下容易分解成二氧化氮、氧气和水.因为这个反应有其特殊性,笔者根据其反应类型设计分析推断题,并对其产物二氧化氮的体积变化联系化学平衡理论作进一步考查.笔者创作的试题,构思新颖,设问有梯度,注重考查推理方法,有利于考查学生的思维能力.     

冷轧带钢退火粘结缺陷影响因素的研究及控制措施

文章在结合冷轧厂从轧制工艺、退火工艺到平整工艺等生产过程着重进行了时粘结缺陷的研究,目的是找出影响粘结产生的诸多因素,分析这些因素的影响方式及控制方法.     

钢的奥氏体晶粒度试验中影响晶粒大小因素的研究

本文综合了大量文献资料，就钢中酸溶铝含量、加热方式和奥氏体晶粒的显示方法对奥氏体晶粒大小、晶粒粗化温度的影响进行了较详细的分析研究。     

捕捉热传导的轨迹

原实验操作让学生用蜡将火柴棒粘在铁棒上,每根火柴棒与加热点的距离各不相同(铁棒上粘4根火柴,分别为1～4号,1号离加热点最近,4号最远),观察火柴棒落地的先后顺序。设计的意图是离火焰近的1     

金属防火罩

把一小块铁丝窗纱放在蜡烛的火焰上。你会惊讶地看到:火焰只在窗纱的网眼下摇晃,而不会透过网眼去。这是因为,纵横交叉的铁丝吸走了许多热,以致蜡烛的蒸     

微波场中温度分布的二维数值模拟

时域有限差分法是解决电磁场问题的一种有效方法．根据电磁模型和热模型,通过α因子将热模型的时间步长降到和电磁模型时间步长同一数量级,将它们结合给出了微波加热模型．模拟了从四周加载波源来加热材料．并且给出了模拟的结果．     

汤汤水水月子餐

月子里,易于消化、营养丰富的汤汤水水,不仅能促进新妈妈身体的恢复,还有发奶的功效,汤水喝得多了,奶水自然也就源源不断,宝宝也就不怕肚子饿了。     

Zero-voltage switching converter absorbing parasitic parameters for super high frequency induction heating

This paper presents a novel mega-Hz-level super high frequency zero-voltage soft-switching converter for induction heating power supplies. The prominent advantage of this topology is that it can absorb both inductive and capacitive parasitic components in the converter. The switch devices operate in a zero-voltage soft-switching mode. Consequently, the high voltage and high current spikes caused by parasitic inductors or capacitors oscillation do not occur in this circuit, and the high power loss caused by high frequency switching can be greatly reduced. A large value inductor is adopted between the input capacitor and the switches, thus, this novel converter shares the benefits of both voltage-type and current-type circuits simultaneously, and there are no needs of dead time between two switches. The working principles in different modes are introduced. Results of simulation and experiments operated at around 1 MHz frequency verify the validity of parasitic components absorption and show that this convener is competent for super high frequency applications.     

Hydrodynamic coefficients of a simplified floating system of gravity cage in waves

Numerical simulation and experimental tests were carried out to examine the hydrodynamic behaviors of a double-column floating system of gravity cage under wave conditions. A floating system of gravity cage can be treated as a small-sized floating structure when compared with the wavelengths. The main problem in calculating the wave loads on the small-sized floating structure is to obtain the reasonable force coefficients, which may differ from a submerged structure. In this paper, the floating system of gravity cage is simplified to a 2D problem, where the floating system is set symmetrically under wave conditions. The motion equations were deduced under wave conditions and a specific method was proposed to resolve the problem of wave forces acting on a small-sized floating system of gravity cage at water surface. Results of the numerical method were compared with those from model tests and the hydrodynamic coefficients Cn and Cr were studied. It is found that Cn ranges from 0.6 to 1.0 while Cr is between 0.4 and 0.6 in this study. The results are useful for research on the hydrodynamic behavior of the deep-water gravity sea cages.     

微波加热的能量吸收与效率研究

微波加热是一种能有效进行热传导的方法,与传统的“由表及里”的加热方式相比,它具有高温快速节能等特点。微波加热已经在生产、生活中得到了广泛的应用。针对微波加热过程中的功率分布、加热负载所吸收的功率、加热效率的问题做了研究。