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关键词： 课堂提问   地理图像   专家型地理教师   视频编码  

摘要： 地理图像是地理教学的核心工具,用图提问是中学地理教师常用的教学方法。本文以7节中学地理优质公开课为研究对象,从数量、频率、地图类型、知识类型、教师反馈等维度分析专家型地理教师用图提问的教学特点。本文通过研究发现,教师用图提问的次数多、频率高,难度适中,形式多样;图像类型以地理景观图和专题地图为主;提问顺序由表及里、由浅入深,注重培养学生的尺度思维;教师反馈方式以引导、点拨为主。基于此,本文从注重地理图像的多样性、重视地理问题的适切性、发挥教学反馈的引导性等方面提出用图教学启示。

关键词： 原词   名词术语   缩略语   金黄色葡萄球菌   文题   括号   金葡菌  

摘要： 文题原则上不能使用缩略语,文中应尽量少用缩略语。公认的缩略语(表1,2)在文中可以直接使用。未公布的名词术语,请按照如下规则进行缩写:原词过长且在文内多次出现者,若为中文可于第一次出现时写出全称,在括号内写出缩略语,如金黄色葡萄球菌(金葡菌)。

关键词： magnesium alloy   gigacasting process   defect   microstructure   process  

摘要： The demand for lightweighting is rapidly increasing to meet the carbon peak and neutrality goals. Gigacasting integrates stamping and welding processes into a single high-pressure die-casting operation, streamlining production workflows and considerably enhancing production efficiency, thereby accelerating advancements in automotive lightweighting. Magnesium alloys, which are the lightest metallic structural materials at present, are superior choices for lightweighting because of their low density, high strength, and excellent casting performance. Magnesium alloy gigacasting has enormous potential for automotive applications, enabling the production of lightweight automotive components with superior mechanical properties. However, this process faces challenges because magnesium alloys' active chemical properties and high susceptibility to hot tearing, combined with their large size, thin wall thickness, and complex geometries, make defects like porosity and hot tearing prevalent. These defects greatly impair the performance of gigacast components. Preventing and mitigating casting defects is critical for improving the yield and quality stability of magnesium alloy gigacastings, thereby facilitating their wide spread application in industries like automotive and aerospace. To address these issues, the causes and control measures for three common defects (porosities, defect bands, and hot tearing) are briefly explored in this study. Progress and challenges in defect control, focusing on melt treatment, alloy development, process optimization, and structural design, are also outlined. This review aims to provide valuable insights into defect control strategies for developing high-performance magnesium alloy gigacastings.

关键词： Nitrogen radiation   Non-equilibrium   Spectral measurement   Shock waves   Shock tube  

摘要： The thermochemical non-equilibrium phenomena encountered by hypersonic vehicles present significant challenges in their design. To investigate the thermochemical reaction flow behind shock waves, the non-equilibrium radiation in the visible range using a shock tube was studied. Experiments were conducted with a shock velocity of 4.7 km/s, using nitrogen at a pressure of 20 Pa. To address measurement difficulties associated with weak radiation, a special square section shock tube with a side length of 380 mm was utilized. A high-speed camera characterized the shock wave's morphology, and a spectrograph and a monochromator captured the radiation. The spectra were analyzed, and the numerical spectra were compared with experimental results, showing a close match. Temperature changes behind the shock wave were obtained and compared with numerical predictions. The findings indicate that the vibrational temperatures are overestimated, while the vibrational relaxation time is likely underestimated, due to the oversimplified portrayals of the non-equilibrium relaxation process in the models. Additionally, both experimental and simulated time-resolved profiles of radiation intensity at specific wavelengths were analyzed. The gathered data aims to enhance computational fluid dynamics codes and radiation models, improving their predictive accuracy. (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)4.7 km/s(sic)20 Pa(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)380 mm(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(si

关键词： 初中   物理   浮力  

摘要： 文章通过详细分析浮力在日常生活、工业生产以及科学研究等领域的具体实例,揭示浮力原理的实际价值和广泛应用.同时结合相关物理规律,对浮力的应用进行深入剖析,以帮助学生更好地理解和掌握这一知识点,培养其运用物理知识解决实际问题的能力.

摘要： 同学们,不久以后,我们就要告别美丽的校园,踏入新的学校,开始新的学习生活了.让我们带着感恩,带着留恋,带着憧憬,准备走进毕业季活动中吧. 先来一起完成活动宣传语吧! 亲爱的同学们,深深浅浅的脚印,写满成长的故事.六年前走进校园的那一张张zhì()嫩的脸庞已经洋溢着自信的阳光,幼小的身躯也如傲竹般坚劲挺拔.