共查询到19条相似文献，搜索用时 818 毫秒
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学完《浮力》一章后，为了提高同学们的解题能力，总结一下计算浮力大小的几种方法是很有七、要的．一、首先弄清楚关于浮力方面的几个术语的含义．1.浸入：指物体正在进入液体的运动过程．此时V排逐渐增大．2．浸没：指整个物体完全处在液面以下，此时V排＝V物，3.上浮：物体在液体内向上的运动过程，条件是F浮＞G物4．下沉：物体在液体内向下运动，条件是F浮＜G物.5．悬浮：物体能够静止停留在液体内的任何地方，此时V排＝V物，F浮＝G物．6．漂浮：指物体静止在液体里时，其中一部分露出水面，此时V排＜V物．F浮＝G物.二、常见的求… 相似文献
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李敬蔚 《中学生数理化(高中版)》2006,(7):96-97
例1，质量为m的物块在粗糙斜面上匀速下滑，下滑过程中斜面保持静止不动．若在物块下滑过程中给物块施加一个竖直向下且过物块重心的力F，如图1所示．则物块的运动情况是（ ）． 相似文献
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计算机模拟微观粒子运动和训练操作技能张定跃一、计算机模拟微观粒子运动＊１．在形成概念的教学过程中模拟微观粒子运动＊学生学习的重要内容之一是形成概念和掌握理论，在＊中学阶段概念的形成必须建立在感性知识的基础上。教学＊大纲指出：“在教学中尽可能通过观察、... 相似文献
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在Visual Basic的集成开发环境下，模拟离地面不同高度的物体的斜抛运动和平抛运动的轨迹，并对抛射体运动的射高、飞行时间和水平射程进行了求解． 相似文献
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本文在介绍如何在Excel中制作自由落体和平抛的同步演示课件．我们可以把在Excel绘图工具中做的彩色小球粘贴在图像控件（Image）中模拟运动质点，设置变量t表示质点的运动时刻，利用图像框控件Image的Left、Top属性（控件与所在窗体的左边或顶边间的距离）来模拟水平、竖直坐标．若每过一个小的时段（比如75ITIS）就让t=t＋0．1递增…，便会形成平抛运动的模拟动画效果．难点在于Excel—VBA中对应的OnTime方法的最小值只有1s．变通的办法是调用Windows的API函数库里的定时器函数SetTime，用来周期性地在指定间隔时间的段尾启用坐标变化过程．[第一段] 相似文献
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光学空间滤波实验的微机模拟演示 总被引：1，自引：0，他引：1
陈城钊 《韩山师范学院学报》2005,26(6):33-36
提出了一种利用MATLAB和C移软件模拟演示空间滤波实验的新方法．用一维黑白光栅作为输入物，设计了能脱离MATLAB运行且界面友好的程序，模拟演示了高通、低通及衬比度反转等实验结果． 相似文献
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陶汉斌 《数理天地(高中版)》2014,(2):32-32
例1如图1所示，水平长传送带始终以速度v匀速运动．现将一质量为m的小物块放于左端（无初速度），最终小物块与传送带一起以速度v运动．在物块由速度为零增加至v的过程中。为传送小物块，电动机需额外做多少功？ 相似文献
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介绍汽车轮毂轴承模拟试验机上使用的监控系统．根据试验大纲，可对应参数进行监控、分析、存储、打印，以达到精确模拟汽车轮毂运动，完成轴承试验的目的。介绍硬件组成的基础上详细介绍使用Borland C Builder5．0进行软件开发的程序实现。 相似文献
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采用小麦幼苗为材料，研究了冷激诱导抗冷性过程中超氧化物歧化酶（SOD），过氧化氢酶（CAT），抗坏血酸专一性过氧化物酶（APX）、愈创木酚过氧化物酶（GPX）四种抗氧化酶活性的变化，结果发现冷激可以提高SOD，CAT，APX，GPX四种抗氧化酶的活性，表明冷激诱导的抗冷性与SOD，CAT，APX，GPX四种抗氧化酶活性增加有关，暗示SOD，CAT，APX，GPX四种抗氧化酶在冷激诱导小麦幼苗抗冷性的形成过程中起重要作用。 相似文献
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Salvianolic acid B(Sal B) is an active component of traditional Chinese medicine Salvia miltiorrhiza and is used to treat vascular diseases. To better understand its mechanism, the antioxidant capacities of Sal B was evaluated with human endothelial cells under oxidative stress. Human endothelial cells were pretreated with Sal B for 12 h followed by hydrogen peroxide for another 12 h. Production of reactive oxygen species (ROS), activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX), and concentration of glu-tathione were measured: Protective effect of Sal B on the endothelial cells from hydrogen peroxide-induced damage ' was observed, and ROS production in the cells was found significantly inhibited. Sal B remarkably enhanced the activities of antioxidant enzymes SOD, CAT and GPX. Furthermore, Sal B up-regulated the intracellular glutathione concentration. The results indicate that Sal B protected endothelial cells from oxidative stress by improving the redox status of the cells through enhancing the antioxidant enzyme activities and increasing the reductive glutathione concentration after the oxidative challenge. 相似文献
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Objective: To estimate the oxidative stress and oxidative damage induced by abnormal free radical reactions in IgA nephropathy (IgAN) patients' bodies. Methods: Seventy-two IgA N patients (IgANP) and 72 healthy adult volunteers (HAV) were enrolled in a random control study design, in which the levels of nitric oxide (NO) in plasma, lipoperoxide (LPO) in plasma and in erythrocytes, and vitamin C (VC), vitamin E (VE) and β-carotene (β-CAR) in plasma as well as the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) in erythrocytes were determined with spectrophotometric mothods. Results: Compared with the HAV group, the averages of NO in plasma, and LPO in plasma and in erythrocytes in the IgANP group were significantly increased (P＜0.0001), while those ofVC, VE and β-CAR in plasma as well as those of SOD, CAT and GPX in erythrocytes in the IgANP group were significantly decreased (P＜0.0001). Linear correlation analysis showed that with the increase of the values of NO, and LPO in plasma and in erythrocytes, and with the decrease of those ofVC, VE, β-CAR,SOD, CAT and GPX in the IgAN patients, the degree of histological damage of tubulointerstitial regions was increased gradually (P＜0.0001); and that with the prolongation of the duration of disease the values of NO, and LPO in plasma and erythrocytes were increased gradually, while those of VC, VE, β-CAR, SOD, CAT and GPX were decreased gradually (P＜0.005). The discriminatory correct rates of the above biochemical parameters reflecting oxidative damage of the IgAN patients were 73.8%-92.5%, and the correct rates for the HAV were 70.0%-91.3% when independent discriminant analysis was used; and the correct rate for the IgAN patients was increased to 98.8%, the correct rate for the HAV was increased to 100% when stepwise discriminant analysis was used. The above biochemical parameters' reliability coefficient (alpha) were used to estimate the oxidative damage of the IgAN patients as 0.8145, the standardized item alpha=0.9730, F=53273.5681, P＜0.0001. Conclusions: A series of free radical chain reactions caused serious pathological aggravation in the IgANP' bodies, thus resulting in oxidative damage in their bodies. In treating IgANP, therefore, it is necessary that suitable dose antioxidants should be supplemented to them so as to alleviate the oxidative damage in their bodies. 相似文献
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对影响数字图书馆的网络安全的因素进行了全面的分析,结合网络安全机制分析了防范技术的应用方法,提出了建立数字图书馆安全保障体系的构想。 相似文献
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探讨临时支撑卸载分析中的两种方法 总被引：1，自引：0，他引：1
目前在工程中,临时支撑卸载过程的分析和模拟主要有两种方法.利用这两种方法分别建立临时支撑卸载的有限元模型并在ANSYS中对这两个模型的卸载过程进行模拟和分析,从理论上和有限元分析结果上对这两种方法进行了探讨. 相似文献
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方长春 《华中师范大学学报(人文社会科学版)》2006,45(3):38-43
二十多年以来,调查研究已经广泛地被国内学者所采用。然而,在调查研究方法不断完善和技术不断提高的同时,人们也开始对调查研究这样一种社会研究方式的局限性有所意识。本文试图从方法论和本土实践两个角度从发,探讨调查研究作为社会研究一种方式的局限性。探讨的目的并不是要否认调查研究作为一种社会研究方式的合理性与必要性,而是希望引起人们对社会研究这一学术活动本身的反思。 相似文献
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袁玉刚 《重庆职业技术学院学报》2008,17(4):133-135
大学生心理问题已成为困扰高校的主要问题之一,运用社会生态理论,采用社会生态干预模式从社会大环境、家庭校园小环境等方面进行干预,能有效地预防和治疗大学生心理问题。 相似文献
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