Hanjie's Blog

一只有理想的羊驼

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sudo apt-get install language-pack-zh-hant language-pack-zh-hans
sudo vim /etc/environment

添加：

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LANG="zh_CN.UTF-8"
LANGUAGE="zh_CN:zh:en_US:en"
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sudo dpkg-reconfigure locales

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  1. Sublime安装JavaScript&NodeJS Snippets插件[1]。

  2. Tools - Build System - New Build System，输入[1:1][2]：

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    {
      "cmd": ["/Users/luohanjie/.nvm/versions/node/v4.2.6/bin/node", "$file"],
      "file_regex": "^[ ]*File \"(...*?)\", line ([0-9]*)",
      "selector": "source.js",
      "shell":true,
      "encoding": "utf-8",
      "windows":
        {
        "cmd": ["taskkill /F /IM node.exe", ""],
            "cmd": ["node", "$file"]
        },
      "linux":
        {
            "cmd": ["killall node; node", "$file"]
        },
      "osx":
        {
           "cmd": ["killall node; /Users/luohanjie/.nvm/versions/node/v4.2.6/bin/node $file"]
        }
    }

    注意node的绝对地址。然后保存为Nodejs.sublime-build并且选择Tools - Build System - Nodejs

  3. 建立一个新js文件，输入console.log("ok");, 按Control + B，应该会输出：

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    No matching processes belonging to you were found
    ok
    [Finished in 0.1s]

  1. http://blog.comingx.com/?p=3041 ↩︎ ↩︎

  2. http://www.hacke2.cn/nodeJS-sublime-3/ ↩︎

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角加速度

我们假设质点进行匀速圆周运动，有：$$\left| {\vec {v_1} } \right| = \left| {\vec {v_2} } \right|$$

因为两个绿色区域相似，有：$$\frac{\left| {\vec {\Delta r} } \right|}{\left| {\vec r} \right|} = \frac{\left| {\vec {\Delta v} } \right|}{\left| {\vec v} \right|}$$
因为路程＝速度*时间，当$\theta \to 0$时，有：$$\left| \vec {\Delta r} \right| = \left| {\vec v} \right|\Delta t$$

$$\frac{\left| \overrightarrow {\Delta r} \right|}{\left| \overrightarrow r \right|} = \frac{\left| {\vec v} \right|\Delta t}{\left| {\vec r} \right|} = \frac{\left| {\overrightarrow {\Delta v} } \right|}{\left| {\vec v} \right|}$$

$$\therefore \frac{ {\vec v}^2 \Delta t }{\left| \vec r\right|} = \frac{\left| \vec {\Delta v} \right|}{\Delta t} = \vec a $$

当$t \to 0$时成立。最后有：

$$\vec a = \frac{ {\vec v}^2}{\left| {\vec r} \right|}\overrightarrow n$$

$\overrightarrow n$为法向量，指向圆心；$\vec a$即为向心加速度。