想必初中是我过去及将来很长一段人生中文思的顶峰时期,那时,脱离了没有运用文字能力的小学时期,又还未受高考应试教育套路限制,最为幸运与巧妙的是,初中时我所遇到的语文老师们都很乐意我们放开了思维去作文。

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其他人自然也或多或少地察觉到那三人的怪异,但在这奇异之地为了不打草惊蛇都选择了沉默,大厅里只剩下他们三人喋喋不休,颇有一种狂热信徒的模样。

突然,三人一齐停住了声音,大厅里再没有一点声音。人们抬头疑看三人,三人惊凝盒子剩下的那个没有被人进入的角。一开始人们也没看出什么奇怪之处,直到靠近那角的某人扑通倒地,人们感受到了从盒角不断弥散的黑色波浪。

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尔斯有凶,名僮狰,群居以存,有度人化己之能。

代代相争,新必讨旧,无异代共存之道。

作驯兽以助态近人,善久和以温吞,食民脂民膏,啖鱼肉百姓。

天下之人得之必诛,然兽善伪,人为兽操以无力。

兽法尔斯,虽数聚人力群起讨兽,形灭,魄能人以续。

人兽疲,默通规:兽止猖,人从兽,兽为食,人为己。

久之,人以化兽为大道,兽乐以食无尽,人乐以疲无尽。

一般形式的计算

基础公式

图 1 比例 - 微分控制系统结构图

由图 1 可计算出系统的开环传递函数

$$G (s) = \frac {C (s)}{E (s)} = \frac {K\left (T_{d} s+1\right)}{s\left [s /\left (2 \zeta \omega_{n}\right)+1\right]} \tag {1.1}$$

其中 $K=\frac {\omega _{n} }{2\zeta } $ ,称为开环增益。

令 $z=\frac {1}{T_{d} } $ ,则闭环传递函数为

$$\Phi (s)=\frac {\omega_{n}^{2}}{z} \cdot \frac {s+z}{s^{2}+2 \zeta_{d} \omega_{n} s+\omega_{n}^{2}} \tag {1.2}$$

其中

$$\zeta_{d}=\zeta+\frac {\omega_{n}}{2z} \tag {1.2.1}$$

输入阶跃响应,由式 (1.2) 得

$$C (s)=\frac {\omega_{n}^{2}}{s\left (s^{2}+2 \zeta_{d} \omega_{n} s+\omega_{n}^{2}\right)}+\frac {1}{z} \frac {s \omega_{n}^{2}}{s\left (s^{2}+2 \zeta_{d} \omega_{n} s+\omega_{n}^{2}\right)} \tag {1.3}$$

对式 (1.3) 拉氏反变换,并令 $\zeta_{d} < 1 $ ,得单位阶跃响应

$$c (t)=1+r \mathrm {e}^{-\zeta_{d} \omega_{n} t} \sin \left (\omega_{n} \sqrt {1-\zeta_{d}^{2}} t+\psi\right) \tag {1.4}$$

其中

$$r=\sqrt {z^{2}-2 \zeta_{d} \omega_{n} z+\omega_{n}^{2}} /\left (z \sqrt {1-\zeta_{d}^{2}}\right) \tag {1.5}$$

$$\psi=-\pi+\arctan \left [\omega_{n} \sqrt {1-\zeta_{d}^{2}} /\left (z-\zeta_{d} \omega_{n}\right)\right]+\arctan \left (\sqrt {1-\zeta_{d}^{2}} / \zeta_{d}\right) \tag {1.6}$$

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What is in the box?

大厅的正中央放了一个大得离奇的 “盒子”,占地有一个足球场大,有六层楼高。“请不要打开这个盒子”,当我们看向这个物体时,脑海里闪出这样一个念头。

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To: cheems of the future…

Hello, long time no see.

I am the past you.

When you think of this letter…

You should be an adult.

Have you fulfiled our dream?

Or, not done by life?

I don’t know.

But, cheems…

Never stop chasing.

I know it may be difficult…

Even if I tried hard, the flame of hope can’t be lit.

But, cheems…

If one day…

I give up.

Bury our dreams..

Well, no matter how many times.

Please must held your courage again…

Pick up your shovel again and dig out the dream again!

Our stories should not be buried deep in the ground…

But should store in the sky!

No matter how many times we’ve been knocked down,

don’t forget the power of dreams.

Go to the end of the Earth.

But it’s not just the end of the Earth…

To see the endless wilderness,

go and see the mountains stretching thousands of miles,

go and see the waterfall flowing straight down,

go and see the clear and clean lake,

no why, just because I wanted to go.

Isn’t that the best life?

—— 摘录自:清竹莫叶 ( bilibili ) :“cheems,你要去码头整点薯条吗?”

New York is 3 hours ahead of California,

but it does not make California slow.

Someone graduated at the age of 22,

but waited 5 years before securing a good job!

Someone became a CEO at 25,and died at 50.

While another became a CEO at 50,and lived to 90 years.

Someone is still single,while someone else got married.

Obama retires at 55,but Trump starts at 70.

Absolutely everyone in this world works based on their Time Zone.

People around you might seem to go ahead of you,

some might seem to be behind you.

But everyone is running their own RACE, in their own TIME.

Don’t envy them or mock them.

They are in their TIME ZONE, and you are in yours!

Life is about waiting for the right moment to act.

So, RELAX.

You’re not LATE. You’re not EARLY.

You are very much ON TIME, and in your, TIME ZONE Destiny set up for you.

—— Marie-Claire Kuja: You’re Not Late! You’re Not Early