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绪论

系统和系统科学

系统的定义

现代系统研究开创者贝塔朗菲对系统的定义：

系统是相互作用的多元素的复合体。

该定义的精确说法是

如果一个对象集合中至少有两个可以区分的对象，所有对象按照可以辨认的特有方式相互联系在一起，就称该集合为一个系统。集合中包含的对象成为系统的组成部分（组分），最小的、不需要再细分的组分称为系统的元素或要素。

重点：

1. 至少两个元素——系统的多元性
2. 组成部分相互作用——矛盾的统一

系统的数学描述

\(S=(A,R)\)，其中\(A\)是所有系统元素的集合，\(R\)是所有相关关系的集合

有些系统可能无法用数学描述定义，例如元素无法界定清晰，或关系无法明确表达

操作思路

• 在Web of Science或者其他学术搜索引擎上查找所需要的文献，然后将全体检索结果的信息导出成Excel（包括作者、标题、出版年份、期刊、DOI号等等）
• 以DOI号为检索条件，到Sci-Hub下载文献，将这一过程写成爬虫进行批量处理
  • 导出DOI号序列，写成循环来逐个爬取
  • 以DOI号检索文献，进入下载页面，查找到保存按钮对应的元素，下载到本地
  • 将下载的PDF文件按照自己的标准重命名
• 手动补全无法在Sci-Hub上得到的文献

“白空之下”

对于地球太阳工程（Geoengineering）这一概念的最初印象来自于Under a White Sky这本书。

Geoengineering is not something you can do with a mail-order kit in your kitchen. Still, as world-altering projects go, it looks to be surprisingly easy. The best method for delivering aerosols would probably be via airplane. The plane would need to be capable of reaching an altitude of around sixty thousand feet and of carrying a payload on the order of twenty tons. Researchers who looked into the configuration of such a craft, which they dubbed a Stratospheric Aerosol Injection Lofter, or SAIL, concluded that development costs would run to about \$2.5 billion. This may sound like a lot of money, but it’s only about a tenth of what Airbus spent to develop its “superjumbo” A380, a plane it stopped producing after a dozen years. To deploy a fleet of SAILs would cost another \$20 billion or so per decade. Again, this is nothing to sneeze at, but the world now spends more than three hundred times that amount every year on fossil-fuel subsidies.

戴森球

前天中午得知美赛开奖，怀着忐忑的心态赶紧查了一下。得到了一张Honorable Mention的奖状。虽然算不上什么大奖，但终于给本科阶段的数学建模经历留下了一个印记。之前就一直想着，等到美赛彻底结束之后要开一个纪念帖。几经拖延，现在终于画上了句号。（川宝镇封面doge)

想起比赛交稿截止的前几个小时，北街咖啡的落地窗外面的天已经黑了又白，邻桌同样参赛的小组也已经纷纷交稿离开。而我们却还面临着模型输出结果不能复现的窘境，一遍一遍焦急地等着代码跑出曲线。前有队友等待着给出最终结论的压力，后有DDL步步紧逼，让人心态爆炸——这还不是一般的爆炸，而是当你把一个摔炮丢进水里，闷着“崩”一声的爆炸。等到论文写完，邮件发送成功，人已经累得没有任何释放情绪的压差了，只有残余的压力和咖啡因还仍然迫使神经保持着清醒。回去睡了一觉醒来后仍然恍惚，还在慌张地自言自语“我是不是应该赶紧写introduction了……”

自回归滑动平均模型（Autoregressive moving average model，ARMA）是研究时间序列的重要方法，以由自回归模型（简称AR模型）与移动平均模型（简称MA模型）为基础“混合”构成。用AMRA模型预测了在当前趋势下，未来二十年内全球二氧化碳浓度的变化趋势。

分析过程

数据集：NOAA Earth System Research Laboratories下属的Global Monitoring Laboratory提供的1969年-2022年逐月的二氧化碳浓度变化数据

https://gml.noaa.gov/dv/iadv/graph.php?code=MLO&program=ccgg&type=ts

环境数据分析课程的大作业，主要目的应用一下课上学到的一些数据分析方法。

1. 通过爬虫获取我国沿海海水水质的监测数据；
2. 以散点图直观反映水质类别的分布和随时间变化情况；
3. 将化学需氧量数据转换为正态分布，以海区/省份为分类变量进行单因素方差分析；
4. 将无机氮数据转换为正态分布，用Pearson分析和线性回归分析考察化学需氧量和无机氮数据的相关性；
5. 利用机器学习，从多个污染指标数据预测海区分类。

在很多支持Markdown语法的编辑器（例如Typora, 印象笔记）中，可以通过mermaid代码块的方式，实现流程图、时序图等图表的绘制。它是一种基于 Javascript 的图表和图表工具，提供标记启发的文本定义，以动态创建和修改图表。

以下是除了普通的graph流程图以外，常用的一些mermaid功能。

flowchart绘制流程图

在绘制流程图的时候，将graph替换成flowchart，可以呈现节点之间的曲线连接。比之前生硬的折线段美观很多。同时，flowchart还可以实现不同子图(subgraph)之间的连通，并且允许箭头逆向。相比之下，graph就只能在节点和节点之间按照既定方向相连。

不过官网上显示flowchart仍然是测试版本，功能上可能会有一些欠缺。

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flowchart TD
    c1--标注-->a2
    subgraph one
    	a1-.->a2
    end
    subgraph two
    	b1
    	b2
    end
    subgraph three
    	c1-->c2
    end
    one --> b2
    three --> two
    two --> c2

This is a draft version of course essay from Berkeley Summer Session 2021 (EPS-80).

Introduction

Huge environmental changes in my hometown have taken place for the past two decades of fast economic growth and industrialization, which is seen as a rough miniature of entering the Anthropocene. Using examples from class materials, my own experience and the book Under a White Sky, several key aspects of anthropogenic actions are analyzed briefly, including land use, agriculture, soil remediation and green house gas management. Finally some personal insights and preparations are mentioned.

Main Body

A glimpse of Anthropocene — a localized point of view

While I was going through the class, I kept thinking about what happened to my hometown located in the southeastern part of China. The past two decades had witnessed rapid economic growth, industrialization and urbanization. When I recalled on how the landscapes looked like at the beginning and what it had become, I figured that this process could be seen as a miniature of what we've been through while entering the Anthropocene, which was believed to have been for just a century or two[1]. This miniature might not be accurate enough, because no trans-regional effect was involved in the narrative, and the time period is not long enough to verify the geological traces of anthropogenic impacts. Yet we can still find the relations to what we've discussed in class and what I've read in the book Under the White Sky.

In the early 2000's I used to spend time in the tiny farm of my grandparents, probably the size of half a tennis court. They grew common vegetables like Chinese cabbages and green vegetables, and in spring dug bamboo shoots from a bamboo forest next to the farmland. The agricultural methods were rather old-fashioned and manual — they used a small plough to loosen the soil, sowed seeds by hand, and used animal excrement as fertilizers. I still remember playing with a small hoe while the adults were busy hoeing to get rid of annoying weeds (I tried to do weeding by myself, but it turned out that all I could do was digging holes in bare soils). There was almost no sign of industrialization and machinery, and even the fence was built out of bamboo strips and wires tied together. This tiny farm provided us with lots of cooking ingredients, and was abandoned after my grandparents moved from the old house.