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\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}
\usepackage[T1]{fontenc}
\usepackage{physics}
\usepackage{lmodern}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage[version=3]{mhchem}
\usepackage{subcaption}
\usepackage{float}
\usepackage{xcolor}
\usepackage[section]{placeins}
\usepackage[normalem]{ulem}
\usepackage{gensymb}
\usepackage{mathrsfs}
\usepackage[tmargin=20mm, bmargin=20mm]{geometry}
\usepackage{lipsum}
\newcommand{\vect}[1]{\boldsymbol{1}}
\usepackage{parskip}
\usepackage{graphicx}
\usepackage[font={small, it}]{caption}
\usepackage{siunitx}
\usepackage{float}
\usepackage{babel}
\usepackage{mhchem}
\usepackage{dblfloatfix}
\usepackage{multicol}
\floatstyle{plaintop}
\restylefloat{table}


\title{Semester assignment 241}
\author{Some guy}
\date{April 2019}


\begin{document}

\maketitle
\vspace{2em}
\begin{multicols}{2}
\raggedright


\section*{Introduction}
As the world's demand for power increases, so does the need for lower carbon emissions. The way the world is going today, it does not seem like humanity will be able to keep their ''two degree'' goal. By using renewable energy, one can both lower emissions and increase power generation. But some issues renewable energy face are that they often take up a large area, and that they can be inconsistent. The sun isn't always shining, the wind isn't always blowing and the dams are reliant on regular precipitation. 

Then there are nuclear power plants, which produce large amounts of power with no release of CO$_2$. Fission reactors produce about 11\% of the worlds power \cite{worldnuclear}. Relative to carbon emissions, they are good for the environment, but they have one major drawback, which is the nuclear waste left behind. The nuclear waste can stay radioactive for hundreds of years, and needs the be treated and stored in a special way.

But in the last 10 years, a new kind of nuclear reactor has been looking more promising, and that is the fusion reactor. They have the possibility of producing even more energy, but without any nuclear waste or carbon emissions. The main difference between fission and fusion is that fission is about splitting atoms into lighter ones, while fusion is about fusing atoms into heavier ones.

On the basis of this, one can raise the question: Can fusion power plants replace fission power plants if nuclear fusion becomes feasible?

\section*{Theory}

One of the most interesting aspects of fusion reactors, is the potential amount of fuel available, and the theoretical amount of power it can produce. If you look at the amount of energy produced by fission of \ce{^{235}_{92}U}, its about 200 MeV, which is 0.85 MeV/u \cite{lecture}. Fusion on the other hand, produces a lot more energy.
\begin{equation}
    \ce{^{2}_{1}H} + \ce{^{3}_{1}H} \xrightarrow{} \ce{^{4}_{2}He} + \ce{^{1}_{0}n}  \; \; \; \; \; \; \; \; Q = 17.59\;MeV
\end{equation}
From equation (1), one can see that the amount of energy released is lower, but if you compare the mass involved, its $\frac{17.59}{5} = 3.5\;MeV/u$ which is more than 3.5 times more than that of fission \cite{lilley2013nuclear}. 

Compared to mining Uranium, it is a lot easier to acquire deuterium, as it makes 0.03\% of all the water in the ocean \cite{serway2004physics}.


\bibliographystyle{plain}
\bibliography{References.bib}
\end{multicols}
\end{document}

I have the problem that I'm using two columns, and cite something at the middle of the page on the left side, then on the top of the right side. The citations on top right gets numbered [1] and [2], and the first citation on the left side gets numbered [3]. This is probably because the citation order is decided by which citation is the top-most one, not necessary the first one you'd read. Its annoying because the first citation you read is then marked as [3].

I'm using Overleaf and BibTeX

Any way to fix this easily?

Sorry for the amount of code

This is what i looks like.

  • Welcome to TeX.SX! Unfortunately (or fortunately, depending on your view), there are several different ways to produce bibliographies and citations in LaTeX and all approaches have their quirks and idiosyncrasies. There are also several different ways to produce multi-column documents and again these methods may differ in important details for your question. It can be quite hard to give useful advice if we don't know roughly what your document looks like. I know it can be time consuming to come up with a useful example, but it will increase your chances of getting a good answer. – moewe Apr 13 '19 at 9:53
  • That all said, I just tested a very simple \documentclass[british,twocolumn]{article} with \bibliographystyle{unsrt} where I cited something in the left column in the lower half of the page and something in the right column in the upper half of the page and got [1] for the left and [2] for the right citation as expected. That is to say the citation number followed the flow of the text, not the distance to the top of the page. Hence, I can not reproduce what you are seeing. So I will definitely need to see an example document (tex.meta.stackexchange.com/q/228). – moewe Apr 13 '19 at 10:00
  • I added the code, and what it looks like. – Sebbek8 Apr 13 '19 at 10:07
  • The style plain sorts the entries in the bibliography by name, not by citation order. So the citation number you get are invariant under the position on the page. I must admit that I'm a bit confused by the order in the bibliography, but the entries look a bit weird, so I can only say why you get the order you get, when I have seen the relevant entries of References.bib. If you want citations to be numbered in the order of appearance/citation, use \bibliographystyle{unsrt} instead of plain. – moewe Apr 13 '19 at 10:12
  • 1
    Welcome to TeX.SX! Thank you for posting a working example! At the same time, much of your code does not seem to be relevant to the question you're asking here. Please limit the example to only the code required for your issue to appear. You can have a look at this guide for how to prune your code for this purpose. – L. F. Apr 13 '19 at 10:39