## 5 Results  
### Dynamic Analysis of Night-Time Light Changes at the National Scale  
The urban built-up area mask is extracted using the statistical method. When the threshold is equal to 10.02, the built-up area of Kiev is 393.89 square kilometers, which is close to the statistical area of 394 square kilometers. This threshold is set as the overall threshold in order to extract data for the whole country. The built-up area is shown in Figure 3.  
Figure 3: Ukrainian urban built-up areas. The built-up area data were binarized, where the city value was set to \(1\) and the non-city value was set to \(0\). The data were first multiplied with the corrected night-time light data to retain the night-time light intensity of the built-up area, then the unstable night-time light was removed and the city night-time light images were obtained. Following this, the administrative boundary division was then used to analyze the above image and obtain the total amount of night-time light in Ukraine. More than 60 percent of the country's night-time light was lost after the conflict broke out. We analyzed the dynamic change of night-time light by combining the military clashes and strategies between Russia and Ukraine. By screening the data published by online media, key information affecting the development of the conflict, such as urban control, humanitarian aid, and other key data, can be obtained, as shown in Table 1. Several cities are taken as examples to determine the ways in which different events of the conflict have affected night-time light. Figure 4 shows the time-dependent changes in the Ukrainian national night-time light ratio index. Different columns in the figure represent the five negotiations that took place within the research period of this paper, namely on 28 February, 3 March, 7 March, 15 March, and 29 March. Peace negotiations are closely related to military operations. During the talks, military operations often stagnate. The negotiation results often affect subsequent military operations, which in turn affect human activity. The intensity of night-time light should reflect these changes. \begin{table}
\begin{tabular}{c c c c c c c} \hline \multirow{3}{*}{**State**} & \multirow{2}{*}{**Type**} & \multicolumn{2}{c}{**Outbreak of**} & \multicolumn{1}{c}{**The First**} & \multicolumn{1}{c}{**The Second**} & \multicolumn{1}{c}{**Humanitarian**} & \multicolumn{1}{c}{**The Third**} \\  & & **Conflict** & **Negotiation** & **Negotiation** & **Corridor** & **Negotiation** \\ \cline{3-6}  & & **Date** & **2.24 —** & **0228** & **0303** & **3.5 —** & **3.7** \\ \cline{2-6}  & & **Impact** & **-** & **+** & **+** & **+** & **+** \\ \hline Cherkasy & UC & – & – & – & – & – \\ Chernivtsi & B & IN & IN & IN & IN & IN \\ Dnipropetrovs’k & B & IN & IN & IN & IN & IN \\ Donets’k & RC & IN & IN & – & IN & – \\ Kharkiv & B & IN & IN & IN & IN & IN \\ Kiev City & B & IN & IN & IN & IN & IN \\ Zaporizhzhya & RC & IN & IN & IN & IN & – \\ \hline \multirow{3}{*}{**State**} & \multirow{3}{*}{**Type**} & \multicolumn{1}{c}{**Multimational**} & \multicolumn{1}{c}{**The Fourth**} & \multicolumn{1}{c}{**Conflict**} & \multicolumn{1}{c}{**The Fifth**} & \multicolumn{1}{c}{**Russian**} \\  & & **Intervention** & **Negotiation** & **Escalation** & **Negotiation** & **Troops** \\ \cline{2-6}  & & **Date** & **3.14 —** & **3.15** & **3.20 —** & **3.29** \\ \cline{2-6}  & & **Impact** & **-** & **+** & **-** & **+** & **+** \\ \hline Cherkasy & UC & IN & – & – & – & – \\ Chernivtsi & B & IN & IN & IN & IN & – \\ Dnipropetrovs’k & B & – & IN & IN & IN & – \\ Donets’k & RC & – & – & – & – & – \\ Kharkiv & B & – & IN & IN & IN & – \\ Kiev City & B & IN & IN & IN & IN & IN \\ Zaporizhzhya & RC & – & – & – & – & – \\ \hline \end{tabular}
\end{table} 
Table 1: Ukrainian cities in military conflict situations. There are three types of cities analyzed here, namely cities in the RC (Russian-controlled area), cities in the UC (Ukrainian-controlled area), and cities in the B (belligerence/conflict area).