## 3 Results and Discussion
### Analysis of EEG and Cardiac Activity Status in the Cooling Condition  
Figure 4 shows the average frequency of the subjects' frontal lobe zone (Fz), central lobe zone (Cz), temporal lobe zone (Tz), and occipital lobe zone (Oz) during rest using the basic, ventilation, and cold water-cooling seats at 27.5 \({}^{\circ}\)C. The \(\delta\)-wave (1-3 Hz) and \(\theta\)-wave (4-7 Hz) components corresponding to 0-7 Hz were relatively activated in the frontal and occipital lobes. Moreover, it was confirmed that the average frequency was most activated when the cold water-cooling seat was used. An increase in the \(\delta\)-wave activity in the frontal lobe zone, related to the mood control, and the posterior cortex, associated with signal processing was observed. The increase in the \(\delta\)-wave activity indicated that the subject felt comfortable during rest using various seats, similar to the brain activity when the human is in a deep sleep. As \(\delta\)-wave and \(\theta\)-wave frequencies occur during sleep and drowsiness, it can be inferred that the use of the cold water-cooling seat provided an appropriate sleep and drowsiness environment to the subject during rest. The lowest values in the \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Vote** & \begin{tabular}{c} **Thermal Sensation Vote** \\ **(TSV)** \\ \end{tabular} & \
\begin{tabular}{c} **Comfort Sensation Vote** \\ **(CSV)** \\ \end{tabular} &
\begin{tabular}{c} **Concentration Level Vote** \\ **(CLV)** \\ \end{tabular} \\ \hline +3 & Hot & Very comfortable & Very good \\ +2 & Warm & Comfortable & Good \\ +1 & Slightly Warm & Slightly comfortable & Slightly good \\ 0 & Neutral & Neutral & Neutral \\ \(-1\) & Slightly Cool & Slightly uncomfortable & Slightly bad \\ \(-2\) & Cool & Uncomfortable & Bad \\ \(-3\) & Cold & Very uncomfortable & Very bad \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Thermal sensation vote (TSV), comfort sensation vote (CSV), and concentration level vote (CLV) questionnaire scales. Figure 3: Experimental process and timetable. average frequencies of the brain were found in the sensorimotor rhythm (SMR) (12-15 Hz) and mid \(\beta\)-wave components (16-18 Hz) corresponding to 10-20 Hz in all areas. When the subject was resting, low values of SMR and mid \(\beta\)-wave average frequencies were obtained because these frequencies occur when the brain maintains concentration in an active state with positive thinking. After an intermediate frequency of 20 Hz, the average frequency of the brain gradually increased at high \(\beta\)-wave frequencies (20-30 Hz) and then slightly decreased at the \(\gamma\)-wave frequencies (31-50 Hz). In this study, the subject conducted a simple concentration test, such as performing office work before and after a break. Subsequently, because the subject sat in a chair and rested for a certain period, the stress caused by the subject's office work affected the variation of brain activity. In all areas, the \(\gamma\)-wave activity of the ventilation and cold water-cooling seats decreased by 33.3% and 42.8%, respectively, compared to that of the basic seat. As a result of the experiment, the \(\delta\)-wave frequencies, which are activated when taking proper rest, were most active when the cold water-cooling seat was used. The \(\theta\)-wave frequencies, which commonly occur during sleep and drowsiness, were most active when the ventilation seat was used. However, the difference in the \(\theta\)-wave frequencies between the cold water-cooling and ventilation seat in the temporal and occipital lobes areas was approximately 8%, which is significant. Therefore, the use of a cold water-cooling seat can provide a pleasant resting environment for the subjects. Figure 5 presents a graph of the relative activity ratio of brain waves in the entire brain area when resting, using the basic, ventilation, and cold water-cooling seats at an indoor temperature of 27.5 \({}^{\circ}\)C during summer.