## 3 Results and Discussion
### Analysis of EEG and Cardiac Activity Status in the Cooling Condition
Activation of \(\theta\)-wave means that the subject is  
Figure 4: Averaged frequency spectrum over 16 channels with absolute frequency. (**a**) Frontal lobe zone (Fz). (**b**) Central lobe zone (Cz). (**c**) Temporal lobe zone (Tz). (**d**) Occipital lobe zone (Oz). taking adequate rest, and the activation of SMR and \(\beta\)-wave increases when the subject is performing concentrated tasks. Activated relative \(\theta\)-waves represented 23.9%, 32.7%, and 39.6% among brain waves when using basic, ventilation, and cold water-cooling seats, respectively. Therefore, it was confirmed that the relative \(\theta\)-wave is the most activated among various brain waves. In the case of using the ventilation and cold water-cooling seats, the relative \(\theta\)-wave increased by 36.8% and 65.5%, respectively, compared to that when using the basic seat. The proportion of the relative \(\alpha\)-wave among brain waves was 15.9%, 20.5%, and 17.9%, when the basic, ventilation, and cold water-cooling seats were used, respectively. Moreover, when the ventilation and cold water-cooling seats were used, the relative \(\alpha\)-wave increased by 28.9% and 12.5%, respectively, compared to that of the basic seat. When using the basic seat, the degree of EEG activation decreased in the following order: relative \(\theta\)-wave, relative \(\gamma\)-wave, relative high \(\beta\)-wave, relative \(\alpha\)-wave, relative SMR, and relative \(\beta\)-wave. In the case of using the ventilation and cold water-cooling seats, the following order was observed: relative \(\theta\)-wave, relative \(\alpha\)-wave, relative \(\gamma\)-wave, relative high \(\beta\)-wave, relative SMR, and relative \(\beta\)-wave. The relative SMR and relative \(\beta\)-wave are activated when maintaining concentration while learning or thinking, and showed the lowest activity during rest in this study. When the ventilation and the cold water-cooling seats were used, the activation of the relative \(\alpha\)-wave was different from that using the basic seat. This indirectly indicates that the subject felt more comfortable during the rest and the external concentration was reduced in this state, compared to the case when the basic seat was used. In other words, ventilation and cold water-cooling seats provided a more comfortable rest, compared to the basic seat, in summer indoor spaces. Overall, the relative \(\theta\)-wave, which is an indicator of sleeping and comfortable rest, was considerably activated, reaching a level of 39.6% when using the cold water-cooling seat. Therefore, the use of a cold water-cooling seat for resting was the most appropriate method to provide a suitable rest environment for the subjects. Table 4 shows the activation of the relative \(\theta\)-wave and relative \(\alpha\)-wave for each area in the subject's brain when resting using the basic, ventilation, and cold water-cooling seats at an indoor temperature of 27.5 \({}^{\circ}\)C during summer. The difference in the activity of relative \(\theta\)-wave and \(\alpha\)-wave at the left and right hemisphere of subject under various resting conditions is shown in Table 4. The relative \(\theta\)-wave is more activated when the ventilation and cold water-cooling seats are used. Moreover, the most active brain wave is obtained when using the cold water-cooling seat. Based on this result, it can be concluded  
Figure 5: Percentage of electroencephalograms (EEGs) with absolute frequency. that a suitable resting environment was provided to the subjects during the break using the cold water-cooling seat. When the subject used the basic seat, the activation of the right hemisphere \(\alpha\)-wave was prominent, compared to that of the left hemisphere, and the brain waves of the frontal lobes were more active than those in other areas. This indirectly indicates that the basic seat is not suitable for the subject's rest during summer.