Congratulations to Serge Haumont (member of this blog) !
He found the solution to the dolphin's sleep problem (without looking into the knowledge fund).
Let us summarize the problematic situation.
If the dolphin sleeps, he will die by drowning (first he will lack oxygen and could eventually die from it).
If the dolphin does not sleep he will finally die from exhausting.
Of course, in the reality, the dolphin sleeps without any problem. The problem is stated only for the illustration of a physical contradiction and its resolution.
It has been already seen here that it is possible to solve a physical contradiction by separating in space or in time the two opposite requirements. Let us apply the two suggested types of separation :
* separation in time : during T1 the dolphin's brain is in its sleepy state, and during T2 the dolphin's brain is in its awaken state. Let's remark that the situation during T1 is exacly the problematic situation which is considered here, in the case where T1 is the sleep duration (or duration of a sleep cycle). Consequently, in this case, nothing is solved and we have walked along a circle. If T1 is of a much lower order of magnitude than a sleep cycle, for instance of the order of magnitude of a breathe, then the problem is theoretically solved : it is suggested that :
* the dolphin is awake during a complete breathe, then
* the dolphin gets asleep for a short duration, while he is in apnea, then
* the former cycle begins again and again
This is a strange way of sleeping ! A theoretical art of the micro-nap
(congratulations to David G. - member of this blog - and my father who suggested directly to me such a solution - this is not the spirit of the blog, however - )
* separation in space : one part of the brain does not sleep, and at the same time, the other part of the brain stays awake. This is exactly what the dolphin does, naturally of course. A structural property of the brain of mammals is used : the natural spatial separation of the brain into two hemispheres (of course some other parts of the brain exist ...). Practically the dolphin "solves" the initially stated problem and sleeps in the following way :
* first the dolphin :
* fulfills the function "regeneration" by sleeping with the left hemisphere
* fulfills the function "breathing" by staying awake (and then controlling this function) with the right hemisphere
* afterwards (after a sleep cycle, I assume) the former separation in space is inverted :
* the function "regeneration" is symmetrically fulfilled with the right hemisphere (not only the body must regenerate, the brain must also regenerate)
* the function "breathing" is ensured by the left hemisphere which stays awake
On the above image, one observes the left fin of the dolphin which is kept horizontal thanks to its activity which is maintained by the waking activity of its right hemisphere ; conversely the right fin is vertical for it is not active, in relationship with the sleepy left hemisphere. The red and blue colors correspond to the right and left parts of the dolphin, respectively (as indicated in Italian language on the Figure). The arrows' ends should be inverted for a correct description of the phenomenon. The curves 1 to 6 are electroencephalograms' excerpts, whereas the other graphs measure the activity of the fins.
(source of the image : http://www.scienzagiovane.unibo.it/English/sleep/3-sleep-animals.html)
As a conclusion, it can be noticed that :
* the dolphin's sleep problem is solved by both separations in space and in time
* an internal resource of the system is used for the problem solving : actually it is a structural property : the brain of mammals which is naturally separated (in space) into two hemispheres
Furthermore the concept of function has been introduced. It is of very high importance within TRIZ.