Fall from height in a stairwell--mechanics and simulation analysis.
The range of problems considered in the biomechanical analysis of a fall from height has been presented. A complicated case of a fall in a stairwell was investigated, the analysis of which demonstrates the research scale and aspect multitude. The scope of the article was restricted to the analysis of biomechanical problems and the simulation analysis of the event. A virtual 3D model of the stairwell was built using sketches, photographs and photogrammetric techniques. A dummy created according to the victim's data was parameterised. Using the PC-Crash biomechanical module a series of several hundred simulations were run following the adopted research plan, allowing for pre-formulated boundary conditions. The region of the stairwell where the accident was likely to originate and the victim's initial configuration were identified. It was proved that biomechanical simulation can bring invaluable benefits in exposing the mechanism of an event and verification of various hypotheses. Despite general similarities, each fall has its own specificity, which, making the use of methodological generalisations difficult, increases the significance of casuistry. The presented analysis can prove very useful in providing guidelines on investigating other cases.
Injuries sustained in falling fatalities in relation to different distances of falls.
BACKGROUND
Falling from a distance is an important issue worldwide, which happens in different ages, genders and circumstances. It is usually not considered a medicolegal case in many countries hence no autopsy is performed. This study focused on analyzing injuries sustained in victims of falling in relation to different distances of fall.


METHODS
Retrospective study of 352 autopsy reports of falling victims brought to the forensic pathology department at Jordan University Hospital during the period from January 1990 to March 2016.


RESULTS
Among 352 cases, 256 (72.7%) were males and 96 (27.3%) were females. 303 (86.1%) cases showed accidental fall, 31 (8.8%) were suicidal, 2 (0.6%) were homicidal and un-clarified death in 16 (4.5%). Time of death was directly proportionate with the distance of fall. Victims fell from distances less than 3 m were 123 (35%), most of them were children less than 7 years 50 (40.5%) and unemployed adults more than 45 years were 48 (39.1%). They showed multiple abrasions (62.6%), few contusions (64.2%) and absent laceration of the skin (84.5%). Victims fell from distances of 3-9 m were 123 (35%), most of them were male workers 56 (60.2%). They showed multiple abrasions (63.5%), few contusions (71%) and few lacerations of skin (50.5%). Victims fell from distances more than 9 m were 136 (38.6%), most of them were male workers 71 (52.2%) and female servants 23 (17%). They showed few abrasions (80.9%), multiple contusions (64.7%) and few lacerations of skin (48.5%). The number of fractured limbs increases obviously with distances more than 3 m. Skull vault fractures were found in all distances, while skull base fractures showed in distances of 3-9 m and more than 9 m. Head injury was the most common fatal injury in all distances. Chest injuries were prominent mainly in distances more than 3 m. While abdominal injuries were mainly prominent in distances more than 9 m.


CONCLUSIONS
This study showed the effect of different distances of fall in causing different types of injuries in falling fatalities. Internal injuries were in a direct proportion with distances of fall, while external injuries showed a great importance in interpretation of the way of fall.
LYAPUNOV-BASED TRANSFER BETWEEN ELLIPTIC KEPLERIAN ORBITS
We present a study of the transfer of satellites between elliptic Keplerian orbits using Lyapunov stability theory specific to this problem. The construction of Lyapunov functions is based on the fact that a non-degenerate Keplerian orbit is uniquely described by its angular momentum and Laplace (- Runge-Lenz) vectors. We suggest a Lyapunov function, which gives a feedback controller such that the target elliptic orbit becomes a locally asymptotically stable periodic orbit in the closed-loop dynamics. We show how to perform a global transfer between two arbitrary elliptic orbits based on the local transfer result. Finally, a second Lyapunov function is presented that works only for circular target orbits.