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.
Active numerical model of human body for reconstruction of falls from height.
Falls from height constitute the largest group of incidents out of approximately 90,000 occupational accidents occurring each year in Poland. Reconstruction of the exact course of a fall from height is generally difficult due to lack of sufficient information from the accident scene. This usually results in several contradictory versions of an incident and impedes, for example, determination of the liability in a judicial process. In similar situations, in many areas of human activity, researchers apply numerical simulation. They use it to model physical phenomena to reconstruct their real course over time; e.g. numerical human body models are frequently used for investigation and reconstruction of road accidents. However, they are validated in terms of specific road traffic accidents and are considerably limited when applied to the reconstruction of other types of accidents. The objective of the study was to develop an active numerical human body model to be used for reconstruction of accidents associated with falling from height. Development of the model involved extension and adaptation of the existing Pedestrian human body model (available in the MADYMO package database) for the purposes of reconstruction of falls from height by taking into account the human reaction to the loss of balance. The model was developed by using the results of experimental tests of the initial phase of the fall from height. The active numerical human body model covering 28 sets of initial conditions related to various human reactions to the loss of balance was developed. The application of the model was illustrated by using it to reconstruct a real fall from height. From among the 28 sets of initial conditions, those whose application made it possible to reconstruct the most probable version of the incident was selected. The selection was based on comparison of the results of the reconstruction with information contained in the accident report. Results in the form of estimated injuries overlap with the real injuries sustained by the casualty.
A new method of near field analysis
The problem of the accurate determination of the total electromagnetic field produced by a current distribution on a circular disc type aperture is examined. For comparison of the near and Fresnel region solutions, an exact Maxwellian integral is used as the starting point. Aperture and space coordinates are separated by the use of Bessel function addition theorems, allowing the field to be expressed as a sum of terms containing radial and angular integrals. The radial integrals involve only the disc (aperture) distribution and coordinates while the angular integrals involve only the elevation angle. The distance from origin appears implicitly in the series coefficients. These integrals are suitable for high speed computations and have been evaluated for a number of cases. The results are compared with the small angle and general Fresnel formula values for various observation angles, distances from the aperture, and aperture distributions.