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Stirling cryocoolers with a single stage of expansion routinely achieve cryogenic refrigeration temperatures of 70 K. Lower temperatures can be achieved with multiple expansion stages arranged ‘in series’, 20 K with two stages, and less than 10 K with three or four stages. Multiple expansion Stirling power systems are also in prospect particularly for exhaust heat recovery systems using different stages of progressively lower temperatures. Two or more stages can be combined in a single cylinder. Multiple expansion Stirling machines have been a topic of interest at The University of Calgary for some years. Recently a second-order computer simulation program with integral graphics package for Stirling cryocoolers with up to four stages of expansion were developed and made available to the Stirling community. Adaptation of the program to multiple expansion Stirling power systems is anticipated. This paper briefly introduces the program and presents a specimen result.

Head neck responses from volunteer experiments, as obtained in various loading directions by the Naval Biodynamics Laboratory, represent a unique set of data in the field of biomechanical research. From this a set of volunteer thoracic (T1) and head responses were selected as a reference for this study. Two loading conditions were considered i.e. frontal and lateral directions. The objective of this study is to develop a finite element model of the human neck in frontal and lateral directions. The number of elements in the model was kept low in order to reduce the processing time for simulation and to minimize damping problems. The structure of the model is as follows: the vertebrae and the head were considered as rigid bodies. The interface between vertebrae such as discs and different ligaments are modelled by brick and spring elements. The passive action of the muscles are taken into account when determining the stiffness characteristics of the ligaments.