You are presented with multiple paper abstracts, alongside the associated literature review and chapter titles. Given the provided information, you are going to do a literature review. Please generate a coherent literature review that synthesizes the content, draws connections between different works, highlights major findings, and identifies any gaps in the existing research.

Literature Review Title: Ballistocardiography and Seismocardiography: A Review of Recent Advances 
Chapter Title:  B. SCG Signal Description 
1. Abstract of Cited Paper (BIB001):  Ballistocardiography was recorded in 3-D on a free floating astronaut in space as well as on healthy volunteers participating to the ESA 55th and DLR 19th parabolic flights campaigns. In this paper we demonstrate further the usefulness of recording and analyzing ballistocardiograms (BCG) in three dimensions. The spatial curves of the displacement, velocity and acceleration vectors are analyzed instead of their individual 2-D components. The maximum magnitude of the force vector is shown to be poorly correlated to the HI and IJ wave amplitude traditionally computed on the longitudinal (feet-to-head) component of acceleration (uni-dimensional BCG). We also suggest that kinetic energy and work are useful parameters to consider for a physiological interpretation of the 3D-BCG. The technique presented is invariant from the axis of representation and provides important novel physiological information. We stress further the need of 3D recordings and analysis techniques for Ballisto- and Seismo-cardiography.

Literature Review:
SCG is the measure of the thoracic vibrations produced by the heart's contraction and the ejection of blood from the ventricles into the vascular tree. Today, the SCG can readily be detected by placing a low-noise accelerometer on the chest. If a tri-axial accelerometer is used, SCG components are present in all three axes, each displaying a specific pattern BIB002 , BIB001 . However, in the literature, the majority of studies on SCG only focus on the amplitude of the dorso-ventral component, although it is likely that additional biological information could be derived also from the analysis of the longitudinal and lateral SCG components, and from the analysis of the acceleration vector trajectory during the heart cycle. Unless the contrary is stated to be consistent with the prevalent literature only the dorso-ventral acceleration component of SCG will be considered in the remainder of this paper.