9,553 research outputs found
History of the tether concept and tether missions: a review
This paper introduces history of space tethers, including tether concepts and tether missions, and attempts to provide a source of references for historical understanding of space tethers. Several concepts of space tethers since the original concept has been conceived are listed in the literature, as well as a summary of interesting applications, and a research of space tethers is given. With the aim of implementing scientific experiments in aerospace, several space tether missions which have been delivered for aerospace application are introduced in the literature.</jats:p
AIRBORNE PATH FREQUENCY BASED SUBSTRUCTURING METHOD AND ITS APPLICATIONS
Frequency based substructuring (FBS) is routinely used to model structural dynamics. It provides a framework for connecting structural subsystems together, assessing path contributions, determining the effect of mount modification, and identifying inverse forces. In this work, FBS methods are extended to include acoustic subsystems and connecting pipes and ducts. Connecting pipes or ducts are modeled using the transfer matrix approach which is commonly used for modeling mufflers and silencers below the plane wave cutoff frequency. The suggested approach is validated using boundary element method (BEM) simulation. Applications of the procedure include determining airborne path contributions, the effect of treating ducts and apertures, and the effect of making lumped acoustic impedance modifications to a subsystem. The method can be simplified and used for determining the effect of design changes on the insertion loss of enclosures
Gaussian dynamics equation in normal product form
In this paper, we discuss the normal product form of the density operator of
multimode Gaussian states, and obtain the correlation equation between the
kernel matrix R of the Gaussian density operator in the normal product form and
its kernel matrix G in the standard quadratic form. Further, we explore the
time evolution mechanism of R and obtain the Gaussian dynamical equation under
the normal product R=i(RJH-HJR). Our work is devoted to searching for another
mechanism for Gaussian dynamics. By exploring the description of the normal
ordered density matrix under the coherent state representation, we find that
our mechanism is feasible and easy to operate
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