Being both wireless and mobile, low Earth obiting (LEO) satellite access networks have a unique set of link errors including bit corruption, handoff, and limited connectivity. Unfortunately, most transport protocols are only designed to handle congestion-related errors common in wired networks. This inability to handle multiple kinds of errors results in severe degradation in effective throughput and energy saving, which are relevant metrics for a wireless and mobile environment. A recent study proposed a new transport protocol for satellites called STP that addresses many of the unique problems of satellite networks. There was, however, no explicit attempt to implement a differentiating error control strategy in that protocol. This paper proposes grafting a new probing mechanism in STP to make it more responsive to the prevailing error conditions in the network. The mechanism works by investing some time and transmission effort to determine the cause of error. This overhead is, however, recouped by handsome gains in both the connection's effective throughput and its energy efficiency.
In this paper, based on the concept of building blocks with interactions, we study the stability of models of Si(lll) 7×7 reconstructed surface. With use of tight-binding method, we calculated formation energies of various building blocks and their interactions. With these building blocks, various large unit surfaces can be constructed and their total energies can be easy estimated, without heavy calculations. We evaluate the surface energies of Si(lll) 5×5 and 7×7 DAS models, and get the results of -0.467 eV and -0.477 eV, respectively, close to the results of Qian and Chadi. Moreover, we point out that neither the 7×7 adatom model nor the 7×7 adatom-vacancy model are stable.
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