A method of constructing an SDH‐based time transfer network and its experimental examination

In this paper we propose a simplified SDH (Synchronous Digital Hierarchy)‐based time synchronous system that does not require the modification of existing SDH transmission equipment (STE) and clock supply equipment (CSE). The system has auxiliary time synchronizing equipment (TSE) attached to existing STE and CSE and can be expanded in a cascade and branch manner, where frequency and time are separately synchronized, and which enables us to partially time‐synchronize an SDH network or to introduce a time transfer network locally. Experimental time synchronizing devices using a 576‐kbps data communication channel (DCC) in the section overhead (SOH) showed potentially satisfactory performance, with synchronization errors of a four‐link system on the order of submicroseconds. Noise analyses of experimental TSE, DCC, CSE, and optical links showed that accuracy on the order of microseconds can be achieved. © 2000 Scripta Technica, Electr Eng Jpn, 132(2): 39–48, 2000     

Microstructures and hydrogen absorption–desorption behavior of an A2B7-based La-Mg-Ni alloy

The microstructural changes during hydrogen absorption–desorption cycles of an A₂B₇-based La-Mg-Ni alloy with a nominal composition of La_1.5Mg_0.5Ni_7.0 were systematically investigated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). The ternary La-Mg-Ni alloy was mostly composed of 2H-A₂B₇ phase with minor inclusions of 3R-A₅B₁₉, 2H-A₅B₁₉ and 3R-AB₃ phases existing as parts of intergrowth structures with the major A₂B₇ phase. Most parts of the major 2H-A₂B₇ phase containing Mg exhibited an excellent crystal structure retention after the hydrogen absorption–desorption cycles at 80 °C. Two types of defected bands were found to develop after the first hydrogen absorption–desorption cycle. The first ones are amorphous bands developed inside the minor 3R-AB₃ phase, while the second ones develop as heterogeneously strained regions inside the major 2H-A₂B₇ phase. Both the defected bands are considered to be responsible for the irreversible hydrogen capacity of the A₂B₇-based La_1.5Mg_0.5Ni_7.0 alloy during the hydrogen absorption–desorption cycles at 80 °C.