Low-Cost Online Partial Discharge Monitoring System for Power Transformers.

The article presents in detail the construction of a low-cost, portable online PD monitoring system based on the acoustic emission (AE) technique. A highly sensitive piezoelectric transducer was used as the PD detector, whose frequency response characteristics were optimized to the frequency of AE waves generated by discharges in oil-paper insulation. The popular and inexpensive Teensy 3.

Development of Acoustic Emission Sensor Optimized for Partial Discharge Monitoring in Power Transformers.

The acoustic emission (AE) technique is one of the unconventional methods of partial discharges (PD) detection. It plays a particularly important role in oil-filled power transformers diagnostics because it enables the detection and online monitoring of PDs as well as localization of their sources. The performance of this technique highly depends on measurement system configuration but mostly on the type of applied AE sensor.

Use of bearings with integrated ceramic insert in cementless total hip arthroplasty – a preliminary report.

Background: Ceramic-on-ceramic articulation presents advancement in the development modern of hip prostheses. It is particularly important for young patients, in whom complications related with polyethylene damages and metalosis pose a serious clinical problem due to the long period of implant functioning. The aim of this study was to assess the effect of total cementless hip replacement using an implant with a ceramic insert embedded in a metal cup and large prosthetic head constituting a ceramic-on-ceramic system in patients with hip osteoarthritis.

Multinuclear NMR study of the solution structure and reactivity of tris(trimethylsilyl)methyllithium and its iodine ate complex.

The extreme steric bulk of tris(trimethylsilyl)methyl derivatives (1-X) provides interesting structural and dynamic behavior for study. Dynamic NMR studies on 1-SePh and 1-I showed restricted rotation around the C-Si bonds of each trimethylsilyl groups. An extensive multinuclear NMR study of natural abundance and (6)Li and (13)C enriched 1-Li revealed three species in THF-containing solvents, a dimer 1T, and two monomers, the contact ion pair 1C, and solvent separated ion pair 1S.

Reactivity of the triple ion and separated ion pair of tris(trimethylsilyl)methyllithium with aldehydes: a RINMR study.

Low-temperature rapid-injection NMR (RINMR) experiments were performed on tris(trimethylsilyl)methyllithium. In THF/Me2O solutions, the separated ion (1S) reacted faster than can be measured at -130 degrees C with MeI and substituted benzaldehydes (k >/= 2 s -1), whereas the contact ion (1C) dissociated to 1S before reacting. Unexpectedly, the triple ion reacted faster with electron-rich benzaldehydes relative to electron-deficient ones.