Data driven modeling for power transformer lifespan evaluation

Large sized power transformers are important parts of the power supply chain. These very critical networks of engineering assets are an essential base of a nation＇s energy resource infrastructure. This research identifies the key factors influencing transformer normal operating conditions and predicts the asset management lifespan. Engineering asset research has developed few lifespan forecasting methods combining real-time monitoring solutions for transformer maintenance and replacement. Utilizing the rich data source from a remote terminal unit （RTU） system for sensor-data driven analysis, this research develops an innovative real-time lifespan forecasting approach applying logistic regression based on the Weibull distribution. The methodology and the implementation prototype are verified using a data series from 161 kV transformers to evaluate the efficiency and accuracy for energy sector applications. The asset stakeholders and suppliers significantly benefit from the real-time power transformer lifespan evaluation for maintenance and replacement decision support.     

Effects of size reduction on deformation,microstructure, and surface roughness of micro components for micro metal injection molding

The fabrication of 17-4PH micro spool mandrils by micro metal injection molding was described here. The effects of size reduction on deformation, microstructure and surface roughness were studied by comparing a φ500 μm micro post and a φ1.7 mm cylinder after debinding and sintering. Experimental results show that slumping of the micro posts occurred due to a dramatic increase in outlet vapor pressure initiated at the thermal degradation onset temperature and the moment of gravity. Asymmetrical stress distribution within the micro component formed during the cooling stage may cause warping. Prior solvent debinding and adjustment in a thermal debinding scheme were useful for preventing the deformation of the micro components. Smaller grain size and higher micro hardness due to impeded grain growth were observed for the micro posts compared with the φ1.7 mm cylinder. Surface roughness increased with distance from the gate of the micro spool mandril due to melt front advancement during mold filling and the ensuing pressure distribution. At each position, surface roughness was dictated by injection molding and increased slightly after sintering.     

High-efficiency trace Na extraction from crystal quartz ore used for fused silica-A pretreatment technology

Trace Na sources, extraction dynamics of trace Na, and influences of calcination temperature on quartz lattice, fluid inclusions, and muscovite were studied in detail herein for trace Na extraction from the quartz ore with water leaching at 90℃. Experimental results suggested that the trace Na sources included quartz lattice, fluid inclusions, and muscovite. The extraction rate of the trace Na in quartz ores can reach 31.0wt% after calcination at 900℃ for 5 h and water leaching at 90℃ for 24 h. The extraction process consisting of the dissolution of unfree Na and diffusion of free Na was dominated by calcination temperature. Calcination at 900℃ for 5 h was effective for extraction of the trace Na in fluid inclusions and muscovite. The extraction of the trace Na was mainly affected by the decrepitation of fluid inclusions when the calcination temperature ranged from 400 to 600℃ and by the damage of muscovite when the calcination temperature ranged from 600 to 900℃. Based on the extraction rates at different calcination temperatures, approximately 20.1wt% of the trace Na occurred in fluid inclusions, approximately 10.9wt% existed in muscovite, and 69.0wt% mainly occurred in quartz lattice.     

Effect of Cu on dehydrogenation and thermal stability of amorphous Mg-Ce-Ni-Cu alloys

The alloying element component is very crucial in improving the hydrogen storage performance of amorphous alloys.In this work,quaternary amorphous Mg_(70-x)Ce_(10)Ni_(20)Cu_x(x=3,7.5,10)alloys were prepared by meltspinning and the effect of Cu on hydrogenation and dehydrogenation were investigated in comparison with the Mg_(70-x)Ce_(10)Ni_(20)amorphous alloys.The initial hydrogenation kinetics of amorphous Mg_(70-x)Ce_(10)Ni_(20)Cu_x(x=0,3,7.5,10)was improved with the increase of Cu content according to the kinetics measured at a temperature below crystallization temperature.As hydrogen is absorbed,an amorphous-amorphous transition occurred,and relatively high Cu content would lead to phase separation in the hydrogenation process.Amorphous phase have much higher crystallization temperature after it absorbs hydrogen and the addition of Cu could increase the crystallization activation energy of amorphous hydrides.In addition,the increase of Cu content could reduce the dehydrogenation temperature of amorphous hydrides,which gives a significant indication for future improving research of the hydrogen desorption performance of Mg based amorphous hydrides.     

Research progress and prospects on machinery monitoring under varying working condition

A general review is given about the research progress of the rotating machinery condition monitoring under varying working condition. The major typical methods for analyzing are reviewed,including their progress,deficiencies and capabilities. Some prospects are given finally.     

Cidea-deficient mice have lean phenotype and are resistant to obesity

The thermogenic activity of brown adipose tissue (BAT), important for adaptive thermogenesis and energy expenditure, is mediated by the mitochondrial uncoupling protein1 (Ucp1) that uncouples ATP generation and dissipates the energy as heat. We show here that Cidea, a protein of unknown function sharing sequence similarity with the N-terminal region of DNA fragmentation factors Dffb and Dffa, is expressed at high levels in BAT. Cidea-null mice had higher metabolic rate, lipolysis in BAT and core body temperature when subjected to cold treatment. Notably, Cidea-null mice are lean and resistant to diet-induced obesity and diabetes. Furthermore, we provide evidence that the role of Cidea in regulating thermogenesis, lipolysis and obesity may be mediated in part through its direct suppression of Ucp1 activity. Our data thus indicate a role for Cidea in regulating energy balance and adiposity.     

Interaction of hydrogen with metal nitrides and imides

The pursuit of a clean and healthy environment has stimulated much effort in the development of technologies for the utilization of hydrogen-based energy. A critical issue is the need for practical systems for hydrogen storage, a problem that remains unresolved after several decades of exploration. In this context, the possibility of storing hydrogen in advanced carbon materials has generated considerable interest. But confirmation and a mechanistic understanding of the hydrogen-storage capabilities of these materials still require much work. Our previously published work on hydrogen uptake by alkali-doped carbon nanotubes cannot be reproduced by others. It was realized by us and also demonstrated by Pinkerton et al. that most of the weight gain was due to moisture, which the alkali oxide picked up from the atmosphere. Here we describe a different material system, lithium nitride, which shows potential as a hydrogen storage medium. Lithium nitride is usually employed as an electrode, or as a starting material for the synthesis of binary or ternary nitrides. Using a variety of techniques, we demonstrate that this compound can also reversibly take up large amounts of hydrogen. Although the temperature required to release the hydrogen at usable pressures is too high for practical application of the present material, we suggest that more investigations are needed, as the metal-N-H system could prove to be a promising route to reversible hydrogen storage.     

Delayed triggering of the 1999 Hector Mine earthquake by viscoelastic stress transfer

Stress changes in the crust due to an earthquake can hasten the failure of neighbouring faults and induce earthquake sequences in some cases. The 1999 Hector Mine earthquake in southern California (magnitude 7.1) occurred only 20 km from, and 7 years after, the 1992 Landers earthquake (magnitude 7.3). This suggests that the Hector Mine earthquake was triggered in some fashion by the earlier event. But uncertainties in the slip distribution and rock friction properties associated with the Landers earthquake have led to widely varying estimates of both the magnitude and sign of the resulting stress change that would be induced at the location of the Hector Mine hypocentre-with estimates varying from -1.4 bar (ref. 6) to +0.5 bar (ref. 7). More importantly, coseismic stress changes alone cannot satisfactorily explain the delay of 7 years between the two events. Here we present the results of a three-dimensional viscoelastic model that simulates stress transfer from the ductile lower crust and upper mantle to the brittle upper crust in the 7 years following the Landers earthquake. Using viscoelastic parameters that can reproduce the observed horizontal surface deformation following the Landers earthquake, our calculations suggest that lower-crustal or upper-mantle flow can lead to postseismic stress increases of up to 1-2 bar at the location of the Hector Mine hypocentre during this time period, contributing to the eventual occurrence of the 1999 Hector Mine earthquake. These results attest to the importance of considering viscoelastic processes in the assessment of seismic hazard.     

Investigation on Suspended Stripline and End-Coupled Bandpass Filter

In this paper, the variational method combined with Green's function is used to analyze the characteristics of suspended, stripline. The result is in good agreement with references. The design of mm-wave end-coupled bandpass filter with suspended substrate is discussed. The computer programs for design of suspended stripline and bandpass filter are established.     

The 17 KeV Neutrino Revived

We summarize the experiments on the 17 Kev/c~2 neutrino since 1985 and discuss possible mass term of the neutrino. Various extensions of the minimal standard model to accommodate a finite neutrino mass and the status of the massive neutrino phenomenology are summarized. Finally the meaning of the 17 KeV/c~2 neutrino is discussed. The purpose of this article is to collect the known relevant materials and to make a pedagogical summary of the interesting possibility of a heavy neutrino which will have far-reaching implications if it is eventually confirmed.