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Electrical Breakdown Strength of Insulation under Combined DC-AC Voltages
Grzybowski, S. The Korean Institute of Electrical and Electronic 1998 전기전자재료 Vol.11 No.10
Electrical breakdown strength of paper-oil and polypropylene/film-oil insulation samples was measured under dc, ac and pulsating voltages. The latter was obtained by superimposing ac upon dc volate and provides an attractive method for a simultaneous testing and assessment of the state of insulation of the various parts of HV apparatus in service. The measurements were carried out over a wide range of the pulsation ratio defined as p=Eac/Edc. The results obtained under pulsating voltages follow colsely an experssion which relates the breakdown strength to the sum of arc tangent and arc cotangent function of the parameter p. The study was carried out using dry paper as well as paper containing various degrees of moisture. The presence of moisture showed a pronounced effect upon the breakdown strength which varied with the pulsation parameter p.
Multistress Life Models of Epoxy Encapsulated Magnet wire under High Frequency Pulsating Voltage
Grzybowski, S.,Feilat, E.A.,Knight, P. The Korean Institute of Electrical Engineers 2003 KIEE International Transactions on Electrophysics Vol.3C No.1
This paper presents an attempt to develop probabilistic multistress life models to evaluate the lifetime characteristics of epoxy-encapsulated magnet wire with heavy build polyurethane enamel. A set of accelerated life tests were conducted over a wide range of pulsating voltages, temperatures, and frequencies. Samples of fine gauge twisted pairs of the encapsulated magnet wire were tested us-ing a pulse endurance dielectric test system. An electrical-thermal lifetime function was combined with the Weibull distribution of lifetimes. The parameters of the combined Weibull-electrical-thermal model were estimated using maximum likelihood estimation. Likewise, a generalized electrical-thermal-frequency life model was also developed. The parameters of this new model were estimated using multiple linear regression technique. It was found in this paper that lifetime estimates of the two proposed probabilistic multistress life models are good enough. This suggests the suitability of using the general electrical-thermal-frequency model to estimate the lifetime of the encapsulated magnet wire over a wide range of voltages, temperatures and pulsating frequencies.
The nanotechnology of life-inspired systems
Grzybowski, Bartosz A.,Huck, Wilhelm T. S. Nature Publishing Group, a division of Macmillan P 2016 Nature nanotechnology Vol.11 No.7
<p>For some decades now, nanotechnology has been touted as the 'next big thing' with potential impact comparable to the steam, electricity or Internet revolutions — but has it lived up to these expectations? While advances in top-down nanolithography, now reaching 10-nm resolution, have resulted in devices that are rapidly approaching mass production, attempts to produce nanoscale devices using bottom-up approaches have met with only limited success. We have been inundated with nanoparticles of almost any shape, material and composition, but their societal impact has been far from revolutionary, with growing concerns over their toxicity. Despite nebulous hopes that making hierarchical nanomaterials will lead to new, emergent properties, no breakthrough applications seem imminent. In this Perspective, we argue that the time is ripe to look beyond individual nano-objects and their static assemblies, and instead focus on systems comprising different types of 'nanoparts' interacting and/or communicating with one another to perform desired functions. Such systems are interesting for a variety of reasons: they can act autonomously without external electrical or optical connections, can be dynamic and reconfigurable, and can act as 'nanomachines' by directing the flow of mass, energy or information . In thinking how this systems nanoscience approach could be implemented to design useful — as opposed to toy-model — nanosystems, our choice of applications and our nanoengineering should be inspired by living matter.</p>
A Priori Estimation of Organic Reaction Yields
Emami, Fateme S.,Vahid, Amir,Wylie, Elizabeth K.,Szymkuć,, Sara,Dittwald, Piotr,Molga, Karol,Grzybowski, Bartosz A. WILEY‐VCH Verlag 2015 Angewandte Chemie Vol.127 No.37
<P><B>Abstract</B></P><P>A thermodynamically guided calculation of free energies of substrate and product molecules allows for the estimation of the yields of organic reactions. The non‐ideality of the system and the solvent effects are taken into account through the activity coefficients calculated at the molecular level by perturbed‐chain statistical associating fluid theory (PC‐SAFT). The model is iteratively trained using a diverse set of reactions with yields that have been reported previously. This trained model can then estimate a priori the yields of reactions not included in the training set with an accuracy of ca. ±15 %. This ability has the potential to translate into significant economic savings through the selection and then execution of only those reactions that can proceed in good yields.</P>
Jeong, Yong-Kwang,Lee, Young Min,Yun, Jeonghun,Mazur, Tomasz,Kim, Minju,Kim, Young Jae,Dygas, Miroslaw,Choi, Sun Hee,Kim, Kwang S.,Kwon, Oh-Hoon,Yoon, Seok Min,Grzybowski, Bartosz A. American Chemical Society 2017 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.139 No.42
<P>Materials exhibiting excitation-wavelength-dependent photoluminescence, PL, are useful in a range of biomedical and optoelectronic applications. This paper describes a nanoparticulate material whose PL is tunable across the entire visible range and is achieved without adjusting particle size, any postsynthetic doping, or surface modification. A straightforward thermal decomposition of rhenium (VII) oxide precursor yields nanoparticles that comprise Re atoms at different oxidation states. Studies of time-resolved emission spectra and DFT calculations both indicate that tunable PL of such mixed-valence particles originates from the presence of multiple emissive states that become “active” at different excitation wavelengths. In addition, the nanoparticles exhibit photocatalytic activity that, under visible-light irradiation, is superior to that of TiO<SUB>2</SUB> nanomaterials.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2017/jacsat.2017.139.issue-42/jacs.7b07494/production/images/medium/ja-2017-07494q_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja7b07494'>ACS Electronic Supporting Info</A></P>