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Majewski, Marcin A.,Chmielewski, Piotr J.,Chien, Alan,Hong, Yongseok,Lis, Tadeusz,Witwicki, Maciej,Kim, Dongho,Zimmerman, Paul M.,Stę,pień,, Marcin Royal Society of Chemistry 2019 Chemical science Vol.10 No.11
<▼1><P>A diindenophenanthrene biradicaloid, formally derived from Chichibabin's hydrocarbon, is obtained in a short, scalable synthesis.</P></▼1><▼2><P>A diindenophenanthrene biradicaloid, formally derived from Chichibabin's hydrocarbon, is obtained in a short, scalable synthesis. The present system is electron-rich and devoid of conjugated substituents, and still exhibits very good stability under ambient conditions. The introduction of the diindeno[1,2-<I>a</I>:2′,1′-<I>i</I>] phenanthrene ring framework results in a singlet biradicaloid system with an easily accessible triplet state (Δ<I>E</I><SUB>S–T</SUB> = –1.30 kcal mol<SUP>–1</SUP>) and a small electronic bandgap (1.39 V). The stability limits of the title hydrocarbon were explored systematically in the solid state, to reveal an unusual thermally initiated hydrogen-scrambling oligomerization process.</P></▼2>
Improvement of dynamic response in an impact absorber by frictional elements
Jorge Bedolla,Dariusz Szwedowicz,Juan Jiménez,Tadeusz Majewski,Claudia Cortés,Enrique S. Gutierrez-Wing 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.4
A novel device that uses friction between one or more pairs of elastic conical rings to dissipate the energy from an impacting body ispresented. The device consists of one moving and one stationary cylinders coupled to each other using two pairs of conical rings and aspring. The spring is used to restore the system to its original configuration after the impact. The dynamic response of the system to theimpact forces during impact events is analysed numerically and experimentally. The effects of several governing parameters, such as themass ratio between the cylinders, the duration of the transient response of the device, the magnitude of the rest zone of the moving elementand the peak impact force are investigated. The proposed system is applicable in sequential impact scenarios, in which remarkableimprovements were observed over traditional solid-rod impact absorbers. The present study may serve as a guide for the design of improveddamping devices for impact applications.