In situ13C NMR study of tert-butanol interaction with moderately concentrated sulfuric acid

An in situ NMR study of tert-butanol dehydration in 95 and 85% sulfuric acid did not indicate the formation of tert-butyl cations as active reaction intermediates. Instead, only NMR lines from oxonium ions under the condition of fast exchange with water and the acid were observed. It is most likely that, in the concentrated acid, the active intermediates of this reaction are represented by tert-butyl sulfuric ester which probably is a precursor of invisible tert-butyl carbenium ions representing short-lived excited or transition states.     

Simulation of Facial Muscle Actions Based on Rational Free Form Deformations

This paper describes interactive facilities for simulating abstract muscle actions using Rational Free Form Deformations (RFFD). The particular muscle action is simulated as the displacement of the control points of the control-unit for an RFFD defined on a region of interest. One or several simulated muscle actions constitute a Minimum Perceptible Action (MPA), which is defined as the atomic action unit, similar to Action Unit (AU) of the Facial Action Coding System (FACS), to build an expression.     

Amore Address Mapping with Overlapped Rotating Entries

A memory management unit that supports demand paging is implemented with standard logic and fast-access RAM chips, resulting in much faster address translation that that provided by the standard Motorola MC68451 MMU.     

IR spectroscopic study of Pt/Kl zeolites using adsorption of CO as a molecular probe

FTIR spectra of CO adsorbed on Pt/KL catalysts show that the relative band intensities and the total dispersion markedly depend on the catalyst preparation method (ion exchange, incipient wetness impregnation or co-impregnation with KCl). The CO stretching frequency of the dominant band for linear CO is shifted to higher wavenumbers, parallel with the proton concentration in the reduced catalyst, which is derived independently from the intensity of the IR bands of the OH groups. The results are in accordance with the model that electron-deficient platinum particles are platinum-proton adducts.On leave from: N.D. Zelinsky Institute of Organic Chemistry, Academy of Sciences, Moscow, USSR.     

A multiple-switch high-voltage DC-DC converter

Series connection of power devices has evolved into a mature technique and is widely applied in HV DC power systems. Static and dynamic voltage balance is ensured by shunting individual devices with dissipative snubbers. The snubber losses become pronounced for increased operating frequencies and adversely affect power density. Capacitive snubbers do not exhibit these disadvantages, but they require a zero-voltage switching mode. Super-resonant power converters facilitate the principle of zero-voltage switching. A high-voltage DC-DC power converter with multiple series-connected devices is proposed. It allows the application of nondissipating snubbers to assist the voltage sharing between the multiple series-connected devices and lowers turnoff losses. Simulation results obtained with a circuit simulator are validated in an experimental power converter operating with two series-connected devices. The behavior of the series connection is examined for MOSFETs and IGBTs by both experimental work with a 2 kW prototype and computer simulation. Applications can be found in traction and heavy industry, where the soft-switching power converter is directly powered from a high-voltage source