Polarization Caging in Diffusion-Controlled Electron Transfer Reactions in Solution

In some bimolecular diffusion-controlled electron transfer (ET) reactions such as ion recombination (IR), both solvent polarization relaxation and the mutual diffusion of the reacting ion pair may determine the rate and even the yield of the reaction. However, a full treatment with these two reaction coordinates is a challenging task and has been left mostly unsolved. In this work, we address this problem by developing a dynamic theory by combining the ideas from ET reaction literature and barrierless chemical reactions. Two-dimensional coupled Smoluchowski equations are employed to compute the time evolution of joint probability distribution for the reactant (P-(1)(X,R,t)) and the product (p((2))(X,R,t)), where X, as is usual in ET reactions, describes the solvent polarization coordinate and R is the distance between the reacting ion pair. The reaction is described by a reaction line (sink) which is a function of X and R obtained by imposing a condition of equal energy on the initial and final states of a reacting ion pair. The resulting two-dimensional coupled equations of motion have been solved numerically using an alternate direction implicit (ADI) scheme (Peaceman and Rachford, J. Soc. Ind. Appl. Math. 1955, 3, 28). The results reveal interesting interplay between polarization relaxation and translational dynamics. The following new results have been obtained. (i) For solvents with slow longitudinal polarization relaxation, the escape probability decreases drastically as the polarization relaxation time increases. We attribute this to caging by polarization of the surrounding solvent, As expected, for the solvents having fast polarization relaxation, the escape probability is independent of the polarization relaxation time. (ii) In the slow relaxation limit, there is a significant dependence of escape probability and average rate on the initial solvent polarization, again displaying the effects of polarization caging. Escape probability increases, and the average rate decreases on increasing the initial polarization. Again, in the fast polarization relaxation limit, there is no effect of initial polarization on the escape probability and the average rate of IR. (iii) For normal and barrierless regions the dependence of escape probability and the rate of IR on initial polarization is stronger than in the inverted region. (iv) Because of the involvement of dynamics along R coordinate, the asymmetrical parabolic (that is, non-Marcus) energy gap dependence of the rate is observed.

A Five-Level Inverter Scheme for a Four-Pole Induction Motor Drive by Feeding the Identical Voltage-Profile Windings From Both Sides

This paper presents a five-level inverter scheme with four two-level inverters for a four-pole induction motor (IM) drive. In a conventional three-phase four-pole IM, there exists two identical voltage-profile winding coil groups per phase around the armature, which are connected in series and spatially apart by two pole pitches. In this paper, these two identical voltage-profile pole-pair winding coils in each phase of the IM are disconnected and fed from four two-level inverters from four sides of the windings with one-fourth dc-link voltage as compared to a conventional five-level neutral-point-clamped inverter. The scheme presented in this paper does not require any special design modification for the induction machine. For this paper, a four-pole IM drive is used, and the scheme can be easily extended to IMs with more than four poles. The proposed scheme is experimentally verified on a four-pole 5-hp IM drive.

Reactions of tetrahalogeno-o-benzoquinones—Part VII. Reaction of alkyl-2-naphthols with tetrachloro-o-benzoquinone

Reaction of 8-methyl-2-naphthol (4a) with the quinone3 gave a mixture of 8-methyl-2,2-(tetrachlorohenylenedioxy)naphthalen-1(2H)-one (1b) and 8-methyl-1,1-(tetrachloro-o-phenylenedioxy)naphthalen-2(1H)-one (2b) in almost equal amounts. Similarly, reaction of the naphthols (4b), (4d) and (4e) with3 gave the corresponding dienones (1c &2c), (1e &2e) and (1f &2f) in almost equal amounts. Reaction of 8-t-butyl-2-naphthol (4c) with3 gave exclusively 8-t-butyl-2,2-(tetrachloro--henylenedioxy)-naphthalen-1(2H)-one (1d). Oxidation of 3-t-butyl-2-naphthol (4f) with3 gave a mixture of 3-t-butyl-2,2-(tetrachloro-o-phenylendioxy) nephthalene-1(2H)-one(1g) and 3-t-butyl-1,1-(tetrachloro--phenylenedioxy)naphthelen-2 (1H)-one (2g) in the ratio 1∶6. Thus, onlyt-butyl group exherts pronounced steric influence on the rearrangement observed in the reaction of β-naphthol with the quinone3. Structures of all the compounds have been established by spectral data.

Performance Optimization of Induction Motor-Pump System Using Photovoltaic Energy Source

The optimization of a photovoltaic pumping system based on an induction motor driven pump that is powered by a solar array is presented in this paper. The motor-pump subsystem is analyzed from the point of view of optimizing the power requirement of the induction motor, which has led to an optimum u-f relationship useful in controlling the motor. The complete pumping system is implemented using a dc-dc converter, a three-phase inverter, and an induction motor-pump set. The dc-dc converter is used as a power conditioner and its duty cycle is controlled so as to match the load to the array. A microprocessor-based controller is used to carry out the load-matching.

Electrophilic Substitution Reactions of Copper(II) Acetylacetoneimine Complexes with Arene Diazonium Ions

Copper(II) complexes of ethylene/propylene-bis(acetylacetoneimine), Cu(baen) or Cu(bapn), react quickly and quantitatively in aqueous methanol at the methine position with arene diazonium ions in a stepwise manner to yield mono- and di-substituted copper(II) complexes. All the complexes are paramagnetic with μeff∼1.88 B.M. In all the complexes the diazo substituted part of the ligand coordinates to the metal through the agr-nitrogen of the azo group and the imine nitrogen, forming glyoxaliminearylhydrazone type of ligand system. The complexes have been characterized by elemental analysis, electronic, esr, ir and mass spectroscopic methods.

A Hybrid Multilevel Inverter Topology for an Open-End Winding Induction-Motor Drive Using Two-Level Inverters in Series With a Capacitor-Fed H-Bridge Cell

In this paper, a new five-level inverter topology for open-end winding induction-motor (IM) drive is proposed. The open-end winding IM is fed from one end with a two-level inverter in series with a capacitor-fed H-bridge cell, while the other end is connected to a conventional two-level inverter. The combined inverter system produces voltage space-vector locations identical to that of a conventional five-level inverter. A total of 2744 space-vector combinations are distributed over 61 space-vector locations in the proposed scheme. With such a high number of switching state redundancies, it is possible to balance the H-bridge capacitor voltages under all operating conditions including overmodulation region. In addition to that, the proposed topology eliminates 18 clamping diodes having different voltage ratings compared with the neutral point clamped inverter. On the other hand, it requires only one capacitor bank per phase, whereas the flying-capacitor scheme for a five-level topology requires more than one capacitor bank per phase. The proposed inverter topology can be operated as a three-level inverter for full modulation range, in case of any switch failure in the capacitor-fed H-bridge cell. This will increase the reliability of the system. The proposed scheme is experimentally verified on a four-pole 5-hp IM drive.