Impacts of structural-acoustic coupling on the performance of energy density-based active sound transmission control

This paper investigates numerically the performance of the active sound transmission control into a rectangular cavity through a flexible panel under the energy density-based error-sensing algorithm. Full coupling between the sound transmitting panel and the enclosed space is considered. A pure vibration actuator, a pure acoustic source and a combined control source system are used as the secondary control source in the active control and their performances are studied. Formulae for the coupled eigenfrequencies of the cavity and the flexible panel are also derived. The strength of the structural-acoustic coupling, the ratio between the first eigenfrequencies of the cavity and the panel and the difference between the excitation frequency and the coupled eigenfrequencies, especially the latter, are found to have crucial impacts on the performance of the active control regardless the type of control source used.     

Generation of angular momentum of fission fragments in a cluster model

Based on the dinuclear system concept, the role of bending vibrations in creation of the angular momentum of primary fission fragments is investigated. For ²⁵²Cf spontaneous fission, the angular momenta of the fragments are calculated as a function of the neutron multiplicity and compared with available experimental data. Different cluster compositions of the ²⁵²Cf fission modes at the scission point are considered.     

Intrinsic Fluorescence of Actin

In this work actin is used to illustrate connection of protein fluorescence characteristics with its structure. On one hand, it has been demonstrated what kind of information about the contribution of each tryptophan residues to the bulk fluorescence spectrum can be obtained from the special analysis of protein three-dimensional structure. On the other hand, potentials of intrinsic fluorescence for elucidation of proteins structure, dynamics and processes of folding-unfolding are shown. In particular, using this method a new essentially unfolded kinetic intermediate state of actin was detected and characterized, and the place of inactivated actin and its kinetic predecessor in the process of folding-unfolding was determined. It has been revealed that inactivated actin is not intermediate state between the native and completely unfolded states, as it has been accepted before, but a result of protein misfolding. On the basis of the obtained data a new model of actin folding-unfolding pathway has been proposed.     

Double adaptive notch filter for mechanical grain flow sensors

Nowadays, commercial combine harvesters are equipped with special sensors for the purposes of precision farming. Sensors are installed to measure the harvested surface and mass flow each second. Hence, grain yield maps are constructed, approximating the actual grain yield on the field before harvesting.Most grain flow sensors are installed on the paddle elevator before storage in the grain tank. At the elevator exit, paddles throw packs of grain against a curved plate on which a force transducer is attached. Therefore, the measured flow signal is heavily disturbed by the paddle rate and resonance frequency of the mechanical sensor.In this study, a computationally cheap method is presented to track both frequencies in the measured flow signal. Based on these frequency trackers, a double notch filter is tuned continuously to remove both disturbances. Moreover, the knowledge about the frequency content can be used to monitor the condition of the mechanical sensor and the paddle elevator.     

An EOQ model with process reliability considerations

The classical economic order quantity (EOQ) model assumes that items produced are of perfect quality and that the unit cost of production is independent of demand. However, in realistic situations, product quality is never perfect, but is directly affected by the reliability of the production process. In this paper, we consider an EOQ model with imperfect production process and the unit production cost is directly related to process reliability and inversely related to the demand rate. In addition, a numerical example is given to illustrate the developed model. Sensitivity analysis is also performed and discussed.     

Mild and efficient synthesis of propargylamines by copper-catalyzed Mannich reaction

Terminal alkynes undergo mild and efficient aminomethylation with aqueous formaldehyde and secondary amines under CuI catalysis. In most cases high to nearly quantitative yields of tertiary propargylamines are obtained in DMSO solution at room temperature. Aromatic, aliphatic and silylated acetylenes as well as alkynols can be used. Primary amines are less reactive and satisfactory yields of secondary propargylamines are obtained only with phenylacetylene.     

Preparation of colloidal solutions of noble metals stabilized by polyoxometalates and supported catalysts based on these solutions

Conditions for the preparation of stable aqueous monometallic and bimetallic colloidal solutions (sols) of noble metals (Ru, Rh, Pd, Pt, Ir, Ag, and Au) in the presence of polyoxometalates containing W, Mo, V, and Nb were found. The stability of sols against coagulation at room temperature was studied. The metal/C samples prepared by metal adsorption from sols were studied by powder X-ray diffraction analysis and transmission electron microscopy. The following factors of importance for the preparation of a stable sol are discussed: (1) the formation of a sol of a metal polyhydroxo complex stabilized by a polyoxometalate (preliminary stage) and (2) the formation of polyoxometalate-metal clusters in the course of reduction of polyhydroxo complexes.Translated from Kinetika i Kataliz, Vol. 45, No. 6, 2004, pp. 921–929.Original Russian Text Copyright © 2004 by Maksimova, Chuvilin, Moroz, Likholobov, Matveev.     

InAs/GaAs (1 1 1)A heteroepitaxial systems

We studied the structural, electrical, and mechanical properties of an InAs thin film grown on GaAs (1 1 1)A substrates by molecular beam epitaxy. In contrast to conventionally used (0 0 1) surfaces, where Stranski–Krastanov growth dominates the highly mismatched heteroepitaxy, layer-by-layer growth of InAs can be established. One of the largest advantages of this unique heteroepitaxial system is that it provides a two-dimensional electron gas system in the near-surface region without the problem of electron depletion. We review the fundamental properties and applications of this unique heteroepitaxial system.     

Charge manipulation and imaging of the Mn acceptor state in GaAs by cross-sectional scanning tunneling microscopy

An individual Mn acceptor in GaAs is mapped by cross-sectional scanning tunneling microscopy (X-STM) at room temperature and a strongly anisotropic shape of the acceptor state is observed. An acceptor state manifests itself as a cross-like feature which we attribute to a valence hole weakly bound to the Mn ion forming the (Mn²⁺3d⁵+hole) complex. We propose that the observed anisotropy of the Mn acceptor wavefunction is due to the d-wave present in the acceptor ground state.