Theory of the Snoek Effect in Ternary B.C.C. Alloys : III Hydrostatic Relaxation

Interstitial atoms in ternary b.c.c. alloys exhibit hydrostatic relaxation, if an applied stress has a dilatational stress component. The effect is absent in binary alloys. Hydrostatic relaxation, in contrast to orientation relaxation effect, involves long-range diffusion ; in order to understand various aspects of the process, calculations are made for imaginary lattices. Internal friction curves are computed for different solute concentrations in a real three-dimensional lattice. The height and the temperature of the peak are compared for hydrostatic relaxation and orientation relaxation

Theory of the Snoek Effect in Ternary B.C.C. Alloys : II. Simplified Treatment

A theoretical basis is developed for the analysis of the spectrum of the Snoek effect in ternary b.c.c. alloys. The extensive treatment of Part I is simplified by assuming that the interstitial atoms in the third-nearest-neighbour position move independently of the substitutional atom. Numerical values obtained with this assumption are fairly close to those obtained by elaborate calculations of Part I. The damping spectrum may be decomposed either into components associated with the degree of rotation of interstitial atoms in each shell around substitutional atoms, or into Debye peaks. The latter decomposition may show an anomaly when the relaxation times have a certain relationship

A Theory of Internal Friction Peak Due to Thermal Unpinning of Dislocations and Its Application to P_1 Peak in Copper

A theory of internal frictions due to thermal unpinning of dislocations was developed. The results of quantitative calculations are as follows. (1) An internal friction peak as a function of temperature is formed, of which the shape is different from that of the Debye type single relaxation. (2) The distortion of the peak shape increases linearly with the strain amplitude. (3) The peak height of the internal friction and the magnitude of the associated ΔM effect are related by the equation, Q^_=0.126Δ_M. (4) The mean pinning distance can be estimated from experimental results. The predictions of the theory were compared with the experimental characteristics of the P_1 peak in deformed copper, and a satisfactory agreement was found especially as to the distortion of the peak with the strain amplitude. The estimated pinning distance was found to decrease from 200b to 20b as the deformation increases, where b is the magnitude of Burgers vector, and was found to remain constant or rather slightly increase with the decay (or annealing) of the P_1 peak

Constitution of the Indium-Rich Portion of the Indium-Magnesium System

The equilibrium phase diagram of the indium-magnesium system in the range up to 40 at.% Mg has been established by X-ray diffraction and thermal analysis. The solid-solubility of magnesium in indium does not exceed about 5 at.%. An intermediate solid solution, γ, with a face-centered cubic structure exists over a wide range of composition. An ordered phase, γ\u27, with superstructure of Cu_3Au-type, is formed near 28 at.% Mg at temperatures below 114℃. The axial ratio c/a of the primary solid solution of indium in magnesium changes as a function of electron/atom ratio as in the parallel case of the indium-cadmium system. Reasons are advanced to explain the conflict between the present results and those of earlier investigators

Internal Friction Peaks of Cold-Worked Dilute Copper-Aluminium Alloys(Metallurgy)

The internal friction of cold-worked Cu-Al alloys is measured with an inverted torsion pendulum in the temperature range between -180℃ and +100℃. Among 10 specimens with different contents of aluminium ranging from 0.01 to 2 at.%, distinct peaks are observed for the two compositions, 0.13 and 0.18 at.%Al, the peak height being larger for the former ; detailed studies are made on 0.13 at.%Al specimens. The peak is introduced by plastic deformation and disappears on annealing at temperatures around +150℃. For a specimen annealed in an oxidizing atmosphere prior to the final deformation, the peak is no longer observed. The peak is considered to be a combined effect of dislocations and aluminium atom-vacancy complexes

The Internal Friction and Elastic Modulus of Amorphous Pd-Si and Fe-P-C Alloys

The internal friction and the shear modulus of the amorphous Pd_-Si_, Fe_-P_-C_7 and Fe_-Ni_-P_-C_5 alloys have been measured at about 0.5 Hz over a temperature range from room temperature to about 550℃. The internal friction rises steeply with temperature and shows maxima around the crystallization temperature. The activation energy for the steeply rising internal friction has been estimated by the two different procedures ; from the shift of the curve by the frequency change and from the slope of the 1n Q^ versus 1/T plot. The two values are very different, which indicates the existence of a wide distribution of activation energies. Crystallization of the amorphous alloys resulted in an increase of about 30% in the shear modulus

An Experimental Study on the Ordered Alloy Ni_2Cr

The ordered alloy Ni_2Cr has been investigated by means of electron diffraction, electron microscopy, calorimetry, resistometry and tensile tests. The formation of the Pt_2Mo type superstructure is revealed by an electron diffraction study on the single crystalline specimens. The size of ordered domains is of the order of magnitude of several hundred A even in the well annealed state. The so-called \u27K-state\u27 which is characterized by the initial increase in electrical resistivity upon isothermal annealing is attributed to the existence of very fine ordered domains. Superdislocations consisting of triple dislocations are sometimes observed in various stages of ordering, and the mechanical properties are briefly discussed in the light of electron microscopic observation. The energy and entropy of transformation are evaluated as about 1.0 kcal/g・atom and 1.2 cal/g・atom-deg on the alloy of 32.1 at% Cr annealed at 500℃ for about 3000 hr

Preselection algorithm based on predictive control for direct matrix converter

This paper presents an enhanced predictive control strategy to reduce the calculation effort for direct matrix converters. The main idea is to preselect the switching states to decrease the calculation effort during each sample period. The proposed preselection algorithm enables a predefined cost function to consider only the preselected switching states to perform the expected control. On the basis of the preselection of switching states at each sample period, the proposed method can effectively reduce the calculation effort as well as show a good performance. The proposed predictive control scheme using only preselected switching states needed to generate the desired source/load current waveforms and control the input power factor. The feasibility of the proposed method is experimentally verified and results are presented in the paper

A Three-Component Gene Expression System and Its Application for Inducible Flavonoid Overproduction in Transgenic Arabidopsis thaliana

Inducible gene expression is a powerful tool to study and engineer genes whose overexpression could be detrimental for the host organisms. However, only limited systems have been adopted in plant biotechnology. We have developed an osmotically inducible system using three components of plant origin, RD29a (Responsive to Dehydration 29A) promoter, CBF3 (C-repeat Binding Factor 3) transcription factor and cpl1-2 (CTD phosphatase-like 1) mutation. The osmotic stress responsible RD29a promoter contains the CBF3 binding sites and thus RD29A-CBF3 feedforward cassette enhances induction of RD29a promoter under stress. The cpl1-2 mutation in a host repressor CPL1 promotes stress responsible RD29a promoter expression. The efficacy of this system was tested using PAP1 (Production of Anthocyanin Pigment 1) transgene, a model transcription factor that regulates the anthocyanin pathway in Arabidopsis. While transgenic plants with only one or two of three components did not reproducibly accumulate anthocyanin pigments above the control level, transgenic cpl1 plants containing homozygous RD29a-PAP1 and RD29a-CBF3 transgenes produced 30-fold higher level of total anthocyanins than control plants upon cold treatment. Growth retardation and phytochemical production of transgenic plants were minimum under normal conditions. The flavonoid profile in cold-induced transgenic plants was determined by LC/MS/MS, which resembled that of previously reported pap1-D plants but enriched for kaempferol derivatives. These results establish the functionality of the inducible three-component gene expression system in plant metabolic engineering. Furthermore, we show that PAP1 and environmental signals synergistically regulate the flavonoid pathway to produce a unique flavonoid blend that has not been produced by PAP1 overexpression or cold treatment alone