Roux-type constructions for covering arrays of strengths three and four

A covering array CA(N;t,k,v) is an N × k array such that every N × t sub-array contains all t-tuples from v symbols at least once, where t is the strength of the array. Covering arrays are used to generate software test suites to cover all t-sets of component interactions. Recursive constructions for covering arrays of strengths 3 and 4 are developed, generalizing many “Roux-type” constructions. A numerical comparison with current construction techniques is given through existence tables for covering arrays.      

On t-Covering Arrays

This paper concerns construction methods for t-covering arrays. Firstly, a construction method using perfect hash families is discussed by combining with recursion techniques and error-correcting codes. In particular, by using algebraic-geometric codes for this method we obtain infinite families of t-covering arrays which are proved to be better than currently known probabilistic bounds for covering arrays. Secondly, inspired from a result of Roux [16] and also from a recent result of Chateauneuf and Kreher [6] for 3-covering arrays, we present several explicit constructions for t-covering arrays, which can be viewed as generalizations of their results for t-covering arrays.     

Effect of “rest” on creep of glass-reinforced plastic SVAM

The effect of rest on creep of glass-reinforced plastic SVAM is investigated. It is shown that for the cyclic loading regime used (24-h load, 24-h rest) the effect of rest is closely related with orientation of the specimen and with the magnitude of the load.Institute of Mechanics, Academy of Sciences of the Armenian SSR, Erevan. Translated from Mekhanika Polymerov, No. 3, pp. 547–550, May–June, 1974.     

Isoquinoline derivatives

Amides IV, which are converted to 1-diphenylmethyl-4,6,7-substituted 1,2,3,4-tetrahydroisoquinolines (II) by cyclization and subsequent reduction with lithium aluminum hydride, were obtained by condensation of diphenylacetyl chloride with the corresponding substituted phenylethylamines (III). Amines VI, the open analogs of the tetrahydroisoquinolines, were synthesized by reduction of IV.See [3] for Communication III.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1670–1673, December, 1970.     

Strengthening of glass-fiber-reinforced plastic under biaxial tension

Conclusions 1. The effect of axial tension, applied at the first stage of loading under biaxial tension, on the increase in the hoop strength of an oriented glass-fiber-reinforced plastic was observed. The increase in the hoop strength depends both on the value of the axial tensile load, and on the angle of winding of the fibers.2. The effect observed is in this case apparently independent of the condition of loading of the sample under biaxial tension.Institute of Mechanics, Academy of Sciences of the Armenian SSR, Erevan. Translated from Mekhanika Polimerov, No. 6, pp. 1025–1029, November–December, 1976.     

X-ray diffraction study of temperature dependence of Nairit polychloroprene permolecular structure

With use of the X-ray technique the permolecular structure of Nairit polychloroprene has been investigated. It is shown that the relative degree of crystallinity decreases with the increase in the polymerization temperature. At relatively low temperatures (18–30°C), in Nairits intensive formation of nuclei occurs and simultaneously existing crystallites collapse. Although mean sizes of crystallites decrease, the degree of crystallinity increases. At higher temperatures (above 30°C) melting of existing crystallites and decrease in the number of nuclei lead to decrease in crystallinity and mean sizes of crystallites.     

Spectral study of the dioxygen and carbonyl adducts of ferrous porphyrins ligated by neutral S-donors

A series of the six-coordinated ferrous porphyrin complexes (L)Fe(II)TPP(O₂) and (L)Fe(II)TPP(CO) (L, (CH₃)₂S, or C₂H₅SH, TPP, meso-tetraphenylporphyrin dianion) was prepared. UV–vis and FTIR spectroscopy were applied to follow the reaction of O₂ and CO adducts of Fe(II) porphyrins with neutral thiol and thioether. Using sublimed layers methodology and low temperature technique, as well as isotope substitution, the formation of six-coordinate complexes was monitored in situ. The comparison of CO and O₂ stretching frequencies of thiol and thioether adducts indicates that the degree of electron donation is similar for these ligands. The complexes of Me₂S and EtSH with Fe(TPP)(O₂) are stable at 150 K and slowly decompose at elevated temperatures. In contrast, the carbonyl complexes of Fe(Por) with Me₂S and EtSH are relatively stable and retain six-coordination at room temperature. The electronic effects of axial S-donor ligands on the coordinated O₂ and CO are discussed and compared with the effects of N- and O-donors.     

Using an absorbing axicon for suppression of spatial modulations in the region of Bessel beam

Light intensity modulations in the region of a Bessel beam formed when laser radiation passes through an absorbing axicon are studied. Since light absorption occurs predominantly in close-to-tip regions of absorbing axicon, spatial modulations are suppressed and the Bessel beam region becomes smoother and more uniform.     

Hydrogen sensitive gas sensor based on porous silicon/TiO2−x structure

Porous silicon (PS) layer was formed by electrochemical anodization on a p-type Si surface. Thereafter, n-type TiO_2−x thin film was deposited onto the PS surface by electron-beam evaporation. Pt catalytic layer and Au electrical contacts for further measurements were deposited onto the PS/TiO_2−x structure by ion-beam sputtering. Current–voltage characteristic, sensitivity to different concentration of hydrogen and resistance change of obtained structures versus time were examined. Results of measurements have shown that the current–voltage characteristics of structures are similar to that of diode. High sensitivity to hydrogen of obtained structures was also detected. Note that all measurements were carried out at room temperature.