In this year we commemorate the 50 year anniversary of death of the outstanding Polish physical chemist professor Wojciech Świetosławski (1881–1968). His work was reviewed by prof. prof A. Dorabialska, K. Zieborak, W. Kemula and others. In this note one of his last and youngest students brings about reminiscences of the political problems he had to face, which could not have been described or even mentioned under the Soviet communist rule over Poland.
Hydrological conditions in the region between the King George and Elephant Islands were defined on the basis of 24 STD measurements and 20 XBT profiles made in the time period from 26 October to 16 November 1986. In the entire investigated region the surface water temperature was below zero, often close to freezing point. The presence of summer modification of surface water with its characteristic thermal minimum was not found. Between the Scotia Front and the relatively well pronounced stream of geostrophic currents the anticyclonic meander was observed above the edge of the shelf at the depth of 100 m. Its spread was about 10 nM and within this meander the downwelling of surface water was noticed. As a compensating water movement, the upwelling of warmer waters was observed in the Drake Passage at 400 m.
Scientists are increasingly specializing in narrower fields, and communication is often difficult between physicists researching elementary particles and those studying semiconductors, not to mention between physicists and biologists or doctors. This makes interdisciplinary work difficult. And yet sometimes they succeed. One thread of work underway at the PAS Institute of High Pressure Physics offers a good example.
The study presents the results of laboratory testing of the phenomenon of cracking in the process of cross rolling. A new method of determining the critical value of the damage function was developed, in which a disc-shaped sample is subjected to rotational compression in a channel. In this method the Mannesmann effect was used. The laboratory tests were conducted for C45, 50HS and R260 grade steel in the temperature range 950°C-1150°C. In order to research various methods of simulating the phenomenon of cracking in the process of cross rolling, physical modelling was also employed. The model material was commercial plasticine, cooled to the temperature 0°C-20°C. Comparing the test results for both the real and model material allowed one to determine the range of the forming temperature for the model material, in which the cracking process is similar to the case of the real material.
A recent IEEE Access Paper by Gunn, Allison and Abbott (GAA) proposed a new transient attack against the Kirchhoff-law-Johnson-noise (KLJN) secure key exchange system. The attack is valid, but it is easy to build a defense for the KLJN system. Here we note that GAA’s paper contains several invalid statements regarding security measures and the continuity of functions in classical physics. These deficiencies are clarified in our present paper, wherein we also emphasize that a new version of the KLJN system is immune against all existing attacks, including the one by GAA.
AISI 316L/TiB2/2p composites were manufactured by HP-HT using different pressures (5 and 7 GPa) and temperatures (900-1300°C), with constant reinforcing particle content 2 vol%. The mechanical properties of the composites were evaluated on the basis of hardness (HV0.3) and compression tests (20°C, 10−5 s−1). The results showed that the role of sintering pressure increased with increasing process temperature. At temperatures of 900°C and pressures of 5 and 7 GPa the difference in measured values of compressive strength was 1-2%, while at 1300°C they reached 20%. At constant pressure of 5 GPa, a change in hardness and compressive strength of 40% were obtained with a temperature change of 900 to 1300°C. Changes in mechanical properties in the composite occurred without substantial changes in density, microstructure, reinforcement phase distribution, and phase composition in the matrix.
The paper has presented the results of theoretical studies and experimental tests of the plastic deformation of multi-layered Ti/Al/Mg specimens. Theoretical studies were carried out using the Forge2011® computer program. Physical modeling, on the other hand, was performed using the Gleeble3800 simulator. Cuboidal specimens were cut off from the plates obtained in the explosive welding method. Based on the obtained investigation results it has been found non uniform deformation of the particular layer as a result their different value of flow stress.
AbstractThe stability of fractional standard and positive continuous-time linear systems with state matrices in integer and rational powers is addressed. It is shown that the fractional systems are asymptotically stable if and only if the eigenvalues of the state matrices satisfy some conditions imposed on the phases of the eigenvalues. The fractional standard systems are unstable if the state matrices have at least one positive eigenvalue.
AbstractThe classical Cayley-Hamilton theorem is extended to Drazin inverse matrices and to standard inverse matrices. It is shown that knowing the characteristic polynomial of the singular matrix or nonsingular matrix, it is possible to write the analog Cayley-Hamilton equations for Drazin inverse matrix and for standard inverse matrices.
AbstractThe Caputo-Fabrizio definition of the fractional derivative is applied to minimum energy control of fractional positive continuous- time linear systems with bounded inputs. Conditions for the reachability of standard and positive fractional linear continuous-time systems are established. The minimum energy control problem for the fractional positive linear systems with bounded inputs is formulated and solved.
AbstractThis paper describes a new method of determining the reactive power factor. The reactive power factor herein is calculated on the basis of time samples and not] with the Fourier transform of signals, like it was done previously. The new reactive power factor calculation results from the receiver admittance-operator decomposition into the product of self-adjoint and unitary operators. This is an alternative decomposition to another one, namely into a sum of the Hermitian and skew-Hemiitian operators.
AbstractThe paper presents the problem of estimating in-situ compressive strength of concrete in a comprehensive way, taking into account the possibility of direct tests of cored specimens and indirect methods of non-destructive tests: rebound hammer tests and ultrasonic pulse velocity measurements. The paper approaches the discussed problem in an original, scientifically documented and exhaustive way, in particular in terms of application.
AbstractPositive descriptor fractional discrete-time linear systems with fractional different orders are addressed in the paper. The decomposition of the regular pencil is used to extend necessary and sufficient conditions for positivity of the descriptor fractional discrete-time linear system with different fractional orders. A method for finding the decentralized controller for the class of positive systems is proposed and its effectiveness is demonstrated on a numerical example.
AbstractThis paper describes how to calculate the number of algebraic operations necessary to implement block matrix inversion that occurs, among others, in mathematical models of modern positioning systems of mass storage devices. The inversion method of block matrices is presented as well. The presented form of general formulas describing the calculation complexity of inverted form of block matrix were prepared for three different cases of division into internal blocks. The obtained results are compared with a standard Gaussian method and the “inv” method used in Matlab. The proposed method for matrix inversion is much more effective in comparison in standard Matlab matrix inversion “inv” function (almost two times faster) and is much less numerically complex than standard Gauss method.
This article has two outreach aims. It concisely summarizes the main research and technical efforts in the EC H2020 ARIES Integrating Activity – Accelerator Research and Innovation for European Science and Society  during the period 2017/2018. ARIES is a continuation of CARE, TIARA and EuCARD projects [2-3]. The article also tries to show these results as an encouragement for local physics and engineering, research and technical communities to participate actively in such important European projects. According to the author’s opinion this participation may be much bigger [4-27]. All the needed components to participate – human, material and infrastructural are there [4,7]. So why the results are not satisfying as they should be? The major research subjects of ARIES are: new methods of particles acceleration including laser, plasma and particle beam interactions, new materials and accelerator components, building new generations of accelerators, energy efficiency and management of large accelerator systems, innovative superconducting magnets, high field and ultra-high gradient magnets, cost lowering, system miniaturization, promotion of innovation originating from accelerator research, industrial applications, and societal implications. Two institutions from Poland participate in ARIES – these are Warsaw University of Technology and Institute of Nuclear Chemistry and Technology in Warsaw. There are not present some of the key institutes active in accelerator technology in Poland. Let this article be a small contribution why Poland, a country of such big research potential, contributes so modestly to the European accelerator infrastructural projects? The article bases on public and internal documents of ARIES project, including the EU Grant Agreement and P1 report. The views presented in the paper are only by the author and not necessarily by the ARIES.