In this paper, the authors analyse the propagation of surface Love waves in an elastic layered waveguide (elastic guiding layer deposited on an elastic substrate) covered on its surface with a Newtonian liquid layer of finite thickness. By solving the equations of motion in the constituent regions (elastic substrate, elastic surface layer and Newtonian liquid) and imposing the appropriate boundary conditions, the authors established an analytical form of the complex dispersion equation for Love surface waves. Further, decomposition of the complex dispersion equation into its real and imaginary part, enabled for evaluation of the phase velocity and attenuation dispersion curves of the Love wave. Subsequently, the influence of the finite thickness of a Newtonian liquid on the dispersion curves was evaluated. Theoretical (numerical) analysis shows that when the thickness of the Newtonian liquid layer exceeds approximately four penetration depths 4δ of the wave in a Newtonian liquid, then this Newtonian liquid layer can be regarded as a semi-infinite half-space. The results obtained in this paper can be important in the design and optimization of ultrasonic Love wave sensors such as: biosensors, chemosensors and viscosity sensors. Love wave viscosity sensors can be used to assess the viscosity of various liquids, e.g. liquid polymers.
Biology is a science on life. This definition, concise and most commonly used, is satisfactory for almost everybody. It is otherwise when one asks: What is life? Then it appears that no one feature can be indicated which distinguishes “the living” from “the non-living.” The author presents the sources of these difficulties and then gives his own attempt to solve the problem of definition of live—which is based on the idea of levels of the biological organization. In author’s view, to characterise the objects of research in biology we should apply not one concept of life (or of living organism) but three concepts: of organized biological matter (for the molecular and sub-cellular levels), of living organism (for the level of the specimen), and of life (for the sphere of phenomena which occur on the population-species-biocenotic level).
The Henaya Irrigated Perimeter (HIP) is an agricultural area irrigated by treated wastewater (TWW) of Ain El Hout treatment plant. Various analyses have shown that i) this water has low concentration of heavy metals and toxic elements, ii) the average values of the physicochemical parameters for 136 samples are satisfactory (29.2 mg O2∙dm–3 for chemical oxygen demands – COD, 13.14 mg O2∙dm–3 for biological oxygen demands – BOD, 14.2 mg∙dm–3 of suspended matter – SM, 1.82 mg∙dm–3 of N-NO3, 7.7 for pH and 927.74 μS∙cm–1 for electric conductivity – EC). Thirdly, it contains a high number of bacteria and nematodes (7200 CFU∙(100 dm3)–1 for faecal coliforms and 30 eggs∙dm–3 for intestinal Nematodes) which makes it dangerous for groundwater contamination. The objective in this work is to characterize the TWW and evaluate the impact of it use for irrigation on the quality of Hennaya groundwater. Before this, one has to prove that there is an amount of TWW that feeds the water table to show that there is a risk of pollution. We then estimated the aquifer minimum recharge value by TWW using the Thormthwaite meth-od. The estimation has given 92 mm which is an important quantity. The results of the groundwater microbiological anal-yses reveal no sign of contamination. The cause is the efficiency of the degradation of pollutants of the Vadose zone. The soil purifying power Md of the HIP was evaluated by the Rehse method and gave values ranging from 2.1 to 12.7 which indicated a complete purification.
The minimum energy control problem for the positive continuous-time linear systems with bounded inputs is formulated and solved. Sufficient conditions for the existence of solution to the problem are established. A procedure for solving of the problem is proposed and illustrated by a numerical example.