Numerical investigation of the Liebau phenomenon

The Liebau phenomenon is the occurrence of valveless pumping through the application of a periodic force at a place which lies asymmetric with respect to system configuration. This paper is concerned with two different physical configurations and respective models. Comparison and derivation among the models is discussed. Accurate numerical schemes which solve these models are presented. By means of numerical simulations it is investigated under which conditions valveless pumping takes place.     

Implementations of PACMAN

Passive and Active Compensability Multicriteria ANalysis (PACMAN) is a multiple criteria methodology based on a decision maker oriented notion of compensation, called compensability. An important feature of PACMAN is a possible asymmetry of the connected decision procedure, since compensability is determined for each ordered pair of criteria, distinguishing the compensating criterion from the compensated one. Here we give a notion of implementation of PACMAN, which allows a concrete modelization of a multiple criteria decision problem. We study regular implementations of PACMAN and their monotonicity properties. We also examine several regular implementations, which satisfy some additional properties. Particular emphasis is given to a regular implementation of PACMAN that produces the lexicographic ordering.     

Tantalum irradiation by high power pulsed laser at 1315 and 438 nm wavelengths

The high power pulsed laser Prague asterix laser system (PALS), operating at the fundamental (1ω) and third (3ω) harmonics (1315 and 438 nm wavelengths, respectively), is employed in a single-shot mode to irradiate tantalum targets in vacuum. The laser pulse width is 400 ps and the laser pulse energy ranges between 43 and 736 J at 1ω and between 12 and 230 J at 3ω. High ablation yields (0.1–0.6 mg per pulse) are measured as a function of the laser pulse energy at both wavelengths; at 438 nm higher etching rates are observed. The produced craters are analysed by the scanning electron microscope (SEM) and by the high sensitivity surface profiler system. They are investigated in dimension, shape and angle aperture as a function of the incident laser energy. Different possible mechanisms responsible for the different crater shapes are presented and discussed.     

Conservation laws and growth of discontinuities in a reactive polytropic gas

Summary We shall consider a conservation law associated with a non-equilibrium gas flow with chemical reaction. Some results on the growth of discontinuities and the occurrence of breakdown of the solution are pointed out.

---

Sommario Si prende in esame una legge di conservazione che viene associata alle equazioni che governano un gas in non equilibrio in cui avviene una reazione chimica. Si mettono in evidenza alcuni risultati sull'evoluzione delle discontinuita' e sulla eventuale perdita di regolarita' della soluzione.

---

---

This work was partially supported by the G.N.F.M. (Gruppo Nazionale Fisica Matematica) of C.N.R.     

Symmetry methods in mathematical modeling of Aedes aegypti dispersal dynamics

A model of Aedes aegypti, the main vector of the yellow fever, is considered. The Lie point symmetries are found and some classes of exact solutions are shown.     

Fractional ionization in plasmas produced by pulsed laser ablation

A pulsed infrared laser (Q-switched Nd:Yag) is employed to irradiate different metal targets having atomic number from Z =13 up to Z =82. The high laser fluence deposited on the metals, of the order of 100 v J/cm, produces high ablation yield and a plasma generation at the target surface. The emitted species are neutral and ionized atoms. Both components have been investigated in terms of yield emission, time-of-flight measurements and angular distribution. Results indicate that the main emission occurs mainly along the normal to the target surface, that the etching, at high fluence, is of the order of 10 v atoms/ pulse, that the atoms velocities are of the order of 10 v m/s, that the maximum ion energies are of the order of keV. During the laser irradiation, expanding and non-equilibrium plasma is produced in front of the target. The plasma has a fraction ionization depending by the metal species and generally within 10% and 80%. The plasma'temperature, at high fluence, can be theoretically calculated and reaches about 10 v K. The fractional ionization of the plasma, experimentally measured, has been investigated as a function of the laser fluence and of the energy binding of the target molecules. The ion emission yield is presented and discussed in view of the possibility to realize a laser ion source for ion accelerators.     

Laser and ion beams graphene oxide reduction for microelectronic devices

Reduced graphene oxide (rGO) is a two-dimensional material, which is attracting increasing attention due to its special properties. It can be obtained by laser or ion beam irradiations of pristine graphene oxide (GO). It shows high mechanical resistance, considerable electric and thermal conductivity. All these rGO characteristics together with the high number of molecular species that can be embedded between its layers, make graphene oxide a potential material for electronic sensors or efficient support on which conductive strips, condensers, and micrometric electronic devices can be designed. In particular, as it is described in this paper, it is possible to carry out high spatial resolution lithography in GO by using a focused laser or micro ion beam in order to design macro, micro, and submicron geometrical structures. The use of the reduced graphene oxide for the laser and ion beam fabrication of electrical resistances and capacitances is presented.