Damage Threshold of Ni Thin Film by Terahertz Pulses

Damage in a thin nickel film irradiated by subpicosecond pulses of terahertz (THz) radiation in the range of 1–3 THz at electric-field strengths up to 20 MV/cm at the center of a focal spot is observed. The damage threshold fluence is evaluated for single-pulse experiments. The damage pattern induced by multiple THz pulses has the appearance of a complex periodic structure in the form of elongated channels of metal film discontinuity that are perpendicular to the in-plane electric field direction of THz radiation.     

Separation of Samarium,Europium, and Gadolinium by Extraction with Organophosphorus Acids

Theoretical Foundations of Chemical Engineering - The features of distribution are studied and a complex technology for the separation of samarium, europium, and gadolinium is proposed. This...     

Circumnavigation of a speedy unpredictable target by a group of speed‐ and acceleration‐limited robots

An unpredictably maneuvering speedy target travels in a plane, which also hosts a team of fully actuated robots whose velocities and accelerations are upper‐bounded in magnitude. The robots should approach the target and then follow it at a prespecified distance. They also should achieve an even self‐distribution around the target and a given angular velocity of rotation about the target. Every robot has access to the relative position of the target and other robots (in the latter case, within a finite “visibility” range) and to the angular speed of its own pure rotation; access to the coordinates of its own linear velocity in its own local frame is also employed in some cases. The robots are not equipped with communication facilities and cannot distinguish among one another; assignment of different roles to various robots is infeasible. Necessary conditions for the mission feasibility are first obtained. A distributed control law is then presented, and its global convergence and collision avoidance property are rigorously justified under slight enhancement of the just mentioned necessary conditions. The performance of the control law is illustrated by computer simulations.     

Functional Surfaces with Enhanced Heat Transfer for Spray Cooling Technology

In this study the effects of nano/microstructuring and surface chemistry on wettability, evaporation rate and the Leidenfrost temperature are experimentally investigated. The functional surfaces with two alternative patterns were originally fabricated via direct femtosecond laser surface processing of polished silicon wafer in air at a fluence slightly above ablation threshold. The droplet lifetime method was used to measure the evaporation rate of a water droplet (4.5 μL) at surface temperatures of 25–350°C and to determine the Leidenfrost temperature. Generally, after processing the functional surfaces with hierarchical surface morphology demonstrate enhanced wetting behavior, evaporation rate enhancement and positive shifts in the Leidenfrost temperature. The functional surfaces with a microgrooved surface pattern, extensively covered by flake-like nanostructures, exhibit strong superhydrophilicity, resulted in a significant temperature-dependent enhancement of evaporation rate (up to 6 times) and an increase of about 30°C in the Leidenfrost temperature relative to the polished surface. The functional surfaces with a microcratered surface pattern being only hydrophilic demonstrate a nearly twofold temperature-independent enhancement of evaporation rate. Thermostability tests showed the heating of the functional surfaces above 340°C to be resulted in a drastically deteriorated wettability and a reduction of evaporative heat transfer performance under repeated experiments.     

Effect of Orthorhombicity on the Electronic Structure and Superconducting Properties of High- $$T_c$$ T c Cuprate Family

Journal of Superconductivity and Novel Magnetism - Electronic structure in the normal state and properties in the superconducting state of the orthorhombic phase in HTSC cuprates are studied within...     

Simulation of Thermionic Thermal Protection in a Supersonic Air Flow around a Spherically Blunted Cone

High Temperature - A mathematical model of a thermionic thermal protection system has been developed to study the characteristics of heat and mass transfer in a spatial, high-enthalpy air flow...     

Reflection electron-energy-loss spectroscopy of Fe<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Si<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript> thin films

The values of the product of the inelastic mean free path and the differential cross section for inelastic scattering of electrons have been determined from the reflection electron-energy-loss spectra of thin films of the Fe _x Si_{1 − x} system (0 ≤ x ≤ 1). A new approach to the quantitative analysis of components in such composite media is proposed.     

Radiation annealing of AMg6, 1441, and VD1 aluminum alloy strips using a ribbon source of accelerated ions

The results of our earlier studies are summed and new data are presented on the influence of beams of accelerated Ar⁺ ions on the mechanical properties and structure of various commercial aluminum alloys. A short-time (5–60 s) ion-beam processing of cold-deformed alloys is shown to lead to their softening, which is analogous to that upon intermediate annealing at 320–400°C for 2–3 h used in cold rolling. An experimental ribbon ion source, which is intended for in situ processing of rolled sheets in a rolling line to remove strain hardening instead of long-term furnace annealing, is described.     

Diaminofuroxan: Synthetic Approaches and Computer‐Aided Study of Thermodynamic Stability

Different approaches to synthesize diaminofuroxan are presented herein. Mathematical and quantum chemical methods were used to study the possible reasons for failures in the syntheses of diaminofuroxan. Additionally, structural isomers of this compound were generated. With the help of the results of quantum chemical calculations at levels of DFT B3LYP 6‐31G(d) and MP2 6‐31G(d), screening of the most stable isomeric forms in the gaseous phase and in water was performed. It was shown that diaminofuroxan is not the thermodynamically most stable isomer among its structural analogues.