Thermoelastic Characterization of Changing Phase Distribution in Hardened Steel by Laser Ultrasonics

The increase of hardness of steel during a heat treatment intended to give components more performance is a result of a drastic change in grain size and microstructure, which in turn can be analyzed via changes in acoustic wave scattering. The degree of scattering is related to the grain size, alloy phases, elastic anisotropy, and phonon spectra, which are connected with the structural heterogeneity. In this study, an axially oriented hardening profile in a steel rod was induced by a Jominy test. All-optical photoacoustic excitation and detection schemes were used to establish the relation between the hardness, the elastic modulus, the elastic scattering, and the thermal diffusivity on a series of eight samples cut out from the gradient part of the rod. For each sample, the scattering of the photoacoustically excited traveling surface acoustic waves detected in a heterodyne diffraction and beam deflection setup was extracted from their damping behavior at different wavelengths and frequencies. Also, the thermal diffusivity was determined by fitting the slow time evolution of the laser-induced photo-thermoelastic displacement signal, and was found to be decreasing with decreasing grain size and increasing hardness.     

Antimicrobial Catanionic Vesicular Self-Assembly with Improved Spectrum of Action

A catanionic mixture based on three components, N-dodecyldiethanolamine, decanoic acid and azelaic acid, was prepared and investigated from a physico-chemical point of view and for its antimicrobial activity. The spontaneously formed vesicles were characterized by dynamic light scattering, zeta potential and electron microscopy. These experiments showed spherical vesicles with an average diameter of 200 nm and a zeta potential of +22 mV. The antimicrobial activity of the vesicle dispersion against different strains (Staphylococcus aureus, Escherichia coli, Staphylococcus epidermidis, Propionibacterium acnes and Candida albicans), was evaluated and compared with the activity of the components separately. The synergistic effect of these bioactive self-assembled catanionic vesicles on the spectrum of activity and on the cytoplasmic membrane is discussed.     

Process Modeling and Optimization of a Submerged Arc Furnace for Phosphorus Production

This article presents a process model of a phosphorus-producing, submerged arc furnace. The model successfully incorporates accurate, multifield thermodynamic, kinetic, and industrial data with computational flow dynamic calculations and thus further unifies the sciences of kinetics and equilibrium thermodynamics. The model is structurally three-dimensional and uses boundary conditions, initial values, and material specifications provided by industrial measurements, laboratory experiments, and a combination of empirical and thermodynamic data. It accounts for fully developed gas flows of gaseous product generated from within the packed bed; the energy associated with chemical reactions, heating, and melting, as well as thermal conductivity and the particle–particle radiation within the burden. The model proves the existence of a narrow, gas–solid reduction zone where the bulk of phosphorus is produced. It shows that fast reaction rates in this narrow reaction zone in combination with long residence times diminish the influence changing reaction rates have on the process. It indicates that most heat exchanged between the new pellets entering the furnace and the gaseous product produced in the reduction zone takes place in the top 0.5 m of the furnace bed. The gaseous product and flow information shows low and recirculating gaseous flow velocity areas that cause dust accumulation.     

Compact high-resolution spaceborne echelle grating spectrometer with acousto-optical tunable filter based order sorting for the infrared domain from 2.2 to 4.3 microm

A new compact spaceborne high-resolution spectrometer developed for the European Space Agency's Venus Express spacecraft is described. It operates in the IR wavelength range of 2.2 to 4.3 microm and measures absorption spectra of minor constituents in the Venusian atmosphere. It uses a novel echelle grating with a groove density of 4 lines/mm in a Littrow configuration in combination with an IR acousto-optic tunable filter for order sorting and an actively cooled HgCdTe focal plane array of 256 by 320 pixels. It is designed to obtain an instrument line profile of 0.2 cm(-1). First results on optical and spectral properties are reported.     

Analysis of synchronous machine modeling for simulation and industrial applications

This paper analyses the synchronous machine modeling by taken into account the machine parameters usually used in industry and those used in researcher’s domains. Two models are presented. The first one is developed in the (d, q) natural reference frames and the other one is referred to the (d, q) stator reference frame. To do this, two methods are proposed to compute the reduction factor of the field winding without any input from design information. It is shown that the reduction factors of the (d, q) damper windings do not influence on the terminal behavior of the machine. This means that it is possible to know the terminal behavior of the machine without knowing the real inductances and resistances of the damper windings. The accuracy of these models is validated by experimental tests.     

Synchronous generator modelling and parameters estimation using least squares method

In this paper, a technique for estimating the synchronous machine’s parameters using sudden short circuit test, is proposed. Before implementing estimation algorithms, a special method of the machine modelling is given. This last one allows to perform tests such as short-circuit, load impact and shedding test, in an easier way than the models usually developed in the literature. Thanks to the well known electrical equivalent circuit of the generator, the relationships between parameters generally used in the industry (i.e., reactances and time constants) and those used in researcher’s domains will be given. Finally, simulation results of the proposed method, allows to show that the algorithm is capable of providing very good estimated parameters fitting with the actual parameters.     

Fatigue‐based model for the droplet impingement erosion incubation period of metallic surfaces

Droplet impingement of metallic surfaces at high impact velocities results, after some time, in erosion of the surface due to fatigue. By extending our previously published analytical model to enable the use of experimental fatigue data (S‐N curves), here, for the first time, a wide range of experimental liquid droplet erosion incubation period test states for both ferrous (stainless steel AISI 316) and nonferrous (aluminium 6061‐T6) engineering metals have been investigated. To achieve this, the developed model includes additional surface hardening and a residual compressive stress state at the surface due to a water drop peening effect. As such, the interrelation of the physical and mechanical properties that follows from the model has been used to identify how changes in selected metal properties might enhance droplet impingement erosion incubation life. Model predictions for both metals, using fatigue data from S‐N curves from different literature sources, showed for the droplet impact velocity range of 140 to 400 m/s an excellent agreement with results from a multiregression equation as determined from an ASTM interlaboratory test program.     

Impact of <Emphasis Type="Italic">in vivo</Emphasis> glycation of LDL on platelet aggregation and monocyte chemotaxis in diabetic <Emphasis Type="Italic">Psammomys obesus</Emphasis>

Psammomys obesus (sand rat) is an appropriate model to highlight the development of hyperinsulinemia, insulin resistance, obesity, and diabetes. This animal species, with genetically predetermined diabetes, acquires non-insulin dependent diabetes mellitus when exposed to energy-rich diets. In the present study, we explored the possibility that glycation of LDL may occur in diabetes-prone P. obesus and affect platelet and macrophage functions. The glycation of LDL, isolated from diabetic animals, was significantly (P<0.05) higher (40%) than that of control animals. The incubation of platelets with glycated LDL enhanced the reactivity of platelets by 32–44% depending on the aggregating agents (thrombin, collagen, ADP). Furthermore, LDL derived from diabetic rats were chemotactic for normal monocytes and stimulated the incorporation of [¹⁴C]oleate into cellular cholesteryl esters. The enhancement of platelet aggregation and cholesterol esterification in monocytes may contribute toward the accelerated development of atherosclerotic cardiovascular disease in diabetic P. obesus animals. This study also illustrates the relevance of studying atherosclerosis in the P. obesus animal model, as it shows an increased tendency to develop dietinduced diabetes, which is associated with cardiovascular disorders.     

Experimental investigation of leaky lamb modes by an optically induced grating

By removing the symmetry of a free plate configuration, fluid loading significantly modifies the nature of acoustic waves travelling along a plate, and it even gives existence to new acoustic modes. We present theoretical predictions for the existence, dispersive behavior, and spatial distribution of leaky Lamb waves in a fluid-loaded film. Although Lamb modes are often investigated by studying the radiated fluid waves resulting from their leakage, here their properties are assessed by detecting the wave displacements directly using laser beam deflection. By using crossed laser beam excitation, the detection and analysis of the different modes is done at a fixed wavelength, allowing one to verify the existence, the velocity, and the damping of each predicted mode in a simple and unambiguous way. Our theoretical predictions for the nature of the modes in a water-loaded Plexiglas film, including parts of looping modes, are experimentally confirmed.     

Robust Single-Walled Carbon Nanotube-Infiltrated Carbon Fiber Electrodes for Structural Supercapacitors: from Reductive Dissolution to High Performance Devices

Multifunctional electrodes for structural supercapacitors are prepared by vacuum infiltration of single-walled carbon nanotubes (SWCNTs) into woven carbon fibers (CFs); the use of reductive charging chemistry to form nanotubide solutions ensured a high degree of individualization. The route is highly versatile, as shown by comparing four different commercial nanotube feedstocks. In film form, the pure nanotubide networks (“buckypapers”) are highly conductive (up to 2000 S cm⁻¹) with high surface area (>1000 m² g⁻¹) and great electrochemical performance (capacitance of 101 F g⁻¹, energy density of 27.5 Wh kg⁻¹ and power density of 135 kW kg⁻¹). Uniformly integrating these SWCNT networks throughout the CF fabrics significantly increased electrical conductivity (up to 318 S cm⁻¹), surface area (up to 196 m² g⁻¹), and in-plane shear properties, all simultaneously. The CNT-infiltrated CFs electrodes exhibited intrinsically high specific energy (2.6–4.2 Wh kg⁻¹) and power (6.0–8.7 kW kg⁻¹) densities in pure 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM TFSI) electrolyte. Multifunctional structural supercapacitors based on CNT-coated CFs offer a substantial increase in capacitive performance while maintaining the tensile mechanical properties of the as-received CF-based composite. This non-damaging approach to modify CFs with highly graphitic, high surface area nanocarbons provides a new route to structural energy storage systems.