Experimental validation of a thermal modelling method dedicated to multichip power modules in operating conditions

In this paper, we present an implementation of a thermal modelling method applied to a multichip module used as a power converter. Analytical functions of thermal impedances, with original formulations for the mutuals are defined. They are derived from 3D thermal simulations and experimental validations with direct chips temperature measurements. Finally, simulations are performed in order to improve the capability of our model to assess, with fast computation, the thermal constraints applied on the multichip module in a real operating condition.     

Estimation of SiC JFET temperature during short-circuit operations

This paper presents results showing the robustness of different SiC JFET transistors from SiCED in current limitation regime or short-circuit operation. Crystal temperature during failure was estimated after different electrical characterizations and using appropriate models of saturation current which is used as a thermal indicator. This work shows the exceptional robustness of SiC JFET transistors in current limitation mode compared to Si devices (MOSFETS and IGBTs).     

Oxidative Aromatization of 1,3,5-trisubstituted 2-pyrazolines Using Oxalic Acid/Sodium Nitrite System

Oxidative aromatization of 1,3,5-trisubstituted 2-pyrazolines by in-situ generation of NO⁺ from oxalic acid/sodium nitrite system has been described. The main advantages of this procedure are the use of an inexpensive and readily available catalyst, facile work-up, and improved yields in aqueous ethanol.     

A geometrically nonlinear size-dependent hypothesis for porous functionally graded micro-plate

The static bending behavior of porous functionally graded (PFG) micro-plate under the geometrically nonlinear analysis is studied in this article. A small-scale nonlinear solution is established using the Von-Kármán hypothesis and the modified couple stress theory (MCST). To obtain the deflection of the plate, the Reddy higher-order plate theory coupled with isogeometric analysis (IGA) is utilized. The distribution of porosities is assumed to be even and uneven across the plate’s thickness and the effective material properties of porous functionally graded micro-plate are calculated using the refined rule-of-mixture hypothesis. The influence of power index, porosity parameter and material length scale parameter on the nonlinear behaviors of static bending of porous FGM micro-plates are also investigated using several numerical examples.

     

Highly efficient electrocatalysts fabricated via electrophoretic deposition for alcohol oxidation,oxygen reduction,hydrogen evolution,and oxygen evolution reactions

Electrophoretic deposition (EPD) is a versatile technique that has drawn attention due to its ease of use and performance in depositing high-quality layers at room temperature. This technique principle is based on the deposition of charged particles from a stable colloidal suspension on a conductive substrate using either a direct or alternating current. Using relatively simple and low-cost equipment, the EPD technique enables the deposition of layers with controlled microstructures at nanoscale. The EPD technique has been particularly successful in the fabrication of the electrocatalyst layers for low-temperature fuel cells, which are anchored on the top of the fuel cell electrodes. In comparison with other electrocatalyst layer deposition techniques such as drop-casting, the EPD technique offers clear advantages for the control of the thickness and packing density of the electrocatalyst layers. Owing to the dense packing density, electrocatalyst layers deposited by EPD could achieve enhanced conductivity and efficiency. The present review aims at comprehensively evaluating the recently published results on the electrocatalyst layers fabricated by EPD and applied in oxygen reduction reactions, alcohol electro-oxidation reactions, hydrogen evolution reactions, and oxygen evolution reactions.     

AK-GWO: a novel hybrid optimization method for accurate optimum hierarchical stiffened shells

Engineering with Computers - An attempt has been made to propose a novel prediction model based on the Gaussian process regression (GPR) approach. The proposed GPR was used to predict blast-induced...     

Influence of nanoclay on urea–glyoxalated lignin–formaldehyde resins for wood adhesive

In this research, the influence of nanoclay on urea–glyoxalated lignin–formaldehyde (GLUF) resin properties has been investigated. To prepare the GLUF resin, glyoxalated soda baggase lignin (15 wt%) was added as an alternative for the second urea during the UF resin synthesis. The prepared GLUF resin was mixed with the 0.5%, 1%, and 1.5% nanoclay by mechanically stirring for 5 min at room temperature. The physicochemical properties of the prepared resins were measured according to standard methods. Then the resins were used in particleboard production and the physical and mechanical properties of the manufactured panels were determined. Finally, from the results obtained, the best prepared resin was selected and its properties were analyzed by differential scanning calorimetry (DSC), Fourier transform infrared spectrometry (FTIR), and X-ray diffractometry (XRD). Generally the results indicated that the addition of sodium-montmorillonite (NaMMT) up to 1.5% appears to improve the performance of GLUF resins in particleboards. The results also showed that nanoclays improved mechanical strength (modulus of elasticity (MOE), Modulus of Rupture (MOR), and internal bond (IB) strength) of the panels bonded with GLUF resins. The panels containing GLUF resin and nanoclay yielded lower formaldehyde emission as well as water absorption content than those made from the neat GLUF resins. XRD characterization indicated that NaMMT only intercalated when mixed with GLUF resin. Based on DSC results, the addition of NaMMT could accelerate the curing of GLUF resins. The enthalpy of the cure reaction (ΔH) of GLUF resin containing NaMMT was increased compared with neat GLUF resin. Also the results of FTIR analysis indicated that addition of NaMMT change the GLUF resins structures.     

Influence of balancing of internal combustion engines on the operating conditions of hydrodynamic bearings

We studied the influence of balancing internal combustion engines on the performance of hydrodynamic plain bearings. A non-linear approach makes it possible to calculate the forces of pressure generated by the lubricant film. This approach is coupled with a dynamic calculation, which determines the inertia forces of the rod. The counterweight to balance the engine is applied to the heads of rods and not to the crankshaft. We chose three models of connecting rod (rod of an engine in series, rod with partial and rod with complete counterweight). To determine the lubricant pressure field in the bearing, the modified Reynolds equation was solved using the finite difference method, taking into account the boundary conditions of Reynolds. Since the bearing is subjected to a variable load, the mobility method was used to facilitate the resolution of the Reynolds equation. The proposed numerical simulation allowed us to analyze the influence of counterweight applied to the connecting rod head on the variation of the lubricant pressure field, the minimum film thickness, the axial flow and the friction torque in the big end bearing during the operating cycle.