Phase Transition and Electrical Properties in Cs2SeO4.Te(OH)6

Dielectric investigations in the temperature and frequency 300- 600 K and 0,1KHz–13MHz, respectively, show that cesium selenate tellurate Cs2SeO4.Te(OH)6 (CsSeTe) exhibits two phase transitions at 490 and 525 K. The a.c. complex impedance measurements performed on CsSeTe material show an important level of conductivity at high temperature, attributed to the motion of H+ proton. This behavior is in agreement with the presence of the super- protonic phase transition in CsSeTe compound at 525K. This assignment was confirmed by the analysis of the M"/M"max spectra. The temperature dependences of ε΄r and tanδ indicate that the anomaly at 490K is attributed to a ferroelectric-paraelectric phase transition. Thermal analysis at high temperature, DSC, DTA, TG,  Ms/z= 18 and Ms/z= 32 confirm the presence of the two transitions already cited, the temperature and the nature of the decomposition. Â

The influence of position in overlap joints of Mg and Al alloys on microstructure and hardness of laser welds

Structure and properties of laser beam welding zone of dissimilar materials, AZ31 magnesium alloy and A5754 Aluminum alloy, are investigated. The microstructure and quality of the Mg/Al weld were studied by metallography, microhardness and optical microscopy. Differences in physical and mechanical properties of both materials, magnesium and aluminum, affect weldability and resistance of this combination, and lead to the formation of intermetallic compounds in the welded metal

Numerical Investigation of the Vortex Breaker for A Dynamic Separator using Computational Fluid Dynamics

The separation efficiency and pressure drop of the dynamic separator of cement particles can be affected by many factors, like structural type, geometric parameters, and operating characteristics. In this paper, CFD modeling is applied to investigate the fluid flow behavior and the efficiency of the industrial dynamic separator with different heights of the inner cone called the vortex breaker. Simulations are based on the RSM and the DPM models. A CFD comparison of the original design and new designs has been performed. The simulation results showed that the fluid flow inside the industrial air separator is greatly dependent on the height of the vortex breaker. Interesting phenomena were observed by the numerical simulations and the results revealed that an increase in the height of the vortex breaker up to three-quarters of the magnitude of the fine powder outlet duct can improve the performances of particle separation not only by reducing 29% the cut size, and by 40% the bypassing of fine particles but also by increasing 30% the separation sharpness while keeping the pressure drop substantially unchanged

CFD Study of the Effect of Geometrical Shape of Separation Blades on the Rotor Performance of an Annular Centrifugal Extractor (ACE)

Annular centrifugal extractors have a great potential in the multiphase extraction of pharmaceutical, nuclear, and many other processes. Although the widespread use of this device, the design procedures are still unavailable because of the complexity of the fluid mechanics in the rotor region called the separation zone. From a structural point of view, this region has a complicated conception due to the different internals. This study presents a three-dimensional numerical simulation of the flow field inside the rotor region of an annular centrifugal extractor ACE. The industrial CFD code (Fluent) was used to model the highly swirling fluid flow in the settling zone with various geometries of separation blades (straight blades and curved blades). Numerical predictions and experimental results were compared in order to validate the proposed models. The velocity field with the k-ε model shows a good agreement with the experimental data available in the literature. The Volume of Fluid (VOF) method was employed to simulate the physics of the interface of air/water free surface. A comparison between the flow field and the performances of the ACE model design with vertical straight blades and with vertical curved blades was further investigated to study the effect of the geometric shape of the separation blades on the parameters of liquid holdup volume, the interface radius and the pressure drop. It was found that the geometry of the separating blades has a significant impact on the pressure drop, liquid hold-up volume and interface radius and general flow in the extractor-settling zone. The predicted pressure drop proved that the geometry of the ACE rotor with curved blades leads to a lower values of pressure drop

Primary Plasmacytoma of The Testis with no Evidence of Multiple Myeloma: a New Case Report and Literature Review

Plasmacytomas of the testis are extremely rare tumours, especially when occurring in the absence of a previous or concurrent diagnosis of multiple myeloma. We report a new case of solitary testicular plasmacytoma, with immunohistochemical studies showing monoclonal cytoplasmic production of IgG lambda light chains, in a 51-year-old man who had no evidence of multiple myeloma 3 years after the orchiectomy.Key Words: Testis, plasmacytoma, multiple myelom

Effect of the Number of Injectors on the Mixing Process in a Rapidly Mixed Type Tubular Flame Burner

Three-dimensional simulations are performed to study the non-reactive mixing process in a rapidly mixed type tubular flame burner (RTFB). The current work examines the effect of the number of injectors (N= 2, 4 and 6) on the mixing process by focusing on three criterions (Flow structure, local swirl intensity and mixing layer thickness). The Discrete Phase Model (DPM) is used to track the particle trajectories. Validation of the numerical results is carried out by comparing the predicted particle trajectories, central recirculation zone (CRZ) and tangential velocity results to the experimental data. It is concluded that the model offers a satisfactory prediction of the flow field in a RTFB. Numerical results show that, for the same geometrical swirl number (Sw) and the same Reynolds number (ReT), the increasing of the number of injectors enhances the mixing process by generating a larger reverse flow and reducing the mixing layer thickness. It is also concluded that the local swirl intensity along of the RTFB can be correlated in terms of geometric swirl number and number of injectors

Shielding Gas Coaxial Jet Pipes Numerical Study of a Vertical Laser Welding Process of AZ91 Magnesium Alloy

The laser welding of magnesium alloys, largely used in many fabrication applications, has gained considerable interest especially in aerospace, electronics, automotive industry etc. Unfortunately, this process is associated to an undesired phenomenon which is “oxidation”. For this reason, a good shielding system of the welding zone is of major importance. This paper presents a numerical study using computational fluid dynamics (CFD) of a laser welding process employing a moving volumetric heat source. Starting with the turbulence model validity, a parametric study of this welding process in a vertical position aiming to optimize the design of protection gas device, the gas jet inclination, the appropriate welding direction and the gas type is, then, proposed. The optimum parametric combination ensuring the largest gas coverage area is the one where the shielding gas is Argon, supplied by the coaxial nozzles at a downward inclination angle with respect to the laser beam axis, and a downward welding direction

The Tnt1 Retrotransposon Escapes Silencing in Tobacco, Its Natural Host

Retrotransposons' high capacity for mutagenesis is a threat that genomes need to control tightly. Transcriptional gene silencing is a general and highly effective control of retrotransposon expression. Yet, some retrotransposons manage to transpose and proliferate in plant genomes, suggesting that, as shown for plant viruses, retrotransposons can escape silencing. However no evidence of retrotransposon silencing escape has been reported. Here we analyze the silencing control of the tobacco Tnt1 retrotransposon and report that even though constructs driven by the Tnt1 promoter become silenced when stably integrated in tobacco, the endogenous Tnt1 elements remain active. Silencing of Tnt1-containing transgenes correlates with high DNA methylation and the inability to incorporate H2A.Z into their promoters, whereas the endogenous Tnt1 elements remain partially methylated at asymmetrical positions and incorporate H2A.Z upon induction. Our results show that the promoter of Tnt1 is a target of silencing in tobacco, but also that endogenous Tnt1 elements can escape this control and be expressed in their natural host