Radiation analysis and errors associated with the monopulse operation of a satellite direction finder

This work describes the radiation performance of a novel concept for direction and location finding, using stationary satellite beacons. The received signals are processed with a monopulse four-element array. The monopulse mode is generated using the phase excitation of the radiating elements. For accurate processing the radiation phase should correspond with the bearing angle around the boresight direction. Phase deviations, however, occur in this phase pattern owing to the discrete excitation of the elements. Therefore, detailed analyses are presented for this phase pattern, its attainable gain and the depolarization effects, in order to select the kind of array elements, and their spacings, which minimize the phase pattern deviations. The dipoles and the slots, as array elements, yield better phase performance, smaller size and simpler structures than horn radiators, at the expense of worse depolarization.     

Microbial-Catalyzed Biotransformation of Multifunctional Triterpenoids Derived from Phytonutrients

Microbial-catalyzed biotransformations have considerable potential for the generation of an enormous variety of structurally diversified organic compounds, especially natural products with complex structures like triterpenoids. They offer efficient and economical ways to produce semi-synthetic analogues and novel lead molecules. Microorganisms such as bacteria and fungi could catalyze chemo-, regio- and stereospecific hydroxylations of diverse triterpenoid substrates that are extremely difficult to produce by chemical routes. During recent years, considerable research has been performed on the microbial transformation of bioactive triterpenoids, in order to obtain biologically active molecules with diverse structures features. This article reviews the microbial modifications of tetranortriterpenoids, tetracyclic triterpenoids and pentacyclic triterpenoids.     

Conception d’une solution de sélection de passerelles Internet dans les réseaux ad hoc

In the past few years, Internet has raised increasing interest in various areas including research, education, and business. The number of people accessing the Internet at work or at home has increased considerably, just like the number of services offered (email, e-commerce, search engines, e-learning, e-government, etc.). Ad hoc networks were generally viewed as stand-alone networks, where communications are only supported between nodes in the network such as in military and rescue operations. The lack of connectivity to the wired infrastructure enables simple management and deployment, but limits the applicability of ad hoc networks to today’s scenarios, which require connectivity outside the ad hoc network and particularly to the Internet. However, to reach this goal, a number of problems need to be resolved because of the dynamic nature of such environment. In this article, we describe a new solution for dynamic gateway selection based on quality of service (QoS) criteria. The underlying architecture is based on a pro-active routing protocol.     

Structural,ferroelectric, magnetic and magnetoelectric properties of (1-x) Ba0.85Ca0.15Zr0.1Ti0.9O3 -x La0.67Sr0.33MnO3 lead-free magnetoelectric composites

The influence of an additional La_0.67Sr_0.33MnO₃ (LSMO) magnetic phase on the structural, ferromagnetic, ferroelectric, and magnetoelectric properties of Ba_0.85Ca_0.15Zr_0.1Ti_0.9O₃ (BCZT) ferroelectric phase was studied for composites of (1-x)BCZT -xLSMO (x = 0, 25, 50, 75 and 100%). The ferroelectric BCZT sample showed a perovskite single phase formation with a tetragonal crystal structure of the P4mm space group, and the magnetic phase of LSMO presented a rhombohedral crystal structure of R3c space group as shown by XRD. The composite sample with 25% LSMO exhibited large ferroelectric and piezoelectric properties with remnant, saturation polarization, and coercive electric field P_r ~7.74 μC/cm², P_s ~11.69 μC/cm² and E_C ~12.22 kV/cm with a piezoelectric coefficient d₃₃ ~ 231 pC/N. The magnetic characterization for the composites showed that the sample containing 75% of LSMO revealed the highest remnant, saturation magnetization, and coercive field of M_r ~1.358 emu/g, M_s ~19.17 emu/g, and H_C ~33.19 Oe, respectively. Moreover, it revealed the largest magnetoelectric coupling coefficient α_ME ~2.51 mV/cm.Oe with high coupling quality at a lower applied magnetic field. The results highlight the value of these composites as lead-free room temperature magnetoelectric sensors and actuators.     

Investigation of gear performance of MLNGPs as an additive on polyamide 6 spur gear

Molded plastic gears have long provided an alternative to metal gears in lightly loaded drives. They transmit power quietly and often without lubrication in numerous applications, furthermore decrease the quantity of parts and oppose chemicals in numerous applications. Previously, plastic gears were restricted to to 0.25 hp because of varieties in their properties and uncertainties about how they react to natural conditions such as moisture, temperature and chemical. Today, better molding controls combined with design practices that more accurately encompass environmental factors have boosted plastic gear drive capacity to 1.5 hp. Using reinforcement this is standout amongst the most practices to enhance the gear performance.

This study estimated the effects of multilayer graphene nanoplatelets (MLNGPs) as an additive on polyamide 6 (PA6) spur gear performance. These include strength, elastic modulus, thermal stability, dynamic mechanical analysis, moisture absorption, and wear characteristics.The nanocomposite gear was made by melt mixing method and injection moulded into thick flanges. The flanges were machined using CNC milling machine to produce spur gear. The wear experiments were performed at a running speed of 1400 rpm and at torques of 13 and 16 Nm with different concentration 0, 0.1, 0.3 and 0.5 wt% MLNGPs using test rig. The result showed that 0.3% of MLGNPs is the optimum concentration. Young's modulus increased up to 40%, Vickers microhardness value increased up to 25%, storage modulus E’ is increased up to 37% and glass transition temperature is increased up to 14%. On the other hand TGA result shows that the Tonest increased up to 7.5% and Td increased up to 2%, and wear decreased by 35% at 16 Nm and 54% at 13 Nm.     

Structural and optical properties of polycrystalline CdSexTe1−x (0 ≤ x ≤ 0.4) thin films

CdSe_xTe_1−x (0 ≤ x ≤ 0.4) ternary thin films have been deposited on quartz substrates at room temperature by a single source thermal evaporation. X-ray diffraction patterns and transmission electron microscope micrographs of these films showed that the films were of polycrystalline texture over the whole range studied and exhibit predominant cubic (zinc blende) structure with strong preferential orientation of the crystallites along (1 1 1) direction. Linear variation of the lattice constant with mole fraction x is observed obeying Vegard's law. The dependence of the optical constants, the refractive index n and extinction coefficient k, of the films on the mole fraction x was studied in the spectral range of 400-2500 nm. The normal dispersion of the refractive index of the films could be described using the Wemple-DiDomenco single-oscillator model. CdSe_xTe_1−x thin films of different composition have two direct and indirect transitions corresponding to energy gaps and . The variation in either or with x indicates that this system belongs to the amalgamation type. The variation follows a subquadratic dependence and the bowing parameters were found to be 0.36 and 0.48 eV for the direct, and indirect energy gaps, respectively. Direct linear variation of the ratio N/m^* with x is observed.