Self-mode-locking effects in heavily doped single-clad Tm3+-doped silica fibre lasers

Self-mode-locking in single-clad Tm-doped silica fibre lasers operating at 1.92?µm is reported with 100% modulated mode-locked pulses observed for longer fibre lengths up to 6?m. The self-mode-locking was accompanied by self Q-switching. A mode-locked pulse duration of 191?ps has been measured using an autocorrelator based on a two-photon absorption detector for operation at 2?µm assembled for the purpose of this experiment. The experimental pulse train characteristics are found to be consistent with mode-locking theoretical analysis. The origin and properties of self-mode-locking in heavily Tm-doped fibre lasers are discussed.     

Integration and dynamic inversion of population balance equations with size-dependent growth rate

Two novel solution schemes for integration and dynamic inversion of a class of population balance equations with size-dependent growth rate are contributed in this article. The proposed methods are developed for population balance systems that, in addition to an advective and a birth rate term, include an external variable which may be fixed (referring to the integration problem), or is to be computed for some prespecified evolution of the population system (referring to the dynamic inversion problem). A unique diffeomorphism for the independent time and internal (property) coordinates is introduced, which transforms the original nonlinear partial differential equation into a linear one with straight lines as equation characteristics. The evolution of the density function in the time and internal property coordinates is then computed by transporting the initial and boundary density functions in the transformed domain. For the integration of the temporal behavior of the boundary density function, a generalization of the standard method of moments is introduced, resulting in a closed integro-differential structure driven by convolution and correlation integrals. While the correlation integrals refer to the given initial density function and, hence, can be a priori computed, the convolution integrals involve the boundary density function and have to be integrated a posteriori online. The solution of the dynamic inversion problem, on the other hand, turns out to become simpler, as it converts to an algebraic equation after pre-computation of the correlation/convolution integrals for the given initial and boundary density function. In a next step, we introduce the concept of internal or eigenmoments which is useful for the representation of the original physical moments in terms of an infinite series. The dynamics of eigenmoments exhibits a closed ODE structure, which we refer to as the internal model. From the perspective of the systems theory this turns out to be an infinite dimensional flat system. Hence, in addition to providing a highly simple structure – basically, a chain of integrators – for the integration of the moments and the density function, the internal model allows for a direct solution of the dynamic inversion problem due to its flatness property. However, the ease and elegance of the method, in general, come at the price of an approximation of the infinite dimensional problem by a finite one. The usability of both proposed solution methods is illustrated on a batch crystallization process with size-dependent growth rate kinetics. The proposed methods are compared in terms of efficiency and accuracy with a state-of-the-art high-resolution finite volume scheme using a numerical example.     

A parallel circuit differential class-E power amplifier using series capacitance

Class-E amplifiers are attractive for wireless handsets because of their high efficiency and simple implementation. However, it requires inductors in its output matching network that are inherently low Q components affecting efficiency and may require significantly large area in fully integrated implementation. In this paper a novel approach of implementing parallel circuit differential class-E amplifier is presented. Instead of using an inductor parallel to the transistor drain of each amplifier, a single capacitor at the single ended side of the balun provides the parallel inductance effect to the switching transistors. As a result, number of inductors required for circuit implementation is reduced which means reduced losses, less area and better tuning of reactance can be achieved. A test circuit is implemented in 0.13 μm CMOS process. Measurement results verify the validity of the concept. The Power Amplifier achieves 22 dBm output power at 2.4 GHz from a 2.5 V with an overall Power Added Efficiency of 38 %.     

Effect of counterface balls on the friction layer of Ni3Al matrix composites with 1.5 wt% graphene nanoplatelets

Research on the friction layer is needed to minimize friction- and wear-related mechanical failures in moving mechanical assemblies. Dry sliding tribological tests of Ni₃Al matrix composites (NMCs) with 1.5 wt% graphene nanoplatelets (GNPs) sliding against different counterface balls are undertaken at the condition of 10 N–0.234 m s^?1 in this study. When sliding against GCr15 steel, a uniform and thick friction layer is formed, resulting in a lower friction coefficient (0.29–0.31) and wear rate (2.0–3.1 × 10^?5 mm³ N^?1 m^?1). While sliding against Al₂O₃ and Si₃N₄, the formation and stability of the friction layers are restricted in the severe wear regime, and the NMCs exhibit higher friction coefficients and wear rates. Therefore, various counterface balls have a great effect on the stability and thickness of the friction layer, thus affecting the tribology performance of NMCs. The result also shows that GNPs exhibit enrichment and self-organized microstructures in the friction layer. In addition, the friction layer is also found to be divided into two layers, protecting the subsurface from further damage and reducing shear.     

Laser-induced efficient reduction of Cr(VI) catalyzed by ZnO nanoparticles

The present study demonstrates the complete removal of Cr(VI) in aqueous suspensions of zinc oxide nanoparticles using a novel laser-induced photocatalytic process without the use of any additive. The study showed that ～95% Cr(VI) was removed within short time (60 min) of laser exposure in the presence of ZnO. However, the removal of chromium using conventional setup under identical conditions was found to be negligible. Effect of critical parameters, such as laser energy, catalyst concentration, chromium concentration, and added electron donor and acceptor on the photocatalytic reduction process was also investigated. The data regarding temporal behavior of metal removal was fitted to first-order kinetic and reaction rate was computed.     

Microscopic characterization of petiole anatomy of Asteraceous taxa of Western Himalaya-Pakistan

Petiole anatomy of 15 species of family Asteraceae was examined which aimed to investigate petiolar anatomical structures for species level identification. Shandon Microtome was used for petiole histological preparations. Both qualitative and quantitative features were studied under microscope which showed significant variation in petiole, collenchyma, parenchyma shape/size, vascular bundles arrangement/size, and vessel elements quantity. Artemisia japonica Thunb., Cirsium vulgare (Savi) Ten., Myriactis nepalensis Less., Seriphidium brevifolium Ling & Y.R.Ling, Taraxacum officinale (L.) Weber ex F.H.Wigg., and Xanthium strumarium L. showed winged petioles. Maximum length and width of upper and lower epidermis was found in Tagetes erecta L. which is 23.05 ± 0.89 μm, 24.9 ± 1.257 μm length and 21.75 ± 1.38067 μm, 22.75 ± 0.467 μm width, respectively. Petioles of Parthenium hysterophorus L. was longest one with 9.85 ± 10.45 μm while A. japonica Thunb. showed highest number of vessel elements. Maximum size of vascular bundles was found in T. erecta L. with 5.05 ± 14.25 μm. Artemisia annua L., C. vulgare (Savi) Ten, Cyanthillium cinereum (L.) H.Rob., Helianthus annus L., M. nepalensis Less., P. hysterophorus L., Senecio chrysanthemoides DC. have trichomes while Tussilago farfara L. has highest number of vascular bundles. All species have angular collenchyma type except M. nepalensis Less., P. hysterophorus L., S. brevifolium Ling & Y.R.Ling, Tagetes minuta L., T. officinale L., S. chrysanthemoides DC., and T. farfara L. Cluster analysis implemented that distinct plant species in cluster. Petiolar anatomical structures and taxonomic key will helpful for distinguishing Asteraceous taxa at genus and species level. This taxonomic significant investigation will also provide baseline to taxonomists for other Asteraceae studies and phylogenetic research.     

Dependence of magnetoelectric properties on the magnetostrictive content in 0–3 composites

The magnetoelectric response in composites of barium titanate (BTO) and cobalt ferrite (CFO) has been determined by measuring the magnetoelectric susceptibility coefficient. This was done by two different methods: magnetocapacitance measurements and magnetoelectric voltage measurement using a lock-in technique. These composites were prepared by the sol–gel method. Four different compositions with different molar ratios of the magnetostrictive phase (CFO) embedded in a piezoelectric matrix of BTO were studied to investigate the effect of the magnetostrictive content and the number density of interfaces on the magnetoelectric response. It was found from both techniques that the magnetoelectric coupling effect increases with the increase of applied field and it had a non-linear dependence on the percentage of magnetostrictive content in the composites.     

Vehicle Pollution Monitoring,Control and Challan System Using MQ2 Sensor Based on Internet of Things

Wireless Personal Communications - In the automobile sector, the new advancements in technology help the vendors in developing smart vehicles. These smart vehicles are designed to provide all sort...     

Pollen micromorphological analysis of tribe Acacieae (Mimosaceae) with LM and SEM techniques

The morphology of pollen grains of the 06 species of tribe Acacieae (Mimosaceae) belonging to one genus were investigated using scanning electron microscopic (SEM) and light microscopic (LM) approach. Lactic acid acetolysis method was used for (LM) while non‐acetolysis for (SEM). The species were examined for the both qualitative and quantitative palynological features. Qualitatively the pollen was studied for the shape, exine sculpturing, pollen shape, and pollen type. Oblate spheroidal shape of pollen was observed in Accacia modesta. Subprolate shape in Accaca nilotica. In Accacia farnesiana, prolate pollen was examined while prolate spheroidal in Acacia tortilis and spheroidal pollen grains were studied in Acacia catechu, respectively. Pollen exine sculpturing of the studied tribe possesses novel variation. Foveolate, reticulate, foveolate‐psilate, faint reticulate, fossulate, perforate, and scrabate exine sculpturing were noticed. Colpi were absent in all species. Excessive variation was observed in both qualitative and quantitative character of pollen. SPSS software was use for the quantitative measurement of the pollen grains. The current study will be helpful for the identification of the problematic species and phylogenetic studies of family Mimosaceae.