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Tracking and Erosion Resistance of LSR and HTV Silicon Rubber Samples under Acid Rain Conditions
No full textAssessment of the material degradation in laboratory similar to field conditions is still a challenge. In the present work an attempt is made to study the effect of environment conditions in service life of polymeric insulators on tracking and erosion resistance. Evaluation of tracking and erosion resistance of Silicone Rubber insulating samples of high temperature vulcanized (HTV) rubber and liquid silicone rubber (LSR) are carried out under AC and positive polarity DC voltage. The samples are treated under normal contaminants as per IEC 60587 and acidic contaminant solution simulating acid rain. The conditions of pollution/contamination severity level are taken into consideration by maintaining the conductivity approximately 2.5 mS/cm for both solution to observe the effect of acidity alone on the samples, the acidity level is varied to understand the material behavior under acidic case with AC and DC stress application. A new experimental arrangement is set up based on IEC 60587 and ASTM D-2303 standards. The constant voltage method is employed to find the relative tracking performance of silicone rubber samples for different chemical composition. Physico-chemical analysis involving SEM, EDAX and FTIR is carried out on treated samples to understand the surface morphology and chemical changes. A comparative analysis is carried out for the acid rain solution and the standard solution of NH4Cl. Further leakage current performance and analysis is carried under both AC and DC stress
Sustainable bio-energy potential of perennial energy grass from reclaimed coalmine spoil (marginal sites) of India
No full textUsage of marginal lands to grow perennial grass for biomass feedstocks is a promising option to meet the bioenergy demand in India. In this context, the present work investigated the potential utility of two perennial grass species Cenchnis ciliaris (L) and Pennisetum pedicellatum (Tan.) to be a new promising energy source for bioenergy. This study entails a detailed characterization of biomass feedstocks using proximate and ultimate analysis, and lignocellulosic fractions and thermogravimetric behaviour using TG-FTIR and Py-GCIMS spectrophotometry to evaluate their potential as an alternate green fuel to fossil fuels by measuring their thermochemical conversion functioning. Property analysis of perennial grass species showed a significant difference in moisture content (7.2-8.5%), volatile matters (80.5-82.4%), fixed carbon (11.3-18.9%), HHV (15-17.8 Mj/kg) and LHV (14.3-16.5 Mj/kg), which is very promising for bioenergy generation. Lignocellulosic fractions of biomass feedstocks are comparable to the previous studied biomass species including switchgrass and elephant grass. The individual decomposition experiments indicated that biomass feedstocks possess higher thermochemical reactivity and shorter devolatilization time. According to Py-GC/MS study, carbonyl compounds including aldehyde and ketones are the major volatile products, in addition to furans, benzenes, phenols, acids, and others. The TGR1R results showed that main gaseous products evolved during devolatilization are CO, CO2, CH4, and H2O. All of the results and findings would help in characterizing the biomass as potential bioenergy feedstocks compatible with other biomass currently in use as supplementary fuel for power generation. (C) 2018 Elsevier Ltd. All rights reserved
A Multiple-Domain Matrix Support to Capture Rationale for Engineering Design Changes
No full textDesign changes are necessary to sustain the product against competition. Due to technical, social, and financial constraints, an organization can only implement a few of many change alternatives. Hence, a wise selection of a change alternative is fundamentally influential for the growth of the organization. Organizations lack knowledge bases to effectively capture rationale for a design change; i.e., identifying the potential effects a design change. In this paper, (1) we propose a knowledge base called multiple-domain matrix that comprises the relationships among different parameters that are building blocks of a product and its manufacturing system. (2) Using the indirect change propagation method, we capture these relationships to identify the potential effects of a design change. (3) We propose a cost-based metric called change propagation impact (CPI) to quantify the effects that are captured from the multiple-domain matrix. These individual pieces of work are integrated into a web-based tool called Vatram. The tool is deployed in a design environment to evaluate its usefulness and usability
Problems on matchings and independent sets of a graph
No full textLet G be a finite simple graph. For X subset of V(G), the difference of X, d(X) := vertical bar X vertical bar vertical bar N(X)vertical bar where N(X) is the neighborhood of X and max {d(X) : X subset of V(G)} is called the critical difference of G. X is called a critical set if d(X) equals the critical difference and ker(G) is the intersection of all critical sets. diadem(G) is the union of all critical independent sets. An independent set S is an inclusion minimal set with d(S) > 0 if no proper subset of S has positive difference. A graph G is called a Konig-Egervdry graph if the sum of its independence number alpha(G) and matching number mu(G) equals vertical bar V(G)vertical bar. In this paper, we prove a conjecture which states that for any graph the number of inclusion minimal independent set S with d(S) > 0 is at least the critical difference of the graph. We also give a new short proof of the inequality vertical bar ker(G)vertical bar + vertical bar diadem(G)vertical bar <= 2 alpha(G). A characterization of unicyclic non-Konig-Egervary graphs is also presented and a conjecture which states that for such a graph G, the critical difference equals alpha(G) mu(G), is proved. We also make an observation about ker(G) using Edmonds-Gallai Structure Theorem as a concluding remark. (C) 2018 Elsevier B.V. All rights reserved
Preparation of a chiral Pt-12 tetrahedral cage and its use in catalytic Michael addition reaction
No full textThe reaction of chiral cis-(1S,2S)-dch] Pt(NO3)(2) (M) where (1S,2S)-dch = (1S,2S)-1,2-diaminocyclohexane] with a hexadentate ligand (L) in 3 : 1 stoichiometric ratio yielded a 12+4] self-assembled chiral M12L4 molecular tetrahedron (T). The cage T features an internal 3D nanocavity with large open `windows', enabling it to catalyze Michael addition reactions of a series of nitrostyrene derivatives with indole in a 9 : 1 water : methanol mixture
Accretion flow dynamics during 1999 outburst of XTE J1859+226-modeling of broadband spectra and constraining the sourcemass
No full textWe examine the dynamical behavior of accretion flow around XTE J1859+226 during the 1999 outburst by analyzing the entire outburst data (similar to 166 days) from RXTE Satellite. Towards this, we study the hysteresis behavior in the hardness intensity diagram (HID) based on the broadband (3-150 keV) spectral modeling, spectral signature of jet ejection and the evolution of Quasi-periodic Oscillation (QPO) frequencies using the two-component advective flow model around a black hole. We compute the flow parameters, namely Keplerian accretion rate (<(m)over dot>(d)), sub-Keplerian accretion rate (<(m)over dot>(h)), shock location (r(s)) and black hole mass (M-bh) from the spectral modeling and study their evolution along the q-diagram. Subsequently, the kinetic jet power is computed as L-jet(obs) similar to 3-6 x 10(37) erg s(-1) during one of the observed radio flares which indicates that jet power corresponds to 8-16% mass outflow rate from the disc. This estimate of mass outflow rate is in close agreement with the change in total accretion rate (similar to 14%) required for spectral modeling before and during the flare. Finally, we provide a mass estimate of the source XTE J1859+226 based on the spectral modeling that lies in the range of 5.2-7.9 M-circle dot with 90% confidence
Anisotropic drop spreading on superhydrophobic grates during drop impact
No full textWe study the influence of geometric anisotropy of micro-grate structures on the spreading dynamics of water drops after impact. It is found that the maximal spreading diameter along the parallel direction to grates becomes larger than that along the transverse direction beyond a certain Weber number, while the extent of such an asymmetric spreading increases with the structural pitch of grates and Weber number. By employing grates covered with nanostructures, we exclude the possible influences coming from the Cassie-to-Wenzel transition and the circumferential contact angle variation on the spreading diameter. Then, based on a simplified energy balance model incorporating slip length, we propose that slip length selectively enhances the spreading diameter along the parallel direction, being responsible for the asymmetric drop spreading. We believe that our work will help better understand the role of microstructures in controlling the drop dynamics during impact, which has relevance to various engineering applications
Humidity Sensing Properties of Coexfoliated Heterogeneous WS2/WSe2 Nanohybrids
No full textTwo-dimensional-layered Van der Waals nanostructures and their hybrids have been in focus since the discovery of graphene. Transition metal dichalcogenides are an important segment of materials of this class which is analogous to graphene and can be exfoliated to mono and few layers form. Excellent interlayer coupling among these nanomaterials may result in fascinating synergistic properties. In this work, a simple liquid-phase coexfoliation technique was utilized to exfoliate WS2 and WSe2 simultaneously by an optimized mixed solvent strategy. The assynthesized nanohybrids were characterized by using different material characterization techniques. The coexfoliated nanomaterial has shown excellent humidity sensing properties including high reproducibility, stability, and low hysteresis. The response from our humidity sensor varies between 15.4 (at 40% RH) to 57 times (at 80% RH), compared to the reference value of the air (at similar to 25% RH). The response and recovery times were observed to be 40 and 65 s, respectively, for 60% RH. The performance of coexfoliated sensing layer was compared with individual WS2, and WSe2 nanosheets and nanocomposite prepared by exfoliation separately. Better performance of sensors utilizing coexfoliated nanosheets has been attributed to synergistic interfacial effects and high proton conductivity. A mechanism based on heterogeneous WS2/WSe2 nanohybrids has been proposed where the interfaces help in creating favorable sites for water adsorption and desorption apart from the sulfur vacancies in the individual WS2 or WSe2. This has been attributed to modulation of surface barrier potential through interfacial electron transfer. We believe such sensing mechanism can help in the development of a new generation highly sensitive humidity sensor
Simple Modules for High Efficiency Conversion of Standard Ytterbium doped Fiber Lasers into Octave Spanning Continuous Wave Supercontinuum Sources
No full textWe have demonstrated a similar to 34 W continuous wave supercontinuum using the standard telecom fiber (SMF 28e). The supercontinuum spans over a bandwidth of similar to 1000 nm (>1 octave) from 880nm to 1900 nm with a substantial power spectral density of >1mW/nm from 880-1350 nm and similar to 50-100mW/nm in 1350-1900 nm. The distributed feedback Raman laser architecture was used for pumping the supercontinuum which ensured high efficiency Raman conversions and helped in achieving a very high efficiency of similar to 44% for supercontinuum generation. Using this architecture, Yb laser operating at any wavelength can be used for generating the supercontinuum and this was demonstrated by using two different Yb lasers operating at 1117nm and 1085 nm to pump the supercontinuum
Phenology of Ficus spp. in a tropical dry forest, Mudumalai, south India
No full textThe phenology of figs (Ficus spp. Moraceae) is being monitored in the dry forests of Mudumalai, southern India and individuals belonging to the genus are marked with unique tag numbers and their vegetative and reproductive phenologies have been monitored since August 2000 on a monthly basis. The influence of abiotic factors on fig phenology and the differences between fig and non-fig phenologies are being examined. The seasonality of different phenophases of fig phenology is also being examined. The maximum intensity of leaf flush occurred in drier months. Fig and non-fig species showed significant differences with expansion and senescence phenophases of leafing. Flowering also occurred in drier months. There were significant differences between fig and non-fig species with reproductive phenophases. As with non-fig species, leafing was influenced by maximum temperatures. Both vegetative and reproductive phenophases were significantly seasonal