Structure and properties of some vegetable fibres

The stress-strain curves for pineapple leaf fibre have been analysed. Ultimate tensile strength (UTS), initial modulus (YM), average modulus (AM) and elongation of fibres have been calculated as functions of fibre diameter test length and test speed. UTS, YM, and elongation lie in the range of 362 to 748 MN m^–2, 25 to 36 GN m^–2, and 2.0 to 2.8%, respectively for fibres of diameters ranging from 45 to 205m. UTS Was found to decrease with increasing test lengths in the range 15 to 65 mm. Various mechanical parameters show marginal changes with change in speed of testing in the range of 1 to 50 mm min^–1. The above results are explained on the basis of structural variables of the fibre. Scanning electron microscope studies of the fibres reveal that the failure of the fibres is mainly due to large defect content of the fibre bo1h along the fibre and through the cross-section, The crack is always initiated by the defective cells and further aggravated by the weak bonding material between the cells.     

Magnetic Properties of Mn‐doped SnO2 Thin Films Prepared by the Sol–Gel Dip Coating Method for Dilute Magnetic Semiconductors

Manganese‐doped tin oxide (SnO₂:Mn) thin films were deposited on glass substrates by the sol–gel dip coating technique. The effect on structural, morphological, magnetic, electrical, and optical properties in the films with different Mn concentrations (0–5 mol%) were investigated. X‐ray diffraction patterns (XRD) showed the deterioration of crystallinity with increase in Mn‐doping concentration. Scanning electron microscopy (SEM) studies showed an inhibition of grain growth with an increase in Mn concentration. X ray photoelectron spectroscopy (XPS) revealed the presence of Sn⁴⁺ and Mn³⁺ in SnO₂: Mn films. SnO₂: Mn films show ferromagnetic and paramagnetic behavior. These SnO₂:Mn films acquire n‐type conductivity for 0–3 mol% (SnO₂ ‐ Sn_0.97Mn_0.03O_{2) ‐}doping concentration and p type for 5 mol% Mn‐doping concentration(Sn_0.95Mn_0.05O₂) in SnO₂ films. An average transmittance of > 75% (in UV‐Vis region) was observed for all the SnO₂:Mn films. Optical band gap energy of SnO₂: Mn films were found to vary in the range 3.55 to 3.71 eV with the increase in Mn‐doping concentration. Photoluminescence (PL) spectra of the films exhibited an increase in the emission intensity with increase in Mn‐doping concentration which may be due to structural defects or luminescent centers, such as nanocrystals and defects in the SnO₂. Such SnO₂:Mn films with structural, magnetic and optical properties can be used as dilute magnetic semiconductors.     

Hybrid atmospheric correction algorithms and evaluation on VNIR/SWIR Hyperion satellite data for soil organic carbon prediction

ABSTRACT

Visible near-infrared and shortwave infrared data acquired by spaceborne sensors contain atmospheric noise, along with target reflectance that may affect its end applications, e.g. geological, vegetation, soil surface studies, etc. Several atmospheric correction algorithms have been already developed to remove unwanted atmospheric components of a spectral signature of Earth targets obtained from airborne/spaceborne hyperspectral image. In spite of this, choosing of an appropriate atmospheric correction algorithm is an ongoing research. In this study, two hybrid atmospheric correction (HAC) algorithms incorporating a modified empirical line (EL_m) method were proposed. The first HAC model (named HAC_1) combines (i) a radiative transfer (RT) model based on the concepts of RT equations, which uses real-time in situ atmospheric and climatic data, and (ii) an EL_m technique. The second one (named HAC_2) combines (i) the well-known ATmospheric CORrection (ATCOR) model and (ii) an EL_m technique. Both HAC algorithms and their component single atmospheric correction algorithms (ATCOR, RT, and EL_m) were applied to radiance data acquired by Hyperion satellite sensor over study sites in Australia. The performances of both HAC algorithms were analysed in two ways. First, the Hyperion reflectances obtained by five atmospheric correction algorithms were analysed and compared using spectral metrics. Second, the performance of each atmospheric correction algorithm was analysed for prediction of soil organic carbon (SOC) using Hyperion reflectances obtained from atmospheric correction algorithms. The prediction model of SOC was built using partial least square regression model. The results show that (i) both the hybrid models produce a good spectrum with lower Spectral Angle Mapper and Spectral Information Divergence values and (ii) both hybrid algorithms provided better SOC prediction accuracy, in terms of coefficient of determination (R²), residual prediction deviation (RPD), and ratio of performance to interquartile (RPIQ), with R² ≥ 0.75, RPD ≥ 2, and RPIQ ≥ 2.58 than single algorithms. HAC algorithms, developed using EL_m technique, may be recommended for atmospheric correction of Hyperion radiance data, when archived Hyperion reflectance data have to be used for SOC prediction mapping.     

Drug-induced vasodilation in an in vitro and in vivo study: the effects of nicardipine, papaverine, and lidocaine on the rabbit carotid artery

Extreme arterial vasoconstriction (vasospasm) is a common problem encountered in microvascular surgery. An ideal pharmacologic tool able to counteract ischemia during microsurgery should be easy to apply and exert its action both locally and distally in the microcirculation of the flap. We have compared in vitro and in vivo vascular properties of nicardipine, papaverine, and lidocaine in the rabbit carotid artery. In vitro, rings from the rabbit carotid artery (n = 7) were bathed in Krebs-Ringers solution and stretched progressively to an optimal tension of 3.7 to 4.2 g. The specimens were contracted with norepinephrine (1 microM), and a cumulative dose response curve was established. In vivo, microvascular anastomoses were performed bilaterally in the rabbit carotid artery in 35 animals using 9-0 nylon suture and standard microsurgical techniques. During and after the anastomoses, nicardipine (0.1, 0.01 mg topical, or 0.1 mg/hour IV), papaverine (30 mg/cc topical), and lidocaine (2% with and without epinephrine) were applied (blinded) at the anastomotic site in five rabbits each. Heparinized sodium chloride was used as topical irrigation for control and to clean the anastomosis. Blood flow changes were monitored continuously with the transonic Doppler for 30 minutes after the procedure. The systemic blood pressure was also monitored in a group of pilot experiments. A documented decrease in blood flow was noted in all animals after the microvascular anastomosis. Nicardipine and papaverine evoked a concentration-dependent relaxation to precontracted rings to norepinephrine. Nicardipine was greater than papaverine in inducing relaxation. Lidocaine demonstrated a biphasic response with low concentrations potentiating contraction. Systemic nicardipine and papaverine significantly increased the blood flow in the rabbit carotid artery. Topical application of nicardipine and lidocaine did not significantly alter the blood flow; however, the application of nicardipine demonstrates a trend toward increased flow. Lidocaine with epinephrine significantly decreased the blood flow. No drug was found to alter the blood pressure of the animals. Our results demonstrate that nicardipine and papaverine seem to be pharmacologic tools able to increase the blood flow in anastomotic arteries. In contrast, the use of 2% lidocaine as a spasmolytic agent should be re-evaluated, since this substance may act as a partial agonist.     

Reduction of cresolase and catecholase activities in tubers of some Indian potato varieties by the application of potash fertilisers

Cresolase and catecholase activities were determined in tubers of four potato (Solanum tuberosum L) varieties (Kufri Chamatkar, Kufri Chandramukhi, Kufri Sindhuri and C-2703) fertilised with three levels (0, 120, 240 kg K₂O ha^?1) of either muriate or sulphate of potash. The enzyme activities were also determined separately in the peel and flesh tissues of the tubers of Kufri Chamatkar and C-2703. Differences were observed in the activities between varieties, with highest specific activities in the tubers of Kufri Chamatkar. Peels of both the varieties showed higher cresolase and catecholase activities than the flesh tissue. Application of potassic fertilisers caused a reduction in both the activities in the tuber, peel and flesh tissue. Greater reduction in activities was caused by application of muriate of potash than with the sulphate form.     

A lumped mass vibration model of a slender latticed cantilever

A relatively simple numerical iterative procedure for estimating the normal modes of flexural vibrations of a slender, multipanel latticed cantilever, tapered or straight, is developed. The cantilever is reduced to a N mass system and the influence coefficients are derived with due consideration to the shear flow through the diagonal bracings. Experimental and computer results on a model are compared.     

Mechanical behaviour of coir fibres under tensile load

Stress-strain curves of coir fibres have been determined. Mechanical properties including initial modulus, strength and percentage elongation of coir fibres have been evaluated as functions of retting treatment (during retting the coconut husks are soaked in saline water for a period of about six months to facilitate the extraction of fibres presumably due to a bacterial process), fibre diameter, gauge length and strain rate. No significant differences in mechanical properties were observed between retted and unretted fibres. The strength and percentage elongation seem to increase for both retted and unretted fibres up to a fibre diameter of 0.2×10^–3 m whereafter they remain almost constant. On the other hand, moduli seem to decrease with increase in diameter of the fibre. The observed modulus values and percentage elongation have been related to microfibrillar angle. Observed strength values have been explained on the basis of structural changes occurring with an increase in the diameter of the fibre. Scanning electron/microscope studies have indicated that the failure of the fibre is due to the fracture of the cells themselves accompanied by the uncoiling of microfibrills. There is no appreciable variation in strength and percentage elongation with strain rates for any one diameter of the fibre. On the other hand, with increase in gauge length, a decrease in both strength and percentage elongation at break has been observed. These have been attributed to an increase of probability of defects and localized deformation and gentle necking, respectively.     

Reliability of fine-pitch through-vias in glass interposers and packages for high-bandwidth computing and communications

Glass is an ideal substrate material to enable 2.5D and 3D packaging of ICs at low cost and high performance. However, it is a brittle material and is prone to failures during fabrication and operation. Large coefficient of thermal expansion (CTE) mismatch between copper and glass leads to thermomechanical stresses that can lead to glass cracking and delamination from glass interfaces. This paper focuses on modeling and reliability characterization of copper-plated through-package-vias (TPV) in glass packages. Thermomechanical simulations were carried out to obtain design guidelines for reliable TPVs in glass. Test-vehicles with different glass thicknesses and copper TPV fabrication conditions were fabricated for thermal cycling tests, resistance monitoring and failure analysis. The reliability characterization results showed good thermomechanical reliability of TPVs in ultra-thin glass panels.     

High-Temperature Tensile Behaviors of Base Metal and Electron Beam-Welded Joints of Ni-20Cr-9Mo-4Nb Superalloy

Electron beam welding of Ni-20Cr-9Mo-4Nb alloy sheets was carried out, and high-temperature tensile behaviors of base metal and weldments were studied. Tensile properties were evaluated at ambient temperature, at elevated temperatures of 625 °C to 1025 °C, and at strain rates of 0.1 to 0.001 s^?1. Microstructure of the weld consisted of columnar dendritic structure and revealed epitaxial mode of solidification. Weld efficiency of ~?90 pct in terms of strength (UTS) was observed at ambient temperature and up to an elevated temperature of 850 °C. Reduction in strength continued with further increase of test temperature (up to 1025 °C); however, a significant improvement in pct elongation is found up to 775 °C, which was sustained even at higher test temperatures. The tensile behaviors of base metal and weldments were similar at the elevated temperatures at the respective strain rates. Strain hardening exponent ‘n’ of the base metal and weldment was ~?0.519. Activation energy ‘Q’ of base metal and EB weldments were 420 to 535 kJ mol^?1 determined through isothermal tensile tests and 625 to 662 kJ mol^?1 through jump-temperature tensile tests. Strain rate sensitivity ‘m’ was low (<?0.119) for the base metal and (<?0.164) for the weldment. The δ phase was revealed in specimens annealed at 700 °C, whereas, twins and fully recrystallized grains were observed in specimens annealed at 1025 °C. Low-angle misorientation and strain localization in the welds and the HAZ during tensile testing at higher temperature and strain rates indicates subgrain formation and recrystallization. Higher elongation in the weldment (at Test temperature >?775 °C) is attributed to the presence of recrystallized grains. Up to 700 °C, the deformation is through slip, where strain hardening is predominant and effect of strain rate is minimal. Between 775 °C to 850 °C, strain hardening is counterbalanced by flow softening, where cavitation limits the deformation (predominantly at lower strain rate). Above 925 °C, flow softening is predominant resulting in a significant reduction in strength. Presence of precipitates/accumulated strain at high strain rate results in high strength, but when the precipitates were coarsened at lower strain rates or precipitates were dissolved at a higher temperature, the result was a reduction in strength. Further, the accumulated strain assisted in recrystallization, which also resulted in a reduction in strength.