Effect of cenosphere and specimen crack lengths on the fracture toughness of Al6061-SiC composites

Main aim of this work is to investigate the influences of the addition of cenosphere and specimen crack length on the fracture toughness of Al6061-SiC composites. The experimental analysis was carried out for 3, 6 and 9 wt% proportions of cenosphere with the 3 wt% of SiC as reinforcements in the aluminum 6061 matrix for various crack lengths. The fracture toughness of Al6061-SiC-Cenosphere hybrid composites was estimated using compact tension (CT) specimen for the said compositions. The CT specimens were prepared, according ASTM E399 standard, for different crack length to width (a/W=0.3-0.6) ratios. From the experimental outcomes, it is identified that the fracture toughness of the hybrid composite increases upto the 6wt% of cenosphere and further increment in the cenosphere causes the decrement in the values. It is also found that the load bearing capacity and fracture toughness of the hybrid composite decreases with increment in the a/W ratios of the CT specimen.&nbsp

Process optimization of supercritical carbon dioxide (SC-CO2) extraction parameters for extraction of deoxynojirimycin (1-DNJ) from mulberry (Morus alba L.) leaves

In the present study, supercritical fluid extraction (SFE) technology was applied to extract deoxynojirimycin (1-DNJ) from mulberry leaf powder using carbon dioxide (CO2) as major extraction solvent with ethanol as cosolvent, and extraction parameters such as pressure (100, 150 and 200 bar), temperature (40, 50 and 60 °C) anddynamic extraction time (40, 60 and 80 min) were systematically investigated by full factorial design to obtain the optimum extraction efficiency and extraction yield. Under optimized conditions (pressure of 200 bar, temperature of 50 °C and dynamic extraction time of 80 min), DNJ enriched extract was obtained with high extraction efficiency (96.46 %) and extraction yield (13.41 %), enabling this product to use for nutraceutical purpose. The results indicated that SC-CO2 extraction is a promising and alternative process for recovering the bioactive compounds from mulberry leaves

A spectroscopic analysis of the chemically peculiar star HD207561

In this paper we present a high-resolution spectroscopic analysis of the chemically peculiar star HD207561. During a survey programme to search for new roAp stars in the Northern hemisphere, Joshi et al. (2006) observed significant photometric variability on two consecutive nights in the year 2000. The amplitude spectra of the light curves obtained on these two nights showed oscillations with a frequency of 2.79 mHz [P~6-min]. However, subsequent follow-up observations could not confirm any rapid variability. In order to determine the spectroscopic nature of HD207561, high-resolution spectroscopic and spectro-polarimetric observations were carried out. A reasonable fit of the calculated Hbeta line profile to the observed one yields the effective temperature (Teff) and surface gravity (log g) as 7300 K and 3.7 dex, respectively. The derived projected rotational velocity (vsin i) for HD207561 is 74 km/sec indicative of a relatively fast rotator. The position of HD207561 in the H-R diagram implies that this is slightly evolved from the main-sequence and located well within the delta-Scuti instability strip. The abundance analysis indicates the star has slight under-abundances of Ca and Sc and mild over-abundances of iron-peak elements. The spectro-polarimetric study of HD207561 shows that the effective magnetic field is within the observational error of 100 gauss (G). The spectroscopic analysis revealed that the star has most of the characteristics similar to an Am star, rather than an Ap star, and that it lies in the delta-Scuti instability strip; hence roAp pulsations are not expected in HD207561, but low-overtone modes might be excited.Comment: 8 pages, 7 figures, 3 tables. Accepted for pubblication in MNRA

A study on growth, instability and direction of chilli trade in India

This study was aimed at studying growth, instability in area, production and productivity and direction of trade of chilli from India. Compound growth rate analysis, Instability analysis and Markov chain analytical tools were used for the study. The results indicated that the growth in area under chilli was negative, while production showed increasing growth due to increased productivity. The sources of instability in chilli production were found to be change in area variance and change in yield variance. Malaysia, Sri Lanka, United Arab Emirates and Indonesia were found to be the loyal markets for Indian chillies. The influence of export price and production on the changes in export of chilli was positive, but the influence of domestic price was negative. &nbsp

Magnetic trapping of metastable 3P2^3P_2 atomic strontium

We report the magnetic trapping of metastable $^3P_2$ atomic strontium. Atoms are cooled in a magneto-optical trap (MOT) operating on the dipole allowed $^1S_0-^1P_1$ transition at 461 nm. Decay via $^1P_1\to {^1D_2}\to {^3P_2}$ continuously loads a magnetic trap formed by the quadrupole magnetic field of the MOT. Over $10^8$ atoms at a density of $8 \times 10^9$ cm$^{-3}$ and temperature of 1 mK are trapped. The atom temperature is significantly lower than what would be expected from the kinetic and potential energy of atoms as they are transferred from the MOT. This suggests that thermalization and evaporative cooling are occurring in the magnetic trap.Comment: This paper has been accepted by PR

Evolution of the optical spectrum of SN 1987a in the large magellanic cloud

The evolution of the spectrum of SN1987a is traced from 1987 February 26 to March 31. Based on the low-resolution spectroscopic data we identify the lines of H, He I, Na I, Fe II, Sc II, Ca II which are known to be present in Type II Supernovae, and also present evidence for the existence of lines of Mg I, CaI, O I, and N I. We discuss the evolution of the Hα profile, and draw attention to its complex structure around March 30. Close to the rest wavelength of Ha a double-peaked structure appeared in the profile with a peak-to-peak separation of ~ 1400 km s−1, suggestive of an expanding shell or disc of gas. Using the available broadband photometric information, we also trace the evolution of the photosphere of SN1987a assuming that it radiates like a supergiant

Normal modes and discovery of high-order cross-frequencies in the DBV white dwarf GD 358

We present a detailed mode identification performed on the 1994 Whole Earth Telescope (WET) run on GD 358. The results are compared with that obtained for the same star from the 1990 WET data. The two temporal spectra show very few qualitative differences, although amplitude changes are seen in most modes, including the disappearance of the mode identified as k=14 in the 1990 data. The excellent coverage and signal-to-noise ratio obtained during the 1994 run lead to the secure identification of combination frequencies up to fourth order, i.e. peaks that are sums or differences of up to four parent frequencies, including a virtually complete set of second-order frequencies, as expected from harmonic distortion. We show how the third-order frequencies are expected to affect the triplet structure of the normal modes by back-interacting with them. Finally, a search for ℓ=2 modes was unsuccessful, not verifying the suspicion that such modes had been uncovered in the 1990 data set

UPSO three channel fast photometer

The design and performance of a modular portable three channel fast photometer is described. It can be disassembled as single individual channels such that the system can also be used as a single channel photometer. The instrument is put into operation since November 1999 on the 1-m UPSO telescope at Nainital. Since then, it is used extensively for the survey of roAp stars in the northern sky at UPSO. The discoveries made using this new photometer are also mentioned

High speed photometry of PG 1012-029

High speed optical photometric observations of PG 1012-029, conducted during 1990-1991, confirm the nova-like classification of the object. Several eclipses observed by us have been used to refine the orbital period of the system. Variations in the light curves and in particular, the presence of a bright hot spot in our 1991 data are high-lighted. We also deduce a maximum mass transfer rate of 1.5 10-8M⊙ yr-1 for the system

Room Temperature Optically and Magnetically Active Edges in Phosphorene Nanoribbons

Nanoribbons - nanometer wide strips of a two-dimensional material - are a unique system in condensed matter physics. They combine the exotic electronic structures of low-dimensional materials with an enhanced number of exposed edges, where phenomena including ultralong spin coherence times, quantum confinement and topologically protected states can emerge. An exciting prospect for this new material concept is the potential for both a tunable semiconducting electronic structure and magnetism along the nanoribbon edge. This combination of magnetism and semiconducting properties is the first step in unlocking spin-based electronics such as non-volatile transistors, a route to low-energy computing, and has thus far typically only been observed in doped semiconductor systems and/or at low temperatures. Here, we report the magnetic and semiconducting properties of phosphorene nanoribbons (PNRs). Static (SQUID) and dynamic (EPR) magnetization probes demonstrate that at room temperature, films of PNRs exhibit macroscopic magnetic properties, arising from their edge, with internal fields of ~ 250 to 800 mT. In solution, a giant magnetic anisotropy enables the alignment of PNRs at modest sub-1T fields. By leveraging this alignment effect, we discover that upon photoexcitation, energy is rapidly funneled to a dark-exciton state that is localized to the magnetic edge and coupled to a symmetry-forbidden edge phonon mode. Our results establish PNRs as a unique candidate system for studying the interplay of magnetism and semiconducting ground states at room temperature and provide a stepping-stone towards using low-dimensional nanomaterials in quantum electronics.Comment: 18 pages, 4 figure