It is known that the shear angle is smaller in 1D vibration-assisted machining (VAM) than in conventional machining (CM). The intermittent nature of cutting in 1D VAM with the unique characteristic ...of elastic recovery is a very different machining process than CM. In this research, the chip formation in 1D VAM, which reveals the mechanism of the cutting process has been studied by Finite Element (FE) simulation to investigate the state of deformation of the chip followed by experimental analysis on a variety of metals with a set of parameters. The cutting experiments include both low-frequency and ultrasonic 1D VAM to investigate the chip formation, the forces, and the corresponding machined surfaces. It has been found from both FE simulation and experimental results that the intermittent cutting with elastic recovery and strain hardening facilitate the increased shear angle and smaller chip thickness in 1D VAM than CM. The smaller tool-chip contact length is also responsible for smaller chip thickness in 1D VAM than CM.
Weak connections between superconductors or superfluids can differ from classical links due to quantum coherence, which allows flow without resistance. Transport properties through such weak links ...can be described with a single function, the current-phase relationship, which serves as the quantum analog of the current-voltage relationship. Here, we present a technique for inteferometrically measuring the current-phase relationship of superfluid weak links. We interferometrically measure the phase gradient around a ring-shaped superfluid Bose-Einstein condensate containing a rotating weak link, allowing us to identify the current flowing around the ring. While our Bose-Einstein condensate weak link operates in the hydrodynamic regime, this technique can be extended to all types of weak links (including tunnel junctions) in any phase-coherent quantum gas. Moreover, it can also measure the current-phase relationships of excitations. Such measurements may open new avenues of research in quantum transport.
For this study a low-cost adsorbent, rice straw activated carbon (RSAC) was prepared via thermochemical routes after being impregnated with ZnCl.sub.2. Characterization studies performed on RSAC have ...revealed that RSAC is a mesoporous adsorbent with significant affinity towards 2-chlorophenol (2-CP). The optimal values for process parameters were investigated via experimental runs. The optimal values of process parameters such as RSAC dose, pH of 2-CP solution, contact time, and temperature were found to be; 1.25 g L.sup.-1. 8, 125 min and 303 K, respectively. The Langmuir isotherm and pseudo-first-order kinetics models were found to be in good agreement with the experimental data for this adsorption system. The adsorption thermodynamics studies have revealed that the adsorption of 2-CP onto RSAC is exothermic and spontaneous. Regeneration studies of RSAC using hydrogen peroxide have revealed that RSAC was effectively regenerated for four consecutive cycles. This research has proved the potential of RSAC for abating 2-CP from aqueous solutions. Keywords: adsorption 2-chlorophenol abatement, rice straw activated carbon, adsorption kinetics, adsorption equilibrium, regeneration
A Strain-Driven Morphotropic Phase Boundary in BiFeO3 Zeches, R. J.; Rossell, M. D.; Zhang, J. X. ...
Science (American Association for the Advancement of Science),
11/2009, Letnik:
326, Številka:
5955
Journal Article
Recenzirano
Odprti dostop
Piezoelectric materials, which convert mechanical to electrical energy and vice versa, are typically characterized by the intimate coexistence of two phases across a morphotropic phase boundary. ...Electrically switching one to the other yields large electromechanical coupling coefficients. Driven by global environmental concerns, there is currently a strong push to discover practical lead-free piezoelectrics for device engineering. Using a combination of epitaxial growth techniques in conjunction with theoretical approaches, we show the formation of a morphotropic phase boundary through epitaxial constraint in lead-free piezoelectric bismuth ferrite (BiFeO3) films. Electric field–dependent studies show that a tetragonal-like phase can be reversibly converted into a rhombohedral-like phase, accompanied by measurable displacements of the surface, making this new lead-free system of interest for probe-based data storage and actuator applications.
The ionospheric effects of six intense geomagnetic storms with Dst index ≤ −100 nT that occurred in 2012 were studied at a low-latitude station, Darwin (Geomagnetic coordinates, 21.96° S, 202.84° E), ...a low-mid-latitude station, Townsville (28.95° S, 220.72° E), and a mid-latitude station, Canberra (45.65° S, 226.30° E), in the Australian Region, by analyzing the storm–time variations in the critical frequency of the F2-region (foF2). Out of six storms, a storm of 23–24 April did not produce any ionospheric effect. The storms of 30 September–3 October (minimum Dst = −122 nT) and 7–10 October (minimum Dst = −109 nT) are presented as case studies and the same analysis was done for the other four storms. The storm of 30 September–3 October, during its main phase, produced a positive ionospheric storm at all three stations with a maximum percentage increase in foF2 (∆foF2%) of 45.3% at Canberra whereas during the recovery phase it produced a negative ionospheric storm at all three stations with a maximum ∆foF2% of −63.5% at Canberra associated with a decrease in virtual height of the F-layer (h’F). The storm of 7–10 October produced a strong long-duration negative ionospheric storm associated with an increase in h’F during its recovery phase at all three stations with a maximum ∆foF2% of −65.1% at Townsville. The negative ionospheric storms with comparatively longer duration were more pronounced in comparison to positive storms and occurred only during the recovery phase of storms. The storm main phase showed positive ionospheric storms for two storms (14–15 July and 30 September–3 October) and other three storms did not produce any ionospheric storm at the low-latitude station indicating prompt penetrating electric fields (PPEFs) associated with these storms did not propagate to the low latitude. The positive ionospheric storms during the main phase are accounted to PPEFs affecting ionospheric equatorial E × B drifts and traveling ionospheric disturbances due to joule heating at the high latitudes. The ionospheric effects during the recovery phase are accounted to the disturbance dynamo electric fields and overshielding electric field affecting E × B drifts and the storm-induced circulation from high latitudes toward low latitudes leading to changes in the natural gas composition O/N2 ratio.
Estuaries are known to be strong source for atmospheric CO2, however, little information is available from Indian estuaries. In order to quantify CO2 emissions from the Indian estuaries, samples were ...collected at 27 estuaries all along the Indian coast during discharge (wet) period. The emissions of CO2 to the atmosphere from Indian estuaries were 4–5 times higher during wet than dry period. The pCO2 ranged between ∼300 and 18492 μatm which are within the range of world estuaries. The mean pCO2 and particulate organic carbon (POC) showed positive relation with rate of discharge suggesting availability of high quantities of organic matter that led to enhanced microbial decomposition. The annual CO2 fluxes from the Indian estuaries, together with dry period data available in the literature, amounts to 1.92 TgC which is >10 times less than that from the European estuaries. The low CO2 fluxes from the Indian estuaries are attributed to low flushing rates and less human settlements along the banks of the Indian estuaries.
Key Points
Indian estuaries emits ~2TgC annually to atmosphere
An order of magnitude high fluxes during discharge period
Intensive microbial decomposition of organic matter is the major source
The same δ-acetoxy allenoates and thioamides, under DABCO, pyridine, or tetra-n-butyl ammonium bromide (TBAB) catalysis, undergo distinctly different annulations giving chemoselective routes to ...dihydrothiophene, thiopyran, or thiazole motifs. Thus, using pyridine in 3 + 2 annulation, dihydrothiophenes are obtained as essentially single diastereomers. By contrast, under DABCO catalysis, allenoates deliver thiopyran motifs in good to high yields through 6-exo-dig cyclization. In the thiazole forming 3 + 2 annulation, tetra-n-butyl ammonium bromide (TBAB) facilitates addition–elimination and 5-exo-trig cyclization in which β- and γ-carbons of allenoates participate to deliver thiazole cores exclusively with a Z-isomeric exocyclic double bond. A possible rationale for these observations is delved into.
► We present bulk modulus for cubic perovskites with the help of ionic charge theory. ► The proposed model only the lattice parameter is required as input. ► The method turns out to be widely ...applicable.
In this paper, semiempirical formula for the bulk modulus (B in GPa) of perovskite structured solids are elaborated in terms of lattice constant (a in Å) and product of ionic charges (ZaZbZc) of the bonding. Values of bulk modulus, of the group A+1B+2X3, (X=F, Cl, Br), A+2B+4O3 and A+3B+3O3 cubic perovskites exhibit a linear relationship when plotted against the lattice constant (a) normalization, but fall on different straight lines according to the product of ionic charges of the compounds. The resulting expressions can be applied to a broad selection of perovskite (ABX3=A: large cation with different valence, B: transition metal and X: oxides and halides) materials and their modulus predictions are in good agreement with the experimental data and those from ab initio calculations.
PDF
