50175 research outputs found
Sort by
Interpretation of bender element test results using sliding Fourier transform method
No full textIdentification of the arrival point of the shear wave in bender element tests is a task that can have ambiguous results. The contamination of the received shear wave signal with a weak P-wave component, which can emerge either directly from the transmitter or reflect from the side boundary, makes the judgement involved in this task dubious. The different available procedures to mark the arrival times of the shear wave are often prone to errors. A method is proposed to identify the time of the arrival of the shear wave. The predominant frequency of the received signal is first evaluated and then, with the help of the sliding Fourier transform approach, the arrival of the shear wave is identified. The method does not require any manual intervention. The proposed approach is applied to bender element tests performed on dry and saturated sand and glass beads by varying (i) input frequency of the signal, (ii) confining pressure, and (iii) void ratio. Results for different cases, including those obtained by using resonant column tests, are found to be very promising
Structural variations within proteins can be as large as variations observed across their homologues
No full textUnderstanding the structural plasticity of proteins is key to understanding the intricacies of their functions and mechanistic basis. In the current study, we analyzed the available multiple crystal structures of the same protein for the structural differences. For this purpose we used an abstraction of protein structures referred as Protein Blocks (PBs) that was previously established. We also characterized the nature of the structural variations for a few proteins using molecular dynamics simulations. In both the cases, the structural variations were summarized in the form of substitution matrices of PBs. We show that certain conformational states are preferably replaced by other specific conformational states. Interestingly, these structural variations are highly similar to those previously observed across structures of homologous proteins (r(2) = 0.923) or across the ensemble of conformations from NMR data (r(2) = 0.919). Thus our study quantitatively shows that overall trends of structural changes in a given protein are nearly identical to the trends of structural differences that occur in the topologically equivalent positions in homologous proteins. Specific case studies are used to illustrate the nature of these structural variations
Cobalt-Catalyzed Regioselective 4+2] Annulation/Lactonization of Benzamides with 4-Hydroxy-2-Alkynoates under Aerobic Conditions
No full textA cobalt-catalyzed regioselective 4+2] annulation/lactonization reaction of benzamides with 4-hydroxy-2-alkynoates is reported. This reaction utilizes air as an oxidant rather than metal salts. The method is operationally simple, mild, and sustainable. This protocol exhibits a broad substrate scope and compatible with a variety of functional groups furnishing the corresponding 1,4-dihydrofuro3,4-c]isoquinoline-3,5-dione derivatives in good to excellent yields with high regioselectivity
Four-State Non-malleable Codes with Explicit Constant Rate
No full textNon-malleable codes (NMCs), introduced by Dziembowski, Pietrzak and Wichs (ITCS 2010), provide a powerful guarantee in scenarioswhere the classical notion of error-correcting codes cannot provide any guarantee: a decoded message is either the same or completely independent of the underlying message, regardless of the number of errors introduced into the codeword. Informally, NMCs are defined with respect to a family of tampering functions F and guarantee that any tampered codeword decodes either to the same message or to an independent message, so long as it is tampered using a function f. F. One of the well-studied tampering families for NMCs is the t-split-state family, where the adversary tampers each of the t ``states'' of a codeword, arbitrarily but independently. Cheraghchi and Guruswami (TCC 2014) obtain a rate-1 non-malleable code for the case where t = O(n) with n being the codeword length and, in (ITCS 2014), show an upper bound of 1 - 1/ t on the best achievable rate for any t-split state NMC. For t = 10, Chattopadhyay and Zuckerman (FOCS 2014) achieve a constant-rate construction where the constant is unknown. In summary, there is no known construction of an NMC with an explicit constant rate for any t = o(n), let alone one that comes close to matching Cheraghchi and Guruswami's lowerbound! In this work, we construct an efficient non-malleable code in the t-split-state model, for t = 4, that achieves a constant rate of 1 3+., for any constant. > 0, and error 2- O(/logc+1 ), where is the length of the message and c > 0 is a constant
Optimal mechanisms for selling two items to a single buyer having uniformly distributed valuations
No full textWe consider the design of a revenue-optimal mechanism when two items are available to be sold to a single buyer whose valuation is uniformly distributed over an arbitrary rectangle c(1), c(1) +b(1)] x c(2), c(2)+b(2)] in the positive quadrant. We provide an explicit, complete solution for arbitrary nonnegative values of (c(1), c(2), b(1), b(2)). We identify eight simple structures, each with at most 4 (possibly stochastic) menu items, and prove that the optimal mechanism has one of these eight structures. We also characterize the optimal mechanism as a function of (c(1), c(2), b(1), b(2)). The structures indicate that the optimal mechanism involves (a) an interplay of individual sale and a bundle sale when c(1) and c(2) are low, (b) a bundle sale when c(1) and c(2) are high, and (c) an individual sale when one of them is high and the other is low. To the best of our knowledge, our results are the first to show the existence of optimal mechanisms with no exclusion region. We further conjecture, based on promising preliminary results, that our methodology can be extended to a wider class of distributions
Evaluation of temperature dependent electrical transport parameters in Fe3O4/SiO2/n-Si metal-insulator-semiconductor (MIS) type Schottky barrier heterojunction in a wide temperature range
No full textIn this manuscript, we reported the electrical characteristics and structural analysis of In/Fe3O4/SiO2/n-Si/In MIS-type SBD heterostructure comprehensively in the temperature range 10-300K using I-V, XRD, TEM and AFM measurements. Pulsed laser deposition in association with DC magnetron sputtering techniques has been utilized to fabricate the proposed In/Fe3O4/SiO2/n-Si/In heterojunction. The fabricated heterojunction revealed that the I-V curves are non-linear and asymmetric in nature. Using these I-V curves in the forward-bias region, SBH is calculated as 0.02eV at 10K and 0.74eV at 300K. On the other hand, the ideality factor (n) value was calculated as 7.55 at 10K and 1.37 at 300K. The series resistance (R-S) values were also evaluated using Chenug's method and the values were 1121 at 10K and 334 at 300K. The dependence of important diode parameters such as SBH, n' and R-S' on measurement temperature was effectively explained firstly on account of triple Gaussian distribution of barrier heights with the help of barrier inhomogeneities of the prepared heterojunction. The value of the Richardson's constant calculated for the fabricated In/Fe3O4/SiO2/n-Si/In heterojunction in the 110-300K temperature regime was calculated to be 115.26A/cm(2)K(2) and is approximately equal to the theoretical value of 120A/cm(2)K(2) for n-type Si. In addition, the higher value (greater than one) of ideality factor at all operating temperatures from 10-300K demonstrated that the probable current transport across the Fe3O4/SiO2/n-Si junction is not only due to the thermionic emission (TE) mechanism. Hence, to reveal the origin of current transport mechanism i.e., other than TE, we noticed that the governing current transport process through the fabricated hetrojunction is mainly due to the tunneling assisted Poole-Frenkel class of emission across the Fe3O4/SiO2/n-Si junction which is found to be temperature-dependent
Evaluation of Radarsat-2 quad-pol SAR time-series images for monitoring groundwater irrigation
No full textGroundwater assists farmers to irrigate crops for fulfilling the crop-water requirement. Indian agriculture system is characterized by three cropping seasons known as Kharif (monsoon), Rabi (post-monsoon) and summer (pre-monsoon). In tropical countries like India, monitoring cropping practices using optical remote sensing during Kharif and Rabi seasons is constraint due to the cloud cover, which can be well addressed by microwave remote sensing. In the proposed research, the strength of C-band polarimetric Synthetic Aperture Radar (SAR) time series images were evaluated to classify groundwater irrigated croplands for the Kharif and Rabi cropping seasons of the year 2013. The present study was performed in the Berambadi experimental watershed of Kabini river basin, southern peninsular India. A total of fifteen polarimetric variables were estimated includes four backscattering coefficients (HH, HV, VH, VV) and eleven polarimetric indices for all Radarsat-2 SAR images. The cumulative temporal sum (seasonal and dual-season) of these parameters was supervised classified using Support Vector Machine (SVM) classifier with intensive ground observation samples. Classification results using the best equation (highest accuracy and kappa) shows that the Kharif, Rabi and irrigated double croplands are respectively 9.58 km(2) (20.6%), 16.14 km(2) (34.7%) and 6.22 km(2) (13.4%) with a kappa coefficient respectively 0.84, 0.74 and 0.94
XRD, internal field-NMR and Mossbauer spectroscopy study of composition, structure and magnetic properties of iron oxide phases in iron ores
No full textWe report the phase-composition, structure and magnetic properties of two representative samples of naturally available iron-oxide containing ores/soils collected from two different regions in Karnataka, India. Presence of elements such as Fe, Si, Al and O were identified in both the samples using energy dispersive analysis of X-rays (EDAX). X-ray diffraction results confirmed that different ceramic phases such as crystalline iron oxide phases (Fe3O4, gamma-Fe2O3 and alpha-Fe2O3), aluminosilicates (Al2SiO5) and low-quartz (SiO2) phases constitute the soil. The presence of ferrimagnetic phases (Fe3O4, gamma-Fe2O3) makes the soil respond to a permanent magnet. Separation between the magnetic and non-magnetic phases was performed using a permanent magnet. The non-magnetic part of the sample contains a high amount of alpha-Fe2O3 phase along with aluminosilicates and low-quartz. The magnetic phases were further characterized and quantified. The presence of Fe3O4 phase in the samples was confirmed from the Verwey transition observed by internal-field NMR spectroscopy. Our results demonstrate that internal-field NMR and Mossbauer spectroscopy are complementary tools for characterizing iron containing soils. Furthermore, we found that the soil collected from the low temperature region (Sandur) contains more amounts of ferrimagnetic oxide (Fe3O4, gamma-Fe2O3) phases, whereas the high temperature region (Hospete) contains more alpha-Fe2O3 phase. Hence, our results confirm that the phase composition of the soil is intimately related to the local daily temperature. (C) 2019 The Authors. Published by Elsevier B.V
Oxidation studies of Al alloys: Part II Al-Mg alloy
No full textThe oxidation behaviour of molten Al-Mg alloys has been investigated. The oxides formed were extracted from the alloys using a novel extraction method and the oxidation mechanisms are discussed with reference to the growth behaviour of the oxides. The oxides formed in Al-Mg alloys were explored by scanning electron microscopy, X-ray diffraction and photoelectron spectroscopy. Thermodynamic calculations were performed to predict the feasibility of the reactions giving rise to oxides and to explain the oxide formation under various experimental conditions. The formation of MgAl2O4 was followed by formation of MgO as a function of time leading to depletion of Mg
Right on track? Performance of satellite telemetry in terrestrial wildlife research
No full textSatellite telemetry is an increasingly utilized technology in wildlife research, and current devices can track individual animal movements at unprecedented spatial and temporal resolutions. However, as we enter the golden age of satellite telemetry, we need an in-depth understanding of the main technological, species-specific and environmental factors that determine the success and failure of satellite tracking devices across species and habitats. Here, we assess the relative influence of such factors on the ability of satellite telemetry units to provide the expected amount and quality of data by analyzing data from over 3,000 devices deployed on 62 terrestrial species in 167 projects worldwide. We evaluate the success rate in obtaining GPS fixes as well as in transferring these fixes to the user and we evaluate failure rates. Average fix success and data transfer rates were high and were generally better predicted by species and unit characteristics, while environmental characteristics influenced the variability of performance. However, 48% of the unit deployments ended prematurely, half of them due to technical failure. Nonetheless, this study shows that the performance of satellite telemetry applications has shown improvements over time, and based on our findings, we provide further recommendations for both users and manufacturers