String Effective Action and Two Dimensional Charged Black Hole

Graviton-dilaton background field equations in three space-time dimensions, following from the string effective action are solved when the metric has only time dependence. By taking one of the two space dimensions as compact, our solution reproduces a recently discovered charged black hole solution in two space-time dimensions. Solutions in presence of nonvanishing three dimensional background antisymmetric tensor field are also discussed.Comment: 11 page

High pressure-temperature proton migration in P-3 brucite [Mg(OH)2]: Implication for electrical conductivity in deep mantle

Hydrous minerals contribute largely to the transport and distribution of water into the mantle of earth to regulate the process of deep-water cycle. Brucite is one of the simplest layered dense hydrous mineral belonging to MgO-SiO2-H2O ternary system, which contains significant amount of water in the form of OH- groups, spanning a wide range of pressure stability. Simultaneously, the pressure (p) and temperature (T) induced mobility of protons within the layered structure of brucite is crucial for consequences on electrical conductivity of the mantle. Using ab initio molecular dynamics (AIMD) simulations, we investigate the diffusion of H in high-pressure trigonal P-3 polymorph of brucite in a combined p-T range of 10-85 GPa and 1250-2000K, relevant to the mantle of earth. The AIMD simulations reveal an unusual pressure-dependence of the proton migration in brucite characterized by maximum H-diffusion in the pressure range of 72-76 GPa along different isotherms. We predict that in the P-3 brucite the H mobility is onset only when a critical hydrostatic pressure is attained. The onset pressure is observed to drop with increasing temperature. The H-diffusion in brucite phase at elevated p-T takes place in such a manner that the process results in the amorphization of the H-sublattice, without disturbing the Mg- and O-sublattices. This selective amorphization yields a pool of highly mobile protons causing a subsequent increment in the electrical conductivity in P-3 brucite. Our calculated values of conductivity are compared with ex-situ geophysical magnetic satellite data indicating that brucite can be present in larger quantities in the lower mantle than previously observed. This hydroxide phase can occur as segregated patches between the dominant constituents e.g., silicates and oxides of the lower mantle and thus can explain the origin of high electrical conductivity therein.Comment: Preliminary draft, 6 figures, presented in Goldschimdt 2023 Conference (Lyon, France), comments are welcom

IoT Ecosystems Enable Smart Communication Solutions: A Case Study

The Internet of Things (IoT) is a platform for innovation, allowing people to invest in and use IoT to improve life, business, and society. It will be applicable to all or any industry sectors, verticals, people, machines, and everything. This creates difficult requirements in terms of higher system capacity, extremely low latency, such as for the tactile Internet, extremely high throughput values, a wide range of services, such as IoT and M2M, and a more uninterrupted experience. As a symbiotic confluence of up to date and existing technologies, the IOT architecture will use Hetnet RAN, Cloud enhanced RAN, and SW defined data centres to combine novel and legacy technologies. As a result, IOT will combine next-generation largearea extensible service experiences anytime and anywhere, with ultra-dense installations, nearzero latency, and GB experiences–when and where it matters. Collaboration on research, standardisation, and spectrum sharing with the IT/Internet world, industry verticals, policymakers, and academia is a significant success element. Trillions of dollars in smart ecosystems prospects covering secure connections, digital service enablement, applications and repair provisioning, and a wide range of internet of things and consumer applications are available to communications service providers and enterprises

Agricultural Waste Management by Hydrothermal Carbonization

There has been a huge emphasis on converting waste into energy in developing countries like India since a couple of decades now. Agriculture is a huge industry in India and produces huge amount of agricultural waste which goes around 350 million tons every year.  Out of this huge weight of waste more than 40 million tons is sugarcane bagasse. Only a small percentage of this waste is collected and out of that, less than 20% gets advanced treatments like incineration, pyrolysis etc. and the rest of it ends up in landfills. In this study Hydrothermal Carbonization of bagasse is carried out in order to raise its carbon content and achieve a higher calorific value. The waste after undergoing the HTC is called hydrochar and mostly resembles the properties of lignite coal. A number of tests are performed on the feedstock at 200 ° C and 220 ° C for three reaction periods viz. 2, 4 and 6 hours. The yield of the char is found to decreases with increase in temperature and retention time whereas the Carbon percentage shows a positive trend and goes as high as 69.1 % at 220° C with Calorific value as 24.44 MJ/kg at 6 hours reaction period

Bagging in overparameterized learning: Risk characterization and risk monotonization

Bagging is a commonly used ensemble technique in statistics and machine learning to improve the performance of prediction procedures. In this paper, we study the prediction risk of variants of bagged predictors under the proportional asymptotics regime, in which the ratio of the number of features to the number of observations converges to a constant. Specifically, we propose a general strategy to analyze the prediction risk under squared error loss of bagged predictors using classical results on simple random sampling. Specializing the strategy, we derive the exact asymptotic risk of the bagged ridge and ridgeless predictors with an arbitrary number of bags under a well-specified linear model with arbitrary feature covariance matrices and signal vectors. Furthermore, we prescribe a generic cross-validation procedure to select the optimal subsample size for bagging and discuss its utility to eliminate the non-monotonic behavior of the limiting risk in the sample size (i.e., double or multiple descents). In demonstrating the proposed procedure for bagged ridge and ridgeless predictors, we thoroughly investigate the oracle properties of the optimal subsample size and provide an in-depth comparison between different bagging variants.Comment: 100 pages, 34 figures; this version does slight reorganization and fixes minor typo