Boiling of He-II on a cylindrical heater inside a porous shell with constant operation condition

This paper presents new efforts undertaken in the study of boiling in superfluid helium on the surface of a cylindrical heater located along the axis in a cylindrical cavity inside a porous shell. New experimental results are obtained with maintaining constant temperature of the helium-II and helium vapor pressure. The modernization of the experimental setup and vacuum system carried out to obtain a series of longer experiments with maintaining a stationary state are described. The basic experimental configurations are specified. Visualization of helium-II film boiling in constant operation condition is represented.

Development of a Novel Bi-Enzymatic Nanobiocatalyst for the Efficient Bioconversion of Oleuropein to Hydroxytyrosol

Lipase A from Candida antarctica (CalA) and β-glucosidase from Thermotoga maritima (bgl) were covalently co-immobilized onto the surface of chitosan-coated magnetic nanoparticles (CS-MNPs). Several parameters regarding the co-immobilization procedure (glutaraldehyde concentration, incubation time, CS-MNPs to enzyme mass ratio and bgl to CalA mass ratio) were evaluated and optimized. The developed nanobiocatalyst was characterized by various spectroscopic techniques. Biochemical parameters such as kinetic constants and thermal stability were also evaluated. The nanobiocatalytic system revealed an increase in the Km constant followed by a decrease in Vmax value compared with the native enzymes, while a significant increase (>5-fold higher) of the thermal stability of the immobilized CalA, both in individual and in co-immobilized form, was observed after 24 h incubation at 60 °C. Finally, the nanobiocatalyst was efficiently applied for the bioconversion of oleuropein to hydroxytyrosol, one of the most powerful naturally derived antioxidants, and it could be recycled for up to 10 reaction cycles (240 h of constant operation) at 60 °C, retaining more than 50% of its initial activity.

COVID-19 Lockdown and the Aerosphere in India: Lessons Learned on How to Reduce Air Pollution

The giant increase in COVID-19 infection across India forced the government to impose strict lockdown in order to curb the pandemic. Although the stringent restrictions crippled India’s economy and poor people’s livelihood, it significantly improved the air quality of most of the polluted cities of India and rejuvenated the atmosphere. Thus, the major objective of this study is to provide a comprehensive overview of lockdown on pollutants prevailing in the atmosphere. A prominent decline in primary pollutants such as Particulate matter (PM), Black carbon (BC), Oxides of nitrogen (NOx), Carbon monoxide (CO) is observed across the country. However, lockdown had a trifling impact on Sulphur dioxide (SO2) concentration over some parts of India due to the constant operation of coal-fired thermal plants as a part of essential service. Furthermore, the sudden decline in NOx concentration disturbed the complex atmospheric chemistry and lead to an enhancement of surface ozone (O3) (secondary pollutant) in many cities of India. Thus, lockdown emerged as a unique opportunity for the atmospheric researchers, policymakers as well as stakeholders to collect baseline data of pollutants and their major sources. This will help to set new targets of air quality standards and to develop various mitigation processes to combat air pollution.

Oil submersible pumps reliability during cyclic operation

The ESP reliability analysis was conducted to determine the correlation between ESP operation mode and ESP component reliability. The analysis was based on operation data of more than 700 ESP. The reliability of operating mode-dependent ESP components was analyzed. ESP and seal section test results under cyclic and constant operation conditions were shown. As a result, it was determined that periodic operation negatively affect ESP components lifetime. Recommendations for ESP cyclic operation were proposed.

Experimental Investigation and Optimization of Non-Catalytic In-Situ Biodiesel Production from Rice Bran Using with RSM Historical Data Design

Biodiesel has become one of the essential fuels in the present and future, and it can be produced from vegetable oil and animal fat. However, current feedstocks to produce biodiesel slow down the growth of biodiesel implementation due to the high cost of feedstock. As a result, rice bran oil (RBO) is claimed to be a potential feedstock for biodiesel production. A non-catalytic in-situ biodiesel production from low cost feedstock (RBO) using subcritical ethanol-water mixture probably decrease the production cost further and environmentally benign. Therefore, in this work the influence of four independent variables, adding co-solvent/without co-solvent, ethanol concentration, temperature, and time of reactions on the yield of biodiesel was examined tentatively. The independent variables limitations were (a) co-solvent of n-hexane, ethyl acetate and chloroform, (b) ethanol concentration of 20 - 80 %, v/v, (c) temperature of reaction 120 - 200 oC, and (d) time of reaction 1 - 4 h employed to direct the trials. In this examination historical data design was utilized and a quadratic polynomial model was built up and after that at last optimized by using response surface methodology (RSM). It was found that the yield of biodiesel achieved an optimum value of 79.79 %, v/v using ethyl acetate as co-solvent with ethanol concentration of 78.83 % (v/v), under constant operation conditions of P = 8 Mpa, T = 160 oC, t = 2 h, N = 400 rpm, ratio of rice bran (RB): solvent: co-solvent= 10 (g): 80 mL: 20 mL. In the other hand (rice bran 2), it was found that the yield of biodiesel achieved an optimum value of 76.98 % for 3.2 h of reaction time and temperature of reaction 200 oC, under constant operation conditions of P = 8 Mpa, co-solvent = ethyl acetate, ethanol concentration = 80 %, v/v, N = 400 rpm, ratio of RB: solvent: co-solvent= 10 (g): 80 mL: 20 mL. The examination has likewise uncovered that authentic plan information with RSM is a well-organized statistical technique for forecasting the optimum operating conditions of a non-catalytic in-situ biodiesel production from rice bran using subcritical ethanol-water mixture assumes a crucial role of ethanol concentration, types of co-solvent, temperature and time of reactions.

A Current Monitor System in High-Voltage Applications in a Range from Picoamps to Microamps

In this article, we present a system to measure current in the range of 0 to 10 μA with high-voltage isolation up to 5 kV. This current monitor consists of three ammeters connected in series, to improve the resolution in the measurement. The design features several innovative elements such as using low voltage to provide power to the devices to measure the current and digitize it with a sampling frequency of 1 KHz, it is generated based on a DC-DC converter that produces three voltages, +12 V, −12 V, and 5 V, from a conventional 10 V source. The three voltages are referenced to the same floating ground. The DC-DC converter has a high voltage insulation up to 5 kV and four optocouplers with an insulation up to 20 kV are used to read the digitized data. The introduction of a DC-DC converter contributed to reduce the noise level in the analog part of the circuit which has been resolved implementing shields inside the board. In particle physics, several systems are used to detect particles in high-energy physics experiments such as Gas Electron Multiplier (GEM), micromegas, etc. GEMs suffer small deteriorations due to discharges in constant operation and require monitoring the current consumption at high frequency (1 kHz). In this work, we present the design and operation of a 0 to 10 μA auto scale ammeter. The results obtained by monitoring the current in a 10 × 10 cm2 GEM are shown.

Photocatalytic Pretreatment of Commercial Lignin Using TiO2-ZnO Nanocomposite-Derived Advanced Oxidation Processes for Methane Production Synergy in Lab Scale Continuous Reactors

The photocatalytic pretreatment of lignocellulosic biomass to oxidize lignin and increase biomass stability has gained attention during the last few years. Conventional pretreatment methods are limited by the fact that they are expensive, non-renewable and contaminate the anaerobic digestate later on. The present study was focused to develop a metal-derived photocatalyst that can work with visible electromagnetic spectra light and oxidize commercial lignin liquor. During this project the advanced photocatalytic oxidation of lignin was achieved by using a quartz cube tungsten T3 Halogen 100 W lamp with a laboratory manufactured TiO2-ZnO nanoparticle (nanocomposite) in a self-designed apparatus. The products of lignin oxidation were confirmed to be vanillic acid (9.71 ± 0.23 mg/L), ferrulic acid (7.34 ± 0.16 mg/L), benzoic acid (6.12 ± 0.17 mg/L) and p-coumaric acid (3.80 ± 0.13 mg/L). These all products corresponded to 85% of the lignin oxidation products that were detectable, which is significantly more than any previously reported lignin pretreatment with even more intensity. Furthermore, all the pretreatment samples were supplemented in the form of feedstock diluent in uniformly operating continuously stirred tank reactors (CSTRs). The results of pretreatment revealed 85% lignin oxidation and later on these products did not hinder the CSTR performance at any stage. Moreover, the synergistic effects of pretreated lignin diluent were seen that resulted in 39% significant increase in the methane yield of the CSTR with constant operation. Finally, the visible light and nanoparticles alone could not pretreat lignin and when used as diluent, halted and reduced the methane yield by 37% during 4th HRT.

TO A QUESTION ABOUT QUASIBAND OF ACOUSTIC AXIS OF THE ANGLE BEAM PROBE

On the basis of modelling an acoustic path of the angle beam probe with a reflector as a side drilled hole influence of two factors resulting to quasiband of acoustic axis of the angle beam probe is shown, first of which is connected to change of amplitude echo signal owing to attenuation of a shear wave in the environment due to absorption and dispersion, and the second factor – with change of amplitude owing to a divergence of wave fronts radiated and received elastic waves. Influence of the first factor is increased with growth of attenuation and depth of reflector, and the second – on increase of distance up to a reflector practically does not depend. Quantitative estimations have revealed a ratio of influence of both factors on size of a angle quasiband of acoustic axis on value of factor of attenuation of shear waves. Reduction of an angle quasidand with increase of radius piezoplate of the angle beam probe is shown at constant operation frequency, that is at narrowing the directivity characteristic of the probe.

A Review of Microgrid-Based Approach to Rural Electrification in South Africa: Architecture and Policy Framework

Access to electricity for every South African citizen, including rural dwellers, is a human right issue guaranteed by the government’s laws and policies. However, many remote rural areas still suffer from a lack of this very important amenity, due to the expensive prospect of connecting them to the central national grid. The feasible approach to connecting the rural communities to electricity supply is suggestively through the use of microgrid solutions. The microgrid technology is a very recent and viable option for the energy revolution. Microgrids result from the incorporation of energy storage systems, distributed generators, and localized loads. The application of this technology requires deliberate and extensive work on the operational architecture and the policy framework to be adopted. The energy storage devices form an integral part of the microgrid configuration or architecture to make sure more maintainable and constant operation is attained. This paper presents a review of the architectures of the existing microgrid systems, as well as the policy framework for implementable solutions. The various architectures display the peculiarity of the systems based on the increased grid performance, stability, quality of electricity, and other comparative advantages. The microgrid architectures are fundamentally recognized according to their AC, DC, or hybrid distribution buses and the complexity inherent to them. In the Policy And Development Section, the problems are treated as ‘a search for the truth’—a truth being revealed by close and objective examination. The core of the problem to be solved is revealed clearly, thereby giving the basis for simplifying and solving it. The policies encourage the accomplishment of a zero-carbon dioxide (CO 2 ) emissions, energy security attainment, the meeting of the electricity demand, and, lastly, the promotion of access to electricity in rural areas. It is established that the returns through charges of the consumers are very insignificant. Although returns on investment always come in conflict with the human right demands of the local indigenes, the policy framework would be explicit on the mode of returns for the government, private partners, and the communities—a return that can be short, medium, or long term. Policymakers would be keen on the exhaustive analysis of issues, leading to optimal decision making.

Toward an Evolutionarily Appropriate Null Model: Jointly Inferring Demography and Purifying Selection

The question of the relative evolutionary roles of adaptive and nonadaptive processes has been a central debate in population genetics for nearly a century. While advances have been made in the theoretical development of the underlying models, and statistical methods for estimating their parameters from large-scale genomic data, a framework for an appropriate null model remains elusive. A model incorporating evolutionary processes known to be in constant operation, genetic drift (as modulated by the demographic history of the population) and purifying selection, is lacking. Without such a null model, the role of adaptive processes in shaping within- and between-population variation may not be accurately assessed. Here, we investigate how population size changes and the strength of purifying selection affect patterns of variation at “neutral” sites near functional genomic components. We propose a novel statistical framework for jointly inferring the contribution of the relevant selective and demographic parameters. By means of extensive performance analyses, we quantify the utility of the approach, identify the most important statistics for parameter estimation, and compare the results with existing methods. Finally, we reanalyze genome-wide population-level data from a Zambian population of Drosophila melanogaster, and find that it has experienced a much slower rate of population growth than was inferred when the effects of purifying selection were neglected. Our approach represents an appropriate null model, against which the effects of positive selection can be assessed.