A review of factors influencing performance of pervious concrete

Porozni (propusni) beton je ekološki prihvatljivo rješenje u odnosu na nepropusnosti konvencionalnih betona. Porozni beton najčešće se sastoji od mješavine cementa, krupnijeg agregata i vode. Djelomičnim ili potpunim uklanjanjem sitnog agregata dobiva se porozna struktura koja zatim utječe na svojstva poroznog betona. Cilj je ovog rada opisati glavne čimbenike koji utječu na mješavine poroznog betona, odnosno zbijenost, omjer agregata i cementnog materijala (ACR), udio pijeska, omjer vode i cementnog materijala (v/cm), veličina krupnog agregata i udio šupljina ili poroznost. Također, u radu se raspravlja i o učincima različitih dodataka, zamjenskih materijala i vlakana u mješavinama. Rezultati pokazuju da porozni beton djeluje kao učinkovit medij u promicanju održivosti urbanih sredina zbog svojih višestrukih koristi.Pervious concrete is an environment friendly solution for eliminating imperviousness-related drawbacks of conventional concrete. Pervious concrete mixes are predominantly composed of cement, coarse aggregate, and water. The partial or complete elimination of fine aggregate results in porous structure, which influences performance of pervious concrete. This article is aimed at reviewing major factors involved in the design of pervious concrete mixes, namely the compaction, aggregate to cementitious material ratio (ACR), sand fraction, water to cementitious material ratio (w/cm), size of coarse aggregate, and void ratio or porosity. The effects of various admixtures, replacement materials, and fibres, are also discussed. The results indicate that pervious concrete acts as an effective medium in promoting the sustainability of urban environments due to its multi-aspectual benefits

High nitrous oxide fluxes from rice indicate the need to manage water for both long- and short-term climate impacts

Global rice cultivation is estimated to account for 2.5% of current anthropogenic warming because of emissions of methane (CH4), a short-lived greenhouse gas. This estimate assumes a widespread prevalence of continuous flooding of most rice fields and hence does not include emissions of nitrous oxide (N2O), a long-lived greenhouse gas. Based on the belief that minimizing CH4 from rice cultivation is always climate beneficial, current mitigation policies promote increased use of intermittent flooding. However, results from five intermittently flooded rice farms across three agroecological regions in India indicate that N2O emissions per hectare can be three times higher (33 kg-N2O⋅ha−1⋅season−1) than the maximum previously reported. Correlations between N2O emissions and management parameters suggest that N2O emissions from rice across the Indian subcontinent might be 30–45 times higher under intensified use of intermittent flooding than under continuous flooding. Our data further indicate that comanagement of water with inorganic nitrogen and/or organic matter inputs can decrease climate impacts caused by greenhouse gas emissions up to 90% and nitrogen management might not be central to N2O reduction. An understanding of climate benefits/drawbacks over time of different flooding regimes because of differences in N2O and CH4 emissions can help select the most climate-friendly water management regimes for a given area. Region-specific studies of rice farming practices that map flooding regimes and measure effects of multiple comanaged variables on N2O and CH4 emissions are necessary to determine and minimize the climate impacts of rice cultivation over both the short term and long term

Nature-Inspired Design and Advanced Multi-Computational Investigations on the Mission Profile of a Highly Manoeuvrable Unmanned Amphibious Vehicle for Ravage Removals in Various Oceanic Environments

Recent large-scale operations, including frequent maritime transportation and unauthorised as well as unlawful collisions of drainage wastes, have polluted the ocean’s ecology. Due to the ocean’s unsuitable ecology, the entire globe may experience drastic aberrant conditions, which will force illness onto all living things. Therefore, an advanced system is very necessary to remove the undesired waste from the ocean’s surface and interior. Through the use of progressive unmanned amphibious vehicles (UAV), this study provides a dynamic operational mode-based solution to damage removal. In order to successfully handle the heavy payloads of ravage collections when the UAV reveals centre of gravity concerns, a highly manoeuvrable-based design inspired by nature has been imposed. The ideal creatures to serve as the inspiration for this piece are tropical birds, which have a long tail for navigating tricky situations. The design initialization was carried out by focusing on the outer body of tropical birds. Following this, special calculations were conducted and the full design parameters of the UAV were established. This study proposes a unique mathematical formulation for the development of primary and secondary design parameters of an UAV. The proposed mission profile of this application is computationally tested with the aid of sophisticated computational methodologies after the modelling of this UAV. The computational methods that are required are one-way coupling-based hydro-structural interaction assessments and computational hydrodynamic analyses. Computing is used to determine the aerodynamic and hydrodynamic forces over the UAV, the lightweight materials to withstand high fluid dynamic loads, and the buoyancy forces to complete the UAV components. These computational methods have been used to produce a flexible and fine-tuned UAV design for targeted real-time applications

Nature-Inspired Design and Advanced Multi-Computational Investigations on the Mission Profile of a Highly Manoeuvrable Unmanned Amphibious Vehicle for Ravage Removals in Various Oceanic Environments

Recent large-scale operations, including frequent maritime transportation and unauthorised as well as unlawful collisions of drainage wastes, have polluted the ocean’s ecology. Due to the ocean’s unsuitable ecology, the entire globe may experience drastic aberrant conditions, which will force illness onto all living things. Therefore, an advanced system is very necessary to remove the undesired waste from the ocean’s surface and interior. Through the use of progressive unmanned amphibious vehicles (UAV), this study provides a dynamic operational mode-based solution to damage removal. In order to successfully handle the heavy payloads of ravage collections when the UAV reveals centre of gravity concerns, a highly manoeuvrable-based design inspired by nature has been imposed. The ideal creatures to serve as the inspiration for this piece are tropical birds, which have a long tail for navigating tricky situations. The design initialization was carried out by focusing on the outer body of tropical birds. Following this, special calculations were conducted and the full design parameters of the UAV were established. This study proposes a unique mathematical formulation for the development of primary and secondary design parameters of an UAV. The proposed mission profile of this application is computationally tested with the aid of sophisticated computational methodologies after the modelling of this UAV. The computational methods that are required are one-way coupling-based hydro-structural interaction assessments and computational hydrodynamic analyses. Computing is used to determine the aerodynamic and hydrodynamic forces over the UAV, the lightweight materials to withstand high fluid dynamic loads, and the buoyancy forces to complete the UAV components. These computational methods have been used to produce a flexible and fine-tuned UAV design for targeted real-time applications

Sampling guidelines and analytical optimization for direct greenhouse gas emissions from tropical rice and upland cropping systems

<p>We describe a modified manual closed-chamber approach with detachable lid and vertically stackable chambers for sampling followed by simultaneous analysis of nitrous oxide (N₂O) and methane (CH₄) for measuring greenhouse gas flux from rice and upland cropping systems in peninsular India. A meta-analysis of leading internationally/regionally recommended approaches to monitor agricultural GHG emissions is presented to put our sampling choices (e.g., chamber design, sampling intensity, sample storage and analytical corrections) into perspective. Given our set-up, the sample retention capacity of polypropylene syringes and crimped glass vials with grey butyl-rubber septa was ∼6 hours and 10 days, respectively; and temperature correction of N₂O and CH₄ concentrations was essential but plant volume correction did not affect the flux rates substantially. Optimization of gas flow rates, pre-column sample retention period, oxygen venting and temperature/current were found to reduce run time from >14 to 7 min per sample and enhance sensitivity by 30–40% while improving analytical precision from 15–30% to < 2% relative standard deviation (RSD). We suggest an alternative to the linear interpolation approach of integrating the area under the N₂O peak because linear interpolation can overestimate the cumulative seasonal N₂O emissions by 50–100%, especially after fertilization and/or rain events.</p

Mirrorless buried waveguide laser in monoclinic double tungstates fabricated by a novel combination of ion milling and liquid phase epitaxy

Buried channel waveguides were fabricated by liquid phase epitaxial growth of a lattice-matched KY0.58Gd0.22Lu0.17Tm0.03(WO4)2 film on a microstructured KY(WO4)2 substrate. Channels were transferred to the substrates by standard photolithography and Ar-ion milling. The bottom and sidewalls of the milled channels were smooth enough (rms roughness = 70 nm and 20 nm, respectively) to favour the epitaxial growth of the active layer without defects at the boundary of substrate/epitaxial layer. The refractive index contrast was sufficient to enable light confinement and guided modes with low scattering losses were observed at wavelengths between 1440 nm and 1640 nm. CW laser operation at 1840 nm at room temperature was observed with feedback provided only by Fresnel reflection at the end faces, with slope efficiencies of 4% and 9% for TE and TM polarizations, respectively