Polyvinyl Alcohol Fiber Length Optimization for High Ductility Cementitious Composites with Different Compressive Strength Grades

The fiber length has a significant impact on the fiber bridging capacity and the mechanical properties of high ductility cementitious composites (HDCCs), which is related to fiber/matrix interfacial bonding. However, this fundamental knowledge of HDCCs design has rarely been investigated systematically. To this end, this study deeply investigates the effect of the fiber length on the bridging stress and the complementary energy with various fiber/matrix interfacial bonds in theory. Then, the mechanical performances of HDCCs with various fiber lengths and compressive strengths were evaluated experimentally. In micromechanical design, longer fibers can achieve stronger bridging stress and more sufficient complementary energy regardless of the fiber/matrix interfacial bonding properties. However, it should be noted that the increase in bridging capacity was quite slow for the overlong fibers and excessive interfacial bonding. The experiments indicated that overlong fibers (18 mm and 24 mm) easily twined on the mixer blade and were hard to disperse evenly. The HDCCs with shorter fibers displayed better workability. The compressive strength was less affected by the fiber length, and most striking differences were less than 5.0%, while the flexural properties and the tensile properties first increased and then decreased when the fiber length ranged from 6 mm to 24 mm. Consequently, the fibers with lengths of 9 mm and the fibers with lengths of 12 mm were better candidates for the HDCCs with compressive strengths of 30 MPa to 80 MPa, and fibers with lengths of 9 mm caused the HDCCs to exhibit higher ductility properties in general.

Effect of concentration areas in sensitive analysis of a hybrid solar Brayton cycle

A simple hybrid solar thermal Brayton cycle plant thermodynamic model is evaluated in northern Colombia, where the maximum solar radiation values in the country are found. The model considers the different irreversibilities of the cycle and is coupled to a model for estimating direct solar radiation as a complementary energy source for the plant. The stability in the operation of the cycle is determined by a combustion chamber that complements the energy supply. As a result of the analysis, this work presents the sensitivity analysis of different operating parameters of the plant as a function of the areas of the concentration ratio of the solar system when the contribution of this system is maximum. It is observed that fuel consumption is reduced by 34.7% when increasing the concentration ratio between 200 and 700.

Crystal structure of the Al20Mn5.37Ni1.31 phase in the Al–Mn–Ni system

The intermetallic phase with composition Al20Mn5.37Ni1.31 (icosaaluminium pentamanganese nickel) was synthesized by high-temperature sintering of a mixture with initial chemical composition Al60Mn7Ni3. Al20Mn5.37Ni1.31 adopts the Co2Al5 structure type in space-group type P63/mmc, replacing the Co atoms with the transition-metal atoms Mn and Ni. Structure analysis revealed that one of the two transition-metal sites is partially occupied by Ni [refined occupancy 0.342 (2)] and the other is co-occupied by Mn and Ni with a ratio of 0.895 (14):0.105 (14). The present refined chemical composition is supported by complementary energy-dispersive X-ray fluorescence (EDX) analysis and is in agreement with the previously determined Al–Mn–Ni phase diagram [Balanetskyy et al. (2011). J. Alloys Compd, 509, 3795–3805].

Techno-economic assessment of the use of Linear Fresnel Solar Collectors for the supply of heat in traditional fruits and vegetable processing industries in Almeria’s province

This study presents a techno-economic assessment of the use of Linear Fresnel Solar Collectors for the heat supply in traditional fruits and vegetable processing industries in Almeria’s province. This assessment is justified by the high availability of solar radiation in the area under study, the evaluation of complementary energy self-consumption modalities, and the suitability of using local resources for the preservation and improvement of traditional productive activities. The work starts with an identification of the potential user’s needs and their location in the province. Afterward, the solar radiation resources have been estimated as they constitute one of the basic inputs for sizing the proposed systems. Together with the above, representative thermal demands have been considered and different configurations of commercial Linear Fresnel Solar Collector thermal plants aimed to contribute to solarize the analyzed productive processes have been designed and the corresponding techno-economic assessment have been undertaken. Main findings advance the profitability that can be achieved with this technology, reaching, after an optimized integration of the solar plant in the industrial process, a solar fraction between 66-82 % and payback periods of the investment between 6-12 years

A constitutive model for materials with directionally strain locking microstructures

Strain locking materials have a limit to the extent to which they can be stretched along one or more axes. The strain limit can be due to the reorientation of stiffening phases at microstructural or molecular scales along the direction of the applied load. Both natural and manmade composites can exhibit such a response when initially wavy fibers or other corrugated structures gradually straighten and limit the extensibility of the material. A new constitutive model is developed for materials that exhibit strain locking along a preferred axis. The model assumes the microstructure is composed of linear elastic material with embedded zig-zag shaped fiber phase that is oriented along the preferred locking axis. The response is governed by a complementary energy density function which is partitioned into separate portions that represent the complementary energies within the fibers and the matrix respectively. A new, nonlinear form for the complementary energy density function of strain locking fibers is derived based on a relationship between the applied stress and the strain of the fiber. An example material that exhibits strain locking longitudinally but is transversely linear-elastic is considered. The behaviors of the example material under tension and compression along the longitudinal and transverse axis are illustrated. A comparison is made with FEM modeling of a strain locking microstructure explicitly fitting the constitutive model parameters with both FEM simulated and experimental data for real material.

Energy Sustainability with a Focus on Environmental Perspectives

Energy sustainability is a key consideration for anthropogenic activity and the development of societies, and more broadly, civilization. In this article, energy sustainability is described and examined, as are methods and technologies that can help enhance it. As a key component of sustainability, the significance and importance of energy sustainability becomes clear. Requirements to enhance energy sustainability are described, including low environmental and ecological impacts, sustainable energy resources and complementary energy carriers, high efficiencies, and various other factors. The latter are predominantly non-technical, and include living standards, societal acceptability and equity. The outcomes and results are anticipated to inform and educate about energy sustainability, to provide an impetus to greater energy sustainability.

Rethinking the Boundary Conditions in the Particle-in-a-Box Mind Experiment

<p>In this manuscript, I speculated that the energy density distributions along space and time in a quantum system are uniform. Thus, the complementary energy contributions are added to the classical solutions of the 1D particle in a box problem, making the energy density a complex distribution function over space and time. Then the concept is extended to the free rotation problem with a Hamiltonian slightly different than the classical Schrödinger equation. The picturized energy distribution functions and associated time evolution are described in movies for comparison between example classical wave functions and the energy density functions. The wave functions for the hydrogen atom are then guessed based on the historical solutions.</p><p><br></p>

Rethinking the Boundary Conditions in the Particle-in-a-Box Mind Experiment

<p>In this manuscript, I speculated that the energy density distributions along space and time in a quantum system are uniform. Thus, the complementary energy contributions are added to the classical solutions of the 1D particle in a box problem, making the energy density a complex distribution function over space and time. Then the concept is extended to the free rotation problem with a Hamiltonian slightly different than the classical Schrödinger equation. The picturized energy distribution functions and associated time evolution are described in movies for comparison between example classical wave functions and the energy density functions. The wave functions for the hydrogen atom are then guessed based on the historical solutions.</p><p><br></p>

Rethinking the Boundary Conditions in the Particle-in-a-Box Mind Experiment

<p>In this manuscript, I speculated that the energy density distributions along space and time in a quantum system are uniform. Thus, the complementary energy contributions are added to the classical solutions of the 1D particle in a box problem, making the energy density a complex distribution function over space and time. Then the concept is extended to the free rotation problem with a Hamiltonian slightly different than the classical Schrödinger equation. The picturized energy distribution functions and associated time evolution are described in movies for comparison between example classical wave functions and the energy density function.</p>

Rethinking the Boundary Conditions in the Particle-in-a-Box Mind Experiment

<p>In this manuscript, I speculated that the energy density distributions along space and time in a quantum system are uniform. Thus, the complementary energy contributions are added to the classical solutions of the 1D particle in a box problem, making the energy density a complex distribution function over space and time. Then the concept is extended to the free rotation problem with a Hamiltonian slightly different than the classical Schrödinger equation. The picturized energy distribution functions and associated time evolution are described in movies for comparison between example classical wave functions and the energy density function.</p>