The effects of porosity,asphalt content and fiberglass incorporation on the tensile strength and resilient modulus of asphalt concrete blends

Asphalt concrete is the prevailing material used for road surface construction. Its adequate characteristics in providing stability, durability and driving safety are controlled by complex interactions between its components. Thus, it is important to estimate the sensitivity of asphalt concrete mechanical properties as a function of its volumetrics. For this study, different combinations between asphalt content (3.5, 5 and 7.5%) and porosity values (above 4%) were used in order to disassociate these properties. The influence of mixing in fiberglass (0.5%) was also analyzed. It was found that porosity is significantly more relevant than the asphalt content in the prediction of tensile strength and resilient modulus of fiber-free asphalt concretes. In fiber-reinforced mixtures, the mechanical properties are improved by increasing the asphalt content, which suggests a better bonding between fibers and aggregates. For both cases, decreasing porosity is beneficial. By grouping both sets of results, it was possible to create a unique theoretical curve for both the tensile strength (q_t) and the resilient modulus (RM). The RM/q_t ratio was 5800 for the fiber-free group, and 3900 for the fiber-reinforced group - suggesting a better fatigue life indicator for asphalt concretes when fibers are added.     

Optimal load distribution between units in a power plant

This paper presents a strategy for load distribution between the generating units in hydro power plants. The objective is to reach the maximum energy conversion efficiency for a given dispatched power. The developed tool employs a heuristic-based combinatorial optimization technique in conjunction with a set of system variables measurement allowing real-time load sharing. The developed equipment is used to give online energy conversion efficiency from each unit of the power plant. No specific previous information about the efficiency of system components is required. Simulation results of the proposed optimization technique when applied to typical hydro power plant data are presented.     

Deriving Efficient Porous Heteroatom‐Doped Carbon Electrocatalysts for Hydrazine Oxidation from Transition Metal Ions‐Coordinated Casein

In this work, the synthesis of high‐performance, metal ion‐imprinted, mesoporous carbon electrocatalysts for hydrazine oxidation reaction (HzOR) using casein or a family of phosphoproteins derived from cow's milk as a precursor is shown. The synthesis is made possible by mixing trace amounts of non‐noble metal ions (Fe³⁺ or Co²⁺) with casein and then producing different metal ions‐functionalized casein intermediates, which upon carbonization, followed by acid treatment, lead to metal ion‐imprinted catalytically active sites on the materials. The materials effectively electrocatalyze HzOR with low overpotentials at neutral pH and exhibit among the highest electrocatalytic performances ever reported for carbon catalysts. Their catalytic activities are also better than the corresponding control material, synthesized by carbonization of pure casein and other materials previously reported for HzOR. This work demonstrates a novel synthetic route that transforms an inexpensive protein to highly active carbon‐based electrocatalysts by modifying its surfaces with trace amounts of non‐noble metals. The types of metal ions employed in the synthesis are found to dictate the electrocatalytic activities of the materials. Notably, Fe³⁺ is found to be more effective than Co²⁺ in helping the conversion of casein into more electrocatalytically active carbon materials for HzOR.     

Touch‐Interactive Flexible Sustainable Energy Harvester and Self‐Powered Smart Card

Sustainable and safe energy sources combined with cost effectiveness are major goals for society when considering the current scenario of mass production of portable and Internet of Things (IoT) devices along with the huge amount of inevitable e‐waste. The conceptual design of a self‐powered “eco‐energy” smart card based on paper promotes green and clean energy, which will bring the zero e‐waste challenge one step closer to fruition. A commercial raw filter paper is modified through a fast in situ functionalization method, resulting in a conductive cellulose fiber/polyaniline composite, which is then applied as an energy harvester based on a mechano‐responsive charge transfer mechanism through a metal/conducting polymer interface. Different electrodes are studied to optimize charge transfer based on contact energy level differences. The highest power density and current density obtained from such a paper‐based “eco‐energy” smart card device are 1.75 W m^?2 and 33.5 mA m^?2 respectively. This self‐powered smart energy card is also able to light up several commercial light‐emitting diodes, power on electronic devices, and charge capacitors.     

The moderating role of just‐in‐time on sociotechnical practices' effect over quality and workers' health

Sociotechnical (ST) theory emphasizes the notion that the design and performance of new systems can be improved, and can only work satisfactorily within an organization if the social and the technical aspects are brought together and treated as interdependent aspects of a work system. The implementation of lean manufacturing (LM) principles and practices has become popular, despite increasing demand on the current and emerging workforce to achieve higher levels of quality and flexibility with lower costs. Exploratory studies that investigate how LM practices influence the effect of ST practices on performance are still scarce, and a holistic view of such a relationship is needed. In this context, this study aims at verifying the moderating effect of just‐in‐time (JIT) practices on the relationship between ST practices and the performance of quality and workers' health. We carried out a survey with 144 different companies from Southern Brazil that are undergoing a lean implementation. Results indicate that ST practices have a positive significant relationship with such performance, and the concurrent adoption of JIT does not undermine quality and workers' health.     

Multiaxial fatigue of quenched and tempered U2 steel: Testing and fatigue life prediction

Tension‐compression, tension‐tension, torsional, and 90° out‐of‐phase axial‐torsional fatigue tests were performed on a quenched and tempered U2 steel. All tests were conducted under force/torque control because macroscopic plastic strains were insignificant in the life range of interest (from 10⁴ to 2 × 10⁶ loading cycles). Stress‐based versions of the Fatemi‐Socie critical plane parameter and of the Smith‐Watson‐Topper parameter with a critical plane interpretation were evaluated using the experimental data. The Smith‐Watson‐Topper parameter was not able to correlate the test data. The Fatemi‐Socie method correlated most of the test data within factor‐of‐three boundaries. A modified Crossland invariant‐based parameter made of two interaction rules between the shear stress amplitude and the maximum hydrostatic stress, and of a definition of shear stress amplitude based on the maximum prismatic hull method, yielded fatigue life estimates in reasonable agreement with the experimental observations.     

Chitin derived biochar as an alternative adsorbent to treat colored effluents containing methyl violet dye

Chitin was used to prepare an alternative, eco–friendly and low–cost adsorbent by a simple pyrolysis process. The adsorbent, named chitin derived biochar, was characterized and applied to treat colored effluents containing methyl violet dye (MV). Pyrolysis using N₂ flow rate of 0.25 L min^?1, heating rate of 10 °C min^?1 until 800 °C was suitable to prepare a chitin derived biochar with good characteristics. Chitin derived biochar presented surface area of 275.0 m² g^?1. The MV adsorption on the chitin derived biochar was favored in alkaline conditions and ambient temperature. The adsorption process presented fast kinetics and, the maximum adsorption capacity was higher than 1000 mg g^?1. Chitin derived biochar can be used for 7 consecutive adsorption/desorption cycles maintaining the same adsorption capacity. Also, the material was suitable to treat colored effluents, reaching color removal percentage of 95%. In brief, it was demonstrated that chitin derived biochar is a low–cost and efficient material to treat colored effluents.     

Sensor placement optimization applied to laminated composite plates under vibration

The location optimization of sensors is a essential problem in structural health monitoring systems. Taking the cost of sensors into account, it is uneconomical to install sensors on every part of a structure and moreover in aeronautical industry, the weight is a crucial factor. In this paper, a optimal placement optimization of sensor locations for structural health monitoring systems is studied. Several techniques of optimization of sensors are approached and applied in a shell structure. The structure, a laminate of carbon fiber, was modeled by the finite element method (FEM) and then subject to free vibration. Genetic algorithms (GAs) are then employed to locate the best sensor distribution to cover a specific number of low frequency modes. Numerical results have demonstrated the overall efficiency of sensor delivery methods. Specific problems occurred, especially regarding the method of effective independence, being less efficient and discrepant in relation to the other methods employed. In summary, the results obtained in this paper provide an optimal position for sensors in real SHM systems and experiments.