Rigorous Experimental Investigation Research Articles

Properties of High-Content Micro-Steel Fiber Self-Compacting Concrete Incorporating Fly Ash and Slag Powder Performance Study

The addition or substitution of various gel materials in cement-based composites has been proven to be an effective approach in enhancing the performance of concrete. Current research focuses mainly on enhancing the toughness of concrete, but lacks discussion on the performance of alternative gel materials. Therefore, this study aims to explore the effects of partially substituting cement with fly ash and slag powder as gel materials, while incorporating a high volume fraction of micro-steel fibers (6%), on the workability and mechanical properties of self-compacting concrete. By means of rigorous experimental investigation and meticulous analysis, we comprehensively assessed the workability characteristics of self-compacting concrete, encompassing critical aspects such as filling ability, cohesion, and permeability. Additionally, we conducted an extensive evaluation of the mechanical attributes of self-compacting concrete, encompassing vital parameters, such as compressive strength, axial compressive strength, splitting tensile strength, and flexural strength. Last but not least, through a holistic integration of workability and mechanical properties, we conducted a comprehensive performance evaluation of self-compacting concrete incorporating a synergistic blend of fly ash, slag powder, and micro steel fibers. The experimental results indicate that the composite addition of fly ash and slag powder in self-compacting concrete, while compatible with up to 6% micro-steel fibers, leads to a decrease in concrete workability and an increase in cohesiveness due to the addition of micro-steel fibers. Moreover, fly ash predominantly influences the tensile properties of concrete, while the addition of slag powder significantly affects the compressive and flexural properties of concrete. Additionally, the addition of micro-steel fibers significantly improves the overall mechanical properties of concrete.

Experimental Investigation of Asphaltene Deposition and Its Impact on Oil Recovery in Eagle Ford Shale during Miscible and Immiscible CO2 Huff-n-Puff Gas Injection

One of the challenges in extracting oil from unconventional resources using hydraulic fracturing and horizontal drilling techniques is the low primary recovery rate, which is caused by the ultra-small permeability of these resources. Consequently, it is essential to investigate gas injection methods to produce the trapped oil in shale formations. However, the injection process can cause asphaltene depositions inside the reservoir, leading to plugging of pores and oil recovery (OR) reduction. There has been limited research on using gas injection techniques to improve oil production in tight/unconventional resources, although carbon dioxide (CO2) and gas-enhanced oil recovery methods have been used in conventional resources. In order to determine whether or not the cyclic (huff-n-puff) CO2 process improves OR and aggravates asphaltene precipitation, a rigorous experimental investigation was undertaken utilizing filter membranes and Eagle Ford shale cores. After the minimum miscibility pressure was calculated for CO2, various injection pressures were selected to perform CO2 huff-n-puff experiments. Investigations were carried out at 70 °C on injection pressure, cycle number, production time, and huff-and-puff mode injection. The results demonstrated that when the pore size structure of the membranes used was smaller and gas injection cycles increased, a higher asphaltene weight percent (wt %) was determined during the static experiments (i.e., employing filter paper membranes). Miscibility improved OR in dynamic testing (i.e., using shale cores), but a more oil-wet system was detected in wettability measurements taken following CO2 huff-and-puff tests. The plugging impact of asphaltene particles on the pore structure was studied using optical microscopy and scanning electron microscopy imaging. Following the huff-and-puff tests, a mercury porosimeter revealed how severely the pores were plugged, and after the CO2 tests, the pore size distribution reduced as a consequence of asphaltene deposition. This study examines the significance of CO2 injection in OR under miscible/immiscible conditions to identify the critical parameters that could impact the effectiveness of CO2 huff-n-puff operation in unconventional formations.

Electrical discharges in ferrofluids based on mineral oil and novel gas-to-liquid oil

Ferrofluids consisting of stabilized iron oxide nanoparticles and insulating oils have emerged as a promising substitute for liquid dielectrics in electrical engineering applications. Recent enhancements of electrical insulating liquids rely on preparation of ferrofluids on emerging insulating oils available on the market. The present work reports on a comparative experimental study of insulating properties of a conventional mineral oil (MO)-based ferrofluid and a ferrofluid based on novel insulating oil produced by a gas-to-liquid (GTL) technology. The ferrofluids prepared on the two oils are subjected to rigorous experimental investigation of dielectric breakdown and partial discharges. The experiments are conducted on 4 MO-and 4 GTL-based ferrofluids with equal concentrations of magnetite nanoparticles. Measurements of partial discharges according to IEC 60270 are complemented with high frame–rate photography with positive streamer analysis. Based on the statistical analysis, it is found that MO-based ferrofluids exhibit superior breakdown performance to GTL-based ferrofluids, even though the pure GTL oil exhibits slightly higher mean breakdown voltage than the pure MO. A deeper analysis revealed a significantly greater number of partial discharges in GTL ferrofluids. The positive streamer size is lowered with increasing nanoparticle concentration only in MO-based nanofluids. Differences in the physical properties of the two oils, such as density, viscosity and permittivity, are considered in the interpretation of the different dielectric performance of the two ferrofluids. The experimental comparison leads to better understanding of the breakdown mechanism, and lay the foundations for proper selection of physical properties of a base oil for high performance insulating ferrofluids.

Influence of Stem Diameter on Fiber Diameter and the Mechanical Properties of Technical Flax Fibers from Linseed Flax

The continued search for sustainable and eco-friendly materials has led to the integration of bio-fibers, such as flax fiber, as reinforcement in composite materials; however, a wide variation in their diameters and mechanical properties poses a considerable challenge for their incorporation in load bearing and structural bio-composite materials. In this paper, a rigorous experimental investigation was performed using two varieties of linseed flax from two growing locations to determine if the variations observed in ultimate tensile strength, Young’s modulus, failure strain and diameter could be attributed to the diameters of the stems that produced the fibers. Tests were performed in two different facilities and the results were compared and analyzed using Welch’s t-tests. Results showed that samples which differed by stem diameter had statistically significant positive correlation with fiber diameter and negative correlation with tensile strength. No correlations for tensile strength, Young’s modulus or fiber diameter were found in samples with the same stem diameter range that were grown in different locations or were of different varieties, that is the effect of location and variety is not statistically significant. Failure strain did not show any statistical significance with respect to differences in stem diameter and only showed one statistically significant result between both facilities for one of the two growing location comparisons.

Pre-treatment of rocks prior to comminution – A critical review of present practices

It has been an established fact that comminution processes, crushing and grinding, are most energy intensive processes which account for more than half of the total energy consumed in mineral industries. Various alternative pre-treatment methods have been tried by experts around the globe. Although these methods yielded positive results in terms of reduction in energy consumption in crushing and particularly, in grinding operations at laboratory scale, their industrial application still remains an unresolved issue and challenge. Present review paper describes each one of these methods along with outcome of earlier studies and issues that need to be addressed through further rigorous experimental investigation. It also suggests the direction in which future studies can be carried out to meet the primary objective of making comminution processes more energy efficient than today they are.

On the characterization of the heterogeneous mechanical response of human brain tissue

The mechanical characterization of brain tissue is a complex task that scientists have tried to accomplish for over 50 years. The results in the literature often differ by orders of magnitude because of the lack of a standard testing protocol. Different testing conditions (including humidity, temperature, strain rate), the methodology adopted, and the variety of the species analysed are all potential sources of discrepancies in the measurements. In this work, we present a rigorous experimental investigation on the mechanical properties of human brain, covering both grey and white matter. The influence of testing conditions is also shown and thoroughly discussed. The material characterization performed is finally adopted to provide inputs to a mathematical formulation suitable for numerical simulations of brain deformation during surgical procedures.

An integrative role for the superior colliculus in selecting targets for movements.

A fundamental goal of systems neuroscience is to understand the neural mechanisms underlying decision making. The midbrain superior colliculus (SC) is known to be central to the selection of one among many potential spatial targets for movements, which represents an important form of decision making that is tractable to rigorous experimental investigation. In this review, we first discuss data from mammalian models-including primates, cats, and rodents-that inform our understanding of how neural activity in the SC underlies the selection of targets for movements. We then examine the anatomy and physiology of inputs to the SC from three key regions that are themselves implicated in motor decisions-the basal ganglia, parabrachial region, and neocortex-and discuss how they may influence SC activity related to target selection. Finally, we discuss the potential for methodological advances to further our understanding of the neural bases of target selection. Our overarching goal is to synthesize what is known about how the SC and its inputs act together to mediate the selection of targets for movements, to highlight open questions about this process, and to spur future studies addressing these questions.

An Erythroid Enhancer of BCL11A Subject to Genetic Variation Determines Fetal Hemoglobin Level

Genome-wide association studies (GWASs) have ascertained numerous trait-associated common genetic variants, frequently localized to regulatory DNA. We found that common genetic variation at BCL11A associated with fetal hemoglobin (HbF) level lies in noncoding sequences decorated by an erythroid enhancer chromatin signature. Fine-mapping uncovers a motif-disrupting common variant associated with reduced transcription factor (TF) binding, modestly diminished BCL11A expression, and elevated HbF. The surrounding sequences function in vivo as a developmental stage-specific, lineage-restricted enhancer. Genome engineering reveals the enhancer is required in erythroid but not B-lymphoid cells for BCL11A expression. These findings illustrate how GWASs may expose functional variants of modest impact within causal elements essential for appropriate gene expression. We propose the GWAS-marked BCL11A enhancer represents an attractive target for therapeutic genome engineering for the β-hemoglobinopathies.

The energy balance of a US Class A evaporation pan

Concurrent with the trend of rising global average air temperature, there have been worldwide observations of a decline in pan evaporation over the last 30–50 years. This global phenomenon has since received much attention from the scientific community. Better interpretation of the long-term trend of pan evaporation (involving seasonal and inter-annual variations) requires rigorous experimental investigation of the physics of pan evaporation. To do that, we constructed an instrumented US Class A pan that replicated an operational pan at Canberra Airport in Australia. We subsequently monitored pan evaporation and associated meteorological variables at half-hourly intervals over a three-year period (Oct 2007–Jan 2010).Extending our earlier work on the aerodynamics of pan evaporation, we conducted a theoretical and experimental study on the energy balance of the pan under non-steady state conditions. The theory considers heat exchanges at both the pan water surface and the pan wall. We formulate the radiative balance based on the geometry of the system (the pan diameter, the height of the water level, the height of the rim and solar zenith angle) and account for differences in albedo and emissivity between the pan water surface and the pan wall. The theory is used to compute all relevant energy fluxes and thereby close the energy balance. Integration of the half-hourly fluxes to a daily basis showed that we were able to close the energy budget with a RMSE of ∼18Wm−2 or 7.5% of the net short-wave radiation. We find that evaporation from our pan is dominated (∼80%) by the radiative exchanges at the pan water surface; those at the pan wall are smaller but also important. Contrary to expectation, there was little if any sensible heat exchange across the pan wall. Instead we found that the major sensible heat flux occurs across the pan water surface. Importantly, evaporative cooling at the pan water surface can result in a transfer of sensible heat from the (warmer) air to the (cooler) surface of the water body. The sensible heat flux from the overlying air to the pan water surface is minimal at low evaporation rates, but at higher evaporation rates (e.g., >300Wm−2) it contributes the equivalent of up to 15% of the total evaporative flux.

Identification of flow regimes using conductivity probe signals and neural networks for counter-current gas–liquid two-phase flow

A rigorous experimental investigation has been carried out on counter-current air–water two-phase flow in vertical tube with circular cross-section over a wide range of phase flow rates of air and water. It is a novel attempt to capture, identify and predict the individual flow regimes for different combinations of air and water superficial velocities based on some of its objective descriptions. Two different conductivity probes (parallel wire and ring probes) have been designed to collect objective descriptions of the flow regime in terms of the time series voltage signals. Statistical analyses have been carried out to characterize those time series voltage signals in terms of some statistical parameters. Three methodologies have been developed using a genetic algorithm (GA)-tuned multi-layer feed-forward neural network with back-propagation algorithm (GA-MLFFNN), a GA-tuned multi-layer radial basis function neural network with entropy-based clustering and back-propagation algorithm (GA-MLRBFNN–EC) and lastly, a GA-tuned multi-layer radial basis function neural network with fuzzy C-means clustering and back-propagation algorithm (GA-MLRBFNN–FCMC) to predict the different flow regimes after knowing the objective descriptions of the flow pattern in terms of the statistical parameters. Parallel wire conductivity probe is found to be better to capture the objective signature of the individual flow regime. GA-MLRBFNN–EC is found to be the best to predict flow regimes successfully.

Measurement and Prediction of the Thermomechanical Response of Shape Memory Alloy Hybrid Composite Beams

An experimental and numerical investigation into the static and dynamic responses of shape memory alloy hybrid composite (SMAHC) beams is performed to provide quantitative validation of a recently commercialized numerical analysis/design tool for SMAHC structures. The SMAHC beam specimens consist of a composite matrix with embedded pre-strained SMA actuators, which act against the mechanical boundaries of the structure when thermally activated to adaptively stiffen the structure. Numerical results are produced from the numerical model as implemented into the commercial finite element code ABAQUS. A rigorous experimental investigation is undertaken to acquire high fidelity measurements including infrared thermography and projection moiré interferometry for full-field temperature and displacement measurements, respectively. High fidelity numerical results are also obtained from the numerical model and include measured parameters, such as geometric imperfection and thermal load. Excellent agreement is achieved between the predicted and measured results of the static and dynamic thermomechanical response, thereby providing quantitative validation of the numerical tool.

Heuristic design of pressure swing adsorption: a preliminary study

Abstract Due to its complicated nature and multiple decision parameters including plant dimensionality and operation condition, the design of pressure swing adsorption (PSA) processes is not a trivial task. Most previous studies on PSA design have been made through rigorous modeling and experimental investigation for specific separation tasks. General heuristics for a preliminary design of PSA processes are necessary but not well investigated so far. In this paper, we attempt to develop easy-to-use rules for PSA process design, based on analysis of the inherent properties of adsorbate–adsorbent systems (i.e. equilibrium isotherm, adsorption kinetics, shape of breakthrough curves, etc.) and simulation results. These rules include the selection of adsorbent, particle size, bed size, bed configuration, purge volume, pressure equalization and vacuum swing adsorption. Results of two case studies are presented to verify the rules proposed in this preliminary study.

Social Processes Affecting the Appearance of Innovative Behaviors in Capuchin Monkeys

We consider the role of social factors in the appearance of innovative problem-solving behaviors in capuchins. Processes supporting dissemination of innovative behaviors included social enhancement of interest in the objects and area around the task and (rarely) coaction. Factors inhibiting display of innovative behaviors included restricted access and requirements for social vigilance among animals of vulnerable social status and exploitation by noninnovators of others' behaviors. We urge caution in interpreting the increased appearance of novel behaviors in primates as evidence for imitation or facilitation and call for a more rigorous experimental investigation of social learning in primates.

The Norwegian North Polar Expedition, 1893–6

ON August 29, 1893, the Fram was steaming smooth and open water between the isle Taimur and Almquist Islands; towards evening she approached thick ice in order to make fast to it. very slight current was observed as she neared the ice, but the vessel made extremely slow progress, and the speed was reduced to 1 or 11/2 knots, although the engines were working at full power, which would have given a speed of 41/2 to, knots in ordinary circumstances. Nansen's journal attributed this singular behaviour to the Fram having “got into dead-water”—a condition which has been frequently met with by ships navigating the Norwegian fords, and occasionally encountered elsewhere. Nansen consulted Prof. Bjerknes (in 1898) on the subject, and that gentleman suggested the explanation that “in the case of a layer of fresh water resting on the top of salt water, a ship will not only produce the ordinary waves at the boundary between the air and the water, but will also generate invisible waves in the boundary between salt water and fresh water;... the great resistance experienced by the ship being due to the work done in generating these invisible waves.” After some discussion between Nansen and Bjerknes it was decided to make a rigorous experimental investigation; the work was entrusted to Dr. Ekman (assistant in the Central Laboratory for the International Study of the Sea at Christiania). Its history and results are recorded in the remarkable memoir under review, which occupies the greater part of the volume in which it appears, and forms an important item in the scientific results of the North Polar Expedition. The Norwegian North Polar Expedition, 1893–6. Scientific Results. Vol. v. On Dead Water. By V. Walfrid Ekman. (London: Longmans, Green and Co., 1906.) Price 20s. net.