We examine whether the El Dorado Promise, a guaranteed college scholarship program for students in the El Dorado School District (EDSD), affected elementary and middle school achievement using a ...quasi-experimental matching design. We first match the EDSD with similar districts to create a pool of potential comparison students then match students on prior achievement and demographics. The Promise leads to an estimated 0.11 standard deviation gain in math achievement; this effect is statistically significant and practically meaningful. Results are similar from district-level synthetic control and difference-in-differences analyses. We find larger effects on students with above-average prior achievement. We are unable to construct an appropriate comparison group to estimate the impact of the Promise on literacy achievement.
•An experimental setup for supercritical helium natural convection was established.•Temperature and pressure characteristics during different processes were analysed.•Pressure severely affected the ...dynamic characteristics of temperature and pressure.•Pressurisation efficiency increased markedly with the increase of initial pressure.
Liquid hydrogen is a good energy storage medium for heavy-lift launch vehicles owing to its high energy density. A suitable pressurisation system is required when liquid hydrogen is injected into the combustion chamber from the storage tank. Helium has the advantages of stable properties and low density. Therefore, when it is used for liquid hydrogen pressurisation in heavy-lift launch vehicles, the weight can be greatly reduced. An experimental setup for supercritical helium natural convection heat transfer for liquid hydrogen pressurisation was established in this work, and the temperature and pressure characteristics during the processes of filling with liquid nitrogen, filling with helium, heating, and repeated heating were analysed based on the setup. The results showed that the cooling rate during the cooling process in the experimental cavity filled with helium was mainly dependent on the distance between the measuring point and the inner wall of the cavity, but not on the height. The heating rate in the upper part of the cavity was the fastest during the process of filling with helium as the supercritical helium with higher temperatures accumulated in this region. The pressure in the cavity substantially affected the dynamic characteristics of the temperature and pressure of the supercritical helium during the heating process. The pressurisation efficiency was increased by approximately 4.6 times when the initial pressure was increased by 7 times. The results are helpful for improving the liquid hydrogen energy storage efficiency, as well as realising a safe and efficient pressurisation of liquid hydrogen.
•A new experimental procedure to test PCM-enhanced components is presented.•A modified Dynamic Heat Flow Meter Apparatus is used to perform the tests.•The thermal conductivity of PCMs is measured in ...different phases (solid-liquid).•Indications to solve the issues related to building PCM-specimens are provided.
The implementation, in Building Performance Simulations (BPS) tools, of robust models capable of simulating the thermophysical behaviour of a Phase Change Material (PCM) represents a fundamental step for an appropriate thermal evaluation of buildings that adopt PCM-enhanced envelope components.
Reliable and robust measuring procedures are essential, at a material and component level, to provide experimental data for the empirical validation of software tools. The traditional laboratory tests that are generally used for the validation of models present some limitations, because PCMs are usually subjected to conditions that may be very different from the real boundary conditions of the building components in which PCMs are applied. Furthermore, in many experimental full-scale mockups, the relatively small quantity of installed PCM and the combination of several thermal phenomena do not allow software tools to be tested in a reliable way.
In this paper, an experimental procedure, based on a modified Heat Flow Meter Apparatus, has been developed to test the behaviour of PCM-enhanced components; the procedure, which is based on the measurement of the sinusoidal response, has been set up to provide data for the comparison and testing of numerical models and of BPS tools. Moreover, general indications and guidelines are provided to solve some issues related to building specimens that contain bulk PCM in order to obtain a more accurate measurement of their performance.
The experimental results presented in this paper were obtained from two different bulk PCMs (organic and inorganic). It was found that it is important to evaluate different PCM typologies and different thermophysical boundary conditions, including partial and full phase transitions, to test simulation codes that implement PCM modelling functions. In fact, some phenomena, such as hysteresis and subcooling effects are more evident when partial phase transition takes place. The results related to the characterization of the thermal conductivity of a paraffin-based PCM have shown a significant increase (up to 42%) of the equivalent thermal conductivity from a solid to a liquid state, with an upward heat flux, thus highlighting that further investigations and improvements are needed to measure the equivalent thermal conductivity in the different PCM phases.
Concrete possesses an intrinsic chloride binding capacity. Chloride ions from the environment bind with the hydrated cementitious phases in the form of bound chlorides. The contribution of chemically ...bound chlorides toward increasing the service life of concrete structures is vital as they help in slowing down the chloride diffusion in the concrete thereby delaying reinforcement depassivation. The authors attempt to increase the chloride binding capacity of concrete by adding a small amount of Mg–Al–NO2 layered double hydroxides (LDHs) with the objective to delay reinforcement corrosion and by this to considerably extend the service life of concrete structures situated in harsh environments. This study presents numerical and experimental analysis of the action of LDH in concrete. Formation factor is used to determine the effective chloride diffusion coefficient. In addition, the chloride binding isotherms together with Poisson–Nernst–Planck equations are used to model the chloride ingress. A comparable chloride binding is observed for concrete with and without Mg–Al–NO2, depicting only a slight chloride uptake by Mg–Al–NO2. Further investigations are conducted to understand this behavior by studying the stability and chloride entrapping capacity Mg–Al–NO2 in concrete.
Mg–Al–NO2 layered double hydroxide (LDH) is incorporated in concrete to increase the amount of bound chlorides. The performance of LDH is evaluated by modeling the chloride transport in concrete using finite element analysis. In situ X‐ray diffraction (XRD) and calorimetry analysis help in understanding the reactiveness and stability of LDH particles in concrete.
An innovative procedure is introduced for the identification of the mechanical parameters of orthotropic plates of arbitrary shape, under various boundary conditions, based on vibration data. The ...method employs a combination of a convenient Rayleigh-Ritz approach and Particle-Swarm Optimization to estimate elastic constants of the orthotropic material in a straightforward manner, without requiring computationally demanding iterative Finite Element analyses. Specifically, the pb-2 Rayleigh-Ritz procedure is extended and applied to deal with orthotropic plates, simplifying the approach to more easily treat generic plate shapes, taking advantage of the Green's theorem. The method is then appropriately combined with the Particle-Swarm Optimization procedure to expeditiously identify material parameters based on available vibration data. Several numerical applications are presented to show the reliability of the approach, and comparisons with pertinent results available in the literature demonstrate the efficiency and accuracy of the proposed procedure. The study is then supplemented by experimental tests developed in the Laboratory of Experimental Dynamics at the University of Palermo, Italy. In this context, because of the obvious relevance for modern additive manufacturing processes, vibration tests are performed on several 3D printed stiffened plates. Numerical vis-à-vis experimental data are examined, showing that the proposed procedure accurately capture equivalent orthotropic parameters of the stiffened plates.
Effects of processing and extraction solvents on antioxidant properties and other characteristics were evaluated for ten medicinal plant species originating from two different localities and two ...production years. A combination of spectroscopic and liquid chromatography techniques possessed data for multivariate statistics. Water, 50% (
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) ethanol, and dimethyl sulfoxide (DMSO) were compared to select the most suitable solvent for the isolation of functional components from the frozen/dried medicinal plants. DMSO and 50% (
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) ethanol were evaluated as more efficient for phenolic compounds and colorants extraction, while water was more useful for element extraction. Drying and extraction of herbs with 50% (
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) ethanol was the most appropriate treatment to ensure a high yield of most compounds. The satisfactory differentiation of herbs (61.8-100%) confirmed the significant effect of the processing, geographical, and seasonal factors on target functional component concentrations. Total phenolic and total flavonoid compounds content, total antioxidant activity expressed as TAA, yellowness, chroma, and browning index were identified as the most important markers for medicinal plant differentiation.
•The first study to carry out the in-depth investigation method of vehicle fire accidents.•The causes of vehicle fire are analyzed, and the accident path of "defect → fault → accident" is put ...forward.•Data of vehicle fire caused by defects can be obtained from historical cases. Combining with trace analysis and scene test, it can effectively judge whether the vehicle fire is caused by defects.
Vehicle fire is a very serious safety accident. At the same time, the defects of vehicle products are closely related to vehicle fire accidents. Based on the comprehensive analysis of the defects of vehicle product recall data and the cause of vehicle fire accidents, this essay explicitly points out that the defects of fuel system, electrical system and other flammable liquid transportation systems are the main causes of vehicle fire, and take the detectability as index to reveal the correlation between detectability and the tendency of accident occurrence was negative. Based on scene investigation and experimental analysis, a method for in-depth investigation of deep accident in vehicle fire is proposed, which uses scene reorganization and traces inspection as means. Through the application analysis of three different vehicle fire cases, it is verified that the accident in-depth investigation method can achieve good results in judging whether the vehicle products have defects and the relationship between defects and fire accidents.
Steel ties perform a key structural role in ensuring the stability of buildings façades built with brick masonry veneer walls. These elements are responsible for transferring the loads acting on the ...veneer wall to the main structure, which typically consists of masonry infill walls used in reinforced concrete frames buildings. Such constructive system is common in Portugal and other Mediterranean countries where the seismic hazard is high. In the event of an earthquake, the ties have to transfer the out-of-plane loads and are subjected to significant tension and compression stress. The characterization of the seismic behavior of these tie connections is an insufficiently explored topic. Despite the codes available for the design of brick masonry veneers and ties, recent earthquakes brought to light the seismic vulnerability of this constructive system. The present paper proposes a simplified spring numerical model validated with experimental results. The simplified model can be applied to perform numerical analyses of greater scale (e.g. to analyze full façades of buildings), which can help to optimize the design. Finally, the paper identifies a common construction problem, which is the probable misalignment of the mortar joints of the masonry walls. A construction solution is proposed by the authors.
Debates in fields studying the biological aspects of aging and longevity, such as biogerontology, are often split between ‘anti-aging’ approaches aimed largely at treating diseases and those focusing ...more on maintaining, promoting, and even enhancing health. However, it is far from clear what this ‘health’ is that would be maintained, promoted, or enhanced. Interestingly, what few have yet to fully reflect on is that there is still no theory of health within the health or aging sciences that would provide an integrative explanatory framework akin to other scientific theories. After clarifying why such a theory could be useful, I discuss five general features of medical theories that could be used to evaluate the utility of a given proposal. With these features in hand, I suggest that philosophers and scientists work together on analyzing actual medical research (experimental analysis), and the ways in which a theoretical construct of ‘health’ is being progressively identified and measured therein. I conclude by suggesting that research fields studying stress and aging might be particularly helpful in developing candidates for theory construction due to their broad scope, increasing specificity, and potential for providing integrative explanations.
Foamy oil flow is one reason that contributes to the high recovery factor observed in the heavy oil reservoirs. Although the viscosity of heavy oil, as a critical fundamental property, has been ...noticed by many researchers, the viscosity effect on foamy oil flow remains unclear. Therefore, this work conducted experimental analysis to study the viscosity effect on the foamy oil and oil recovery factor. Based on the experimental analysis, optimal oil viscosity was determined for optimizing foamy oil behavior in the porous media. Stronger foamy oil flow was observed with higher oil viscosity. Due to the low mobility of high oil viscosity, a stronger foamy oil flow does not necessarily mean a higher oil recovery factor. With the increases of dead oil viscosity from 2200 mPa·s to 6600 mPa·s, oil recovery increases from 10.55% to 14.10%. When the dead oil viscosity further increases to 144,000 mPa·s, oil recovery drops to 10.43%. Another important observation is the second foamy oil flow, which occurs during the late stage of oil production for experiments of relatively high oil viscosity. During secondary foamy oil flow, the oil production rate increases again with an increased pressure gradient of the sand-pack and gas production rate drops. All those phenomenal indicate that given preferable oil viscosity and gas-oil ratio (GOR), foamy oil can occur multiple times, which provides significant understanding of current foamy oil study. Therefore, optimizing oil viscosity during each production stage will result in stronger foamy oil flow AND maintained the oil mobility during production.
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