Airflow in a slot-ventilated enclosure partially filled with porous boxes: Part I - Measurements and simulations in the clear region

A reduced-scale model and CFD predictions were used to investigate experimentally and numerically the airflow patterns within a ceiling slot-ventilated enclosure partially loaded with vented boxes filled by spherical objects. The experiments were carried out using laser Doppler velocimetry. Airflows around and inside porous boxes were predicted taking into account their aerodynamic interactions. This work is divided into two parts. This paper presents part I and concerns the air velocity characteristics within the jet above the boxes, while Part II deals with the air velocity characteristics inside the boxes. The results highlight the confinement effect due to the enclosure and the influence of load porosity on jet penetration, its development and hence the heterogeneity of ventilation within the enclosure. The numerical predictions obtained with the computational fluid dynamics Fluent package using the RSM turbulence model show reasonable agreement with experimental data. Predicted velocity profiles were generally within an error of 3-30% of the measured velocities.     

Comparing Linear Viscoelastic Properties of Asphalt Concrete Measured by Laboratory Seismic and Tension–Compression Tests

Seismic measurements and conventional cyclic loading have been applied to a cylindrical asphalt concrete specimen to compare the complex modulus and complex Poisson’s ratio between the two testing methods. The seismic moduli and Poisson’s ratio have been characterized by optimizing finite element calculated frequency response functions to measurements performed at different temperatures. An impact hammer and an accelerometer were used to measure the frequency response functions of the specimen which was placed on soft foam for free boundary conditions. The cyclic loading was performed by applying both tension and compression to the specimen while measuring the displacements in the axial and radial direction. The Havriliak–Negami and the 2S2P1D model have been used to estimate master curves of the complex modulus and complex Poisson’s ratio from the seismic and the tension–compression tests. The seismic measurements performed at a lower strain level than the tension–compression test give a higher absolute value of the complex moduli (e.g. \({\sim }12\,\%\) at 100 Hz) and a lower phase angle compared to the tension–compression results.     

Air velocity characteristics within vented pallets loaded in a refrigerated vehicle with and without air ducts

During transport using refrigerated vehicles, this being a vital link in the cold chain, the maintaining of even temperature throughout the cargo is essential in order to preserve the quality, safety and shelf life of perishable food. Within the refrigerated container, the temperature level and its homogeneity are directly governed by airflow patterns. The design of the air-distribution system should allow these airflows to compensate heat fluxes exchanged through the insulated walls or generated by the products.In this paper, a reduced-scale model and CFD predictions were used to investigate experimentally and numerically the airflow patterns within a typical refrigerated truck configuration loaded with vented pallets filled with spherical objects. The experiments were carried out using a laser Doppler velocimetry and thermal sphere-shaped probes located inside the pallets. The aim was to investigate air velocity characteristics above and within pallets. The performance of ventilation was characterized with and without supply air duct systems. Both configurations are extensively used in refrigerated transport. Full-scale measurements were also performed within a load of fruit during transport in a refrigerated truck in order to evaluate the temperature distribution under given operating conditions.The numerical modelling of airflow was performed using the computational fluid dynamics (CFD) fluent code and the Reynolds Stress Model (RSM) turbulence model. Numerical and experimental data make it possible to evaluate the air ventilation levels and their heterogeneity between the pallets. The numerical predictions show reasonable agreement with experimental data. The studied supply air duct system improves significantly the homogeneity of ventilation in the vehicle.     

Combining Artificial Neural Network Models, Geostatistics, and Passive Microwave Data for Snow Water Equivalent Retrieval and Mapping

A new modeling framework combining neural-network-based models, passive microwave data, and geostatistics is proposed for snow water equivalent (SWE) retrieval and mapping. Brightness temperature data from the seven-channel special sensor microwave/imager and the interpolated minimum temperature are the inputs of a multilayer feedforward neural network (MFF). Kriging with an external drift algorithm is applied to ground-based SWE data to produce gridded SWE data that are used as the target of the neural network. An optimal division of the sample of available pixels is achieved by a self-organizing feature map. Prediction error is used for model selection and is assessed by bootstrap. It is shown that a committee of a network containing neural networks with different architectures can provide consistent SWE retrievals. This modeling framework is applied for SWE retrieval and mapping over La Grande River basin in north eastern Quebec (Canada). The results are very promising for operational purposes particularly for SWE mapping during periods with no ground measurements and operational streamflow forecasting.     

Ex vivo Activities of β‐Lapachone and α‐Lapachone on Macrophages: A Quantitative Pharmacological Analysis Based on Amperometric Monitoring of Oxidative Bursts by Single Cells

Artificial synapses for femtomolar detection : Amperometry at platinized carbon fibre electrodes has been used to unravel the complexity of β‐lapachone's effects on cellular oxidative stress. α‐Lapachone, the pharmacologically inactive para‐quinone isomer, did not display such characteristics, but over longer incubation periods both quinones induced apoptosis. The observed effects were interpreted in terms of two mechanisms involving opposite reactivities of quinones in living cells.

     

Airflow patterns inside slotted obstacles in a ventilated enclosure

Laser Doppler measurements and CFD predictions were carried out to characterize air flow pattern, mean velocities and turbulence structure inside slotted boxes stacked within a slot ventilated enclosure. Special attention was paid to the strong aerodynamic interactions observed on the top faces of the slotted boxes, between the external main flow and the return flow which predominate inside the boxes. Numerical and experimental data make it possible to evaluate the air ventilation levels and their heterogeneity for the different boxes. The two turbulence models used, RSM and k-ε, give quite similar results for the velocity levels in the load and show qualitative agreement with experiments.     

Thermomechanical characterization of asphalt mixtures modified with high contents of asphalt shingle modifier (ASM®) and reclaimed asphalt pavement (RAP)

The reuse of reclaimed asphalt pavements (RAP) in asphalt mixes at high substitution rates has become a major economical and environmental necessity. However, this reuse of RAP is technically limited by the impact of RAP on the behavior of the mixes and industrially limited by the incorporation capacity of RAP in plants. On the other hand, several studies and industrial experiences showed that the reuse of manufacturer-waste asphalt roofing shingles as a modifier in asphalt mixes enhances the behavior of the asphalt mixes at different levels (fatigue, rutting and stiffness) without having a negative impact on low-temperature cracking when an appropriate asphalt mix design is used. The objective of this paper is to assess the behavior of asphalt mixes using a combination of RAP and asphalt shingle modifier (ASM^®) together at high substitution rates. An experimental program was set up and carried out at the Lafarge Research Center and the French Ecole Nationale des Travaux Publics de l’Etat. A reference mix, and other mixes, modified with different percentages of RAP and ASM^® were evaluated. The experimental results showed that the mixes with up to 15 % of RAP and 5 % of RAS behave well compared to the reference mix. Beyond these limits, low-temperature cracking behavior could be altered. Certain technical solutions were then evaluated and are presented in this paper.     

Angeli's salt (Na2N2O3) is a precursor of HNO and NO: a voltammetric study of the reactive intermediates released by Angeli's salt decomposition

Under physiological conditions, it is usually accepted that the aerobic decomposition of Angeli's salt produces nitrite (NO(2)(-)) and nitroxyl (HNO), which dimerizes and leads to N(2)O. No consensus has yet been established on the formation of nitric oxide (NO) and/or peroxynitrite (ONOO(-)) by Angeli's salt. Because this salt has recently been shown to have pharmacological properties for the treatment of cardiovascular diseases, identification of its follow-up reactive intermediates is of increasing importance. In this work, we investigated the decomposition mechanism of Angeli's salt by voltammetry performed at platinized carbon fiber microelectrodes. By following the decomposition process of Angeli's salt, we showed that the mechanism depends on the experimental conditions. Under aerobic neutral and slightly alkaline conditions, the formation of HNO, NO(2)(-), but also of nitric oxide NO was demonstrated. In strongly alkaline buffer (pH>10), we observed the formation of peroxynitrite ONOO(-) in the presence of oxygen. These electrochemical results are supported by comparison with UV spectrophotometry data.     

Three‐dimensional analysis of fatigue tests on bituminous mixtures

A tension–compression test on cylindrical specimens was used to study the three‐dimensional behaviour of bituminous mixtures during fatigue tests. The tests were carried out at 10 °C, 10 Hz at constant strain amplitude mode. The axial strain, radial strain and axial stress were measured using a prototype apparatus developed at the University of Lyon/“Ecole Nationale des TPE” (ENTPE). In addition to axial stress and strain analysis, the measurements of the radial strain made it possible to obtain the complex Poisson ratio and the volumetric strains during the tests. The results showed good correlations between the volumetric strains and global damage. The effects of the change of temperature due to viscous dissipation on the volumetric strain and on the complex modulus were also analysed.