Impatti, adattamento e vulnerabilita Le cause e le responsabilita dei cambiamenti climatici sono state trattate sul numero di ottobre della rivista Cda. Approfondiamo l’argomento presentando il documento: “Cambiamenti climatici 2007: impatti, adattamento e vulnerabilita” votato ad aprile 2007 dal secondo gruppo di lavoro del Comitato Intergovernativo sui Cambiamenti Climatici (Intergovernmental Panel on Climate Change). Si tratta del secondo di tre documenti che compongono il quarto rapporto sui cambiamenti climatici.

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Climate Change 2007: Impacts, Adaptation and Vulnerability.

This article reports on the International Nanofluid Property Benchmark Exercise, or INPBE, in which the thermal conductivity of identical samples of colloidally stable dispersions of nanoparticles or “nanofluids,” was measured by over 30 organizations worldwide, using a variety of experimental approaches, including the transient hot wire method, steady-state methods, and optical methods. The nanofluids tested in the exercise were comprised of aqueous and nonaqueous basefluids, metal and metal oxide particles, near-spherical and elongated particles, at low and high particle concentrations. The data analysis reveals that the data from most organizations lie within a relatively narrow band (±10% or less) about the sample average with only few outliers. The thermal conductivity of the nanofluids was found to increase with particle concentration and aspect ratio, as expected from classical theory. There are (small) systematic differences in the absolute values of the nanofluid thermal conductivity among the various experimental approaches; however, such differences tend to disappear when the data are normalized to the measured thermal conductivity of the basefluid. The effective medium theory developed for dispersed particles by Maxwell in 1881 and recently generalized by Nan et al. [J. Appl. Phys. 81, 6692 (1997)], was found to be in good agreement with the experimental data, suggesting that no anomalous enhancement of thermal conductivity was achieved in the nanofluids tested in this exercise.

A Benchmark Study on the Thermal Conductivity of Nanofluids

Keywords: Mecanique des sols ; Drainage ; Ecoulement souterrain Reference Record created on 2004-09-07, modified on 2016-08-08

Applications of soil physics.

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Analysis of observed chaotic data

http://www.saetaequina.com/files/1-s2_0-S0950061811006763-main.pdf

A simple review of soil reinforcement by using natural and synthetic fibers

Rock weathering fractures in nature are complex and fracture healing is an effective strategy for rock weathering mitigation. This study is a first attempt to apply microbially induced calcium carbonate precipitation (MICP) technology in the healing of nature-weathering-like rough fractures (NWLRF). Sandstone was studied as an example due to its wide distribution as construction, sculpture and monument materials all over the world. To achieve a high healing efficiency, a repeated mixture injection strategy was proposed. Based on a series of laboratory MICP injection experiments on four types of NWLRF, we systematically explored the fundamental micro-healing mechanism and the influence factors including fracture aperture, characteristics of branch fractures, and cementation solution concentration. Experimental results demonstrated that MICP healing with the repeated mixture injection strategy had the ability to efficiently heal the penetrated NWLRF well with length in centimeter scale and aperture in millimeter scale, but cannot heal the non-penetrated branch fractures under low injection pressure. The repeated mixture injection strategy furtherly achieved a high apparent fracture healing ratio and a significant reduction of transmissivity. The apparent fracture healing ratios of all main fractures were higher than 80% and the maximum was 96.3%. Fracture transmissivity was reduced by at least three orders of magnitude from about 1 × 10–4 m2/s to less than 1 × 10–7 m2/s, and the highest reduction reached to four orders of magnitude. For the aspect of the effects, larger cementation solution concentration, finer aperture and penetrated branch fracture were beneficial to improve the healing effect. Moreover, the MICP healing mechanism with high fracture healing ratio and significant reduction of transmissivity on sandstone NWLRF was also analyzed. The research results have important theoretical significance and technical guidance value for the disaster prevention and mitigation of rock weathering. 

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Microbial healing of nature-like rough sandstone fractures for rock weathering mitigation

This study proposed a novel bio-carbonation method of reactive magnesia cement (RMC) with urea pre-hydrolysis for geomaterial stabilization. Urea pre-hydrolysis in the bacteria solution before mixing with RMC produced more carbonate and ammonia, facilitating the RMC bio-carbonation to form more hydrated magnesia carbonates (HMCs), the dominant product that contributed to the strength gain. The effect of urea pre-hydrolysis on the engineering performances of bio-carbonated samples was investigated through a series of RMC bio-carbonation geomaterial stabilization tests with various pre-hydrolysis times and urea concentrations. The results showed that the proposed method can improve material utilization, enhance RMC bio-carbonation reaction, and promote geomaterial stabilization performance. The relationships between the unconfined compressive strength (UCS) of bio-carbonated samples and the amount of HMCs were studied by a proposed indicator, degree of carbonation (DC). However, the strength increment was not monotonous with the amount of the HMCs. The optimal pre-hydrolysis time was 6-12 hours for the bio-carbonated samples with UCS up to 3.79 MPa, and the maximum UCS increase of the samples was up to 404.42%. The critical DC values ranged 0.23-0.36 with varying urea concentrations. The proposed method had implications for the design of bio-carbonated RMC in field applications.

A novel bio-carbonation method of reactive magnesia with urea pre-hydrolysis for geomaterial stabilization

Determination of dry soil layer and its soil heat flux distribution using actively heated distributed temperature sensing

https://link.springer.com/content/pdf/10.1007/s10064-022-02668-1.pdf

Chao-Sheng Tang

Papers

Microbial healing of nature-like rough sandstone fractures for rock weathering mitigation

A novel bio-carbonation method of reactive magnesia with urea pre-hydrolysis for geomaterial stabilization

Determination of dry soil layer and its soil heat flux distribution using actively heated distributed temperature sensing

Correction to: Desiccation cracking in clay‑bottom ash mixtures: insights from crack image analysis and digital image correlation

Probability Density Function of Geometrical Properties of Soil Desiccation Cracks at Different Relative Humidity Levels