[en] Many countries are planning to locate long-lived high- and intermediate-level radioactive waste disposal facilities in deep clayey geology. Bentonite was chosen as the cushioning and sealing material to fill the void in the galleries due to its low permeability and swelling properties.However, the properties of bentonite can be affected by changing geological conditions. On the one hand, the reaction of the cementitious material with the surrounding geological medium will cause an alkaline plume, leading to modifications of the chemical conditions of the geological medium; on the other hand, the anaerobic corrosion of the storage tank will generate hydrogen, which makes the clay medium including bentonite under unsaturated water condition for up to 100,000 years. The objective of the doctoral thesis is to evaluate the effect of partially water-saturated conditions on the swelling capacity of bentonite and the diffusion properties of radionuclides through the medium. At the same time, the change of chemical conditions is made, to study the joint effect of ionic strength and saturation on the swelling capacity. The thesis is divided into two parts: Firstly, from the point of view of the long-term hydro-chemical model of the evolution of bentonite, to study the correlation between the rate of diffusion and the water saturation. Diffusion tests were performed first in kaolinite, a two-phase water diffusion model was proposed. Secondly, we have studied the swelling capacity of bentonite under chemical conditions similar to the interstitial water of Cox Correlation with water saturation. Furthermore, the correlation between swelling capacity and water saturation was studied under chemical imbalance, with the influence of ionic strength and alkaline plume. (author)

[en] We report preliminary results of the temperature dependence of the lifetime spectra of natural rubber (NR) and NR loaded with 50 phr of carbon black (CB) from room temperature to below the glass transition temperature (T_g). Additional polymers to be studied include Sn-SSBR, Duradene 706, 709 and 711 and butyl rubber: both unloaded and loaded with CB N115 or N762. Different types of CB have very different structure and are expected to have different effects on the behavior of the lifetime near T_g

[en] Highlights: • Steam-Assisted Gravity Drainage (SAGD) has multiple time scales. • Time scale for steam flow in the reservoir can be immediate to 100s of days. • Time scale for bitumen mobilization, drainage, and production is up to 100s of days. • Time between steam stimulation and consequent bitumen response can be separated by 100s of days. Despite technical and economic success of Steam-assisted gravity drainage (SAGD), improvements of its thermal efficiency as reflected by the steam-to-oil ratio (SOR) present challenges. Given that the SOR is a measure of the ratio of the energy invested to the energy (chemical energy in oil) produced and emissions intensity, there is strong motivation to reduce the SOR since the lower the SOR, the lower is the energy invested and emissions produced per unit oil produced. However, there appears to be few directions for modifying SAGD to improve the SOR by adjusting the steam injection strategy or fluid production strategy alone. In this research, multiple steam components and multiple bitumen components are used in a thermal reservoir simulation model to understand the time scales of steam flow and bitumen mobilization, drainage, and production. The results reveal that immediate bitumen response is observed near the well and in the steam-trap liquid pool above the production well whereas the time scale between steam stimulation and bitumen response can be as high as hundreds of days. This brings into question the meaningfulness of the steam-to-oil ratio as a control variable for behaviours far from the well pair.

[en] To evaluate the diagnostic performance of zero echo time (ZTE) MRI in the depiction of structural lesions of sacroiliac joints (SIJs) in patients with the suspicion of sacroiliitis compared with T1-weighted fast spin echo (T1 FSE), using CT as the reference standard. Forty patients with suspicion of sacroiliitis underwent both CT and MR scans of SIJs with 80 SIJs (160 bone articular surfaces) included for analysis. Two readers independently scored SIJs for structural lesions on CT and MR images. The diagnostic capability of ZTE MRI and T1 FSE were compared by the McNemar test, using CT as the reference standard. Agreements of diagnosis and sum scores of lesions between MR sequences and CT as well as between readers were also investigated using Cohen's κappa tests and intraclass correlation coefficients. Diagnostic accuracy of ZTE MRI was higher than that of T1 FSE for erosions, sclerosis, and joint space changes (e.g., joint space changes: 91.3% vs 75.0%). ZTE MRI also improved sensitivity for detection of erosions and sclerosis (e.g., erosions at the joint level: 98.2% vs 80.0%) as well as specificity for detection of joint space changes (93.0% vs 67.4%). ZTE MRI had more consistency with CT than T1 FSE for both diagnosis and sum scores. Inter-reader agreements were higher for CT and ZTE MRI than those for T1 FSE. ZTE MRI showed superior diagnostic performance in the depiction of SIJ structural lesions compared with routine T1-weighted MRI and had reliability comparable to CT. ZTE MRI can provide CT-like bone contrast for the depiction of osseous structural lesions of the sacroiliac joints. ZTE MRI showed superior diagnostic performance than conventional T1 FSE in the detection of osseous structural lesions of sacroiliitis, using CT as the reference standard. In terms of inter-reader reliability, ZTE MRI performed comparably to CT and better than conventional T1 FSE.

[en] Highlights: • Irreversible degree of heat transfer in organic Rankine cycle (ORC) is proposed. • Theoretical model of irreversible degree is built based on a trapezoidal cycle (TPC). • Thermodynamic relation between irreversible degree and cycle performance is built and studied. • Model of working fluid with linear saturation line is proposed to study the general principles of ORC. - Abstract: Irreversible degree of heat transfer in organic Rankine cycle (ORC) is proposed in this paper. Based on a trapezoidal cycle (TPC) and its theoretical model, the model and mathematic formulas of irreversible degree of heat transfer is built. Thermodynamic relation between irreversible degree and cycle performance (thermal efficiency, net power output and exergy efficiency) is built and studied, which can be applied to the coupling optimization between cycle performance and heat transfer processes. Similar to net power output, there exists a kind of shift-curve of irreversible degree and the corresponding shift-temperature of heating fluid for working fluids, which indicates the shift of irreversible degree from having optimum condition with a minimum to monotonic decrease with heating fluid temperature. The range of irreversible degree and range of cycle performance according to irreversible degree are obtained respectively. Moreover, a model of working fluid with linear saturation line is proposed to study the general thermodynamic principles of TPC (or ORC) theoretically without the restriction of actual working fluids.

[en] An enzyme-free electrode was fabricated by anodic electrodeposition of cobalt oxyhydroxide film on an ITO electrode (CoO_x(OH)_y/ITO) for direct electrochemical detection of pyruvic acid (PA) in solution. Scanning electron microscopy (SEM) and atom force microscopy (AFM) were employed to characterize the morphology of CoO_x(OH)_y film. Cyclic voltammetry (CV) was used to investigate the electrochemical properties of PA on CoO_x(OH)_y/ITO in order to select the optimal potential for the chronoamperometric detection of PA. It was found that the CoO_x(OH)_y/ITO electrode served as an excellent PA sensor with a linear detection range of 1.00 μM to 1.91 mM, a detection limit of 0.55 μM, and a high sensitivity of 417.1 μA mM^-1 cm^-2. Moreover, the response time of CoO_x(OH)_y/ITO to PA is less than 10 s, which is the shortest for PA detection reported in literature using electrochemical method. These properties and the high stability of CoO_x(OH)_y/ITO made it a good candidate for developing electrochemical enzyme-free PA sensing device.

[en] To compare the performance of 6-min MRI with a fat-saturated 3D-controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA) Sampling perfection with application-optimized contrast using different flip angle evolution (SPACE) TSE protocol with 10-min 2D TSE MRI protocol for assessment of abnormalities of the shoulder. Forty-nine subjects underwent both 3D fat-saturated-CAIPIRINHA SPACE and 2D TSE sequences of the shoulder on a 3.0-T system. Following randomization and anonymization, two musculoskeletal radiologists evaluated the 2D and 3D images independently for image quality and diagnostic capability. Descriptive statistics, inter-observer, and inter-method concordance were investigated. p values < 0.05 were considered significant. For image quality assessment, 2D images were similar to 3D CAIPIRINHA SPACE images (p = 0.05). 3D had lower noise standard deviation (SD) and higher fluid CNR than 2D images (p = 0.00). For diagnostic capability assessment, using 2D TSE as a standard of reference, sensitivity, specificity, and accuracy of 3D SPACE were, respectively, 94.81%, 94.12%, and 94.39% for tendon abnormalities; 97.06%, 80.00%, and 91.84% for acromioclavicular joint abnormalities; 88.89%, 100.00%, and 93.89% for adjacent bone alterations; and 97.30%, 100%, and 97.96% for joint fluid/effusion assessment. The inter-method concordance was moderate to almost perfect. The inter-observer-concordance of the shoulder assessment was also moderate to almost perfect, with SSP lesions demonstrating the greatest concordance. The performance of 6-min 3D fat-saturated-CAIPIRINHA SPACE MRI for shoulder MRI is similar to that of 10-min 2D TSE MRI. 3D fat-saturated-CAIPIRINHA SPACE MRI can be utilized to reduce scan time without degradation in image quality. CAIPIRINHA acceleration 3D fat-saturated-MRI of the shoulder is achievable in 6 min with high spatial resolution. 3 D fat-saturated CAIPIRINHA MRI is similar to 2D MRI in the shoulder assessment. 3 D CAIPIRINHA MRI images enable rapid diagnosis of shoulder abnormalities without image quality degradation.

[en] Highlights: • Key thermodynamic work principles and moisture circle are investigated. • To analyze the overall efficiency, BEVP system is divided into two subsystems. • Relationship between overall efficiency and efficiency of subsystems is revealed. • The systematic feasible domain is developed for design and operation guidance. -- Abstract: There is tremendous surplus heat in flue gas from gas boilers which cannot be efficiently recovered by conventional condensing heat exchangers. As one of heat recovery systems, boilers equipped with vapor-pump system (BEVP system) is complicated. To improve system performance, theoretical investigation and mathematical models are required. However, these are not proposed in previous work. In this study, thermodynamic work principles and moisture loop of BEVP system are analyzed. It utilizes the ‘constant vapor flux’ property of natural gas combustion and the humidity level of combustion generated vapor flux depends on the humidity level of combustion air. The system is divided into two subsystems for better understanding. Subsystem I is used for dehumidification, and subsystem II is for total heat recovery, serving as a ‘vapor pump’. The core optimization principle of BEVP system is to decrease the moisture transfer driven force of vapor pump, which is used for total heat recovery in Subsystem II. A mathematical model is established to quantitatively characterize the BEVP system. Analytical solutions are derived with clear physical significances and additivity property. The mathematical model is used to conduct performance analyses under various conditions. The systematic feasible domain is developed with iso-efficiency lines.

[en] Highlights: • Exergy analysis of multi-heat recovery systems with heat pumps is proposed. • The mean heat transfer times is proposed as the key point of heat recovery process optimization. • Two specific optimization methods in graphic expression are suggested, and significant energy reduction can be achieved. -- Abstract: Large amount of low-grade waste heat is discharged into the environment during industrial processes. This part of waste heat can be collected to serve district heating systems as an important heat source. In most studies of industrial waste heat recovery, the proposed system simulations were unsophisticated in terms of analyzing the real processes. For this reason, the tangency analysis has recently been proposed, and it has been found effective in conducting optimization analysis for direct-heat-exchange systems with multi-heat sources. However, in this study, it has been found that the tangency method has limitations in designing systems with heat pumps, and therefore the disadvantages of tangency analysis are suggested and discussed. Exergy analysis reveals that without considering additional exergy generated by heat pumps, the systems designed by tangency technology tend not be the optimal configuration when heat pumps are employed. In this study, the process optimization principles have been developed from the exergy analysis of heat recovery systems with heat pumps. The optimization principles and mean-heat-transfer-times index are proposed as the key point of process design. Based on the principles, two specific optimization methods in graphic expression are suggested. In the case studies, energy input decreased by more than 70%, which compares favorably with that of tangency analysis.

[en] Highlights: • Determinants of environmental degradation in SSA countries investigated. • Ecological footprint-growth-renewables-urbanization nexus examined. • Significant cross-sectional dependence exists within the data. • Renewable energy mitigates environmental degradation but not vice versa. -- Abstract: Although Sub-Saharan Africa (SSA) countries make less environmental pollution compared with other regions, the notably increasing economic growth and accelerating process of urbanization have resulted in the increase of energy needs and, thus, lead to environmental degradation. To empirically investigate the determinants of environmental degradation by accounting for the significant roles played by economic growth, non-renewable and renewable energy consumption, and urbanization, a balanced panel dataset of 14 SSA countries over 1990–2014 is utilized. Also, the ecological footprint (EF), considered a more comprehensive indicator, is used as a proxy of environmental degradation. The results confirm strong cross-sectional dependence within the SSA countries. The Augmented Mean Group (AMG) estimator indicates that economic growth, non-renewable energy consumption, and urbanization exert positive effects on the EF in the SSA countries, while renewable energy consumption plays a negative role in the EF. Moreover, bidirectional long-run causality runs among economic growth, non-renewable consumption, urbanization, and the EF; in contrast, unidirectional causality is found to run from renewable energy consumption to the EF. Therefore, for the SSA countries, the upgrading of industrial structure and further improvement of renewable energy are needed. In addition, urbanization plays a crucial role in contributing to environmental degradation and requires immediate policy response in the SSA countries.