The geological strength index: applications and limitations

The geological strength index (GSI) is a system of rock-mass characterization that has been developed in engineering rock mechanics to meet the need for reliable input data, particularly those related to rock-mass properties required as inputs into numerical analysis or closed form solutions for designing tunnels, slopes or foundations in rocks. The geological character of rock material, together with the visual assessment of the mass it forms, is used as a direct input to the selection of parameters relevant for the prediction of rock-mass strength and deformability. This approach enables a rock mass to be considered as a mechanical continuum without losing the influence geology has on its mechanical properties. It also provides a field method for characterizing difficult-to-describe rock masses. After a decade of application of the GSI and its variations in quantitative characterization of rock mass, this paper attempts to answer questions that have been raised by the users about the appropriate selection of the index for a range of rock masses under various conditions. Recommendations on the use of GSI are given and, in addition, cases where the GSI is not applicable are discussed. More particularly, a discussion and suggestions are presented on issues such as the size of the rock mass to be considered, its anisotropy, the influence of great depth, the presence of ground water, the aperture and the infilling of discontinuities and the properties of weathered rock masses and soft rocks.     

Assessment of ground conditions with respect to mechanised tunnelling for the construction of the extension of the Athens Metro to the city of Piraeus

This paper refers to the proposed western extension of the Athens Metro to Piraeus city. The railway consists of a 9.45 m diameter, 8.2 km long tunnel and seven stations. Tunnelling works are expected to be undertaken within a variety of lithological formations ranging from very strong alpine limestones to recent soft littoral deposits. The tunnel alignment was divided into 12 areas with respect to the geological and geotechnical conditions that may be encountered during construction. In many of these zones, the geotechnical conditions together with the presence of sensitive surface and/or subsurface structures led to the selection of a closed-face TBM (Earth Pressure Balance Machine or Slurry Tunnel Boring Machine) as the appropriate tunnelling technique. The Piraeus extension is a project where in places both types of commonly used closed-face tunnelling machines will encounter ‘text book’ application areas, but not always. The applicability of each type of TBM is discussed using the available data obtained from an extensive site investigation.      

Interleukin-12 induction of Th1 cytokines is important for viral clearance in chronic hepatitis B

Interleukin-12, a cytokine with an important role against intracellular pathogens, promotes Th1 cell development, cellmediated cytotoxicity, and interferon-gamma production. We investigated the immunoregulatory role of IL-12 in 72 chronic hepatitis B virus (HBV) carriers, 33 of whom were monitored longitudinally during interferon-alpha treatment. Serum levels of IL-12 heterodimer, IL-12 p40 subunit, IL-4, and Th1 cytokines were determined by specific ELISAs, and hepatitis B core antigen-specific T cell response by a proliferation assay. Chronic HBV carriers had higher serum levels of IL-12 and IL-12 p40 in comparison with controls (P < 0.01), suggesting that IL-12 production is not impaired. The longitudinal analysis revealed a further substantial increase (> 2.5x baseline level) of bioactive IL-12 and Th1 cytokines in patients who cleared HBV and seroconverted to anti- hepatitis B e, unlike the 23 nonresponders with persistent HBV replication (P < 0.01). The IL-12 peak followed the peak of hepatocytolysis by 9.8+/-2.8 wk and occurred either before or simultaneously with hepatitis B e seroconversion. Hepatitis B core antigen-specific T cell proliferation closely correlated with hepatocytolysis and increased significantly in all patients (8 responders and 15 nonresponders) who developed hepatitis flare, irrespective of the virological outcome. These results provide in vivo evidence that IL-12 may have an important role for viral clearance in chronic HBV infection.     

Exact ESCT minimization for functions of up to six input variables

In this paper, an efficient algorithm for the synthesis and exact minimization of ESCT (exclusive or sum of complex terms) expressions for Boolean functions of at most six variables is proposed. This kind of logical expressions can be mapped to a special cellular architecture, called reversible wave cascade architecture. This topology is useful, because it has been proved to be reversible and moreover it may help in the design of quantum circuits. The proposed algorithm is the first one to give solution to the problem of finding minimal ESCT expressions for switching functions of up to six input variables.     

Environmental effects in a karstic aquifer due to seepage from an in-river reservoir

The paper estimates the anticipated changes in the seepage conditions towards the karstic aquifer, the recharge of the aquifer from the combined rainfall, seepage and exploitation as well as the potential alteration in the quality of the aquifer due to the creation of a nearby reservoir. It is shown that despite the somewhat increased seepage of polluted river water towards the aquifer, the quality of the groundwater in the karstic aquifer is not expected to degrade appreciably. However, since the water of the aquifer is used for the supply of neighbouring communities, it is proposed that in the areas where the thickness of the intervening semi-permeable alluvia is small, artificial sealing is installed using either compacted clay or plastic membranes.

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Conséquences sur l'environnement des fuites d'un réser voir de barrage vers un aquifère karstique

Résumé L'article traite le problème des fuites du réservoir d'un barrage qui pourraient se produire vers un aquifère karstique proche et les modifications du régime des eaux souterraines qui en résulteraient, tout en tenant compte des conditions d'alimentation et d'exploitation de cet aquifère. L'analyse montre que malgré l'augmentation des fuites des eaux du fleuve, les quantités concernées ne peuvent aggraver la qualité des eaux souterraines d'une manière notable. Néanmoins, comme les eaux sont utilisées en même temps pour les adductions d'eau potable, il est proposé, dans certains secteurs, où l'épaisseur des alluvions interposées est faible, d'imperméabiliser les berges.

     

Enhancing Light Emission in Interface Engineered Spin‐OLEDs through Spin‐Polarized Injection at High Voltages

The quest for a spin‐polarized organic light‐emitting diode (spin‐OLED) is a common goal in the emerging fields of molecular electronics and spintronics. In this device, two ferromagnetic (FM) electrodes are used to enhance the electroluminescence intensity of the OLED through a magnetic control of the spin polarization of the injected carriers. The major difficulty is that the driving voltage of an OLED device exceeds a few volts, while spin injection in organic materials is only efficient at low voltages. The fabrication of a spin‐OLED that uses a conjugated polymer as bipolar spin collector layer and ferromagnetic electrodes is reported here. Through a careful engineering of the organic/inorganic interfaces, it is succeeded in obtaining a light‐emitting device showing spin‐valve effects at high voltages (up to 14 V). This allows the detection of a magneto‐electroluminescence (MEL) enhancement on the order of a 2.4% at 9 V for the antiparallel (AP) configuration of the magnetic electrodes. This observation provides evidence for the long‐standing fundamental issue of injecting spins from magnetic electrodes into the frontier levels of a molecular semiconductor. The finding opens the way for the design of multifunctional devices coupling the light and the spin degrees of freedom.     

Bis(2‐ethylhexyl) succinate in mixtures with epoxidized soybean oil as bio‐based plasticizers for poly(vinylchloride)

Mixtures of bis(2‐ethylhexyl) succinate and epoxidized soybean oil (ESO) have been evaluated as bio‐based plasticizers for poly(vinylchloride). The rate of absorption of the bioplasticizers and their mixtures in the polymer was fast and, unlike that of petroleum‐derived plasticizers, did not vary significantly with molecular weight. These bio‐derived plasticizers and their mixtures were compatible with the polymer even at high loadings. The succinate was the most volatile and efficient plasticizer, but on heat aging of the polymer compositions, it also had the greatest deleterious effects. Diffusion coefficients and apparent activation energies of formulations containing bioplasticizer mixtures were controlled by the more volatile succinate. Mixtures comprising up to 50 wt% of the succinate yielded acceptably high‐tensile properties after thermal aging as well as better plasticization efficiency than the epoxy bioplasticizer. Although the succinate resulted in inferior volume resistivity of the polymer compositions, improvements were obtained with increasing proportions of the epoxidized derivative in plasticizer mixtures. Melt state viscosity‐shear rate curves of compositions containing dioctyl succinate (DOS) were similar to those made with two of the petroleum‐derived plasticizers, but a DOS/ESO mixture yielded extended non‐Newtonian behavior at low‐shear rates. POLYM. ENG. SCI., 55:634–640, 2015. © 2014 Society of Plastics Engineers