Sprayed Concrete Lining (SCL) or the New Austrian Tunnelling Method (NATM) has had limited exposure in Singapore. Previously this has been restricted to excavations of less than 6 metres inside diameter in the boulder clay and decomposed granite. For the North East Line Project (NELP) a section of SCL tunnel was constructed as part of the tunnelling works on Contract 710. This paper describes the design, planning, and construction issues of twin 8.4-metre inside diameter crossover tunnels spaced less than one diameter apart constructed in the Jurong Formation. In addition, the construction of a SCL tunnel in the Old Alluvium, is also described. This tunnel is an advance tunnel for the future Deep Tunnel Sewage Scheme (DTSS) and is being constructed as part of the NELP Contract 705 Works. Details of the Jurong Formation and Old Alluvium are given together with their geotechnical characteristics, which played a major role in the selection of temporary support methods used and the behaviour of the ground during tunnelling. The planning and design issues concentrate on aspects to ensure overall integrity and stability of both SCL projects. The success of various construction techniques utilised to construct the tunnels safely is discussed and a summary of the ground movements is presented. 相似文献
Variability in water cycles driven by climate change is considered likely to impact rice production in the near future. Rice
is the main staple food for the population in the lower Mekong Basin and the demand for food is expected to grow due to increase
in population. This paper examines the impact of climate change on rice production in the lower Mekong Basin, evaluates some
widely used adaptation options, and analyses their implications for overall food security by 2050. Climate change data used
in the study are the future climate projection for two IPCC SRES scenarios, A2 and B2, based on ECHAM4 General Circulation
Model downscaled to the Mekong region using the PRECIS (Providing Regional Climates for Impact Studies) system. In general,
the results suggest that yield of rainfed rice may increase significantly in the upper part of the basin in Laos and Thailand
and may decrease in the lower part of the basin in Cambodia and Vietnam. Irrigated rice may not be affected by climate change
if increased irrigation requirements are met. Negative impact on the yield of rainfed rice can be offset and net increase
in yield can be achieved by applying widely used adaptation options such as changing planting date, supplementary irrigation
and increased fertilizer input. Analysis of the projected production, considering population growth by 2050, suggests that
food security of the basin is unlikely to be threatened by the increased population and climate change, excluding extreme
events such as sea level rise and cyclones. 相似文献
For the nonlinear dynamic analyses of complex mechanical components, it is necessary to apply efficient modeling framework to reduce computational burden. The accurate surrogate model for approximating the nonlinear responses of several failures is a vital issue to provide robust and safe design conditions in complex engineering applications. In this paper, two different Modified multi-extremum Response Surface basis Models (MRSM) are proposed for dynamic nonlinear responses of failure capacities for turbine blisk responses. The proposed MRSM is established using two regression processes including regressed the input variables by linear or exponential basis functions in first calibrating phase and regressed the second-order polynomial basis function using inputs data provided by first stage in second calibrating procedure. A sensitivity analysis using MRSM is proposed to consider the variation of input variables on the nonlinear responses. In the sensitivity analysis procedure, the effects of input variables are evaluated using the calibrating results given from the first regressed process. To evaluate the performance of the proposed MRSM, three multi-extremum failure modes including radial deformation of compressor blisk, maximum strain, and stress of compressor blade and disk are considered. the prediction of MRSM of nonlinear responses for Thermal-fluid–structure system with dynamical nonlinear finite-element analyses is compared with response surface method (RSM) and artificial neural network (ANN). The predicted results of modeling approaches showed that the sensitivity analysis based on MRSM accurately provided the effective degree for input variables. The gas temperature has the highest effects on nonlinear responses of turbine blisk which is followed by angular speed and material density. The MRSM combined with basic exponential function performs better than other models, while the MRSM coupled with linear function is more accurate than ANN and RSM. The proposed MRSM models have illustrated the accurate and efficient framework for approximating dynamic structural analysis of complex components.
Hemolysis is known to cause acute kidney injury (AKI). The iron regulatory hormone hepcidin, produced by renal distal tubules, is suggested to exert a renoprotective role during this pathology. We aimed to elucidate the molecular mechanisms of renal hepcidin synthesis and its protection against hemoglobin-induced AKI. In contrast to known hepatic hepcidin induction, incubation of mouse cortical collecting duct (mCCDcl1) cells with IL-6 or LPS did not induce Hamp1 mRNA expression, whereas iron (FeS) and hemin significantly induced hepcidin synthesis (p < 0.05). Moreover, iron/heme-mediated hepcidin induction in mCCDcl1 cells was caused by the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway, as indicated by increased nuclear Nrf2 translocation and induced expression of Nrf2 downstream targets GCLM (p < 0.001), NQO1 (p < 0.001), and TXNRD1 (p < 0.005), which could be prevented by the known Nrf2 inhibitor trigonelline. Newly created inducible kidney-specific hepcidin KO mice demonstrated a significant reduction in renal Hamp1 mRNA expression. Phenylhydrazine (PHZ)-induced hemolysis caused renal iron loading and oxidative stress in both wildtype (Wt) and KO mice. PHZ treatment in Wt induced inflammatory markers (IL-6, TNFα) but not Hamp1. However, since PHZ treatment also significantly reduced systemic hepcidin levels in both Wt and KO mice (both p < 0.001), a dissection between the roles of systemic and renal hepcidin could not be made. Combined, the results of our study indicate that there are kidney-specific mechanisms in hepcidin regulation, as indicated by the dominant role of iron and not inflammation as an inducer of renal hepcidin, but also emphasize the complex interplay of various iron regulatory mechanisms during AKI on a local and systemic level. 相似文献
Gd_2O_3:Er~(3+) nanophosphors were fabricated by the combustion method in presence of Na_2 ethylene diamine tetra acetic acid(EDTA-Na_2) as fuel at not high temperature(≤350℃) within a very short time of 5 min.The added concentration of Er~(3+)ions in Gd_2O_3 matrix was changed from 0.5 mol% to 5.0 mol%.The X-ray diffraction pattern of samples indicates the monoclinic structure of Gd_2O_3:Er3+.The morphology and chemical composition analysis of the Gd_2O_3:Er~(3+) samples are characterized by a field emission scanning electron microscope(FESEM) and a Fourier-transform infrared spectrometer(FTIR).The photoluminescence(PL),photo luminescence excitation(PLE) and upconversion(UC) at room temperature of the prepared materials with different concentrations of Er~(3+) were investigated.The PL of Gd_2O_3:Er~(3+)nanomaterials are shown in visible at 545,594,623,648,688 nm under excitation at 275 nm.The emission bands from transitions of Er~(3+) from ~2P_(3/2) to ~4F_(9/2) are observed,UC luminescent spectra of the Gd_2O_3:Er~(3+)/silica nanocomposites under 976 nm excitation show the bands at 548 and 670 nm.The influence of excitation power at 980 nm for transitions were measured and calculated.The results indicate that the upconversion process of Gd_2O_3:Er~(3+)/silica is two photons absorption mechanism.The low temperature dependence of UC luminescent intensities of the main bands of Gd_2O_3:Er~(3+)was investigated towards development of a nanotemperature sensor in the range of 10-300 K. 相似文献
In this research, a novel pH and temperature-sensitive biodegradable oligomer serin-b-poly(lactide)-b-poly (ethylene glycol)-b-poly(lactide)-b- oligomer serin (OS-PLA–PEG–PLA-OS) pentablock copolymer was synthesized with modification of serine to sulfonamide group. The properties of the different pentablock copolymer structures were detail characterized. The copolymer solution easily flowed at high pH and changed to gel state at physiological conditions (37°C, pH 7.4). The sol to gel behavior of these block copolymer solutions were controllable by tuning the length of PEG segment, PLA/PEG block ratio, the molecular weight and the concentration of the pentablock copolymer. The in vivo gelation of the copolymer solution was investigated. The stable gel was formed after injection into the back of the adult male Mus musculus Swiss Albino mice. The degradation process was observed after 6 weeks and showed that the hydrogel depot was bioresorbable without any detection of inflammation sign. The results in this study suggest that the OS-PLA–PEG–PLA-OS pentablock copolymer has the potential application as an injectable delivery vehicle for therapeutic drugs that easily denatured at low-pH condition. 相似文献
Information Systems Frontiers - Interactions with conversational agents (CAs) become increasingly common in our daily life. While research on human-CA interactions provides insights into the role... 相似文献
This paper investigates the feasibility to achieve grinding-hardening in a plunge cylindrical grinding process. To understand the mechanisms, a temperature-dependent finite element heat transfer model incorporating a triangular moving heat source was developed to describe the temperature field, thus to predict the thickness of the grinding-hardened layer. The analysis carried out included the variation effect of depth of cut caused by the change in wheel-workpiece engagement. The model was applied on quenchable steel 1045 and the analysis was verified experimentally. It was shown that the heating cycle in plunge cylindrical grinding is the result of consecutive heating and cooling processes, varying from location to location in a workpiece. The ratio of the workpiece speed to the infeed rate plays an important role in the heat treatment cycle. 相似文献