Novel integrated approaches for predicting the compressibility of clay using cascade forward neural networks optimized by swarm- and evolution-based algorithms     

He  Ziguang  Nguyen  Hoang  Vu  Thai Ha  Zhou  Jian  Asteris  Panagiotis G.  Mammou  Anna 《Acta Geotechnica》2022,17(4):1257-1272

Acta Geotechnica - Soft soils are considered as disadvantages in construction, especially in clay layers. It requires many advanced techniques to treat the soft soils before construction, aiming to...  相似文献   

Modelling the Asian summer monsoon using CCAM   总被引：2，自引：1，他引：1  

Kim Chi Nguyen  John L. McGregor 《Climate Dynamics》2009,32(2-3):219-236

A ten-year mean (1989–1998) climatology of the Asian summer monsoon is studied using the CSIRO Conformal-Cubic Atmospheric Model (CCAM) to downscale NCEP reanalyses. The aim of the current study is to validate the model results against previous work on this topic, in order to identify model strengths and weaknesses in simulating the Asian summer monsoon. The model results are compared with available observations and are presented in two parts. In the first part, the mean summer rainfall, maximum and minimum temperatures and winds are compared with the observations. The second part focuses on validation of the monsoon onset. The model captures the mean characteristics such as the cross-equatorial flow of low-level winds over the Indian Ocean and near the Somali coast, rainfall patterns, onset indices, northward movements, active-break and revival periods.  相似文献   

Experimental and numerical behaviour of reinforced mortar plates subjected to accelerated corrosion     

Quang Thanh Nguyen  Sabine Caré  Yves Berthaud  Alain Millard  Frédéric Ragueneau 《国际地质力学数值与分析法杂志》2011,35(10):1141-1159

Most reinforced concrete structures are damaged due to corrosion of reinforcements in concrete. In normal conditions the pH near the reinforcements is around 12–13 which means that steel is in a passive state. But aggressive species, such as chloride ions or carbon dioxide, may penetrate into concrete and promote active corrosion. As a consequence (hydro)oxides are produced leading to degradation of concrete structures. For instance cracking of the concrete is generated due to the pressure induced by rust. In this paper, we study the inception and the propagation of cracking on reinforced mortar plates with rebars located either in the middle or at the corner. Additional experiments have been performed on cylindrical specimens to determine the local effect of rust pressure at the interface rust/mortar. The specimens have been subjected to imposed current density in order to enhance the corrosion and digital image intercorrelation has been used to determine displacement fields. The experiments have been compared to numerical modelling. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Determination of210Pb in volcanic gases and210Pb,226Ra,238U in lavas by non-destructive gamma-ray spectrometry     

Y. Yokoyama  H. Van Nguyen  G. Lambert 《Bulletin of Volcanology》1982,45(3):265-266

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Fault-valve behaviour in optimally oriented shear zones: an example at the Revenge gold mine, Kambalda, Western Australia   总被引：1，自引：0，他引：1  

Phung T Nguyen  Lyal B Harris  Chris McA Powell  Stephen F Cox 《Journal of Structural Geology》1998,20(12):1625-1640

Quartz vein systems developed in and adjacent to shear zones host major gold deposits in the Kambalda region of the Norseman–Wiluna greenstone belt. At the Revenge Mine, two groups of mineralised reverse shear zones formed as conjugate, near-optimally oriented sets during ESE subhorizontal shortening adjacent to a major transpressional shear system. The shear zones developed at temperatures of about 400°C in a transitional brittle–ductile regime. Deformation was associated with high fluid fluxes and involved fault-valve behaviour at transiently near-lithostatic fluid pressures. During progressive evolution of the shear system, early brittle and ductile deformation was overprinted by predominantly brittle deformation. Brittle shear failure was associated with fault dilation and the formation of fault-fill veins, particularly at fault bends and jogs. A transition from predominantly brittle shear failure to combined shear along faults and extension failure adjacent to faults occurred late during shear zone evolution and is interpreted as a response to a progressive decrease in maximum shear stress and a decrease in effective stresses. The formation of subhorizontal stylolites, locally subvertical extension veins and minor normal faults in association with thrust faulting, indicates episodic or transient reorientation of the near-field maximum principal stress from a subhorizontal to a near-vertical attitude during some fault-valve cycles. Local stress re-orientation is interpreted as resulting from near-total shear stress release and overshoot during some rupture events. Previously described fault-valve systems have formed predominantly in severely misoriented faults. The shear systems at Revenge Mine indicate that fault-valve action, and associated fluctuations in shear stress and fluid pressure, can influence the mechanical behaviour of optimally-oriented faults.  相似文献   

A Computer Model for Simulating Water Quality and Quantity in a Wellfield in an Alluvial Aquifer     

Martha W. Gilliland  Quang M. Nguyen 《Ground water》1987,25(2):151-159

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An anisotropic model for estimating of hourly sums of solar radiation on vertical south-facing surfaces     

Nguyen Huong Dien 《Meteorology and Atmospheric Physics》1984,35(1-2):45-54

Summary An empirical study was performed to obtain a new anisotropic model for estimating of individual hourly sums of solar radiation on vertical south-facing surfaces. The procedure consists of correcting statistically the isotropic model by taking into account the anisotropic character of both sky diffuse and ground reflected solar radiation. Based on the data measured at Budapest-Lörinc station a simple correction function was obtained.

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Ein anisotropes Modell zur Bestimmung der Sonnenstrahlung auf vertikale Südwände

Zusammenfassung Es wurde eine empirische Studie zur Entwicklung eines neuen anisotropen Modells zur Bestimmung der individuellen Stundensummen der Sonnenstrahlung auf vertikale Südwände durchgeführt. Das Verfahren besteht in einer statistischen Korrektur des isotropen Modells durch Berücksichtigung des anisotropen Charakters der diffusen Himmelsstrahlung und der vom Boden reflektierten Sonnenstrahlung. Mit in Budapest-Lörinc gemessenen Beobachtungsdaten wurde eine einfache Korrektionsfunktion erhalten.

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1 Visiting scientist from the Socialist Republic of Vietnam.  相似文献   

Velocity model estimation for depth imaging: Comparison of three tomography methods on a 2D real data set     

Soazig Le Bégat  Hervé Chauris †  Vincent Devaux  Sylvain Nguyen  Mark Noble 《Geophysical Prospecting》2004,52(5):427-438

The estimation of velocity models is still crucial in seismic reflection imaging as it controls the quality of the depth‐migrated image, which is the basis of geological interpretation. Among the numerous existing methods for velocity determination, tomographic methods are very attractive for their efficiency and ability to retrieve heterogeneities of the medium. We present three tomographic methods in order to estimate heterogeneous velocity models from 2D prestack PP reflection data: a traveltime tomography in the time‐migrated domain, a traveltime and slope tomography in the non‐migrated time domain, and a slope tomography in the depth‐migrated domain. The first method (traveltime tomography in the time domain) is based on continuous picked events, whereas the two slope tomographic methods, one in the time domain and the other in the depth domain, are based on locally coherent events, with no assumptions about reflector geometry or the unknown velocity field. The purpose of this paper is not to describe in detail the theoretical basis and implementation of the methods, but to apply and compare their output using the same marine real data set. Based on the estimated velocity models, the migrated images and the common‐image gathers from the three processing routes, the relative strengths and weaknesses of the methods are discussed. Finally, similarities are indicated and potential alternative approaches are proposed.  相似文献   

Tectonic wedging along the rear of the offshore Taiwan accretionary prism     

Wu-Cheng Chi  Donald L. Reed  Greg Moore  Tuan Nguyen  Char-Shine Liu  Neil Lundberg 《Tectonophysics》2003,374(3-4):199-217

The structural geometry, kinematics and density structure along the rear of the offshore Taiwan accretionary prism were studied using seismic reflection profiling and gravity modeling. Deformation between the offshore prism and forearc basin at the point of incipient collision, and southward into the region of subduction, has been interpreted as a tectonic wedge, similar to those observed along the front of mountain ranges. This tectonic wedge is bounded by an east-dipping roof thrust and a blind, west-dipping floor thrust. An east-dipping sequence of forearc-basin strata in the hanging wall of the roof thrust reaches a thickness in excess of 4 km near the tip of the interpreted tectonic wedge. Section restoration of the roof sequence yields an estimate of 4 km of shortening, which is small compared with that inferred in the collision area to the north, based on the variation in distance between the apex of the prism and the island arc.Previous studies propose that either high-angle normal faulting or backfolding has exhumed the metamorphic rocks along the eastern flank of the Central Range in the collision zone on land. To better constrain the initial crustal configuration, we tested 350 crustal models to fit the free-air gravity anomaly data in the offshore region to study the density structure along the rear of the accretionary prism in the subduction and initial collision zones before the structures become more complex in the collision zone on land. The gravity anomaly, observed in the region of subduction (20.2°N), can be modeled with the arc basement forming a trenchward-dipping backstop that is overlain by materials with densities in the range of sedimentary rocks. Near the point of incipient collision (20.9°N), however, the free-air gravity anomaly over the rear of the prism is approximately 40 mgal higher, compared with the region of subduction, and requires a significant component of high density crustal rocks within the tectonic wedge. These results suggest that the forearc basement may be deformed along the rear of the prism, associated with the onset of collision, but not in the subduction region further to the south.  相似文献   

Interaction of metamorphism, deformation and exhumation in large convergent orogens   总被引：11，自引：0，他引：11  

R. A. Jamieson  C. Beaumont  M. H. Nguyen  B. Lee 《Journal of Metamorphic Geology》2002,20(1):9-24

Coupled thermal‐mechanical models are used to investigate interactions between metamorphism, deformation and exhumation in large convergent orogens, and the implications of coupling and feedback between these processes for observed structural and metamorphic styles. The models involve subduction of suborogenic mantle lithosphere, large amounts of convergence (≥ 450 km) at 1 cm yr^?1, and a slope‐dependent erosion rate. The model crust is layered with respect to thermal and rheological properties — the upper crust (0–20 km) follows a wet quartzite flow law, with heat production of 2.0 μW m^?3, and the lower crust (20–35 km) follows a modified dry diabase flow law, with heat production of 0.75 μW m^?3. After 45 Myr, the model orogens develop crustal thicknesses of the order of 60 km, with lower crustal temperatures in excess of 700 °C. In some models, an additional increment of weakening is introduced so that the effective viscosity decreases to 10¹⁹ Pa.s at 700 °C in the upper crust and 900 °C in the lower crust. In these models, a narrow zone of outward channel flow develops at the base of the weak upper crustal layer where T≥600 °C. The channel flow zone is characterised by a reversal in velocity direction on the pro‐side of the system, and is driven by a depth‐dependent pressure gradient that is facilitated by the development of a temperature‐dependent low viscosity horizon in the mid‐crust. Different exhumation styles produce contrasting effects on models with channel flow zones. Post‐convergent crustal extension leads to thinning in the orogenic core and a corresponding zone of shortening and thrust‐related exhumation on the flanks. Velocities in the pro‐side channel flow zone are enhanced but the channel itself is not exhumed. In contrast, exhumation resulting from erosion that is focused on the pro‐side flank of the plateau leads to ‘ductile extrusion’ of the channel flow zone. The exhumed channel displays apparent normal‐sense offset at its upper boundary, reverse‐sense offset at its lower boundary, and an ‘inverted’ metamorphic sequence across the zone. The different styles of exhumation produce contrasting peak grade profiles across the model surfaces. However, P–T–t paths in both cases are loops where P_max precedes T_max, typical of regional metamorphism; individual paths are not diagnostic of either the thickening or the exhumation mechanism. Possible natural examples of the channel flow zones produced in these models include the Main Central Thrust zone of the Himalayas and the Muskoka domain of the western Grenville orogen.  相似文献