Shuanhu Wang

Magnetic tuning of the photovoltaic effect in silicon-based Schottky junctions.

A magnetic tuning of the photovoltaic effect is demonstrated for the Schottky junction formed by a ferromagnetic (FM) layer and silicon. Obvious anisotropic magnetic photovoltaic effects (AMV) are gained not only in the FM layer but also in the Si substrate though the latter is non-magnetic. Key factors determining the AMV of Si are identified.

Retrospective case example using a comprehensive suitability index (CSI) for siting the Shisan-Ling power station, China

Abstract The purpose of this paper is to present a retrospective case example of using the rock engineering systems (RES) methodology to site a pumped storage power station in China. With such a siting problem, there are many interacting factors governing both the site and the specific underground position of the powerhouse. The RES approach, based on an interaction matrix for semi-quantitative characterization of the factors and their interactions, is used to develop a comprehensive suitability index (CSI). In this way, the factors governing the geological and rock mechanics related factors are structured and evaluated. Additionally, the complexity of the decision making process is condensed to the CSI values for different potential sites and underground locations, a higher CSI value indicating a more suitable site. The retrospective analysis uses information from the investigations made during the actual site investigation and design work for the Shisan-Ling Power Station, China — which has been constructed. For the first stage, site selection for the overall engineering arrangement, 11 parameters concerned with geology, geomorphology, engineering layout, environment, cost and construction are taken into account. After comparison of site options in conglomerate, andesite and limestone formations, the conglomerate formation proved to be most favorable — because it has the highest CSI value. For the second stage, specifically locating the underground powerhouse, another seven parameters associated with faults, joints, groundwater, etc. are evaluated. As a result, position II proved to be the most favorable location for the powerhouse. Since these were the same conclusions reached during the actual investigations, this retrospective application of the CSI demonstrates the value of the RES methodology and associated indices for assisting in rock engineering design.

Abnormal percolative transport and colossal electroresistance induced by anisotropic strain in (011)-Pr 0.7 (Ca 0.6 Sr 0.4 ) 0.3 MnO 3 / PMN-PT heterostructure

Abnormal percolative transport in inhomogeneous systems has drawn increasing interests due to its deviation from the conventional percolation picture. However, its nature is still ambiguous partly due to the difficulty in obtaining controllable abnormal percolative transport behaviors. Here, we report the first observation of electric-field-controlled abnormal percolative transport in (011)-Pr0.7(Ca0.6Sr0.4)0.3MnO3/0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 heterostructure. By introducing an electric-field-induced in-plane anisotropic strain-field in a phase separated PCSMO film, we stimulate a significant inverse thermal hysteresis (~ -17.5u2005K) and positive colossal electroresistance (~11460%), which is found to be crucially orientation-dependent and completely inconsistent with the well accepted conventional percolation picture. Further investigations reveal that such abnormal inverse hysteresis is strongly related to the preferential formation of ferromagnetic metallic domains caused by in-plane anisotropic strain-field. Meanwhile, it is found that the positive colossal electroresistance should be ascribed to the coactions between the anisotropic strain and the polarization effect from the poling of the substrate which leads to orientation and bias-polarity dependencies for the colossal electroresistance. This work unambiguously evidences the indispensable role of the anisotropic strain-field in driving the abnormal percolative transport and provides a new perspective for well understanding the percolation mechanism in inhomogeneous systems.

Mechanical behavior and microstructural variation of loess under dynamic compaction

The laboratory dynamic compaction test was used to study the effects of dynamic impact loads on the shear strength characteristics of loess. Loess specimens were compacted by different numbers of blows and their shear strengths measured. The experimental results revealed that the shear strength varies in stages with the number of blows. During the initial stage, the shear strength increases with the number of blows. It reaches a peak value and then decreases with the number of blows. To reveal the relationship between this alternation in shear strength and microstructural variation, quantitative microstructural analyses were performed on some tested specimens at different stages of strength evolution. This microstructural study demonstrated that the variation of shear strength is directly related to the alteration of microstructure. It is concluded that the shear strength of loess is basically controlled by its microstructural state. Growing particle size heterogeneity, varying particle orientations and increasing microstructural damage are the main causes of the alternation of shear strength.

Deformation of the central pier of the permanent shiplock, Three Gorges Project, China: an analysis case study

The central pier (CP) is one of the key structures of the permanent shiplock in the Three Gorges Project on the Yangtze River, China. This paper deals with the study of the rock mass deformation of the CP of the second shiplock under various operation conditions. Numerical simulations using the 2-D distinct-element method and 3-D finite-element method are applied to analyze the rock mass deformation. Also, time-series analysis and gray system theory are used to predict the trends of rock displacements based on in situ measured data. The results can be summarized as follows: (1) the main deformation of the rock mass in the CP occurs after excavation completion, while the shiplock is in operation, the dominant displacements mainly occurring on both sides of the northern chamber, developing generally towards the chamber; (2) the horizontal displacement varies with the process of excavation, and is in a steady state after excavation, and during operation of the shiplock the displacement is slightly decreased; (3) the horizontal displacement parallel to the axial line of the shiplock occurs downstream; and (4) the vertical displacement occurs during excavation, and then subsidence with various values takes place in different parts of the CP for different operation conditions.

Assessment of an equivalent porous medium for coupled stress and fluid flow in fractured rock

Abstract The equivalent porous medium (EPM) for coupled stress and fluid flow in fractured rock was assessed. The assessment was focused on the contributions of the seepage-induced force to the systems equilibrium and deformation as well as fluid flux through the fractures, with the special emphasis on the inter-relations among these three aspects. Seepage-induced average stress was calculated for the EPM. And it was proved, with respect to the fluid flow system (FFS) proposed by Long et al. [Long JCS, Remer JC, Wilson CR, Witherspoon PA. Porous medium equivalents for networks of discontinuous fractures. Water Resour Res 1982;18:645–658], that the equivalence of the equilibrium contribution of the seepage-induced force is unconditionally satisfied in the EPM. The equivalence of fluid flux and seepage-induced deformation was evaluated using numerical techniques based on the FFS, in which the seepage-induced deformation was considered as ‘tensile’ deformation under fluid pressures. The numerical simulation results of the two cases suggest that the EPM established in terms of fluid flux based on the FFS guarantees equivalence of coupled stress and fluid flow. Also, the numerical simulation results indicate that the percolation theory can not be applied to a system with fractures of remarkably different size and hydraulic conductivity.

Engineering geomechanical analysis and monitoring-control in design and construction of the Wuqiangxi ship lock slope, China

Abstract The Wuqiangxi Hydroelectric Power Station is located on the Yuan River in Hunan Province, Central China. Phyllitic slates (Pt 1 ) and sandstones (Pt 2 ) occurring on the left bank of the river belong to the Wuqiangxi Formation, the Shangbanxi Group of Pre-Sinian. The slope is intersected by a number of major faults, and rocks are intensely weathered. These factors make the engineering geological situation there unfavorable to the ship lock slope stability. The ship lock slope is threatened under landslides during deep excavation involved in the construction. In order to prevent the excavation of the slope and pouring concrete from failing, a technique of the Monitoring-Control in Design for Geotechnical Engineering (MCGE) was proposed and developed. Consequently, the slope passed smoothly through the excavation and afterward construction stages. This proves that the technique suggested is reasonable and applicable.

Three-dimensional gantt chart based resource-constrained multiple projects scheduling and critical chain identification

Aiming at resources-constrained multiple projects scheduling problem (RCMPSP), a three-dimensional representation is presented through extending the two-dimensional representation of resources-constrained scheduling problem by adding resource dimension to the two-dimensional Gantt chart. It can clearly display the resources consumption of every activity and provide valuable reference for concerning bottleneck resources and solving the resources conflict. In addition, a hybrid algorithm which combined the merits of bidirectional scheduling and parallel schedule generation scheme (PSGS) is proposed to optimize the RCMPSP. Furthermore how to use the presented three-dimensional Gantt chart to represent the schedule and identify critical chain is also described in details. The results of single project with single resource scheduling, single project with multiple resources scheduling, multiple projects with single resource scheduling and multiple projects with multiple resources scheduling show that the proposed approach is effective and explicit for resource constrained project scheduling and critical chain identification.

Particle-size distribution of interlayer shear zone material and its implications in geological processes—a case study in China

Abstract A case study was carried out at the Gaobazhou dam site on the Qingjiang River in Hubei Province, Central China, to investigate the particle-size distribution (PSD) of interlayer shear zone material and its implications in the geological processes. Forty-six disturbed samples were taken at various representative locations within the well-characterized interlayer shear zones at the Gaobazhou dam site. The particle-size distributions of these samples were analyzed, and the mass-based approach is used for fractal scaling of the particle-size distribution curves. It is shown that all curves on the log–log scale can be approximated by two intersecting lines. Thus, each curve can be quantified by α 1 , α 2 , P s , and r s , which respectively correspond to the slopes of the two lines and the coordinates of the point of intersection. α 1 and α 2 can be replaced by fractal dimensions D 1 and D 2 . The statistical analysis results reveal that Delta (= D 2 − D 1 ) and P s are closely related to D 1 . Therefore, only D 1 and r s are used to characterize each curve. It is illustrated that 47 specimens are clustered into five groups with respect to r s and D 1 . Accordingly, five categories of particle-size distributions are identified. It is found that the D 1 and r s values of a sample can reflect the geological processes of the interlayer shear zone. The larger the value of D 1 , the higher the degree of interlayer shear experienced. The value of r s implies the degree of subsequent secondary geological processes, but in a rather complex way due to the differences in intensity of interlayer shear undergone. Based on this, the geological evolution processes of the interlayer shear zones are postulated, and the current status can be defined through fractal scaling of the particle-size distribution of disturbed samples.

Joint effect of gate bias and light illumination on metallic LaAlO3/SrTiO3 interface

We presented a systemic investigation on the joint effect of gate bias and light illumination on a metallic LaAlO3/SrTiO3 interface in the temperature range from 15u2009K to 300u2009K. We showed that the photo excitation significantly enhanced the gating effect for the metallic two-dimensional electron gas. However, its effect is strongly temperature dependent; it is strong at low and high temperatures, and weak in the intermediate temperature range. There are evidences that the amplified gating effect stemmed from enhanced carrier depletion while the Hall mobility remains nearly unaffected. Acceleration of the gating process, together with a training effect marked by a strong dependence on gating history of the getting effect, is induced by repeating the electric cycling, indicating atomic reconfiguration due to oxygen migration and the memory of the migration paths.We presented a systemic investigation on the joint effect of gate bias and light illumination on a metallic LaAlO3/SrTiO3 interface in the temperature range from 15u2009K to 300u2009K. We showed that the photo excitation significantly enhanced the gating effect for the metallic two-dimensional electron gas. However, its effect is strongly temperature dependent; it is strong at low and high temperatures, and weak in the intermediate temperature range. There are evidences that the amplified gating effect stemmed from enhanced carrier depletion while the Hall mobility remains nearly unaffected. Acceleration of the gating process, together with a training effect marked by a strong dependence on gating history of the getting effect, is induced by repeating the electric cycling, indicating atomic reconfiguration due to oxygen migration and the memory of the migration paths.