Search

The mechanical behaviour of clayey loess is strongly affected by the soil structure, but although anisotropy has been identified in loess by some, the anisotropy of small-strain behaviour is rarely reported. This paper presents an experimental study on the inherent and stress-induced small-strain shear stiffness anisotropy of a clayey loess from China. Both undisturbed and reconstituted specimens were tested with bender elements under isotropic compression and shearing conditions. Under an isotropic stress state, an inherent anisotropy was found for undisturbed specimens, while the reconstituted specimens prepared by moist tamping behaved isotropically. During shearing, the ratio of horizontal to vertical shear moduli of the undisturbed specimens decreased due to both an increase of stress anisotropy and the destruction of the intact structure. In contrast, the stiffness ratio of the reconstituted specimens only decreased due to stress anisotropy and it became more anisotropic at the critical state. This study reveals the influence of intact structure and inherent anisotropy on the behaviour of loess soils, which cannot be reproduced by compaction, thus highlighting the importance of characterising the undisturbed loess.

Three-dimensional numerical simulations for a solar chimney power plant (SCPP) and wind supercharged solar chimney power plant (WSSCPP) based on the Spanish prototype using the solar ray-tracing algorithm were performed to study the shadow effect of the chimney. The area of the shadow region increases with an increase in the incident angle of the solar rays. A parametric study was performed by varying the incident angle from 0° to 30°. The temperature and velocity distributions at different incident angles were analyzed. In addition, we investigated the chimney shadow effect in several comprehensive SCPP systems. The findings show that the turbine shaft powers of the SCPP and WSSCPP were reduced by 22.4% and 13.7%, respectively, when the incident angle increased from 0° to 30°. In conclusion, it is important to consider the chimney shadow effect when estimating the performance in the design and cost analysis of SCPP systems.

A series of aromatic sulfonic acids is synthesized by subjecting arenes and NaHSO4·H2O to high-speed ball milling in the presence of P2O5. It is suggested the aromatic sulfonation occurs via in situ generated H2SO4 to give aromatic sulfonic acids. In some cases, formation of diaryl sulfones was observed.

Based on the lifting design method of the axial flow hydraulic turbine and axial-flow pump impeller, an air turbine design method considering the optimal turbine pressure drop ratio for the solar chimney power plant was presented in this paper. Numerical simulations for the Spanish prototype system incorporating the turbine impeller were conducted to investigate the feasibility of the present turbine design method on the improvement of the system output performance. Furthermore, the influence of the solar radiation on the turbine performance was investigated. The results indicates that the turbine performance can be improved by using the proposed design method. The maximum turbine power output is 53.49 kW, 30.46% higher than that of the Spanish prototype and the turbine is less sensitive to rotational speed. In addition, the turbine high-performance rotational speed range is larger under higher solar radiation.

The existence and failures of silty sand have been reported worldwide, and the behaviour of sand–silt mixtures at small to large strains has been intensively studied. Owing to the relatively low stress level achieved in laboratory testing, no unifying framework has yet been proposed for sand–silt mixtures. In the presented work, a crushable sand, made of pumice, was used as host sand so as to reach a unique normal compression line under pressures easily attainable in the laboratory. The sand was combined with non-plastic fines in proportions varying between 0 and 100%, and tested in compression and shearing with associated bender element testing for small-strain stiffness measurements. The unique relationship between pressure and volume on the normal compression line allowed for the normalisation of the data in a way that highlights the effects of fines irrespective of the density. It was found that once the effects of the fines on the index properties and compressibility have been cancelled, by normalising for volume, the behaviour of the sand–silt mixtures can be characterised as unique.

By setting up the unpowered wind pressure wheel at the chimney top, this paper puts forward the model of “wind supercharged solar chimney power plant (WS-SCPP)". Based on the prototype Spanish solar chimney power plant (SCPP), the physical, mathematical models are built, the performance of WS-SCPP and SCPP are compared and the relationship between chimney height increment and supercharging effect is discussed. The results show that: with the help of unpowered wind pressure wheel, the performance of WS-SCPP improves greatly. At the same turbine rotational speed, the shaft power of WS-SCPP is always higher than that of SCPP. When the speed is 100 rpm, the shaft power of SCPP increases from 37.8kw to 57.03kw, with an increase of 50.9%. The net income and NPV of WS-SCPP are always higher than those of SCPP. The lowest electricity selling price is significantly lower than that of SCPP, with a decrease of 20.1%. When the chimney height of SCPP is increased by at least 80 m, the performance is comparable to WS-SCPP. Wind supercharging technology is one of the effective ways to improve the efficiency and commercial application of SCPP.

A series of oedometer tests was carried out on natural loess and artificial soils. The loess soils were retrieved from sandy loess, silty loess and clayey loess zones within the Chinese Loess Plateau, as well as Yili area, Xinjiang Province outside the Chinese Loess Plateau. The results show clear influences of grading on soil compressibility. With the finer particle content increasing in loess, the compression paths turn from slightly upwards concave to upwards convex. The collapse index Ic defined in this study increases with the increasing Cu and decreases with the increasing D60. Locations of the soil normal consolidation lines in v–log σ′v plane are also influenced by soil grading characterised by the D60 and Cu. The intact clayey loess has more significant structure effect than the intact silty loess. Compared with the silty and clayey loess, the intact sandy loess has negligible structure effect on soil compressibility. For a given sampling site, deep loess has a higher yielding stress point and is more difficult to compress to the intrinsic compression line than shallow loess, revealing the effect of stress history on the soil compressibility.

3-D triple-level cell (3-D TLC) NAND flash has high storage density and capacity, but degrading data reliability due to high raw bit error rates induced by a certain number of program/erase cycles. To guarantee data reliability, low-density parity-check (LDPC) codes are selected as the error correction codes in modern flash memories because of strong error correction capability. However, directly adopting LDPC codes induces high decoding latency due to iterative updating of log-likelihood ratio (LLR) information in the decoding process. Increasing LLR information accuracy can greatly improve decoding performance. In this paper, we propose EMAL: using error modes aware LDPC codes for further enhancing the decoding performance of 3-D TLC NAND flash. We first obtain 3-D TLC error modes based on an FPGA testing platform, and then exploit the error modes to optimize LLR information and enable the decoding to converge at a high speed. The simulation results show that the decoding performance is significantly improved, resulting in reduced bit error rates and decoding latency.

Under dual crisis of energy and freshwater, solar chimney technology has been widely applied in freshwater production in recent years. According to different access to freshwater, the research progress of the coupling of solar chimney with other technologies such as solar desalination technology, humidification and humidification desalination technology, as well as integrated systems that obtain freshwater output from ambient air were summarized respectively. The integrated solar chimney system can realize multi-target production of electricity and freshwater, and improve the comprehensive utilization of solar energy, which provides new possibility for the site selection and small-scale construction of solar chimney power plant in the future. It has certain practical significance and is conducive to the promotion and application of solar chimney technology. Keywords: Solar chimney, Desalination, Multi-target, Freshwater output

This paper aims to optimize the design of individualized classroom teaching for mobile English learning in colleges, and find a scientific and effective English teaching mode and strategy for mobile learning. For this purpose, the application and evolution of mobile learning in English teaching was investigated, and the concept and theoretical bases of mobile learning were introduced in details. Through literature review, questionnaire survey and face-to-face interview, the status of mobile English learning among college students was analysed qualitatively and quantitatively from three dimensions, namely, the mobile device, learning resource and learning attitude. Then, several strategies for individualized teaching reform were presented through status analysis. Finally, the application of individualized mobile English learning was demonstrated through case studies on public platforms like Weibo and WeChat. The research findings shed new light on the individualized English learning among college students and lay a scientific basis for the application of mobile learning in college English education.

In this study, the physical and mathematical models of wind supercharging solar chimney power plant combined with seawater desalination by indirect condensation freshwater production (WSSCPPSDIC) were proposed. The numerical simulation was carried out for analyzing the flow field characteristics of WSSCPPSDIC. Subsequently, a comparison of solar chimney power plant (SCPP), solar chimney power plant combined with seawater desalination by indirect condensation freshwater production (SCPPSDIC) and WSSCPPSDIC was conducted in different rotational speed. It was found that the ingenious and special condenser combined in the integrated system could preheat the seawater and realize the full utilization of the latent heat of condensation released by water vapor. Besides, the negative pressure generated by the wind supercharging system installed at chimney exit remarkably increased the electricity production. Generally, WSSCPPSDIC could effectively improve the freshwater output and the solar energy comprehensive utilization efficiency, specifically 9.805 ton/h and 16.73%.

Rainfall-induced landslides are major natural hazards that are inherently inter-disciplinary crossing various fields (from geology to hydrology) and scales (particle level to catchment scale and beyond). Comparatively, very few studies on landslides have been conducted at the particle level with most research focusing on particle breakage or the effect of particle size and shape on the macro-scale and particle contact behavior. Limited evidence suggests that soils under shear undergo changes not only of size but also of shape and surface roughness. However, the particle morphology descriptors used are frequently qualitative so that information on how the soil particles are damaged during landsliding remains incomplete. This paper uses quantitative particle morphology descriptors, namely particle size, shape, and particle surface roughness to investigate particle damage during landslide-induced shearing. A series of ring shear tests were conducted to simulate landslide movement in completely decomposed volcanic rocks (CDV), a typical soil in Hong Kong that was retrieved from a debris flow. Particle size, shape, and surface roughness were analyzed on original CDV particles and on samples subjected to ring shear testing. Owing to the crushable nature of the soil, particle breakage was the key factor controlling particle morphology, with the results revealing an intricate dependency of shape and surface roughness on particle size. Shearing enhanced the bimodal gradation of the soil, with the larger grains more rounded and smoother and the resulting fines with a more irregular shape. This may be attributed to a combination of chipping and abrasion of the coarser particles. Further research is needed to ascertain the effect of such particle morphology changes to landslide movement.

Ambition is often considered to have a dualistic nature, associated with both being a driver of success and a cause of personal downfalls. However, there is little understanding of what factors may lead to which outcomes. Drawing upon socioanalytic theory, we hypothesize and test a mediation model in which ambition impacts transformational leadership via perceptions of agency. We also utilize the channeling hypothesis to argue that impulsivity acts as a boundary condition for the positive influence of ambition on perceptions of agency. Using multisource data from 333 members of seven student Greek organizations, we found strong support for the positive indirect effect of self-rated ambition on peer-rated transformational leadership through peer-rated agency. We also found that impulsivity attenuated this positive effect such that ambition could be translated into peer-rated agency and, in turn, peer-rated transformational leadership, only when impulsivity was low. Our findings illustrate theoretical and practical implications for ambition that influences leadership outcomes.

Based on the basic size and operating environment of the prototype solar chimney power plant(SCPP) in Spain, a series of simulation models were built in order to study the performance of the unpowered wind pressure wheel which is installed at the top of the wind supercharged solar chimney power plant (WS-SCPP). The influence of the structural parameters of the wind pressure wheel on the system performance was studied. The results show that: with the increase of H-type vertical axis blade installation angle, the negative pressure acting on the chimney outlet and shaft power of the system both increase but then decrease. When the installation angle is 3°, the negative pressure value at the bottom of the wheel is the largest, the negative pressure increases by 3. 72Pa, the system shaft power increases by 4. 54kW. When using asymmetric airfoils and concave-in configuration, the negative pressure produced by the wheel increases by 1. 3Pa, the system shaft power increases by 0.81kW. When the airfoils use concave-out configuration, the negative pressure at the bottom of the wheel is increased by 5. 6Pa, the system shaft power is increased by 4. 95kW. When the spiral blade is adopted and the helicity is 72°, the negative pressure produced by the wheel increases by 14.61Pa, the system shaft power increases by 14. 95kW. The structural optimization of the unpowered wind pressure wheel can greatly enhance the negative pressure at the chimney outlet to improve the chimney effect, which is a great way to significantly enhance the ability of power generation of WS-SCPP and make the commercial application of SCPP more possible.

The aluminized layer of 321 stainless steel was treated by laser shock processing (LSP). The effects of constituent distribution and microstructure change of the aluminized layer in 321 stainless steel on creep performance at high temperature were investigated. SEM and EDS results reveal that aluminized coating is mainly composed of an Al2O3 outer layer, the transition layer of the Fe-Al phase, and the diffusion layer. Additionally, LSP conducted on coating surface not only improves the density of the layer structure, resulting in an increment on the bonding strength of both infiltration layer and substrate, but also leaves higher residual compressive stress in the aluminized layer which improves its creep life effectively. Experimental results indicate that the microhardness of the laser-shocked region is improved strongly by the refined grains and the reconstruction of microstructures. Meanwhile, the roughness and microhardness of aluminized steel are found to increase with the laser impact times. On the other hand, the intermetallic layers, whose microstructure is stable enough to inhibit crack initiation, reinforce strength greatly. The anticreep life of aluminized sample with three times LSP was increased by 232.1% as compared to aluminized steel, which could attribute to the increased dislocation density in the peened sample as well as the decrease of creep voids in size and density.

The thermomechanical fatigue (TMF) behaviors of spray-deposited SiCp-reinforced Al-Si alloy were investigated in terms of the size of Si particles and the Si content. Thermomechanical fatigue experiments were conducted in the temperature range of 150-400°C. The cyclic response behavior indicated that the continuous cyclic softening was exhibited for all materials, and the increase in SiC particles size and Si content aggravated the softening degree, which was attributed to dislocation generation due to differential thermal contraction at the Al matrix/Si phase interface or Al matrix/SiC particle interface. Meanwhile, the TMF life and stress amplitude of SiCp/Al-7Si composites were greater than those of Al-7Si alloy, and increased with the increasing SiC particle size, which was associated with “load sharing” of the direct strengthening mechanism. The stress amplitude of 4.5μmSiCp/Al-Si composite increased as the Si content increased; however, the influence of Si content on the TMF life was not so significant. The TMF failure mechanism revealed that the crack mainly initiated at the agglomeration of small-particulate SiC and the breakage of large-particulate SiC, and the broken primary Si and the exfoliated eutectic Si accelerated the crack propagation.

Based on the mathematical model of the wind supercharged solar chimney power plant combined with seawater desalination (WSSCPPCSD), the velocity field characteristics of basic WSSCPPCSD were analyzed through three-dimensional numerical simulation. To investigate the influence of different structural parameters of system performance, systems with turbines of different blade numbers, installation angles and relative radial clearances, with guide cone or guide vane were also simulated. Unsteady numerical simulations of H-type wind pressure ventilator with different wind wheel blade installation angles were conducted, as well as another helix-type wind pressure ventilator. The results show that the increase of turbine blade number could lead to a reduced freshwater productivity, and the rotational speed corresponding to maximum turbine shaft power shifts in the direction of lower speed. Besides, with the increase of blade installation angle, both the freshwater productivity and the turbine shaft power increase first and then decrease. As the radial clearance of turbine blades increases, the system freshwater productivity increases and the noise decreases, and the turbine shaft power has a maximum value when the relative radial clearance is 2%. The addition of guide cone and guide vane can effectively improve the flow field. As for the wind pressure ventilator, system freshwater productivity and shaft power both increases first and then drops with the increase of wind wheel blade installation angle. In addition, the helix-type wind wheel can improve the self-starting performance of the wind pressure ventilator and decrease the fluctuation of blade torque at the same time, so as to improve the stability.

In this study, a model of wind supercharged solar chimney power plant combined with seawater desalination (WSSCPPCSD) was proposed. The integrated system was divided into wind pressure ventilator and solar chimney power generation system for numerical simulation. Three-dimensional unsteady state numerical investigation on wind pressure ventilator was carried out as well as steady state numerical study on the solar chimney power generation system. The flow field characteristics and performance parameters of the two subsystems were analyzed. Subsequently, the comparison between solar chimney power plant (SCPP), solar chimney power plant combined with seawater desalination (SCPPCSD) and WSSCPPCSD was conducted. The results show that, although SCPPCSD can greatly improve the solar energy comprehensive utilization, the power generation is reduced. The wind pressure ventilator proposed in this paper could not only significantly increase the power generation but also increase the freshwater production by providing a negative pressure of 64.5 Pa at the chimney outlet. It was found that at 800 W/m2, an increase in power output of about 14.7 kW and increase in hourly freshwater production of 30 g/h were obtained.