In recent decades, colleagues working in the Discipline of Geological Resources and Geological Engineering at Central South University made significant progress in theoretic study and application of geophysics, ore deposit and shale gas geology, 3D predictive modeling of concealed resources, and geological engineering. In geophysics, world-class progress was achieved in the development, data processing, equipment, and scientific survey of electromagnetic method in onshore and offshore environments and the tectonic evolution of the Tibetan Plateau. Especially, advanced wide-field electromagnetic exploration method and equipment as a highlight technique won the first prize of National Science and Technology Invention of China. In ore geology, progressive and complex characteristics of most nonferrous ore deposits and the geodynamic relationship between crust-mantle reaction and mineralization in south China were revealed. Progressive metallogenic models of certain typical ore deposits were established based on the study of fluid inclusion and geochemistry. According to characteristics of complex metallogenic system of polygenetic ore deposit, key ore-controlling factors were found and summarized. The investigation on unconventional resources advanced China’s shale gas resource evaluation system. In 3D predictive modelling of metallogenic, a large-scale location prediction model was established for exploration of crisis mines and concealed ore deposits. Our developed 3D predictive modeling techniques for concealed orebodies were widely used to explore deep mineral resources in China. In geological engineering area, the key technologies for deep drilling into complex formations were developed. Especially the drilling fluid and tools were utilized in the fieldwork. The rock and soil mechanics analysis method and anchor technologies were also established and applied to engineering practice.
The paramount importance and multi-purpose applications of underlying topography over forest areas have gained widespread recognition over recent decades, bringing about a variety of experimental studies on accurate underlying topography mapping. The highly spatial and temporal dynamics of forest scenarios makes traditional measuring techniques difficult to construct the precise underlying topography surface. Microwave remote sensing has been demonstrated as a promising technique to retrieve the underlying topography over large areas within a limited period, including synthetic aperture radar interferometry (InSAR), polarimetric InSAR (PolInSAR) and tomographic SAR (TomoSAR). In this paper, firstly, the main principle of digital elevation model (DEM) generation by InSAR and SAR data acquisition over forest area are introduced. Following that, several methods of underlying topography extraction based on InSAR, PolInSAR, and TomoSAR are introduced and analyzed, as well as their applications and performance are discussed afterwards. Finally, four aspects of challenge are highlighted, including SAR data acquisition, error compensation and correction, scattering model reconstruction and solution strategy of multi-source data, which needs to be further addressed for robust underlying topography estimation.
As the application of energy-absorption structure reaches an unprecedented scale in both academia and industry, a reflection upon the state-of-the-art developments in the crashworthiness design and structural optimization, becomes vital for successfully shaping the future energy-absorption structure. Physical impacting test and numerical simulation are the main methods to study the crashworthiness of railway vehicles at present. The end collision deformation area of the train can generally be divided into two kinds of structural design forms: integral absorbing structure design form and specific energy absorbing structure design form, and different energy-absorption structures introduced in this article can be equipped on different railway vehicles, so as to meet the balance of crashworthiness and economy. In pursuit of improving the capacity of energy dissipation in energy-absorption structures, studies are increasingly investigating multistage energy absorption systems, searching breakthrough when the energy dissipation capacity of the energy-absorption structure reaches its limit. In order to minimize injuries, a self-protective posture for occupants is also studied. Despite the abundance of energy-absorption structure research methods to-date, the problems of analysis and prediction during impact are still scarce, which is constituting one of many key challenges for the future.
This paper reviews the current status of investigation on snow accumulation on the bogies of high-speed trains (HSTs) running in snowy region. First, the background of the snow issue occurring to the HST and the contra-measures for the snow issue proposed in the past decades are provided by reviewing previous studies. Next, the methodology for investigating the snow issue developed by High-Speed Train Research Center of Central South University is introduced, including the numerical simulation research platform and the experimental devices for two-phase flow wind tunnel tests. Then, effective anti-snow flow control schemes for guiding the underbody airflow and their impact on the motion and accretion of snow in the installation region of the bogies are presented. Finally, the remaining investigating challenge for the snow issue of HST and the future research with respect to the challenge are provided from an engineering application viewpoint.
Serviceability and running safety of the high-speed train on/through a bridge are of major concern in China. Due to the uncertainty chain of the train dynamic analysis in crosswinds originating mainly from the aerodynamic assessment, this paper primarily reviews five meaningful progresses on the aerodynamics of the train-bridge system done by Wind Tunnel Laboratory of Central South University in the past several years. Firstly, the flow around the train and the uncertainty origin of the aerodynamic assessment are described from the fluid mechanism point of view. After a brief introduction of the current aerodynamic assessment methods with their strengths and weaknesses, a new-developed TRAIN-INFRASTRUCTURE rig with the maximum launch speed of 35 m/s is introduced. Then, several benchmark studies are presented, including the statistic results of the characterized geometry parameters of the currently utilized bridge-decks, the aerodynamics of the train, and the aerodynamics of the flat box/truss bridge-decks. Upon compared with the foregoing mentioned benchmarks, this paper highlights the aerodynamic interference of the train-bridge system associated with its physical natures. Finally, a porosity- and orientation-adjustable novel wind barrier with its effects on the aerodynamics of the train-bridge system is discussed.
Methanol is regarded as an important liquid fuel for hydrogen storage, transportation, and in-situ generation due to its convenient conveyance, high energy density, and low conversion temperature. In this work, an overview of state-of-the-art investigations on methanol reforming is critically summarized, including the detailed introduction of methanol conversion pathways from the perspective of fuel cell applications, various advanced materials design for catalytic methanol conversion, as well as the development of steam methanol reformers. For the section of utilization pathways, reactions such as steam reforming of methanol, partial oxidation of methanol, oxidative steam reforming of methanol, and sorption-enhanced steam methanol reforming were elaborated; For the catalyst section, the strategies to enhance the catalytic activity and other comprehensive performances were summarized; For the reactor section, the newly designed steam methanol reformers were thoroughly described. This review will benefit researchers from both fundamental research and fuel cell applications in the field of catalyzing methanol to hydrogen.
Perovskite solar cells (PSCs) have emerged as one of the most promising candidates for photovoltaic applications. Low-cost, low-temperature solution processes including coating and printing techniques makes PSCs promising for the greatly potential commercialization due to the scalability and compatibility with large-scale, roll-to-roll manufacturing processes. In this review, we focus on the solution deposition of charge transport layers and perovskite absorption layer in both mesoporous and planar structural PSC devices. Furthermore, the most recent design strategies via solution deposition are presented as well, which have been explored to enlarge the active area, enhance the crystallization and passivate the defects, leading to the performance improvement of PSC devices.
Additive manufacturing is a new emerging technology which is ideal for low-to-zero waste production, and it is considered to be a green and clean process that has the potential to lower the cost and energy consumption of production. However, the cost of the feedstock for additive manufacturing and the additive manufactured parts is usually very high, which hinders the further application of additive manufacturing, especially for the metal additive manufacturing. The concept of circular metal additive manufacturing involves the recycling of the metal feedstock and the additive manufactured parts leading to the truly zero waste production and the most energy saving. This paper reviews the technologies that help the formation of a circular metal additive manufacturing through recycling of the feedstocks and the damaged metal parts. Reactive metals, such as titanium, tend to be contaminated easily during handling and production. Recycling of the titanium for achieving a circular titanium additive manufacturing is reviewed in detail.
For developing new binder phase with high performance, Co-Ni-Fe alloy was used as binder in cemented carbides. The mechanical properties of WC-CoNiFe and WC-Co cemented carbides with different grain sizes were studied. The results show that the reprecipitation of WC-CoNiFe is inhibited compared with that of WC-Co during sintering process, and the grains in WC-CoNiFe cemented carbides are more of smooth shape, resulting in a slightly lower hardness and higher transverse rupture strength. With the increase of the grain size, the hardness of the two cemented carbides decreases, and the transverse rupture strength increases. However, the slope values of K in Hall-Petch relationship are higher in WC-CoNiFe than those in WC-Co, indicating the high toughness of medium entropy alloy Co-Ni-Fe.
The ultra-high strength Cu-20Ni-20Mn alloy was prepared by vacuum melting and its mechanical property and corrosion behavior were investigated. After thermomechanical treatment, the alloy exhibited an ultra-high tensile strength of 1204 MPa and the applicable elongation of up to 6.2%. With the increasing exposure time in 3.5% NaCl solution, the corrosion current of the alloy decreased, while the polarization resistance and the charge-transfer resistance of the corrosion surface increased. The corrosion products formed on the surface of the alloy exposed for 1 d, and further corrosion made the corrosion product layer much dense, increasing the corrosion resistance and protecting the alloy from further corrosion.
Creep age forming techniques have been widely used in aerospace industries. In this study, we investigated the effect of aging temperature (143 °C–163 °C) on the creep behavior of Al-Li-S4 aluminum alloy and their mechanical properties at room temperature. The mechanical properties were tested by tensile testing, and the microstructural evolution at different aging temperatures was examined by transmission electron microscopy. Results show that the creep strains and the room-temperature mechanical properties after creep aging increase with the aging temperature. As the aging temperature increases, the creep strain increases from 0.018% at 143 °C to 0.058% at 153 °C, and then to 0.094% at 163 °C. Within 25 h aging, the number of creep steps increases and the duration time of the same steps is shortened with the growth of aging temperatures. Therefore, the increase in aging temperatures accelerates the progress of the entire creep. Two main strengthening precipitates θ′ (Al2Cu) and T1 (Al2CuLi) phases were characterized. This work indicates that the creep strain and mechanical properties of Al-Li-S4 alloys can be improved by controlling aging temperatures.
Magnetic Fe3O4@Cu/Ce microspheres were successfully prepared by one-step solvothermal approach and further utilized to remediate toxic arsenic (As(III)) pollution. The effects of Cu/Ce elements co-doping on the crystal structure, catalytic oxidation and adsorption behaviors of magnetic microspheres were researched systematically. The results showed that with the aid of Cu/Ce elements, the grain size reduced, lattice defects increased, and the oxygen vacancies and surface hydroxyl groups were improved. Therefore, Cu/Ce elements endowed magnetic Fe3O4@Cu/Ce microspheres with excellent As(III) removal performance, whose maximum adsorption capacity reached 139.19 mg/g. The adsorption mechanism mainly involved catalytic oxidant co-adsorption. This research developed a feasible strategy for the preparation of high efficiency magnetic adsorbent to enhance the removal of As(III).
Zinc leaching residue (ZLR) contains high content of valuable metals such as zinc and iron. However, zinc and iron mainly exist in the form of zinc ferrite, which are difficult to separate and recover. This study proposed a new process involving sulfidation roasting, magnetic separation and flotation to recover zinc and iron in ZLR. Through sulfidation roasting of ZLR with pyrite, zinc and iron were converted into ZnS and Fe3O4. The effects of pyrite dosage, roasting temperature and roasting time on the sulfidation of zinc in ZLR were investigated. The results showed that the sulfidation percentage of zinc reached 91.8% under the optimum condition. Besides, it was found that ball-milling was favorable for the separation and recovery of zinc and iron in sulfidation products. After ball-milling pretreatment, iron and zinc were enriched from sulfidation products by magnetic separation and flotation. The grade of iron in magnetic concentrates was 52.3% and the grade of zinc in flotation concentrates was 31.7%, which realized the recovery of resources.
In this study, a lab-scale upflow anaerobic sludge blanket (UASB) reactor was applied to studying the high-rate nitrogen removal of granule-based anammox process. The nitrogen removal rate (NRR) finally improved to 15.77 kg/m3/d by shortening hydraulic retention time (HRT) to 1.06 h. Well-shaped red anammox granules were extensively enriched inside the reactor. The results of nitrogen removal kinetics indicated that the present bioreactor has great nitrogen removal potential, because the maximum rate of substrate utilization (Umax) predicted by Stover-Kincannon model is suggested as 55.68 kg/(m3·d). Analysis of the microbial community showed that the anammox genus Candidatus Kuenenia dominated the bacterial communities. The relative abundance of Candidatus Kuenenia rose from 12.29% to 36.95% after progressively shorter HRT and higher influent substrate concentrations, illustrating the stability of nitrogen removal performance and biomass enrichment offered by the UASB in carrying out high-rate anammox process.
The purpose of this research was to better understand the water quality status of the Xiangjiang River, China, and to evaluate the risks posed by the river water. Precisely, ten water quality parameters including pH, dissolved oxygen (DO), Escherichia coli (E. coli), potassium permanganate index (CODMn), dichromate oxidizability (CODcr), five-day biochemical oxygen demand (BOD5), ammonia nitrogen (NH4+-N), total phosphorus (TP) and fluoride (F−) as well as metal(loid)s (Pb, Hg, Cd, As, Zn, Cu and Se) were monitored monthly in 2016 at 12 sampling sites throughout the Hengyang section of the Xiangjiang River. Concentrations of all parameters were presented according to rainy and dry seasons. They were compared with Chinese surface water standards and WHO drinking water limits to assess the sustainability of the river water status. Principal component analysis (PCA) revealed different pollution sources in different seasons. Dual hierarchical cluster analysis (DHCA) was applied to further classify the water quality variables and sampling sites. Besides, a risk assessment was introduced to evaluate the carcinogenic and non-carcinogenic concerns of heavy metal(loid)s to human health. This research will help to optimize water monitoring locations and establish pollution reduction strategies on the preservation of public safety.
The corrosion behaviors and electrochemical properties of Q235A steel in the treated water containing corrosive halide anions (F−, Cl−) have been investigated with corrosion tests of static coupon and dynamic coupon testing, electrochemical measurement of open-circuit potential and linear sweep voltammetry. The results reveal that the existence of F− and Cl− ions in the simulated treated water accelerate the corrosion rate of Q235A steel. The corrosion rate reaches maximum with F− concentration of 50 mg/L, Cl− concentration of 200 mg/L, respectively. However, Q235A steel would passivate when an applied potential is added to the system. Meanwhile, the initiating passive potential becomes positive with F−, Cl− concentration increasing. There is a little influence of F−, Cl− concentration on the initiating passivation current density. Therefore, it is necessary to control F−, Cl− concentration in the treated water when it is recycled by the pipelines made of Q235A steel.
Left-hand materials have drawn increasing attention from many disciplines and found widespread application, especially in microwave engineering. A sandwiched metamaterial consisting of multi-nested square-split-ring resonators on the top side and a set of wires on the back side is proposed. Scattering parameters are retrieved by high-frequency structure simulator (HFSS) software based on the finite element method. Effects of square-split-ring number on the left-hand characteristics containing negative values of permittivity, permeability, and refractive index have been intensively investigated. Simulated results show that obvious resonant left-hand characteristics could be observed within 8–18 GHz, and the resonant frequency counts are inclined to be in direct proportion to the square-split-ring number over 8–18 GHz. Besides, the proposed sandwiched metamaterial with three square-split-ring resonators and three wires presents the widest frequency band of left-hand characteristics in a range of 8–18 GHz. Further, electromagnetic field distributions demonstrated that the induced magnetic dipole dominates the resonant absorption. The multi-peak resonance characteristics of square-split-ring resonant structure are considered to be a promising candidate for selective-frequency absorption or modulation toward microwave frequency band.
Ferrocene-based porous organic polymer (FcPOP) was constructed with ferrocene and porphyrin derivatives as building blocks via Schiff-base coupling. FcPOP was well characterized, and exhibited good thermal stability, high porosity, microporous structure, and homogeneous pore size distribution. Ferrocene blocks with highly electron-rich characteristics endowed FcPOP with excellent adsorption capacity of CO2 and methyl violet. The kinetic study indicated adsorption of methyl violet onto FcPOP mainly complied with pesudo-second order model. The maximum adsorption capacity of FcPOP derived from Langmuir isotherm model reached up to 516 mg/g. More importantly, FcPOP could be easily regenerated and repeatedly employed for removal of methyl violet with high efficiency. Overall, FcPOP in the present study highlighted prospective applications in the field of gas capture and dyeing wastewater treatment.
A shield machine with freezing function is proposed in order to realize tool change operation at atmospheric pressure. Furthermore, the transformation project of freezing cutterhead and tool change maintenance method are put forward. Taking the shield construction of Huanxi Power Tunnel as an example, a numerical analysis of the freezing cutter head of the project was carried out. The results show that when the brine temperature is −25 °C, after 30 d of freezing, the thickness of the frozen wall can reach 0.67 m and the average temperature drops to −9.9 °C. When the brine temperature is −30 °C, after 50 d of freezing, the thickness of the frozen wall can reach 1.01 m and the average temperature drops to −12.4 °C. If the thickness of the frozen wall is 0.5 m and the average temperature is −10 °C, as the design index of the frozen wall, the brine temperature should be lower than −28 °C to meet the excavation requirements in 30 d. Analyzing the frozen wall stress under 0.5 m thickness and −10 °C average temperature condition, the tensile safety factor and compressive safety factor are both greater than 2 at the most dangerous position, which can meet the tool change requirements for shield construction.
Solar water heaters (SWH) are widely used in urban areas because of their advantages in reducing energy consumption and mitigating greenhouse gas emissions. However, the performance of SWH subjected to obstructions is unclear yet. In this study, we present a numerical evaluation on thermal performance of façade-installed SWH under three typical obstructed scenarios, based on various levels of sunshine duration. This study is carried out for four locations with various latitudes across China. Thermal performance is measured by solar fraction for annual and monthly evaluation. The results show that the obstruction can seriously degrade annual solar fraction of SWH, even in the 4-hour sunshine duration scenario, for all the studied locations. Interestingly, only lengthening sunshine duration in the standard day (e.g., from 2 h to 4 h) may not result in increasing annual solar fraction markedly. In terms of the monthly performance, solar fraction in January and December decreases significantly, while from May to August it just declines slightly, except for Guangzhou having a swift reduction. This study can provide insights into the behavior and promote the appropriate application of SWH in urban areas.
Based on a typical prototype of a soil slope in engineering practice, a numerical model of a three-stage soil slope supported by the anchor frame structure was established by means of FLAC3D code. The dynamic responses of three-stage soil slope and frame structure were studied by performing a series of bidirectional Wenchuan motions in terms of the failure mode of three-stage structure, the acceleration of soil slope, the displacement of frame structure, and the anchor stress of frame structure. The response accelerations in both horizontal and vertical directions are the most largely amplified at the slope top of each stage subjected to different shaking cases. The platforms among the stages reduce the amplification effect of response acceleration. The residual displacement of frame structure increases significantly as the intensity of shaking case increases. The frame structure at each stage presents a combined displacement mode consisting of a translation and a rotation around the vertex. The anchor stress of frame structure is mainly increased by the first intense pulse of Wenchuan seismic wave, and it is sensitive to the intensity of shaking case. The anchor stress of frame structure at the first stage is the most considerably enlarged by earthquake loading.
Mountain tunnel crossing a normal fault in seismically active zone is easily affected by normal fault slip and earthquake. It is necessary to study tunnel dynamic response under action of normal fault slip and earthquake. In this paper, a three-dimensional normal fault sliding device was designed, and a shaking table test was carried out to study tunnel seismic performance under normal fault slip. The results show that peak acceleration of lining is dominated by an existence of fault and direction of seismic excitation, not normal fault slip. And the incremental strains of lining in critical zone with 1.7 times fault thickness and centered in faults induced by normal fault slip and seismic excitation are larger than ones only by seismic excitation. And the incremental strains in critical zone increase with the increase of normal fault slip magnitude ranging from 0 to 2 mm. And normal fault slip results in a significant reduction of overall tunnel stiffness subjected to an earthquake. These experimental results provide a scientific reference for prevention and control measurement of tunnel damage under earthquake and normal fault slip.
Through rock mechanics test, similar simulation experiment, borehole photographic observation of rock fissure, numerical simulation calculation of plastic zone distribution and deformation monitoring of rock mass during undersea mining, the fractal evolution mechanisms of rock fracture in undersea metallic deposits of Sanshandao Gold Mine were studied by fractal theory. The experimental researches on granite mechanics test in undersea deposit indicate that with the increase of load, the granite deformation energy and the fractal dimension of acoustic emission (FDAE) increase gradually. However, after reaching the peak stress of specimen, the fractal dimensions of acoustic emission (FDAEs) decrease and the granite specimen fails. Therefore, the fractal dimension evolution of rock failure can be divided into four stages, which are fissure inoculation stage, fissure growth stage, fissure expansion stage and fracture instability stage, respectively. By calculating and analyzing the damage photographs of rock specimens in Sanshandao Gold Mine, the fractal dimension of rock fissure is 1.4514, which is close to the average value of FDAE during granite destruction, i.e., 1.4693. Similar simulation experiments of undersea mining show that with the excavation proceeding, the FDAE in rock stratum increases gradually, and when the thickness of the isolation roof is less than 40 m, the FDAE begins to decrease, and meanwhile the sign of water inrush emerges. The numerical simulation researches on the plastic zone distribution of undersea mining in Sanshandao Gold Mine indicate that the fractal dimension of plastic zone (FDPZ) where the failure characteristics occur is 1.4598, close to the result of similar simulation experiment of 1.4364, which shows the sign of water inrush. Meanwhile, the thickness of the isolation roof for undersea mining should be more than 40 m, which is consistent with the results of similar simulation experiment. In Sanshandao Gold Mine, the rock fissures in undersea mining were observed by borehole photography and the rock mass deformation was monitored by multi-point displacement meters, and at the same time the fractal dimensions of strata borehole fissure distribution and energy release ratio (ERR) of rock mass were calculated by fractal principle, which are 1.2328 and 1.2685, respectively. The results demonstrate that rock deformation and fissure propagation are both in the second stage of fissure growth, and have not reached the fourth stage of fracture instability. Therefore, the conclusion can be obtained that the undersea mining in Sanshandao Gold Mine is safe at present.
This study investigates the influence of different pantograph parameters and train length on the aerodynamic drag of high-speed train by the delayed detached eddy simulation (DDES) method. The train geometry considered is the high-speed train with pantographs, and the different versions have 3, 5, 8, 10, 12, 16 and 17 cars. The numerical results are verified by the wind tunnel test with 3.6% difference. The influences of the number of cars and the position, quantity and configuration of pantographs on flow field around high-speed train and wake vortices are analyzed. The aerodynamic drag of middle cars gradually decreases along the flow direction. The aerodynamic drag of pantographs decreases with its backward shift, and that of the first pantograph decreases significantly. As the number of pantographs increases, its effect on the aerodynamic drag decrease of rear cars is more significant. The engineering application equation for the aerodynamic drag of high-speed train with pantographs is proposed. For the 10-car and 17-car train, the differences of total aerodynamic drag between the equation and the simulation results are 1.2% and 0.4%, respectively. The equation generalized in this study could well guide the design phase of high-speed train.