Abstract: The innovation in the direction of scientific research is a major issue in the development of science and technology, which involves variety of philosophy and methodology, and it is important and necessary for scientists and engineers. Based on the interpretation of “innovation”, combined with the author’s understanding and experience, this paper summarizes a 32 words formula for the scientific and technological innovation of engineering, and proposed the specific methods for scientific research innovation, such as “first principle, demand guidance, positive extrapolation, interdisciplinary, reverse thinking, node exhaustion”, as well as the concepts of model tree, node method and so on. The typical application of these methods is demonstrated by taking oil and gas drilling technology as an example.
Abstract: Aiming at the problems of pipeline transportation blockage and filling body stratification caused by waste rock–unclassified tailings high-concentration slurry, the effects of superplasticizer and stirring parameters on the slurry homogenization were experimented with, and the quantitative characterization of slurry homogenization was explored. Initially, the polycarboxylate (PC) superplasticizer with the best suitability was screened out based on the bleeding-slump test, and the mathematical correlations of the slump and bleeding rate with the optimal superplasticizer dosage range were obtained by regression. The rheological properties of the slurry and the filling body strength were then determined at different PC superplasticizer dosages, and separate mathematical models for correlations of slurry rheological parameters and mechanical properties with superplasticizer dosage were built. Next, the slurry surface images under different stirring conditions were acquired with the Nikon D350 camera, and their information entropies were calculated. Meanwhile, the OTSU algorithm was used to perform image segmentation thresholding, and the images were binarized via Matlab, followed by a calculation of the proportion of black pixels in the binarized images. Further, the variation trends of image information entropy and black pixels proportion with PC superplasticizer, rock/tailing ratio (mass ratio of waste rock to unclassified tailings), and stirring time were derived. Finally, the homogenization mechanism in the waste rock–unclassified tailings filling slurry was revealed based on the PC superplasticizer’s regulatory role in fine particle absorption and dispersion, which was further validated by the relationship between the zeta potential of cement paste and the dosage of PC superplasticizer. On this basis, a quantitative model of slurry homogenization was developed based on the slump, bleeding rate, rheological properties, strength characteristics, and image information, and the optimal parameters of waste rock–unclassified tailings high-concentration filling slurry were obtained by multi-objective programming. The results show that the PC superplasticizer is highly suitable for the slurry, which can reduce its yield stress and plastic viscosity coefficient and improve its fluidity. When the dosage of PC superplasticizer is 0.50%, the yield stress and plastic viscosity of the slurry is reduced by 34.4% and 21.2%, respectively, in comparison to the case without superplasticizer. The slurry rheological properties conform to the Bingham plastic model. Increasing the PC superplasticizer dosage improves the early strength of the filling body and weakens the 28-d strength. Nonetheless, within the optimal dosage range, all the filling body strengths can meet the mine filling requirements. Slurry surface images with higher information entropy and a smaller proportion of black pixels indicate a higher degree of slurry homogenization. Moreover, the entropy value of slurry surface images tends to increase initially and then decrease with the prolonging of stirring time and the heightening of the rock/tailing ratio. When the rock/tailing ratio is constant, the proportion of black pixels is the largest at a stirring time of 3 min, followed by 5 min, and the smallest at 4 min. According to the quantitative model results of slurry homogenization, the reasonable dosage range of PC superplasticizer is 0.26%–0.5%, and the optimal stirring time is 4.3 min. The degree of homogenization is the best at a 0.5% dosage, at which point the slurry has a plastic viscosity μ of 0.79 Pa·s and a yield stress τ of 202.25 Pa.
Abstract: Low grade is one of the three characteristics of mineral resources in China. With the exploitation of a large number of mineral resources, more tailings will inevitably be produced in the concentrator, and transporting them to the goaf is the best way to deal with tailings. The tailings are compacted by a deep cone thickener (DCT) to prepare a paste. The mud height and underflow concentration are the key parameters to ensure the filling efficiency and quality. To explore the relationship between mud height and underflow concentration of the DCT, mathematical models of mud height and underflow concentration under different conditions were established based on the Terzaghi effective stress principle and the relationship between compressibility $ \alpha $ and mud pressure. Taking a mine as an example, the industrial application and difference analysis of the mathematical model are conducted. Results show that the relationship between mud height and underflow concentration is a power function. When $ \alpha $ is constant, dh/dc decreases gradually with the increase of mud height, and the underflow concentration reaches 100% when the mud height is 29.4 m, which is inconsistent with reality. When $ \alpha $ varies, dh/dc increases gradually with the increase of mud height, and the mud layer becomes difficult to compress. This model is consistent with reality. Moreover, for this mine, the mud height is 5.79 m when the underflow concentration of the DCT increases from 60% to 65% and 11.22 m when the underflow concentration increases from 70% to 75%; the mud height required by the latter is approximately 1.94 times that of the former. The physical significance of the mathematical model is that the effective stress and intergranular porosity vary at different mud heights. As the height of the upper mud layer increases, the tailings particles at the bottom are rearranged and combined under pressure, the water between the pores is discharged, and the particles are compressed more densely. That is, the higher the mud height is, the smaller the intergranular porosity and the higher the underflow concentration. Notably, the mathematical model is applicable to both dynamic and static operations of the DCT from two perspectives, that is, compaction mechanism and effective stress; however, it cannot be generalized. Finally, according to the mathematical model expression and practical application, the mud layer in the DCT is divided into mixed sedimentation, deceleration compression, and limit compression areas.
Abstract: In the process of underground engineering construction, tuff in the fault fracture zone under a three-dimensional stress state loses particles under the action of fluid–solid coupling, causing the structural instability of the fault fracture rock. Finally, fault water inrush disaster occurs. Based on this, the field fault sampling has been conducted, and the broken rock triaxial seepage test system has been used to investigate the phenomenon of particle loss in samples with various particle sizes under triaxial load, as well as the effect of particle loss on pore structure and the time-varying evolution of seepage velocity. The following are the results: (1) The quality and time of the particle loss of broken tuff satisfy the exponential nonlinear relationship under different levels of triaxial stress, with a correlation coefficient of not less than 94%. Particle loss quality is inversely related to axial pressure and confining pressure, indicating that the higher the axial displacement, the smaller the decrease in particle loss mass with confining pressure. (2) The porosity increases rapidly between 0 and 60 s during the infiltration process. The seepage evolution process of the pore structure is related to the particle size gradation; that is, the overall porosity increases as the value of n (Talbot power exponent) increases. In the case of the same value of n, the porosity, which ranges from 0.33 to 0.52, decreases as the axial displacement and confining pressure increase. (3) Owing to the regular loss of particles in the sample, the time-varying evolution process of the seepage velocity of fractured tuff can be divided into three stages: stable seepage, sudden increase of seepage velocity, and approximate pipe flow. When the confining pressure is 0.8 MPa, each stage’s flow velocity is higher than that of the corresponding stage when the confining pressure is 1.4 MPa. The stable seepage stage has a short duration and low flow rate, and its occurrence times decrease as the n value increases. In the stage of seepage velocity surge, velocity surges to a peak value. The approximate pipe flow stage maintains a relatively stable and high flow velocity despite occasional fluctuations. The research results can offer a theoretical basis for studying the evolution law of fault water inrush disaster.
Abstract: To explore the reasonable width of the coal pillar and surrounding rock control technology of the mining roadway in a close-distance coal seam working face, this paper took the mining of No.10 and No.11 coal seams of the Huipodi coal mine as the engineering background. Through numerical simulation, theoretical analysis, field practice, and other technical means, the evolution of the coal pillar failure, influencing factors, and damage range of floor under different widths were analyzed. The surrounding rock control technology of the mining roadway was studied in depth. Results show that: (1) During the four stages of reserved, section, protective, and isolated coal pillars, the damage scope of the coal pillar gradually increased. The proportion of the elastic core of the coal pillar increased with the increase of the coal pillar width. The mining roadway in this coal seam evolves from asymmetric failure to symmetrical failure. The failure width of the coal pillar is directly proportional to the buried depth and inversely proportional to the coal seam dip angle, cohesion, coal pillar width, internal friction angle, and Poisson’s ratio. (2) With the increase in coal pillar width, the width and depth of the coal pillar floor failure will change. Moreover, the floor failure concentrated on the side of the coal pillar edge, and the damaged floor area under the coal pillar is observed to be small. (3) The maximum principal stress under the floor deflects owing to the concentrated stress of the coal pillar. The larger is the distance between any point of the floor and the centerline of the coal pillar, the smaller is the deflection angle of the maximum principal stress. With the increase in the distance between the roadway and coal pillar edge, the plastic zone of the roadway surrounding rock initially changes from an inclined X-shaped distribution to an inclined 8-shaped distribution, which then changes to an inclined O-shaped distribution and finally to an elliptical distribution. When the distance from the coal pillar is close, the roadway often shows an asymmetric failure, and the support should also take the form of asymmetric support.
Abstract: Based on the UDEC (Universal distinct element code) modeling and grain-based model (UDEC-GBM), the effects of mineral’s (e.g., feldspar) cleavage angle, the confining effect of the cleavage angle and cleavage spacing on mechanical properties, microcracking process and mechanism of hard rocks, and the resulting problems in engineering were investigated in the present study. Numerical results show that: (1) Mineral cleavage has a considerable angle effect. As the cleavage angle increases from 0° to 90°, the elastic modulus, uniaxial compressive strength, and post-peak characteristics of the rock are affected. The total number of transgranular cracks is obviously affected, which is mainly reflected by the increase in the number of feldspar tensile cracks and the number of feldspar shear cracks increases to a maximum at 60° and then decreases, and the number of quartz tensile cracks changes considerably. In general, the number of transgranular cracks increases, while the number of intergranular cracks decreases. However, tensile and intergranular cracking dominate the cracking process. (2) The cleavage effect is affected by the confining pressure. The confining pressure will cause the number and proportion of intergranular cracks and transgranular cracks to change. However, the confining pressure at different angles has different effects on the number and proportion of intergranular cracks and transgranular cracks. (3) As the cleavage spacing increases from 2 to 4 mm, the number of transgranular cracks increases and the number of intergranular cracks decreases. However, the ratio of the total shear and tensile cracks remains constant, indicating that microscopic tensile and shear cracking mechanisms are almost unaffected. In addition, when the proportion of minerals with cleavage characteristics is high and the type of mineral has a considerable influence on the rock properties, the influence of cleavage characteristics on rock failures, such as spalling and rockburst, should be given attention.
Abstract: The steel industry is an important embodiment of national productivity and contributes to the development of the national economy and defense construction as a material foundation. Recently, China’s crude steel production ranked first in the world and in 2020, it exceeded 1 billion tons for the first time, reaching 1.065 billion tons. However, the steel industry is also a major energy consumer and polluter. In the current national coordination to do a good job of “carbon peak” and “carbon-neutral” background, the traditional steelmaking process urgently needs to be transformed into intelligent and green. Recently, as an important branch of machine learning, with artificial neural networks as the basic architecture, deep learning, a nonlinear modeling algorithm that can extract features from data and realize knowledge learning, has been applied in various industrial fields. The steelmaking process is an extremely complex industrial scenario with many influencing factors and high-security requirements. It is also an area where deep learning has not been applied on a large scale yet. Accordingly, in this study, the principles and types of deep learning were compared, and the development history and research status of deep learning in the steelmaking process with domestic and foreign application examples were summarized. The application of deep learning to the steelmaking process mainly has the advantages of simple feature extraction, strong generalization ability, and high model plasticity, but it also faces the challenges of high data dependency, difficult preprocessing, and verification of production safety. In the future, with the application of high-precision sensors, popularization of the Internet of Things, iteration of computing hardware, and innovation of algorithms, deep learning models can be effectively applied to more scenarios in steelmaking, which will promote the intelligent development of the metallurgical industry.
Abstract: Using bubbles to remove inclusions in steel is rapidly becoming a popular method for refining. Fine bubbles are thought to be more effective on inclusion removal than big bubbles. The fine bubbles can be formed in molten steel using the argon injection into ladle shroud technology. There are two stages during the formation of fine bubbles in ladle shroud: bubble detachment from wall orifice and detached bubbles splitting into smaller ones in turbulent steel. Many reports have been published on the water model of the argon injection into ladle shroud technology, but industrial experimental research is in its early stage. In this study, high argon flow was injected into a ladle shroud and adopted in continuous casting production to produce fine argon bubbles in a tundish. The bubbles were captured by dipping a cold steel sheet into molten steel. The captured bubbles at the surface of a hot-dipped steel sheet, with a size of 1.0–3.0 mm, characterized the argon bubbles at steel/slag interface and slag phase in the upper part of a tundish rather than those inside molten steel in tundish. The bubbles inside molten steel in tundish were characterized by the captured bubbles in the interior of a hot-dipped steel sheet, and their morphology, size, and number were analyzed using scanning electron microscopy and confocal microscopy. The bubbles inside molten steel in tundish have a spherical shape and occasionally adhere to each other. These bubbles rang in size from 100 to 1000 μm, with an average of 500 μm. They are dispersed at the exit of a ladle shroud in its lower position, with a density of 15.2 cm–2. Moreover, it was observed that a bubble could adhere to inclusion, even multiple inclusions for part of bubbles. Bubbles adhered more strongly to Al2O3 inclusions than that to CaO(?MgO)?Al2O3?SiO2 complex inclusions.
Abstract: Blast furnace (BF) ironmaking is considered to be the most popular technology to meet the increasing steel demand worldwide, but it is responsible for the most CO2 emissions in the blast furnace-basic oxygen furnace production process. The utilization of biomass/biochar in BF ironmaking is an effective countermeasure to reduce its CO2 emission, as biomass/biochar is a renewable carbon source and environment neutron. Charging the biochar composite briquette (BCB) is a convenient method to introduce biomass/biochar into BF. The present research investigates the reaction behavior of the BCB in the BF. The BCB for the BF was prepared using cold briquetting followed by low-temperature heat treatment. The BCB was composed of 11.1% carbon, 72.7% magnetite, 11.25% wustite, 0.77% metallic iron, and 4.67% gangue (all in mass fraction). The BCB reaction model in the BF was developed considering the step-wise gaseous reduction of iron-oxide particles, CO2 gasification of biochar particles, internal gas diffusion in the BCB, and mass transfer between the BCB and the environment. Isothermal BCB reaction tests were conducted for model validation. Using the model, the changes of the BCB iron-oxide reduction fraction and biochar conversion rate and the BCB microstructure evolution under simulated BF conditions were analyzed. The model was also applied to predict the change of the BCB iron-oxide reduction fraction, change of the BCB biochar conversion, change of the BCB CO generating rate, and change of the BCB CO2 generation rate along a solid flowing path near the mid-radius in an actual BF. Results showed that under simulated BF conditions, the BCB underwent fast self-reduction and structure changes (forming low-melting compounds and transforming from the slag matrix to the iron network) from 60 min (973 K) to 120 min (1273 K). In an actual BF, the BCB reaction route is mainly divided into three stages: (1) reduction by BF gas (473–853 K), (2) reduction by the BF gas and partial self-reduction (853–953 K), and (3) full self-reduction (953–1150 K). In the stages involving BCB self-reduction, the iron oxide in the BCB reduces faster than the sinter, and the biochar gasifies faster than the coke. Moreover, in these stages, the BCB has the functions of increasing the BF gas utilization efficiency and lowering the temperature level of the BF thermal reserve zone.
Abstract: To investigate the effect of slag composition on desulfurization and alkali removal ability of blast furnace slag for smelting Bayan Obo ore, based on the actual composition of blast furnace slag, the effect of free basicity (Ro), w(MgO), and w(Al2O3) on the desulfurization and alkali removal ability of blast furnace slag was investigated by performing orthogonal experiments and on the basis of five-element pseudoternary phase diagrams of various components of a blast furnace slag system calculated and drawn using Factsage 7.1 thermodynamic simulation software, and the appropriate control range of Ro, w(MgO) and w(Al2O3) in the slag were given in combination with the production practice. The results show that: Ro is the most significant factor affecting slag desulfurization and alkali removal ability. With the increase in Ro, the O2? concentration in slag increases, resulting in Si?O disintegration, and slag viscosity decreases. In addition, the mass transfer between slag and metal liquid is accelerated, which makes S2? easier to migrate into slag, the thermodynamic and kinetic conditions of slag desulfurization are improved, thus improving the desulfurization ability. The appropriate Ro should be controlled within the range of 1.05–1.15. w(MgO) is a secondary factor affecting the slag desulfurization ability. With the increase in w(MgO), the fluidity and stability of the slag are improved, which are beneficial for improving the kinetic conditions of slag desulfurization and reducing the activity of (K2O+Na2O) in the slag, thus improving the alkali removal ability. Appropriate w(MgO) should be controlled at approximately 15%. w(Al2O3) is a secondary factor affecting the alkali removal ability of blast furnace slag. With the increase in w(Al2O3), high melting point materials such as MgAl2O4 are easily formed, thereby increasing the consumption of free oxygen ions in the slag. This increase is not conducive to the improvement of desulfurization reaction kinetic conditions. Although increasing w(Al2O3) is beneficial for removing alkali, high w(Al2O3) is not conducive to desulfurization and leads to an increase in slag viscosity. Appropriate w(Al2O3) should be controlled at approximately 12%.
Abstract: Due to the issue of raw material depletion, lithium-ion batteries are becoming less value-added. In addition, the highly toxic organic electrolytes contained in them cause serious harm to humans and the environment. That is why the effective recovery of spent lithium-ion batteries is of great importance for the development and sustainable use of lithium-ion batteries. Currently, recovery of metals present in spent lithium-ion batteries mainly relies on hydrometallurgical extraction: The main metals are extracted through acid or alkali media followed by recovery of metal compounds through further processing or the resynthesis of high-performance materials. Among them, acid leaching is a short and highly efficient process; however, this process dissolves all the metal ions in the solution, making it difficult to subsequently separate and purify the valuable metals. Contrarily, the hydroxide of impure metal in lithium-ion batteries shows low solubility, whereas lithium, nickel, and cobalt have high solubility, allowing for the formation of complexes with ammonia ions that can exist in alkali solution in large quantities. Thus, alkaline leaching has better selective leaching of metals in electrode materials due to the high solubility of lithium, nickel, and cobalt ammonia complexes and has a more efficient and cleaner recovery process, which is of outstanding importance in the industry. Most research was mainly focused on various acid recovery systems and scales, and the research progress on the alkaline recovery process was insufficient. Here, based on the industrial research status of alkali leaching recovery, four alkali leaching recovery systems, which include the ammonia leaching-reductant-hot working system, ammonia leaching-reductant-electrodeposition system, ammonia leaching-reductant-lithium adsorption system, and ammonia leaching-reductant-oxidation separation system, were reviewed along with their principles and advantages. Finally, a brief summary of the recovery methods for spent lithium-ion batteries was expressed.
Abstract: In recent years, lithium-ion batteries using nickel-cobalt-manganese ternary materials as cathode materials have advantages of good electrical performance, high specific energy, green environmental protection, low cost, and high discharge stability. These have been widely used in new energy vehicles and portable electronics product areas. As a new generation of rechargeable batteries, lithium batteries have a certain service life, which is generally 3–5 years. Therefore, the rapid development of lithium-ion batteries has caused a blowout increase in the number of used lithium-ion batteries. Waste ternary lithium-ion batteries are very harmful to the environment and humans, but valuable metals such as lithium, nickel, cobalt, and manganese have a high recycling value. In terms of resource recycling and environmental protection, used lithium-ion batteries have a high recycling value. At present, the recycling of waste lithium-ion batteries is facing some problems. For example, the diversity of electrode materials makes their separation and purification difficult, and the high cost can also cause some problems such as secondary pollution. Therefore, it is necessary to find green and low-cost methods for the recycling of waste lithium-ion batteries. Microwave metallurgy has outstanding advantages in this respect. Therefore, this paper used the mechanically crushed ternary lithium battery as the raw material for studying the dielectric properties of the apparent density of the positive electrode material at room temperature and the microwave dielectric properties and absorption that change with temperature. Results show that at room temperature, the cathode material has the best dielectric performance at an apparent density of 1.484 g·cm–3. During the heating process, the cathode material has good microwave absorption performance at 25–700 ℃. At 400 ℃, the dielectric constant $ {\textit{ε}}_{\rm{r}}^{'} $ reaches the maximum value of 11.96 F·M–1. With the increase in the microwave power, the time for the positive electrode powder to rise to 700 °C is significantly shortened, and the maximum heating rate is in the range of 320–450 °C. The changing trend of the dielectric properties is consistent with the changing trend of the microwave heating characteristics.
Abstract: Causality is a generic relationship between an effect and a cause that produces it. The causal relationship among things has been a research hotspot; however, the complexity of causality is sometimes far beyond our imagination. Although some causality problems seem easy to analyze, finding an exact answer may not be easy. Nevertheless, through the continuous innovation and development of empirical research methods in recent decades, we have had several clear analytical frameworks and effective methods on how to define and estimate causality. Exploring the causal effects among things is a promising research topic in many fields, such as statistics, computer science, and econometrics. With Joshua D. Angrist and Guido W. Imbens winning the Nobel Prize in economics for their methodological contributions to the analysis of causality in 2021, causal inference is expected to thrive in these fields. This paper briefly introduces the basic concepts involved in causal inference and its three analytical frameworks, namely, counterfactual framework (CF), potential outcome framework (POF), and structural causal model (SCM). Firstly, we introduce the origin of causal effects according to CF. Secondly, based on the counterfactual theory, two analysis frameworks are considered (POF and SCM), and we introduce the associated key theories and methods. The SCM explains the causal theory through mathematics and computable language, and it is a calculation model that clearly expresses hypotheses, propositions, and conclusions. It quantitatively analyzes the pair of cause variables under the premise that the cause and effect variables are known. The POF makes up for the missing potential results, such that the effect of the observational research is close to experimental research. The SCM is a causal inference method based on graph theory. It divides events into three levels: observation, intervention, and counterfactual. Through the “do” operation, the causal relationship at the intervention and counterfactual levels could be reduced to low-dimensional problems, which can be solved via statistical methods. Finally, the current application scenarios of causal inference in many fields are discussed in this paper, and the three analysis frameworks are compared.
Abstract: The CPU is the core part of all integrated circuits. Although some homemade CPUs of proprietary intellectual property rights are rapidly developed, few high-performance chipsets are available, especially in server domains, to match them. Thus, the total systems designed using these CPUs and low-performance chipsets do not have proper performance. The Loongson CPU faces the same problem. To seek better chipsets for it, certain architecture and some methods are designed and implemented to adapt different types of chipsets. In this architecture, a field-programmable gate array (FPGA) is linked between a CPU and these chipsets. An FPGA is divided into three domains: an HT (hyper transport) bus domain, a processing domain for important but temporarily indeterminate signals, and a CPLD (complex programmable logic device) function domain. In these adaption processes, HT bus signals, the temporarily indeterminate signals, and power signals in CPUs and chipsets are respectively linked into three domains in an FPGA and treated by a programming FPGA to perform all types of possible signal combinations. The power sequence between the CPU and chipsets is coordinated to the right order using an FPGA. The signal integrity difference between them is avoided and trimmed to the right state by amending their signals in the FPGA. In this system, the experimental results show that this architecture and these methods simultaneously make more chipsets work together to be adapted than before in a single motherboard. This combination avoids researching and developing many different motherboards for every type of possible chipset and greatly reduces costs. High-performance server chipsets can be found to properly match the Loongson CPU and have better specifications and higher performance than those currently used for the Loongson CPU. A prototype system composed of the Loongson CPU and five types of chipsets is designed and implemented. Using the above architecture and methods, a type of optimal server chipsets SR5690 + SP5100 has been found, and the matching principles or correct settings for the signal connection and power sequence have been concluded. The Loongson 3B4000 two-way SMP motherboard with SR5690 + SP5100 chipsets is also produced. On this motherboard, the results of evaluation experiments on computing performance tests by the SPEC CPU 2006 program, storage performance tests by the IO zone program, and network performance tests by the Netperf program are performed. Compared with the current Loongson 3B4000 server with a 7A1000 chipset, the test results show the performance on three items is improved by approximately 10%. The combination of the Loongson CPU and this type of server chipset provides wider applications in the server market and promotes the development of the Loongson CPU in its ecosystem.
Abstract: An AFT oxidation fan room is a kind of composite structure of reinforced concrete structure supporting the steel tank in the desulfurization process. It is a common structural form of a power plant. The obvious vibration generated by the structure is not conducive to the normal production and operation of the power plant and may even cause accidents. Therefore, on-site monitoring and a simulation calculation are carried out for the AFT structure to study the causes of vibration of the AFT structure and clarify its vibration mechanism. First, a field investigation of the AFT structure is carried out combining video monitoring and local structure vibration monitoring. Based on the simulation method of the fluid-solid interaction, a simulation method to simplify the action of the mixer and the oxidation wind in the steel tank is then proposed, and the vibration characteristics of the AFT structure are further studied through the proposed numerical simulation method. Finally, numerical simulation results are compared with the monitoring results, and causes of vibration differences in various parts of the structure are studied. Results show that video monitoring can quickly identify the structure movement track. Local monitoring results show that the mixer is the main factor of the structural vibration, and the aeration of the oxidation wind intensifies the structural vibration response, causing different degrees of damage to the infill wall between the columns of the structure. The dynamic response law of different positions of each column and the upper steel tank of the structure is found to be more different. A comparison of numerical simulation results with monitoring results verified the calculation method of simplifying the mixer and the oxidation wind effect, providing a reference for the analysis of the vibration response, damage mechanism, and reinforcement design of such structures.
Abstract: Traffic volume and vehicle loads are increasing with time during the bridge service life. Time-dependent reliability theory considers the time-varying effects of loads and resistance, which has been commonly adopted in recent engineering reliability research. The degradation of bridge resistance and increase of vehicle load and frequency varies with time, as described by a nonstationary stochastic model. The gamma stochastic process is adopted to describe the frequency function of vehicle load occurrence to promote the application of nonstationary processes in reliability studies, and time-dependent reliability analyzing approach is proposed for reinforced concrete bridges based on increasing load frequency. The time-dependent reliability equation is modified to account for the verifying effect of historical load information on time-varying resistance by including the coefficient of variation of bridge resistance as a time-associated variable. The above two methods are then used to perform a time-dependent reliability analysis on a prefabricated prestressed concrete bridge. The results show that the structural time-dependent reliability immunes the correlativity of frequency increment of vehicle loads; the time-dependent failure probabilities within 20 to 40 years range from those obtained by proof load tests with load intensities between 31.6% and 36.4% of the initial resistance, indicating higher precision of the modified equation. When the load frequency λ is less than ten times a year, the inspecting time interval is within 35 years, and the historical load intensity is less than 29.1% of the initial resistance, the approach based on load frequency function λ(t) is available. When the load frequency exceeds 36.4% of the bridge’s initial resistance, and the annual growth rate of frequency (γ) exceeds 150%. The RC bridge structure constructed in the marine environment has a higher failure probability within 20 years; thus, extra attention must be paid as corrosion resistance of reinforcements should be enhanced during its design and construction.
Abstract: Hydrogen has the advantages of high energy density, no pollution, and long-term storage. As an important medium for the transformation of energy interconnection, it helps to promote the clean and efficient use of traditional fossil energy, support the large-scale development of renewable energy, and achieve large-scale deep decarbonization. With the excellent responsiveness to intermittent and fluctuating power supplies, proton exchange membrane (PEM) water electrolysis has been a research hotspot in the field of hydrogen production with renewable energy and will be one of the main technical routes for effective hydrogen supply in the future. The high-pressure operation of PEM electrolyzers has been successfully realized and commercialized, considering PEM’s outstanding mechanical strength and gas separation properties. However, due to the water-absorbing properties of the membrane, an important problem in high-pressure PEM water electrolysis (especially under differential pressure conditions and high pressure in the cathode compartment/atmospheric pressure in the anode compartment) is the permeation of hydrogen through the membrane, which affects safety and efficiency. In this article, the research progress of hydrogen permeation in PEM electrolysis was reviewed. First, the theory of permeation was introduced. Second, considering the relationship among the permeation flux, permeability, and partial pressure difference described by Fick’s law, the effects of temperature/pressure, hydration degree of the membrane, and partial pressure difference on hydrogen permeation were reviewed. In the normal operating pressure range (<3.5 MPa) for hydrogen production through PEM electrolysis, the diffusion coefficient and solubility are mainly affected by temperature, and the permeability increases with increasing temperature. The permeability of hydrogen in water is approximately 5–10 times that of a dry film, and the permeability increases with increases in the relative humidity of the membrane. The influence of partial pressure difference in hydrogen permeation shows a linear dependence in permeation cell and quadratic dependence in real electrolysis. The quadratic dependence may be attributed to the convective permeation caused by the increase in membrane water permeability and changes in the water channel. Third, considering the current in real operating conditions of electrolysis, the effect of current density on hydrogen permeation was reviewed. The permeability increases with the increase in current density, which may be attributed to the increase in hydrogen supersaturation in the cathode. At a high current density, the hydrogen concentration within the ionomer at the cathode catalyst particles become higher, and the high concentration gradient causes hydrogen to diffuse from cathode to anode.
Abstract: The existence of fractures has a considerable influence on the mechanical properties of hydropower high and steep rocky slopes. The method to construct an equivalent rock mass calculation model that reflects the distribution characteristics of three-dimensional (3D) fractures is the key to analyze and evaluate the mechanical properties of rock mass. Based on the theory of damage mechanics and statistical strength, this study proposed a new method to calculate the equivalent rock 3D random fractured network model using the 3D rock failure process analysis (RFPA3D). First, based on the Baecher model and Monte-Carlo method, the reconstruction of the 3D random discrete fracture network (DFN) model was implemented in the RFPA3D. Furthermore, an equivalent rock 3D random fractured network model of engineering scale was constructed using the embedded DFN model and through giving different mechanical parameters to fractures and rocks. All the types of load combinations can be applied to the model to realize the analysis of the mechanical properties, such as failure process, deformation, and the strength of the 3D random fractured rock mass. The rock mass downstream of the dam site area of the left bank slope of the Lianghekou Hydropower Station was then taken as the background, and the geometric parameters of the joints in the region were analyzed and studied using the 3GSM software. Moreover, the characteristic values and the distribution types of joint geometric parameters in the study area were obtained. Finally, the accuracy of the 3D random DFN model was verified by taking the fractured rock mass downstream of the left bank slope dam site of the Lianghekou Hydropower Station as an example, and the size effect of the fractured rock mass in the study area was studied. Results show that the representative elementary volume of the jointed rock mass is evaluated as 8 m × 8 m × 8 m, and the corresponding equivalent uniaxial compressive strength and elastic modulus are 25.159 MPa and 19.443 GPA, respectively. Research results provide a new method for the study of the mechanical behavior of the equivalent rock mass.
Monthly, started in 1955 Supervising institution：Ministry of Education Sponsoring Institution：University of Science and Technology Beijing Editorial office：Editorial Department of Chinese Journal of Engineering Publisher：Science Press Chairperson：Ren-shu Yang Editor-in-Chief：Ai-xiang Wu ISSN 2095-9389CN 2095-9389
、
、
、
、
、
、
、
、
、
、
、
、
、
、
、
、
、
