Abstract: To investigate the early hydration and consolidation mechanism of superfine metal tailings powder in the CaO–CaSO4–H2O system, a clinker-free consolidation material based on iron tailings powder was prepared by superfine grinding lime, gypsum, and iron tailings. From 3 min to 24 h, the liquid phase of the hydrated slurry was extracted by centrifugation and high-pressure extraction. The changes in ion concentration and conductivity were tested, and the relationship between them was analyzed. The relationship between the formation mechanism of early hydration products of a consolidated body and the change of liquid phase characteristics is studied combined with the hydration exothermic rate curve, field emission scanning electron microscope (SEM), X-ray diffraction analysis (XRD), thermogravimetry-differential thermal analysis (TG–DSC), and other test methods. The results show that lime, gypsum, and amorphous components, which are on the surface of iron tailings powder, dissolve rapidly within a few minutes after solid-liquid mixing. The concentration of each ion in the liquid phase rises sharply, reaching the peak or saturated state successively in 10–30 min, and then decreases rapidly. After 180 min, the decline rate slows down but continues to decline. The liquid conductivity has a very high positive correlation with the total concentration of Ca2+, OH–, and SO42– ions; The first hydration exothermic peak of the consolidated material is concentrated within 0–15 min, which is mainly caused by the wetting and dissolution of soluble components in the consolidated material and the exothermic behavior of lime hydration; The starting and ending time of the second hydration exothermic behavior is 20–180 min, which is mainly caused by the phase change heat generated by the formation of hydration products. Increasing the grinding time significantly prolongs the termination time of the second exothermic behavior and increases its peak value; The phase analysis of hydration products showed that AFt characteristic peak and C–S–H endothermic peak could be seen in the slurry after hydration for 90 min. Research has proved that the amorphous SiO2 and Al2O3 on the surface of superfine iron tailings powder have the characteristics of rapid dissolution in alkaline solutions, and a hydration reaction can occur when lime and gypsum components are encountered. When the solubility product of hydration products is reached, hydration products AFt and C–S–H will be generated. The two hydration products are interspersed and cemented with each other, and the unhydrated iron tailings particles will be consolidated to form a hardened body. Prolonging the grinding time can effectively increase the system’s amorphous SiO2 and Al2O3 content and the proportion of superfine particles in iron tailings, thus improving the slurry hydration rate. While increasing the amount of the hydration product, the filling effect of the micro powder part is further increased, and the strength of the consolidated body is correspondingly improved.
Abstract: To study the oxidation behavior induced by the spontaneous combustion of accumulated pulverized coal during its storage and transportation within an air leakage circumstance during increased oxidation and temperature and to reveal the mechanism of [BMIM][BF4] ionic liquid inhibiting oxidation and flame retardant characteristics of pulverized coal, this paper used a high-efficiency inhibitor [BMIM][BF4] ionic liquid to inhibit the noncaking coal pulverized coal of the Hongliu coal mine (HL), measuring the critical parameters (critical spontaneous combustion temperature, Tm, and ignition delay time, ti) of pulverized coal spontaneous combustion treated using [BMIM][BF4] at 5%, 10%, and 15% mass fraction. This work also analyzed the influence of [BMIM][BF4] on the heating and self-heating of the pulverized coal. Macroscopic resistance characteristics of [BMIM][BF4] to the pulverized coal were tested under the same high-temperature circumstance (all pulverized coals were ignited). Furthermore, an Fourier transform infrared experiment was used to characterize the microscopic resistance characteristics of the pulverized coal by [BMIM][BF4] to verify the variation of the critical parameters during pulverized coal spontaneous combustion. Results show that [BMIM][BF4] can efficiently inhibit the self-heating reaction of the pulverized coal, increase the Tm and ti values of the pulverized coal, and reduce the risk of pulverized coal spontaneous combustion. Moreover, a higher [BMIM][BF4] mass fraction results in a greater critical parameter of pulverized coal spontaneous combustion. Among them, the Tm of the coal powder treated by [BMIM][BF4] at a 15% mass fraction is 156 ℃, which is +26 ℃ longer than the original pulverized coal redundancy, and the ti is 80 min, which is 32 min later than the original pulverized coal ignition. Under a similar experimental temperature, Ta (Ta>Tm), the center point temperature, oxygen consumption rate, and CO production of pulverized coal treated by [BMIM][BF4] are all lower than those of the original pulverized coal, and the inhibition effect is enhanced with the increase in the mass fraction of [BMIM][BF4]. Meanwhile, the inhibited effect of [BMIM][BF4] is reflected in the strong electronegative fluorine atoms forming strong hydrogen bonds with the hydroxyl hydrogen atoms in coal, dissolving and destroying the hydroxyl groups in the coal and blocking the coal oxygen chain reaction.
Abstract: To improve the positioning accuracy of a mining-induced seismicity monitoring system, reduce the monitoring blind area, and reduce the monitoring cost, based on the distributed idea, this paper proposes a positioning method of mining-induced seismicity based on the smartphone sensor network. First, smartphones used by workers and their families near the mining area were utilized to establish a mobile sensor network. Second, the simulated source points were meshed, and the objective function based on the standard deviation was constructed. An improved firefly optimization strategy was proposed. The inflection point backtracking method and smartphone sensor network exclude the discrete points strategy, namely, EDPS, to reduce the positioning error. Verification is done by the simulation experiment of the mining-induced seismicity location. Experimental results show that under the ideal condition of no arrival time error in the smartphone sensor network, all simulated source points can converge to the source position accurately with a positioning error of less than 1 m. However, compared to the detector, the arrival error of the smartphone is higher, and the positioning error is correlated with the arrival error. When the mobile phone arrival error is ?1.0–1.0 s, the traditional algorithm positioning error is 216 m, which cannot achieve high-accuracy positioning. Researching the relationship between objective function value and positioning error, this work proposes and uses two optimization methods: (1) inflection point backtracking method and (2) EDPS. The absolute positioning error of the algorithm is reduced to 73 m. When the time error is ?0.2–0.2 s, the absolute positioning error is reduced to 17 m, and the positioning accuracy is improved by 76.1%. The location method of the mining-induced seismicity based on the crowdsensing of a phone mobile sensor network provides a new method for mining-induced seismicity monitoring. It can be considered to combine with an underground microseismic system in the future, which is of great significance in saving the monitoring cost and improving the positioning accuracy.
Abstract: Due to the influence of geological structures, various forms of joint structural planes are present in rock mass engineering. The undulating structural planes, such as a torsional fold surface, are unique geological structures. These structures affect the stability of rock masses and cause potential hazards to rock mass engineering. Because of their shape complexity, the research on the fracture and damage constitutive law of rock mass with undulating joints is not thoroughly conducted. Undulating joints with various dip angles were fabricated using three-dimensional printing technology. The uniaxial compression test and digital image correlation (DIC) technology were used to study the mechanical and fracture characteristics of undulating joint specimens. Based on the principle of fracture mechanics, an idea was proposed to use the DIC displacement field for solving the stress intensity factor (SIF: type one KI and type two KII) at the joint tips and to study the damage constitutive law. The results show that the upper limit of undulating joint damage to specimens is determined with 46.6% through the minimum strength analysis. The sensitivity of uniaxial strength to a joint dip angle of undulating joint specimen is greater than that of a straight joint specimen. The fracture initiation occurs near peak stress. The fracture process can be divided into the initiation and synchronous penetration of microcracks on the fracture path. Additionally, the fracture mode shows a combination of multiple tension and shear fractures. The SIF increases with loading at the prepeak stage, and the cracks propagate in shear fracture at the joint left and right tips in the postpeak stage because KII>KI under the same stress. The undulating joint damage to the specimen with the dip angle is in a sinusoidal curve form. The relationships between the total damage coupled by joint and load with strain are all “S” curves.
Abstract: A centrally cracked Brazilian disk (CCBD) specimen subjected to a pair of diametral compressive forces has been widely used to study mixed-mode I and II fractures of brittle and quasi-brittle materials. Reasons for using the CCBD are mainly due to its capability to introduce different mode mixities from pure mode I to pure mode II, the existence of closed-form solutions for fracture parameters, and the simple setup of compressive test. In addition to the diametrical concentrated force loading, the partially distributed pressure loading is also an important loading condition for CCBD specimen tests. Using the weight function method, analytical solutions of stress intensity factors and T stress considering the tangential loading friction for a CCBD specimen that is subjected to four typical partially distributed loads were derived, and effects of the boundary friction and load distribution angle on the fracture parameters were also explored. The results obtained are as follows: (1) For short cracks, geometric parameters YI, YII, and T* of pure mode I and II fractures decrease with an increase in the friction coefficient and load distribution angle. However, for long cracks, an increase in the friction coefficient causes an increase in pure mode-I YI, and an increase in the load distribution angle causes an increase in pure mode-II T*; (2) The influence of the load distribution angle on the fracture parameters is the most significant when the distributed pressure follows a constant function form, while it is the least significant for the case of quartic polynomial pressure; (3) The critical loading angle for pure mode II fractures decreases with an increase in the load distribution angle for short cracks, whereas it increases for long cracks. When the load distribution angle is fixed, an increase in friction can raise the critical loading angle for pure mode II fractures. These results have further improved the research of fracture parameters in CCBD specimens.
Abstract: A finite element limit equilibrium method was proposed based on finite element stress analysis combined with a limit equilibrium condition to analyze the slope stability. The local safety factor defined in the form of shear strength and shear stress ratio in a three-dimensional (3D) space does not consider the sliding direction influence on the calculation results. In this paper, a 3D finite element limit equilibrium method that considers the sliding direction was proposed. This method was different from the limit equilibrium and strength reduction methods and analyzed slope stability through the “true” stress state without reducing the material strength parameters. First, considering the sliding direction in the 3D space, the limit equilibrium condition of a point was proposed on the slip surface in the sliding direction. An equivalent relationship was proved of the slip surface was in the limit equilibrium state, and each point of the slip surface was in the limit equilibrium state in the sliding direction. Then, the main sliding direction and the sliding direction of each point on the slip surface were calculated assuming the rigid body limit equilibrium. Finally, the local safety factor was defined as the ratio of the shear strength to the shear stress projection in the sliding direction. Based on the equivalent relationship of the limit equilibrium state of the 3D slope, the local safety factor was transformed into a global safety factor by applying the integral median theorem. The method is simple to calculate, eliminates the limitation of the slip surface shape of the safety factor defined by the shear stress ratio form, and is reasonable and effective. The verification result of the calculation example shows that the sliding direction assumption of the method is reasonable, and the safety factor is consistent with the result of the strict 3D limit equilibrium method.
Abstract: The type, proportion, and charging method of explosives produce different stress waveforms, which greatly affect rock crack propagation. Because of the complex interaction law between waveform parameters such as the peak value, wavelength, energy, and rise or fall rate, and the limited physical and mechanical test conditions, quantitatively controlling waveform parameters in a blasting test is difficult. Numerical simulation has advantages in revealing the influence law of the stress wave. In this paper, RFPA3D dynamic analysis software was used to simulate the crack propagation in a rock with a prefabricated crack under impact loads, and the effects of the stress wave peak value, energy, rise rate, and fall rate of the stress wave on the rock crack propagation process were investigated. Results show that the rock crack propagation pattern under dynamic loads was affected by the rise rate of the stress wave. The faster the stress wave rose, the more breakages occurred around the hole. For the crack propagation length, the crack grew longer with the increase in the stress wave energy. When the stress wave energy was constant, the crack grew farther with the decrease in the rise rate, but the broken degree around the hole was decreased. The rise rate and the energy of the rising edge of the stress wave affected the radius of the comminution zone. Numerical simulation results revealed the rock crushing mechanism of different stress wave peak values, energies, and rise or fall rates. In a practical engineering blasting operation, to expand the impact range of blasting, extending the action time using a water cannon mud seal or an air column interval charge structure was suggested. In addition, the appropriate type and proportion of explosives were also selected to increase the stress wave’s rise rate to improve the effect of hole edge crushing.
Abstract: Large CaO?Al2O3-type inclusions easily induce fatigue failure of bearing steels, so controlling large CaO?Al2O3-type inclusions is the key to producing high-quality GCr15-bearing steel. Impurity elements in alloys added during refining, slag refining, and slag entrainment during the refining process are the main potential sources for forming large CaO?Al2O3-type inclusions in Al-killed bearing steels. The ferrosilicon alloy is applied to improve the quenching and tempering softening resistance of Al-killed bearing steels. In this work, the effect of the calcium element in ferrosilicon alloys on inclusions in Al-killed bearing steel was studied through laboratory experiments, observations, and thermodynamic calculations. The ferrosilicon alloy mainly consists of the dark silicon and light ferrosilicon phases. The calcium element in ferrosilicon alloys exists as a metal compound at the interface between the silicon phase and the ferrosilicon phase. The total calcium (T.Ca) content in molten steel increases after adding the ferrosilicon alloy and modifying the Al2O3 and MgO·Al2O3 inclusions into CaO?Al2O3-type ones. The size of inclusions in the molten steel decreases with an increase in the CaO content in the inclusions. Large CaO?Al2O3-type inclusions are rarely generated. With the increase of the T.Ca in the molten steel, the T.O in the steel increases, whereas the average size of the inclusions decreases. It was observed that the calcium element in ferrosilicon alloys is not the direct cause for the formation of large size CaO?Al2O3 inclusions in the steel. However, the generated small, solid CaO?Al2O3-type inclusions clog the wall of the submerged entry nozzle, leading to dislodging of the big clogging lump into the molten steel. This lump is one of the reasons for large and irregularly shaped CaO?Al2O3 type inclusions in the steel product.
Abstract: The blast furnace operation profile is closely related to the operation, technical and economic indicators of a blast furnace. A reasonable furnace operation profile ensures high-quality hot metal, low fuel consumption, high yield, and furnace longevity. To guide the blast furnace ironmaking, cluster analysis of the stave temperature is implemented to effectively characterize the changes in the furnace operation profile. The K-Means, TwoStep, and hierarchical clustering algorithms are often used to monitor the blast furnace operation profile. The present study also shows that various clustering algorithms can help manage the blast furnace operation profile. However, the difference among the clustering results from these algorithms remains unclear. Based on the previous research, this paper compared the clustering principles and research status with various algorithms and selected two algorithms of K-Means and TwoStep, which were more applicable and compatible with the algorithm principles. The K-Means algorithm is a typical partition-based clustering algorithm with low time complexity, high clustering efficiency, and good clustering quality. It has been widely used in cluster analysis of the blast furnace operation profile. Additionally, domestic scholars had given effective improvement measures for the shortcomings of sensitivity to the initial center and requirements for data distribution. The TwoStep algorithm was an improved BIRCH (Balanced iterative reducing and clustering using hierarchies) algorithm, which reduced time complexity and can automatically determine the optimal number of clusters. The authors of this article considered the problem that indicators for evaluating the furnace operation profile were multiple and largely overlapped. Principal Component Analysis was introduced based on the TwoStep algorithm. Three new core indicators were generated from the traditional evaluation indicators for the clustering results of the furnace operation profile. For blast furnace operation profile monitoring and management, three core indicators also showed improved performance. In this paper, K-Means and TwoStep were used to cluster the data set. Based on the principles of these algorithms and combined with the Davies?Bouldin index and Dunn index, the clustering results were analyzed to judge the difference between the two clustering algorithms. The analysis based on the sample data and data characteristics selected in this article revealed that the K-Means algorithm achieved better clustering results than TwoStep. This research can provide a powerful reference for selection among various clustering algorithms in blast furnace ironmaking big data analysis.
Abstract: The most important secondary resources of platinum group metals (PGMs) are spent automotive exhaust catalysts, which are called “mobile PGM mines.” Low-temperature iron-capture technology is a promising technology for recovering PGMs due to its high efficiency and low pollution. Because of the content of aluminosilicates and toxic heavy metals (Cr, Ba, Ni, and Mn), the disposal of iron-capture smelting slag is necessary. This paper is devoted to the solidification of heavy metals and the resource utilization of iron-capture smelting slag. Glass-ceramics were made by a one-step method using aluminosilicates as network formers. Heavy metals and CaF2 are employed as nucleating agents in pickling sludge. According to the analysis of differential scanning calorimetry, the glass transition temperature and crystallization temperature of samples are in the range of 650 ℃–700 ℃ and 800 ℃–920 ℃, respectively. The gap between the glass transition temperature and crystallization temperature of samples decreased from 211 ℃ to 150 ℃ when increasing the amount of pickling sludge from 7% to 28% (mass fraction). The devitrification activation energy decreased from 321.8 to 303.5 kJ·mol?1, while the Avrami index increased from 1.7 to 3.7. It demonstrates that pickling sludge can reduce the temperature difference between nucleation and crystallization, which is beneficial in realizing the one-step process. The effects of pickling sludge and heat treatment systems on glass-ceramics were investigated. The diopside phase is the main crystalline phase of glass-ceramics. Nepheline and Magnetite phases were detected when the amount of pickling sludge (mass fraction) reached 28%. The physical properties of the glass-ceramics were improved with the increase in heat treatment temperature and time. When the addition amount of pickling sludge (mass fraction) was 21%, the glass-ceramics prepared by heat treatment at 900 ℃ for 1.2 h had the best properties; namely, the density was 3.04 g·cm?3, the water absorption (mass fraction) was 0.11%, and the Vickers hardness and flexural strength were 742.72 HV and 119.32 MPa, respectively. The Toxicity Characteristic Leaching Procedure (TCLP) leaching standard was met by heavy metals such as Cr, Ba, and Ni in the toxicity test. Glass structure analysis revealed that the pickling sludge increased the nonbridging oxygen content in the base glass while reducing the degree of glass network polymerization, resulting in an enhanced crystallization tendency. The pickling sludge proved to have potential as an inexpensive nucleating agent in the preparation of glass-ceramics with excellent performance. The glass-ceramics with these unique properties are promising to be applied as building materials.
Abstract: To promote the effective utilization of the tuff powder waste, this paper proposes a preparation method for a tuff polymer. The raw material is the by-product in the machine-made tuff-based aggregate production process. NaOH and Na2SiO3 were added to the raw material successively and cured in an airtight condition at 60 ℃. Compared to the production of Portland cement, higher temperature excitation was not necessary, and lower carbon dioxide emissions during the chemical reaction were achieved. Based on the compressive strength, pH value, scanning electron microscopy, X-ray energy dispersive spectrometer, X-ray diffraction spectrogram, and Fourier transform infrared spectroscopy tests on samples with a variety modulus (n(SiO2)/n(Na2O)) of the activator, the mechanism of the modulus of activator influences on the compressive strengths of this tuff polymer was investigated. This work highlights the following: (1) A superior mechanical performance was observed. Results revealed that the optimum modulus was 0.042–0.055 at a range of 0.034–0.150, and the corresponding maximum strength of the tuff powder was 71.33 MPa. (2) The comprehensive microscopic characterization proved the mechanism of strength development. Microscopic characterization results revealed that the alkali activator mainly acted with the surface of tuff powder particles. With the decrease of the modulus of the activator, the dissolution extent of particles increased, and more aluminosilicate was produced, resulting in strength development. When the modulus was below the optimum value, defects such as pore diameter increased, and the contacting area of the polymer on the surface of the tuff particles decreased, resulting in strength deterioration. When the modulus of the activator was 0.150 and 0.080, the strength development occurred between three and seven days. When the modulus of the activator was 0.050, 0.042, and 0.034, the strength development mainly occurred between 7 and 14 days. The pH value variety of the leaching solution generally corresponded to strength development. The increased strengths are attributed to the consumption of OH? in the polymerization and polycondensation stages. Meanwhile, a pH value that is too high may result in depolymerization of the production in the polymerization and polycondensation stages. In addition, the electrostatic repulsion increased, and therefore the strengths of the tuff polymer decreased.
Abstract: Natural flyers use muscles, bones, and other structures in coordination to attain agile and nimble flight performance. They can fly in various complex environments through different flight modes, such as flapping, hovering, and gliding. The high-lift mechanism on flapping-wing flights plays a fundamental role in bionic flapping-wing aerial vehicle design. Bionic flapping-wing aerial vehicles operate in modes that mimic birds and insects. They rely on flapping wings to generate the lift and thrust required for flight. With the advantages of good concealment, high energy efficiency, and low flying noise, flapping-wing aerial vehicles have great potential in performing civil and military tasks. In the civil field, they can go deep into different complicated, unknown environments and perform environmental monitoring, rescue missions, and other special tasks that are difficult for human beings to complete. In the military field, they can replace human beings to complete covert reconnaissance and search tasks and play an important role in maintaining regional stability and preventing military invasions. Because of their broad application prospects, flapping-wing aerial vehicles have drawn considerable attention from researchers. Inspiration from the distinct features of natural flyers has influenced flapping-wing aerial vehicle design. Many attempts have been made to improve flapping-wing aerial vehicle performance. Because flapping-wing aerial vehicles have a small payload, they carry large-capacity batteries with difficulty, resulting in limited endurance. Under limited energy, the endurance time of flapping-wing aerial vehicles can be effectively increased by reducing energy consumption. An important research direction of flapping-wing aerial vehicles is to improve endurance by developing high energy density batteries and bionic design. Starting from bionic mechanism analysis, mechanism optimization design, and control strategy research, designers and engineers have conducted much research on the energy consumption of flapping-wing aerial vehicles, and achievements have been made frequently. However, their flight efficiency is still far from their natural counterparts. Many challenges remain in the bionic mechanism, fabrication, and autonomous flight of flapping-wing aerial vehicles. This paper summarizes the research progress on the energy consumption of bionic flapping-wing aerial vehicles. We discuss the main components of flapping-wing aerial vehicle energy consumption. Then, we analyze the effects of static parameters, dynamic parameters, and control strategies on the energy consumption of flapping-wing aerial vehicles. The energy consumption improvements of flapping-wing aerial vehicles with different parameter designs are compared. Finally, we propose measures to reduce energy consumption and discuss future research directions.
Abstract: Inspired by the biological organs in nature, many robots have been developed and successfully applied by imitating the characteristics of different animals. The design inspiration of a soft robot comes from the bending movement of an elephant trunk and an octopus arm. They can use their soft structure to effectively adapt to a complex and changeable environment and complete various complex operations. Their excellent flexibility and bending have attracted the interest of researchers. Continuing breakthroughs in materials science, chemistry, control, and other disciplines, and in the observation and modeling of soft organisms such as the octopus, worm, and starfish have led to a new robot research direction—soft robot. Soft manipulators are made of soft materials and can be used to accomplish tasks that rigid manipulators cannot accomplish, such as detecting in an unstructured environment, grasping fragile objects, and safer man-machine cooperation. Many countries are investing in this area; soft manipulators of various shapes and functions have been designed, using different manufacturing materials and driving, modeling, and control methods, exhibiting the uniqueness of each device. The driving ways of the soft manipulator are different according to their task purposes. This paper first studies three main driving ways of the soft manipulator: (1) tendon driving (tendon driving), (2) shape memory alloy driving (SMA driving), and (3) pneumatic driving (pneumatic driving). Modeling and control methods of soft manipulators in different driving modes are then studied. Finally, the development of soft manipulators is summarized and prospected from three aspects: (1) driving way, (2) modeling methods, and (3) control methods.
Abstract: Smart legal contract (SLC), as a form of smart contract in accordance with the law, has attracted extensive attention in recent years. However, the conclusion procedure of an SLC still lacks effective technical methods to make it conform to the current legal regulations, which directly affects the legitimacy of the SLC contract. Therefore, this paper starts with the relevant legal regulations of contract conclusion and introduces the idea of contract normative pattern (CNP), which is a reusable form, model, or template for contract conclusion. Based on these regulations, we propose a standardized conclusion procedure of smart legal contracts. This procedure includes four stages: establishment, deployment, conclusion, and deposit to meet the current legal regulations for the conditions of establishment in the written contracts. Meanwhile, a written form of interactive interface is proposed to satisfy the two stages of “negotiation” and “acceptance” in the CNP. The negotiation stage supports the parties to repeatedly negotiate and determine the pending contents in the CNP, and the acceptance stage is to activate the behavioral attribute by actively triggering predefined algorithms, such as registration and signature. In addition, the syntax of contract conclusion, including parties’ negotiation and acceptance, is introduced in the SLC language, SPESC, to adhere to the “negotiation-acceptance” mechanism in the conclusion procedure. In this paper, we design three blockchain’s transaction structures to store interactive data during party registration, signature, and clause execution. Finally, considering the sales contract as an example, we analyze the legitimacy of the proposed conclusion scheme based on three aspects: negotiation confirmation, acceptance confirmation, and deposit legitimacy. This paper will provide a legal basis for the conclusion procedure of an SLC and promote better achievement of legalization of a smart contract.
Abstract: The vehicle suspension system is not only used to consume the vibration energy transmitted from the ground to the vehicle body but also provides good handling stability for the vehicle. This can be a challenging tradeoff, especially for vehicles with a high center of gravity and heavy loads, such as trucks and SUVs. These vehicles are prone to large load deviations during emergency steering, causing the vehicle to roll over. The emergence of a hydraulically-interconnected suspension (HIS) could effectively maintain the vehicle body’s stability. As a unique hydropneumatic suspension, the HIS system has prominent nonlinear damping characteristics and can decouple the bounce motion and roll motion of the vehicle. This increases the vehicle’s roll stiffness without affecting the vertical rigidity of the vehicle, thereby substantially reducing the possibility of rollover accidents. This paper introduces a novel energy-harvesting hydraulically-interconnected suspension (EH-HIS), which has the dynamic characteristics of the HIS and can even harvest the vibration energy that is traditionally dissipated into heat using the oil shock absorbers. Working principles of bounce motion, roll motion, and pitch motion of the EH-HIS system have been analyzed. A mathematical model of the system was established based on the pressure drop principle and validated by a bench test. Damping characteristics and the energy harvesting capability are studied via simulations. Results show that the EH-HIS has considerable asymmetric and tunable damping characteristics that can meet the allowable range of most passenger vehicles. When the external resistance increases from 5 to 25 $ \mathrm{\Omega } $, the corresponding equivalent damping coefficient decreases from 7558 to 3134 N?s·m?1. The energy harvesting capability analysis shows that maximum energy harvesting power is achieved when the external resistance is equal to the internal resistance. Furthermore, the average harvesting power can reach 875.9 W under the excitation of 2 Hz (frequency) 30 mm (amplitude).
Abstract: Microscale electronic devices offer promising application capabilities in various fields, such as information, aeronautics and astronautics, energy, and chemical engineering. Specifically, the exceptional performance of high-integration and high-frequency devices leads to a significant heat flux enhancement. Conventional air and liquid cooling techniques struggle to meet the efficient heat dissipation requirement, affecting the reliability and safety of microscale electronic devices significantly. Many types of passive heat transfer process intensification strategies have been proposed recently, such as those based on adjusting element structure, surface roughness, surface hydrophobicity, and channel dimension. However, these passive strategies increase flow resistance to some extent, limiting their applicability. Ultrasound has several unique characteristics, including low cost, simple operation, flexible control, strong penetrability, and good biocompatibility. These characteristics make ultrasound a promising candidate for use in national defense, biomedical theranostics, agriculture, food, the environment, and materials. Researchers have paid considerable attention to the integration of ultrasound with heat transfer techniques, which has gradually become one of the key research directions for heat transfer enhancement. This paper aims to provide a comprehensive overview of the research progress on the intensification of the ultrasound-excited heat transfer process. First, the principles of ultrasound-excited heat transfer enhancement are introduced, and two major acoustic phenomena, acoustic cavitation and acoustic streaming, are highlighted. Theoretical and experimental studies on ultrasound-excited single-phase gas convection, single-phase liquid convection, pool boiling, and flow boiling heat transfer process intensification are then summarized, and typical studies in these fields are categorized and discussed in depth. Finally, current challenges and future directions are presented, such as simple numerical simulation models that should consider multiphysics and multidomain constraints for accurately representing the practical heat transfer process, lack of sufficient characterization methods that should develop new and integrated visualization techniques for precisely monitoring heat transfer performance, limited focus on other acoustic phenomena other than acoustic streaming and acoustic cavitation that should provide a comprehensive analysis for revealing the in-depth heat transfer mechanisms, and few attempts and pathways to industrialization that should demand researchers from different disciplines to work together and collaboratively. It is hoped that this review article will not only reveal the unprecedented functionality of ultrasound for heat transfer enhancement but will also provide critical guidelines for the rational and practical design of robust ultrasound heat transfer platforms.
Abstract: When compared with the traditional refrigeration method that uses a refrigerant as a working medium, thermoelectric refrigeration is a new type of solid-state active environmental protection refrigeration method. This method is based on the Peltier effect of semiconductor thermoelectric materials, which directly converts electrical energy into a temperature gradient. Thermoelectric refrigeration has the advantages of simple structure, compact structure, rapid cooling, and accurate control of refrigeration temperature. When compared with a single-stage thermoelectric cooler, a two-stage thermoelectric cooler can ensure greater cooling temperature difference and efficiency. A heat pipe is a heat transfer component that uses liquid-phase transition to transfer heat. It has good isothermal stability, efficient thermal conductivity, and small size. For good heat dissipation capacity of heat pipes and higher cooling temperature difference in two-stage thermoelectric coolers, a two-stage thermoelectric chiller model based on heat pipe heat dissipation is proposed. Based on finite-time and nonequilibrium thermodynamics, various thermoelectric effects, including the Thomson effect, are considered. The effects of working current, distribution ratio of thermoelectric elements, and heat pipe geometric parameters (heat pipe outer diameter, evaporating section length, and wick thickness) on the device-cooling load, coefficient of performance (COP), and extreme cooling temperature difference are analyzed by the numerical simulation method. Under a certain total logarithm constraint of the thermoelectric unit, the cooling load and the COP are taken as the targets. The working current and distribution ratio of thermoelectric elements are used as the variables to optimize device performance. The influence of key parameters on the optimal variables and optimal performance is analyzed, and the optimal interval of the coordinated cooling load and COP is obtained. By optimizing the distribution ratio and current of thermoelectric elements, the cooling load and COP of the device significantly improved. When ${\Delta }{T}\text{}\text{=}\text{}\text{20?K}$, x = 0.6, I = 2.5 A, the optimized cooling load and COP reach 23.42 W and 1.53, respectively, which are 12.11% and 218.75% higher than those before optimization.
Abstract: Sintering is one of the most important processes in iron and steel production, which provides stable sinter for the blast furnace. However, it also produces pollutants, such as sulfur dioxide (SO2), nitrogen oxide (NOx), and dioxins, which cause serious environmental problems. With the increasing pressure of environmental protection, pollutant reduction has become one of the bottlenecks restricting the development of iron and steel enterprises. Using a vanadium–tungsten–titanium catalyst can effectively reduce NO and dioxin in the sintering flue gas, while the potassium salt contained in the flue gas will reduce the activity of the catalyst. In this study, the fresh vanadium–tungsten–titanium catalyst was deactivated by the wet impregnation method in the laboratory. Effects of three potassium salts (K2SO4, K2O, and KCl) loaded on the surface of the catalyst on its denitration and dioxin removal activities were investigated. The regeneration performance of the deactivated catalyst was studied by the water washing and acid pickling process. Results confirmed that activities of denitration and dioxin removal were reduced by different potassium salts, and the order of reduction follows the sequence: KCl>K2O>K2SO4. The deactivation mechanism of the catalyst mainly includes physical deactivation and chemical deactivation. Physical deactivation is mainly caused by the deposition of potassium salts on the surface of the catalyst, blocking its pores. Chemical deactivation mainly refers to the interaction between the potassium salts and the active component on the catalyst’s surface, which inactivates the surface’s active site, weakens its oxidation reducibility, and reduces the number of acid sites on the surface, thereby decreasing the denitration and dioxin removal activities of the catalyst. Regeneration experiment results showed that water washing could restore the denitration activity of the catalyst. Acid pickling would lead to the loss of active substances on the surface of the catalyst. However, neither water washing nor acid pickling could effectively restore the dioxin removal activity of the catalyst. Finally, the poisoning mechanism of different potassium salts on the vanadium–tungsten–titanium catalyst was proposed.
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
