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A water model experiment and a transient 3D numerical model were designed and implemented to quantitatively evaluate the flow-induced erosion behavior of the refractory lining in a continuous casting tundish. A relationship between the erosion rate and flow characteristic parameters was proposed and experimentally verified. Boric acid tablets were used in the water model experiment to determine the flow-induced erosion rate, and the numerical model defined the two-phase flow pattern. The results indicate that the impacting and rubbing effects caused by the fluid flow can be quantitatively characterized by the turbulent kinetic energy and wall shear stress. The proposed empirical dependence describes the erosion rate of the boric acid tablet with acceptable accuracy. The most serious erosion occurs inside the turbulence inhibitor, and the erosion rate sharply drops and steadily reduces with the water flow outside the turbulence inhibitor. The influence of casting speed on the refractory erosion rate is also quantitatively analyzed using the developed model with the introduction of the proposed correction.

Channel attention mechanisms have attracted more and more researchers because of their generality and effectiveness in deep convolutional neural networks(DCNNs). However, the signal encoding methods of the current popular channel attention mechanisms are limited. For example, SENet uses the full-connection method to encode channel relevance, which is parameters-costly; ECANet uses 1D-Convolution to encode channel relevance, which is parameter fewer but can only encode per k adjacent channels in a fixed scale. This paper proposes a novel dilated efficient channel attention module(DECA), which consists of a novel multi-scale channel encoding method and a novel channel relevance feature fusion method. We empirically show that different scale channel relevance also contributes to performance, and fusing various scale channel relevance features can obtain more powerful channel feature representation. Besides, we widely use the weight-sharing method in the DECA module to make it more efficient. Specifically, we have applied our module to the real-life fire image detection task to evaluate its effectiveness. Extensive experiments on different backbone depths, detectors, and fire datasets have shown that the average performance boost of DECA module is more than 4.5% compare to the baselines. Meanwhile, DECA outperforms other state-of-art attention modules while keeping lower or comparable parameters in the experiments. The experimental results on different datasets also shown that the DECA module holds great generalization ability.

The new route for recycling fly ash was proposed to prepare SiC reticulated porous ceramics (SRPCs) with high strength and increased efficient filtration for molten metal filtration. The effects of fly ash on the rheological characteristics, microstructure evaluation and wetting behavior between SRPCs and molten metal were investigated. It was found that the fly ash was beneficial to thixotropic property of SiC slurry when its content was less than 30 wt%. Furthermore, fly ash in SRPCs was completely transformed into mullite with needle-shape at 1300 °C, forming a porous structure containing micro pores and windows. SRPCs containing 20 wt% fly ash exhibited a higher strength because of the improved rheological properties of SiC slurry and the optimized microstructure in skeleton. In addition, the added fly ash in SRPCs could increase the contact angle between skeleton substrate and molten metal via microporosization of skeleton, thus exhibiting the potential ability to improve the filtration efficiency.

The formation and removal of exogenous inclusions in a real-size two-strand tundish is simulated by the proposed unsteady 3D comprehensive numerical model of the respective fluid-structure interaction, which takes into account the impacting and washing effects on the refractory wear. A large eddy simulation is employed to describe the molten steel vortex flow. Thus, the thermal profiles of the molten steel and refractory lining are constructed. One-way coupled unsteady Euler-Lagrange approach is adopted to estimate the detachment and motion of the exogenous inclusion. The inclusion’s Reynolds number is utilized for evaluating the inclusion separation at the refractory lining after formation and at the upper surface of the molten steel. At a 1.2 m/min casting speed, 49 and 38 pct of exogenous inclusions are created at the turbulent inhibitor inner bottom and long nozzle inner wall, respectively. In contrast, only 13 pct of new inclusions are produced at all other inner walls. About 80 pct of newly generated inclusions are then trapped by free surfaces, 78 pct of which are removed at the first free surface. The initial diameter of exogenous inclusions ranges from 13 to 48 μm. The removal ratio of exogenous inclusions in the tundish first grows from 61 to 80 pct, with the casting speed rising from 1.0 to 1.2 m/min and then drops to 63 pct after the further casting speed rise to 1.4 m/min.

Reusable electronics have received widespread attention and are urgently needed. Here, nanocellulose-based liquid metal (NC-LM) printed circuit has been fabricated by the evaporation-induced transfer printing technology. In this way, the liquid metal pattern is embedded into the nanocellulose membrane, which is beneficial for the stability of the circuit during use. Besides, the NC-LM circuit is ultrathin with just tens of microns. In particular, the finished product is environmentally friendly because it can be completely dissolved by water, and both the liquid metal ink and the nanocellulose membrane can be easily recollected and reused, thereby reducing waste and pollution to the environment. Several examples of flexible circuits have been designed to evaluate their performance. The mechanism of evaporation-induced transfer printing technology involves the deposition, aggregation, and coverage tightly of the nanosized cellulose fibrils as the water evaporated. This study provides an economical and environmentally friendly way for the fabrication of renewable flexible electronics.

A transient three-dimensional comprehensive numerical model was developed to clarify the effect of electro-emulsification on sulfur mass transfer during the electroslag remelting process of rejected electrolytic manganese metal scrap. The magnetohydrodynamic thermal two-phase flow and solidification behavior were numerically clarified. The kinetics module was established to assess the sulfur mass transfer rate between molten manganese metal and molten slag. Furthermore, variations of the alternating current (AC) magnitude and direction were taken into account. A reasonable agreement between the experimental and simulated results was observed. The surface area of molten droplets was shown to enlarge and it regularly fluctuates under the Lorentz force action. At the constant frequency of 50 Hz, the desulfurization rate rises from 54.7 to 71.0 pct when the AC root mean square (RMS) value of the AC is increased from 3000 to 4000 A, while at the constant AC RMS value of 3500 A, it dropped from 63.4 to 58.5 pct with the frequency increases from 5 to 500 Hz.

Thermoelectric generation (TEG) is one of the most effective technologies converting heat directly into electric power. In this paper, a nearly kilowatt class TEG system mainly based on radiation h...

Shape transformable materials that can respond to external environments have attracted widespread interest over the fields of soft robotics, flexible electronics, and tissue engineering. Among stimuli-responsive materials, liquid metals exhibit rather unique characteristics of versatile morphological changes upon diverse stimuli, including chemicals, electrical field, and mechanical force, etc. Herein, a superfast (few milliseconds), large-scaled (13.8% deformation increase), and fierce (cracks formation) transformation of liquid metal microdroplets (LMMs) with strong impulse expanded force due to liquid-solid phase transition in a dual fluid system composed of LMMs and aqueous solution is reported. When subject to low-temperature stimulus, LMM would transform from ellipsoidal shape to amorphous shape induced by thermal stress, driving the shape morphing. Furthermore, the phase changes of LMMs as well as the formation of surrounding ice crystals are proven to be responsible for this phenomenal behavior. The densification of ice crystals is demonstrated to play a significant role in the transformable behavior. In particular, these nonconductive LMMs in aqueous solutions are discovered to turn into conducive materials with an impedance change of about 10

SiC reticulated porous ceramics (RPCs), as the key functional components, are widely applied in field of molten-metal filtration. However, the hollow struts with triangular tips caused by burnt out of polymer foam reduced the strength of SiC RPCs, which limited their engineering application. Aiming to reveal the effects of template strut morphology on the mechanical performance of SiC RPCs, templates with triangular, square and circular cross sections were designed by additive manufacturing. Subsequently, SiC RPCs with varied strut structures were prepared by slurry immersion, followed by sintering at elevated temperature. The blunt of template strut improved the mechanical property of SiC RPCs, samples with circular hollow struts showed the highest crushing strength and strain than that of triangular and square hollow struts. From the results of simulation calculation, triangular hollow struts led to the significant stress concentration in the connection of struts and their middle parts, while the smaller stress uniformly distributed in the whole SiC skeleton as hollow struts became circle, thereby the improved mechanical properties were obtained in SiC RPCs.

As the key component for porous media burner, the sufficient strength of SiC reticulated porous ceramics (RPCs) is necessary due to the scour of hot flue gas. However, SiC RPCs prepared with template replica method often exhibited serious oxidation and low strength when the foam was burnt out. In the present work, a sol-coated Al powder with high hydration resistance was introduced into the silicon carbide slurry to promote mullite formation in SiC skeleton, meanwhile reduce the SiC oxidation ratio of sample during the heat treatment. Firstly, the silica-sol coated Al with uniform silica-sol was successfully prepared via dip coating to improve the ability of hydration resistance of Al powder. Furthermore, sol-coated Al with spherical morphology improved rheological properties of silicon carbide slurry, including viscosity and rheological behavior. In addition, the evolution mechanism of sol-coated Al in SiC RPCs was revealed. The AlO2(g) and AlO(g) was first formed in the system, thus significantly reducing the SiC oxidation ratio in SiC RPC. The partial pressure of AlO(g) increased with the sintering temperature, the needle-shaped mullite formed at 1300 ○C when it dissolved in the microsilica, while lumpy mullite formed as SiC was the silica source in SiC RPCs. The addition of sol-coated Al was beneficial to optimize the microstructure of SiC skeleton, resulting in higher compressive strength of SiC RPCs.

To investigate the fracture behavior of cement-bonded corundum castables, various cement contents and pre-treating temperatures have been comparatively studied using the wedge splitting method and the digital image correlation technique. The results show that the microstructure enhances the mechanical properties, so the fracture energy and the maximum load as well as the fracture modes are affected correspondingly. The castables demonstrate the highest fracture energy and maximum load at 1600 °C with cement content of 10 wt% due to an appropriate amount of CA6. At the temperatures of 110 and 1100 °C, the crack propagation within the matrix and along the interface are dominated whereas within the aggregates significantly increased at 1600 °C, leading to the brittleness of materials. However, increasing the cement content can reduce their brittleness, caused by the maximum strain in thex-direction, largest length of the main crack, and high ratio of crack propagation in the matrix.

The cement-bonded corundum castables are often subjected to great temperature gradient in the service process of purging plugs for refining ladle. The mechanical properties of such castables are of particular interest in the serviceability and the safety of purging plug, which are significantly influenced by the microstructures including the amount, size and morphology of materials. The reported cement contents in compounds of purging plugs are generally low or ultralow, which inevitably limits the adjustable range of the mechanical properties enhancement by regulating their microstructures. In the present research, a serial of comprehensive experiments have been carried out, including the high cement contents (10–15 wt%), so as to further understand the role of cement content on the microstructural evolution and mechanical properties of castables. It is found that the phase compositions and microstructure can be optimized through adjusting the cement content in corundum castables. When the cement content is below 10 wt%, the hexagonal flake CA6 grains are platelet-shaped both in the matrix and at the border of the aggregates, their amount and size increase and distributions are more uniformly with cement content. When the cement content is above 10 wt%, small amount of granular crystals CA2 are detected in matrix, and CA6 crystals transform to equiaxial morphologies after cement content of 10 wt%. This research also provides quantitative relationship between the mechanical properties of the castables and the cement content. Castables with cement content of 10 wt% contain most hexagonal flake CA6 crystals, so that they have the highest CMOR and HMOR after heating at 1600 °C. However, CMOR decreases after cement content of 10 wt% due to the porosity and volumetric expansion from the formation of in-situ CA6 and CA2.

In order to further optimize the working performance of micro-cylindrical combustor, the combustion chamber of the micro-cylindrical combustor is inserted in a rectangular rib. Extensive numerical investigations are conducted to compare the exergy efficiency of non-ribbed and rectangular-ribbed micro combustors under various hydrogen mass flow rates and hydrogen/air equivalence ratios. Moreover, the effects of dimensionless rib positions and heights on the exergy efficiency of micro-cylindrical combustor are also widely investigated. Results suggest that the exergy efficiency of the rectangular-ribbed micro combustor is significantly higher than that of the non-ribbed micro combustor under different inlet conditions. Moreover, the exergy efficiency of the rectangular-ribbed micro combustor is significantly affected by the dimensionless positions l. The optimum dimensionless l is increased with the increase of hydrogen mass flow rate. This work offers us significant reference for optimizing the micro combustor in energy utilization.

As it is important to achieve higher combustion efficiency for applications of micro-cylindrical combustor, the multi-factor impact mechanism on the combustion efficiency of a hydrogen-fuelled micro-cylindrical combustor is investigated in this work. Firstly, six factors such as hydrogen/air equivalence ratio, inlet velocity, inlet temperature, wall thermal conductivity, wall emissivity and convective heat transfer coefficient of outer wall and five levels of each factor are determined. Orthogonal design table L25(56) is introduced to arrange cases. Secondly, grey relational analysis is adopted to investigate the effects of the six factors on combustion efficiency. Finally, the results of grey relational analysis are validated by analysis of variance. Based on grey relational analysis and analysis of variance, it is determined that the impact ranking from the largest to the smallest is hydrogen/air equivalence ratio, inlet velocity and inlet temperature, followed by the other three factors. The impact of wall thermal conductivity, convective heat transfer coefficient of outer wall and wall emissivity is considered to be equal due to their difference of impact on combustion efficiency is very small. This work provides us significant reference for optimizing combustion efficiency of a hydrogen-fuelled micro-cylindrical combustor.

In order to reduce the entropy generation of premixed hydrogen/air flame in the micro combustion chamber, the combustion chamber of the old micro reactor is modified by gradually varying the diameter of the combustion chamber. Extensive numerical investigations about the entropy generation of premixed hydrogen/air flame in old and modified micro reactors are conducted under various hydrogen mass flow rates, hydrogen/air equivalence ratios, solid materials and inlet/outlet diameter ratios. Results suggest that the modified micro reactor has lower total entropy generation than that of the old micro reactor. This is attributed to that the temperature gradient of the burned gas in the modified micro reactor is lower than that in the old micro reactor after chemical reactions. Finally, the largest descent percentages of total entropy generation are achieved under various conditions, which provide significant reference values for hydrogen energy usage under micro scale combustion.

In order to obtain the real solution of the fracture parameters for the wedge-splitting test, numerical simulation and inverse algorithm have been designed to estimate the maximum tensile stress and fracture energy of cement-bonded corundum refractory. The experimental and simulated curves have been systematically compared to produce the bilinear model of cohesive zone material with the inverse algorithm of nonlinear least-squares solution being the most suitable for the simulation of the wedge-splitting test. Furthermore, the inverse simulation procedure has been applied to specimens of various heating temperatures and cement contents. Consequently, the fracture energy and the maximum tensile stress initially decrease and then increase with the temperature. Furthermore, the fracture energy has the tendency of increasing with the cement content, and the maximum tensile stress has the highest peak at the content of 10 wt.%. Additionally, the cement-bonded corundum refractory presents higher brittleness after high-temperature heating (1400°C) or with the cement content of 10 wt.% at 110°C.

Water changes natural seepage in the surrounding geological environment and weaken rock mass of valley during reservoir impounding, which result in large time-dependent deformation of foundation of dam. A nonlinear creep damage model considering water effect is proposed by taking into account the influence of pore pressure on the spherical stress tensor and yield surface. The elastic-viscoelastic model is consisted of a spring and several cascaded Kelvin models. The model is implemented in the ABAQUS user material subroutine. The accuracy of the model is verified by the triaxial creep test of saturated sandstone and dry sandstone. Then it is applied in the valley contraction analysis during impounding of Xiluodu high arch dam.

This paper reports on a novel phase change material macrocapsule for thermal energy storage, which can be dynamically and repeatably remodeled as needed to a complicated shape with large-scale deformation. In addition, it effectively eliminates the stress mismatch, induced by the volumetric expansion (or shrink) of the phase change material during melting (or solidification), through the self-adaptative deformation of the coated flexible shell. The shape-remodeled macrocapsule, consisting of octadecanol as the core and the silicone elastomer for encapsulation, was prepared through a cast molding method. The high-concentration microparticles of low-melting Bi-In-Sn eutectic alloys were embedded into elastic shell for significantly enhancing its latent heat storage and heat conductivity. The prepared macrocapsule has a high latent heat density of 210.1 MJ/m3, which of the contribution from the shell is about 20%. The thermal conductivity of the macrocapsule core reaches to 1.53 W/m·K with a 428% increase compared with pure octadecanol. The flexible shell attains a high thermal conductivity of 1.98 W/m·K with an 890% increase compared with pure silicone, which also remains a high stretchability with 432% strain. The performance of shape remodeling, energy storage capacity, and heat charging and discharging rates of the macrocapsule were demonstrated in detail. The applications of the prepared macrocapsule as thermal management for the flexible electronic devices and the thermal storage for thermoelectric energy harvesting were also investigated. The present study opens the way for further development of elastic phase change material capsule applications in energy storage systems and thermal control engineering.

Background: Accessibility is considered as an important indicator for the public transit service level. Transit accessibility is generally evaluated by its distance to transit access points such as bus stops and metro stations, and methods of measuring the access distances to transit points have been relying heavily on geographic data of transit facilities, built environments and pedestrian routes. Data collecting and analyzing are tedious for researchers in conventional approaches. As the application of cloud computing is on the rise, open services provided by Google Cloud Platform may simplify the procedure of accessibility measurement if the outputs of the open computing services could be validated. Aims and Objectives: This paper aims to develop a method of measuring public transit accessibility based on Google Direction API rather than local data analyzing. A mechanism of API (Application Program Interface) probing is introduced. In a case study, the metropolitan area of Beijing was sliced into gridded spaces, with transit access distance of each cell space calculated by Google Direction API. The access distances in the API feedbacks were compared with transit access numbers in each cell area in order to validate the method with their correlation coefficient. Results and Conclusion: It was found that Google Direction API generally gave shorter access distances in cell areas with more public access points. The conclusion is that open cloud services such as Google Direction API may serve as alternative solutions to public transit accessibility measurement. Transit researchers and agencies may take advantage of such open API services to avoid the tediousness of collecting and processing geographic data sets on transit facilities.

This study proposes a linear magnetic gear (LMG). Unlike conventional LMGs, the proposed one purposely uses high-temperature superconducting (HTS) bulks replace permanent magnets (PMs). The high-speed mover of the magnetic gear is connected to the secondary of the linear permanent magnet generator (LPMG), which constitutes a direct-drive wave power system that converts wave energy into electrical energy. First, the LMG structure is presented according to the principle of magnetic field modulation, and the authors briefly analyzed the number of pole pairs of inner, outer, and ferromagnetic modulators. Second, they also established a finite element analysis model to analyze the performance of magnetic gear, including magnetic field distribution, radial air gap magnetic flux density, and force characteristic. An LMG with HTS bulks not only increased the radial air gap magnetic flux density but also improved the speed of LPMG. In conclusion, this experiment verifies the efficacy of direct-drive wave power take-off system and effectively converts wave energy into electrical energy.

For cooling system, liquid metal (LM) have attracted many attentions as an excellent coolant. In this study, we propose a superior liquid metal cooling blade dissipator with twin stage electromagnetic pumps (EMPs), whose thinnest dimension was only 4 mm. The coupling model is utilized to solve the distribution of Lorentz force and the field of velocity and temperature simultaneously in the COMSOL multi-physics software, and the validity of numerical model was verified by experimental data. It is demonstrated that the efficiency of twin stage EMPs was obviously higher than that of single stage of EMP at the same input power theoretically. The Nusselt number at the heater is calculated under the different driven current and heating power. It has been found that there was no obvious change for Nusselt number. Also it can be concluded that the superior property of suppressing thermal shock and high performance-cost ratio were presented.

The three-layered struts within SiC reticulated porous ceramics (RPC) were designed to improve the thermal characteristics and thermal shock resistance of porous burner. The effects of strut structure and its composition on the flame stability limits, flame temperature and thermal damage resistance of porous burner were investigated. The results showed that three-layered struts consisted of continuous mullite coating, middle layer of SiC skeleton and inner layer of reaction-bonded mullite after sintering at 1450 °C. Compared to porous media with single layer, RPC with three-layered struts possessed the combined effects of high thermal conductivity and heat radiation because of its middle layer of SiC skeleton and in-situ formed mullite coating. The three-layered struts in porous media extended the flame stability limits and increased the flame temperature of porous burner. Furthermore, the formation of three-layered struts eliminated strut defects and formed continuous mullite coating, thereby significantly improving the oxidation resistance and thermal shock resistance of RPC, which increased the service life of porous burner.

The soot formation and evolution characteristics in premixed methane/ethylene-oxygen-argon flames are studied experimentally and numerically. The soot particles sampled with an in-situ probe sampling method are measured for different light hydrocarbon fuels (i.e., methane and ethylene), heights above the exit surface of the burner (HAB), equivalence ratios, ϕ and Reynolds numbers of flame jet, Rej. A novel stochastically weighted operator splitting Monte Carlo (SWOSMC) method coupled with detailed soot model is developed to simulate the evolution of soot particle size distribution (PSD) in premixed methane/ethylene-oxygen-argon flames. The flame temperature decreases while geometric mean diameter of soot particles increases with increasing ϕ. With increasing ϕ, condensation and nucleation processes are enhanced in methane flame while coagulation and nucleation processes are enhanced in ethylene flame. Hence, these processes lead to an increase of total soot number concentration for methane flame but a decrease for ethylene flame. A distinctly different variation trend of the normalized total number density of soot particles for methane flame along with HAB can be found for low and high studied Rej ranges. Similarly, a distinctly different variation trend of geometric mean diameter of soot particles for ethylene flames along with HAB can also be found for low and high studied Rej ranges. The numerical simulation results obtained via the fully validated SWOSMC method show excellent agreement with experimental results in the present study. Consistent with the experimental results, the numerical simulation results show that both condensation and nucleation rates increase and become dominant processes in the methane flame while coagulation rate increases in ethylene flame with increasing ϕ. Meanwhile, the simulated nucleation and coagulation rates along the centerline of both methane and ethylene burner flames are reversed with increasing Rej. The present study not only verifies the competition phenomenon among different soot dynamic processes but also shows that this competition can be reversed for different Rej ranges. These results show that the soot formation and evolution characteristics in the studied premixed methane/ethylene-oxygen-argon flames are determined by competition among different soot dynamic processes.

BiCuSeO is a kind of promising oxide-based thermoelectric material with special natural superlattice structure. Herein, the effects of Er doping and modulation doping on the thermoelectric properties of BiCuSeO have been investigated. The results indicate that Er doping can tune the Fermi level, widen the band gap, reduce the energy offset between the heavy band and the light band, and then greatly improve the electrical conductivity, power factor and ZT. Modulation doping based on Er doping can increase carrier concentration and power factor significantly while maintaining high carrier mobility. Meanwhile, due to the special heterostructure of the modulation doping sample, the phonon scattering is greatly enhanced, and the corresponding lattice thermal conductivity is significantly reduced. Finally, the maximum ZT value reaches 0.99 for the modulation doped Bi0.92Er0.08CuSeO bulk at 873 K, which was ~1.8 times as that of the pristine BiCuSeO sample.

Annular furnace is widely used for high temperature annealing of oriented silicon steel coils. The coils are placed under a cover in a protective atmosphere. The heating rate of the process must be strictly controlled to prevent magnetic property variations of the products. In this work, temperature distribution in the coil at the heating stage is simulated using finite method. Effects of fuel flux at burners on temperature distribution in the furnace are also analysed. Experiments are carried out to measure the parameters needed in simulations and to verify the simulation results. For a coil of 510 mm inside and 1710 mm outside diameters, the largest temperature difference in the coil is found to be as high as 438 °C, which occurs at about 8 h of heating. A total of 72 h is needed for the temperatures across the coil to reach a target level of 1170 °C. The temperature difference in the coil can be greatly reduced if N2 is replaced by H2 as protective atmosphere and the gap between sheet layers in the coil is reduced. Temperature distribution on the cover during heating is found to be rather uniform with the largest difference being within 30 °C.

In this paper, an iterative multiwavelength method is proposed for the reconstruction of soot temperature and volume fraction fields in an axisymmetric flame with absorbing, emitting participating ...

Ultrathin flexible Janus membranes with asymmetric structure and anisotropic conductive characteristics have attracted considerable attention due to their promising applications in soft electronics, microsensors, and energy management technologies. Conventional fabrication methods for Janus films usually require the assistance of interfacial or auxiliary equipment, which are usually complex and time-consuming. Herein, flexible and ultrathin liquid metal (LM) Janus films with integrated electrically, optically, and thermally anisotropic properties are presented for the first time. They were fabricated by the simple mixing of liquid metal nanoparticles with cellulose nanocrystal cotton and polyvinyl alcohol suspension, followed by self-assembly density deposition without the necessity of any interface or equipment, thereby making it easier and time-saving when compared with traditional interfacial or noninterfacial fabrication methods for Janus films. This unique substrate-ink-integrated nature of the liquid metal Janus film and shear-friction-enabled direct-writing technology provide a novel approach for the field manufacturing of customized electronics and one-step fabrication of multilayer circuits. It is particularly important to note that a microscale depth sensor can also be achieved in a simple manner; further, a smart acupuncture depth training model was developed by using liquid metal Janus films. In addition, the as-prepared Janus film could be used as a light conversion switch and temperature regulator. This study suggests a versatile strategy for creating Janus films with multifunctional (such as electrical, thermal, and optical) anisotropies.

The porous p-type Bi0.4Sb1.6Te3 bulks containing irregularly and randomly oriented pores were obtained by artificially controlling the relative density of sintered samples during resistance pressing sintering process. It is demonstrated that the thermoelectric performances are significantly affected by the porous structure, especially for the electrical and thermal conductivity due to the enhanced carrier scattering and phonon scattering. The increasing porosity resulted in the obvious decrease in electrical and thermal conductivity, and little change in Seebeck coefficients. It is encouraging that the reduction of thermal conductivity can compensate for the deterioration of electrical performance, leading to the enhancement in thermoelectric figure of merit (ZT). The maximum ZT value of 1.0 was obtained for the sample with a relative density of 90% at 333 K. Unfortunately, the increase in porosity also brought in obvious degradations in Vickers hardness from 51.71 to 27.74 HV. It is worth mentioning that although the Vickers hardness of the sample with a relative density of 90% decreased to 40.12 HV, it was still about twice as high as that of the zone melting sample (21.25 HV). To summarize, introducing pores structure into bulks properly not only enhances the ZT value of Bi2Te3 based alloys, but also reduces the use of raw materials and saves production cost.

It is remarkably desirable and challenging to design a stretchable conductive material with tunable electromagnetic‐interference (EMI) shielding and heat transfer for applications in flexible electronics. However, the existing materials sustained a severe attenuation of performances when largely stretched. Here, a super‐stretchable (800% strain) liquid metal foamed elastomer composite (LMF‐EC) is reported, achieving super‐high electrical (≈104 S cm−1) and thermal (17.6 W mK−1) conductivities under a large strain of 400%, which also exhibits unexpected stretching‐enhanced EMI shielding effectiveness of 85 dB due to the conductive network elongation and reorientation. By varying the liquid and solid states of LMF, the stretching can enable a multifunctional reversible switch that simultaneously regulates the thermal, electrical, and electromagnetic wave transport. Novel flexible temperature control and a thermoelectric system based on LMF‐EC is furthermore developed. This work is a significant step toward the development of smart electromagnetic and thermal regulator for stretchable electronics., This work reports a super‐stretchable liquid metal foamed elastomer composite with both high electrical and thermal conductivities, and electromagnetic interference shielding effectiveness of 85 dB even when strained at 400% due to the stretching enabled conductive network elongation and reorientation, which also exhibits unique multifunctional reversible switch responses for application to tunable control of electromagnetic waves and thermal transport.

This paper presents an effective memetic algorithm for the large-scale vehicle routing problem with time windows (VRPTW). Memetic algorithms consist of an evolutionary algorithm for the global exploration and a local search algorithm for the exploitation. In this paper, a switching mechanism is introduced to balance quantitatively between exploration and exploitation, to improve the convergent performance. Specifically, a similarity measure and a sigmoid function is defined to guide the crossover. Experimental results on Gehring and Homberger’s benchmark show that this algorithm outperforms previous approaches and improves 34 best-known solutions out of 180 large-scale instances. Although this paper focuses on the VRPTW, the proposed switching mechanism can be applied to accelerate more general genetic algorithms.

With the rapid rise of artificial intelligence, knowledge graph has also been widely concerned, and the security of knowledge graph has also followed. In the process of knowledge graph construction, process files are easy to be tampered and forged by malicious, so that the reasoning results are biased. The purpose of this experiment is to explore the availability and effectiveness of knowledge graph based on blockchain and distributed system storage and traceability. This paper proposes a scheme of process file storage and traceability of knowledge graph based on blockchain and distributed file storage system. Firstly, the process files of building knowledge graph are preprocessed by distributed file system to improve the storage efficiency and save resources; then the processed files are stored in the blockchain network to ensure the security and integrity of the files.

Here, Bi1-xBaxCuSe1-xTexO (x = 0, 0.02, 0.04, 0.06, 0.08, 0.10) ceramics have been prepared by mechanical alloying (MA) and resistance pressing sintering (RPS) process. The effects of Ba/Te doping on the thermoelectric properties have been investigated systematically. For Ba doping, it can tune the Fermi level and promote the band convergence, decreasing the band gap and significantly enhancing the carrier concentration; for the Te doping based on Ba doping, it can profoundly reduce the difference of electronegativity in (Cu2Se2)2- layer, increase bond covalency, and then increase the electrical conductivity. The results indicate that the substitution of Ba/Te resulted in significant increases of electrical conductivity and power factor. Based on this, modulation doping leads to the simultaneous increase of the electrical conductivity and Seebeck coefficient. Finally, the maximum power factor of 0.98 mW m−1 K−2 and ZT value of 1.17 were obtained for the modulation doped Bi0.90Ba0.10CuSe0.90Te0.10O bulk, which were ~ 3.5 and ~ 2.2 times respectively as those of the pristine BiCuSeO ceramic.

In order to understand the movement of the inclusion in electroslag remelting (ESR) process, a transient three-dimensional (3D) comprehensive mathematical model has been established. The finite volume method was employed to solve the mass, momentum and energy conservation equations as well as the Maxwell’s equations. The volume of fluid (VOF) approach was used to define the redistribution of the metal and the slag. The inclusion trajectory was described by using the two-way coupled Euler-Lagrange method. Experiments were conducted to verify the proposed model. The removal ratios of the inclusions with 1 µm and 10 µm diameters constantly increase with a larger current. The removal ratios of the inclusions with 3 µm and 5 µm diameters first increase with the current ranging from 1000 A to 1600 A, but then decrease if the current continuously increases to 1800 A. The inclusions with 15 µm and 20 µm diameters are almost completely eliminated in the five currents. The increase of the inclusion density would reduce the removal ratio of the inclusion with a larger diameter in different degrees.

The layered oxyselenide BiCuSeO thermoelectric ceramics are attracting much scientific attention for its excellent thermoelectric properties. Herein, Bi1-xSbxCuSe1-xTexO (x = 0, 0.01, 0.02, 0.04, 0.06, 0.08) ceramics have been prepared by ball milling (BM) and resistance pressing sintering (RPS) process. The effects of Sb/Te doping and grain size on the thermoelectric/mechanical properties are investigated systematically. For the former, it can tune the Fermi level and promote the band convergence, decreasing the band gap and concurrently enhancing the carrier concentration; for the latter, it can profoundly modify microstructure into an all-scale hierarchical architecture to scatter phonons with broad range of mean free paths, effectively reducing the lattice thermal conductivity. The results indicates that the substitution of Sb/Te resulted in the significantly increase of electrical conductivity and power factor, and BM effectively reduces the grain size to ~ 387 nm in the sample after sintering, which leads to a decrease in the thermal conductivity and an increase in the electrical conductivity. The maximum power factor of 0.72 m Wm−1 K−2 and ZT value of 1.19 were obtained for Bi0.92Sb0.08CuSe0.92Te0.08O with BM time = 16 h at 873 K, which was ~ 2.7 and ~ 2.2 times as that of the pristine BiCuSeO ceramic.

Here we report an active method to enhance the thermal performance of phase change material (PCM) based on magnetically-stirring method. The magnetic bead with small size embedded in the container filled with octadecanol, is driven to rotate by rotating magnetic field, and induce the forced convective heat transfer of the liquid octadecanol. We investigate the impact of rotating magnetic velocity, magnetic bead size, the distance between magnetic bead and rotating permanent magnet on the surface temperature of the simulated heating plate. The experimental results indicated that magnetically stirring obviously improve the heat transfer from liquid phase to solid phase of octadecanol and make simulated heat source keep a lower and smoother temperature platform. We also find that the best condition point could be determined by matching the rotation velocity for the given size of magnetic bead. These results are expected to provide insights into the design and optimization of latent heat thermal energy storage systems. Keywords: Phase change material, Magnetically stirring, Heat transfer, Energy storage technology

The effect of elevated curing temperature on the fracture properties of concrete was investigated. Fracture experiments were carried out on wedge splitting specimens exposed to temperatures ranging from 5 to 60 °C. A new maturity model was then proposed for describing the combined influence of the temperature and aging on the fracture properties of concrete. The results show that the fracture energy of concrete subjected to high temperature is high at early ages; however, the effect of curing temperature on the fracture energy was reversed after 14 days, with greater later-age fracture energy corresponding to lower temperature and vice-versa. The effective fracture toughness of concrete also exhibited the same temperature inversion phenomenon. The optimum curing temperature was found to be approximately 40 °C for development of concrete fracture properties. The value of activation energy changed with fracture properties, temperature ranges and the development stage of a given fracture property. The proposed model accurately predicts the fracture properties of concrete and significantly simplifies the calculation process of the maturity index relative to the existing maturity method.

In order to study the effect of refractory graphite content and heating temperature on carbon pick-up of ultra-low-carbon steel from magnesia-carbon refractory, a transient axisymmetric mathematical model has been established. The momentum, heat and mass transfer between the refractory and the molten steel was modeled by using porous medium. Arrhenius law was employed to define the rate of the carbothermic reduction reaction of the magnesia. Besides, a series of experiments were carried out to verify the model. The results indicate that the carbon content of the molten steel rapidly rises when the refractory graphite content ranges from 3 mass% to 10 mass%, and the carbon pick-up induced by direct dissolution is significantly promoted. The influence of the heating temperature on the carbon content in the molten steel however is negligibly small, and the proportions of the carbon pick-up caused by the direct dissolution and the chemical reaction basically remain the same although the heating temperature increases by 100 K. The effect of the refractory graphite content on the carbon pick-up of the molten steel far outweighs that of the heating temperature.

During the past few decades, Bi2Te3-based alloys have been investigated extensively because of their promising application in the area of low temperature waste heat thermoelectric power generation. However, their thermal stability must be evaluated to explore the appropriate service temperature. In this work, the thermal stability of zone melting p-type (Bi, Sb)2Te3-based ingots was investigated under different annealing treatment conditions. The effect of service temperature on the thermoelectric properties and hardness of the samples was also discussed in detail. The results showed that the grain size, density, dimension size and mass remained nearly unchanged when the service temperature was below 523 K, which suggested that the geometry size of zone melting p-type (Bi, Sb)2Te3-based materials was stable below 523 K. The power factor and Vickers hardness of the ingots also changed little and maintained good thermal stability. Unfortunately, the thermal conductivity increased with increasing annealing temperature, which resulted in an obvious decrease of the zT value. In addition, the thermal stabilities of the zone melting p-type (Bi, Sb)2Te3-based materials and the corresponding powder metallurgy samples were also compared. All evidence implied that the thermal stabilities of the zone-melted (ZMed) p-type (Bi, Sb)2Te3 ingots in terms of crystal structure, geometry size, power factor (PF) and hardness were better than those of the corresponding powder metallurgy samples. However, their thermal stabilities in terms of zT values were similar under different annealing temperatures.

In this paper, a finned heat pipe assisted passive heat sink based on a newly emerging high performance phase change material (PCM), the low melting point metal (LMPM), was developed for thermal buffering of high power electronics which works intermittently with heat generation rate up to 1000 W (10 W/cm2). Firstly, thermal performances of the PCM heat sink under different thermal shocks (from 200 W to 1000 W) were experimentally evaluated, in comparison with that of an organic PCM which has similar melting point. It was found that, the former one can prolong the working duration 1.4–2.4 times that of the latter one. Then, the performance of the heat sink was improved through reducing the contact thermal resistance and by increasing the fin number. Furtherly, an air cooling radiator was configured to accelerate the solidification process of the PCM module, which makes it capable of maintaining its highest temperature below 85 °C under 1000 W periodic thermal shock (10 min on and 15 min off). Moreover, energy dispersive spectrometer (EDS) analysis was conducted to verify the compatibility of the LMPM PCM and the structural materials. Finally, a simplified numerical model was developed and validated for the currently constructed finned heat pipe assisted LMPM PCM heat sink, which can be much helpful for future practical thermal design and optimization of this kind of thermal buffering module.

Thermoelectric generator has been considered as a promising device to recover industrial waste heat for electricity generating. To figure out the heat transfer and electric conduction processes in thermoelectric generator, a three-dimensional numerical model has been built up which consists of 127 thermocouples. The open-circuit voltage, internal resistance, and output power have been studied by numerical simulation. All calculation results are in good agreement with the experimental results, and the maximum deviation is less than 6%. Due to the influence of Peltier effect, both heat flow and equivalent thermal conductivity increases by 30.2% when temperature difference between the hot and cold side is 170 °C and the thermoelectric generator reaches its maximum power output. In addition, the Peltier effect has been investigated when the convective heat transfer boundary conditions are applied. The results showed that the effective temperature difference was raised to 13.6 °C (a 10.2% increase) and maximum output power was raised to 0.59 W (a 14.8% increase) for the thermoelectric generator model with a fin height of 100 mm when compared with that without fins. Besides that, the radio of load resistance to internal resistance decreased from 1.31 to 1.14.

Room-temperature liquid metals have many intriguing properties that have not previously been fully understood. Among them, surface tension behaviors of such metals are especially critical in a group of newly emerging areas such as printed electronics, functional materials and soft machines, etc. This study is dedicated to clarifying the wettability of liquid metals on various substrate surfaces with varied roughness immersed in solutions when subject to an electric field. The contact angles of Ga75.5In24.5 in several typical liquids were comprehensively measured and interpreted, and were revealed to be affected by the components and concentration of the environmental solution. Meanwhile, the roughness of the substrates is also revealed to be an important parameter dominating the process. The dynamic wetting behaviors of liquid metal in aqueous environment under an electric field were quantified. The contact angle values of eutectic gallium–indium alloys (eGaIn) on titanium substrates with different roughness would lead to better electrowetting performances on rougher surfaces. In particular, using an electrical field to control the wetting status of liquid metal with the matching substrate have been illustrated, which would offer a practical way to flexibly control liquid metal-based functional devices working in an aqueous environment. Furthermore, Lippmann–Young’s equation reveals the relationship between contact angle and applied voltage, explaining the excellent electrowetting property of eGaIn. The power law, R = αt β , was adopted to characterize the two-stage wetting process of eGaIn under different voltages. In the initial process, β ≈ 1/2 represents the complete wetting law, while the later one, β ≈ 1/10, meets with Tanner’s law of a drop spontaneously spreading on a smooth surface.

Aerosol deposition is highly concerned recently due to its significant impact on surface glass cleaning, glass transmittance and energy conversion of building-integrated photovoltaics (BIPV). Thus, this paper reviewed direct transmittance degradation works of PV module surface glasses, and employed several integrated and improved experiment and model methods to investigate the correlation effects of PM2.5 deposition dynamics, tilt angles, surface conditions and self-cleaning TiO2 nanocoating on glasses. Series of physical models from ambient aerosol concentration to deposition density and transmittance reduction were extended or newly developed. Measured and modeled data could inter-validate with each other and literature results. The usage condition of Al-Hasan model was discovered as 0 a p 0.10 for particle projected-area fraction under clustering particle projected-area fraction a p c p ≤ 5 % . Ranging from 0 to 18.7 μg/cm2, deposition densities with the most reductions (50–91%) were found under the combination of wet and nanocoating conditions due to effects of water film and low adhesive force. Generally, the average deposition densities decreased 19–47% with the increase of each 30° tilt angle for different surface properties. Finally, six linear empirical models were obtained with decreasing slopes of 0.001544–0.001841 between fine aerosol deposition density and transmittance ratio. These observed phenomena and derived models would be useful for solar energy, building illumination or heat-transfer, and BIPV industries.

Background Thermally significant blood flows into locally cooled diseased tissues and warm them during cryosurgery so that the iceball is often hard to cover the whole diseased volume. This paper is aimed at investigating the effects of large arterial bifurcation on the temperature distribution during cryosurgery through simulation method. Methods A parametric geometry model is introduced to construct a close-to-real arterial bifurcation. The three-dimensional transient conjugate heat transfer between bifurcated artery and solid tissues with phase change during cryosurgery is performed by finite volume method. Results The discussion was then made on the effects of the relative position between cryoprobe and artery bifurcation, the inlet velocity of root artery and the layout of multiple cryoprobes on the temperature distribution and iceball evolution. The results show that the thermal interaction between blood flow and iceball growth near bifurcation is considerable complex. The thermal effects of bifurcation could modulate the iceball morphology, severely weaken its freezing volume and prevent the blood vessel from being frozen. Conclusion The present work is expected to be valuable in optimizing cryosurgery scheme of the situation that the bifurcated artery is embedded into the disease tissue.

Energy consumption of fuel-fired industrial furnace accounts for about 23% of the national total energy consumption every year in China. Meanwhile, the reduction of combustion-generated pollutants in furnace has become very important due to the stringent environment laws and policy introduced in the recent years. It is therefore a great challenge for the researchers to simultaneously enhance the fuel efficiency of the furnace while controlling the pollution emission. In this study, a transient 3-D mathematical combustion model coupled with heat transfer and pollution formation model of a walking-beam-type reheating furnace has been developed to simulate the essential combustion, and pollution distribution in the furnace. Based on this model, considering nitrogen oxides formation mechanism, sensitivity study has been carried out to investigate the influence of fuel flow rate, air-fuel ratio on the resultant concentration of nitrogen oxides in the flue gas. The results of present study provide valuable information for improving the thermal efficiency and pollutant control of reheating furnace.

A novel phenomenon of electrochemically enabled reactive wetting, coating and spreading of gallium-based liquid metals within porous copper (Cu) was observed, and its mechanism was demonstrated. Its extensive applications including in the fabrication of large-area conductive film patterns, transfer-printing technology and the preparation of thermal interface materials with superhigh heat conductivity are presented.

A transient three-dimensional (3D) comprehensive mathematical model has been developed to understand oxygen and sulfur transfers in electroslag remelting process. The solutions of the mass, momentum, energy and species conservation equations were simultaneously carried out by finite volume method. The Joule heating and Lorentz force were taken into account. The thermochemical and electrochemical transfers of oxygen and sulfur were represented through the application of a metallurgical thermodynamic and kinetic module. In order to obtain the evolution of oxygen activity, the chemical reaction between dissolved aluminum and dissolved oxygen in the metal was included. The comparison between the measured and simulated data indicates that the model can predicate the transfer behavior with an acceptable accuracy. The thermochemical reaction always removes oxygen and sulfur from the metal, while the electrochemical reaction brings oxygen and sulfur back to the metal through the metal droplet-slag interface, and takes them away from the metal through the metal pool-slag interface. The oxygen removal ratio is about 60%, and the contribution of the electrochemical reaction is around 82%. The sulfur removal ratio is approximately 76%, and the contribution of the electrochemical reaction is around 39%.

The p-type Bi 2 Te 3 alloys were prepared using the waste particles from the cutting process of the zone melting crystal rods as the main raw materials by impurity removal process including washing, carbon monoxide reduction and vacuum metallurgical process. The thermoelectric properties of the Bi 2 Te 3 based bulk materials were optimized by component adjustment, second smelting and resistance pressing sintering (RPS) process. All evidences confirmed that most of impurities from the line cutting process and the oxidation such as Sb 2 O 3 , Bi 2 O 3 and Bi 2 Te 4 O 11 could be removed by carbon monoxide reduction and vacuum metallurgical process adopted in this work, and the recycling yield was higher than 97%. Appropriate component adjustment treatment was used to optimize the carrier content and corresponding thermoelectric properties. Lastly, a Bi 0.36 Sb 1.64 Te 3 bulk was obtained and its power factor ( PF ) could reach 4.24 mW m −1 K −2 at 300 K and the average PF value was over 3.2 mW m −1 K −2 from 300 K to 470 K, which was equivalent with the thermoelectric performance of the zone melting products from high purity elements Bi, Te and Sb. It was worth mentioning that the recovery process introduced here was a simple, low-cost, high recovery rate and green recycling technology.

In order to enhance the performance of the automobile waste heat recovery system, a novel two-stage automobile thermoelectric generator with a cascade configuration along the temperature gradient of exhaust gas was designed. The corresponding integrated one-dimensional numerical model considering temperature-dependent thermoelectric materials was developed to predict the performance accurately. The impedance matching condition for the maximum output power was derived for the novel two-stage automobile thermoelectric generator. The developed model was demonstrated through comparisons with the reported experimental data and simulation results. The results indicated significant discrepancies in output power, conversion efficiency, and the temperature difference between the cold/hot sides of thermocouples for single-stage and two-stage configurations. The designed thermoelectric generator with the two-stage configuration could capture the temperature change along the flow direction of exhaust gas and obtain better performance by adjusting the length of the two-stage module. Compared to the traditional single-stage thermoelectric generator, the designed two-stage configuration could achieve the output power increments by 13.5% under the same working conditions. The effects of working conditions (exhaust gas temperature and mass flow rate) and TEG geometry size on the output power are studied. This work could provide some guidance on the design and performance enhancement of automobile thermoelectric generators.