Acoustic black holes (ABHs) achieved by thinning structural thickness following a power-law profile have shown fantastic applications in vibration and noise suppression, energy harvesting, and wave ...manipulation. For the latter, many passband properties exemplified by self-collimation, focusing, and bi-refraction, have been reported on metamaterial plates with embedded circular ABHs in periodic arrangement. To date, however, band gaps (BGs), being the main feature for metamaterials, have not yet been observed in ABH plates. In this paper, we propose a new class of phononic crystal consisting in two crossed strip ABHs to open broad and complete BGs in plates, based on the dual benefit of local resonance and Bragg scattering effect. The dispersion curves of infinite strip ABHs are recovered by means of the Gaussian expansion method, then validated by a finite element model. The influences of ABH radius, ABH order and residual thickness, on the GBs have been carried out by parametric studies. The results show that the BGs can be modulated to very low frequencies via adjusting the ABH parameters, while maintaining the broadband characteristics. Finally, the wave propagation properties including isolation, guiding, and shielding, in plates with finite periodic arrays have been characterized, indicating that a small number of ABHs are very efficient to quarantine flexural waves. Experimental samples have been fabricated and tested, showing very close results compared to the BGs predicted by the GEM. Even though the proposed strip ABHs seems fragile in strength, peripheral frame can be adopted to partially alleviate this problem. The proposed PCs possess a great potential to broaden ABH applications in vibration control and wave manipulation in plates based on the highlighted BG feature.
In this paper, a prediction model for hot-rolled strip crown based on an artificial neural network (ANN) is presented. Considering the mean squared error (MSE) and correlation coefficient (R), ...production data of 10,133 coils collected from a hot rolling plant are used to establish models. A feed-forward neural network with one hidden layer, a non-dominated sorting genetic algorithm II (NSGA II) optimized ANN, and a deep neural network (DNN) are applied to evaluate the prediction performance. Parameter settings of the ANN and NSGA II including learning rate, hidden neurons, activation function and population size, and crossover probability, are investigated to acquire the optimal model. The structure of the DNN, including how many layers and units the network should contain, is also studied. Prediction performance comparisons of the ANN, NSGA II-ANN, and DNN are presented. Among the ANN, NSGA II-ANN and DNN, the results show that the DNN has the highest prediction accuracy. Root mean squared error (RMSE) of the proposed DNN is 2. 06μm, and 97.04% of the prediction data have an absolute error of less than 5μm. Through model response surfaces, effects of four key operating parameters are investigated. The results indicate that the proposed DNN with strong learning ability and generalization performance can be well applied to hot rolling production.
•Three neural network based models are established based on a dataset from a hot-rolling line.•The proposed models used to predict strip crown can acquire high prediction precisions.•The best performed model precisely corresponds with the existing physical understandings.•Using the parameters obtained by the best performed model, strip crown is close to target values.
Medium carbon steels have been widely used in the fields of tool and die manufacturing due to their outstanding hardness and wear resistance. In this study, microstructures of 50# steel strips ...fabricated by twin roll casting (TRC) and compact strip production (CSP) processes were analyzed to investigate the influences of solidification cooling rate, rolling reduction, and coiling temperature on composition segregation, decarburization, and pearlitic phase transformation. The results show that a partial decarburization layer with a thickness of 13.3 μm and banded C-Mn segregation were observed in the 50# steel produced by CSP, leading to the banded distributions of ferrite and pearlite in the C-Mn poor regions and C-Mn rich regions, respectively. For the steel fabricated by TRC, owing to the sub-rapid solidification cooling rate and short processing time at high temperatures, neither apparent C-Mn segregation nor decarburization was observed. In addition, the steel strip fabricated by TRC has higher pearlite volume fractions, larger pearlite nodule sizes, smaller pearlite colony sizes and interlamellar spacings due to the co-influence of larger prior austenite grain size and lower coiling temperatures. The alleviated segregation, eliminated decarburization and large volume fraction of pearlite render TRC a promising process for medium carbon steel production.
•Transforming continuous fin into discontinuous fins enhances heat transfer in PCM.•The use of discontinuous strip fins can improve the energy release time by up to 89%.•89% time improvement was ...achieved by an optimum distribution of the strips fins.•89% time improvement was achieved when only 2% strip fins were employed.•Fin material is one of the effective parameters in discontinuous fins.•Using nanoparticles alone cannot lead to a significant improvement in phase change time.
Energy storing is one of the most vital needs in the energy industry. This paper aims to solve the problem of long energy release time in phase change material (PCM) energy storage system. In the present study, continuous longitudinal fin that had been traditionally used in literature is transformed into a new three-dimensional distribution of discontinuous strip fins. Effects of the geometric distribution of the strip fins, fins material and adding nanoparticles (NPs) to the PCM on heat transfer enhancement and energy discharge time are investigated by testing 17 different cases. According to the results, the use of discontinuous fins can improve the energy release time up to 89% and 84% comparing to continuous copper and aluminum fins, respectively. Moreover, the results indicate that effect of fin material on the thermal performance is insignificant in cases of continuous fins. The results confirmed that the optimal distribution for cases of discontinuous aluminum fins with and without NPs is different. Besides, the maximum of saving discharge time is 77.8% and 59.5% for combination of NPs with copper and aluminum discontinuous fins, respectively. Besides, the results show that the application of nanoparticles alone cannot lead to a significant discharge time improvement.
The photocatalytic efficiency of polymeric carbon nitride is hampered by high carrier recombination rate and low charge transfer. Herein, these issues are addressed by constructing 1D strip‐like ...carbon nitride with a large π‐electron conjugated system from carbon‐doping, realizing the synchronization control of its electronic structure and morphology. Nicotinic acid, a monomer with the carboxyl group and pyridine ring, and melamine are selected for assembling the strip‐like supramolecular via hydrogen bond under hydrothermal process. Both peripheral pyridine unit and hydrogen bond have significant effect on self‐assembly process of nicotinic acid and melamine along one dimension to form a strip‐like precursor. Subsequently, 1D thin porous strip‐like carbon nitride is obtained by calcination treatment of precursor. The as‐prepared 1D strip‐like carbon nitride with effective π delocalization from carbon‐doping and porous structure can accelerate charges and mass transfer and provide extra active sites. Both theoretical and experimental results demonstrate that carbon doping (pyridine heterocycle) narrows the bandgap via manipulating the band position and increases the π electron density. Thus, the 1D porous thin strip‐like carbon nitride realizes compelling hydrogen evolution rate (126.2 µmol h−1), far beyond (≈18 fold) the value of polymeric carbon nitride (PCN) (7.2 µmol h−1) under visible light irradiation.
1D strip‐like carbon nitride (CN) with a large π‐electron conjugated system realizes the synchronization control of its electronic structure and morphology, which improves the separation efficiency of photogenerated charge carriers. Thus, such strip‐like carbon nitride exhibits a significant enhancement in photocatalytic activity with the hydrogen evolution rate of 126.2 µmol h−1, about 18 times higher than that of bulk CN.
•Novel perforated louvered strips significantly improve the thermal performance.•Heat transfer enhances up to 45.8% by using DPLS instead of typical louvered strip.•Thermal performance of 1.84 is ...achieved by using DPLS insert with θ=25°oat Re=14,000.•Additional vortex flow near the holes in the main reason for Nu number enhancement.•Friction factor increases up to 81% for DLPS insert with θ=15°o compared to plain tube.
Numerical simulations have been performed to analyze the turbulent flow characteristics and thermal performance of fluid flows inside heat exchangers fitted with novel perforated louvered strip inserts with different slant angles. The (RNG) k-ε is employed for the numerical simulations with the Reynolds number in the range of 5000–14,000. The results demonstrate that the recirculation flow through the holes of perforated louvered strips significantly improves the Nusselt number and thermal enhancement factor compared to the louvered strips without holes. Better fluid mixing between the tube walls and core region is the main physical reason for heat transfer augmentation. The recirculation flow through the holes of the perforated louvered strips significantly intensifies the flow disturbance and thus, the turbulent kinetic energy values near the holes increases. The effects of double mounted louvered strips on the axial velocity and turbulent kinetic energy are also investigated. The results show that the average Nusselt numbers for the cases of double perforated louvered strip with θ=15∘ and 25∘ are 30.1% and 45.84%, respectively, higher than single perforated louvered strip with the same slant angles. The maximum thermal enhancement factor of 1.84 can be obtained by employing double perforated louvered strip with θ=25∘ at Re=14,000.
In most research on the hot strip mill production scheduling problem (HSMPSP) arising in the steel industry, it is accepted that a schedule with lower penalty caused by jumps of width, hardness, and ...gauge will result in lower roller wear, so it is regarded as a better schedule. However, based on the analysis of production processes, it is realised that rolling each coil also cause roller wear. In order to assessing the roller wear associated with production scheduling more precisely, it is necessary to consider it as another factor besides those jumps, especially when complicated constraints are involved. In this paper, an improved method is proposed to quantify the expected wear of the rollers done by those jumps and rolling processes. Then the HSMPSP whose objective is to maximise the total length of all scheduled coils is formulated as a team orienteering problem with time windows and additional production constraints. A heuristic method combining an improved Ant Colony Extended algorithm with local search procedures dedicated to HSMPSP is developed. Finally, computational results on instances generated based on production data from an integrated steel mill in China indicate that the proposed algorithm is a promising solution specific to HSMPSP.
Based on the finite volume method, a continuum model that coupled enthalpy‐porosity approach is developed herein to investigate the fluid flow, phase transition, and macrosegregation in the ...solidification process for bloom continuous casting. The optimal parameters of the process of feeding strip technology (FST) are obtained, and the effects of different processes of regular continuous casting, mold electromagnetic stirring (M‐EMS), and FST on the superheat degree and macrosegregation are compared. The results show that the process of FST can not only greatly reduce the superheat degree of liquid steel and improve the macrosegregation in the bloom center, but also effectively avoid the deterioration of negative segregation defects at the edge of bloom, compared with the processes of regular continuous casting and M‐EMS. The best process parameters for the process of FST are as follows: the strip feeding position is 0.12 m far away from the bloom centerline, and the steel strip feeding velocity is 0.20 m s−1.
The results of the article show that the feeding strip technology can not only greatly reduce the superheat degree of liquid steel and improve the macrosegregation in the bloom center, but also effectively avoid the deterioration of negative segregation defects at the edge of the bloom, compared with the processes of regular continuous casting and mold electromagnetic stirring.
Display omitted
•Crop yields were simulated with a relay strip intercrop model.•Simulated optimum strip widths are less than 1 meter wide.•Benefits of intercropping drop as strip widths become ...wider.•Results are sensitive to border row effects on RUE.
Intercropping is the cultivation of multiple crop species on the same land. Relay strip intercropping is an intercropping system in which the component species are grown in strips, while the growing periods of the crop species overlap only partially. The effects of strip width on yields in relay-strip intercropping are still poorly understood. Here in a case study on wheat-maize relay intercropping a simple strip intercropping model was applied to quantify intercropping performance as a function of a wide range of strip widths. Simulations showed that (1) the optimum strip width is less than 1 meter and (2) benefits of intercropping rapidly drop as strips become wider. Most previous experimental work was also done at narrow configurations, with strips less than 3 meters wide. Benefits of intercropping may therefore be less than what would be expected from experiments if narrow configurations are not attainable because of lack of mechanisation. All optimised strip configurations showed a Land Equivalent Ratio (LER) larger than 1 indicating benefits of intercropping, irrespective of assumptions that were made on radiation use efficiency in intercropped species as compared to sole crops. At current prices of wheat and maize, however, intercropping gross margin exceeded sole cropping gross margin only if the intercrop RUE was larger than sole crop RUE for both species. This study shows that strip crop growth models can be used to specify needs for future machinery, that will enable farmers to attain benefits from intercropping.
In this study, turbulent flow characteristics of CuO-water nanofluid through heat exchanger pipe enhanced with louvered strips are numerically investigated. Nanoparticles volume fraction (ϕ) varied ...from 0 to 2%. The louvered strips are mounted in single and double geometries. The slant angle (θ) and the Reynolds number (Re) are within 15° − 25° and between 5000 and 14,000, respectively. (RNG) k − ϵ model is employed based on the finite volume technique. The results illustrated that strong flow disturbance between the wall and the louvered strip is the main reason for turbulent kinetic energy increment. Besides, the nanoparticles improve the thermophysical properties of the working fluid, which results in better heat transfer. The Nu number increases 15.6% by using nanofluid instead of water at Re = 14000. The highest thermal enhancement parameter of 1.99 is obtained at Re = 14000 by using double perforated louvered strip with θ = 25°. The recirculating flow inside the holes can significantly improve the thermal performance.
Display omitted
•CuO-water nanofluid flow through heat exchangers fitted by DPLS is investigated.•Heat transfer enhances up to 15.6% by using Cu nanoparticles in water with ϕ = 2% .•Highest friction factor (f = 0.171) is reached by using DPLS turbulators at Re = 5000.•Thermal performance of 1.99 is achieved by using DPLS insert with θ = 25° at Re = 14,000.•Additional recirculation flow near the holes of LS inserts improves heat transfer.
PDF
