Theoretical Calculation Value Research Articles

Determination of Fe3O4 Content and Total Nonhydraulic Minerals in Steel Slag

The nonhydraulic minerals (Fe3O4, RO phase, Fe) in slag are important indicators for evaluating the pozzolanic activity and detecting the quality of the slag activation processing technology. Fe3O4 is an important characteristic mineral among the nonhydraulic minerals. In order to accurately assess the pozzolanic activity of steel slag powder and to monitor the quality of the activation process of steel slag powder for separate nonhydraulic minerals, it is imperative to precisely determine the nonhydraulic mineral content within the steel slag. Further refinement and enhancement are required for both the HNO3 dissolution method used in determining Fe3O4 content in steel slag, as well as for the EDTA-DEA-TEA (ethylenediamine tetraacetate sodium-diethylamine-triethanolamine) dissolution method employed in determining total nonhydraulic minerals, due to potential deviations caused by challenging impurity separations. The results show that the content of Fe3O4 is determined by 10%HNO3-20%NaOH-chemical analysis method, which solves the problem that the impurities of refractory materials (quartz, corundum, mullite) and amorphous phase affects the content determination in HNO3 dissolution method. The total amount of nonhydraulic minerals (Fe3O4, RO phase, Fe) was determined by the EDTA-NaOH-TEA dissolution method, which solved the problem that the incomplete dissolution of C2F in the EDTA-DEA-TEA dissolution method affected the content determination. The maximum error between the content determination value and the theoretical calculation value of the two methods is less than 0.50%. The improved Fe3O4 and total nonhydraulic mineral quantification methods are feasible and reliable.

Fixed‐time sliding mode trajectory tracking control for marine surface vessels under mismatched conditions and input saturation

SummaryThis paper addresses a trajectory tracking control problem for marine surface vessels (MSVs) in the presence of mismatched conditions and input saturation. Firstly, an MSV model under mismatched conditions is established to solve the problem of unreasonable modeling methods in the existing literature. Secondly, fixed‐time disturbance observers (FXDOs) are designed, where the designed FXDOs not only avoid selecting complicated parameters but also has simple structures, and the disturbance estimation errors can converge to the origin within a setting time. Thirdly, based on the FXDOs and an anti–saturation auxiliary dynamic system, a trajectory tracking control scheme in the presence of mismatched conditions and input saturation is constructed by virtue of fixed‐time integral sliding mode control (SMC), and the actual tracking error signals are uniformly fixed‐time bounded rather than finite‐time one. Fourthly, in order to decrease theoretical calculation values of the original setting time in fixed‐time control, the new setting time under three different parameter conditions is derived, and thus reducing the conservatism. Finally, the simulation results are provided to show the effectiveness and superiority of the designed tracking control scheme.

Research and application on intelligent monitoring and early warning system for Inner-Suspended gin poles

The pressure of the inner suspension pole body is one of the key control indicators that need to be focused on in the design and use of the pole. A real-time intelligent monitoring and early warning system for the working status of the internal suspension pole tower is developed to address safety issues such as excessive inclination, excessive force on the stay wire or support rope during the construction process, including pole body pressure monitoring. The system monitors the axial pressure and inclination angle of the pole body using an integrated sensor for the axial pressure and inclination angle of the pole body. The tension sensor monitors the tension of the lifting, pulling, and supporting ropes, and the anemometer monitors the environmental wind speed. The monitoring data is fed back to the monitoring system through a wireless transmission module, and the safety of the pole state is determined in real-time through an embedded algorithm. When the preset threshold is exceeded, an audible and visual warning is issued. A comparison was made between the actual lifting test and theoretical calculation values, and engineering applications were completed.

Theoretical and experimental study on the secondary heat recovery cycle of the mixed working fluid in ocean thermal energy conversion

The small ocean temperature difference causes the power generation efficiency to not be high while the power generation cost is high; this method has not been commercially applied. Therefore, it is particularly important to find a new thermal cycle to improve the cycle efficiency. In this paper, a new cycle of the ocean temperature difference using a non-azeotropic mixed as working fluid is proposed, and a secondary heat recovery device is added to the solution branch separated by the separator. Theoretical analysis and numerical calculation were used to analyze the relationships between cycle efficiency and working fluid concentration, turbine inlet pressure and cold seawater temperature were obtained. The results show that the maximum cycle efficiency can reach 5.25% by adding a secondary heat recovery device. A 10 kW OTEC experimental system was constructed and analyzed; the system performance was obtained. The efficiency of the experimental system was found to be as high as 3.8%, while the experimental value of the test system was lower than the theoretical calculation value. Finally, the heat transfer coefficients of an evaporator and condenser under these conditions were obtained, which provides basic data and technical support for the engineering application of an OTEC plant.

Switchable large-angle beam splitter based on a continuous metasurface in the near-infrared region

Metasurface-based beam splitters with broadband and high efficiency are highly desirable in various optical and photonic applications. In this paper, we theoretically propose a switchable equal power beam splitter with large beam splitting angle based on a continuous metasurface by integrating the vanadium dioxide (VO2). Utilizing the phase change characteristics of VO2, the beam splitter can be thermally switched between transmission and reflection modes in the near-infrared region. Moreover, the theoretical calculation value of the splitting angle matches well with the simulation result. And the conversion efficiencies of both transmission and reflection modes reach up to ∼100% in a broadband wavelength range. In addition, we discuss the influences of related geometrical parameters on the performance of beam splitter in detail. Our proposed switchable power beam splitter may have potential applications in integration and miniaturization of modern optical devices.

Machine Learning Design for High-Entropy Alloys: Models and Algorithms

High-entropy alloys (HEAs) have attracted worldwide interest due to their excellent properties and vast compositional space for design. However, obtaining HEAs with low density and high properties through experimental trial-and-error methods results in low efficiency and high costs. Although high-throughput calculation (HTC) improves the design efficiency of HEAs, the accuracy of prediction is limited owing to the indirect correlation between the theoretical calculation values and performances. Recently, machine learning (ML) from real data has attracted increasing attention to assist in material design, which is closely related to performance. This review introduces common and advanced ML models and algorithms which are used in current HEA design. The advantages and limitations of these ML models and algorithms are analyzed and their potential weaknesses and corresponding optimization strategies are discussed as well. This review suggests that the acquisition, utilization, and generation of effective data are the key issues for the development of ML models and algorithms for future HEA design.

Simplified approach for sizing surge tank in long-distance pipeline systems

The cross-sectional area of a surge tank (CAST) is a key factor for protecting pipelines from harm by hydraulic transients. However, for long-distance pipeline systems (LDPS), the water level fluctuations in the surge tank and valve closure water hammer normally share a coupling relationship. Traditionally, this coupling relationship renders difficulty in determining the CAST. This study focused on the influence of water level fluctuation and water hammer, and proposed a simplified approach for sizing surge tanks. First, a water hammer formula that considers the coupling effect was derived. Subsequently, formulae for sizing the CAST were deduced. Finally, a case study of an actual LDPS was conducted to verify the accuracy of the presented formulae. In addition, the calculation errors caused by the theoretical assumptions are discussed. The results indicate that the theoretical calculation values and time-domain simulation results match well, thereby demonstrating the great convenience of designing surge tanks.

Formation and strengthening mechanism of kink bands in an ultra-coarse-grained Fe-Cr-Al alloy

Fe-Cr-Al alloys, owing to their absence of allotropic transformation, require multiple cycles of rolling and recrystallization annealing processes to achieve substantial grain refinement, ultimately leading to the attainment of outstanding mechanical properties. However, the corresponding manufacturing costs will also increase greatly. In this work, we have proposed a new microstructural preparation process. Simply using warm rolling for an ultra-coarse-grained Fe-Cr-Al alloy to introduce lamellar kink bands (KBs) into the matrix, the mechanical properties can be significantly improved. By using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM), and combined with Schmid factor (SF) calculation, the formation mechanism of KBs has been revealed. When the slip plane and direction are nearly perpendicular to the loading force direction (LFD) during the continuous grain rotation, the dislocation wall will evolve into the KBs boundaries. Simultaneously, a huge orientation separation between the matrix and KBs will be produced. As strain continues to rise, KBs undergo a transformation, transitioning from low-angle-grain boundaries (LAGBs) to high-angle-grain boundaries (HAGBs), occasionally adopting a configuration as coincident site lattice (CSL) boundaries with reduced interface energy. Results of the tensile test, cyclic loading-unloading-reloading tensile test, and the strengthening calculation show that KBs can pronouncedly enhance the strength by their heterogeneous refinement on the original grains and hetero-deformation induced (HDI) strengthening effect from the dislocation density discrepancy between the matrix and internal KBs, the grains containing KBs (KBGs) and the grains without KBs (or KBs-free-grains, KFGs). The theoretical calculation value of the strengthening contribution from KBs on yield strength can be up to 225.5 MPa, with a minimum value exceeding 153 MPa. On the other hand, the ductility can be retained to some extent through stimulating the KBs boundary delamination mechanism. The present study provides a low-cost and feasible processing method for fabricating Fe-Cr-Al alloy with high strength and good ductility.

A novel energy storage system for efficiency improvement of fuel cell electric vehicles based on a new high step-up DC-DC converter

Proton exchange membrane fuel cell systems have relatively low efficiency in low power applications and have many uncertainties. In this regard, the design of a high-efficiency battery charger for fuel cell electric vehicles has been an important issue for researchers and has attracted a lot of attention in recent years. For this purpose, in this article, in the first step, with the aim of developing a battery charger with high efficiency and low cost, a new high step-up DC-DC converter with unique features is proposed. The main advantages of the proposed converter are continuous input current, high efficiency, low voltage stress on components, less component count, and high voltage gain. To prove the advantages of the proposed converter, a peer-to-peer comparison with some existing converters has been made and results are presented. In addition, this study comprehensively presents the different operating modes for the proposed converter and provides the necessary analysis and relationships for circuit operation. In the second step, this study explains the small signal modelling for the proposed converter as well as the maximum power point tracking controller for this system. In order to validate the proposed system, the values of theoretical calculations, simulation results, as well as the experimental results of the 48V-input/220V-output prototype device are presented and the results are compared side by side.

Unified strength-based elastoplastic solution for frost heaving force of cold-region tunnels considering dual non-uniform frost heaving of surrounding rock

Precise evaluation of the frost heaving force and surrounding rock plastic zone is an important basis of the prevention of freezing damage in cold-region tunnels. The temperature gradient along the radial direction of cold-region tunnels surrounding rock results in the dual non-uniform frost heaving of surrounding rock, namely, the gradual change of frost heave ratio along the radial direction and the unequal frost heaving deformation in the circumferential and radial directions. A new elastoplastic solution of tunnel frost heaving force considering double non-uniform frost heave and intermediate principal stress was derived based on the elastoplastic mechanics theory, thick-cylinder theory, and unified strength theory to better guide the frost resistance design of tunnels in cold regions. The rationality and advantages of the unified plastic solution of tunnel frost heaving force were verified by model tests and engineering examples. Results showed that the theoretical calculation value of frost heaving force was in good agreement with the measured value. When the gradual change in the frost heave ratio of surrounding rock in the radial direction was ignored, the frost heaving force and radius of the surrounding rock plastic zone were large and conservative. The solution in this paper can accurately evaluate the tunnel frost heaving force and surrounding rock plastic zone. Finally, this paper studies the influences of intermediate principal stress coefficient, the frost heaving coefficient of unit temperature of frozen surrounding rock, non-uniform frost heaving coefficient in different directions, and maximum freezing depth on the evolutionary law of frost heaving force and plastic zone of cold-region tunnels are studied.

CONSTRUCTION VERIFICATION OF UNDER-BEARING ARCH BRIDGE BASED ON CONSTRUCTION MONITORING AND TEST

In this paper, a bottom-bearing arch bridge is taken as an example to carry out the bridge construction monitoring and load tests. In order to ensure the safety of the arch bridge structure in construction and reach the internal force state of the bridge, in the construction monitoring, the construction process of the main girder type and stress, construction error and safety state is monitored. At the same time, in order to verify whether the bridge can meet the design requirements, static and dynamic load tests are carried out after the bridge is completed. The results of construction monitoring show that the stress state of the structure during the construction process is basically consistent with the theoretical calculation and design requirements, and both meet the design and code requirements. The final measured stress state of the structure is within the allowable range of the beam and arch composite bridge, and the stress state of the structure is normal and meets the code requirements. The results of load test show that the measured deflection values of the middle section of the main girder of the test hole are all less than the theoretical calculation values, and the deflection is between 1.54~3.40 mm, indicating that the bearing capacity of the structure meets the design requirements. In addition, under the four working conditions, the measured values of the transverse strain of the main girder are all less than the theoretical values, and the values are all positive. The stress at the measured points is in the tensile state, which meets the design requirements, indicating that the structure has a good elastic recovery ability after unloading. This study can provide important reference value for the construction and design of the same kind of under-bearing arch bridge.

Scattered beam control of encoded metasurface based on near-field coupling effects of elements

The coupling effect between the element structures of the traditional Huygens metasurface is easy to cause the efficiency of the designed functional devices to be reduced. In order to eliminate or reduce the coupling effect between the element structures, a border-type Huygens metasurface element structure is proposed. In order to confirm that the bounding element structure can significantly reduce the coupling effect, the near-field distribution and far-field properties of two Huygens metasurfaces with and without bounding are compared. Through comparative analysis, we find that the bounding Huygens element structure can significantly reduce the coupling effect between the element structures, and the far-field scattering angle is more consistent with the theoretical calculation value. In order to realize the free regulation of the far-field scattering angle of THz waves, we introduce the Fourier convolution principle in digital signal processing, and operate the element sequence of Huygens metasurface on the addition principle to realize the free regulation of scattered beams. In addition, we performed functional addition operations on the bounding and unbounding coding sequences. The bounding code structure can accurately achieve the synthesis of functions.

Energy consumption model of coal grinding based on energy dissipation fractal dimension

Based on particle size distribution characteristics, this paper explored the energy dissipation law in the coal ultrafine grinding process. By studying the fractal dimension of coal particle size distribution under the multi-domain fractal rule, the truncated particle size was introduced to characterize the energy consumption changes of coarse, intermediate, and fine particles. Combined with macro-energy consumption laws and three-piecewise fractal dimensions, a micro-energy consumption theory considering lattice fracture and agglomeration of ultrafine particles was proposed. On this basis, the energy consumption fractal dimension DE was proposed, and its theoretical calculation value was 2.021. The energy consumption formula of coal ultrafine grinding was established, in which energy consumption was characterized by the DE th power of the added surface area of coal particles. The DE obtained by the specific surface area and the adsorption equilibrium constant of pores were 2.285 and 2.564, respectively, which confirmed the reliability of the above theoretical analysis.

Analysis of Shear Model for Steel-Fiber-Reinforced High-Strength Concrete Corbels with Welded-Anchorage Longitudinal Reinforcement.

According to the shear capacity test results of six steel-fiber-reinforced high-strength concrete (SFHSC) corbels with welded-anchorage longitudinal reinforcement under concentrated load, the effects of shear span ratio and steel fiber volume fraction on the failure mode, cracking load and ultimate load of corbel specimens were analyzed. On the basis of experimental research, the shear transfer mechanism of corbel structure was discussed. Then, a modified softened strut-and-tie model (MSSTM), composed of the diagonal and horizontal mechanisms, was proposed, for steel-fiber-reinforced high-strength concrete corbels. The contributions of concrete, steel fiber and horizontal stirrups to the shear bearing capacity of the corbels were clarified. A calculation method for the shear bearing capacity of steel-fiber-reinforced high-strength concrete corbels was established and was simplified on this basis. The calculation results of the model were compared with the test values and calculation results of the GB50010-2010 code, the ACI318-19 code, the EN 1992-1-1 code and the CSA A23.3-19 code. The results showed that the concrete corbel with small shear span ratio mainly has two typical failure modes: shear failure and diagonal compression failure. With the increase in shear span ratio, the shear capacity of corbels decreases. Steel fiber can improve the ductility of a reinforced concrete corbel, but has little effect on the failure mode of the diagonal section. The calculated values of the national codes were lower than the experimental values, and the results were conservative. The theoretical calculation values of the shear capacity calculation model of the corbels were close to the experimental results. In addition, the model has a clear mechanical concept considering the tensile properties of steel-fiber-reinforced high-strength concrete and the influence of horizontal stirrups, which can reasonably reflect the shear transfer mechanism of corbels.

Study on distribution of sidewall earth pressure on open caissons considering soil arching effect

Based on the soil arching effect theory, the magnitude and distribution of sidewall earth pressure on open caissons when the embedded depth is large was analyzed by using theory of non-limit state earth pressure theory and horizontal differential element method. The theoretical formula was deduced. The theoretical calculation results are compared with the field test results and centrifugal model test results respectively. The results show that when the embedded depth of the open caisson is large, the distribution of earth pressure on the side wall of the open caisson first increases with the increase of embedded depth, reaches a peak value, and then sharply decreases. The peak point is located at 2/3 ~ 4/5 of the embedded depth. In engineering practice, when the embedded depth of the open caisson is 40 m, the relative error between the field test value and the theoretical calculation value is − 55.8% ~ 1.2%, with an average error of 13.8%. When the equivalent embedded depth of the open caisson in the centrifugal model test is 36 m, the relative error between the centrifugal model test value and the theoretical calculation value is − 20.1% ~ 68.0%, with an average error of 10.6%, The results are consistent well. The results of this article provides reference for the design and construction of open caisson.

Research on the Strength Calculation Method and Effects of Gear Parameters for High-Coincidence High-Tooth Gears

This article studies the calculation method for the tooth root bending stress of a high-tooth gear pair with a high contact ratio. The boundary point of the double-tooth meshing zone of the high-tooth gear pair is used as the loading point for the load, and the calculation formula for the bending stress at the dangerous section of the tooth root is obtained. By using ANSYS finite element simulation, the effect of the addendum coefficient, pressure angle, and other gear parameters on the bending stress of the tooth root is studied. The analysis shows that increasing the pressure angle will reduce the bending strength of the tooth root. Increasing the coefficient of a tooth’s top height will lead to an increase in the bending strength of the tooth root. Comparing the finite element analysis (FEA) results with the theoretical calculation results, the analysis shows that under low loads, the maximum error of the theoretical calculation values of the driving toothed gear and driven gear shall not exceed 13.53% and 15.42%, respectively. Under high loads, the maximum theoretical errors of the driving toothed gear and driven gear shall not exceed 8.78% and 10.91%, respectively. This verifies the correctness of the calculation method, which is of great significance for improving the load-bearing capacity of high-tooth gears and for guiding tooth shape design.

Three-Dimensional Temperature Field Simulation and Analysis of a Concrete Bridge Tower Considering the Influence of Sunshine Shadow

This paper forms a set of three-dimensional temperature field simulation methods considering the influence of sunshine shadow based on the DFLUX subroutine and FILM subroutine interface provided by the Abaqus platform to simulate the three-dimensional temperature field of concrete bridge towers and study its distribution law. The results show that the method has high accuracy for shadow recognition and temperature field calculation. The maximum difference between the shadow recognition results and the theoretical calculation value was only 19.1 mm, and the maximum difference between the simulated temperature and the measured temperature was 3.3 °C. The results of analyzing the temperature field of the concrete bridge tower using this algorithm show that the temperature difference between the opposite external surface of the tower column can reach 11.6 °C, which is significantly greater than the recommended temperature difference value of 5 °C in the specifications. For the concrete bridge tower, in the thickness direction of the tower wall, the temperature change was obvious only at a range of 0.3 m from the external surface of the tower wall, and the temperature change in the remaining range was small. In addition, the temperature gradient distribution of the sunshine temperature field in the direction of wall thickness conformed to the exponential function T(x) = T0e−αx + C. Additionally, the data fitting results indicate that using the temperature data at a distance of 0.8 m from the external surface as the calculation parameter in the function can achieve the ideal fitting result.

Process monitoring and terminal verification of π–section girder cable-stayed bridge

PurposeIn this paper, taking a p-section girder cable-stayed bridge as an example, the construction monitoring and load test of the bridge are implemented.Design/methodology/approachIn order to ensure the safety of cable-stayed bridge structure in construction and achieve the internal force state of the completed bridge, the construction process is monitored for liner and stress of the p-section girder, construction error and safety state during construction. At the same time, to verify whether the bridge can meet the design requirements, the static and dynamic load tests are done.FindingsThe results of construction monitoring show that the stress state of the structure during construction is basically consistent with the theoretical calculation and design requirements. The final measured stress state of the structure is within the allowable range of the cable-stayed bridge, and the structural stress state is normal and meets the specification requirements. The load tests results show that the measured deflection of the midspan section of the main girder is less than the theoretical calculation value. The maximum deflection of the main girder is 48.03 mm, which is less than 54.25 mm of the theoretical value, indicating that the main girder has sufficient structural stiffness. Under the dynamic load test, the natural frequency of the three spans of the bridge is less than the theoretical frequency.Originality/valueThis study can provide important reference value for the construction and maintenance of similar p-section girder cable-stayed bridges.

Development of Pure Torsion Test System for Micro Torsion Bars

MEMS scanners use micro torsion bars made of single crystal silicon. The push-in method is used to measure the mechanical properties of these micro torsion bars, in which a lever connected to the torsion bar is pushed. In the push-in method, the sliding force increases as the indentation amount increases, decreasing measurement accuracy. As a method to reduce the sliding force, we proposed to generate pure torsion in the torsion bar section by rotating a sample holder with a test sample attached. The proposed method can maintain the load detection axis of the load cell and the lever part at almost a right angle regardless of the degree of torsional angle, preventing slip at the contact point between the load cell and the lever part. The torsional spring constants of test samples were obtained and compared by three different methods: a testing system using this principle, a resonance frequency method, and a theoretical calculation. The accuracy of the developed testing system is -17.5 % to 12.7 % of the measurement error compared to the torsion beam spring constant obtained from the resonance frequency, and -15.6 % to 7.2 % compared to the theoretical calculation value, thus verifying the effectiveness of the proposed test method.

Breaking law of overlying strata in shallow coal seam fire area under thermal–mechanical coupling effect

AbstractThe cracks formed by the breaking and collapse of the overlying strata are the oxygen supply channels for the continuous combustion of coal fires. The development of cracks is of great significance for determining the scope of the fire area and controlling the fire efficiently and accurately. To study the development law of cracks, a breaking model of the overlying strata in the shallow coal seam fire area is established on the basis of beam theory considering the coupling effect of gravity load and temperature field. The physical model of the coal fire is established based on the similarity principle. The temperature data from rock strata in the model are monitored by the infrared thermal imager. The dynamic distribution function of the roof temperature field is obtained by fitting. According to the breaking model theory, the position of the maximum tensile stress on the roof of the shallow fire area is the middle of the lower surface. The theoretical calculation value of the first breaking distance of the roof is 0.575 m, which is consistent with the experimental results of the physical model. The maximum tensile stress of the roof under the thermal‐mechanical coupling is slightly less than that under the load only. For shallow coal seams, the thermal stress generated by the coal fire increases the first breaking distance of the roof.