Method For Calculation Of Coefficients Research Articles

Coupling coefficient calculation method of circular coil with bilateral finite magnetic shields at horizontal misalignment in wireless power transfer systems

AbstractThe coupling coefficient determines the transfer efficiency of the wireless power transfer (WPT) system. The magnetic leakage can be reduced, and the coupling coefficient of the coil can be enhanced by adding a magnetic shield. Thus, the transfer efficiency of the WPT system can be improved. However, when the receiving coil is added with magnetic shield and occurs horizontally misaligned, the coupling coefficients between the coils with the magnetic shield can only be calculated by finite element simulation, and there is no calculation method for the coupling coefficient of two circular coils with bilateral finite magnetic shield at horizontal misalignment. Therefore, based on Maxwell's equations and Bessel's function, the formula of the coupling coefficient between circular coils at coaxial is derived by the subdomain hierarchical analysis (SHA) method. On this basis, the coupling coefficient calculation formula between circular coils at horizontal misalignment is further derived by using the boundary vector equivalence (BVE) method. The results show that the maximum experimental error is not more than 5.58%, and the longest average time of the algorithm is not more than 1.282 s, which verifies the effectiveness and rapidity of the proposed method.

Vision-based detection of bolt tension considering non-rotatory loosening via a new calculation method of bolt flexibility coefficient

Bolted joint is widely used in construction, vehicle, aerospace, and other engineering fields. Bolt tension is the most important performance index of bolted joints. The whole life cycle monitoring of bolt tension without contact and damage can be realized by vision-based method. The existing methods indirectly predict the change of bolt tension by calculating the rotary angle of the nut. This kind of method can judge the loosening caused by nut rotation but cannot deal with the non-rotary loosening. At the same time, the relationship between nut rotation angle and loosening must be obtained through calibration experiments. This paper proposes a vision-based method to measure the change of bolt tension considering the non-rotary loosening by detecting the change of bolt elongation. Based on VDI2230 and finite element analysis, a new calculation method of bolt flexibility coefficient is proposed. The experimental results show that this method can measure the change of bolt tension with high precision in the process of tightening and loosening.

Dynamic Flow and Heat Transfer Characteristics of Uncracked Hydrocarbon Fuel under Super-Critical Pressure in the Cooling Channel of a Regeneratively Cooled Scramjet

Regeneratively cooled scramjets are successfully used as propulsion devices in hypersonic vehicles. During operation, scramjets experience acceleration. This special process causes a dynamic flow process, and heat transfer in the cooling channel commonly occurs, which may cause hazards and control difficulties for scramjets. A dynamic numerical model with a modified heat transfer coefficient calculation method was established to study the transient flow and heat transfer processes in a cooling channel. The dynamic characteristics of the flow and heat transfer under different conditions were calculated and are discussed, including the changes in the inlet fuel mass flow, heat flux, and pressure working conditions. The results indicate that the stable time of the cooling channel outlet fuel temperature is related to the rate of change in the inlet mass flow and heat flux. The stable time of the outlet fuel temperature under decreasing heat flux working conditions was approximately 12.5 s. These results summarize the dynamic flow and heat transfer characteristics, which are significant for designing cooling channels in scramjets.

Wind-induced responses for cable net structures considering punching rate of reflecting panels

The datum surface of the active reflector of the Five-hundred-meter Aperture Spherical radio Telescope (FAST) is a spherical crown with a radius of 300 m and an aperture of 500 m. The reflector is supported on a cable net structure. Due to its sensitivity to wind loads, it is imperative to investigate its aerodynamic characteristics and wind-induced vibration response. This paper explores the aerodynamic characteristics of the reflecting panel through computational fluid dynamics (CFD). Compared with the nonporous panel, the drag coefficient of the reflecting panel with a punching rate of approximately 50% increases by approximately 51%, and the main reason is that the resistance changes little, but the projected area decreases by 50%. On this basis, the calculation method of the aerodynamic coefficient of the reflecting panel under arbitrary wind direction angle is established. Then, the simulation model of the active reflector system is established, and the wind-induced vibration response is analyzed under different wind speed conditions. The displacement and stress responses of the cable net structure, ring beams, and lattice columns are studied, and the gust response factors (GRFs) are calculated. The results show that the wind load has a very strong effect on the nodal displacement and column bottom stress but has little effect on the stress of the cable net structure; the displacement GRFs of the cable net structure, ring beams, and lattice columns increase with increasing wind speed, of which the simulated results can provide a reference for the design of similar projects.

Experimental verification of the novel transcritical CO2 heat pump system and model evaluation method

This work proposes a novel method for verifying the accuracy of the numerical simulation model of the compression/ejector transcritical CO2 heat pump system using convolutional neural networks. The method focuses on converting the original unequal input conditions into equal input conditions and comparing the simulation results with the experimental prediction results of each component. The validation results reveal the following findings: 1) The root mean square errors of the gas cooler and the water source evaporator are 9.16 °C and 11.47 °C respectively, indicating that future work should focus on correcting of the CO2 heat transfer coefficient calculation method; 2) The verification results of the evaporator indicate that suggesting the need to incorporate an air dynamic change module in the air source input; 3) The root mean square error of the CO2 outlet pressure in the ejector is 462.45 kPa. It can be inferred from the pressure variation trend that the limit pressure ratio of the compressor is the main factor affecting the accuracy of the ejector model. Overall, this article presents a novel and effective method for verifying the accuracy of numerical models.

Mechanism analysis and optimal design of sound-absorbing metastructure constructed by slit-embedded Helmholtz resonators

Low-frequency noise has always been a thorny problem in the field of noise control. In recent years, the development of sound-absorbing metastructures has provided new ideas for low-frequency noise control. In this paper, we propose low-frequency sound-absorbing metastructures constructed by Helmholtz resonators with embedded slit. Analytical and numerical models were established to analyze the sound absorption performance and mechanism of the proposed sound-absorbing metastructure, and optimization design was conducted to achieve low-frequency wideband absorption performance. The analytical modeling method and the performance of the proposed sound-absorbing metastructure were also experimentally verified. The main conclusions are summarized as follows:<br>1) Based on the use of transfer matrix method and finite element method, analytical and numerical models for calculation of sound absorption coefficient were established. It was shown that analytical predictions are in good agreement with numerical calculations. It was demonstrated that a typical design of a single-cell metastructure with 30mm thickness can achieve a sound absorption coefficient of 0.88 at 404 Hz. Typical designs of two-cell and the four-cell parallel structures (with 50 mm thickness) can achieve two and four near-perfect low-frequency sound absorption peaks within the frequency band of 200-400 Hz, respectively.<br>2) The low-frequency sound absorption mechanisms of the proposed metastructure were explained from four aspects: simplified equivalent model parameters, normalized acoustic impedance, complex-plane zero/pole distribution, sound pressure cloud image and particle velocity field distribution. It was demonstrated that the main sound absorption mechanism is associated with the thermal viscous loss of sound waves caused the inner wall of embedded slit.<br>3) Optimization design for broadband low-frequency absorption performance was carried out by using differential evolution optimization algorithm. A parallel-multi-cell coupled metastructure with multiple perfect sound absorption peaks below 500Hz was optimized. Under the condition of thickness 90mm, the sound absorption coefficient curve of an optimized metastructure exhibited 8 near-perfect sound absorption peaks and an average sound absorption coefficient of 0.86 within the frequency range of 170-380 Hz.<br>4) Experimental samples were fabricated to carry out sound absorption tests. Experimental results were basically consistent with the analytical predictions. Mutual verification of analytical model, numerical calculation and experimental measurements was completed.<br>To sum up, the sound-absorbing metastructures proposed in this paper have outstanding sound absorption performance at low frequencies with sub-wavelength thickness. We demonstrated they are suitable for low frequency broadband sound absorption below 500 Hz. Thanks to their thin thickness and relatively simple construction, they have broad application prospects in practical noise control engineering.

A fast matrix-based method for two-phase and three-phase daylight simulations

This study introduced a sequential contribution coefficient calculation method with an ambient cache to expedite the computation of daylight coefficient (DC) matrices and view matrices for the two-phase method (2-PM) and three-phase method (3-PM) in daylight simulations. This innovation resulted in the development of swifter two-phase and three-phase methods. Additionally, a novel tool for high-speed matrix multiplication was developed to enhance climate-based daylight modeling. The results demonstrate the effectiveness of the proposed sequence contribution coefficient calculation, showing a reduction in computation time for the DC matrix by 53.1% and 55.8% for 145 sky patches and 1297 sky patches, respectively. Furthermore, the view matrix computation time shows an impressive reduction of 86.4%. The tool for rapid matrix multiplication further contributes to a reduction in computation time exceeding 80%. Overall, the fast two-phase method and three-phase method achieve a reduction in computation time exceeding 60% and 80%, respectively, compared to the original two-phase and three-phase methods. Notably, the simulation results affirm that the accelerated matrix-based method does not compromise the accuracy of glare metric calculations.

Thermal analytical modeling of machine tool structural components via dual-layer equivalence

Precision machine tools are sensitive to thermal effects. Thermal deformation of machine tool structural components can lead to changes in the relative pose between the spindle tool and the workpiece, causing thermally induced machining errors. Gaining insight into the mechanistic correlation between critical thermal condition parameters of heat sources and thermal errors in machine tools is essential to elevate the design of machine tool thermal attributes. To address this issue, this paper proposes a dual-layer equivalent analytical modeling method for characterizing the thermal properties of structural components. The construction of the temperature field analytical model for the dual-layer equivalent structure is achieved by setting and handling different interlayer heat flows and temperature boundary conditions. The dual-layer equivalent approach simplifies complex structural components into top and bottom layers, providing a more flexible and accurate capability for characterizing the thermal properties of structural components. This modeling method enables rapid prediction and evaluation of machine tool thermal characteristics. Furthermore, based on this analytical approach, the calculation method of sensitivity coefficient of thermal power to thermal error is proposed to elucidate the mapping relationship between different thermal condition parameters and thermal errors. This method facilitates the fast and accurate prediction of six thermally induced errors under various thermal conditions. Experimental results demonstrate that the key point temperature deviation predicted using the dual-layer analytical modeling method is less than 0.8 °C, and the thermally induced axial linear error deviation is less than 1.8 μm. The dual-layer analytical modeling approach introduced in this study presents a versatile technique applicable to enhancing the design and control of machine tool thermal characteristics, holding significant potential for advancing the stability of machine tools thermal accuracy.

Modeling for on-line monitoring of carbon burnout coefficient in boiler under partial load

Combustion stability of boiler deteriorates under low load, making carbon burnout coefficient decrease, further reducing boiler thermal efficiency. The online monitoring methods of carbon burnout coefficient and boiler thermal efficiency can track energy efficiency levels of boiler in real-time under low loads. It is of great practical significance to optimize and adjust combustion conditions of boilers and upgrade boiler real-time energy efficiency. Nevertheless, extremely difficult challenge for online monitoring technology of carbon burnout coefficient seriously restricts the online monitoring of boiler thermal efficiency.In this background, an innovative theoretical model between excess air coefficient and carbon burnout coefficient is derived according to incomplete combustion equation inside furnace. Calculation method of excess air coefficient is proposed with a brand new perspective on energy balance of economizer. Subsequently, on-line monitoring model of carbon burnout coefficient and boiler thermal efficiency is constructed and verified.The online monitoring results of a 600 MW unit indicate, lower carbon burnout coefficient magnifies the degree of virtual height of calculation results and calculation error from traditional methods of national standard for calculating excess air coefficient. This operating mode results in a significant shortage of actual air flow into boiler under partial load.Carbon burnout coefficient, showing an upward trend with unit load increasing, is as high as 0.99 with unit load of 489 MW. As unit load decreases to 161 MW, carbon burnout coefficient decreases to 0.80. Additionally, combustion conditions fluctuation is greatly influenced by changing in coal quality. Under partial load, volatility in carbon burnout coefficient increases with electrical load below 300 MW. Combustion stability and combustion efficiency of boiler under low load significantly decrease. The variation in exhaust flue gas heat loss of boiler with unit load changes is relatively small due to opposite effect by exhaust gas temperature and excess air coefficient. Actually, changing trends and fluctuation degree of boiler thermal efficiency are mainly influenced by carbon burnout coefficient with a variation in load. Overall, boiler thermal efficiency, affected by heat loss of incomplete solid on combustion, fluctuates greatly at low loads. The implementation of online monitoring for carbon burnout coefficient provides a quantitative basis for improving boiler energy efficiency under low load conditions.

Influence of blocking ratio on hydrodynamic force on deep-water pier under earthquake

The deep-water bridge would suffer more serious damage under earthquake than that standing in air. The larger blocking ratio has remarkable effect on the added mass coefficient, which deserves a further and comprehensive study. The generation mechanism of block effect is analyzed by using the numerical simulation software ANSYS Fluent. Results show that the recirculation zone with focus decreases the pressure on the rear surface of the cylinder, results in the peak value of the in-line force does not occur synchronously with the peak value of acceleration. Results also indicate that the change of the position and intensity of the recirculation zone with focus, as well as the change of the water flow around the cylinder surface, are the generation mechanism of the block effect, the block effect has a 10% influence on the hydrodynamic force. The added mass coefficient changing rule with blocking ratio is then discussed elaborately, and the modification approach to the present added mass coefficient calculation method is suggested. Finally the physical experiments are conducted to validate the modification approach, results shows the modification approach is accurate and can be used both in the further study and in real practice.

Automatic Identification Method of Defects in Concrete Structures Strengthened with Composite Materials Based on a Multi-Scale Model

Due to the inconsistent geometric characteristics of reinforced concrete structures with composite materials, some echo signals have a lower degree of clarity, resulting in problems such as long time, small range, and low accuracy in identifying structural defects. Therefore, in order to improve the accuracy and efficiency of defect identification in composite material reinforced concrete structures, a multi-scale model based on the automatic defect identification method for composite material reinforced concrete structures is proposed. Using the interface connection method, based on continuous distribution coupling and the uniform weighting coefficient calculation method to weigh the interface nodes, we determined the interface connection mode and analyzed the stress–strain relationship. The impact echo method was used to analyze the degree of high-frequency stress wave scattering caused by internal non-uniformity in composite reinforced concrete, and the fast Fourier transform conversion algorithm was used to generate amplitude–frequency curves and resolved thickness or defect depth. The experimental results show that the multi-scale finite element simulation structure of this method is clear and accurate, and although there are errors, they do not affect the simulation results of the structure. The impact echo detection effect is obvious; it can automatically identify defects in composite reinforced concrete structures and quickly and accurately identify defects in different states and positions of composite reinforced concrete, with a recognition accuracy of 98%.

Feasibility Analysis of Compressed Air Energy Storage in Salt Caverns in the Yunying Area

With the widespread recognition of underground salt cavern compressed air storage at home and abroad, how to choose and evaluate salt cavern resources has become a key issue in the construction of gas storage. This paper discussed the condition of building power plants, the collection of regional data and salt plant data, and the analysis of stability and tightness. Comprehensive analysis and evaluation methods were put forward from four aspects, including ground comprehensive conditions, regional geological conditions and formation lithology, salt mine characteristics, stability, and tightness of salt caverns. The limit equilibrium theory was applied to establish the limit equilibrium failure mode of salt caverns under operating pressure, and the stability coefficient calculation method of the target salt cavern was determined by combining the mechanical characteristics. Based on the physical and mechanical properties of salt rocks, it was found that salt rocks with enough thickness around the salt cavity could be used as sealing rings to ensure the tightness of the salt cavern. Combined with the field water sealing test, the tightness of the target salt cavern is verified. This method has been applied to the salt cavern screening and evaluation of a 300 MW compressed air energy storage power plant project in Yingcheng, Hubei Province, and remarkable results have been obtained, indicating the rationality of the method.

The Influence of Different Shear Directions on the Shear Resistance Characteristics of Rock Joints

The joint roughness coefficient JRC of rock joints is an important parameter for measuring the geometric morphology of rock joints. However, the parameter obtained from traditional calculation methods has certain limitations in reflecting the differences in shear strength of rock joints in different shear directions with the same orientation. Firstly, native joint surface test blocks were cast using three-dimensional reverse reconstruction technology. Subsequently, direct shear tests were conducted under different normal stress and shear direction conditions, followed by numerical simulations using the finite difference software Flac3d. The JRC coefficient calculation method proposed by Yuan was modified and extended by considering the percentage of climbing sections and the effective contact area during the ramping process. This study indicates that the numerical simulation results are in good agreement with the shear test results. The introduction of the shear climbing rate SCR and the curvature coefficient of profile CCP is used to reflect the geometric differences of the joint surfaces in different shear directions. These two parameters are nonlinearly fitted with the experimental results, leading to a calculation formula that characterizes the shear strength characteristics of the joint surfaces in different shear directions. This novel formula is an extension of the JRC–JCS model.

ПАРАМЕТРИЧЕСКИЙ МЕТОД РАСЧЕТА ТРЕУГОЛЬНЫХ ВЕСОВЫХ КОЭФФИЦИЕНТОВ В МАТРИЦЕ ПОПАРНЫХ СРАВНЕНИЙ

The article deals with development of the method for calculation of triangular weight coefficients in fuzzy problem of decision making. The study objective is to improve the accuracy of triangular weight coefficient determination. In order to achieve the above-mentioned objective, a set of methods of scientific and empirical investigation: analysis and splitting of the problem into two tasks, methods of mathematical programming and fuzzy logic, method of comparison. The required weight coefficients are represented in a parametrical form with unlike fuzzy parameters which allowed for two tasks to be separated and formalized: determination of modal values and the task to determine fuzziness parameters. Both tasks have been formulated in terms of non-linear mathematical programming. The proposed method differs from the known ones by using the parameters of triangular numbers fuzziness as optimized variables which are assumed to be different for the left and right borders in all weight coefficients.
 The proposed approach allowed for the accuracy of weight coefficients to be improved. The accuracy validation was conducted comparing with the known LLSM method on two matrices. The calculations have demonstrated that the integral absolute error of the proposed method more than twice smaller than that of the know method for each of the matrices.

Research on the importance and structural vulnerability assessment of RC frame components and robustness improvement methods

ABSTRACT To reasonably evaluate the robustness of RC frame structures, the ability to resist continuous collapse is improved. In this paper, the members’ contribution to the bearing capacity of the structure and the impact of the member’s failure are comprehensively considered, and the calculation method of the importance coefficient of the member is improved. At the same time, the structural vulnerability coefficient based on the change of the strain energy of the structure is combined with the reasonable assessment of the structural robustness through the two aspects of the member and the structure finishing. The redundancy analysis of the peripheral components of the failed components is carried out, and the low redundancy components are strengthened to improve the robustness of the structure to achieve the purpose of “strengthening the part and improving the whole”. On this basis, this paper evaluates the robustness of a four-story RC frame structure. It strengthens the low redundancy components under the influence of failure components to meet the requirements of improving the robustness of the structure, which verifies the rationality of the robustness evaluation method of the RC frame structure in this paper and the feasibility of improving the robustness of the structure.

Depth-resolved method for attenuation coefficient calculation from optical coherence tomography data for improved biological structure visualization.

Optical coherence tomography (OCT) is a promising tool for intraoperative tissue morphology determination. Several studies suggest that attenuation coefficient derived from the OCT images, can differentiate between tissues of different morphology, such as normal and pathological structures of the brain, skin, and other tissues. In the present study, the depth-resolved method for attenuation coefficient calculation was adopted for the real-world situation of the depth-dependent OCT sensitivity and additive imaging noise with nonzero mean. It was shown that in the case of sharp focusing (~10 μm spot full width at half maximum [FWHM] or smaller at 1.3 μm central wavelength) only the proposed method for depth-dependent sensitivity compensation does not introduce misleading artifacts into the calculated attenuation coefficient distribution. At the same time, the scanning beam focus spot with FWHM greater than 10 μm at 1.3 μm central wavelength allows one to use multiple approaches to the attenuation coefficient calculation without introducing noticeable bias. This feature may hinder the need for robust corrections for the depth-resolved attenuation coefficient estimations from the community.

Design method of HSS welded H-section beams subjected to bending-shear combination

High-strength steel (HSS) welded H-section beams are increasingly used in steel structures considering their advantage of high strength, but the stability is a concern especially near the supports, where the beams are prone to buckling under the combined actions of bending and shear. In this paper, finite element method was used to analyze the mechanical performance of HSS welded H-section beams under shear and bending-shear loads. A parametrical analysis for the H-section beams under pure shear loads was conducted, and a new shear buckling coefficient calculation method considering the interaction between plates was proposed. This coefficient was then applied to calculate the shear strength, and a design method for shear buckling strength based on the direct strength method (DSM) was proposed. Finally, a new bending-shear interaction curve was developed to predict the ultimate resistance of HSS welded H-section beams under bending-shear combination, and the reliability analysis results demonstrate the feasibility and safety of the design method proposed in this paper for HSS welded H-section beams.

Effect of carbon black components on rolling mechanical properties of tread rubber material by using improved digital image correlation

AbstractThe rolling and sliding state of the tread rubber material within contact patch was very important to the handling stability and safety of the vehicle. In this paper, first, the absolute coordinate system was introduced into the digital image correlation method, which improved the ability of the traditional digital image correlation method to solve the large deformation of polymer material surface. Second, a new calculation method of rolling friction coefficient based on the brush model was proposed. Third, a non‐contact full‐field rolling dynamics experimental device was developed to study the effects of carbon black components, rotational speed and vertical load on the rolling mechanical characteristics of tread rubber material. On this basis, the rolling mechanical characteristics of tread rubber material with different formulations were obtained by analyzing the distribution properties of global strain rate, full‐field longitudinal speed and full‐field longitudinal acceleration and the variation laws of transverse/longitudinal strain rate, trajectory of marked points, stress‐strain hysteresis curve and rolling friction coefficient. Finally, the influence mechanism of carbon black composition on rolling mechanical properties of tread rubber material was revealed.

Clustering Analysis of Multilayer Complex Network of Nanjing Metro Based on Traffic Line and Passenger Flow Big Data

Complex networks in reality are not just single-layer networks. The connection of nodes in an urban metro network includes two kinds of connections: line and passenger flow. In fact, it is a multilayer network. The line network constructed by the Space L model based on a complex network reflects the geographical proximity of stations, which is an undirected and weightless network. The passenger flow network constructed with smart card big data reflects the passenger flow relationship between stations, which is a directed weighted network. The construction of a line-flow multilayer network can reflect the actual situation of metro traffic passenger flow, and the node clustering coefficient can measure the passenger flow clustering effect of the station on adjacent stations. Combined with the situation of subway lines in Nanjing and card-swiping big data, this research constructs the line network with the Space L model and the passenger flow network with smart card big data, and uses these two networks to construct the multilayer network of line flow. This research improves the calculation method of the clustering coefficient of weighted networks, proposes the concept of node group, distinguishes the inflow and outflow, and successively calculates the clustering coefficient of nodes and the whole network in the multilayer network. The degree of passenger flow activity in the network thermal diagram is used to represent the passenger flow activity of the line-flow network. This method can be used to evaluate the clustering effect of metro stations and identify the business districts in the metro network, so as to improve the level of intelligent transportation management and provide a theoretical basis for transportation construction and business planning.

Temperature field model of limited slip clutch based on dynamic heat flux partition characteristics

The interaxle torque distribution of off-road vehicle is interfered with temperature field variation of limited slip clutch during long-time sliding, which is controlled by actual heat flux input. The equivalent heat dissipation model is created based on the suggested calculation method of convective heat transfer equivalent coefficient in various lubrication phases. Further, thermal equilibrium equations of friction pair nodes are solved to produce the temperature field calculation model of dynamic heat flux partition. A clutch sliding bench is set up to verify and analyze the effect of heat flux partition on temperature field by organizing different operating conditions. The results demonstrate that the temperature difference of contact surface calculated by the constant heat flux partition model increases significantly along with sliding time and heat flux. In addition, the deviations of temperature rising rate at stage A and average temperature at stage B of separator plate higher than the experimental result also increases. On the contrary, the decrease value of actual input heat flux of separator plate from initial to steady state gradually increases with the increase of relative speed difference in dynamic heat flux partition model. The calculation deviations of temperature rising rate and average temperature are less than 0.1°C/s and 3°C, respectively. This model offers a novel approach for calculating clutch temperature field.