Theoretical Calculation Method Research Articles

Structural model and capacity determination of underground reservoir in goaf: a case study of Shendong mining area in China

The large-scale extraction of coal resources in the western mining areas of China has resulted in a significant loss of water resources, which is a challenge for coordinating resource extraction with ecological preservation in the mining areas. Although underground reservoir technology can effectively solve this problem, measuring the storage capacity of underground reservoirs through engineering experiments is costly and time-consuming. Currently, there is a lack of accurate, reliable, and low-cost theoretical calculation solutions, which greatly restricts the promotion and application of underground reservoir technology. The theoretical calculation methods for underground reservoir capacity were studied based on parameters from the Shendong mining area in China. A water storage structure model for coal mine underground water reservoirs was established, taking into account the settlement boundaries of the bedrock and loose layers in shallow coal seams, based on the key layer theory and the spatial structure model of the mining roof. The mathematical expression for the load on the coal-rock mass in the goaf was derived considering the rock breaking characteristics of the mining roof. The model determined the range of each water storage area, including the zone of loose body, zone of gradual load, and the compacted zone, based on the strength of the water storage capacity. The key parameters for calculating the water storage capacity were determined using a modified model for shallow thick loose layers and thin bedrock movement. Finally, a calculation method for the storage capacity was obtained. Based on the real data from the 22,615 working face of a mine in the Shendong mining area, the water storage capacity of the underground reservoir in the goaf was jointly calculated using FLAC3D, Surfer 12.0 and the proposed calculation method. The calculated water storage capacity was approximately 1.0191 million m3. Although this result was 2.20% smaller than the on-site water pumping experiment data, it still verifies the feasibility of the above calculation method for determining the water storage capacity of underground water reservoirs.

Flexural behavior of open-web composite slab with I-shaped steel bottom chord and vertical flat webs

Traditional composite floor truss systems with top and bottom chords and web trusses have encountered difficulties in system erection, installation, and the passage of utilities. In order to address these challenges, this study introduces a novel open-web composite floor system that only consists of a bottom chord and vertically placed flat web elements. These vertical web members are essentially short I-shaped steel elements and are connected to the I-shaped steel beam bottom chord and concrete slab through steel top plates and shear connectors, forming an innovative composite floor system. This paper presents the results of static loading tests conducted on two specimens with distinct web members, evaluating deformation, cracking characteristics, ultimate bearing capacity, failure mode, and stress and strain distributions. The findings indicate that the new composite floor system offers good flexural performance. Furthermore, finite element models of the composite floor system have been developed to analyze the influence of the web element’s geometry on the composite slab’s ultimate bearing capacity. This study also develops a theoretical calculation method for determining the internal force, elastic deflection, and ultimate bearing capacity of the composite floor system. The theoretical calculation results regarding the failure mode and ultimate load capacity align closely with the experimental values, and the deformation calculation formula can be used to estimate the deformation curve shape and elastic deflection of the floor system.

Study on filling mining technology for gently inclined thin to medium thick phosphorus deposits

This study is grounded in research conducted at the Kunyang Phosphate Mine No. 2, a Chinese open-pit phosphate mining enterprise owned by the Yunnan Phosphate Group Co., Ltd. Due to the small inclination angle and the presence of weak interlayers in the middle of the gently inclined thin to medium thick phosphate ore layer, mining such ore bodies cannot rely on self weight migration, making roof management difficult and mining costs high technical challenges. The methods utilized on-site research, engineering comparisons, and theoretical analysis experiments to address the gently inclined phosphorus deposits. Based on the actual technical and economic conditions of current phosphorus mines, the advantages, disadvantages, and practical conditions of upward horizontal layered filling mining method, upward horizontal layered drift filling mining method, and pseudo inclined segmented strip filling mining method are compared. Priority should be given to using the pseudo inclined segmented strip method as the main method for mining, supplemented by the upward horizontal layered filling method in the panel area. And theoretical calculation methods were applied to obtain various numerical values of the filling capacity of the 2 million t/a mine filling test section, providing technical support for the mining design and equipment selection of the filling test system. The relevant research results can provide guidance for the selection of mining methods for gently inclined thin to medium thick phosphate deposits with an average inclination angle of 15°. The theoretical calculation method used can provide technical guidance for the filling system and filling equipment.

Thermal expansion characteristics of high energy insensitive explosive α-NTO

ABSTRACT Thermal expansion is an important structural parameter to evaluate the structural stability and performance reliability of energetic materials. In order to further understand the thermal expansion characteristics and mechanism of high-energy insensitive explosive 3-nitro-1, 2, 4-triazol-5-one (NTO), the thermal expansion characteristics of α-NTO were studied by in-situ X-ray diffraction (XRD) technique. Based on the Rietveld full-spectrum fitting structure refinement principle, the thermal expansion coefficient of α-NTO was obtained. The results show that α-NTO exhibits obvious reversible anisotropic thermal expansion under the action of thermal field. Based on infrared and Raman spectroscopy combined with theoretical calculation methods, the crystal packing structure of α-NTO at different temperatures and its correlation with thermal expansion characteristics were studied. It is believed that the functional groups that produce hydrogen bonds and hydrogen bond receptors in the crystal structure of α-NTO under thermal stimulation play a leading role. At the same time, compared with the thermal expansion characteristics of other explosive crystals, the influence of crystal packing on the thermal stability of explosive crystal structure was analyzed. The results show that the thermal expansion anisotropy of layered packing explosive crystals with strong hydrogen bonding is more obvious.

Theoretical Calculation and Experimental Verification of Wind-Driven Rain Aerodynamic Forces on the Bridge Main Beam

Regarding the issue of changes in the aerodynamic force of the bridge main beam under the action of wind-driven rain, this article explores the changes in air density caused by rainfall, the calculation theory of raindrop impact force and its simplified mass-weighted equivalent method (MWEM), and the calculation method of water accumulation thickness on the surface of the main beam. The calculation shows that the changes in air density caused by rainfall can be ignored, and the error of the MWEM increases with the increase in rainfall intensity; however, even at a rainfall intensity of 709 mm/h, the deviations in the MWEM value of the horizontal and vertical raindrop impact force is only about +5% and −4%, respectively. Then, based on the above analysis, a calculation model for the aerodynamic three-component forces of the main beam caused by rainfall under the action of wind-driven rain is provided. Finally, taking two typical main beam sections as an example, static three-component force tests are carried out on the main beam model under different rainfall intensities. The experimental results show that the drag coefficient variations obtained through the MWEM are in good agreement with experimental data, which proves the correctness of the theoretical model of the raindrop impact force. But for the lift and torque coefficient, the differences between theoretical and experimental values are much more significant than the drag coefficient, and it increases with the increase in rain intensity. It can be seen that the surface ponding model and influence of rainfall intensity need to be further explored. In summary, the theoretical calculation method for the additional aerodynamic force of wind-driven rain on the main beam proposed in this article is convenient and practical, and it can provide a certain reference for the rapid safety assessment of bridges under extreme meteorological conditions.

Experimental study on the eccentrically compressive performance of square masonry columns repaired with UHPC jackets

Ultra-high performance concrete (UHPC) is a new class of structural material with outstanding properties of high strength, excellent ductility, and durability, which has an extremely broad application field. To examine the rehabilitation potential of UHPC on the existing masonry structures, the mechanical behavior of square masonry columns strengthened with UHPC under eccentric loading was investigated in this paper. A total of six masonry columns with or without the confinement of UHPC jackets were axially and eccentrically loaded. The strengthening effectiveness of UHPC on masonry columns was explored in terms of failure mode, deformation capacity, and carrying capacity. The results showed that UHPC jacketing is a highly effective technique for strengthening masonry columns, significantly increasing both the load-carrying capacity and transverse deformability of eccentrically compressed masonry columns (up to 103.64% and 71.43%, respectively). Furthermore, the UHPC strengthening technique modified brittle damage in unconfined masonry columns. A theoretical calculation was carried out for determining the bearing capacity of masonry columns strengthened with UHPC under eccentric loading. The accuracy of the theoretical calculation method was verified by comparing the theoretical values with the experimental values. Thus, this study provides a theoretical basis for the practical application of masonry structures strengthened with UHPC.

Accurate Prediction of Adiabatic Ionization Energies for PAHs and Substituted Analogues.

The accurate calculation of adiabatic ionization energies (AIEs) for polycyclic aromatic hydrocarbons (PAHs) and their substituted analogues is essential for understanding their electronic properties, reactivity, stability, and environmental/health implications. This study demonstrates that the M06-2X density functional theory method excels in predicting the AIEs of polycyclic aromatic hydrocarbons and related molecules, rivaling the (R)CCSD(T)-F12 method in terms of accuracy. These findings suggest that M06-2X, coupled with an appropriate basis set, represents a reliable and efficient method for studying polycyclic aromatic hydrocarbons and related molecules, aligning well with the experimental techniques. The set of molecules examined in this work encompasses numerous polycyclic aromatic hydrocarbons from m/z 67 up to m/z 1,176, containing heteroatoms that may be found in biofuels or nucleic acid bases, making the results highly relevant for photoionization experiments and mass spectrometry. For coronene-derivative molecular species with the C6n2H6n chemical formula, we give an expression to predict their AIEs (AIE (n) = 4.359 + 4.8743n-0.72057, in eV) upon extending the π-aromatic cloud until reaching graphene. In the long term, the application of this method is anticipated to contribute to a deeper understanding of the relationships between PAHs and graphene, guiding research in materials science and electronic applications and serving as a valuable tool for validating theoretical calculation methods.

Cracking and damage analysis of a masonry structure based on joint masonry model caused by a obliquely undercrossing tunnel

The damage variation of a masonry structure during shield tunneling has been investigated. Furthermore, the damage degree of the masonry building has been investigated by combining the field measurement, finite element method results, and theoretical method. The results show that compared with the theoretical calculation method LSTM, the method provide by this paper can give the detail damage location of the masonry structure caused by shield construction. Due to the existence of door and window openings, the result of JMM is larger than LSTM result, the differences can be modified by concept of “characteristic tensile strain”. The wall of the masonry building encounter the shield face first suffers more damage than the later ones. At the beginning of tunnlling, the damage were generated from a small area at the bottom for wall 1, but a larger area at the top of the building for wall 2. The damage area increase more at the top of the building as tunneling advanced, but the maximum damage occurred at the bottom of the building.

Paying Comprehensive Attention to the Temperature-Dependent Dual-Channel Excited-State Intramolecular Proton Transfer Mechanism of Fluorescence Ratio Probe BZ-DAM.

The mechanism of fluorescence detection of diethyl chlorophosphate (DCP) based on 2-substituted benzothiazole (BZ-DAM) was studied by a theoretical calculation method. It should not be ignored that both the BZ-DAM and the detection product BZ-CHO have two excited-state intramolecular proton transfer (ESIPT) channels. Density functional theory (DFT) and time-dependent DFT (TDDFT) theory were used to study the photophysical mechanism of two compounds in two channels in (acetonitrile) ACN solvent, and the temperature dependence of the two channels was given. Channel 1 is more likely to exist at low temperatures and channel 2 is more likely to exist at high temperatures. By theoretical analysis of the constructed potential energy curve, the hydrogen bond energy and electron-hole analysis, we confirmed that both molecules undergo ESIPT and intramolecular charge transfer (ICT) processes in channel 1 and ESIPT and twisted intramolecular charge transfer (TICT) coupling processes in channel 2. The formation of product BZ-CHO molecules led to a significant fluorescence blue-shift phenomenon and inhibited the ICT process, which confirmed that BZ-DAM could be used as a fluorescence probe for fluorescence detection. We sincerely hope that this work will not only help to clarify the excited-state dynamics behavior of the BZ-DAM probe but also provide a new idea for designing and optimizing a new chemical dosimeter.

Moment-Rotation Calculation Method and Parameter Analysis for Loose Continuous-Tenon Joint in Column-And-Tie Timber Structure

ABSTRACT To quantitatively calculate the moment-rotation relationship of loose continuous-tenon joints in traditional column-and-tie timber frame, the rotational deformation of loose joints is divided into two stages: free sliding and contact compression. Using constitutive, geometric, and equilibrium equations, a theoretical formula for moment-rotation is derived. The calculated values are then compared with experimental results to validate the accuracy of the theoretical calculation method. A sensitivity analysis is conducted on typical parameters, such as beam height, column diameter, joint clearance, and perpendicular compression modulus of wood, to explore their effects on the moment-rotation relationship of tenon joints. The results show that increasing the perpendicular compression modulus of wood leads to greater bending stiffness and load carrying capacity of tenon joints, with the latter increasing more significantly. In the elastic stage, the rotational stiffness of the joint increases with beam height or column diameter, while after entering the elastoplastic stage, the joint stiffness is less influenced by these factors. The initial rotational stiffness and load carrying capacity of the joint both decrease with joint clearance, and the effect of joint clearance on load carrying capacity decreases as the clearance increases when the joint enters the yielding stage.

A theoretical calculation method of seismic shear key pounding based on continuum model

The evolution of shear key design for bridges is accompanied by research on structural earthquake resistance. However, the vast majority of pounding forces, responses, and corresponding data for the study and design of shear keys have been based on expensive experimentalism and imprecise empiricism approaches for decades. Hence, strengthening theoretical study on seismic performance of shear key is essential. In this paper, a “Beam-Spring-Beam + Concentrated Mass” continuum dynamic model is proposed. Meanwhile, the transient wave function expansion method and the mode superposition method are applied to determine the analytical expression of the dynamic response from the girder and pier system (pier and cap beam). Furthermore, the combined transient internal force method and Duhamel integration method are introduced to assess the elastic pounding process. Through programming and numerical analysis, a series of pounding response data related to the shear key under various working circumstances will be explored. As mentioned above, the proposed theoretical method can optimize shear key design and boost the reliability of seismic limiting devices in the future.•Establishing a feasible “Beam-Spring-Beam + Concentrated Mass” continuum model of girders and piers based on a two-span continuous girder bridge.•Deriving the analytical solutions of responses by conducting the response equations under horizontal seismic excitation (containing orthonormality verification).•Simulating the pounding process by embedding elastic pounding calculation methods into Continuum Model.

The effect of water molecules and air humidity on the cluster formation from benzoic acid with sulfuric acid/ammonia/dimethylamine: A molecular-scale investigation

In the atmosphere, benzoic acid (BA) is one of the most abundant aromatic acids and contributes to new particle formation (NPF). Sulfuric acid (SA), ammonia (NH3), and dimethylamine (DMA) have been identified as critical nucleation precursors. Since water (H2O) is abundant in the atmosphere, the hydration effect is a significant concern. However, the hydration effect on the precise mechanisms of cluster formation remains unclear. In this study, theoretical calculation method was used to investigate the interactions between BA and NH3/DMA/SA in the presence of up to six water molecules at the PW91PW91/6-311++G(3df,3pd) using geometrical analysis, topological analysis, and the Gibbs free energies analysis. Hydrated distributions of clusters under different relative humidity (RH) levels and their atmospheric implications were also estimated. This study shows water molecules have mild impacts on the interaction between BA and NH3/DMA, but have relatively strong effect on the interaction between BA and SA. Hydrated distributions for the three types of clusters show that they are insensitive to different RH levels, and a completely unhydrated (BA)(NH3) cluster dominates the hydrated distributions. When the concentrations of BA are particularly high, especially in heavily polluted areas, the concentrations of (BA)(SA) can reach the same order of magnitude or higher than those of (SA)2. Thus, the importance of BA in prompting NPF has been revealed to a certain extent.

Study of the tensile properties of the original bamboo sleeve grouting joints

As an environmentally friendly and renewable green building material, bamboo has an increasingly broad application prospect under the requirement of promoting low-carbon sustainable development. However, due to the natural properties of hollow, thin-wall and anisotropy of raw bamboo material, the study of raw bamboo joints has been a challenge in the development of raw bamboo structures. This manuscript presents a novel bamboo sleeve grouting connection. 13 connection specimens were fabricated to conduct axial tensile tests and establish a finite element simulation. The experimental and finite element results indicate that increasing the number of bolts, bonding depth, and dimensions of the bamboo tube section can improve the tensile bearing capacity of the connection. Among them, the increase in the number of bolts has the most obvious effect on the connection lifting, which can increase the ultimate bearing capacity by up to 322.19%. Ultimately, theoretical calculation methods for the connections were proposed based on the principles of elastic-plastic mechanics and rigid-plastic mechanics, respectively. These theoretical calculation methods exhibit an elastic-plastic verification coefficient ranging from 0.80 to 1.09 and a rigid-plastic verification coefficient ranging from 0.88 to 1.17. With relatively high precision in accordance with experimental and simulation outcomes, these theoretical calculation methods furnish a solid theoretical foundation for the design methodology of the connections in bamboo sleeve grouting.

Numerical and theoretical studies for the shear behavior of CFRP plate-ECC-concrete composite interface

The shear behavior of the single-shear specimen with CFRP plate-ECC-concrete (CEC) composite interface was investigated using the finite element (FE) and theoretical calculation methods. The proposed FE model was established to simulate the entire loading process of the single-shear specimen under actual experimental conditions, and the newly developed CFRP-ECC interface model was incorporated. The FE model was calibrated and verified by comparing it with the experimental results. The results showed good agreement between the simulated and measured values for debonding load, shear stress, and interface damage. The proposed FE model was further adopted to perform parameter analyses of ECC thickness, CFRP bonding length, and CFRP plate width. This paper also proposed a calculation model for the debonding load of CEC composite interface considering the high tensile strength and the thickness of ECC. The results show that the proposed model shows a high accuracy for the prediction of debonding load.

Revealing the influence of solute segregation on the stability and strength of Cu Σ11 [110](113) symmetrical tilt grain boundary via first-principles investigation

The stability and strength of the grain boundary (GB) structure are critical for the practical application of nanocrystals. This study systematically calculates the impact of the segregation of 26 transitional alloy elements on Cu Σ11 [110](113) GB using the first-principle theoretical calculation method. The research findings demonstrate that there is a parabolic connection between atomic number and segregation energy of TM elements in the same period. In addition to Fe, Co, and Ni, all other 23 elements have the potential to segregate to Cu GB, with Zr exhibiting the strongest segregation tendency. The difference in atomic radius and electronegativity between solute atoms and copper atoms strongly affects the segregation tendency, the greater the difference, the greater the tendency for segregation. The segregation energy of solute segregation has strong linear correlation with its GB energy, and the stronger the segregation ability, the more stable the GB. Except for Zn, Ag, Cd, and Au, other 19 alloying elements can increase the strength of GB. Electronic analysis indicates that the strengthening and embrittlement of solutes are primarily related to the accumulation and consumption of electrons near GB and the bonding between atoms.

Experimental vs. Theoretical Viscosity Determination of Aluminosilicate Glasses.

The paper presents the results of studies on the viscosity of the glass mass in various temperature ranges, determining the basic technological parameter, very important from the point of view of melting and forming. For this purpose, six sets based on natural raw materials such as basalt, dolomite, and amphibolite, modified with different amounts of float glass cullet, were melted. The melting process was carried out in an electric furnace at the temperature of 1450 °C for 2 h. Using the dilatometric method, high-temperature microscopy and theoretical calculation methods, the viscosity of the produced glasses was determined in various temperature ranges. Comparative analyses of the employed methods were carried out. The significance of the applied calculation methods for aluminosilicate glasses depending on the basic chemical composition of the glasses was presented. The relationship between the manner of incorporating amphoteric ions Al3+, Fe3+ and Mg2+ into the glass structure and the change in viscosity in the temperature range corresponding to the working point range at 104 [dPa·s] viscosity and the relaxation range-Tg temperature at 1013 [dPa·s] viscosity was justified. It was justified that in order to plot the viscosity curve with the correct slope in the forming range for aluminosilicate glasses, it is appropriate to use the two-point method based on the fixed viscosity points of 104 [dPa·s] and 1013 [dPa·s].

A new method for calculating the minimum sand-carrying velocity in geothermal well production

Formation sand production is an important engineering and technical problem that restricts the safe and efficient development of geothermal wells. Accurate prediction of the minimum sand carrying velocity of sand production is the key to effectively controlling the formation sand production of geothermal wells. Compared with conventional vertical well sand production, geothermal wellbore sand carrying has the characteristics of high concentration, high fluid temperature, and easy silting, which makes it more difficult to calculate the minimum sand carrying velocity. In order to derive the formula of sand carrying law suitable for complex geothermal conditions, this paper considers the temperature and concentration conditions, based on the basic sedimentation principle and indoor sand carrying experiment, abandons the single correction coefficient correction of the conventional calculation formula, integrates the influence of temperature and high sand content on debris migration and deposition, and adopts the double correction coefficient of temperature-viscosity and sand content-mixed density, the actual minimum sand carrying velocity calculation formula of geothermal well under different sand content and temperature is obtained, and a new theoretical calculation method of minimum sand carrying velocity of the geothermal wellbore is formed. With the help of indoor experiments, a reasonable experimental group was designed to carry sand law experimental research. The experimental results show that the calculated value is in good agreement with the measured data, and can be used to calculate the minimum sand-carrying velocity of unconsolidated sandstone in the geothermal wellbore, which provides a basis for sand-carrying failure and sand sinking prevention in geothermal wellbore site.

Composition optimization and performance prediction for ultra-stable water-based aerosol based on thermodynamic entropy theory

Water-based aerosol is widely used as an effective strategy in electro-optical countermeasure on the battlefield used to the preponderance of high efficiency, low cost and eco-friendly. Unfortunately, the stability of the water-based aerosol is always unsatisfactory due to the rapid evaporation and sedimentation of the aerosol droplets. Great efforts have been devoted to improve the stability of water-based aerosol by using additives with different composition and proportion. However, the lack of the criterion and principle for screening the effective additives results in excessive experimental time consumption and cost. And the stabilization time of the aerosol is still only 30 min, which could not meet the requirements of the perdurable interference. Herein, to improve the stability of water-based aerosol and optimize the complex formulation efficiently, a theoretical calculation method based on thermodynamic entropy theory is proposed. All the factors that influence the shielding effect, including polyol, stabilizer, propellant, water and cosolvent, are considered within calculation. An ultra-stable water-based aerosol with long duration over 120 min is obtained with the optimal fogging agent composition, providing enough time for fighting the electro-optic weapon. Theoretical design guideline for choosing the additives with high phase transition temperature and low phase transition enthalpy is also proposed, which greatly improves the total entropy change and reduce the absolute entropy change of the aerosol cooling process, and gives rise to an enhanced stability of the water-based aerosol. The theoretical calculation methodology contributes to an abstemious time and space for sieving the water-based aerosol with desirable performance and stability, and provides the powerful guarantee to the homeland security.

Low‐Energy Driven Ring‐Opening Behavior of Benzocyclobutene Derivatives

Comprehensive SummaryIt's urgent to develop benzocyclobutene (BCB)‐based polymers with low curing temperature for temperature‐sensitive applications such as liquid crystal displays (LCDs) and flexible electronics. Herein, the effect of substituents on the ring‐opening behavior of BCB derivatives was investigated. The ring‐opening activation energy barriers (ΔGA) of BCB derivatives with one or two substituents on the four‐membered alkyl ring were systematically calculated using the B3LYP function. Both mono‐ and di‐substituted BCBs adopted the conrotatory ring‐opening process, obeying the Woodward‐Hoffmann's Rules upon heating. The mono‐/di‐substituted BCBs exhibited 8.2%—69% lower ΔGA compared with BCB, attributed to the electronic effects of the substituents. Disubstituted BCBs with both electron‐donating and electron‐withdrawing groups, e.g., 1‐NH2‐8‐NO2‐BCB, demonstrated the lowest ΔGA. In addition, BCB derivatives with amide/ester/acyloxy group modified on C1 position were synthesized as model molecules, and their ring‐opening temperature can be decreased by 20 °C compared to the unsubstituted one, also consistent with our calculation results. This work combined theoretical calculation methods with experimental results to provide valuable insights into the design and synthesis of BCB derivatives and next‐generation BCB functional packaging materials with low ring‐opening temperature.

Experimental and theoretical investigation for shielding efficiency of self-compacted concrete containing lead smelting waste for gamma ray

Lead smelter waste is considered as one of the most hazardous waste that pollute the environment by releasing hazardous effluents, a lot of particle matter, and other different solid wastes. In this research lead smelter waste is used as a concrete additive and fine aggregate constituent in self-compacted concrete casting to be used as a gamma ray shield. Three types of traditionally used coarse aggregate (basalt, crushed dolomite, and gravel) were used in casting normal and high strength self-compacted concrete. The fresh and hardened concrete properties were investigated. The cast samples were tested for 137Cs and 60Co gamma rays with energies 0.662 and 1.25 Mev. The mass attenuation coefficients (µ/ρ) and linear attenuation (µ) were measured and calculated using WinXCom program for gamma rays. The experimental measurements and the used theoretical calculation method were highly compatible. The usage of lead smelter waste in concrete casting improved the concrete gamma rays shielding.