The effects of pressure on the structural stability,elasticity,electronic properties,and thermodynamic properties of Al,Al_(3)Cu,Al_(2)Cu,Al_(4)Cu_(9),AlCu_(3),and Cu were investigated using first-principles calculati...The effects of pressure on the structural stability,elasticity,electronic properties,and thermodynamic properties of Al,Al_(3)Cu,Al_(2)Cu,Al_(4)Cu_(9),AlCu_(3),and Cu were investigated using first-principles calculations.The experimental results indicate that the calculated equilibrium lattice constant,elastic constant,and elastic modulus agree with both theoretical and experimental data at 0 GPa.The Young's modulus,bulk modulus,and shear modulus increase with increasing pressure.The influence of pressure on mechanical properties is explained from a chemical bond perspective.By employing the quasi-harmonic approximation model of phonon calculation,the temperature and pressure dependence of thermodynamic parameters in the range of 0 to 800 K and 0 to 100 GPa are determined.The findings demonstrate that the thermal capacity and coefficient of thermal expansion increase with increasing temperature and decrease with increasing pressure.This study provides fundamental data and support for experimental investigations and further theoretical research on the properties of aluminum-copper intermetallic compounds.展开更多
Control of hyperfine interaction strength of shallow donors in Si is one of the central issues in realizing Kane quantum computers.First-principles calculations on the hyperfine Stark shift of shallow donors are chall...Control of hyperfine interaction strength of shallow donors in Si is one of the central issues in realizing Kane quantum computers.First-principles calculations on the hyperfine Stark shift of shallow donors are challenging since large supercells are needed to accommodate the delocalized donor wave functions.In this work,we investigated the hyperfine Stark shift and its strain tunability for shallow donors P and As in Si using the potential patching method based on first-principles density functional theory calculations.The good agreement between our calculations and experimental results confirms that the potential patching method is a feasible and accurate first-principles approach for studying wave-function-related properties of shallow impurities,such as the Stark shift parameter.It is further shown that the application of strain expands the range of hyperfine Stark shift and helps improve the response of shallow donor based qubit gates.The results could be useful for developing quantum computing architectures based on shallow donors in Si.展开更多
In this study,6061 aluminum alloy and galvanized steel fusion-brazed lap joints were obtained using a laser-arc hybrid heat source,and the effects of laser power variation on the microstructure,mechanical properties,a...In this study,6061 aluminum alloy and galvanized steel fusion-brazed lap joints were obtained using a laser-arc hybrid heat source,and the effects of laser power variation on the microstructure,mechanical properties,and fracture mechanism of the joints were ana-lyzed.The results showed that the tensile shear load initially increased with rising laser power,followed by a decrease.At a laser power of 240 W,the maximum tensile shear load was 2479.8 N/cm and the weak section of joint was in the Al-Fe reaction layer con-sisting of Fe(Al,Si)_(3),Fe_(2)(Al,Si)_(5),and Fe(Al,Si)intermetallic compounds(IMCs).Computational results showed that the inherently high brittleness and hardness of Fe(Al,Si)_(3) and the high mismatch rates of Fe(Al,Si)_(3)/Al interfaces were the key factor leading to the failure of the joints at lower heat input.展开更多
To explain the influence mechanism of MgO on the consolidation and reduction characteristics of roasted iron pellets,the properties and structure of pellets were investigated from multi-dimensions.It indicated that th...To explain the influence mechanism of MgO on the consolidation and reduction characteristics of roasted iron pellets,the properties and structure of pellets were investigated from multi-dimensions.It indicated that the MgO addition decreased the reduction swelling index(RSI)and reduction degree of pellets in both CO and H_(2)atmospheres.During the stepwise reduction process of Fe2O3→Fe3O4→FeO,the reduction behaviour of pellets in CO and H_(2)was similar,while the reduction rate of pellets in H_(2)atmosphere was almost twice as high as that in CO atmosphere.During the stepwise reduction process of FeO→Fe,the RSI of pellets showed a logarithmic increase in CO atmosphere and a linear decrease in H_(2)atmosphere.As investigated by first-principles calculations,C and Fe mainly formed chemical bonds,and the CO reduction process released energy,promoting the formation of iron whiskers.However,H and Fe produced weak physical adsorption,and the H_(2)reduction process was endothermic,inhibiting the generation of iron whiskers.With Mg2+doping in FexO,the nucleation region of iron whiskers expanded in CO reduction process,and the morphology of iron whiskers transformed from“slender”to“stocky,”reducing RSI of the pellets.展开更多
We have investigated the phase stability,magnetic properties,and martensitic transformation thermodynamics/kinetics of the Ni_(24-x)Mn_(18+x+y)Sn_(6-y)(x,y=0,1,2)system by combining the first-principles calculations a...We have investigated the phase stability,magnetic properties,and martensitic transformation thermodynamics/kinetics of the Ni_(24-x)Mn_(18+x+y)Sn_(6-y)(x,y=0,1,2)system by combining the first-principles calculations and experiments.The calculation results show that the optimized lattice parameters are consistent with the experimental data.Respectively,we obtain the relation equation for the austenite formation energy(E_(form-A))and Mn content(X_(Mn)):E_(form-A)=507.358X_(Mn)-274.126,as well as for the six-layer modulated(6M)martensite formation energy(E_(form-6M))and Ni content(X_(Ni)):E_(form-6M)=-728.484X_(Ni)+264.374.The ternary phase diagram of the total magnetic moment was established.The excess Mn will reduce the total magnetic moment of 6M(Mag6M)and non-modulated(NM)(MagNM)martensites,with the following equations relating the total magnetic moment and Mn content:Mag_(6M)=-15.905X_(Mn)+7.902and Mag_(NM)=-14.781X_(Mn)+7.411,while the effect on austenite is complex.The variation of total magnetic moment is mainly dominated by the Mn atomic magnetic moment.The 3d electrons of Mn_(Sn)(Mn at Sn sublattice)play an important role in magnetic properties from the perspective of the electronic density of states.Based on the thermodynamics of martensitic transformation,the alloys will likely undergo austenite?6M?NM transformation sequence.Combining the thermodynamic and kinetic results,the martensitic transformation temperature decreases with x increasing and increases with y increasing.These results are expected to provide reference for predicting the phase stability and magnetic properties of NiMn-Sn alloys.展开更多
As cataract surgery progresses from “restoration of sight” to “refractive correction”, precise prediction of intraocular lens (IOL) power is critical for enhancing postoperative visual quality in patients. IOL pow...As cataract surgery progresses from “restoration of sight” to “refractive correction”, precise prediction of intraocular lens (IOL) power is critical for enhancing postoperative visual quality in patients. IOL power calculation methods have evolved and innovated throughout time, from early theoretical and regression formulas to nonlinear formulas for estimating effective lens position (ELP), multivariable formulas, and innovative formulas that use optical principles and AI-based online formulas. This paper thoroughly discusses the development and iteration of traditional IOL calculation formulas, the emergence of new IOL calculation formulas, and the selection of IOL calculation formulas for different patients in the era of refractive cataract surgery, serving as a reference for “personalized” IOL implantation in clinical practice.展开更多
Based on experiments and first-principles calculations,the microstructures and mechanical properties of as-cast and solution treated Mg-10Gd-4Y-xZn-0.6Zr(x=0,1,2,wt.%)alloys are investigated.The transformation process...Based on experiments and first-principles calculations,the microstructures and mechanical properties of as-cast and solution treated Mg-10Gd-4Y-xZn-0.6Zr(x=0,1,2,wt.%)alloys are investigated.The transformation process of long-period stacking ordered(LPSO)structure during solidification and heat treatment and its effect on the mechanical properties of experimental alloys are discussed.Results reveal that the stacking faults and 18R LPSO phases appear in the as-cast Mg-10Gd-4Y-1Zn-0.6Zr and Mg-10Gd-4Y-2Zn-0.6Zr alloys,respectively.After solution treatment,the stacking faults and 18R LPSO phase transform into 14H LPSO phase.The Enthalpies of formation and reaction energy of 14H and 18R LPSO are calculated based on first-principles.Results show that the alloying ability of 18R is stronger than that of 14H.The reaction energies show that the 14H LPSO phase is more stable than the 18R LPSO.The elastic properties of the 14H and 18R LPSO phases are also evaluated by first-principles calculations,and the results are in good agreement with the experimental results.The precipitation of LPSO phase improves the tensile strength,yield strength and elongation of the alloy.After solution treatment,the Mg-10Gd-4Y-2Zn-0.6Zr alloy has the best mechanical properties,and its ultimate tensile strength and yield strength are 278.7 MPa and 196.4 MPa,respectively.The elongation of Mg-10Gd-4Y-2Zn-0.6Zr reaches 15.1,which is higher than that of Mg-10Gd-4Y0.6Zr alloy.The improving mechanism of elastic modulus by the LPSO phases and the influence on the alloy mechanical properties are also analyzed.展开更多
In the present work,a new Mg-Bi based alloy is developed by the addition of Zn and Ca in equiva-lent atom fraction with Bi.Mg-Bi and Mg-Bi-Zn-Ca alloys were prepared by extrusion at a ram speed of 20 mm/s.Room tempera...In the present work,a new Mg-Bi based alloy is developed by the addition of Zn and Ca in equiva-lent atom fraction with Bi.Mg-Bi and Mg-Bi-Zn-Ca alloys were prepared by extrusion at a ram speed of 20 mm/s.Room temperature mechanical properties and creep behaviors at 423 K were investigated.The results show that Zn and Ca co-addition shows little influence on average grain size and texture in-tensity but changes the dispersive Mg_(3)Bi_(2)into Mg_(2)Bi_(2)Ca particles in different sizes and a lower density.Twinning is largely activated during room-temperature deformation.Consequently,a slightly decreased proof strength but tripled elongation is shown at room temperature.Unexpectedly,large enhancement in creep resistance is detected after the co-alloying of Zn and Ca and the minimum creep rate is reduced by 10 to 20 times in the BZX621 alloy.Stress exponent n=4-5 indicates that the creep is a dislocation-climb controlled type.Post-mortem characterization on microstructure shows slip of dislocationc+aare also largely found in B6 as well as BZX621 alloy and cross-slip is detected more severe in B6 alloy.Dynamic segregation and precipitation are also seen in both alloys.Bi-clusters are seen dispersive across the grains in B6 and so did the PFZs that could undermine creep resistance at the grain boundaries.By contrast,Zn-rich needle-like precipitates are developed at most“ends”ofc+adislocations,which would hinder the further dislocation motions and thus improve the creep resistance.First-principles cal-culations were adopted and the results show that the thermal stability and thermomechanical properties of Mg_(2)Bi_(2)Ca are much better than that of Mg_(3)Bi_(2).Stacking faults energy is lowered down with the co-addition of Ca and Zn,which could inhibit the rate of dislocation climb and cross-slip.As a result,the im-proved creep resistance is obtained in the Mg-Bi-Zn-Ca alloys.Microstructural and controlling mechanism changes by thermal activation result in the unexpected enhancement in creep resistance with decreased room-temperature proof strength after co-addition.These findings could contribute to the development and optimization of creep-resistant Mg alloys in the future.展开更多
Steel-concrete composite beams,due to their superior mechanical properties,are widely utilized in engineering structures.This study systematically investigates the calculation methods for internal forces and load-bear...Steel-concrete composite beams,due to their superior mechanical properties,are widely utilized in engineering structures.This study systematically investigates the calculation methods for internal forces and load-bearing capacity of composite beams based on elastic theory,with a focus on the transformed section method and its application under varying neutral axis positions.By deriving the geometric characteristics of the transformed section and incorporating a reduction factor accounting for slip effects,a computational model for sectional stress and ultimate load-bearing capacity is established.The results demonstrate that the slip effect significantly influences the flexural load-bearing capacity of composite beams.The proposed reduction factor,which considers the influence of the steel beam’s top flange thickness,offers higher accuracy compared to traditional methods.These findings provide a theoretical foundation for the design and analysis of composite beams,with significant practical engineering value.展开更多
Understanding the adsorption behavior of heavy metals and metalloids on clay minerals is essential for remediating heavy metal-contaminated soils.The adsorption of heavy metals and metalloids on illite(001)and sodium ...Understanding the adsorption behavior of heavy metals and metalloids on clay minerals is essential for remediating heavy metal-contaminated soils.The adsorption of heavy metals and metalloids on illite(001)and sodium montmorillonite(Na-MMT)(001)surfaces was investigated using first-principles calculations in this study,especially As atom and H_(3)AsO_(3) molecule.The adsorption energies of the As atom were−1.94 eV on the illite(001)and−0.56 eV on the Na-MMT(001),whereas,the adsorption energies of the H_(3)AsO_(3) molecule were−1.40 eV on illite(001)and−1.01 eV on Na-MMT(001).The above results indicate that the adsorption was more energetically favorable on illite(001).Additionally,compared to Na-MMT(001),there were more significant interactions between the atoms/molecules on the illite(001).After As atom and H_(3)AsO_(3) molecule adsorption,the electrons were transferred from mineral surface atoms to the adsorbates on both illite(001)and Na-MMT(001)surfaces.Moreover,the adsorption of As atom on illite(001)and Na-MMT(001)surfaces were more energy favorable compared to Hg,Cd,and Cr atoms.Overall,this work provides new insights into the adsorption behavior of As atoms and As molecules on illite and Na-MMT.The results indicate that illite rich soils are more prone to contamination by arsenic compared to soils primarily composed of Na-MMT minerals.展开更多
The longitudinal cracks distributed along the dam axis in the corridor of a dam may have potential safety hazards.According to the detection results of crack depth and width and the analysis of monitoring data,a three...The longitudinal cracks distributed along the dam axis in the corridor of a dam may have potential safety hazards.According to the detection results of crack depth and width and the analysis of monitoring data,a three-dimensional finite element model is established for numerical simulation calculation and the influence of cracks on the safety of dam structure is analyzed from different aspects such as deformation,stress value,and distribution range.The calculation results show that the maximum principal tensile stress value and the location of the dam body are basically independent of the change of crack depth(within 1.0 m).Regarding local stress around the corridor,the high upstream water level causes cracks to deepen,resulting in an increase in the maximum tensile stress near the crack tip and an expansion of the tensile stress region.展开更多
AIM:To investigate the effect of pharmacological pupil alterations on intraocular lens(IOL)power calculations.METHODS:A systematic review and Meta-analysis of studies published before December 2023 in the PubMed,Embas...AIM:To investigate the effect of pharmacological pupil alterations on intraocular lens(IOL)power calculations.METHODS:A systematic review and Meta-analysis of studies published before December 2023 in the PubMed,Embase,and Cochrane library databases on the accuracy of pharmacological pupil changes on IOL power calculation was performed.The primary outcome was the results of IOL power calculations before and after the use of medications.Subgroup analyses were performed based on participants’basic characteristics,such as age,axial length(AL),and whether miosis or mydriasis were used as classification criteria for further analyses.Each eligible study was evaluated for potential risk of bias by the AHRQ assessment scale.The study was registered on PROSPERO(CRD 42024497535).RESULTS:A total of 3062 eyes from 21 studies were eligible.There was no significant difference in the IOL power calculation before and after pharmacological pupil changes using any of the Hoffer Q(WMD=0.055,95%CI=-0.046–0.156;P=0.29),SRK/T(WMD=0.003,95%CI=-0.073–0.080;P=0.93),Haigis(WMD=-0.030,95%CI=-0.176–0.116;P=0.69),Holladay 2(WMD=-0.042,95%CI=-0.366–0.282;P=0.80),and Barrett Universal Ⅱ(WMD=0.033,95%CI=-0.061–0.127;P=0.49)formulas.On the measurement of parameters related to IOL power calculation,for either miosis or mydriasis AL(P=0.98 and 0.29,respectively),lens thickness(P=0.96 and 0.13,respectively),and mean keratometry(P=0.90 and 0.86,respectively)did not present significant differences,while anterior chamber depth(P=0.07 and<0.01,respectively)and white-to-white distance(P=0.01 and 0.04,respectively)changed significantly between the two measurements prior and posterior.At the same time,despite there being some participants with the difference between the before and after calculations greater than 0.5 diopter,there was no significant difference in the incidence rate between these formulas.CONCLUSION:There is no significant effect of pharmacological pupil changes on the IOL power calculation.It will considerably reduce the visit time burden for patients who require cataract surgery.展开更多
The micro-area characterization experiments like scanning Kelvin probe force microscope(SKPFM)and Kernel average misorientation have the defects of complex sample preparation and occasional errors in test results,whic...The micro-area characterization experiments like scanning Kelvin probe force microscope(SKPFM)and Kernel average misorientation have the defects of complex sample preparation and occasional errors in test results,which makes it impossible to accurately and quickly analyze the pitting behavior induced by inclusions in some cases,prompting attempts to turn to simulation calculation research.The method of calculating band structure and work function can be used to replace current-sensing atomic force microscopy and SKPFM to detect the potential and conductivity of the sample.The band structure results show that Al_(2)O_(3) inclusion is an insulator and non-conductive,and it will not form galvanic corrosion with the matrix.Al_(2)O_(3) inclusion does not dissolve because its work function is higher than that of the matrix.Moreover,the stress concentration of the matrix around the inclusion can be characterized by first-principles calculation coupled with finite element simulation.The results show that the stress concentration degree of the matrix around Al_(2)O_(3) inclusion is serious,and the galvanic corrosion is formed between the high and the low stress concentration areas,which can be used to explain the reason of the pitting induced by Al_(2)O_(3) inclusions.展开更多
Two pairs of novel 6/6/6/9 tetracyclic merosesquiterpenoid enantiomers,dauroxonanols A(1)and B(2),possessing an unprecedented 9,15-dioxatetracyclo[8.5.3.0^(4.17).0^(14.18)]octadecane core skeleton,were isolated from R...Two pairs of novel 6/6/6/9 tetracyclic merosesquiterpenoid enantiomers,dauroxonanols A(1)and B(2),possessing an unprecedented 9,15-dioxatetracyclo[8.5.3.0^(4.17).0^(14.18)]octadecane core skeleton,were isolated from Rhododendron dauricum.The nuclear magnetic resonance(NMR)spectra of 1 and 2 showed very broad resonances,and^(13)C NMR spectrum of 1 exhibited only 13 instead of 22 carbon resonances.These broadening or missing NMR resonances led to a great challenge to elucidate their structures using NMR data analysis.Their structures and absolute configurations of 1 and 2 were finally determined by single crystal X-ray diffraction analysis,chiral separation,and electronic circular dichroism(ECD)calculations.Plausible biosynthetic pathways for 1 and 2 are proposed.Conformational analysis,density functional theory(DFT)calculations,and dynamic NMR assigned the coalescent NMR phenomena of 1 and 2 to the conformational changes of the flexible oxonane ring.Dauroxonanols A(1)and B(2)showed potentα-glucosidase inhibitory activities,2-8 times potent than acarbose,an antidiabetic drug targetingα-glucosidase in clinic.展开更多
Oxygen release from Ni-rich cathode is one of the major structural degradations resulting in rapid performance fading in lithium-ion batteries(LIBs).The energy gap between the transition metals(TM)-d band and the O-p ...Oxygen release from Ni-rich cathode is one of the major structural degradations resulting in rapid performance fading in lithium-ion batteries(LIBs).The energy gap between the transition metals(TM)-d band and the O-p band serves as an effective evaluation metric in characterizing the potential for oxygen release.Given that the primary oxidation factors of NCM811 materials vary at different states of charge(SOC),this study employs high-throughput density functional theory(DFT)calculations combined with machine learning(ML)to systematically investigate the regulation mechanism of heteroatoms on the energy gap between the TM-d band(TM=Ni,Co)and O-p band at various SOC levels.Highthroughput DFT calculations were used to study doping thermodynamic stability and complete the database.The results indicate that dopant atoms remain at their original sites even at 50%SOC.Correlation analysis reveals that at 0 SOC,the dopant reduces Ni-O bonding interactions by forming its own bonds with oxygen,thereby preventing lattice oxygen escape and weakening the oxygen binding of the system during Ni redox.At 50%SOC,the dopant and Co atoms synergistically strengthen their bonding interactions with oxygen,thereby maintaining structural stability and inhibiting lattice oxygen escape.Based on R^(2)and root-mean-square error(RMSE),the gradient boosting regression(GBR)algorithm is identified as optimal for predicting the energy gaps between the Ni-d band and O-p band,as well as between the Co-d band and O-p band.Feature importance analysis demonstrates that the magnetic moment(Dma)of the doped atom significantly contributes to the prediction of ΔNi-O and ΔCo-O.In this study,the energy gap regulation mechanisms of Ni-d/O-p and Co-d/O-p are systematically investigated using non-empirical first principle calculations combined with data-driven machine learning,aiming to provide insights into the electrochemical stability of NCM811 and related materials.展开更多
By comprehensively considering the influences of temperature and pressure on fluid density in high temperature and high pressure(HTHP)wells in deepwater fractured formations and the effects of formation fracture defor...By comprehensively considering the influences of temperature and pressure on fluid density in high temperature and high pressure(HTHP)wells in deepwater fractured formations and the effects of formation fracture deformation on well shut-in afterflow,this study couples the shut-in temperature field model,fracture deformation model,and gas flow model to establish a wellbore pressure calculation model incorporating thermo-hydro-mechanical coupling effects.The research analyzes the governing patterns of geothermal gradient,bottomhole pressure difference,drilling fluid pit gain,and kick index on casing head pressure,and establishes a shut-in pressure determination chart for HPHT wells based on coupled model calculation results.The study results show:geothermal gradient,bottomhole pressure difference,and drilling fluid pit gain exhibit positive correlations with casing head pressure;higher kick indices accelerate pressure rising rates while maintaining a constant maximum casing pressure;validation against field case data demonstrates over 95%accuracy in predicting wellbore pressure recovery after shut-in,with the pressure determination chart achieving 97.2%accuracy in target casing head pressure prediction and 98.3%accuracy in target shut-in time.This method enables accurate acquisition of formation pressure after HPHT well shut-in,providing reliable technical support for subsequent well control measures and ensuring safe and efficient development of deepwater and deep hydrocarbon reservoirs.展开更多
This study investigates the application of Gurney and flight of fragment equations,typically used to predict metal fragment velocities,in modeling the water jet behavior.Three shotgun cartridge sizes were used as the ...This study investigates the application of Gurney and flight of fragment equations,typically used to predict metal fragment velocities,in modeling the water jet behavior.Three shotgun cartridge sizes were used as the energy source:2.59 g,5.83 g,and 7.13 g.Two configurations were tested:standard(full-barrel water load)and"negative 8"(partial water load).High-speed footage captured water column velocities,and Gurney models,including infinitely tamped and open-faced configurations,combined with the flight of fragment model were used to assess prediction accuracy.Results showed charge strength significantly affects water column velocity,with higher strengths yielding greater stability and velocity retention over distance.The infinitely tamped Gurney model closely predicted experimental velocities,deviating by as little as 1.4%for standard charges and 2.8% for negative 8 charges.Additionally,interesting dynamics such as a 1-2°rise in jet height and the rear overtaking the front was observed.These findings have significant implications for optimizing PAN disruptors and enhancing performance in high-velocity fluid applications and explosive breaching systems.展开更多
AIM:To evaluate the accuracy of intraocular lens(IOL)power calculation formulas with/without preoperative aphakic anterior chamber depth(aph-ACD)in pediatric aphakia.METHODS:A total of 102 pediatric patients(150 eyes)...AIM:To evaluate the accuracy of intraocular lens(IOL)power calculation formulas with/without preoperative aphakic anterior chamber depth(aph-ACD)in pediatric aphakia.METHODS:A total of 102 pediatric patients(150 eyes)undergoing secondary IOL implantation were divided into two groups(in-the-bag or ciliary sulcus).Prediction error was calculated for 9 IOL power calculation formulas,including:1)not requiring ACD:Hoffer Q,Holladay 1,SRK/T;2)usable without or with entering ACD:Barrett Universal II(BUII),Emmetropia Verifying Optical(EVO)2.0,and Ladas Artificial Intelligence Super(Ladas AI);3)requiring ACD:Haigis,Kane,and Pearl-DGS.Mean prediction error(ME),mean absolute error(MAE),median absolute error(MedAE)and the percentage of eyes within±0.25,±0.50,±0.75,and±1.00 D were calculated.RESULTS:For the BUII,EVO 2.0,and Ladas AI,with aph-ACD demonstrated a higher MedAE compared to without aph-ACD(BUII:1.27 vs 1.13 D,EVO 2.0:1.26 vs 1.06 D,Ladas AI:1.30 vs 1.10 D;all P<0.05).Formulas requiring ACD(Haigis,Kane,and Pearl-DGS)exhibited larger MedAE than those not requiring aph-ACD(Hoffer Q,Holladay 1,and SRK/T;P<0.05).In the capsular group,the percentage of eyes within±1.00 D ranged from 44.83%to 74.14%,and it was 19.57%to 32.61%in the sulcus group.CONCLUSION:The introduction of aph-ACD does not improve the accuracy of IOL calculation for pediatric aphakia,regardless of in-the-bag or sulcus IOL secondary implantation.The relationship between aph-ACD and effective lens position in pediatric aphakia warrants further study.展开更多
The deformation energy(Wd)of soil-like tectonic coal is crucial for investigating the mechanism of coal and gas outbursts.Tectonic coal has a significant nonlinear constitutive relationship,which makes traditional ela...The deformation energy(Wd)of soil-like tectonic coal is crucial for investigating the mechanism of coal and gas outbursts.Tectonic coal has a significant nonlinear constitutive relationship,which makes traditional elastic-based models for computing Wdunsuitable.Inspired by critical state soil mechanics,this study theoretically established a new calculation model of Wdsuitable for the coal with nonlinear deformation characteristics.In the new model,the relationship between energy and stress no longer follows the square law(observed in traditional linear elastic models)but exhibits a power function,with the theoretical value of the power exponent ranging between 1 and 2.Hydrostatic cyclic loading and unloading experiments were conducted on four groups of tectonic coal samples and one group of intact coal samples.The results indicated that the relationship between Wdand stress for both intact and tectonic coal follows a power law.The exponents for intact and tectonic coal are close to 2 and 1,respectively.The stress-strain curve of intact coal exhibits small deformation and linear characteristics,whereas the stress-strain curves of tectonic coal show large deformation and nonlinear characteristics.The study specifically investigates the role of coal viscosity in the cyclic loading/unloading process.The downward bending in the unloading curves can be attributed to the time-dependent characteristics of coal,particularly its viscoelastic behavior.Based on experimental statistics,the calculation model of Wdwas further simplified.The simplified model involves only one unknown parameter,which is the power exponent between Wdand stress.The measured Wdof the coal samples increases with the number of load cycles.This phenomenon is attributed to coal's viscoelastic deformation.Within the same stress,the Wdof tectonic coal is an order of magnitude greater than that of intact coal.The calculation model of Wdproposed in this paper provides a new tool for studying the energy principle of coal and gas outbursts.展开更多
Aimed at the demand of contingency return at any time during the near-moon phase in the manned lunar landing missions,a fast calculation method for three-impulse contingency return trajectories is proposed.Firstly,a t...Aimed at the demand of contingency return at any time during the near-moon phase in the manned lunar landing missions,a fast calculation method for three-impulse contingency return trajectories is proposed.Firstly,a three-impulse contingency return trajectory scheme is presented by combining the Lambert transfer and maneuver at the special point.Secondly,a calculation model of three-impulse contingency return trajectories is established.Then,fast calculation methods are proposed by adopting the high-order Taylor expansion of differential algebra in the twobody trajectory dynamics model and perturbed trajectory dynamics model.Finally,the performance of the proposed methods is verified by numerical simulation.The results indicate that the fast calculation method of two-body trajectory has higher calculation efficiency compared to the semi-analytical calculation method under a certain accuracy condition.Due to its high efficiency,the characteristics of the three-impulse contingency return trajectories under different contingency scenarios are further analyzed expeditiously.These findings can be used for the design of contingency return trajectories in future manned lunar landing missions.展开更多
基金Funded by the National Key R&D Program of China(No.2021YFB3802300)the Foundation of National Key Laboratory of Shock Wave and Detonation Physics(No.JCKYS2022212004)the National Natural Science Foundation of China(No.52171045),and the Joint Fund(No.8091B022108)。
文摘The effects of pressure on the structural stability,elasticity,electronic properties,and thermodynamic properties of Al,Al_(3)Cu,Al_(2)Cu,Al_(4)Cu_(9),AlCu_(3),and Cu were investigated using first-principles calculations.The experimental results indicate that the calculated equilibrium lattice constant,elastic constant,and elastic modulus agree with both theoretical and experimental data at 0 GPa.The Young's modulus,bulk modulus,and shear modulus increase with increasing pressure.The influence of pressure on mechanical properties is explained from a chemical bond perspective.By employing the quasi-harmonic approximation model of phonon calculation,the temperature and pressure dependence of thermodynamic parameters in the range of 0 to 800 K and 0 to 100 GPa are determined.The findings demonstrate that the thermal capacity and coefficient of thermal expansion increase with increasing temperature and decrease with increasing pressure.This study provides fundamental data and support for experimental investigations and further theoretical research on the properties of aluminum-copper intermetallic compounds.
基金supported by the National Natural Science Foun-dation of China(Grant Nos.12393831 and 12088101).
文摘Control of hyperfine interaction strength of shallow donors in Si is one of the central issues in realizing Kane quantum computers.First-principles calculations on the hyperfine Stark shift of shallow donors are challenging since large supercells are needed to accommodate the delocalized donor wave functions.In this work,we investigated the hyperfine Stark shift and its strain tunability for shallow donors P and As in Si using the potential patching method based on first-principles density functional theory calculations.The good agreement between our calculations and experimental results confirms that the potential patching method is a feasible and accurate first-principles approach for studying wave-function-related properties of shallow impurities,such as the Stark shift parameter.It is further shown that the application of strain expands the range of hyperfine Stark shift and helps improve the response of shallow donor based qubit gates.The results could be useful for developing quantum computing architectures based on shallow donors in Si.
基金supported by the National Key Research and Development Program of China(No.2022YFB4600900).
文摘In this study,6061 aluminum alloy and galvanized steel fusion-brazed lap joints were obtained using a laser-arc hybrid heat source,and the effects of laser power variation on the microstructure,mechanical properties,and fracture mechanism of the joints were ana-lyzed.The results showed that the tensile shear load initially increased with rising laser power,followed by a decrease.At a laser power of 240 W,the maximum tensile shear load was 2479.8 N/cm and the weak section of joint was in the Al-Fe reaction layer con-sisting of Fe(Al,Si)_(3),Fe_(2)(Al,Si)_(5),and Fe(Al,Si)intermetallic compounds(IMCs).Computational results showed that the inherently high brittleness and hardness of Fe(Al,Si)_(3) and the high mismatch rates of Fe(Al,Si)_(3)/Al interfaces were the key factor leading to the failure of the joints at lower heat input.
基金support from the National Natural Science Foundation of China(52174290).
文摘To explain the influence mechanism of MgO on the consolidation and reduction characteristics of roasted iron pellets,the properties and structure of pellets were investigated from multi-dimensions.It indicated that the MgO addition decreased the reduction swelling index(RSI)and reduction degree of pellets in both CO and H_(2)atmospheres.During the stepwise reduction process of Fe2O3→Fe3O4→FeO,the reduction behaviour of pellets in CO and H_(2)was similar,while the reduction rate of pellets in H_(2)atmosphere was almost twice as high as that in CO atmosphere.During the stepwise reduction process of FeO→Fe,the RSI of pellets showed a logarithmic increase in CO atmosphere and a linear decrease in H_(2)atmosphere.As investigated by first-principles calculations,C and Fe mainly formed chemical bonds,and the CO reduction process released energy,promoting the formation of iron whiskers.However,H and Fe produced weak physical adsorption,and the H_(2)reduction process was endothermic,inhibiting the generation of iron whiskers.With Mg2+doping in FexO,the nucleation region of iron whiskers expanded in CO reduction process,and the morphology of iron whiskers transformed from“slender”to“stocky,”reducing RSI of the pellets.
基金financially supported by the National Natural Science Foundation of China(No.51771044)the Natural Science Foundation of Hebei Province(No.E2019501061)+5 种基金the Performance Subsidy Fund for Key Laboratory of Dielectric and Electrolyte Functional Material Hebei(No.22567627H)the Fundamental Research Funds for the Central Universities(No.N2223025)2023 Hebei Provincial doctoral candidate Innovation Ability training funding project(CXZZBS2023165)the Programme of Introducing Talents of Discipline Innovation to Universities 2.0(No.BP0719037)the support of the Shanxi Supercomputing Center of China,the calculations for this work were performed on TianHe-2supported by the China Scholarship Council(CSC)。
文摘We have investigated the phase stability,magnetic properties,and martensitic transformation thermodynamics/kinetics of the Ni_(24-x)Mn_(18+x+y)Sn_(6-y)(x,y=0,1,2)system by combining the first-principles calculations and experiments.The calculation results show that the optimized lattice parameters are consistent with the experimental data.Respectively,we obtain the relation equation for the austenite formation energy(E_(form-A))and Mn content(X_(Mn)):E_(form-A)=507.358X_(Mn)-274.126,as well as for the six-layer modulated(6M)martensite formation energy(E_(form-6M))and Ni content(X_(Ni)):E_(form-6M)=-728.484X_(Ni)+264.374.The ternary phase diagram of the total magnetic moment was established.The excess Mn will reduce the total magnetic moment of 6M(Mag6M)and non-modulated(NM)(MagNM)martensites,with the following equations relating the total magnetic moment and Mn content:Mag_(6M)=-15.905X_(Mn)+7.902and Mag_(NM)=-14.781X_(Mn)+7.411,while the effect on austenite is complex.The variation of total magnetic moment is mainly dominated by the Mn atomic magnetic moment.The 3d electrons of Mn_(Sn)(Mn at Sn sublattice)play an important role in magnetic properties from the perspective of the electronic density of states.Based on the thermodynamics of martensitic transformation,the alloys will likely undergo austenite?6M?NM transformation sequence.Combining the thermodynamic and kinetic results,the martensitic transformation temperature decreases with x increasing and increases with y increasing.These results are expected to provide reference for predicting the phase stability and magnetic properties of NiMn-Sn alloys.
文摘As cataract surgery progresses from “restoration of sight” to “refractive correction”, precise prediction of intraocular lens (IOL) power is critical for enhancing postoperative visual quality in patients. IOL power calculation methods have evolved and innovated throughout time, from early theoretical and regression formulas to nonlinear formulas for estimating effective lens position (ELP), multivariable formulas, and innovative formulas that use optical principles and AI-based online formulas. This paper thoroughly discusses the development and iteration of traditional IOL calculation formulas, the emergence of new IOL calculation formulas, and the selection of IOL calculation formulas for different patients in the era of refractive cataract surgery, serving as a reference for “personalized” IOL implantation in clinical practice.
基金supported by the National Key Research and Development Program of China[grant No.2018YFB2001800]National Natural Science Foundation of China[grant No.51871184]Dalian High-level Talents Innovation Support Program[grant No.2021RD06]。
文摘Based on experiments and first-principles calculations,the microstructures and mechanical properties of as-cast and solution treated Mg-10Gd-4Y-xZn-0.6Zr(x=0,1,2,wt.%)alloys are investigated.The transformation process of long-period stacking ordered(LPSO)structure during solidification and heat treatment and its effect on the mechanical properties of experimental alloys are discussed.Results reveal that the stacking faults and 18R LPSO phases appear in the as-cast Mg-10Gd-4Y-1Zn-0.6Zr and Mg-10Gd-4Y-2Zn-0.6Zr alloys,respectively.After solution treatment,the stacking faults and 18R LPSO phase transform into 14H LPSO phase.The Enthalpies of formation and reaction energy of 14H and 18R LPSO are calculated based on first-principles.Results show that the alloying ability of 18R is stronger than that of 14H.The reaction energies show that the 14H LPSO phase is more stable than the 18R LPSO.The elastic properties of the 14H and 18R LPSO phases are also evaluated by first-principles calculations,and the results are in good agreement with the experimental results.The precipitation of LPSO phase improves the tensile strength,yield strength and elongation of the alloy.After solution treatment,the Mg-10Gd-4Y-2Zn-0.6Zr alloy has the best mechanical properties,and its ultimate tensile strength and yield strength are 278.7 MPa and 196.4 MPa,respectively.The elongation of Mg-10Gd-4Y-2Zn-0.6Zr reaches 15.1,which is higher than that of Mg-10Gd-4Y0.6Zr alloy.The improving mechanism of elastic modulus by the LPSO phases and the influence on the alloy mechanical properties are also analyzed.
基金supported by the National Key R&D Program of China(No.2021YFB3701100)the Joint Funds of the National Natural Science Foundation of China(No.U22A20187)+4 种基金the Science and Technology Innovation Program of Hunan Province(Nos.2023RC3268,2021JC0005 and 2020RC4013)the Science Fund of State Key Laboratory of Advanced Design and Manu-facturing Technology for Vehicle(No.32117009)the Projects“Development of lightweight high-performance Mg alloys profiles manufacturing technologies”and“Research and development of room-temperature bendable Mg alloy thin sheets manufactur-ing technology”from QingHai Salt Lake Industry Co.,Ltd.(Nos.2022-Z-0810000000-21-ZC0609-0001 and 2022-Z-08)the“Technology Innovation 2025”Major Special Project of Ningbo CityThe first-principles calculations work was carried out using software provided by the High Performance Computing Center of Central South University.
文摘In the present work,a new Mg-Bi based alloy is developed by the addition of Zn and Ca in equiva-lent atom fraction with Bi.Mg-Bi and Mg-Bi-Zn-Ca alloys were prepared by extrusion at a ram speed of 20 mm/s.Room temperature mechanical properties and creep behaviors at 423 K were investigated.The results show that Zn and Ca co-addition shows little influence on average grain size and texture in-tensity but changes the dispersive Mg_(3)Bi_(2)into Mg_(2)Bi_(2)Ca particles in different sizes and a lower density.Twinning is largely activated during room-temperature deformation.Consequently,a slightly decreased proof strength but tripled elongation is shown at room temperature.Unexpectedly,large enhancement in creep resistance is detected after the co-alloying of Zn and Ca and the minimum creep rate is reduced by 10 to 20 times in the BZX621 alloy.Stress exponent n=4-5 indicates that the creep is a dislocation-climb controlled type.Post-mortem characterization on microstructure shows slip of dislocationc+aare also largely found in B6 as well as BZX621 alloy and cross-slip is detected more severe in B6 alloy.Dynamic segregation and precipitation are also seen in both alloys.Bi-clusters are seen dispersive across the grains in B6 and so did the PFZs that could undermine creep resistance at the grain boundaries.By contrast,Zn-rich needle-like precipitates are developed at most“ends”ofc+adislocations,which would hinder the further dislocation motions and thus improve the creep resistance.First-principles cal-culations were adopted and the results show that the thermal stability and thermomechanical properties of Mg_(2)Bi_(2)Ca are much better than that of Mg_(3)Bi_(2).Stacking faults energy is lowered down with the co-addition of Ca and Zn,which could inhibit the rate of dislocation climb and cross-slip.As a result,the im-proved creep resistance is obtained in the Mg-Bi-Zn-Ca alloys.Microstructural and controlling mechanism changes by thermal activation result in the unexpected enhancement in creep resistance with decreased room-temperature proof strength after co-addition.These findings could contribute to the development and optimization of creep-resistant Mg alloys in the future.
文摘Steel-concrete composite beams,due to their superior mechanical properties,are widely utilized in engineering structures.This study systematically investigates the calculation methods for internal forces and load-bearing capacity of composite beams based on elastic theory,with a focus on the transformed section method and its application under varying neutral axis positions.By deriving the geometric characteristics of the transformed section and incorporating a reduction factor accounting for slip effects,a computational model for sectional stress and ultimate load-bearing capacity is established.The results demonstrate that the slip effect significantly influences the flexural load-bearing capacity of composite beams.The proposed reduction factor,which considers the influence of the steel beam’s top flange thickness,offers higher accuracy compared to traditional methods.These findings provide a theoretical foundation for the design and analysis of composite beams,with significant practical engineering value.
基金Project(22376221)supported by the National Natural Science Foundation of ChinaProject(2024JJ2074)supported by the Natural Science Foundation of Hunan Province,ChinaProject(2023QNRC001)supported by the Young Elite Scientists Sponsorship Program by CAST。
文摘Understanding the adsorption behavior of heavy metals and metalloids on clay minerals is essential for remediating heavy metal-contaminated soils.The adsorption of heavy metals and metalloids on illite(001)and sodium montmorillonite(Na-MMT)(001)surfaces was investigated using first-principles calculations in this study,especially As atom and H_(3)AsO_(3) molecule.The adsorption energies of the As atom were−1.94 eV on the illite(001)and−0.56 eV on the Na-MMT(001),whereas,the adsorption energies of the H_(3)AsO_(3) molecule were−1.40 eV on illite(001)and−1.01 eV on Na-MMT(001).The above results indicate that the adsorption was more energetically favorable on illite(001).Additionally,compared to Na-MMT(001),there were more significant interactions between the atoms/molecules on the illite(001).After As atom and H_(3)AsO_(3) molecule adsorption,the electrons were transferred from mineral surface atoms to the adsorbates on both illite(001)and Na-MMT(001)surfaces.Moreover,the adsorption of As atom on illite(001)and Na-MMT(001)surfaces were more energy favorable compared to Hg,Cd,and Cr atoms.Overall,this work provides new insights into the adsorption behavior of As atoms and As molecules on illite and Na-MMT.The results indicate that illite rich soils are more prone to contamination by arsenic compared to soils primarily composed of Na-MMT minerals.
基金Zhejiang Provincial Natural Science Foundation of China for Young Scholars(Project No.:LQ20A020009)National College Students’Innovation and Entrepreneurship Training Program(Project No.:202311842014X)。
文摘The longitudinal cracks distributed along the dam axis in the corridor of a dam may have potential safety hazards.According to the detection results of crack depth and width and the analysis of monitoring data,a three-dimensional finite element model is established for numerical simulation calculation and the influence of cracks on the safety of dam structure is analyzed from different aspects such as deformation,stress value,and distribution range.The calculation results show that the maximum principal tensile stress value and the location of the dam body are basically independent of the change of crack depth(within 1.0 m).Regarding local stress around the corridor,the high upstream water level causes cracks to deepen,resulting in an increase in the maximum tensile stress near the crack tip and an expansion of the tensile stress region.
基金Supported by Beijing Natural Science Foundation from Beijing Municipal Government(No.7202030).
文摘AIM:To investigate the effect of pharmacological pupil alterations on intraocular lens(IOL)power calculations.METHODS:A systematic review and Meta-analysis of studies published before December 2023 in the PubMed,Embase,and Cochrane library databases on the accuracy of pharmacological pupil changes on IOL power calculation was performed.The primary outcome was the results of IOL power calculations before and after the use of medications.Subgroup analyses were performed based on participants’basic characteristics,such as age,axial length(AL),and whether miosis or mydriasis were used as classification criteria for further analyses.Each eligible study was evaluated for potential risk of bias by the AHRQ assessment scale.The study was registered on PROSPERO(CRD 42024497535).RESULTS:A total of 3062 eyes from 21 studies were eligible.There was no significant difference in the IOL power calculation before and after pharmacological pupil changes using any of the Hoffer Q(WMD=0.055,95%CI=-0.046–0.156;P=0.29),SRK/T(WMD=0.003,95%CI=-0.073–0.080;P=0.93),Haigis(WMD=-0.030,95%CI=-0.176–0.116;P=0.69),Holladay 2(WMD=-0.042,95%CI=-0.366–0.282;P=0.80),and Barrett Universal Ⅱ(WMD=0.033,95%CI=-0.061–0.127;P=0.49)formulas.On the measurement of parameters related to IOL power calculation,for either miosis or mydriasis AL(P=0.98 and 0.29,respectively),lens thickness(P=0.96 and 0.13,respectively),and mean keratometry(P=0.90 and 0.86,respectively)did not present significant differences,while anterior chamber depth(P=0.07 and<0.01,respectively)and white-to-white distance(P=0.01 and 0.04,respectively)changed significantly between the two measurements prior and posterior.At the same time,despite there being some participants with the difference between the before and after calculations greater than 0.5 diopter,there was no significant difference in the incidence rate between these formulas.CONCLUSION:There is no significant effect of pharmacological pupil changes on the IOL power calculation.It will considerably reduce the visit time burden for patients who require cataract surgery.
基金supported by the National Natural Science Foundation of China(Nos.52364044 and 52204364)Central Guidance on Local Science and Technology Development Fund Projects of Inner Mongolia Autonomous Region(No.2022ZY0090)Basic Scientific Research Business Expenses of Colleges and Universities in Inner Mongolia Autonomous Region(Nos.2023QNJS011 and 0406082226).
文摘The micro-area characterization experiments like scanning Kelvin probe force microscope(SKPFM)and Kernel average misorientation have the defects of complex sample preparation and occasional errors in test results,which makes it impossible to accurately and quickly analyze the pitting behavior induced by inclusions in some cases,prompting attempts to turn to simulation calculation research.The method of calculating band structure and work function can be used to replace current-sensing atomic force microscopy and SKPFM to detect the potential and conductivity of the sample.The band structure results show that Al_(2)O_(3) inclusion is an insulator and non-conductive,and it will not form galvanic corrosion with the matrix.Al_(2)O_(3) inclusion does not dissolve because its work function is higher than that of the matrix.Moreover,the stress concentration of the matrix around the inclusion can be characterized by first-principles calculation coupled with finite element simulation.The results show that the stress concentration degree of the matrix around Al_(2)O_(3) inclusion is serious,and the galvanic corrosion is formed between the high and the low stress concentration areas,which can be used to explain the reason of the pitting induced by Al_(2)O_(3) inclusions.
基金supported by the National Natural Science Foundation of China(Nos.22207036,22277034,22477034,and 22107033)Interdisciplinary Research Program of Huazhong University of Science and Technology(No.2023JCYJ037)International Cooperation Project of Hubei Provincial Key R&D Plan(No.2023EHA040)。
文摘Two pairs of novel 6/6/6/9 tetracyclic merosesquiterpenoid enantiomers,dauroxonanols A(1)and B(2),possessing an unprecedented 9,15-dioxatetracyclo[8.5.3.0^(4.17).0^(14.18)]octadecane core skeleton,were isolated from Rhododendron dauricum.The nuclear magnetic resonance(NMR)spectra of 1 and 2 showed very broad resonances,and^(13)C NMR spectrum of 1 exhibited only 13 instead of 22 carbon resonances.These broadening or missing NMR resonances led to a great challenge to elucidate their structures using NMR data analysis.Their structures and absolute configurations of 1 and 2 were finally determined by single crystal X-ray diffraction analysis,chiral separation,and electronic circular dichroism(ECD)calculations.Plausible biosynthetic pathways for 1 and 2 are proposed.Conformational analysis,density functional theory(DFT)calculations,and dynamic NMR assigned the coalescent NMR phenomena of 1 and 2 to the conformational changes of the flexible oxonane ring.Dauroxonanols A(1)and B(2)showed potentα-glucosidase inhibitory activities,2-8 times potent than acarbose,an antidiabetic drug targetingα-glucosidase in clinic.
基金supported by the National Natural Science Foundation of China(Grant no.52463025,and 52062035)the Major Discipline Academic and Technical Leaders Training Program of Jiangxi Province(Grant no.20213BCJ22056)+2 种基金the Key R&D Program of Jiangxi Province(Grant no.20223BBE51028)the Jiangxi Province Key Laboratory of Lithium-ion Battery Materials and Application(2024SSY05202)the Jiangxi Province Graduate Innovation Special Fund Project(YC2023-B004)。
文摘Oxygen release from Ni-rich cathode is one of the major structural degradations resulting in rapid performance fading in lithium-ion batteries(LIBs).The energy gap between the transition metals(TM)-d band and the O-p band serves as an effective evaluation metric in characterizing the potential for oxygen release.Given that the primary oxidation factors of NCM811 materials vary at different states of charge(SOC),this study employs high-throughput density functional theory(DFT)calculations combined with machine learning(ML)to systematically investigate the regulation mechanism of heteroatoms on the energy gap between the TM-d band(TM=Ni,Co)and O-p band at various SOC levels.Highthroughput DFT calculations were used to study doping thermodynamic stability and complete the database.The results indicate that dopant atoms remain at their original sites even at 50%SOC.Correlation analysis reveals that at 0 SOC,the dopant reduces Ni-O bonding interactions by forming its own bonds with oxygen,thereby preventing lattice oxygen escape and weakening the oxygen binding of the system during Ni redox.At 50%SOC,the dopant and Co atoms synergistically strengthen their bonding interactions with oxygen,thereby maintaining structural stability and inhibiting lattice oxygen escape.Based on R^(2)and root-mean-square error(RMSE),the gradient boosting regression(GBR)algorithm is identified as optimal for predicting the energy gaps between the Ni-d band and O-p band,as well as between the Co-d band and O-p band.Feature importance analysis demonstrates that the magnetic moment(Dma)of the doped atom significantly contributes to the prediction of ΔNi-O and ΔCo-O.In this study,the energy gap regulation mechanisms of Ni-d/O-p and Co-d/O-p are systematically investigated using non-empirical first principle calculations combined with data-driven machine learning,aiming to provide insights into the electrochemical stability of NCM811 and related materials.
基金Supported by the Joint Fund Key Program of the National Natural Science Foundation of China(U21B2069)Key Research and Development Program of Shandong Province(2022CXGC020407)Basic Science Center Program of the National Natural Science Foundation of China(52288101)。
文摘By comprehensively considering the influences of temperature and pressure on fluid density in high temperature and high pressure(HTHP)wells in deepwater fractured formations and the effects of formation fracture deformation on well shut-in afterflow,this study couples the shut-in temperature field model,fracture deformation model,and gas flow model to establish a wellbore pressure calculation model incorporating thermo-hydro-mechanical coupling effects.The research analyzes the governing patterns of geothermal gradient,bottomhole pressure difference,drilling fluid pit gain,and kick index on casing head pressure,and establishes a shut-in pressure determination chart for HPHT wells based on coupled model calculation results.The study results show:geothermal gradient,bottomhole pressure difference,and drilling fluid pit gain exhibit positive correlations with casing head pressure;higher kick indices accelerate pressure rising rates while maintaining a constant maximum casing pressure;validation against field case data demonstrates over 95%accuracy in predicting wellbore pressure recovery after shut-in,with the pressure determination chart achieving 97.2%accuracy in target casing head pressure prediction and 98.3%accuracy in target shut-in time.This method enables accurate acquisition of formation pressure after HPHT well shut-in,providing reliable technical support for subsequent well control measures and ensuring safe and efficient development of deepwater and deep hydrocarbon reservoirs.
基金supported and funded internally through Dr. Catherine Johnson's research funds at Missouri S&T
文摘This study investigates the application of Gurney and flight of fragment equations,typically used to predict metal fragment velocities,in modeling the water jet behavior.Three shotgun cartridge sizes were used as the energy source:2.59 g,5.83 g,and 7.13 g.Two configurations were tested:standard(full-barrel water load)and"negative 8"(partial water load).High-speed footage captured water column velocities,and Gurney models,including infinitely tamped and open-faced configurations,combined with the flight of fragment model were used to assess prediction accuracy.Results showed charge strength significantly affects water column velocity,with higher strengths yielding greater stability and velocity retention over distance.The infinitely tamped Gurney model closely predicted experimental velocities,deviating by as little as 1.4%for standard charges and 2.8% for negative 8 charges.Additionally,interesting dynamics such as a 1-2°rise in jet height and the rear overtaking the front was observed.These findings have significant implications for optimizing PAN disruptors and enhancing performance in high-velocity fluid applications and explosive breaching systems.
基金Supported by the Joint Funding Project of Municipal Schools(Colleges)of Science and Technology Program of Guangzhou,China(No.2023A03J0188)the Construction Project of High-Level Hospitals in Guangdong Province(No.303020102)the Natural Science Fund of Guangdong Province(No.2023A1515011102).
文摘AIM:To evaluate the accuracy of intraocular lens(IOL)power calculation formulas with/without preoperative aphakic anterior chamber depth(aph-ACD)in pediatric aphakia.METHODS:A total of 102 pediatric patients(150 eyes)undergoing secondary IOL implantation were divided into two groups(in-the-bag or ciliary sulcus).Prediction error was calculated for 9 IOL power calculation formulas,including:1)not requiring ACD:Hoffer Q,Holladay 1,SRK/T;2)usable without or with entering ACD:Barrett Universal II(BUII),Emmetropia Verifying Optical(EVO)2.0,and Ladas Artificial Intelligence Super(Ladas AI);3)requiring ACD:Haigis,Kane,and Pearl-DGS.Mean prediction error(ME),mean absolute error(MAE),median absolute error(MedAE)and the percentage of eyes within±0.25,±0.50,±0.75,and±1.00 D were calculated.RESULTS:For the BUII,EVO 2.0,and Ladas AI,with aph-ACD demonstrated a higher MedAE compared to without aph-ACD(BUII:1.27 vs 1.13 D,EVO 2.0:1.26 vs 1.06 D,Ladas AI:1.30 vs 1.10 D;all P<0.05).Formulas requiring ACD(Haigis,Kane,and Pearl-DGS)exhibited larger MedAE than those not requiring aph-ACD(Hoffer Q,Holladay 1,and SRK/T;P<0.05).In the capsular group,the percentage of eyes within±1.00 D ranged from 44.83%to 74.14%,and it was 19.57%to 32.61%in the sulcus group.CONCLUSION:The introduction of aph-ACD does not improve the accuracy of IOL calculation for pediatric aphakia,regardless of in-the-bag or sulcus IOL secondary implantation.The relationship between aph-ACD and effective lens position in pediatric aphakia warrants further study.
基金supported by the Fundamental Research Funds for the Central Universities(No.2024QN11072)National Natural Science Foundation of China(Nos.52404264 and 52174217)State Key Program of the National Natural Science Foundation of China(No.52034008)。
文摘The deformation energy(Wd)of soil-like tectonic coal is crucial for investigating the mechanism of coal and gas outbursts.Tectonic coal has a significant nonlinear constitutive relationship,which makes traditional elastic-based models for computing Wdunsuitable.Inspired by critical state soil mechanics,this study theoretically established a new calculation model of Wdsuitable for the coal with nonlinear deformation characteristics.In the new model,the relationship between energy and stress no longer follows the square law(observed in traditional linear elastic models)but exhibits a power function,with the theoretical value of the power exponent ranging between 1 and 2.Hydrostatic cyclic loading and unloading experiments were conducted on four groups of tectonic coal samples and one group of intact coal samples.The results indicated that the relationship between Wdand stress for both intact and tectonic coal follows a power law.The exponents for intact and tectonic coal are close to 2 and 1,respectively.The stress-strain curve of intact coal exhibits small deformation and linear characteristics,whereas the stress-strain curves of tectonic coal show large deformation and nonlinear characteristics.The study specifically investigates the role of coal viscosity in the cyclic loading/unloading process.The downward bending in the unloading curves can be attributed to the time-dependent characteristics of coal,particularly its viscoelastic behavior.Based on experimental statistics,the calculation model of Wdwas further simplified.The simplified model involves only one unknown parameter,which is the power exponent between Wdand stress.The measured Wdof the coal samples increases with the number of load cycles.This phenomenon is attributed to coal's viscoelastic deformation.Within the same stress,the Wdof tectonic coal is an order of magnitude greater than that of intact coal.The calculation model of Wdproposed in this paper provides a new tool for studying the energy principle of coal and gas outbursts.
基金co-supported by the National Natural Science Foundation of China(No.12072365)the Technology Innovation Team of Manned Space Engineering,China。
文摘Aimed at the demand of contingency return at any time during the near-moon phase in the manned lunar landing missions,a fast calculation method for three-impulse contingency return trajectories is proposed.Firstly,a three-impulse contingency return trajectory scheme is presented by combining the Lambert transfer and maneuver at the special point.Secondly,a calculation model of three-impulse contingency return trajectories is established.Then,fast calculation methods are proposed by adopting the high-order Taylor expansion of differential algebra in the twobody trajectory dynamics model and perturbed trajectory dynamics model.Finally,the performance of the proposed methods is verified by numerical simulation.The results indicate that the fast calculation method of two-body trajectory has higher calculation efficiency compared to the semi-analytical calculation method under a certain accuracy condition.Due to its high efficiency,the characteristics of the three-impulse contingency return trajectories under different contingency scenarios are further analyzed expeditiously.These findings can be used for the design of contingency return trajectories in future manned lunar landing missions.
