Ice crystal icing is an important cause of accidents in aircraft engines.Ice formation in aircraft engines can cause internal blades to freeze,affecting the quality of the air flow field and blocking the flow path.On ...Ice crystal icing is an important cause of accidents in aircraft engines.Ice formation in aircraft engines can cause internal blades to freeze,affecting the quality of the air flow field and blocking the flow path.On the other hand,the entry of ice crystal particles into the combustion chamber can cause a decrease in temperature or even flameout,leading to engine surge or shutdown.Therefore,it is necessary to conduct multiphase flow tests on ice crystals for aircraft components such as aircraft engines.Conducting ice crystal multiphase flow tests on aircraft is an effective research method,but it requires the construction of an ice crystal multiphase flow test platform that meets relevant technical requirements.The paper focuses on the relevant experimental requirements and combines wind tunnel test structures to conduct multiphase flow numerical simulations on various forms of jet pipelines,obtaining particle motion distribution results.After comparison,the optimal form of jet structure is obtained,providing the best selection scheme for the design of relevant wind tunnel structures.展开更多
Hydrogen displays the potential to partially replace pulverized coal injection(PCI)in the blast furnace,and it can reduce CO_(2)emissions.In this paper,a three-dimensional mathematical model of hydrogen and pulverized...Hydrogen displays the potential to partially replace pulverized coal injection(PCI)in the blast furnace,and it can reduce CO_(2)emissions.In this paper,a three-dimensional mathematical model of hydrogen and pulverized coal co-injection in blast furnace tuyere was established through numerical simulation,and the effect of hydrogen injection and oxygen enrichment interaction on pulverized coal combustion and raceway smelting was investigated.The simulation results indicate that when the coal injection rate decreased from 36 to 30t/h and the hydrogen injection increased from 0 to 3600 m^(3)/h,the CO_(2)emissions decreased from 1860 to 1551 kg/t,which represents a16.6%reduction,and the pulverized coal burnout decreased from 70.1%to 63.7%.The heat released from hydrogen combustion can not only promote the volatilization of pulverized coal but also affect the combustion reaction between volatilization and oxygen,which resulted in a decrease in the temperature at the end of the raceway.Co-injection of hydrogen with PCI increased the wall temperature near the upper half part of the raceway and at the outlet of the tuyere,which required a high cooling efficiency to extend the service life of the blast furnace.The increase in oxygen level compensated for the decreased average temperature in the raceway due to hydrogen injection.The increase in the oxygen content by 3%while maintaining constant hydrogen and PCI injection rates increased the burnout and average raceway temperature by 4.2%and 43 K,respectively.The mole fraction of CO and H_(2) production increased by 0.04 and 0.02,respectively.Burnout can be improved through optimization of the particle size distribution of pulverized coal.展开更多
Produced water reinjection is a common strategy in offshore oilfield operations,yet the presence of solid particles in produced water can lead to localized formation pressure buildup,increasing the risk of rock fractu...Produced water reinjection is a common strategy in offshore oilfield operations,yet the presence of solid particles in produced water can lead to localized formation pressure buildup,increasing the risk of rock fracturing and leakage.In this study,we present an integrated experimental and numerical investigation to quantify the effects of particle migration on formation pressure and the spatial diffusion of injected water.Dynamic plugging experiments were performed to systematically examine the influence of injection rate and injection volume on core permeability.Results demonstrate that higher injection rates substantially reduce permeability,and the derived relationship between permeability and injection volume enables dynamic assessment of permeability evolution during reinjection.Complementary numerical simulations explored the impacts of injection length,particle concentration,and injection rate on formation pressure and diffusion behavior.Findings indicate that extending the injection section promotes pressure distribution and enlarges the diffusion area,whereas elevated particle concentrations and injection rates accelerate formation plugging,causing rapid pressure rise and constrained diffusion.展开更多
The uplift resistance of the soil overlying shield tunnels significantly impacts their anti-floating stability.However,research on uplift resistance concerning special-shaped shield tunnels is limited.This study combi...The uplift resistance of the soil overlying shield tunnels significantly impacts their anti-floating stability.However,research on uplift resistance concerning special-shaped shield tunnels is limited.This study combines numerical simulation with machine learning techniques to explore this issue.It presents a summary of special-shaped tunnel geometries and introduces a shape coefficient.Through the finite element software,Plaxis3D,the study simulates six key parameters—shape coefficient,burial depth ratio,tunnel’s longest horizontal length,internal friction angle,cohesion,and soil submerged bulk density—that impact uplift resistance across different conditions.Employing XGBoost and ANN methods,the feature importance of each parameter was analyzed based on the numerical simulation results.The findings demonstrate that a tunnel shape more closely resembling a circle leads to reduced uplift resistance in the overlying soil,whereas other parameters exhibit the contrary effects.Furthermore,the study reveals a diminishing trend in the feature importance of buried depth ratio,internal friction angle,tunnel longest horizontal length,cohesion,soil submerged bulk density,and shape coefficient in influencing uplift resistance.展开更多
Wire arc additive manufacturing(WAAM)has emerged as a promising approach for fabricating large-scale components.However,conventional WAAM still faces challenges in optimizing microstructural evolution,minimizing addit...Wire arc additive manufacturing(WAAM)has emerged as a promising approach for fabricating large-scale components.However,conventional WAAM still faces challenges in optimizing microstructural evolution,minimizing additive-induced defects,and alleviating residual stress and deformation,all of which are critical for enhancing the mechanical performance of the manufactured parts.Integrating interlayer friction stir processing(FSP)into WAAM significantly enhances the quality of deposited materials.However,numerical simulation research focusing on elucidating the associated thermomechanical coupling mechanisms remains insufficient.A comprehensive numerical model was developed to simulate the thermomechanical coupling behavior in friction stir-assisted WAAM.The influence of post-deposition FSP on the coupled thermomechanical response of the WAAM process was analyzed quantitatively.Moreover,the residual stress distribution and deformation behavior under both single-layer and multilayer deposition conditions were investigated.Thermal analysis of different deposition layers in WAAM and friction stir-assisted WAAM was conducted.Results show that subsequent layer deposition induces partial remelting of the previously solidified layer,whereas FSP does not cause such remelting.Furthermore,thermal stress and deformation analysis confirm that interlayer FSP effectively mitigates residual stresses and distortion in WAAM components,thereby improving their structural integrity and mechanical properties.展开更多
Large language models(LLMs)have revolutionized AI applications across diverse domains.However,their widespread deployment has introduced critical security vulnerabilities,particularly prompt injection attacks that man...Large language models(LLMs)have revolutionized AI applications across diverse domains.However,their widespread deployment has introduced critical security vulnerabilities,particularly prompt injection attacks that manipulate model behavior through malicious instructions.Following Kitchenham’s guidelines,this systematic review synthesizes 128 peer-reviewed studies from 2022 to 2025 to provide a unified understanding of this rapidly evolving threat landscape.Our findings reveal a swift progression from simple direct injections to sophisticated multimodal attacks,achieving over 90%success rates against unprotected systems.In response,defense mechanisms show varying effectiveness:input preprocessing achieves 60%–80%detection rates and advanced architectural defenses demonstrate up to 95%protection against known patterns,though significant gaps persist against novel attack vectors.We identified 37 distinct defense approaches across three categories,but standardized evaluation frameworks remain limited.Our analysis attributes these vulnerabilities to fundamental LLM architectural limitations,such as the inability to distinguish instructions from data and attention mechanism vulnerabilities.This highlights critical research directions such as formal verification methods,standardized evaluation protocols,and architectural innovations for inherently secure LLM designs.展开更多
Background:Penile augmentation through injectable substances is becoming increasingly common.A growing number of aesthetic clinics are developing penile enlargement procedures using various injectable materials.Althou...Background:Penile augmentation through injectable substances is becoming increasingly common.A growing number of aesthetic clinics are developing penile enlargement procedures using various injectable materials.Although these procedures are now performed in more controlled and medically supervised environments,their long-term outcomes remain poorly understood.The promotion of such medical treatments contributes to an increasing interest among adult males in self-injection as a method to alleviate psychological distress associated with penile size concerns.At the same time,access to injectable substances through unofficial or unregulated sources has become increasingly easy.Tor our knowledge,we report the first documented case of self-injection with Garamycin®(gentamicin)cream,contributing to the literature on the often multidisciplinary management of penile enlargement injections,a field still lacking well-established guidelines.Case Description:This case report describes a young patient who self-injected Garamycin®into the penis for the purpose of enlargement.He presented to our urology department with worsening symptoms,including severe and poorly tolerated pain.His primary request was prompt relief of pain while preserving,as much as possible,the aesthetic appearance and functional integrity of his penis.This case required a multi-stage surgical approach to salvage the penis and preserve both its structural integrity and functional outcome.Conclusions:To our knowledge,this case report documents the first reported instance of Garamycin®injection performed for the purpose of penile enlargement.It provides insight into the clinical course of such penile cream injections,demonstrates that a two-stage scrotal flap can achieve both functional and aesthetic outcomes,and highlights the importance of comprehensive management particularly addressing the traumatic impact of penile deformity secondary to inflammation and/or infection,as well as the body dysmorphic concerns often associated with these cases.展开更多
In this investigation,a hybrid approach integrating the IDDES turbulence model and FW-H is employed to forecast the hydroacoustic of the rim driven thruster(RDT)under non-cavitation and uniform flow conditions at vary...In this investigation,a hybrid approach integrating the IDDES turbulence model and FW-H is employed to forecast the hydroacoustic of the rim driven thruster(RDT)under non-cavitation and uniform flow conditions at varying loading conditions(J=0.3 and J=0.6).It is revealed that the quadrupole term contribution in the P-FWH method significantly affects the monopole term in the low-frequency region,while it mainly affects the dipole term in the high-frequency region.Specifically,the overall sound pressure levels(SPL)of the RDT using the P-FWH method are 2.27 dB,10.03 dB,and 16.73 dB at the receiving points from R1 to R3 under the heavy-loaded condition,while they increase by 0.67 dB at R1,and decrease by 14.93 dB at R2,and 22.20 dB at R3,for the light-loaded condition.The study also utilizes the pressure-time derivatives to visualize the numerical noise and to pinpoint the dynamics of the vortex cores,and the optimization of the grid design can significantly reduce the numerical noise.The computational accuracy of the P-FWH method can meet the noise requirements for the preliminary design of rim driven thrusters.展开更多
Machine learning-assisted methods for rapid and accurate prediction of temperature field,mushy zone,and grain size were proposed for the heating−cooling combined mold(HCCM)horizontal continuous casting of C70250 alloy...Machine learning-assisted methods for rapid and accurate prediction of temperature field,mushy zone,and grain size were proposed for the heating−cooling combined mold(HCCM)horizontal continuous casting of C70250 alloy plates.First,finite element simulations of casting processes were carried out with various parameters to build a dataset.Subsequently,different machine learning algorithms were employed to achieve high precision in predicting temperature fields,mushy zone locations,mushy zone inclination angle,and billet grain size.Finally,the process parameters were quickly optimized using a strategy consisting of random generation,prediction,and screening,allowing the mushy zone to be controlled to the desired target.The optimized parameters are 1234℃for heating mold temperature,47 mm/min for casting speed,and 10 L/min for cooling water flow rate.The optimized mushy zone is located in the middle of the second heat insulation section and has an inclination angle of roughly 7°.展开更多
As binary geological media,soil-rock mixtures(SRMs)exhibit a distinct gradational composition,leading to their unique mechanical behaviors.To appraise the stability of SRM slopes,it is essential to determine equivalen...As binary geological media,soil-rock mixtures(SRMs)exhibit a distinct gradational composition,leading to their unique mechanical behaviors.To appraise the stability of SRM slopes,it is essential to determine equivalent parameters of SRMs,which are typically obtained through experimental and numerical methods.In contrasted to other numerical methods,the numerical manifold method(NMM)is more effective in addressing SRM problems.This is because the high-precision regular mathematical meshes in NMM can be used without aligning with the soil-rock interfaces and boundaries of SRMs.In the current research,the equivalent strength parameters of SRMs,i.e.the equivalent cohesion ce and internal friction angleϕ_(e),are determined using NMM.Initially,an NMM triaxial numerical model is established and validated based on triaxial experiments.Subsequently,the soil and rock parameters are derived through parameter inversion.Moreover,the impacts of rock content,size,shape and rock blocks'major-axis orientation on ce andϕ_(e) of SRMs are thoroughly examined using the NMM triaxial numerical model.Additionally,a fitting function is proposed to linkϕ_(e) to the rock content and size of SRMs.When other influencing factors are fixed,the above fitting model leads to the following conclusions:(1)the predictedϕ_(e) of SRMs increase with the increase of rock content;and(2)SRM samples with smaller rocks display a higher predictedϕ_(e).展开更多
Objective:To explore the therapeutic effect of double-puncture tympanic membrane puncture and tympanic cavity drug injection in patients with acute secretory otitis media.Methods:A total of 84 patients with acute secr...Objective:To explore the therapeutic effect of double-puncture tympanic membrane puncture and tympanic cavity drug injection in patients with acute secretory otitis media.Methods:A total of 84 patients with acute secretory otitis media admitted to our hospital from June 2024 to June 2025 were selected and randomly divided into two groups by drawing lots.The control group(42 cases)was treated with the traditional single-puncture tympanic membrane puncture and tympanic cavity drug injection method,while the observation group(42 cases)was treated with the double-puncture tympanic membrane puncture and tympanic cavity drug injection method.The therapeutic effects of the two groups were compared.Results:The overall treatment response rate,overall complication rate,time to symptom relief,and improvement in hearing threshold in the observation group were all superior to those in the control group,with statistically significant differences(P<0.05).Conclusion:For acute secretory otitis media,the treatment method of double-puncture tympanic membrane puncture and tympanic cavity drug injection demonstrates definite efficacy,significantly reducing the incidence of complications,accelerating symptom relief,and improving hearing function,making it worthy of promotion.展开更多
Hydraulic fracturing serves as a critical technology for reservoir stimulation in deep coalbed methane(CBM)development,where the mechanical properties of gangue layers exert a significant control on fracture propagati...Hydraulic fracturing serves as a critical technology for reservoir stimulation in deep coalbed methane(CBM)development,where the mechanical properties of gangue layers exert a significant control on fracture propagation behavior.To address the unclear mechanisms governing fracture penetration across coal-gangue interfaces,this study employs the Continuum-Discontinuum Element Method(CDEM)to simulate and analyze the vertical propagation of hydraulic fractures initiating within coal seams,based on geomechanical parameters derived from the deep Benxi Formation coal seams in the southeastern Ordos Basin.The investigation systematically examines the influence of geological and operational parameters on cross-interfacial fracture growth.Results demonstrate that vertical stress difference,elastic modulus contrast between coal and gangue layers,interfacial stress differential,and interfacial cohesion at coal-gangue interfaces are critical factors governing hydraulic fracture penetration through these interfaces.High vertical stress differences(>3 MPa)inhibit interfacial dilation,promoting predominant crosslayer fracture propagation.Reduced interfacial stress contrasts and enhanced interfacial cohesion facilitate fracture penetration across interfaces.Furthermore,smaller elastic modulus contrasts between coal and gangue correlate with increased interfacial aperture.Finally,lower injection rates effectively suppress vertical fracture propagation in deep coal reservoirs.This study elucidates the characteristics and mechanisms governing cross-layer fracture propagation in coal–rock composites with interbedded partings,and delineates the dynamic evolution laws and dominant controlling factors involved.Thefindings provide critical theoretical insights for the optimization of fracture design and the efficient development of deep coalbed methane reservoirs.展开更多
Marine thin plates are susceptible to welding deformation owing to their low structural stiffness.Therefore,the efficient and accurate prediction of welding deformation is essential for improving welding quality.The t...Marine thin plates are susceptible to welding deformation owing to their low structural stiffness.Therefore,the efficient and accurate prediction of welding deformation is essential for improving welding quality.The traditional thermal elastic-plastic finite element method(TEP-FEM)can accurately predict welding deformation.However,its efficiency is low because of the complex nonlinear transient computation,making it difficult to meet the needs of rapid engineering evaluation.To address this challenge,this study proposes an efficient prediction method for welding deformation in marine thin plate butt welds.This method is based on the coupled temperature gradient-thermal strain method(TG-TSM)that integrates inherent strain theory with a shell element finite element model.The proposed method first extracts the distribution pattern and characteristic value of welding-induced inherent strain through TEP-FEM analysis.This strain is then converted into the equivalent thermal load applied to the shell element model for rapid computation.The proposed method-particularly,the gradual temperature gradient-thermal strain method(GTG-TSM)-achieved improved computational efficiency and consistent precision.Furthermore,the proposed method required much less computation time than the traditional TEP-FEM.Thus,this study lays the foundation for future prediction of welding deformation in more complex marine thin plates.展开更多
Energy shortage has become one of themost concerning issues in the world today,and improving energy utilization efficiency is a key area of research for experts and scholars worldwide.Small-diameter heat exchangers of...Energy shortage has become one of themost concerning issues in the world today,and improving energy utilization efficiency is a key area of research for experts and scholars worldwide.Small-diameter heat exchangers offer advantages such as reduced material usage,lower refrigerant charge,and compact structure.However,they also face challenges,including increased refrigerant pressure drop and smaller heat transfer area inside the tubes.This paper combines the advantages and disadvantages of both small and large-diameter tubes and proposes a combined-diameter heat exchanger,consisting of large and small diameters,for use in the indoor units of split-type air conditioners.There are relatively few studies in this area.In this paper,A theoretical and numerical computation method is employed to establish a theoretical-numerical calculation model,and its reliability is verified through experiments.Using this model,the optimal combined diameters and flow path design for a combined-diameter heat exchanger using R32 as the working fluid are derived.The results show that the heat transfer performance of all combined diameter configurations improves by 2.79%to 8.26%compared to the baseline design,with the coefficient of performance(COP)increasing from 4.15 to 4.27~4.5.These designs can save copper material,but at the cost of an increase in pressure drop by 66.86%to 131.84%.The scheme IIIH,using R32,is the optimal combined-diameter and flow path configuration that balances both heat transfer performance and economic cost.展开更多
Improving the absorbed gas to active desorption and seepage and delaying gas drainage attenuation are considered as key methods for increasing drainage efficiency and gas output.According to the solid mechanics theory...Improving the absorbed gas to active desorption and seepage and delaying gas drainage attenuation are considered as key methods for increasing drainage efficiency and gas output.According to the solid mechanics theory,the nonlinear Darcy seepage theory and thermodynamics,the heat-fluid-solid coupling model for gassy coal has been improved.The numerical model was founded from the improved multi-field coupling model by COMSOL Multiphysics and gas drainage by borehole down the coal seam enhanced by heat injection was modelled.The results show that the heatfluid-solid model with adsorption effects for gassy coal was well simulated by the improved multi-field model.The mechanism of coal seam gas desorption seepage under the combined action of temperature,stress and adsorption can be well described.Gas desorption and seepage can be enhanced by heat injection into coal seams.The gas drainage rate was directly proportional to the temperature of injected heat in the scope of 30-150 ℃ and increasing in the whole modelleddrainage process (0-1000 d).The increased level was maximum in the initial drainage time and decreasing gradually along with drainage time.The increasing ratio of drainage rate was maximum when the temperature raised from 30 to 60 ℃.Although the drainage rate would increase along with increasing temperature,when exceeding 60 ℃,the increasing ratio of drainage rate with rising temperature would decrease.Gas drainage promotion was more effective in coal seams with lower permeability than with higher permeability.The coal seam temperature in a 5 m distance surrounding the heat injection borehole would rise to around 60 ℃ in 3 months.That was much less than the time of gas drainage in the coal mines in sites with low permeability coal seams.Therefore,it is valuable and feasible to inject heat into coal seams to promote gas drainage,and this has strong feasibility for coal seams with low permeability which are widespread in China.展开更多
The technology used to enhance coalbed methane(CBM) recovery by injecting CO_2(CO_2-ECBM) with heat, combining heat injection with CO_2 injection, is still in its infancy; therefore, theoretical studies of this CO_2-E...The technology used to enhance coalbed methane(CBM) recovery by injecting CO_2(CO_2-ECBM) with heat, combining heat injection with CO_2 injection, is still in its infancy; therefore, theoretical studies of this CO_2-ECBM technology should be perused. First, the coupling equations of the di usion–adsorption–seepage–heat transfer fields of gas are established. The displacement processes under di erent pressures and temperatures are simulated by COMSOL. Finally, the displacement effects, a comparison of the CO_2 storage capacity with the CH_4 output and the e ective influencing radius of CO_2 injection are analyzed and discussed. The results show that(1) the displacement pressure and temperature are two key factors influencing the CH_4 output and the CO_2 storage capacity, and the increase in the CO_2 storage capacity is more sensitive to temperature and pressure than the CH_4 output.(2) The gas flow direction is from the injection hole to the discharge hole during the displacement process, and the regions with high velocity are concentrated at the injection hole and the discharge hole.(3) A reduction in the CH_4 concentration and an increase in the CO_2 concentration are obvious during the displacement process.(4) The e ective influencing radius of injecting CO_2 with heat increases with the increase in time and pressure. The relationship between the e ective influencing radius and the injection time of CO_2 has a power exponential function, and there is a linear relationship between the functional coe cient and the injection pressure of CO_2. This numerical simulation study on enhancing CBM recovery by injecting CO_2 with heat can further promote the implementation of CO_2-ECBM project in deep coal seams.展开更多
In order to reduce the "trial-mold" risk and cost,numerical simulation method was applied to micro injection molding weld line development investigation. The micro tensile specimen which has the size of 0.1 ...In order to reduce the "trial-mold" risk and cost,numerical simulation method was applied to micro injection molding weld line development investigation. The micro tensile specimen which has the size of 0.1 mm(depth) ×0.4 mm(width) ×12 mm(length) in test area was selected as the objective part,and polypropylene(PP) as the experimental material. Respectively with specific commercial software(Mold Flow) and general computational fluid dynamic(CFD) software(Comsol Multiphysics) ,the simulation experiments for development of weld line in micro injection molding process were executed and the real comparison experiments were also carried out. The results show that during micro injection molding process,the specific commercial software for normal injection molding process is not valid to describe the micro flow process,the shape of flow front in micro cavity flowing which is important in weld line developing study and the contact angle due to surface tension are not able to be simulated. In order to improve the simulation results for micro weld line development,the general CFD software,which is more flexible in user defining function,is applied. The results show better effects in describing micro fluid flow behavior. As a conclusion,as for weld line forming process,the numerical simulation method can give a characteristic analysis results for processing parameters optimizing in micro injection molding process;but for both kinds of softwares quantitative analysis cannot be obtained unless the boundary condition and micro fluid mathematic model are improved in the future.展开更多
Deep shale reservoirs are characterized by elevated breakdown pressures,diminished fracture complexity,and reduced modified volumes compared to medium and shallow reservoirs.Therefore,it is urgent to investigate parti...Deep shale reservoirs are characterized by elevated breakdown pressures,diminished fracture complexity,and reduced modified volumes compared to medium and shallow reservoirs.Therefore,it is urgent to investigate particular injection strategies that can optimize breakdown pressure and fracturing efficiency to address the increasing demands for deep shale reservoir stimulation.In this study,the efficiency of various stimulation strategies,including multi-cluster simultaneous fracturing,modified alternating fracturing,alternating shut-in fracturing,and cyclic alternating fracturing,was evaluated.Subsequently,the sensitivity of factors such as the cycle index,shut-in time,cluster spacing,and horizontal permeability was investigated.Additionally,the flow distribution effect within the wellbore was discussed.The results indicate that relative to multi-cluster simultaneous fracturing,modified alternating fracturing exhibits reduced susceptibility to the stress shadow effect,which results in earlier breakdown,extended hydraulic fracture lengths,and more consistent propagation despite an increase in breakdown pressure.The alternating shut-in fracturing benefits the increase of fracture length,which is closely related to the shut-in time.Furthermore,cyclic alternating fracturing markedly lowers breakdown pressure and contributes to uniform fracture propagation,in which the cycle count plays an important role.Modified alternating fracturing demonstrates insensitivity to variations in cluster spacing,whereas horizontal permeability is a critical factor affecting fracture length.The wellbore effect restrains the accumulation of pressure and flow near the perforation,delaying the initiation of hydraulic fractures.The simulation results can provide valuable numerical insights for optimizing injection strategies for deep shale hydraulic fracturing.展开更多
文摘Ice crystal icing is an important cause of accidents in aircraft engines.Ice formation in aircraft engines can cause internal blades to freeze,affecting the quality of the air flow field and blocking the flow path.On the other hand,the entry of ice crystal particles into the combustion chamber can cause a decrease in temperature or even flameout,leading to engine surge or shutdown.Therefore,it is necessary to conduct multiphase flow tests on ice crystals for aircraft components such as aircraft engines.Conducting ice crystal multiphase flow tests on aircraft is an effective research method,but it requires the construction of an ice crystal multiphase flow test platform that meets relevant technical requirements.The paper focuses on the relevant experimental requirements and combines wind tunnel test structures to conduct multiphase flow numerical simulations on various forms of jet pipelines,obtaining particle motion distribution results.After comparison,the optimal form of jet structure is obtained,providing the best selection scheme for the design of relevant wind tunnel structures.
基金financially supported by the National Natural Science Foundation of China(No.51904026)the Fundamental Research Funds for the Central Universities(No.06500108)。
文摘Hydrogen displays the potential to partially replace pulverized coal injection(PCI)in the blast furnace,and it can reduce CO_(2)emissions.In this paper,a three-dimensional mathematical model of hydrogen and pulverized coal co-injection in blast furnace tuyere was established through numerical simulation,and the effect of hydrogen injection and oxygen enrichment interaction on pulverized coal combustion and raceway smelting was investigated.The simulation results indicate that when the coal injection rate decreased from 36 to 30t/h and the hydrogen injection increased from 0 to 3600 m^(3)/h,the CO_(2)emissions decreased from 1860 to 1551 kg/t,which represents a16.6%reduction,and the pulverized coal burnout decreased from 70.1%to 63.7%.The heat released from hydrogen combustion can not only promote the volatilization of pulverized coal but also affect the combustion reaction between volatilization and oxygen,which resulted in a decrease in the temperature at the end of the raceway.Co-injection of hydrogen with PCI increased the wall temperature near the upper half part of the raceway and at the outlet of the tuyere,which required a high cooling efficiency to extend the service life of the blast furnace.The increase in oxygen level compensated for the decreased average temperature in the raceway due to hydrogen injection.The increase in the oxygen content by 3%while maintaining constant hydrogen and PCI injection rates increased the burnout and average raceway temperature by 4.2%and 43 K,respectively.The mole fraction of CO and H_(2) production increased by 0.04 and 0.02,respectively.Burnout can be improved through optimization of the particle size distribution of pulverized coal.
基金supported by the National Natural Science Foundation of China(No.52204026).
文摘Produced water reinjection is a common strategy in offshore oilfield operations,yet the presence of solid particles in produced water can lead to localized formation pressure buildup,increasing the risk of rock fracturing and leakage.In this study,we present an integrated experimental and numerical investigation to quantify the effects of particle migration on formation pressure and the spatial diffusion of injected water.Dynamic plugging experiments were performed to systematically examine the influence of injection rate and injection volume on core permeability.Results demonstrate that higher injection rates substantially reduce permeability,and the derived relationship between permeability and injection volume enables dynamic assessment of permeability evolution during reinjection.Complementary numerical simulations explored the impacts of injection length,particle concentration,and injection rate on formation pressure and diffusion behavior.Findings indicate that extending the injection section promotes pressure distribution and enlarges the diffusion area,whereas elevated particle concentrations and injection rates accelerate formation plugging,causing rapid pressure rise and constrained diffusion.
基金Guangzhou Metro Scientific Research Project(No.JT204-100111-23001)Chongqing Municipal Special Project for Technological Innovation and Application Development(No.CSTB2022TIAD-KPX0101)Science and Technology Research and Development Program of China State Railway Group Co.,Ltd.(No.N2023G045)。
文摘The uplift resistance of the soil overlying shield tunnels significantly impacts their anti-floating stability.However,research on uplift resistance concerning special-shaped shield tunnels is limited.This study combines numerical simulation with machine learning techniques to explore this issue.It presents a summary of special-shaped tunnel geometries and introduces a shape coefficient.Through the finite element software,Plaxis3D,the study simulates six key parameters—shape coefficient,burial depth ratio,tunnel’s longest horizontal length,internal friction angle,cohesion,and soil submerged bulk density—that impact uplift resistance across different conditions.Employing XGBoost and ANN methods,the feature importance of each parameter was analyzed based on the numerical simulation results.The findings demonstrate that a tunnel shape more closely resembling a circle leads to reduced uplift resistance in the overlying soil,whereas other parameters exhibit the contrary effects.Furthermore,the study reveals a diminishing trend in the feature importance of buried depth ratio,internal friction angle,tunnel longest horizontal length,cohesion,soil submerged bulk density,and shape coefficient in influencing uplift resistance.
基金National Key Research and Development Program of China(2022YFB4600902)Shandong Provincial Science Foundation for Outstanding Young Scholars(ZR2024YQ020)。
文摘Wire arc additive manufacturing(WAAM)has emerged as a promising approach for fabricating large-scale components.However,conventional WAAM still faces challenges in optimizing microstructural evolution,minimizing additive-induced defects,and alleviating residual stress and deformation,all of which are critical for enhancing the mechanical performance of the manufactured parts.Integrating interlayer friction stir processing(FSP)into WAAM significantly enhances the quality of deposited materials.However,numerical simulation research focusing on elucidating the associated thermomechanical coupling mechanisms remains insufficient.A comprehensive numerical model was developed to simulate the thermomechanical coupling behavior in friction stir-assisted WAAM.The influence of post-deposition FSP on the coupled thermomechanical response of the WAAM process was analyzed quantitatively.Moreover,the residual stress distribution and deformation behavior under both single-layer and multilayer deposition conditions were investigated.Thermal analysis of different deposition layers in WAAM and friction stir-assisted WAAM was conducted.Results show that subsequent layer deposition induces partial remelting of the previously solidified layer,whereas FSP does not cause such remelting.Furthermore,thermal stress and deformation analysis confirm that interlayer FSP effectively mitigates residual stresses and distortion in WAAM components,thereby improving their structural integrity and mechanical properties.
基金supported by 2023 Higher Education Scientific Research Planning Project of China Society of Higher Education(No.23PG0408)2023 Philosophy and Social Science Research Programs in Jiangsu Province(No.2023SJSZ0993)+2 种基金Nantong Science and Technology Project(No.JC2023070)Key Project of Jiangsu Province Education Science 14th Five-Year Plan(Grant No.B-b/2024/02/41)the Open Fund of Advanced Cryptography and System Security Key Laboratory of Sichuan Province(Grant No.SKLACSS-202407).
文摘Large language models(LLMs)have revolutionized AI applications across diverse domains.However,their widespread deployment has introduced critical security vulnerabilities,particularly prompt injection attacks that manipulate model behavior through malicious instructions.Following Kitchenham’s guidelines,this systematic review synthesizes 128 peer-reviewed studies from 2022 to 2025 to provide a unified understanding of this rapidly evolving threat landscape.Our findings reveal a swift progression from simple direct injections to sophisticated multimodal attacks,achieving over 90%success rates against unprotected systems.In response,defense mechanisms show varying effectiveness:input preprocessing achieves 60%–80%detection rates and advanced architectural defenses demonstrate up to 95%protection against known patterns,though significant gaps persist against novel attack vectors.We identified 37 distinct defense approaches across three categories,but standardized evaluation frameworks remain limited.Our analysis attributes these vulnerabilities to fundamental LLM architectural limitations,such as the inability to distinguish instructions from data and attention mechanism vulnerabilities.This highlights critical research directions such as formal verification methods,standardized evaluation protocols,and architectural innovations for inherently secure LLM designs.
文摘Background:Penile augmentation through injectable substances is becoming increasingly common.A growing number of aesthetic clinics are developing penile enlargement procedures using various injectable materials.Although these procedures are now performed in more controlled and medically supervised environments,their long-term outcomes remain poorly understood.The promotion of such medical treatments contributes to an increasing interest among adult males in self-injection as a method to alleviate psychological distress associated with penile size concerns.At the same time,access to injectable substances through unofficial or unregulated sources has become increasingly easy.Tor our knowledge,we report the first documented case of self-injection with Garamycin®(gentamicin)cream,contributing to the literature on the often multidisciplinary management of penile enlargement injections,a field still lacking well-established guidelines.Case Description:This case report describes a young patient who self-injected Garamycin®into the penis for the purpose of enlargement.He presented to our urology department with worsening symptoms,including severe and poorly tolerated pain.His primary request was prompt relief of pain while preserving,as much as possible,the aesthetic appearance and functional integrity of his penis.This case required a multi-stage surgical approach to salvage the penis and preserve both its structural integrity and functional outcome.Conclusions:To our knowledge,this case report documents the first reported instance of Garamycin®injection performed for the purpose of penile enlargement.It provides insight into the clinical course of such penile cream injections,demonstrates that a two-stage scrotal flap can achieve both functional and aesthetic outcomes,and highlights the importance of comprehensive management particularly addressing the traumatic impact of penile deformity secondary to inflammation and/or infection,as well as the body dysmorphic concerns often associated with these cases.
基金The National Natural Science Foundation of China(Grant No.52201376)the Natural Science Foundation of Hubei Province,China(Grant No.2023AFB683).
文摘In this investigation,a hybrid approach integrating the IDDES turbulence model and FW-H is employed to forecast the hydroacoustic of the rim driven thruster(RDT)under non-cavitation and uniform flow conditions at varying loading conditions(J=0.3 and J=0.6).It is revealed that the quadrupole term contribution in the P-FWH method significantly affects the monopole term in the low-frequency region,while it mainly affects the dipole term in the high-frequency region.Specifically,the overall sound pressure levels(SPL)of the RDT using the P-FWH method are 2.27 dB,10.03 dB,and 16.73 dB at the receiving points from R1 to R3 under the heavy-loaded condition,while they increase by 0.67 dB at R1,and decrease by 14.93 dB at R2,and 22.20 dB at R3,for the light-loaded condition.The study also utilizes the pressure-time derivatives to visualize the numerical noise and to pinpoint the dynamics of the vortex cores,and the optimization of the grid design can significantly reduce the numerical noise.The computational accuracy of the P-FWH method can meet the noise requirements for the preliminary design of rim driven thrusters.
基金financially supported by the National Key Research and Development Program of China (No. 2023YFB3812601)the National Natural Science Foundation of China (No. 51925401)the Young Elite Scientists Sponsorship Program by CAST, China (No. 2022QNRC001)。
文摘Machine learning-assisted methods for rapid and accurate prediction of temperature field,mushy zone,and grain size were proposed for the heating−cooling combined mold(HCCM)horizontal continuous casting of C70250 alloy plates.First,finite element simulations of casting processes were carried out with various parameters to build a dataset.Subsequently,different machine learning algorithms were employed to achieve high precision in predicting temperature fields,mushy zone locations,mushy zone inclination angle,and billet grain size.Finally,the process parameters were quickly optimized using a strategy consisting of random generation,prediction,and screening,allowing the mushy zone to be controlled to the desired target.The optimized parameters are 1234℃for heating mold temperature,47 mm/min for casting speed,and 10 L/min for cooling water flow rate.The optimized mushy zone is located in the middle of the second heat insulation section and has an inclination angle of roughly 7°.
基金supported by the National Natural Science Foundation of China(Grant Nos.12272393 and 52130905).
文摘As binary geological media,soil-rock mixtures(SRMs)exhibit a distinct gradational composition,leading to their unique mechanical behaviors.To appraise the stability of SRM slopes,it is essential to determine equivalent parameters of SRMs,which are typically obtained through experimental and numerical methods.In contrasted to other numerical methods,the numerical manifold method(NMM)is more effective in addressing SRM problems.This is because the high-precision regular mathematical meshes in NMM can be used without aligning with the soil-rock interfaces and boundaries of SRMs.In the current research,the equivalent strength parameters of SRMs,i.e.the equivalent cohesion ce and internal friction angleϕ_(e),are determined using NMM.Initially,an NMM triaxial numerical model is established and validated based on triaxial experiments.Subsequently,the soil and rock parameters are derived through parameter inversion.Moreover,the impacts of rock content,size,shape and rock blocks'major-axis orientation on ce andϕ_(e) of SRMs are thoroughly examined using the NMM triaxial numerical model.Additionally,a fitting function is proposed to linkϕ_(e) to the rock content and size of SRMs.When other influencing factors are fixed,the above fitting model leads to the following conclusions:(1)the predictedϕ_(e) of SRMs increase with the increase of rock content;and(2)SRM samples with smaller rocks display a higher predictedϕ_(e).
文摘Objective:To explore the therapeutic effect of double-puncture tympanic membrane puncture and tympanic cavity drug injection in patients with acute secretory otitis media.Methods:A total of 84 patients with acute secretory otitis media admitted to our hospital from June 2024 to June 2025 were selected and randomly divided into two groups by drawing lots.The control group(42 cases)was treated with the traditional single-puncture tympanic membrane puncture and tympanic cavity drug injection method,while the observation group(42 cases)was treated with the double-puncture tympanic membrane puncture and tympanic cavity drug injection method.The therapeutic effects of the two groups were compared.Results:The overall treatment response rate,overall complication rate,time to symptom relief,and improvement in hearing threshold in the observation group were all superior to those in the control group,with statistically significant differences(P<0.05).Conclusion:For acute secretory otitis media,the treatment method of double-puncture tympanic membrane puncture and tympanic cavity drug injection demonstrates definite efficacy,significantly reducing the incidence of complications,accelerating symptom relief,and improving hearing function,making it worthy of promotion.
文摘Hydraulic fracturing serves as a critical technology for reservoir stimulation in deep coalbed methane(CBM)development,where the mechanical properties of gangue layers exert a significant control on fracture propagation behavior.To address the unclear mechanisms governing fracture penetration across coal-gangue interfaces,this study employs the Continuum-Discontinuum Element Method(CDEM)to simulate and analyze the vertical propagation of hydraulic fractures initiating within coal seams,based on geomechanical parameters derived from the deep Benxi Formation coal seams in the southeastern Ordos Basin.The investigation systematically examines the influence of geological and operational parameters on cross-interfacial fracture growth.Results demonstrate that vertical stress difference,elastic modulus contrast between coal and gangue layers,interfacial stress differential,and interfacial cohesion at coal-gangue interfaces are critical factors governing hydraulic fracture penetration through these interfaces.High vertical stress differences(>3 MPa)inhibit interfacial dilation,promoting predominant crosslayer fracture propagation.Reduced interfacial stress contrasts and enhanced interfacial cohesion facilitate fracture penetration across interfaces.Furthermore,smaller elastic modulus contrasts between coal and gangue correlate with increased interfacial aperture.Finally,lower injection rates effectively suppress vertical fracture propagation in deep coal reservoirs.This study elucidates the characteristics and mechanisms governing cross-layer fracture propagation in coal–rock composites with interbedded partings,and delineates the dynamic evolution laws and dominant controlling factors involved.Thefindings provide critical theoretical insights for the optimization of fracture design and the efficient development of deep coalbed methane reservoirs.
基金Supported by the National Natural Science Foundation of China under Grant No.51975138the High-Tech Ship Scientific Research Project from the Ministry of Industry and Information Technology under Grant No.CJ05N20the National Defense Basic Research Project under Grant No.JCKY2023604C006.
文摘Marine thin plates are susceptible to welding deformation owing to their low structural stiffness.Therefore,the efficient and accurate prediction of welding deformation is essential for improving welding quality.The traditional thermal elastic-plastic finite element method(TEP-FEM)can accurately predict welding deformation.However,its efficiency is low because of the complex nonlinear transient computation,making it difficult to meet the needs of rapid engineering evaluation.To address this challenge,this study proposes an efficient prediction method for welding deformation in marine thin plate butt welds.This method is based on the coupled temperature gradient-thermal strain method(TG-TSM)that integrates inherent strain theory with a shell element finite element model.The proposed method first extracts the distribution pattern and characteristic value of welding-induced inherent strain through TEP-FEM analysis.This strain is then converted into the equivalent thermal load applied to the shell element model for rapid computation.The proposed method-particularly,the gradual temperature gradient-thermal strain method(GTG-TSM)-achieved improved computational efficiency and consistent precision.Furthermore,the proposed method required much less computation time than the traditional TEP-FEM.Thus,this study lays the foundation for future prediction of welding deformation in more complex marine thin plates.
基金supported by Supported by the Scientific Research Foundation for High-Level Talents of Zhoukou Normal University(ZKNUC2024018).
文摘Energy shortage has become one of themost concerning issues in the world today,and improving energy utilization efficiency is a key area of research for experts and scholars worldwide.Small-diameter heat exchangers offer advantages such as reduced material usage,lower refrigerant charge,and compact structure.However,they also face challenges,including increased refrigerant pressure drop and smaller heat transfer area inside the tubes.This paper combines the advantages and disadvantages of both small and large-diameter tubes and proposes a combined-diameter heat exchanger,consisting of large and small diameters,for use in the indoor units of split-type air conditioners.There are relatively few studies in this area.In this paper,A theoretical and numerical computation method is employed to establish a theoretical-numerical calculation model,and its reliability is verified through experiments.Using this model,the optimal combined diameters and flow path design for a combined-diameter heat exchanger using R32 as the working fluid are derived.The results show that the heat transfer performance of all combined diameter configurations improves by 2.79%to 8.26%compared to the baseline design,with the coefficient of performance(COP)increasing from 4.15 to 4.27~4.5.These designs can save copper material,but at the cost of an increase in pressure drop by 66.86%to 131.84%.The scheme IIIH,using R32,is the optimal combined-diameter and flow path configuration that balances both heat transfer performance and economic cost.
基金The authors acknowledge the financial support from the Natural Science Foundation of China(U1704131)Program for Science&Technology Innovation Talents in Universities of Henan Province(18HASTIT018)the Program for Changjiang Scholars and Innovative Research Team in University(IRT_16R22).
文摘Improving the absorbed gas to active desorption and seepage and delaying gas drainage attenuation are considered as key methods for increasing drainage efficiency and gas output.According to the solid mechanics theory,the nonlinear Darcy seepage theory and thermodynamics,the heat-fluid-solid coupling model for gassy coal has been improved.The numerical model was founded from the improved multi-field coupling model by COMSOL Multiphysics and gas drainage by borehole down the coal seam enhanced by heat injection was modelled.The results show that the heatfluid-solid model with adsorption effects for gassy coal was well simulated by the improved multi-field model.The mechanism of coal seam gas desorption seepage under the combined action of temperature,stress and adsorption can be well described.Gas desorption and seepage can be enhanced by heat injection into coal seams.The gas drainage rate was directly proportional to the temperature of injected heat in the scope of 30-150 ℃ and increasing in the whole modelleddrainage process (0-1000 d).The increased level was maximum in the initial drainage time and decreasing gradually along with drainage time.The increasing ratio of drainage rate was maximum when the temperature raised from 30 to 60 ℃.Although the drainage rate would increase along with increasing temperature,when exceeding 60 ℃,the increasing ratio of drainage rate with rising temperature would decrease.Gas drainage promotion was more effective in coal seams with lower permeability than with higher permeability.The coal seam temperature in a 5 m distance surrounding the heat injection borehole would rise to around 60 ℃ in 3 months.That was much less than the time of gas drainage in the coal mines in sites with low permeability coal seams.Therefore,it is valuable and feasible to inject heat into coal seams to promote gas drainage,and this has strong feasibility for coal seams with low permeability which are widespread in China.
基金financially supported by the National Natural Science Foundation of China(No.41330638)
文摘The technology used to enhance coalbed methane(CBM) recovery by injecting CO_2(CO_2-ECBM) with heat, combining heat injection with CO_2 injection, is still in its infancy; therefore, theoretical studies of this CO_2-ECBM technology should be perused. First, the coupling equations of the di usion–adsorption–seepage–heat transfer fields of gas are established. The displacement processes under di erent pressures and temperatures are simulated by COMSOL. Finally, the displacement effects, a comparison of the CO_2 storage capacity with the CH_4 output and the e ective influencing radius of CO_2 injection are analyzed and discussed. The results show that(1) the displacement pressure and temperature are two key factors influencing the CH_4 output and the CO_2 storage capacity, and the increase in the CO_2 storage capacity is more sensitive to temperature and pressure than the CH_4 output.(2) The gas flow direction is from the injection hole to the discharge hole during the displacement process, and the regions with high velocity are concentrated at the injection hole and the discharge hole.(3) A reduction in the CH_4 concentration and an increase in the CO_2 concentration are obvious during the displacement process.(4) The e ective influencing radius of injecting CO_2 with heat increases with the increase in time and pressure. The relationship between the e ective influencing radius and the injection time of CO_2 has a power exponential function, and there is a linear relationship between the functional coe cient and the injection pressure of CO_2. This numerical simulation study on enhancing CBM recovery by injecting CO_2 with heat can further promote the implementation of CO_2-ECBM project in deep coal seams.
基金Project(ZI648/13-1) supported by German Research FoundationProject(D/06/00373) supported by German Academic Exchange Service
文摘In order to reduce the "trial-mold" risk and cost,numerical simulation method was applied to micro injection molding weld line development investigation. The micro tensile specimen which has the size of 0.1 mm(depth) ×0.4 mm(width) ×12 mm(length) in test area was selected as the objective part,and polypropylene(PP) as the experimental material. Respectively with specific commercial software(Mold Flow) and general computational fluid dynamic(CFD) software(Comsol Multiphysics) ,the simulation experiments for development of weld line in micro injection molding process were executed and the real comparison experiments were also carried out. The results show that during micro injection molding process,the specific commercial software for normal injection molding process is not valid to describe the micro flow process,the shape of flow front in micro cavity flowing which is important in weld line developing study and the contact angle due to surface tension are not able to be simulated. In order to improve the simulation results for micro weld line development,the general CFD software,which is more flexible in user defining function,is applied. The results show better effects in describing micro fluid flow behavior. As a conclusion,as for weld line forming process,the numerical simulation method can give a characteristic analysis results for processing parameters optimizing in micro injection molding process;but for both kinds of softwares quantitative analysis cannot be obtained unless the boundary condition and micro fluid mathematic model are improved in the future.
基金supported by the National Natural Science Foundation of China(NSFC)(Grant Nos.42377156,42077251 and 42202305).
文摘Deep shale reservoirs are characterized by elevated breakdown pressures,diminished fracture complexity,and reduced modified volumes compared to medium and shallow reservoirs.Therefore,it is urgent to investigate particular injection strategies that can optimize breakdown pressure and fracturing efficiency to address the increasing demands for deep shale reservoir stimulation.In this study,the efficiency of various stimulation strategies,including multi-cluster simultaneous fracturing,modified alternating fracturing,alternating shut-in fracturing,and cyclic alternating fracturing,was evaluated.Subsequently,the sensitivity of factors such as the cycle index,shut-in time,cluster spacing,and horizontal permeability was investigated.Additionally,the flow distribution effect within the wellbore was discussed.The results indicate that relative to multi-cluster simultaneous fracturing,modified alternating fracturing exhibits reduced susceptibility to the stress shadow effect,which results in earlier breakdown,extended hydraulic fracture lengths,and more consistent propagation despite an increase in breakdown pressure.The alternating shut-in fracturing benefits the increase of fracture length,which is closely related to the shut-in time.Furthermore,cyclic alternating fracturing markedly lowers breakdown pressure and contributes to uniform fracture propagation,in which the cycle count plays an important role.Modified alternating fracturing demonstrates insensitivity to variations in cluster spacing,whereas horizontal permeability is a critical factor affecting fracture length.The wellbore effect restrains the accumulation of pressure and flow near the perforation,delaying the initiation of hydraulic fractures.The simulation results can provide valuable numerical insights for optimizing injection strategies for deep shale hydraulic fracturing.
