BACKGROUND Non-operative spinal infections(NOSI)are caused by tuberculosis,brucella,and other specific bacteria.The etiology of the disease is insidious,the onset is slow and the diagnosis and treatment are difficult....BACKGROUND Non-operative spinal infections(NOSI)are caused by tuberculosis,brucella,and other specific bacteria.The etiology of the disease is insidious,the onset is slow and the diagnosis and treatment are difficult.Identifying the factors associated with spinal infection and early intervention can reduce the occurrence of the disease.At present,the research mainly focuses on the accurate diagnosis and treatment of spinal infection,and there are few studies on the prevention of spinal infection.The concept of"preventive treatment of diseases"in traditional Chinese medicine may help identify the causes and reduce the occurrence of NOSI.AIM To determine the association of age,bowel movements,and sleep patterns with NOSI.METHODS Data of 69 NOSI patients and 84 healthy controls in a tertiary hospital from January 2019 to June 2024 were collected.Patients with NOSI had imaging evidence(magnetic resonance imaging)of spinal infections(including infections caused by tuberculosis,brucopathy,and other pathogens)and had no history of spinal surgery in the last 1 year were included in the analysis.Patients with spinalinfection due to spinal surgery are excluded in the study.Data including age,sex,place of residence,sleeping status,and bowel movements were collected.SPSS22.0 was used for correlation analysis of all data.RESULTS The mean age of the NOSI group and the control group was 63.55±14.635 years and 59.18±17.111 years,respectively,without statistical difference(P=0.096).There was also no statistically significant difference in gender between the two groups.In the NOSI group,45(65.22%)were over 60 years old,and 44(63.77%)were rural residents.Compared with the control group,the NOSI group had more patients with sleep disorder and defecation disorder,accounting for 69.57%and 68.12%,respectively,with significant statistical difference(both P<0.001).Regression analysis showed that defecation and sleep disorders were closely related to NOSI(both P<0.001).CONCLUSION Most patients with NOSI are older and have sleep disorders and abnormal defecation.展开更多
BACKGROUND Non-operative management(NOM)for uncomplicated acute appendicitis(AA)has been gaining popularity in recent years.One of the major concerns with NOM is the recurrence rate of AA following NOM.AIM To investig...BACKGROUND Non-operative management(NOM)for uncomplicated acute appendicitis(AA)has been gaining popularity in recent years.One of the major concerns with NOM is the recurrence rate of AA following NOM.AIM To investigate the impact of the presence of an appendicolith and its specific characteristics on the recurrence rate of AA following NOM.METHODS A retrospective analysis identified all patients treated with NOM for AA,at our institute between 2016 and 2024.Patients with an appendicolith on imaging were identified and their course and outcomes were compared with patients who were treated with NOM without an appendicolith.The primary outcome was defined as a recurrence of AA.RESULTS During the study period,797 patients were treated with NOM for AA.Their mean age was 25.4 years±14.4 years,and 45.4%were females.Only 68 patients(8.5%)had an appendicolith identified on imaging.Patients with an appendicolith had a larger appendix diameter(10.2 mm±4 mm vs 8.5 mm±2.1 mm,P=0.001).There was no difference in the recurrence rate of patients with and without an appendicolith(26.5%vs 19.1%,P=0.14),however patients with an appendicolith presented with a shorter time to recurrence of appendicitis(3.9 months±10.4 months vs 5.9 months±8.1 months,P=0.04).In a sub analysis,the number of appendicoliths,its size,and its location,did not influence the recurrence rate.CONCLUSION This study demonstrates that patients with appendicoliths have a shorter time to recurrence after NOM of AA,but do not experience higher overall recurrence rates.展开更多
In this paper,we consider the maximal positive definite solution of the nonlinear matrix equation.By using the idea of Algorithm 2.1 in ZHANG(2013),a new inversion-free method with a stepsize parameter is proposed to ...In this paper,we consider the maximal positive definite solution of the nonlinear matrix equation.By using the idea of Algorithm 2.1 in ZHANG(2013),a new inversion-free method with a stepsize parameter is proposed to obtain the maximal positive definite solution of nonlinear matrix equation X+A^(*)X|^(-α)A=Q with the case 0<α≤1.Based on this method,a new iterative algorithm is developed,and its convergence proof is given.Finally,two numerical examples are provided to show the effectiveness of the proposed method.展开更多
In this paper,a novel method for investigating the particle-crushing behavior of breeding particles in a fusion blanket is proposed.The fractal theory and Weibull distribution are combined to establish a theoretical m...In this paper,a novel method for investigating the particle-crushing behavior of breeding particles in a fusion blanket is proposed.The fractal theory and Weibull distribution are combined to establish a theoretical model,and its validity was verified using a simple impact test.A crushable discrete element method(DEM)framework is built based on the previously established theoretical model.The tensile strength,which considers the fractal theory,size effect,and Weibull variation,was assigned to each generated particle.The assigned strength is then used for crush detection by comparing it with its maximum tensile stress.Mass conservation is ensured by inserting a series of sub-particles whose total mass was equal to the quality loss.Based on the crushable DEM framework,a numerical simulation of the crushing behavior of a pebble bed with hollow cylindrical geometry under a uniaxial compression test was performed.The results of this investigation showed that the particle withstands the external load by contact and sliding at the beginning of the compression process,and the results confirmed that crushing can be considered an important method of resisting the increasing external load.A relatively regular particle arrangement aids in resisting the load and reduces the occurrence of particle crushing.However,a limit exists to the promotion of resistance.When the strain increases beyond this limit,the distribution of the crushing position tends to be isotropic over the entire pebble bed.The theoretical model and crushable DEM framework provide a new method for exploring the pebble bed in a fusion reactor,considering particle crushing.展开更多
Effective partitioning is crucial for enabling parallel restoration of power systems after blackouts.This paper proposes a novel partitioning method based on deep reinforcement learning.First,the partitioning decision...Effective partitioning is crucial for enabling parallel restoration of power systems after blackouts.This paper proposes a novel partitioning method based on deep reinforcement learning.First,the partitioning decision process is formulated as a Markov decision process(MDP)model to maximize the modularity.Corresponding key partitioning constraints on parallel restoration are considered.Second,based on the partitioning objective and constraints,the reward function of the partitioning MDP model is set by adopting a relative deviation normalization scheme to reduce mutual interference between the reward and penalty in the reward function.The soft bonus scaling mechanism is introduced to mitigate overestimation caused by abrupt jumps in the reward.Then,the deep Q network method is applied to solve the partitioning MDP model and generate partitioning schemes.Two experience replay buffers are employed to speed up the training process of the method.Finally,case studies on the IEEE 39-bus test system demonstrate that the proposed method can generate a high-modularity partitioning result that meets all key partitioning constraints,thereby improving the parallelism and reliability of the restoration process.Moreover,simulation results demonstrate that an appropriate discount factor is crucial for ensuring both the convergence speed and the stability of the partitioning training.展开更多
The application of nitrogen fertilizers in agricultural fields can lead to the release of nitrogen-containing gases(NCGs),such as NO_(x),NH_(3) and N_(2)O,which can significantly impact regional atmospheric environmen...The application of nitrogen fertilizers in agricultural fields can lead to the release of nitrogen-containing gases(NCGs),such as NO_(x),NH_(3) and N_(2)O,which can significantly impact regional atmospheric environment and con-tribute to global climate change.However,there remain considerable research gaps in the accurate measurement of NCGs emissions from agricultural fields,hindering the development of effective emission reduction strategies.We improved an open-top dynamic chambers(OTDCs)system and evaluated the performance by comparing the measured and given fluxes of the NCGs.The results showed that the measured fluxes of NO,N_(2)O and NH_(3)were 1%,2%and 7%lower than the given fluxes,respectively.For the determination of NH_(3) concentration,we employed a stripping coil-ion chromatograph(SC-IC)analytical technique,which demonstrated an absorption efficiency for atmospheric NH_(3) exceeding 96.1%across sampling durations of 6 to 60 min.In the summer maize season,we utilized the OTDCs system to measure the exchange fluxes of NO,NH_(3),and N_(2)O from the soil in the North China Plain.Substantial emissions of NO,NH_(3) and N_(2)O were recorded following fertilization,with peaks of 107,309,1239 ng N/(m^(2)·s),respectively.Notably,significant NCGs emissions were observed following sus-tained heavy rainfall one month after fertilization,particularly with NH_(3) peak being 4.5 times higher than that observed immediately after fertilization.Our results demonstrate that the OTDCs system accurately reflects the emission characteristics of soil NCGs and meets the requirements for long-term and continuous flux observation.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
At present,there is currently a lack of unified standard methods for the determination of antimony content in groundwater in China.The precision and trueness of related detection technologies have not yet been systema...At present,there is currently a lack of unified standard methods for the determination of antimony content in groundwater in China.The precision and trueness of related detection technologies have not yet been systematically and quantitatively evaluated,which limits the effective implementation of environmental monitoring.In response to this key technical gap,this study aimed to establish a standardized method for determining antimony in groundwater using Hydride Generation–Atomic Fluorescence Spectrometry(HG-AFS).Ten laboratories participated in inter-laboratory collaborative tests,and the statistical analysis of the test data was carried out in strict accordance with the technical specifications of GB/T 6379.2—2004 and GB/T 6379.4—2006.The consistency and outliers of the data were tested by Mandel's h and k statistics,the Grubbs test and the Cochran test,and the outliers were removed to optimize the data,thereby significantly improving the reliability and accuracy.Based on the optimized data,parameters such as the repeatability limit(r),reproducibility limit(R),and method bias value(δ)were determined,and the trueness of the method was statistically evaluated.At the same time,precision-function relationships were established,and all results met the requirements.The results show that the lower the antimony content,the lower the repeatability limit(r)and reproducibility limit(R),indicating that the measurement error mainly originates from the detection limit of the method and instrument sensitivity.Therefore,improving the instrument sensitivity and reducing the detection limit are the keys to controlling the analytical error and improving precision.This study provides reliable data support and a solid technical foundation for the establishment and evaluation of standardized methods for the determination of antimony content in groundwater.展开更多
AIM: To perform a systematic review and meta-analysis comparing operative vs non-operative treatment of displaced proximal humerus fractures in elderly patients.METHODS: A systematic literature search was performed us...AIM: To perform a systematic review and meta-analysis comparing operative vs non-operative treatment of displaced proximal humerus fractures in elderly patients.METHODS: A systematic literature search was performed using EMBASE and MEDLINE through the OVID interface,CINAHL,the Cochrane Central Register of Controlled Trials(CENTRAL),Proquest,Web of Science,SAE digital library,and Transportation Research Board's TRID database.Searches of conference proceedings were also conducted.All available randomized controlled trials comparing operative vs non-operative management of displaced three- and four-part proximal humerus fractures in elderly patients were included.The primary outcomes measures included physical function,pain,health related quality of life,mortality,and the re-operation rate.RESULTS: Six randomized controlled trials(n = 287) were included.There was no statistically significant difference in function(MD = 1.72,95%CI:-2.90-6.34,P = 0.47),as measured by the Constant score,between the operative and the non-operative treatment groups.There was no statistically significance difference insecondary outcomes of health related quality of life(standardized MD = 0.27,95%CI:-0.05-0.59,P = 0.09),and mortality(relative risk 1.29,95%CI: 0.50-3.35,P = 0.60).Operative treatment had a statistically significant higher re-operation rate(relative risk 4.09,95%CI: 1.50-11.15,P = 0.006),and statistically significant decreased pain(MD = 1.26,95%CI: 0.02-2.49,P = 0.05).CONCLUSION: There is moderate quality evidence to suggest that there is no difference in functional outcomes between the two treatments.Further high quality randomized controlled trials are required to determine if certain subgroup populations benefit from surgical management.展开更多
Liver trauma is the most common abdominal emergency with high morbidity and mortality. Now, nonoperative management（NOM） is a selective method for liver trauma. The aim of this study was to determine the success rat...Liver trauma is the most common abdominal emergency with high morbidity and mortality. Now, nonoperative management（NOM） is a selective method for liver trauma. The aim of this study was to determine the success rate, mortality and morbidity of NOM for isolated liver trauma.Medical records of 81 patients with isolated liver trauma in our unit were analyzed retrospectively. The success rate, mortality and morbidity of NOM were evaluated. In this series, 9 patients with grade IV-V liver injuries underwent emergent operation due to hemodynamic instability; 72 patients, 6 with grade V, 18 grade IV, 29 grade III, 15 grade II and 4 grade I, with hemodynamic stability received NOM. The overall success rate of NOM was 97.2%（70/72）. The success rates of NOM in the patients with grade I-III, IV and V liver trauma were100%, 94.4% and 83.3%. The complication rates were 10.0%and 45.5% in the patients who underwent NOM and surgical treatment, respectively. No patient with grade I-II liver trauma had complications. All patients who underwent NOM survived.NOM is the first option for the treatment of liver trauma if the patient is hemodynamically stable. The grade of liver injury and the volume of hemoperitoneum are not suitable criteria for selecting NOM. Hepatic angioembolization associated with the correction of hypothermia, coagulopathy and acidosis is important in the conservative treatment for liver trauma.展开更多
There remains much ambiguity on what non-operative management(NOM)of rectal cancer truly entails in terms of the methods to be adopted and the best algorithm to follow.This is clearly shown by the discordance between ...There remains much ambiguity on what non-operative management(NOM)of rectal cancer truly entails in terms of the methods to be adopted and the best algorithm to follow.This is clearly shown by the discordance between various national and international guidelines on NOM of rectal cancer.The main aim of the NOM strategy is organ preservation and avoiding unnecessary surgical in-tervention,which carries its own risk of morbidity.A highly specific and sensitive surveillance program must be devised to avoid patients undergoing unnecessary surgical interventions.In many studies,NOM,often interchangeably called the Watch and Wait strategy,has been shown as a promising treatment option when undertaken in the appropriate patient population,where a clinical complete res-ponse is achieved.However,there are no clear guidelines on patient selection for NOM along with the optimal method of surveillance.展开更多
BACKGROUND Majority of adhesive small bowel obstruction(SBO)cases can be managed nonoperatively.However,a proportion of patients failed non-operative management.AIM To evaluate the predictors of successful non-operati...BACKGROUND Majority of adhesive small bowel obstruction(SBO)cases can be managed nonoperatively.However,a proportion of patients failed non-operative management.AIM To evaluate the predictors of successful non-operative management in adhesive SBO.METHODS A retrospective study was performed for all consecutive cases of adhesive SBO from November 2015 to May 2018.Data collated included basic demographics,clinical presentation,biochemistry and imaging results and management outcomes.The imaging studies were independently analyzed by a radiologist who was blinded to the clinical outcomes.The patients were divided into group A operative(including those that failed initial non-operative management)and group B non-operative for analysis.RESULTS Of 252 patients were included in the final analysis;group A(n=90)(35.7%)and group B(n=162)(64.3%).There were no differences in the clinical features between both groups.Laboratory tests of inflammatory markers and lactate levels were similar in both groups.From the imaging findings,the presence of a definitive transition point[odds ratio(OR)=2.67,95%confidence interval(CI):0.98-7.32,P=0.048],presence of free fluid(OR=2.11,95%CI:1.15-3.89,P=0.015)and absence of small bowel faecal signs(OR=1.70,95%CI:1.01-2.88,P=0.047)were predictive of the need of surgical intervention.In patients that received water soluble contrast medium,the evidence of contrast in colon was 3.83 times predictive of successful non-operative management(95%CI:1.79-8.21,P=0.001).CONCLUSION The computed tomography findings can assist clinicians in deciding early surgical intervention in adhesive SBO cases that are unlikely to be successful with non-operative management to prevent associated morbidity and mortality.展开更多
Introduction: results after non-operative management for knees sustaining combined acute anterior and posterior cruciate ligament tears were presented. Subjects: 13 patients, 10 with medial, and 3 with lateral ligamen...Introduction: results after non-operative management for knees sustaining combined acute anterior and posterior cruciate ligament tears were presented. Subjects: 13 patients, 10 with medial, and 3 with lateral ligament injury. Methods: non-operative management consisted of employing a brace to prevent sagittal translation of the tibia. Quadriceps muscle and early passive knee motion exercises in the brace was encouraged immediately after arthroscopy. Weight-bearing was forbidden for 3 weeks. The brace was not removed for 3 months. Follow-up periods ranged from 2 to 6 years (mean, 3 years 2 months). Results: none, but one patient had a slight restriction of knee flexion. Quadriceps muscle strength revealed an average of 89.0% of normal side. The knee score indicated 2 patients rated good, 3 rated fair, and 8 rated poor. The score correlated with measurements of anterior and posterior translation on the stress radiograph significantly. Stress radiography revealed that anterior laxity was reduced better than posterior laxity significantly. Conclusion: non-operative brace therapy can be considered for this combined injury as the initial treatment. A late reconstruction would be performed when the result was not satisfactory. Preserved range of motion and muscle strength after brace therapy had a great advantage to the late reconstructive surgery.展开更多
Modal parameters can accurately characterize the structural dynamic properties and assess the physical state of the structure.Therefore,it is particularly significant to identify the structural modal parameters accordi...Modal parameters can accurately characterize the structural dynamic properties and assess the physical state of the structure.Therefore,it is particularly significant to identify the structural modal parameters according to the monitoring data information in the structural health monitoring(SHM)system,so as to provide a scientific basis for structural damage identification and dynamic model modification.In view of this,this paper reviews methods for identifying structural modal parameters under environmental excitation and briefly describes how to identify structural damages based on the derived modal parameters.The paper primarily introduces data-driven modal parameter recognition methods(e.g.,time-domain,frequency-domain,and time-frequency-domain methods,etc.),briefly describes damage identification methods based on the variations of modal parameters(e.g.,natural frequency,modal shapes,and curvature modal shapes,etc.)and modal validation methods(e.g.,Stability Diagram and Modal Assurance Criterion,etc.).The current status of the application of artificial intelligence(AI)methods in the direction of modal parameter recognition and damage identification is further discussed.Based on the pre-vious analysis,the main development trends of structural modal parameter recognition and damage identification methods are given to provide scientific references for the optimized design and functional upgrading of SHM systems.展开更多
To analyze the differences in the transport and distribution of different types of proppants and to address issues such as the short effective support of proppant and poor placement in hydraulically intersecting fract...To analyze the differences in the transport and distribution of different types of proppants and to address issues such as the short effective support of proppant and poor placement in hydraulically intersecting fractures,this study considered the combined impact of geological-engineering factors on conductivity.Using reservoir production parameters and the discrete elementmethod,multispherical proppants were constructed.Additionally,a 3D fracture model,based on the specified conditions of the L block,employed coupled(Computational Fluid Dynamics)CFD-DEM(Discrete ElementMethod)for joint simulations to quantitatively analyze the transport and placement patterns of multispherical proppants in intersecting fractures.Results indicate that turbulent kinetic energy is an intrinsic factor affecting proppant transport.Moreover,the efficiency of placement and migration distance of low-sphericity quartz sand constructed by the DEM in the main fracture are significantly reduced compared to spherical ceramic proppants,with a 27.7%decrease in the volume fraction of the fracture surface,subsequently affecting the placement concentration and damaging fracture conductivity.Compared to small-angle fractures,controlling artificial and natural fractures to expand at angles of 45°to 60°increases the effective support length by approximately 20.6%.During hydraulic fracturing of gas wells,ensuring the fracture support area and post-closure conductivity can be achieved by controlling the sphericity of proppants and adjusting the perforation direction to control the direction of artificial fractures.展开更多
Objective: the indications and clinical effects of non-surgical treatment for 49 cases of traumatic splenic rupture were analyzed and summarized. Methods: the clinical data of 49 patients with traumatic splenic ruptur...Objective: the indications and clinical effects of non-surgical treatment for 49 cases of traumatic splenic rupture were analyzed and summarized. Methods: the clinical data of 49 patients with traumatic splenic rupture admitted to our hospital from January 2006 to December 2015 were retrospectively analyzed. Results: all cases were graded according to the degree of injury. 45 cases were cured successfully (91.84%) after non-operative treatment. 4 cases (8.16%) were converted to surgical treatment during the course of conservative treatment, and there was no death. Conclusion: traumatic splenic rupture is very dangerous and changeable. Non-operative and surgical indications should be reasonably grasped according to the grade of splenic injury and the change of disease condition.展开更多
This study investigated the physicochemical properties,enzyme activities,volatile flavor components,microbial communities,and sensory evaluation of high-temperature Daqu(HTD)during the maturation process,and a standar...This study investigated the physicochemical properties,enzyme activities,volatile flavor components,microbial communities,and sensory evaluation of high-temperature Daqu(HTD)during the maturation process,and a standard system was established for comprehensive quality evaluation of HTD.There were obvious changes in the physicochemical properties,enzyme activities,and volatile flavor components at different storage periods,which affected the sensory evaluation of HTD to a certain extent.The results of high-throughput sequencing revealed significant microbial diversity,and showed that the bacterial community changed significantly more than did the fungal community.During the storage process,the dominant bacterial genera were Kroppenstedtia and Thermoascus.The correlation between dominant microorganisms and quality indicators highlighted their role in HTD quality.Lactococcus,Candida,Pichia,Paecilomyces,and protease activity played a crucial role in the formation of isovaleraldehyde.Acidic protease activity had the greatest impact on the microbial community.Moisture promoted isobutyric acid generation.Furthermore,the comprehensive quality evaluation standard system was established by the entropy weight method combined with multi-factor fuzzy mathematics.Consequently,this study provides innovative insights for comprehensive quality evaluation of HTD during storage and establishes a groundwork for scientific and rational storage of HTD and quality control of sauce-flavor Baijiu.展开更多
Due to the heterogeneity of rock masses and the variability of in situ stress,the traditional linear inversion method is insufficiently accurate to achieve high accuracy of the in situ stress field.To address this cha...Due to the heterogeneity of rock masses and the variability of in situ stress,the traditional linear inversion method is insufficiently accurate to achieve high accuracy of the in situ stress field.To address this challenge,nonlinear stress boundaries for a numerical model are determined through regression analysis of a series of nonlinear coefficient matrices,which are derived from the bubbling method.Considering the randomness and flexibility of the bubbling method,a parametric study is conducted to determine recommended ranges for these parameters,including the standard deviation(σb)of bubble radii,the non-uniform coefficient matrix number(λ)for nonlinear stress boundaries,and the number(m)and positions of in situ stress measurement points.A model case study provides a reference for the selection of these parameters.Additionally,when the nonlinear in situ stress inversion method is employed,stress distortion inevitably occurs near model boundaries,aligning with the Saint Venant's principle.Two strategies are proposed accordingly:employing a systematic reduction of nonlinear coefficients to achieve high inversion accuracy while minimizing significant stress distortion,and excluding regions with severe stress distortion near the model edges while utilizing the central part of the model for subsequent simulations.These two strategies have been successfully implemented in the nonlinear in situ stress inversion of the Xincheng Gold Mine and have achieved higher inversion accuracy than the linear method.Specifically,the linear and nonlinear inversion methods yield root mean square errors(RMSE)of 4.15 and 3.2,and inversion relative errors(δAve)of 22.08%and 17.55%,respectively.Therefore,the nonlinear inversion method outperforms the traditional multiple linear regression method,even in the presence of a systematic reduction in the nonlinear stress boundaries.展开更多
To address the problems of low accuracy by the CONWEP model and poor efficiency by the Coupled Eulerian-Lagrangian(CEL)method in predicting close-range air blast loads of cylindrical charges,a neural network-based sim...To address the problems of low accuracy by the CONWEP model and poor efficiency by the Coupled Eulerian-Lagrangian(CEL)method in predicting close-range air blast loads of cylindrical charges,a neural network-based simulation(NNS)method with higher accuracy and better efficiency was proposed.The NNS method consisted of three main steps.First,the parameters of blast loads,including the peak pressures and impulses of cylindrical charges with different aspect ratios(L/D)at different stand-off distances and incident angles were obtained by two-dimensional numerical simulations.Subsequently,incident shape factors of cylindrical charges with arbitrary aspect ratios were predicted by a neural network.Finally,reflected shape factors were derived and implemented into the subroutine of the ABAQUS code to modify the CONWEP model,including modifications of impulse and overpressure.The reliability of the proposed NNS method was verified by related experimental results.Remarkable accuracy improvement was acquired by the proposed NNS method compared with the unmodified CONWEP model.Moreover,huge efficiency superiority was obtained by the proposed NNS method compared with the CEL method.The proposed NNS method showed good accuracy when the scaled distance was greater than 0.2 m/kg^(1/3).It should be noted that there is no need to generate a new dataset again since the blast loads satisfy the similarity law,and the proposed NNS method can be directly used to simulate the blast loads generated by different cylindrical charges.The proposed NNS method with high efficiency and accuracy can be used as an effective method to analyze the dynamic response of structures under blast loads,and it has significant application prospects in designing protective structures.展开更多
The separation-of-variable(SOV)methods,such as the improved SOV method,the variational SOV method,and the extended SOV method,have been proposed by the present authors and coworkers to obtain the closed-form analytica...The separation-of-variable(SOV)methods,such as the improved SOV method,the variational SOV method,and the extended SOV method,have been proposed by the present authors and coworkers to obtain the closed-form analytical solutions for free vibration and eigenbuckling of rectangular plates and circular cylindrical shells.By taking the free vibration of rectangular thin plates as an example,this work presents the theoretical framework of the SOV methods in an instructive way,and the bisection–based solution procedures for a group of nonlinear eigenvalue equations.Besides,the explicit equations of nodal lines of the SOV methods are presented,and the relations of nodal line patterns and frequency orders are investigated.It is concluded that the highly accurate SOV methods have the same accuracy for all frequencies,the mode shapes about repeated frequencies can also be precisely captured,and the SOV methods do not have the problem of missing roots as well.展开更多
文摘BACKGROUND Non-operative spinal infections(NOSI)are caused by tuberculosis,brucella,and other specific bacteria.The etiology of the disease is insidious,the onset is slow and the diagnosis and treatment are difficult.Identifying the factors associated with spinal infection and early intervention can reduce the occurrence of the disease.At present,the research mainly focuses on the accurate diagnosis and treatment of spinal infection,and there are few studies on the prevention of spinal infection.The concept of"preventive treatment of diseases"in traditional Chinese medicine may help identify the causes and reduce the occurrence of NOSI.AIM To determine the association of age,bowel movements,and sleep patterns with NOSI.METHODS Data of 69 NOSI patients and 84 healthy controls in a tertiary hospital from January 2019 to June 2024 were collected.Patients with NOSI had imaging evidence(magnetic resonance imaging)of spinal infections(including infections caused by tuberculosis,brucopathy,and other pathogens)and had no history of spinal surgery in the last 1 year were included in the analysis.Patients with spinalinfection due to spinal surgery are excluded in the study.Data including age,sex,place of residence,sleeping status,and bowel movements were collected.SPSS22.0 was used for correlation analysis of all data.RESULTS The mean age of the NOSI group and the control group was 63.55±14.635 years and 59.18±17.111 years,respectively,without statistical difference(P=0.096).There was also no statistically significant difference in gender between the two groups.In the NOSI group,45(65.22%)were over 60 years old,and 44(63.77%)were rural residents.Compared with the control group,the NOSI group had more patients with sleep disorder and defecation disorder,accounting for 69.57%and 68.12%,respectively,with significant statistical difference(both P<0.001).Regression analysis showed that defecation and sleep disorders were closely related to NOSI(both P<0.001).CONCLUSION Most patients with NOSI are older and have sleep disorders and abnormal defecation.
文摘BACKGROUND Non-operative management(NOM)for uncomplicated acute appendicitis(AA)has been gaining popularity in recent years.One of the major concerns with NOM is the recurrence rate of AA following NOM.AIM To investigate the impact of the presence of an appendicolith and its specific characteristics on the recurrence rate of AA following NOM.METHODS A retrospective analysis identified all patients treated with NOM for AA,at our institute between 2016 and 2024.Patients with an appendicolith on imaging were identified and their course and outcomes were compared with patients who were treated with NOM without an appendicolith.The primary outcome was defined as a recurrence of AA.RESULTS During the study period,797 patients were treated with NOM for AA.Their mean age was 25.4 years±14.4 years,and 45.4%were females.Only 68 patients(8.5%)had an appendicolith identified on imaging.Patients with an appendicolith had a larger appendix diameter(10.2 mm±4 mm vs 8.5 mm±2.1 mm,P=0.001).There was no difference in the recurrence rate of patients with and without an appendicolith(26.5%vs 19.1%,P=0.14),however patients with an appendicolith presented with a shorter time to recurrence of appendicitis(3.9 months±10.4 months vs 5.9 months±8.1 months,P=0.04).In a sub analysis,the number of appendicoliths,its size,and its location,did not influence the recurrence rate.CONCLUSION This study demonstrates that patients with appendicoliths have a shorter time to recurrence after NOM of AA,but do not experience higher overall recurrence rates.
基金Supported in part by Natural Science Foundation of Guangxi(2023GXNSFAA026246)in part by the Central Government's Guide to Local Science and Technology Development Fund(GuikeZY23055044)in part by the National Natural Science Foundation of China(62363003)。
文摘In this paper,we consider the maximal positive definite solution of the nonlinear matrix equation.By using the idea of Algorithm 2.1 in ZHANG(2013),a new inversion-free method with a stepsize parameter is proposed to obtain the maximal positive definite solution of nonlinear matrix equation X+A^(*)X|^(-α)A=Q with the case 0<α≤1.Based on this method,a new iterative algorithm is developed,and its convergence proof is given.Finally,two numerical examples are provided to show the effectiveness of the proposed method.
基金supported by Anhui Provincial Natural Science Foundation(2408085QA030)Natural Science Research Project of Anhui Educational Committee,China(2022AH050825)+3 种基金Medical Special Cultivation Project of Anhui University of Science and Technology(YZ2023H2C008)the Excellent Research and Innovation Team of Anhui Province,China(2022AH010052)the Scientific Research Foundation for High-level Talents of Anhui University of Science and Technology,China(2021yjrc51)Collaborative Innovation Program of Hefei Science Center,CAS,China(2019HSC-CIP006).
文摘In this paper,a novel method for investigating the particle-crushing behavior of breeding particles in a fusion blanket is proposed.The fractal theory and Weibull distribution are combined to establish a theoretical model,and its validity was verified using a simple impact test.A crushable discrete element method(DEM)framework is built based on the previously established theoretical model.The tensile strength,which considers the fractal theory,size effect,and Weibull variation,was assigned to each generated particle.The assigned strength is then used for crush detection by comparing it with its maximum tensile stress.Mass conservation is ensured by inserting a series of sub-particles whose total mass was equal to the quality loss.Based on the crushable DEM framework,a numerical simulation of the crushing behavior of a pebble bed with hollow cylindrical geometry under a uniaxial compression test was performed.The results of this investigation showed that the particle withstands the external load by contact and sliding at the beginning of the compression process,and the results confirmed that crushing can be considered an important method of resisting the increasing external load.A relatively regular particle arrangement aids in resisting the load and reduces the occurrence of particle crushing.However,a limit exists to the promotion of resistance.When the strain increases beyond this limit,the distribution of the crushing position tends to be isotropic over the entire pebble bed.The theoretical model and crushable DEM framework provide a new method for exploring the pebble bed in a fusion reactor,considering particle crushing.
基金funded by the Beijing Engineering Research Center of Electric Rail Transportation.
文摘Effective partitioning is crucial for enabling parallel restoration of power systems after blackouts.This paper proposes a novel partitioning method based on deep reinforcement learning.First,the partitioning decision process is formulated as a Markov decision process(MDP)model to maximize the modularity.Corresponding key partitioning constraints on parallel restoration are considered.Second,based on the partitioning objective and constraints,the reward function of the partitioning MDP model is set by adopting a relative deviation normalization scheme to reduce mutual interference between the reward and penalty in the reward function.The soft bonus scaling mechanism is introduced to mitigate overestimation caused by abrupt jumps in the reward.Then,the deep Q network method is applied to solve the partitioning MDP model and generate partitioning schemes.Two experience replay buffers are employed to speed up the training process of the method.Finally,case studies on the IEEE 39-bus test system demonstrate that the proposed method can generate a high-modularity partitioning result that meets all key partitioning constraints,thereby improving the parallelism and reliability of the restoration process.Moreover,simulation results demonstrate that an appropriate discount factor is crucial for ensuring both the convergence speed and the stability of the partitioning training.
基金supported by the National Key Research and Develop-ment Program(No.2022YFC3701103)the National Natural Science Foundation of China(Nos.42130714 and 41931287).
文摘The application of nitrogen fertilizers in agricultural fields can lead to the release of nitrogen-containing gases(NCGs),such as NO_(x),NH_(3) and N_(2)O,which can significantly impact regional atmospheric environment and con-tribute to global climate change.However,there remain considerable research gaps in the accurate measurement of NCGs emissions from agricultural fields,hindering the development of effective emission reduction strategies.We improved an open-top dynamic chambers(OTDCs)system and evaluated the performance by comparing the measured and given fluxes of the NCGs.The results showed that the measured fluxes of NO,N_(2)O and NH_(3)were 1%,2%and 7%lower than the given fluxes,respectively.For the determination of NH_(3) concentration,we employed a stripping coil-ion chromatograph(SC-IC)analytical technique,which demonstrated an absorption efficiency for atmospheric NH_(3) exceeding 96.1%across sampling durations of 6 to 60 min.In the summer maize season,we utilized the OTDCs system to measure the exchange fluxes of NO,NH_(3),and N_(2)O from the soil in the North China Plain.Substantial emissions of NO,NH_(3) and N_(2)O were recorded following fertilization,with peaks of 107,309,1239 ng N/(m^(2)·s),respectively.Notably,significant NCGs emissions were observed following sus-tained heavy rainfall one month after fertilization,particularly with NH_(3) peak being 4.5 times higher than that observed immediately after fertilization.Our results demonstrate that the OTDCs system accurately reflects the emission characteristics of soil NCGs and meets the requirements for long-term and continuous flux observation.
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 the National Natural Science Foundation of China(Project No.42307555).
文摘At present,there is currently a lack of unified standard methods for the determination of antimony content in groundwater in China.The precision and trueness of related detection technologies have not yet been systematically and quantitatively evaluated,which limits the effective implementation of environmental monitoring.In response to this key technical gap,this study aimed to establish a standardized method for determining antimony in groundwater using Hydride Generation–Atomic Fluorescence Spectrometry(HG-AFS).Ten laboratories participated in inter-laboratory collaborative tests,and the statistical analysis of the test data was carried out in strict accordance with the technical specifications of GB/T 6379.2—2004 and GB/T 6379.4—2006.The consistency and outliers of the data were tested by Mandel's h and k statistics,the Grubbs test and the Cochran test,and the outliers were removed to optimize the data,thereby significantly improving the reliability and accuracy.Based on the optimized data,parameters such as the repeatability limit(r),reproducibility limit(R),and method bias value(δ)were determined,and the trueness of the method was statistically evaluated.At the same time,precision-function relationships were established,and all results met the requirements.The results show that the lower the antimony content,the lower the repeatability limit(r)and reproducibility limit(R),indicating that the measurement error mainly originates from the detection limit of the method and instrument sensitivity.Therefore,improving the instrument sensitivity and reducing the detection limit are the keys to controlling the analytical error and improving precision.This study provides reliable data support and a solid technical foundation for the establishment and evaluation of standardized methods for the determination of antimony content in groundwater.
基金Supported by In part by a Canada Research Chair to Dr.Bhandariin part by the Canadian Institutes of Health Research and Vancouver Coastal Health Research Institute to Dr.Slobogean
文摘AIM: To perform a systematic review and meta-analysis comparing operative vs non-operative treatment of displaced proximal humerus fractures in elderly patients.METHODS: A systematic literature search was performed using EMBASE and MEDLINE through the OVID interface,CINAHL,the Cochrane Central Register of Controlled Trials(CENTRAL),Proquest,Web of Science,SAE digital library,and Transportation Research Board's TRID database.Searches of conference proceedings were also conducted.All available randomized controlled trials comparing operative vs non-operative management of displaced three- and four-part proximal humerus fractures in elderly patients were included.The primary outcomes measures included physical function,pain,health related quality of life,mortality,and the re-operation rate.RESULTS: Six randomized controlled trials(n = 287) were included.There was no statistically significant difference in function(MD = 1.72,95%CI:-2.90-6.34,P = 0.47),as measured by the Constant score,between the operative and the non-operative treatment groups.There was no statistically significance difference insecondary outcomes of health related quality of life(standardized MD = 0.27,95%CI:-0.05-0.59,P = 0.09),and mortality(relative risk 1.29,95%CI: 0.50-3.35,P = 0.60).Operative treatment had a statistically significant higher re-operation rate(relative risk 4.09,95%CI: 1.50-11.15,P = 0.006),and statistically significant decreased pain(MD = 1.26,95%CI: 0.02-2.49,P = 0.05).CONCLUSION: There is moderate quality evidence to suggest that there is no difference in functional outcomes between the two treatments.Further high quality randomized controlled trials are required to determine if certain subgroup populations benefit from surgical management.
文摘Liver trauma is the most common abdominal emergency with high morbidity and mortality. Now, nonoperative management（NOM） is a selective method for liver trauma. The aim of this study was to determine the success rate, mortality and morbidity of NOM for isolated liver trauma.Medical records of 81 patients with isolated liver trauma in our unit were analyzed retrospectively. The success rate, mortality and morbidity of NOM were evaluated. In this series, 9 patients with grade IV-V liver injuries underwent emergent operation due to hemodynamic instability; 72 patients, 6 with grade V, 18 grade IV, 29 grade III, 15 grade II and 4 grade I, with hemodynamic stability received NOM. The overall success rate of NOM was 97.2%（70/72）. The success rates of NOM in the patients with grade I-III, IV and V liver trauma were100%, 94.4% and 83.3%. The complication rates were 10.0%and 45.5% in the patients who underwent NOM and surgical treatment, respectively. No patient with grade I-II liver trauma had complications. All patients who underwent NOM survived.NOM is the first option for the treatment of liver trauma if the patient is hemodynamically stable. The grade of liver injury and the volume of hemoperitoneum are not suitable criteria for selecting NOM. Hepatic angioembolization associated with the correction of hypothermia, coagulopathy and acidosis is important in the conservative treatment for liver trauma.
文摘There remains much ambiguity on what non-operative management(NOM)of rectal cancer truly entails in terms of the methods to be adopted and the best algorithm to follow.This is clearly shown by the discordance between various national and international guidelines on NOM of rectal cancer.The main aim of the NOM strategy is organ preservation and avoiding unnecessary surgical in-tervention,which carries its own risk of morbidity.A highly specific and sensitive surveillance program must be devised to avoid patients undergoing unnecessary surgical interventions.In many studies,NOM,often interchangeably called the Watch and Wait strategy,has been shown as a promising treatment option when undertaken in the appropriate patient population,where a clinical complete res-ponse is achieved.However,there are no clear guidelines on patient selection for NOM along with the optimal method of surveillance.
文摘BACKGROUND Majority of adhesive small bowel obstruction(SBO)cases can be managed nonoperatively.However,a proportion of patients failed non-operative management.AIM To evaluate the predictors of successful non-operative management in adhesive SBO.METHODS A retrospective study was performed for all consecutive cases of adhesive SBO from November 2015 to May 2018.Data collated included basic demographics,clinical presentation,biochemistry and imaging results and management outcomes.The imaging studies were independently analyzed by a radiologist who was blinded to the clinical outcomes.The patients were divided into group A operative(including those that failed initial non-operative management)and group B non-operative for analysis.RESULTS Of 252 patients were included in the final analysis;group A(n=90)(35.7%)and group B(n=162)(64.3%).There were no differences in the clinical features between both groups.Laboratory tests of inflammatory markers and lactate levels were similar in both groups.From the imaging findings,the presence of a definitive transition point[odds ratio(OR)=2.67,95%confidence interval(CI):0.98-7.32,P=0.048],presence of free fluid(OR=2.11,95%CI:1.15-3.89,P=0.015)and absence of small bowel faecal signs(OR=1.70,95%CI:1.01-2.88,P=0.047)were predictive of the need of surgical intervention.In patients that received water soluble contrast medium,the evidence of contrast in colon was 3.83 times predictive of successful non-operative management(95%CI:1.79-8.21,P=0.001).CONCLUSION The computed tomography findings can assist clinicians in deciding early surgical intervention in adhesive SBO cases that are unlikely to be successful with non-operative management to prevent associated morbidity and mortality.
文摘Introduction: results after non-operative management for knees sustaining combined acute anterior and posterior cruciate ligament tears were presented. Subjects: 13 patients, 10 with medial, and 3 with lateral ligament injury. Methods: non-operative management consisted of employing a brace to prevent sagittal translation of the tibia. Quadriceps muscle and early passive knee motion exercises in the brace was encouraged immediately after arthroscopy. Weight-bearing was forbidden for 3 weeks. The brace was not removed for 3 months. Follow-up periods ranged from 2 to 6 years (mean, 3 years 2 months). Results: none, but one patient had a slight restriction of knee flexion. Quadriceps muscle strength revealed an average of 89.0% of normal side. The knee score indicated 2 patients rated good, 3 rated fair, and 8 rated poor. The score correlated with measurements of anterior and posterior translation on the stress radiograph significantly. Stress radiography revealed that anterior laxity was reduced better than posterior laxity significantly. Conclusion: non-operative brace therapy can be considered for this combined injury as the initial treatment. A late reconstruction would be performed when the result was not satisfactory. Preserved range of motion and muscle strength after brace therapy had a great advantage to the late reconstructive surgery.
基金supported by the Innovation Foundation of Provincial Education Department of Gansu(2024B-005)the Gansu Province National Science Foundation(22YF7GA182)the Fundamental Research Funds for the Central Universities(No.lzujbky2022-kb01)。
文摘Modal parameters can accurately characterize the structural dynamic properties and assess the physical state of the structure.Therefore,it is particularly significant to identify the structural modal parameters according to the monitoring data information in the structural health monitoring(SHM)system,so as to provide a scientific basis for structural damage identification and dynamic model modification.In view of this,this paper reviews methods for identifying structural modal parameters under environmental excitation and briefly describes how to identify structural damages based on the derived modal parameters.The paper primarily introduces data-driven modal parameter recognition methods(e.g.,time-domain,frequency-domain,and time-frequency-domain methods,etc.),briefly describes damage identification methods based on the variations of modal parameters(e.g.,natural frequency,modal shapes,and curvature modal shapes,etc.)and modal validation methods(e.g.,Stability Diagram and Modal Assurance Criterion,etc.).The current status of the application of artificial intelligence(AI)methods in the direction of modal parameter recognition and damage identification is further discussed.Based on the pre-vious analysis,the main development trends of structural modal parameter recognition and damage identification methods are given to provide scientific references for the optimized design and functional upgrading of SHM systems.
基金funded by the project of the Major Scientific and Technological Projects of CNOOC in the 14th Five-Year Plan(No.KJGG2022-0701)the CNOOC Research Institute(No.2020PFS-03).
文摘To analyze the differences in the transport and distribution of different types of proppants and to address issues such as the short effective support of proppant and poor placement in hydraulically intersecting fractures,this study considered the combined impact of geological-engineering factors on conductivity.Using reservoir production parameters and the discrete elementmethod,multispherical proppants were constructed.Additionally,a 3D fracture model,based on the specified conditions of the L block,employed coupled(Computational Fluid Dynamics)CFD-DEM(Discrete ElementMethod)for joint simulations to quantitatively analyze the transport and placement patterns of multispherical proppants in intersecting fractures.Results indicate that turbulent kinetic energy is an intrinsic factor affecting proppant transport.Moreover,the efficiency of placement and migration distance of low-sphericity quartz sand constructed by the DEM in the main fracture are significantly reduced compared to spherical ceramic proppants,with a 27.7%decrease in the volume fraction of the fracture surface,subsequently affecting the placement concentration and damaging fracture conductivity.Compared to small-angle fractures,controlling artificial and natural fractures to expand at angles of 45°to 60°increases the effective support length by approximately 20.6%.During hydraulic fracturing of gas wells,ensuring the fracture support area and post-closure conductivity can be achieved by controlling the sphericity of proppants and adjusting the perforation direction to control the direction of artificial fractures.
文摘Objective: the indications and clinical effects of non-surgical treatment for 49 cases of traumatic splenic rupture were analyzed and summarized. Methods: the clinical data of 49 patients with traumatic splenic rupture admitted to our hospital from January 2006 to December 2015 were retrospectively analyzed. Results: all cases were graded according to the degree of injury. 45 cases were cured successfully (91.84%) after non-operative treatment. 4 cases (8.16%) were converted to surgical treatment during the course of conservative treatment, and there was no death. Conclusion: traumatic splenic rupture is very dangerous and changeable. Non-operative and surgical indications should be reasonably grasped according to the grade of splenic injury and the change of disease condition.
文摘This study investigated the physicochemical properties,enzyme activities,volatile flavor components,microbial communities,and sensory evaluation of high-temperature Daqu(HTD)during the maturation process,and a standard system was established for comprehensive quality evaluation of HTD.There were obvious changes in the physicochemical properties,enzyme activities,and volatile flavor components at different storage periods,which affected the sensory evaluation of HTD to a certain extent.The results of high-throughput sequencing revealed significant microbial diversity,and showed that the bacterial community changed significantly more than did the fungal community.During the storage process,the dominant bacterial genera were Kroppenstedtia and Thermoascus.The correlation between dominant microorganisms and quality indicators highlighted their role in HTD quality.Lactococcus,Candida,Pichia,Paecilomyces,and protease activity played a crucial role in the formation of isovaleraldehyde.Acidic protease activity had the greatest impact on the microbial community.Moisture promoted isobutyric acid generation.Furthermore,the comprehensive quality evaluation standard system was established by the entropy weight method combined with multi-factor fuzzy mathematics.Consequently,this study provides innovative insights for comprehensive quality evaluation of HTD during storage and establishes a groundwork for scientific and rational storage of HTD and quality control of sauce-flavor Baijiu.
基金funded by the National Key R&D Program of China(Grant No.2022YFC2903904)the National Natural Science Foundation of China(Grant Nos.51904057 and U1906208).
文摘Due to the heterogeneity of rock masses and the variability of in situ stress,the traditional linear inversion method is insufficiently accurate to achieve high accuracy of the in situ stress field.To address this challenge,nonlinear stress boundaries for a numerical model are determined through regression analysis of a series of nonlinear coefficient matrices,which are derived from the bubbling method.Considering the randomness and flexibility of the bubbling method,a parametric study is conducted to determine recommended ranges for these parameters,including the standard deviation(σb)of bubble radii,the non-uniform coefficient matrix number(λ)for nonlinear stress boundaries,and the number(m)and positions of in situ stress measurement points.A model case study provides a reference for the selection of these parameters.Additionally,when the nonlinear in situ stress inversion method is employed,stress distortion inevitably occurs near model boundaries,aligning with the Saint Venant's principle.Two strategies are proposed accordingly:employing a systematic reduction of nonlinear coefficients to achieve high inversion accuracy while minimizing significant stress distortion,and excluding regions with severe stress distortion near the model edges while utilizing the central part of the model for subsequent simulations.These two strategies have been successfully implemented in the nonlinear in situ stress inversion of the Xincheng Gold Mine and have achieved higher inversion accuracy than the linear method.Specifically,the linear and nonlinear inversion methods yield root mean square errors(RMSE)of 4.15 and 3.2,and inversion relative errors(δAve)of 22.08%and 17.55%,respectively.Therefore,the nonlinear inversion method outperforms the traditional multiple linear regression method,even in the presence of a systematic reduction in the nonlinear stress boundaries.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.52271317 and 52071149)the Fundamental Research Funds for the Central Universities(HUST:2019kfy XJJS007)。
文摘To address the problems of low accuracy by the CONWEP model and poor efficiency by the Coupled Eulerian-Lagrangian(CEL)method in predicting close-range air blast loads of cylindrical charges,a neural network-based simulation(NNS)method with higher accuracy and better efficiency was proposed.The NNS method consisted of three main steps.First,the parameters of blast loads,including the peak pressures and impulses of cylindrical charges with different aspect ratios(L/D)at different stand-off distances and incident angles were obtained by two-dimensional numerical simulations.Subsequently,incident shape factors of cylindrical charges with arbitrary aspect ratios were predicted by a neural network.Finally,reflected shape factors were derived and implemented into the subroutine of the ABAQUS code to modify the CONWEP model,including modifications of impulse and overpressure.The reliability of the proposed NNS method was verified by related experimental results.Remarkable accuracy improvement was acquired by the proposed NNS method compared with the unmodified CONWEP model.Moreover,huge efficiency superiority was obtained by the proposed NNS method compared with the CEL method.The proposed NNS method showed good accuracy when the scaled distance was greater than 0.2 m/kg^(1/3).It should be noted that there is no need to generate a new dataset again since the blast loads satisfy the similarity law,and the proposed NNS method can be directly used to simulate the blast loads generated by different cylindrical charges.The proposed NNS method with high efficiency and accuracy can be used as an effective method to analyze the dynamic response of structures under blast loads,and it has significant application prospects in designing protective structures.
基金supported by the National Natural Science Foundation of China(12172023).
文摘The separation-of-variable(SOV)methods,such as the improved SOV method,the variational SOV method,and the extended SOV method,have been proposed by the present authors and coworkers to obtain the closed-form analytical solutions for free vibration and eigenbuckling of rectangular plates and circular cylindrical shells.By taking the free vibration of rectangular thin plates as an example,this work presents the theoretical framework of the SOV methods in an instructive way,and the bisection–based solution procedures for a group of nonlinear eigenvalue equations.Besides,the explicit equations of nodal lines of the SOV methods are presented,and the relations of nodal line patterns and frequency orders are investigated.It is concluded that the highly accurate SOV methods have the same accuracy for all frequencies,the mode shapes about repeated frequencies can also be precisely captured,and the SOV methods do not have the problem of missing roots as well.
