Gear assembly errors can lead to the increase of vibration and noise of the system,which affect the stability of system.The influence can be compensated by tooth modification.Firstly,an improved three-dimensional load...Gear assembly errors can lead to the increase of vibration and noise of the system,which affect the stability of system.The influence can be compensated by tooth modification.Firstly,an improved three-dimensional loaded tooth contact analysis(3D-LTCA)method which can consider tooth modification and coupling assembly errors is proposed,and mesh stiffness calculated by proposed method is verified by MASTA software.Secondly,based on neural network,the surrogate model(SM)that maps the relationship between modification parameters and mesh mechanical parameters is established,and its accuracy is verified.Finally,SM is introduced to establish an optimization model with the target of minimizing mesh stiffness variations and obtaining more even load distribution on mesh surface.The results show that even considering training time,the efficiency of gear pair optimization by surrogate model is still much higher than that by LTCA method.After optimization,the mesh stiffness fluctuation of gear pair with coupling assembly error is reduced by 34.10%,and difference in average contact stresses between left and right regions of the mesh surface is reduced by 62.84%.展开更多
The contact characteristics of the rough tooth surface during the meshing process are significantly affected by the lubrication state.The coupling effect of tooth surface roughness and lubrication on meshing character...The contact characteristics of the rough tooth surface during the meshing process are significantly affected by the lubrication state.The coupling effect of tooth surface roughness and lubrication on meshing characteristics of planetary gear is studied.An improved three-dimensional(3 D)anisotropic tooth surface roughness fractal model is proposed based on the experimental parameters.Considering asperity contact and elastohydrodynamic lubrication(EHL),the contact load and flexibility deformation of the tooth surface are derived,and the deformation compatibility equation of the 3 D loaded tooth contact analysis(3 D-LTCA)method is improved.The asperity of the tooth surface changes the system from EHL to mixed lubrication and reduces the stiffness of the oil film.Compared with the sun planet gear,the asperity has a greater effect on the meshing characteristics of the ring-planet gear.Compared with the proposed method,the comprehensive stiffness obtained by the traditional calculation method considering the lubrication effect is smaller,especially for the ring-planet gear.Compared with roughness,speed and viscosity,the meshing characteristics of planetary gears are most sensitive to torque.展开更多
The aim of this paper is to simulate and study the early moments of the reactive ballistics of a large caliber projectile fired from a gun,combining 0D and 2D axisymmetric Computational Fluid Dynamics(CFD)approaches.F...The aim of this paper is to simulate and study the early moments of the reactive ballistics of a large caliber projectile fired from a gun,combining 0D and 2D axisymmetric Computational Fluid Dynamics(CFD)approaches.First,the methodology is introduced with the development of an interior ballistics(IB)lumped parameter code(LPC),integrating an original image processing method for calculating the specific regression of propellant grains that compose the gun propellant.The ONERA CFD code CEDRE,equipped with a Dynamic Mesh Technique(DMT),is then used in conjunction with the developed LPC to build a dedicated methodology to calculate IB.First results obtained on the AGARD gun and 40 mm gun test cases are in a good agreement with the existing literature.CEDRE is also used to calculate inter-mediate ballistics(first milliseconds of free flight of the projectile)with a multispecies and reactive approach either starting from the gun muzzle plane or directly following IB.In the latter case,an inverse problem involving a Latin hypercube sampling method is used to find a gun propellant configuration that allows the projectile to reach a given exit velocity and base pressure when IB ends.The methodology developed in this work makes it possible to study the flame front of the intermediate flash and depressurization that occurs in a base bleed(BB)channel at the gun muzzle.Average pressure variations in the BB channel during depressurization are in good agreement with literature.展开更多
Objective:To perform a meta-analysis to evaluate the diagnostic performance of computed tomography(CT) and transthoracic echocardiography(TTE) in complex congenital heart diseases(CHD) in China.Methods:MEDLINE,Cochran...Objective:To perform a meta-analysis to evaluate the diagnostic performance of computed tomography(CT) and transthoracic echocardiography(TTE) in complex congenital heart diseases(CHD) in China.Methods:MEDLINE,Cochrane library and China National Knowledge Infrastructure(CNKI) database from January 1966 to October 2010,were searched for initial studies in China.All the studies,published in English or Chinese,used TTE,CT,or both as diagnostic tests for CHD and reported the rate of true-positive,true-negative,false-positive and false-negative diagnoses of CHD from TTE and CT findings with the surgical results as the 'gold-standard'(15 studies,XX patients) were collected.The statistic software package,'Meta-Disc 1.4',was used to conduct data analysis.A covariate analysis was used to evaluate the influence of patient or study-related factors on sensitivity.Results:Pooled sensitivity for diagnosis of CHD were 95% [95% confidence interval(CI):94%~96%] for CT studies and 87%(95% CI:85%~88%) for TTE studies.The difference between the pooled sensitivity of CT and that of TTE was statistically significant(P<0.001).TTE had higher sensitivity [0.96(95% CI:0.94~0.97)] for cardiac malformation but lower sensitivity [0.78(95% CI:0.76~0.81)] for extracardiac malformation than CT.Conclusion:CT can provide added diagnostic information compared with TTE in patients with CHD in China,especially for patients suspected of extracardiac malformation.展开更多
Background and objective:Lung cancer is one of the malignant tumors.Gene mutations associated with cellular immune function and regulating the activation and proliferation of immune cells.Several publications have exp...Background and objective:Lung cancer is one of the malignant tumors.Gene mutations associated with cellular immune function and regulating the activation and proliferation of immune cells.Several publications have explored the relationship between cytotoxic T lymphocyte antigen-4(CTLA-4)+49 adenine(A)/guanine(G)polymorphism and susceptibility of lung cancer,but the results remain controversial.Thus,we performed this meta-analysis to derive a more comprehensive estimation of the relationship.Methods:All articles addressed lung cancer and polymorphisms of CTLA-4 were searched from the Pub Med,EMBASE databases published up to June 29,2019.Odds ratios(ORs)with 95%confidence intervals(CIs)were used to assess the strength of association.Publication bias of relevant studies was examined via Begg’s test and funnel plots.Results:The meta-analysis included 8 case-control studies covering 4,430 lung cancer patients and 5,198 healthy controls from September 2008 to April 2020.The overall eligible data indicated that CTLA-4+49 A/G polymorphisms did not correlate with the elevated lung cancer risk in all genetic comparison models(dominant model:OR=1.037,95%CI:0.925-1.161;recessive model:OR=0.968,95%CI:0.888-1.055;allele model:OR=0.992,95%CI:0.933-1.054;homozygous model:OR=0.980,95%CI:0.857-1.121;heterozygous model:OR=1.023,95%CI:0.906-1.154).In further stratified analyses,CTLA-4+49 A/G polymorphism was found to be significantly associated with susceptibility to NSCLC in these models(dominant model:OR=1.404,95%CI:1.074-1.836;allele model:OR=1.273,95%CI:1.034-1.565;homozygous model:OR=1.553,95%CI:1.044-2.310;heterozygous model:OR=1.308,95%CI:1.062-1.611).Conclusion:CTLA-4+49 A/G polymorphism were not associated with the risk of lung cancer but might be a risk factor only in NSCLC.展开更多
OBJECTIVE To systematically assess the efficacy and safety of acupuncture in treating acute tonsillitis,providing a reference for clinical decision-making.METHODS We searched PubMed,CENTRAL,Embase,Web of Science,China...OBJECTIVE To systematically assess the efficacy and safety of acupuncture in treating acute tonsillitis,providing a reference for clinical decision-making.METHODS We searched PubMed,CENTRAL,Embase,Web of Science,China National Knowledge Infrastruc⁃ture,China Biomedical,clinical research registra⁃tion platforms,grey literature,and the reference lists of the selected studies from inception to Oct.30,2022.The risk of bias assessment used Rev⁃Man.Meta-analysis was performed using STATA with Hedges′g value.In addition,we performed subgroup analysis,meta-regression,and publica⁃tion bias detection with Harbord′s and Egger′s tests.RESULTS We included 19 randomized controlled trials comprising 1701 patients,of which 1 study was assessed high risk of bias.The primary outcome,the response rate,revealed that acupuncture was more effective than antibi⁃otics.The secondary outcomes showed that the difference in the reduction of the VAS scores,sore throat time,and white blood cell counts was statistically significant with acupuncture compared to antibiotics.However,the difference in modulat⁃ing neutrophil percentage and C-reactive protein was not statistically significant.Besides,acupuncture treatments showed a lower incidence of adverse events than antibiotics.CONCLUSION Acupuncture therapy on acute tonsillitis is safe,and the response rate is superior to antibiotics.For alleviating sore throat symptoms,shortening sore throat time,and improving immune in fl am mation index,acupuncture has positive signi fi cance.Nevertheless,because of the limitations of this study,our conclusions should be inter⁃preted with caution.Future efforts still need more high-quality trials to improve the methodology and reporting quality.展开更多
OBJECTIVE To assess the effi⁃cacy and safety of acupuncture-related treat⁃ments for postherpetic neuralgia(PHN),identify the most effective acupuncture and related treat⁃ments.METHODS PubMed,Cochrane Central Register ...OBJECTIVE To assess the effi⁃cacy and safety of acupuncture-related treat⁃ments for postherpetic neuralgia(PHN),identify the most effective acupuncture and related treat⁃ments.METHODS PubMed,Cochrane Central Register of Controlled Trials,Embase,Web of Science,and four Chinese databases,a clinical research registration platform,and grey literature were searched.We evaluated the risk of bias and quality in the included studies and per⁃formed a Bayesian multiple network meta-analysis.RESULTS We included 29 randomized controlled trials comprising 1973 patients,of which approximately 17.24%showed a high risk of bias.According to the Jadad scale,2,16,and 11 studies were high,medium,and low quality,respectively.The pairwise meta-analysis results revealed that the efficacy of all acupuncture-related treatments for pain relief related to PHN showed the difference was statistically significant com⁃pared with that of antiepileptics.The network meta-analysis results showed that pricking and cupping plus antiepileptics were the most effective,followed by electroacupuncture(EA)plus antiepileptics for pain relief in patients with PHN.EA plus antiepileptics ranked the best regarding reduced Pittsburgh Sleep Quality Index and Self-Rating Depression Scale scores in patients with PHN.No results were found regarding total response rate or quality of life among this study.Acupuncture-related treatments showed a lower incidence of adverse events than that of antiepi⁃leptics-related treatments.CONCLUSION Acu⁃puncture-related therapies may be potential treat⁃ment options for PHN and are relatively safe.Pricking and cupping plus antiepileptics are the most effective techniques for pain relief.EA plus antiepileptics is the best approach for improving insomnia and depression symptoms of PHN.展开更多
Objective Individuals with pulmonary hypertension(PH)have reduced exercise capacity and quality of life.Exercise-based rehabilitation may have beneficial effects to improve the exercise capacity and quality of life in...Objective Individuals with pulmonary hypertension(PH)have reduced exercise capacity and quality of life.Exercise-based rehabilitation may have beneficial effects to improve the exercise capacity and quality of life in patients with PH.We aim to assess the efficacy and safety of exercised-based rehabilitation for people eith PH by performing a randomized controlled trails(RCTs)meta-analysis of exercised-based rehabilitation for people with PH by performing a randomized controlled trails meta-analysis.展开更多
基金Project(11972112)supported by the National Natural Science Foundation of ChinaProject(N2103024)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(J2019-IV-0018-0086)supported by the National Science and Technology Major Project,China。
文摘Gear assembly errors can lead to the increase of vibration and noise of the system,which affect the stability of system.The influence can be compensated by tooth modification.Firstly,an improved three-dimensional loaded tooth contact analysis(3D-LTCA)method which can consider tooth modification and coupling assembly errors is proposed,and mesh stiffness calculated by proposed method is verified by MASTA software.Secondly,based on neural network,the surrogate model(SM)that maps the relationship between modification parameters and mesh mechanical parameters is established,and its accuracy is verified.Finally,SM is introduced to establish an optimization model with the target of minimizing mesh stiffness variations and obtaining more even load distribution on mesh surface.The results show that even considering training time,the efficiency of gear pair optimization by surrogate model is still much higher than that by LTCA method.After optimization,the mesh stiffness fluctuation of gear pair with coupling assembly error is reduced by 34.10%,and difference in average contact stresses between left and right regions of the mesh surface is reduced by 62.84%.
基金Project(2024A1515240020)supported by the Guangdong Basic and Applied Basic Research Foundation,China。
文摘The contact characteristics of the rough tooth surface during the meshing process are significantly affected by the lubrication state.The coupling effect of tooth surface roughness and lubrication on meshing characteristics of planetary gear is studied.An improved three-dimensional(3 D)anisotropic tooth surface roughness fractal model is proposed based on the experimental parameters.Considering asperity contact and elastohydrodynamic lubrication(EHL),the contact load and flexibility deformation of the tooth surface are derived,and the deformation compatibility equation of the 3 D loaded tooth contact analysis(3 D-LTCA)method is improved.The asperity of the tooth surface changes the system from EHL to mixed lubrication and reduces the stiffness of the oil film.Compared with the sun planet gear,the asperity has a greater effect on the meshing characteristics of the ring-planet gear.Compared with the proposed method,the comprehensive stiffness obtained by the traditional calculation method considering the lubrication effect is smaller,especially for the ring-planet gear.Compared with roughness,speed and viscosity,the meshing characteristics of planetary gears are most sensitive to torque.
基金the French Defense Innovation Agency (AID)the French Procurement Agency for Armament (DGA)ONERA's scientific direction for funding and supporting the present work
文摘The aim of this paper is to simulate and study the early moments of the reactive ballistics of a large caliber projectile fired from a gun,combining 0D and 2D axisymmetric Computational Fluid Dynamics(CFD)approaches.First,the methodology is introduced with the development of an interior ballistics(IB)lumped parameter code(LPC),integrating an original image processing method for calculating the specific regression of propellant grains that compose the gun propellant.The ONERA CFD code CEDRE,equipped with a Dynamic Mesh Technique(DMT),is then used in conjunction with the developed LPC to build a dedicated methodology to calculate IB.First results obtained on the AGARD gun and 40 mm gun test cases are in a good agreement with the existing literature.CEDRE is also used to calculate inter-mediate ballistics(first milliseconds of free flight of the projectile)with a multispecies and reactive approach either starting from the gun muzzle plane or directly following IB.In the latter case,an inverse problem involving a Latin hypercube sampling method is used to find a gun propellant configuration that allows the projectile to reach a given exit velocity and base pressure when IB ends.The methodology developed in this work makes it possible to study the flame front of the intermediate flash and depressurization that occurs in a base bleed(BB)channel at the gun muzzle.Average pressure variations in the BB channel during depressurization are in good agreement with literature.
文摘Objective:To perform a meta-analysis to evaluate the diagnostic performance of computed tomography(CT) and transthoracic echocardiography(TTE) in complex congenital heart diseases(CHD) in China.Methods:MEDLINE,Cochrane library and China National Knowledge Infrastructure(CNKI) database from January 1966 to October 2010,were searched for initial studies in China.All the studies,published in English or Chinese,used TTE,CT,or both as diagnostic tests for CHD and reported the rate of true-positive,true-negative,false-positive and false-negative diagnoses of CHD from TTE and CT findings with the surgical results as the 'gold-standard'(15 studies,XX patients) were collected.The statistic software package,'Meta-Disc 1.4',was used to conduct data analysis.A covariate analysis was used to evaluate the influence of patient or study-related factors on sensitivity.Results:Pooled sensitivity for diagnosis of CHD were 95% [95% confidence interval(CI):94%~96%] for CT studies and 87%(95% CI:85%~88%) for TTE studies.The difference between the pooled sensitivity of CT and that of TTE was statistically significant(P<0.001).TTE had higher sensitivity [0.96(95% CI:0.94~0.97)] for cardiac malformation but lower sensitivity [0.78(95% CI:0.76~0.81)] for extracardiac malformation than CT.Conclusion:CT can provide added diagnostic information compared with TTE in patients with CHD in China,especially for patients suspected of extracardiac malformation.
文摘Background and objective:Lung cancer is one of the malignant tumors.Gene mutations associated with cellular immune function and regulating the activation and proliferation of immune cells.Several publications have explored the relationship between cytotoxic T lymphocyte antigen-4(CTLA-4)+49 adenine(A)/guanine(G)polymorphism and susceptibility of lung cancer,but the results remain controversial.Thus,we performed this meta-analysis to derive a more comprehensive estimation of the relationship.Methods:All articles addressed lung cancer and polymorphisms of CTLA-4 were searched from the Pub Med,EMBASE databases published up to June 29,2019.Odds ratios(ORs)with 95%confidence intervals(CIs)were used to assess the strength of association.Publication bias of relevant studies was examined via Begg’s test and funnel plots.Results:The meta-analysis included 8 case-control studies covering 4,430 lung cancer patients and 5,198 healthy controls from September 2008 to April 2020.The overall eligible data indicated that CTLA-4+49 A/G polymorphisms did not correlate with the elevated lung cancer risk in all genetic comparison models(dominant model:OR=1.037,95%CI:0.925-1.161;recessive model:OR=0.968,95%CI:0.888-1.055;allele model:OR=0.992,95%CI:0.933-1.054;homozygous model:OR=0.980,95%CI:0.857-1.121;heterozygous model:OR=1.023,95%CI:0.906-1.154).In further stratified analyses,CTLA-4+49 A/G polymorphism was found to be significantly associated with susceptibility to NSCLC in these models(dominant model:OR=1.404,95%CI:1.074-1.836;allele model:OR=1.273,95%CI:1.034-1.565;homozygous model:OR=1.553,95%CI:1.044-2.310;heterozygous model:OR=1.308,95%CI:1.062-1.611).Conclusion:CTLA-4+49 A/G polymorphism were not associated with the risk of lung cancer but might be a risk factor only in NSCLC.
文摘OBJECTIVE To systematically assess the efficacy and safety of acupuncture in treating acute tonsillitis,providing a reference for clinical decision-making.METHODS We searched PubMed,CENTRAL,Embase,Web of Science,China National Knowledge Infrastruc⁃ture,China Biomedical,clinical research registra⁃tion platforms,grey literature,and the reference lists of the selected studies from inception to Oct.30,2022.The risk of bias assessment used Rev⁃Man.Meta-analysis was performed using STATA with Hedges′g value.In addition,we performed subgroup analysis,meta-regression,and publica⁃tion bias detection with Harbord′s and Egger′s tests.RESULTS We included 19 randomized controlled trials comprising 1701 patients,of which 1 study was assessed high risk of bias.The primary outcome,the response rate,revealed that acupuncture was more effective than antibi⁃otics.The secondary outcomes showed that the difference in the reduction of the VAS scores,sore throat time,and white blood cell counts was statistically significant with acupuncture compared to antibiotics.However,the difference in modulat⁃ing neutrophil percentage and C-reactive protein was not statistically significant.Besides,acupuncture treatments showed a lower incidence of adverse events than antibiotics.CONCLUSION Acupuncture therapy on acute tonsillitis is safe,and the response rate is superior to antibiotics.For alleviating sore throat symptoms,shortening sore throat time,and improving immune in fl am mation index,acupuncture has positive signi fi cance.Nevertheless,because of the limitations of this study,our conclusions should be inter⁃preted with caution.Future efforts still need more high-quality trials to improve the methodology and reporting quality.
基金National Key Research and Development plan for the Modernization of Traditional Chinese Medicine (2018YFC1707700)National Key Research and Development plan for the Modernization of Traditional Chinese Medicine (2018YFC1707706)National Administration of Traditional Chinese Medicine Evidencebased Capacity Building Project (2019XZZXZJ005)
文摘OBJECTIVE To assess the effi⁃cacy and safety of acupuncture-related treat⁃ments for postherpetic neuralgia(PHN),identify the most effective acupuncture and related treat⁃ments.METHODS PubMed,Cochrane Central Register of Controlled Trials,Embase,Web of Science,and four Chinese databases,a clinical research registration platform,and grey literature were searched.We evaluated the risk of bias and quality in the included studies and per⁃formed a Bayesian multiple network meta-analysis.RESULTS We included 29 randomized controlled trials comprising 1973 patients,of which approximately 17.24%showed a high risk of bias.According to the Jadad scale,2,16,and 11 studies were high,medium,and low quality,respectively.The pairwise meta-analysis results revealed that the efficacy of all acupuncture-related treatments for pain relief related to PHN showed the difference was statistically significant com⁃pared with that of antiepileptics.The network meta-analysis results showed that pricking and cupping plus antiepileptics were the most effective,followed by electroacupuncture(EA)plus antiepileptics for pain relief in patients with PHN.EA plus antiepileptics ranked the best regarding reduced Pittsburgh Sleep Quality Index and Self-Rating Depression Scale scores in patients with PHN.No results were found regarding total response rate or quality of life among this study.Acupuncture-related treatments showed a lower incidence of adverse events than that of antiepi⁃leptics-related treatments.CONCLUSION Acu⁃puncture-related therapies may be potential treat⁃ment options for PHN and are relatively safe.Pricking and cupping plus antiepileptics are the most effective techniques for pain relief.EA plus antiepileptics is the best approach for improving insomnia and depression symptoms of PHN.
文摘Objective Individuals with pulmonary hypertension(PH)have reduced exercise capacity and quality of life.Exercise-based rehabilitation may have beneficial effects to improve the exercise capacity and quality of life in patients with PH.We aim to assess the efficacy and safety of exercised-based rehabilitation for people eith PH by performing a randomized controlled trails(RCTs)meta-analysis of exercised-based rehabilitation for people with PH by performing a randomized controlled trails meta-analysis.
