Reliability Distribution of Numerical Control Lathe Based on Correlation Analysis

Combined Reliability distribution with correlation analysis,a new method has been proposed to make Reliability distribution where considering the elements about structure correlation and failure correlation of subsystems.Firstly,we make a sequence for subsystems by means of TOPSIS which comprehends the considerations of Reliability allocation,and introducing a Copula connecting function to set up a distribution model based on structure correlation,failure correlation and target correlation,and then acquiring reliability target area of all subsystems by Matlab.In this method,not only the traditional distribution considerations are concerned,but also correlation influences are involved,to achieve supplementing information and optimizing distribution.

A New Approach for Parameter Estimation of Mixed Weibull Distribution:A Case Study in Spindle

In order to improve the accuracy and efficiency of graphical method and maximum likelihood estimation( MLE) in Mixed Weibull distribution parameters estimation,Graphical-GA combines the advantage of graphical method and genetic algorithm( GA) is proposed.Firstly,with the analysis of Weibull probability paper( WPP),mixed Weibull is identified to data fitting.Secondly,the observed value of shape and scale parameters are obtained by graphical method with least square,then optimizing the parameters of mixed Weibull with GA.Thirdly,with the comparative analysis on graphical method,piecewise Weibull and two-Weibull,it shows graphical-GA mixed Weibull is the best.Finally,the spindle MTBF point estimation and interval estimation are got based on mixed Weibull distribution.The results indicate that graphical-GA are improved effectively and the evaluation of spindle can provide the basis for design and reliability growth.

Importance Analysis on Subsystem of CNC Lathe Based on TOPSIS

An importance analysis model for computer numerical control（CNC）lathe subsystems was proposed.The model was based on technique for order preference by similarity to an ideal solution（TOPSIS）and considered the structure correlation between subsystems and the complete machine,the fault correlation of each subsystem and so on.The model can obtain a comprehensive sequencing of subsystems based on their importance to the complete machine.It lays a theoretical foundation for reliability allocation.

Analysis on Failure Mode Severity of Machining Center Spindle System

According to the subjectivity and fuzziness of analysis on failure mode severity about spindle system of machining center,an analysis model of the failure mode severity of such a system is proposed based on the new fault severity index system, improved analytic hierarchy process( IAHP) and entropy-based fuzzy comprehensive evaluation. IAHP and entropy methods are adopted to determine the comprehensive failure severity index weight. The evaluation result is obtained after the factor set,comment set,weight set,and other parameters are determined,and then the level of risk degree and numerical value order of every spindle system failure mode is given. By taking an example,we verify that the proposed method can quantify the qualitative problem comprehensively,obtain more accurate analysis results,and provide the theoretical reference for mechanization and sequencing of failure mode effect analysis in reliability analysis. The calculation results can also serve as the basis of failure mode,effects,and criticality analysis in the subsequent step.

Optimizing circumferential assembly angle of rotor parts connected by curvic couplings based on acquired tooth surface error data

Due to the excellent self-centering and load-carrying capability,curvic couplings have been widely used in advanced aero-engine rotors.However,curvic tooth surface errors lead to poor assembly precision.Traditional physical-master-gauge-based indirect tooth surface error measurement and circumferential assembly angle optimization methods have the disadvantages of high cost and weak generality.The unknown tooth surface fitting mechanism is a big barrier to assembly precision prediction and improvement.Therefore,this work puts forward a data-driven assembly simulation and optimization approach for aero-engine rotors connected by curvic couplings.The origin of curvic tooth surface error is deeply investigated.Using 5-axis sweep scan method,a large amount of high-precision curvic tooth surface data are acquired efficiently.Based on geometric models of parts,the fitting mechanism of curvic couplings is uncovered for assembly precision simulation and prediction.A circumferential assembly angle optimization model is developed to decrease axial and radial assembly runouts.Experimental results show that the assembly precision can be predicted accurately and improved dramatically.By uncovering the essential principle of the assembly precision formation and proposing circumferential assembly angle optimization model,this work is meaningful for assembly quality,efficiency and economy improvement of multistage aero-engine rotors connected by curvic couplings.

Weakened humoral and cellular immune response to the inactivated COVID-19 vaccines in Chinese individuals with obesity/overweight

Inactivated COVID-19 vaccines have been widely used to vaccinate the Chinese population.However,limited literature exists to explore the effect of obesity on the humoral and cellular immune response to these vaccines.In this study,132 high BMI(Body mass index)(obesity and overweight,BMI≥24 kg/m^(2))and 82 normal BMI(BMI<24 kg/m^(2))participants were enrolled.Adverse events(AEs),Spike receptor-binding domain IgG antibody(anti-RBD-IgG),neutralizing antibodies(NAbs),and specific B-cell and T-cell responses were evaluated 21–105 days after full-course inactivated COVID-19 vaccination.The overall incidence of AEs was similar in individuals with and without obesity/overweight.No serious vaccine-related AEs occurred.Individuals with obesity/overweight had a reduced seropositivity rate of NAbs compared to those with normal BMI.Anti-RBD-IgG and NAbs titers in the high BMI group were significantly lower than those in the normal BMI group.The frequencies of RBD-specific memory B cells(MBCs)and the numbers of spike-specific TNF-α+spot-forming cells(SFCs)in individuals with obesity/overweight were reduced compared with those noted in individuals without obesity/overweight.A similar trend of weakened humoral responses was also observed in individuals with central obesity.Our study results suggested that inactivated COVID-19 vaccines were safe and well tolerated but induced poor humoral and cellular immune responses in Chinese individuals with obesity/overweight.

Dynamic Humoral Immune Response to Primary and Booster Inactivated SARS-CoV-2 Vaccination in Patients with Cirrhosis

Background and Aims:Our aim was to determine the immune efficacy of a severe acute respiratory syndrome coronavirus-2(SARS-CoV-2)booster vaccination in cirrhotic patients who had received the primary series.Methods:We performed a longitudinal assessment in 48 patients with cirrhosis,57 patients with chronic hepatitis B(CHB)and 68 healthy controls(HCs)to continuously track the dynamics of SARS-CoV-2 specific antibodies and memory B cells after receiving the primary series and booster dose at different times.A pseudovirus neutralization assay was used to determine neutralization against Omicron subvariants BA.2.12.1,BA.4 and BA.5 from serum samples collected from three cohorts.Results:Serum anti-receptor-binding domain(RBD)immunoglobulin(Ig)G and neutralizing antibody(NAb)levels in cirrhotic patients were elevated within 15–45 days after completing the primary series before rapidly declining and reaching a valley at around 165–195 days.After receiving the booster dose,both antibody levels were significantly increased to levels comparable to patients with CHB and HCs.Subgroup analysis showed that booster vaccination induced weaker antibody responses in patients with decompensated cirrhosis than in those with compensated cirrhosis.The SARS-CoV-2 memory B-cell response in cirrhotic patients was durable during follow-up regardless of the hepatic fibrocirrhosis grade.However,compared with the primary series,the booster dose did not result in an evident improvement of neutralization activity against the Omicron subvariants BA.2.12.1 and BA.4,and was followed by a significant decrease in the titer against BA.5.Conclusions:A booster dose elicited a robust and durable humoral response to the wild-type strain in cirrhotic patients but not the Omicron subvariants.Repeated vaccination of inactivated SARS-CoV-2 vaccine may not benefit cirrhotic patients in neutralization against newly circulating strains.

A bibliometric review on stability and reinforcement of special soil subgrade based on CiteSpace

To establish a scientific foundation for further studies and to better understand special soil subgrade research foci and development directions,a visualization analysis of 2601 and 2102 article from 2005 to 2019 was conducted based on the China National Knowledge Infrastructure(CNKI)and Web of Science(WOS)core databases.Time distribution feature,country/region distribution,organization distribution,main source journal distribution,research hotspots and frontier of literature are all analyzed,and the knowledge domain maps are plotted with CiteSpace visualization software.It was found that from 2005 to 2019,the analysis uncovered that China,USA,Australia,Iran and India as the top five most productive countries publishing about subgrade stability and reinforcement with special soil,but results from the USA are the most influential ones in this field,the national/regional quantitative analysis showed that the density of international co-occurrence network is higher than that of China,which indicated that the international research on the subgrade stability and reinforcement with special soil is relatively concentrated,and the CNKI research was focused on dynamic compaction methods,adding CFG pile and geogrid to strengthen the soil subgrade and the WOS researches were focused on the use of geosynthetics to strengthen the subgrade.The current researches of CNKI were revealed to be the compression and deformation characteristics of lightweight foam soil fill subgrade whereas soft soil subgrade problems and numerical analysis methods were the current research foci in the WOS.

Development of database of real-world diesel vehicle emission factors for China

A database of real-world diesel vehicle emission factors, based on type and technology, has been developed following tests on more than 300 diesel vehicles in China using a portable emission measurement system. The database provides better understanding of diesel vehicle emissions under actual driving conditions. We found that although new regulations have reduced real-world emission levels of diesel trucks and buses significantly for most pollutants in China, NOx emissions have been inadequately controlled by the current standards, especially for diesel buses, because of bad driving conditions in the real world. We also compared the emission factors in the database with those calculated by emission factor models and used in inventory studies. The emission factors derived from COPERT（Computer Programmer to calculate Emissions from Road Transport） and MOBILE may both underestimate real emission factors, whereas the updated COPERT and PART5（Highway Vehicle Particulate Emission Modeling Software） models may overestimate emission factors in China. Real-world measurement results and emission factors used in recent emission inventory studies are inconsistent,which has led to inaccurate estimates of emissions from diesel trucks and buses over recent years. This suggests that emission factors derived from European or US-based models will not truly represent real-world emissions in China. Therefore, it is useful and necessary to conduct systematic real-world measurements of vehicle emissions in China in order to obtain the optimum inputs for emission inventory models.

Waning humoral immune responses to inactivated SARS-CoV-2 vaccines in patients with severe liver disease

Dear Editor,The Coronavirus disease 2019(COVID-19)pandemic caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)is still ongoing around the world.Patients with severe liver disease(SLD),such as compensated cirrhosis(CC),decompensated cirrhosis(DC)or hepatocellular carcinoma(HCC),are highly vulnerable and have worse outcomes from COVID-191.Vaccines are effective measure for the prevention of SARS-CoV-2 infection,severe disease,and mortality.Recent studies have preliminarily described the safety and immunogenicity of SARSCoV-2 vaccines in patients with nonalcoholic fatty liver disease(NAFLD)2,and in patients with chronic hepatitis B virus infection(CHB)3.However,data are limited on the safety and immunogenicity of inactivated vaccines against SARS-CoV-2 in SLD patients.Additionally,the memory B cells(MBCs)responses and immunological memory after vaccination in SLD patients is still unclear.Hence,we aim to explore the safety,antibody responses,and MBCs responses of inactivated vaccines(BBIBPCorV or CoronaVac)in SLD patients through a prospective observational study(NCT05007665).