Numerical analysis of keyhole shape and keyhole establishment time is of great significance for selection and optimization of the process parameters in keyhole plasma arc welding. In this paper, a three-dimensional tr...Numerical analysis of keyhole shape and keyhole establishment time is of great significance for selection and optimization of the process parameters in keyhole plasma arc welding. In this paper, a three-dimensional transient model is developed to analyze the evolutions of keyhole shape and keyhole establishment time in continuous current plasma arc welding process. Firstly, a combined volumetric heat source model is used to simulate the transient variation of temperature field. And then the surface deformation equation is adopted to calculate dynamic features of the keyhole shape and keyhole establishment time inside weld pool, in which the force action on weld pool surface is considered. Experiment is cond^ted to validate the numerical simulation results. The predicted keyhole size and keyhole establishment time are in agreement with the experimental measurement. And the calculated fusion zone geometry is consistent with the measured one.展开更多
The commonly used Poisson rectangular pulse(PRP)model,employed for simulating high-resolution residential water consumption patterns(RWCPs),relies on calibration via medium-resolution RWCPs obtained from practical mea...The commonly used Poisson rectangular pulse(PRP)model,employed for simulating high-resolution residential water consumption patterns(RWCPs),relies on calibration via medium-resolution RWCPs obtained from practical measurements.This introduces inevitable uncertainty stemming from the measured RWCPs,which consequently impacts the precision of model simulations.Here we enhance the accuracy of the PRP model by addressing the uncertainty of RWCPs.We established a critical sampling size of 2000 household water consumption patterns(HWCPs)with a data logging interval(DLI)of 15 min to attain dependable RWCPs.Through Genetic Algorithm calibration,the optimal values of the PRP model's parameters were determined:pulse frequency lλ=91 d^(-1),mean of pulse intensity E(I)=0.346 m^(3) h^(-1),standard deviation of pulse intensity STD(I)=0.292 m^(3) h^(-1),mean of pulse duration E(D)=40 s,and standard deviation of pulse duration STD(D)=55 s.Furthermore,validation was conducted at both HWCP and RWCP levels.We recommend a sampling size of2000 HWCPs and a DLI of30 min for PRP model calibration to balance simulation precision and practical implementation.This study significantly advances the theoretical foundation and real-world application of the PRP model,enhancing its role in urban water supply system management.展开更多
In the paper, the establishment, measurement, data-processing program and monitoring accuracy of the GPS seismic monitoring network in North China, especially in the Capital-Circle area, have been presented briefly. T...In the paper, the establishment, measurement, data-processing program and monitoring accuracy of the GPS seismic monitoring network in North China, especially in the Capital-Circle area, have been presented briefly. The relation of horizontal crustal deformation to tectonic movement, stress-field variation and seismicity has been analyzed in detail. The results indicate that the accuracy of GPS measurement has reached the order of 10-9 and the annual rate of horizontal crustal deformation in North China is about 4 ~5 mm. Horizontal crustal movement is a direct indication of the regional stress field. Therefore, by monitoring the time-sequence variation of horizontal crustal motion, it would be possible to investigate the change in the stress field, to analyze the tendency of seismicity and to determine the seismogenic zones.展开更多
The aim of the research was to evaluate overall quality of introduction of hazard analysis and critical control points （HACCP） prerequisites and HACCP procedures in catering sector in Latvia to reveal common problem...The aim of the research was to evaluate overall quality of introduction of hazard analysis and critical control points （HACCP） prerequisites and HACCP procedures in catering sector in Latvia to reveal common problems that can provoke food-borne infection outbreaks. Certain quantitative indicators were defined and analyzed to conclude about characteristic trends related to implementation of food safety legislation. The state＇s monitoring data on surveillance of catering establishments were used. Fulfillment of legislative requirements in about 6,000 catering establishments was evaluated during time period of 2004-2009. The results of investigation were obtained with help of statistical analyses using MS Excel computer program. The results of the research suggest that most of catering establishments （e.g., 83.6% during 2009） meet the hygiene requirements only partly. Non-conformities regarding HACCP-based self-control procedures were fixed during 49.2% of inspections. The research reveals characteristic shortcomings that are established from year to year, e.g., improper hygiene of premises （established during 30%-40% of inspections, depending on the year）, poor hygiene of technological equipment （established during 27%-37% of inspections）, poor personnel hygiene （established during 11%-22% of inspections）, inadequate competence of food service personnel （established during 10%-35% of inspections）, as well as non-observance of cleaning-disinfection procedures and technological parameters for food processing （established during 11%-25% of inspections, depending on the year）. Actual shortcomings can lead to both the direct and the indirect cross-contamination of food. On the base of the research, it was concluded that further detailed assessment of potential food safety risks is relevant to establish risk-based monitoring activities in catering sector.展开更多
Human nuclear receptor hB1F is a novel member of the fushi tarazu factor Ⅰ subfamily of nuclear receptor superfamily. The studies about its homologous genes indicate that hB1F may play a key role in regulating the me...Human nuclear receptor hB1F is a novel member of the fushi tarazu factor Ⅰ subfamily of nuclear receptor superfamily. The studies about its homologous genes indicate that hB1F may play a key role in regulating the metabolic homeostasis of cholesterol. After obtaining the founder mice carrying the trausgeue of hblf by microiujectiou, each founder was mated to normal C57 mouse and the positive F1 by PCR identification of the same founder were iutercrossed within sisters and brothers to establish the trausgeuic mouse lineage. The results of F1, F2 and offspring of test cross identification showed that the widely expressed hb1f trausgeuic mouse lineage was established successfully in this study. The tissue morphology of the trausgeuic lineage was also analyzed preliminarily.展开更多
文摘Numerical analysis of keyhole shape and keyhole establishment time is of great significance for selection and optimization of the process parameters in keyhole plasma arc welding. In this paper, a three-dimensional transient model is developed to analyze the evolutions of keyhole shape and keyhole establishment time in continuous current plasma arc welding process. Firstly, a combined volumetric heat source model is used to simulate the transient variation of temperature field. And then the surface deformation equation is adopted to calculate dynamic features of the keyhole shape and keyhole establishment time inside weld pool, in which the force action on weld pool surface is considered. Experiment is cond^ted to validate the numerical simulation results. The predicted keyhole size and keyhole establishment time are in agreement with the experimental measurement. And the calculated fusion zone geometry is consistent with the measured one.
基金supported by the National Natural Science Foundation of China(52170105)the Ministry of Science and Technology of China(2019YFD1100105)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(2019043).
文摘The commonly used Poisson rectangular pulse(PRP)model,employed for simulating high-resolution residential water consumption patterns(RWCPs),relies on calibration via medium-resolution RWCPs obtained from practical measurements.This introduces inevitable uncertainty stemming from the measured RWCPs,which consequently impacts the precision of model simulations.Here we enhance the accuracy of the PRP model by addressing the uncertainty of RWCPs.We established a critical sampling size of 2000 household water consumption patterns(HWCPs)with a data logging interval(DLI)of 15 min to attain dependable RWCPs.Through Genetic Algorithm calibration,the optimal values of the PRP model's parameters were determined:pulse frequency lλ=91 d^(-1),mean of pulse intensity E(I)=0.346 m^(3) h^(-1),standard deviation of pulse intensity STD(I)=0.292 m^(3) h^(-1),mean of pulse duration E(D)=40 s,and standard deviation of pulse duration STD(D)=55 s.Furthermore,validation was conducted at both HWCP and RWCP levels.We recommend a sampling size of2000 HWCPs and a DLI of30 min for PRP model calibration to balance simulation precision and practical implementation.This study significantly advances the theoretical foundation and real-world application of the PRP model,enhancing its role in urban water supply system management.
文摘In the paper, the establishment, measurement, data-processing program and monitoring accuracy of the GPS seismic monitoring network in North China, especially in the Capital-Circle area, have been presented briefly. The relation of horizontal crustal deformation to tectonic movement, stress-field variation and seismicity has been analyzed in detail. The results indicate that the accuracy of GPS measurement has reached the order of 10-9 and the annual rate of horizontal crustal deformation in North China is about 4 ~5 mm. Horizontal crustal movement is a direct indication of the regional stress field. Therefore, by monitoring the time-sequence variation of horizontal crustal motion, it would be possible to investigate the change in the stress field, to analyze the tendency of seismicity and to determine the seismogenic zones.
文摘The aim of the research was to evaluate overall quality of introduction of hazard analysis and critical control points （HACCP） prerequisites and HACCP procedures in catering sector in Latvia to reveal common problems that can provoke food-borne infection outbreaks. Certain quantitative indicators were defined and analyzed to conclude about characteristic trends related to implementation of food safety legislation. The state＇s monitoring data on surveillance of catering establishments were used. Fulfillment of legislative requirements in about 6,000 catering establishments was evaluated during time period of 2004-2009. The results of investigation were obtained with help of statistical analyses using MS Excel computer program. The results of the research suggest that most of catering establishments （e.g., 83.6% during 2009） meet the hygiene requirements only partly. Non-conformities regarding HACCP-based self-control procedures were fixed during 49.2% of inspections. The research reveals characteristic shortcomings that are established from year to year, e.g., improper hygiene of premises （established during 30%-40% of inspections, depending on the year）, poor hygiene of technological equipment （established during 27%-37% of inspections）, poor personnel hygiene （established during 11%-22% of inspections）, inadequate competence of food service personnel （established during 10%-35% of inspections）, as well as non-observance of cleaning-disinfection procedures and technological parameters for food processing （established during 11%-25% of inspections, depending on the year）. Actual shortcomings can lead to both the direct and the indirect cross-contamination of food. On the base of the research, it was concluded that further detailed assessment of potential food safety risks is relevant to establish risk-based monitoring activities in catering sector.
文摘Human nuclear receptor hB1F is a novel member of the fushi tarazu factor Ⅰ subfamily of nuclear receptor superfamily. The studies about its homologous genes indicate that hB1F may play a key role in regulating the metabolic homeostasis of cholesterol. After obtaining the founder mice carrying the trausgeue of hblf by microiujectiou, each founder was mated to normal C57 mouse and the positive F1 by PCR identification of the same founder were iutercrossed within sisters and brothers to establish the trausgeuic mouse lineage. The results of F1, F2 and offspring of test cross identification showed that the widely expressed hb1f trausgeuic mouse lineage was established successfully in this study. The tissue morphology of the trausgeuic lineage was also analyzed preliminarily.
