In recent years, most of the drilling engineering accidents are caused by human error of judgment, which has much to do with the fact that technical experts and leaders can't get to know the site situation immedia...In recent years, most of the drilling engineering accidents are caused by human error of judgment, which has much to do with the fact that technical experts and leaders can't get to know the site situation immediately and miss the best time to deal with downhole anomalies. Along the general direction of information-based drilling, relying on the continuous improvement of information construction and the maturing of engineering automatic warning software, in August 2016, our company was the first pilot unit of Great Wall Drilling to establish a remote technical support center. The remote real-time monitoring of drilling parameters, data entry and analysis of EISS system, engineering simulation calculation and analysis software and other modules were applied to construct a remote technical support system for drilling engineering, which achieved the control objectives of "pre-prediction", "in-process control" and "post-analysis", promoted the continuous improvement of ROP, steadily reduced the accident complexity rate, and promoted the overall speed-up and efficiency improvement of all well teams of the Company. At the same time, combining with my own work practice, the author puts forward optimization and expansion methods for the problems and development direction in the operation of the remote support system, hoping to provide reference and reference for more people in the industry.展开更多
The influencing factors of the equipment support activity process have the characteristics of nonlinearity, high dimension, many constraints, random uncertainty and fuzzy uncertainty. Monte Carlo method can solve the ...The influencing factors of the equipment support activity process have the characteristics of nonlinearity, high dimension, many constraints, random uncertainty and fuzzy uncertainty. Monte Carlo method can solve the above problems commendably. This paper analyzes the main equipment support activity process and establishes the sampling plan and simulation model of the medium maintenance process based on Monte Carlo method, and the simulation result verifies a fact that the medium maintenance time can be effectively reduced when parallel operation on some procedures is used. It has a practical value and can give good advice to achieve the capability of equipment supportability.展开更多
The core of grid technology is just to solve the problem of resource share and to eliminate information island and resource island. Thus, it is a perfect approach to apply the grid technology to armored equipment mate...The core of grid technology is just to solve the problem of resource share and to eliminate information island and resource island. Thus, it is a perfect approach to apply the grid technology to armored equipment materiel support. Firstly, the military and function demands of armored equipment materiel support grid are analyzed. Besides, according to the function demand, the system structure of armored equipment materiel support grid is designed. Finally, the organizational structure of armored equipment materiel support grid is established in this paper based on actual armored equipment materiel support.展开更多
A secondary-cooling-segment electromagnetic stirring(S-EMS)experiment was performed at 150 A and 4 Hz to evaluate the effect of S-EMS on solidification characterization near the white band.The upper and lower parts of...A secondary-cooling-segment electromagnetic stirring(S-EMS)experiment was performed at 150 A and 4 Hz to evaluate the effect of S-EMS on solidification characterization near the white band.The upper and lower parts of the white band exhibited average secondary dendritic arm spacing of 205.4 and 214.4μm,respectively.The S-EMS operation resulted in large Lorentz forces and cooling intensity,which could produce additional dendritic arms with low carbon concentrations,leading to local negative segregation.Moreover,a 3D flow-temperature-magnetic coupling numerical model was established.The results revealed that the magnetic induction intensity and Lorentz force were symmetrically distributed along rollers S1 and S2.The average velocity magnitude increased by approximately 42.52%,58.69%,and 64.11%for liquid fractions of 0.7,0.8,and 0.9,respectively.During the S-EMS operation,the Lorentz force may alter the velocity of the solidification front and promote the dissipation of superheat.Additionally,the influence of S-EMS on grain nucleation and growth was investigated using Gibbs free energy theory and component undercooling.Furthermore,a formation model for the white band was established,and the mechanism of white band formation was elucidated according to the changes in the solute-enriched layer,solute precipitation,and diffusion.展开更多
A mathematical model of the decarburization reaction zone was established for the Ruhrstahl–Heraeus (RH) forced oxygen blowing decarburization process by Matlab R2022b software. For the problem of inaccurate predicti...A mathematical model of the decarburization reaction zone was established for the Ruhrstahl–Heraeus (RH) forced oxygen blowing decarburization process by Matlab R2022b software. For the problem of inaccurate prediction due to the large variation range of oxygen absorption rate under different process conditions, we statistically analyzed the main factors affecting the oxygen absorption rate. The backpropagation neural network was used to train and predict the oxygen absorption rate and was used to calculate the RH decarburization reaction zone model. We designed and developed a mathematical modeling software with process control of decarburization in RH degasser, which can realize the change of operating process parameters in the dynamic prediction process. The optimized mathematical model has more than 95% of the furnaces whose absolute error in calculation of carbon content is within ± 5 × 10^(−6), more than 90% of the heats whose relative error in calculation of oxygen content is within ± 15%, and the average absolute error of calculation of oxygen content is 26.4 × 10^(−6). Finally, we studied the influence of oxygen blowing timing, oxygen blowing volume and initial oxygen content on the forced decarburization process.展开更多
BACKGROUND Inflammatory cytokines are associated with cancer prognosis,but their specific role in cholangiocarcinoma remains poorly understood.The lymphocyte to C-reactive protein ratio(LCR),a novel inflammatory-nutri...BACKGROUND Inflammatory cytokines are associated with cancer prognosis,but their specific role in cholangiocarcinoma remains poorly understood.The lymphocyte to C-reactive protein ratio(LCR),a novel inflammatory-nutritional biomarker,has demonstrated predictive value in gastrointestinal cancers;however,its clinical relevance in cholangiocarcinoma has not been investigated.AIM To validate the LCR as an independent prognostic factor for overall survival(OS),surgical site infection(SSI),and length of hospital stay in patients with resectable cholangiocarcinoma.METHODS We conducted a retrospective analysis of 76 patients with cholangiocarcinoma who underwent radical surgery between 2008 and 2013.The preoperative LCR was calculated as the lymphocyte count divided by C-reactive protein level,using a cutoff value of 180.Univariate and multivariate logistic regression analyses were performed to evaluate factors associated with SSI and hospitalization duration,while Kaplan-Meier survival curves and Cox proportional hazards models were used to assess predictors of OS.RESULTS Patients in the low LCR group was significantly associated with several adverse clinical outcomes:A shorter median OS(14.93 months vs 46.67 months;P=0.022);a 4.5-fold increased risk of prolonged hospitalization(P=0.007);and a higher incidence of SSI(odds ratio=4.41,P=0.045).Multivariate analysis confirmed that LCR was an independent predictor of OS[hazard ratio(HR)=3.204,P=0.002],SSI,and hospitalization duration.Additionally,R0 resection(HR=3.546,P=0.002)and advanced tumor-node-metastasis stage(HR=2.016,P=0.035)were identified as independent prognostic factors for OS.CONCLUSION In this retrospective study,preoperative LCR is a cost-effective and practical biomarker that independently predicts OS,postoperative complications,and hospitalization duration in patients with resectable cholangiocarcinoma,thereby facilitating more precise patient stratification.展开更多
Thirty years ago, the analysis of longwall pillar stability(ALPS) inaugurated a new era in coal pillar design.ALPS was the first empirical pillar design technique to consider the abutment loads that arise from full ex...Thirty years ago, the analysis of longwall pillar stability(ALPS) inaugurated a new era in coal pillar design.ALPS was the first empirical pillar design technique to consider the abutment loads that arise from full extraction, and the first to be calibrated using an extensive database of longwall mining case histories.ALPS was followed by the analysis of retreat mining stability(ARMPS) and the analysis of multiple seam stability(AMSS). These methods incorporated other innovations, including the coal mine roof rating(CMRR), the Mark-Bieniawski pillar strength formula, and the pressure arch loading model. They also built upon ever larger case history databases and employed more sophisticated statistical methods.Today, these empirical methods are used in nearly every underground coal mine in the US. However,the piecemeal manner in which these methods have evolved resulted in some weaknesses. For example,in certain situations, it may not be obvious which program is the best to use. Other times the results from the different programs are not entirely consistent with each other. The programs have also not been updated for several years, and some changes were necessary to keep pace with new developments in mining practice. The analysis of coal pillar stability(ACPS) now integrates all three of the older software packages into a single pillar design framework. ACPS also incorporates the latest research findings in the field of pillar design, including an expanded multiple seam case history data base and a new method to evaluate room and pillar panels containing multiple rows of pillars left in place during pillar recovery.ACPS also includes updated guidance and warnings for users and features upgraded help files and graphics.展开更多
Accident tolerant fuel(ATF) for the light water reactor has gained wide attentions after the Fukushima accident. To enhance the accident-tolerance of the nuclear system, one strategy is to modify the Zr-based alloy cl...Accident tolerant fuel(ATF) for the light water reactor has gained wide attentions after the Fukushima accident. To enhance the accident-tolerance of the nuclear system, one strategy is to modify the Zr-based alloy cladding surface with advanced ceramic coating. In this work, monolithic and dense Cr_2AlC coating has been synthesized by magnetron sputtering. The as-grown Cr_2AlC coating exhibits good chemical compatibility with Zr-based alloy substrate as well as mechanical integrity under both pull-off and scratch tests. The coating system also presents moderate thermochemical compatibility at 800℃ but degrades above 1000℃ under simulated loss-of-coolant accident(LOCA) conditions.展开更多
A simple powder forging process was presented herein to fabricate an Fe-14 Cr-4.5 Al-2 W-0.4 Ti-0.5 Y_(2)O_(3)ODS Fe Cr Al alloy.The forged alloy exhibits a high density that exceeds 97%of the theoretical density.The ...A simple powder forging process was presented herein to fabricate an Fe-14 Cr-4.5 Al-2 W-0.4 Ti-0.5 Y_(2)O_(3)ODS Fe Cr Al alloy.The forged alloy exhibits a high density that exceeds 97%of the theoretical density.The ODS alloy was investigated in terms of the residual porosity,morphology and phase structure of oxide nanoparticles,impact toughness and tensile properties.It was found that refined grains were obtained during powder forging.A residual porosity less than 1.1%has no impact on the precipitation of oxide nanoparticles.The average diameter of the oxide particles is 7.99 nm,with a number density of 2.75×10^(22)m^(-3).Almost all of the oxides are identified as orthorhombic YAl O3 particles.The refined grains and uniformly distributed oxide nanoparticles enable the alloy to show excellent mechanical strength and ductility below 700℃,and enable the ductile-to-brittle transition temperature to be close to room temperature.However,a slight decrease in strength at 1000℃and the Charpy upper shelf energy has been suggested to be due to the residual porosity.These results indicate that powder forging can be used as a promising technique for the fabrication of ODS alloys.展开更多
The paper deals with systems suffered from gradual deterioration. To avoid functional failures and disastrous consequences, such systems should be monitored and preventively maintained. And to promote the maintenance ...The paper deals with systems suffered from gradual deterioration. To avoid functional failures and disastrous consequences, such systems should be monitored and preventively maintained. And to promote the maintenance effectiveness, an unequal time-interval maintenance policy was brought forward to substitute fixedinterval preventive maintenance strategy. At the same time, preventive and corrective maintenance actions are both assumed to be imperfect, and their impact on the system is expressed by the increment of failure rate. The case study shown that the unequal time-interval maintenance policy proposed in the paper is of help to promote the availability of the system.展开更多
Longwall mining has existed in Utah for more than half a century.Much of this mining occurred at depths of cover that significantly exceed those encountered by most other US longwall operations.Deep cover causes high ...Longwall mining has existed in Utah for more than half a century.Much of this mining occurred at depths of cover that significantly exceed those encountered by most other US longwall operations.Deep cover causes high ground stress,which can combine with geology to create a coal burst hazard.Nearly every longwall mine operating within the Utah’s Book Cliffs coalfield has been affected by coal bursts.Pillar design has been a key component in the burst control strategies employed by mines in the Book Cliffs.Historically,most longwall mines employed double-use two-entry yield pillar gates.Double-use signifies that the gate system serves first as the headgate,and then later serves as the tailgate for the adjacent panel.After the 1996 burst fatality at the Aberdeen Mine,the inter-panel barrier design was introduced.In this layout,a wide barrier pillar protects each longwall panel from the previously mined panel,and each gate system is used just once.This paper documents the deep cover longwall mining conducted with each type of pillar design,together with the associated coal burst experience.Each of the six longwall mining complexes in the Book Cliffs having a coal burst history is described on a panel-by-panel basis.The analysis shows that where the mining depth exceeded 450 m,each design has been employed for about 38000 total m of longwall panel extraction.The double-use yield pillar design has been used primarily at depths less than 600 m,however,while the inter-panel barrier design has been used mainly at depths exceeding 600 m.Despite its greater depth of use,the inter-panel barrier gate design has been associated with about one-third as much face region burst activity as the double-use yield pillar design.展开更多
Using the data collected over the Southern Great Plains ARM site from 2006 to 2010, the surface Active Remote Sensing of Cloud （ARSCL） and CloudSat-CALIPSO satellite （CC） retrievals of total cloud and six specifie...Using the data collected over the Southern Great Plains ARM site from 2006 to 2010, the surface Active Remote Sensing of Cloud （ARSCL） and CloudSat-CALIPSO satellite （CC） retrievals of total cloud and six specified cloud types [low, midlow （ML）, high-mid-low （HML）, mid, high-mid （HM） and high] were compared in terms of cloud fraction （CF）, cloud-base height （CBH）, cloud-top height （CTH） and cloud thickness （CT）, on different temporal scales, to identify their respective advantages and limitations. Good agreement between the two methods was exhibited in the total CF. However, large discrepancies were found between the cloud distributions of the two methods at a high （240-m） vertical grid spacing. Compared to the satellites, ARSCL retrievals detected more boundary layer clouds, while they underestimated high clouds. In terms of the six specific cloud types, more low- and mid-level clouds but less HML- and high-level clouds were detected by ARSCL than by CC. In contrast, the ARSCL retrievals of ML- and HM-level clouds agreed more closely with the estimations from the CC product. Lower CBHs tended to be reported by the surface data for low-, ML- and HML-level clouds; however, higher CTHs were often recorded by the satellite product for HML-, HM- and high-level clouds. The mean CTs for low- and ML-level cloud were similar between the two products; however, the mean CTs for HML-, mid-, HM- and high-level clouds from ARSCL were smaller than those from CC.展开更多
Time for single vehicle combat preparation(TSVCP) is an important characteristic parameter for the operational support feature of armored vehicle. During the development phase, how to validate the TSVCP of armored veh...Time for single vehicle combat preparation(TSVCP) is an important characteristic parameter for the operational support feature of armored vehicle. During the development phase, how to validate the TSVCP of armored vehicle through analytic method is a difficult issue in analysis and validation of vehicle supportability.This paper uses Monte Carlo approach and builds a working model for single vehicle combat preparation(SVCP)of armored vehicle, thus realizes the prediction and analysis of the TSVCP of armored vehicle, and finally validates the effectiveness of the approach by example.展开更多
A dynamic parallel forecasting model is proposed, which is based on the problem of current forecasting models and their combined model. According to the process of the model, the fuzzy C-means clustering algorithm is ...A dynamic parallel forecasting model is proposed, which is based on the problem of current forecasting models and their combined model. According to the process of the model, the fuzzy C-means clustering algorithm is improved in outliers operation and distance in the clusters and among the clusters. Firstly, the input data sets are optimized and their coherence is ensured, the region scale algorithm is modified and non-isometric multi scale region fuzzy time series model is built. At the same time, the particle swarm optimization algorithm about the particle speed, location and inertia weight value is improved, this method is used to optimize the parameters of support vector machine, construct the combined forecast model, build the dynamic parallel forecast model, and calculate the dynamic weight values and regard the product of the weight value and forecast value to be the final forecast values. At last, the example shows the improved forecast model is effective and accurate.展开更多
Cross-sectional homogenization for full-core calculations of small and complex reactor configurations,such as research reactors,has been recently recognized as an interesting and challenging topic.This paper presents ...Cross-sectional homogenization for full-core calculations of small and complex reactor configurations,such as research reactors,has been recently recognized as an interesting and challenging topic.This paper presents the development of a PARCS/Serpent model for the neutronics analysis of a research reactor type TRIGA Mark-II loaded with Russian VVR-M2 fuel(known as the Dalat Nuclear Research Reactor or DNRR).The full-scale DNRR model and a supercell model for a shim/safety rod and its surrounding fuel bundles with the Monte Carlo code Serpent 2 were proposed to generate homogenized fewgroup cross sections for full-core diffusion calculations with PARCS.The full-scale DNRR model with Serpent 2 was also utilized as a reference to verify the PARCS/Serpent calculations.Comparison of the effective neutron multiplication factors,radial and axial core power distributions,and control rod worths showed a generally good agreement between PARCS and Serpent 2.In addition,the discrepancies between the PARCS and Serpent 2 results are also discussed.Consequently,the results indicate the applicability of the PARCS/Serpent model for further steady state and transient analyses of the DNRR.展开更多
文摘In recent years, most of the drilling engineering accidents are caused by human error of judgment, which has much to do with the fact that technical experts and leaders can't get to know the site situation immediately and miss the best time to deal with downhole anomalies. Along the general direction of information-based drilling, relying on the continuous improvement of information construction and the maturing of engineering automatic warning software, in August 2016, our company was the first pilot unit of Great Wall Drilling to establish a remote technical support center. The remote real-time monitoring of drilling parameters, data entry and analysis of EISS system, engineering simulation calculation and analysis software and other modules were applied to construct a remote technical support system for drilling engineering, which achieved the control objectives of "pre-prediction", "in-process control" and "post-analysis", promoted the continuous improvement of ROP, steadily reduced the accident complexity rate, and promoted the overall speed-up and efficiency improvement of all well teams of the Company. At the same time, combining with my own work practice, the author puts forward optimization and expansion methods for the problems and development direction in the operation of the remote support system, hoping to provide reference and reference for more people in the industry.
基金the Special Research Fund for the Research on Armored Vehicle Supportability Requirement Analysis(No.51319050302)
文摘The influencing factors of the equipment support activity process have the characteristics of nonlinearity, high dimension, many constraints, random uncertainty and fuzzy uncertainty. Monte Carlo method can solve the above problems commendably. This paper analyzes the main equipment support activity process and establishes the sampling plan and simulation model of the medium maintenance process based on Monte Carlo method, and the simulation result verifies a fact that the medium maintenance time can be effectively reduced when parallel operation on some procedures is used. It has a practical value and can give good advice to achieve the capability of equipment supportability.
文摘The core of grid technology is just to solve the problem of resource share and to eliminate information island and resource island. Thus, it is a perfect approach to apply the grid technology to armored equipment materiel support. Firstly, the military and function demands of armored equipment materiel support grid are analyzed. Besides, according to the function demand, the system structure of armored equipment materiel support grid is designed. Finally, the organizational structure of armored equipment materiel support grid is established in this paper based on actual armored equipment materiel support.
基金supported by the National Natural Science Foundation of China(No.51774031)the Project funded by China Postdoctoral Science Foundation(No.2023M730230).
文摘A secondary-cooling-segment electromagnetic stirring(S-EMS)experiment was performed at 150 A and 4 Hz to evaluate the effect of S-EMS on solidification characterization near the white band.The upper and lower parts of the white band exhibited average secondary dendritic arm spacing of 205.4 and 214.4μm,respectively.The S-EMS operation resulted in large Lorentz forces and cooling intensity,which could produce additional dendritic arms with low carbon concentrations,leading to local negative segregation.Moreover,a 3D flow-temperature-magnetic coupling numerical model was established.The results revealed that the magnetic induction intensity and Lorentz force were symmetrically distributed along rollers S1 and S2.The average velocity magnitude increased by approximately 42.52%,58.69%,and 64.11%for liquid fractions of 0.7,0.8,and 0.9,respectively.During the S-EMS operation,the Lorentz force may alter the velocity of the solidification front and promote the dissipation of superheat.Additionally,the influence of S-EMS on grain nucleation and growth was investigated using Gibbs free energy theory and component undercooling.Furthermore,a formation model for the white band was established,and the mechanism of white band formation was elucidated according to the changes in the solute-enriched layer,solute precipitation,and diffusion.
基金supported by the Central Government Guides Local Science and Technology Development Foundation(No.2023JH6/100100046)the Project funded by China Postdoctoral Science Foundation(No.2023M730230).
文摘A mathematical model of the decarburization reaction zone was established for the Ruhrstahl–Heraeus (RH) forced oxygen blowing decarburization process by Matlab R2022b software. For the problem of inaccurate prediction due to the large variation range of oxygen absorption rate under different process conditions, we statistically analyzed the main factors affecting the oxygen absorption rate. The backpropagation neural network was used to train and predict the oxygen absorption rate and was used to calculate the RH decarburization reaction zone model. We designed and developed a mathematical modeling software with process control of decarburization in RH degasser, which can realize the change of operating process parameters in the dynamic prediction process. The optimized mathematical model has more than 95% of the furnaces whose absolute error in calculation of carbon content is within ± 5 × 10^(−6), more than 90% of the heats whose relative error in calculation of oxygen content is within ± 15%, and the average absolute error of calculation of oxygen content is 26.4 × 10^(−6). Finally, we studied the influence of oxygen blowing timing, oxygen blowing volume and initial oxygen content on the forced decarburization process.
基金Supported by National Natural Science Foundation of China,No.82170412.
文摘BACKGROUND Inflammatory cytokines are associated with cancer prognosis,but their specific role in cholangiocarcinoma remains poorly understood.The lymphocyte to C-reactive protein ratio(LCR),a novel inflammatory-nutritional biomarker,has demonstrated predictive value in gastrointestinal cancers;however,its clinical relevance in cholangiocarcinoma has not been investigated.AIM To validate the LCR as an independent prognostic factor for overall survival(OS),surgical site infection(SSI),and length of hospital stay in patients with resectable cholangiocarcinoma.METHODS We conducted a retrospective analysis of 76 patients with cholangiocarcinoma who underwent radical surgery between 2008 and 2013.The preoperative LCR was calculated as the lymphocyte count divided by C-reactive protein level,using a cutoff value of 180.Univariate and multivariate logistic regression analyses were performed to evaluate factors associated with SSI and hospitalization duration,while Kaplan-Meier survival curves and Cox proportional hazards models were used to assess predictors of OS.RESULTS Patients in the low LCR group was significantly associated with several adverse clinical outcomes:A shorter median OS(14.93 months vs 46.67 months;P=0.022);a 4.5-fold increased risk of prolonged hospitalization(P=0.007);and a higher incidence of SSI(odds ratio=4.41,P=0.045).Multivariate analysis confirmed that LCR was an independent predictor of OS[hazard ratio(HR)=3.204,P=0.002],SSI,and hospitalization duration.Additionally,R0 resection(HR=3.546,P=0.002)and advanced tumor-node-metastasis stage(HR=2.016,P=0.035)were identified as independent prognostic factors for OS.CONCLUSION In this retrospective study,preoperative LCR is a cost-effective and practical biomarker that independently predicts OS,postoperative complications,and hospitalization duration in patients with resectable cholangiocarcinoma,thereby facilitating more precise patient stratification.
文摘Thirty years ago, the analysis of longwall pillar stability(ALPS) inaugurated a new era in coal pillar design.ALPS was the first empirical pillar design technique to consider the abutment loads that arise from full extraction, and the first to be calibrated using an extensive database of longwall mining case histories.ALPS was followed by the analysis of retreat mining stability(ARMPS) and the analysis of multiple seam stability(AMSS). These methods incorporated other innovations, including the coal mine roof rating(CMRR), the Mark-Bieniawski pillar strength formula, and the pressure arch loading model. They also built upon ever larger case history databases and employed more sophisticated statistical methods.Today, these empirical methods are used in nearly every underground coal mine in the US. However,the piecemeal manner in which these methods have evolved resulted in some weaknesses. For example,in certain situations, it may not be obvious which program is the best to use. Other times the results from the different programs are not entirely consistent with each other. The programs have also not been updated for several years, and some changes were necessary to keep pace with new developments in mining practice. The analysis of coal pillar stability(ACPS) now integrates all three of the older software packages into a single pillar design framework. ACPS also incorporates the latest research findings in the field of pillar design, including an expanded multiple seam case history data base and a new method to evaluate room and pillar panels containing multiple rows of pillars left in place during pillar recovery.ACPS also includes updated guidance and warnings for users and features upgraded help files and graphics.
基金supported by the National Natural Science Foundation of China under Grant Nos. 51402311 and 51772302the National Key R&D Program of China under Grant No. 2017YFB0703201
文摘Accident tolerant fuel(ATF) for the light water reactor has gained wide attentions after the Fukushima accident. To enhance the accident-tolerance of the nuclear system, one strategy is to modify the Zr-based alloy cladding surface with advanced ceramic coating. In this work, monolithic and dense Cr_2AlC coating has been synthesized by magnetron sputtering. The as-grown Cr_2AlC coating exhibits good chemical compatibility with Zr-based alloy substrate as well as mechanical integrity under both pull-off and scratch tests. The coating system also presents moderate thermochemical compatibility at 800℃ but degrades above 1000℃ under simulated loss-of-coolant accident(LOCA) conditions.
基金financially supported by National Defense Science and Technology Industry Nuclear Material Technology Innovation Center Project(No.ICNM-2020-ZH-17)。
文摘A simple powder forging process was presented herein to fabricate an Fe-14 Cr-4.5 Al-2 W-0.4 Ti-0.5 Y_(2)O_(3)ODS Fe Cr Al alloy.The forged alloy exhibits a high density that exceeds 97%of the theoretical density.The ODS alloy was investigated in terms of the residual porosity,morphology and phase structure of oxide nanoparticles,impact toughness and tensile properties.It was found that refined grains were obtained during powder forging.A residual porosity less than 1.1%has no impact on the precipitation of oxide nanoparticles.The average diameter of the oxide particles is 7.99 nm,with a number density of 2.75×10^(22)m^(-3).Almost all of the oxides are identified as orthorhombic YAl O3 particles.The refined grains and uniformly distributed oxide nanoparticles enable the alloy to show excellent mechanical strength and ductility below 700℃,and enable the ductile-to-brittle transition temperature to be close to room temperature.However,a slight decrease in strength at 1000℃and the Charpy upper shelf energy has been suggested to be due to the residual porosity.These results indicate that powder forging can be used as a promising technique for the fabrication of ODS alloys.
文摘The paper deals with systems suffered from gradual deterioration. To avoid functional failures and disastrous consequences, such systems should be monitored and preventively maintained. And to promote the maintenance effectiveness, an unequal time-interval maintenance policy was brought forward to substitute fixedinterval preventive maintenance strategy. At the same time, preventive and corrective maintenance actions are both assumed to be imperfect, and their impact on the system is expressed by the increment of failure rate. The case study shown that the unequal time-interval maintenance policy proposed in the paper is of help to promote the availability of the system.
文摘Longwall mining has existed in Utah for more than half a century.Much of this mining occurred at depths of cover that significantly exceed those encountered by most other US longwall operations.Deep cover causes high ground stress,which can combine with geology to create a coal burst hazard.Nearly every longwall mine operating within the Utah’s Book Cliffs coalfield has been affected by coal bursts.Pillar design has been a key component in the burst control strategies employed by mines in the Book Cliffs.Historically,most longwall mines employed double-use two-entry yield pillar gates.Double-use signifies that the gate system serves first as the headgate,and then later serves as the tailgate for the adjacent panel.After the 1996 burst fatality at the Aberdeen Mine,the inter-panel barrier design was introduced.In this layout,a wide barrier pillar protects each longwall panel from the previously mined panel,and each gate system is used just once.This paper documents the deep cover longwall mining conducted with each type of pillar design,together with the associated coal burst experience.Each of the six longwall mining complexes in the Book Cliffs having a coal burst history is described on a panel-by-panel basis.The analysis shows that where the mining depth exceeded 450 m,each design has been employed for about 38000 total m of longwall panel extraction.The double-use yield pillar design has been used primarily at depths less than 600 m,however,while the inter-panel barrier design has been used mainly at depths exceeding 600 m.Despite its greater depth of use,the inter-panel barrier gate design has been associated with about one-third as much face region burst activity as the double-use yield pillar design.
基金supported by the National Natural Science Foundation of China(Grant Nos.61327810,41275039,41675033,and 91337214)
文摘Using the data collected over the Southern Great Plains ARM site from 2006 to 2010, the surface Active Remote Sensing of Cloud （ARSCL） and CloudSat-CALIPSO satellite （CC） retrievals of total cloud and six specified cloud types [low, midlow （ML）, high-mid-low （HML）, mid, high-mid （HM） and high] were compared in terms of cloud fraction （CF）, cloud-base height （CBH）, cloud-top height （CTH） and cloud thickness （CT）, on different temporal scales, to identify their respective advantages and limitations. Good agreement between the two methods was exhibited in the total CF. However, large discrepancies were found between the cloud distributions of the two methods at a high （240-m） vertical grid spacing. Compared to the satellites, ARSCL retrievals detected more boundary layer clouds, while they underestimated high clouds. In terms of the six specific cloud types, more low- and mid-level clouds but less HML- and high-level clouds were detected by ARSCL than by CC. In contrast, the ARSCL retrievals of ML- and HM-level clouds agreed more closely with the estimations from the CC product. Lower CBHs tended to be reported by the surface data for low-, ML- and HML-level clouds; however, higher CTHs were often recorded by the satellite product for HML-, HM- and high-level clouds. The mean CTs for low- and ML-level cloud were similar between the two products; however, the mean CTs for HML-, mid-, HM- and high-level clouds from ARSCL were smaller than those from CC.
文摘Time for single vehicle combat preparation(TSVCP) is an important characteristic parameter for the operational support feature of armored vehicle. During the development phase, how to validate the TSVCP of armored vehicle through analytic method is a difficult issue in analysis and validation of vehicle supportability.This paper uses Monte Carlo approach and builds a working model for single vehicle combat preparation(SVCP)of armored vehicle, thus realizes the prediction and analysis of the TSVCP of armored vehicle, and finally validates the effectiveness of the approach by example.
基金supported by the National Defense Preliminary Research Program of China(A157167)the National Defense Fundamental of China(9140A19030314JB35275)
文摘A dynamic parallel forecasting model is proposed, which is based on the problem of current forecasting models and their combined model. According to the process of the model, the fuzzy C-means clustering algorithm is improved in outliers operation and distance in the clusters and among the clusters. Firstly, the input data sets are optimized and their coherence is ensured, the region scale algorithm is modified and non-isometric multi scale region fuzzy time series model is built. At the same time, the particle swarm optimization algorithm about the particle speed, location and inertia weight value is improved, this method is used to optimize the parameters of support vector machine, construct the combined forecast model, build the dynamic parallel forecast model, and calculate the dynamic weight values and regard the product of the weight value and forecast value to be the final forecast values. At last, the example shows the improved forecast model is effective and accurate.
基金the Ministry of Science and Technology of Vietnam(No.DTCB.06/18/VKHKTHN).
文摘Cross-sectional homogenization for full-core calculations of small and complex reactor configurations,such as research reactors,has been recently recognized as an interesting and challenging topic.This paper presents the development of a PARCS/Serpent model for the neutronics analysis of a research reactor type TRIGA Mark-II loaded with Russian VVR-M2 fuel(known as the Dalat Nuclear Research Reactor or DNRR).The full-scale DNRR model and a supercell model for a shim/safety rod and its surrounding fuel bundles with the Monte Carlo code Serpent 2 were proposed to generate homogenized fewgroup cross sections for full-core diffusion calculations with PARCS.The full-scale DNRR model with Serpent 2 was also utilized as a reference to verify the PARCS/Serpent calculations.Comparison of the effective neutron multiplication factors,radial and axial core power distributions,and control rod worths showed a generally good agreement between PARCS and Serpent 2.In addition,the discrepancies between the PARCS and Serpent 2 results are also discussed.Consequently,the results indicate the applicability of the PARCS/Serpent model for further steady state and transient analyses of the DNRR.
基金co-funded by the Key Project of the National Natural Science Foundation of China [grant number 42230609 and 41630425]the National Key Research and Development Plan projects [grant number 2022YFC3004101]
