Aircraft mechanical and electrical equipment maintenance major requires students to master the basic maintenance skills of aircraft airframe and engine, and it is a major that attaches importance to students' comp...Aircraft mechanical and electrical equipment maintenance major requires students to master the basic maintenance skills of aircraft airframe and engine, and it is a major that attaches importance to students' comprehensive ability. Under the traditional education mode, it is difficult for graduates majoring in aircraft mechanical and electrical equipment maintenance to adapt to their jobs quickly. Therefore, the teaching reform research of aircraft mechanical and electrical equipment maintenance major is put forward with job demand-oriented. By analyzing the deficiency of the traditional teaching mode and considering the job demand, this paper tries to reform the teaching mode in order to provide more excellent professionals for the society.展开更多
The “3·31” severe squall line event in eastern China was notable for its exceptional intensity and persistence,posing significant challenges to forecast accuracy. This study analyzed the maintenance stage of th...The “3·31” severe squall line event in eastern China was notable for its exceptional intensity and persistence,posing significant challenges to forecast accuracy. This study analyzed the maintenance stage of this event using highresolution convection-permitting numerical simulations, with a focus on vorticity budgets of the environmental flow, multiscale synoptic diagnostics, and Rotunno-Klemp-Weisman(RKW) theory. These analyses aimed to elucidate the mechanisms governing the morphological transition, the generation of associated convective gales, and the prolonged maintenance of the squall line event. The results show that the numerical simulation accurately reproduced the development and evolution of the squall line, particularly its location, with surface wind errors remaining within a reasonable range. The development of a mesoscale vortex modulated the dynamic and water vapor fields, providing favorable mesoscale environmental conditions for the organization and maintenance of the squall line. Vorticity budget analysis indicates that the divergence and tilting terms were the primary contributors to vorticity tendency. After the squall line entered Jiangxi Province, it exhibited a sharper leading edge and enhanced upward motion. Dry intrusion from the mid-toupper troposphere led to rapid downward momentum transfer at the meso-γ scale, thereby generating convective gales. In addition, the enhancement of the rear-inflow jet(RIJ) was related to the pressure difference between the interior and exterior of system, which resulted from the phase change of condensate within tilted updrafts. The RIJ was orthogonal to the squall line, causing it to transform from a linear into a bowing shape. Diagnosis based on the RKW theory underscore the important roles in both low-level and deep vertical wind shear in maintenaning the squall line. The ratios of the cold pool propagation velocity to the vertical wind shear were close to 1, which balanced with the ambient horizontal vorticity that allowed the convection to remain upright, thus sustaining the squall line's intensity for an extended period. In summary, the squall line event was sustained by a favorable environment created by the environmental vortex. The dry intrusion from the mid-to-upper troposphere and intensified RIJ resulted in the severe convective winds, while the balance between cold pool and ambient vertical wind shear promoted the system's prolonged maintenance. These findings provide an effective reference for the short-range forecasting of squall lines throughout their lifecycle.展开更多
With the sustained and rapid development of national economy in our country, as well as the quality of people's material life sustained steady growth in consumption level, the car is becoming more and more big, co...With the sustained and rapid development of national economy in our country, as well as the quality of people's material life sustained steady growth in consumption level, the car is becoming more and more big, continuous ownership of the main selling car brand quantity and automobile brand in our country has increased steadily, to promote the current our country modern commercial car maintenance and maintenance, rapid and sound development of the industry. Because these vehicles in the daily use of the process of maintenance in the process of continuous occurrence of a variety of new automotive mechanical failure, therefore, also greatly promoted the current China's modern automobile maintenance and maintenance technology service industry healthy and rapid development.展开更多
In this paper, a typical mei-yu front process with heavy rainfall from June 12 to 15 in 1998 is analyzed. The results show that the mei-yu front is a front system which consists of an iso-theta(e) dense area with stro...In this paper, a typical mei-yu front process with heavy rainfall from June 12 to 15 in 1998 is analyzed. The results show that the mei-yu front is a front system which consists of an iso-theta(e) dense area with strong horizontal gradient, a deep-convective cloud tower band, a passageway transporting warm and moist air flow from the summer monsoon surge in the mid and low levels to the south of the mei-yu front, and a migrating synoptic scale trough to the north of the mei-yu front, which transports cold and dry air southward in the mid and upper levels. The maintenance of the mei-yu front is realized by: (1) is a positive feedback between the moist physical process enhancing frontogenesis and the development of the strong convective system in front of the mei-yu front; (2) the sustaining system to the north of the mei-yu front which is a migrating synoptic scale trough transporting cold and dry air to the mei-yu front and positive vorticity to the mesoscale system in front of the mei-yu front.展开更多
The dynamic environments in riparian zones support a variety of life-history strategies, which constitute a fundamental mechanism for development and maintenance of biodiversity in riparian forest ecosystems. To demon...The dynamic environments in riparian zones support a variety of life-history strategies, which constitute a fundamental mechanism for development and maintenance of biodiversity in riparian forest ecosystems. To demonstrate the effect of life-history strategies on biodiversity, we investigated community-level diversity and its relationship to environmental variability in the riparian Populus euphratica forests of the Ejina Oasis. Communities were divided into 14 associations on the basis of their species impor- tance values. The Simpson＇s index, Shannon-Wiener index, Pielou＇s evenness index and the regional Whittaker＇s index were applied to calculate community diversity. An ordination of the sample plots was carried out by correspondence analysis （CA）. Biodiversity was relatively low across the entire study area, but there was high community diversity （flw = 8.09） due to the spatial heterogeneity of habitats in different plots. In addition, we investigated the relationship between biodiversity and several environmental factors, such as water availability, community components and soil conditions. We conclude that the heterogeneity of soil and water availability drives community diversity patterns in riparian zones and that community-level diversity favors the maintenance of species diversity in the P euphratica forests in the Ejina Oasis.展开更多
The thickest coal seam is 20 meters, and the thinnest one is generally 1 meter. In the process of coal mining, comprehensive mechanized equipment or other mining technology will be selected according to the thickness ...The thickest coal seam is 20 meters, and the thinnest one is generally 1 meter. In the process of coal mining, comprehensive mechanized equipment or other mining technology will be selected according to the thickness of coal seam. Therefore, in the process of mining coal mine, there are high requirements for the use of fully mechanized mining machinery and equipment. Coal mining enterprises should strengthen the research on the deficiencies in the use of fully mechanized mining machinery and equipment, and formulate scientific and reasonable improvement measures according to the actual situation of the enterprise, so as to continuously improve the mining efficiency of the coal mine and realize the high-quality development of the enterprise. In this paper, the author first studies the deficiencies in the use of fully mechanized mining machinery and equipment, and then discusses the reasons for the problems of fully mechanized mining machinery and equipment, and finally discusses and studies how to better maintain the fully mechanized mining machinery and equipment.展开更多
Telomeres are the structures that locate at the terminals of linear eukaryotic chromosomes. They can play essential roles in many cellular processes. The terminal location ofArabidopsis-type TTTAGGG tandem repeats wer...Telomeres are the structures that locate at the terminals of linear eukaryotic chromosomes. They can play essential roles in many cellular processes. The terminal location ofArabidopsis-type TTTAGGG tandem repeats were thought to be highly conserved. The terminal location of Ginkgo biloba L. consisting of TTTAGGG tandem repeats, were confirmed by Bal31 exonuclease degradation and Southern blotting. By comparing telomeric restriction fragment （TRF） lengths at different developmental stages from embryos to seedlings, a fluctuant tendency towards variation was found in these samples. The TRF length of embryos was also compared with that of embryonal calli and an upward trend was discovered in callus culture. The results suggest that there should be a telomerase mechanism or/and ALT mechanism for the maintenance of telomere length.展开更多
Tunnel boring machines require extensive maintenance and inspection effort to provide a high availability.The cutting tools of the cutting wheel must be changed timely upon reaching a critical condition.While one poss...Tunnel boring machines require extensive maintenance and inspection effort to provide a high availability.The cutting tools of the cutting wheel must be changed timely upon reaching a critical condition.While one possible maintenance strategy is to change tools only when it is absolutely necessary,tools can also be changed preventively to avoid further damages.Such different maintenance strategies influence the maintenance duration and the overall project performance.However,determine downtime related to a particular mainte-nance strategy is still a challenging task.This paper shows an analysis of the robustness to achieve the planned project performance of a maintenance strategy considering uncertainties of wear behavior of the cutting tools.A simulation based analysis is presented,imple-menting an empirical wear prediction model.Different strategies of maintenance planning are compared by performing a parameter vari-ation study including Monte-Carlo simulations.The maintenance costs are calculated and evaluated with respect to their robustness.Finally,an improved and robust maintenance strategy has been determined.展开更多
The spatial structure and temporal variations of the stationary wave anomalies in the upper troposphere during the Northern Hemisphere winter are studied with the ECMWF data of 1980— 1988 and PCA(principal component ...The spatial structure and temporal variations of the stationary wave anomalies in the upper troposphere during the Northern Hemisphere winter are studied with the ECMWF data of 1980— 1988 and PCA(principal component analysis)method.The vorticity source anomalies of the main teleconnection patterns are analyzed,and their roles in the maintenance of the stationary wave anomaly teleconnection patterns are investigated with the harotropic model.The results show that the anomalies of transient vorticity flux convergences tend to cancel the anomaly of vorticity sources generated by divergent winds.The stationary wave anomaly patterns caused by divergent wind anomalies only are very different from observations.However,if the anomalous transient vorticity flux convergences are also included in the vorticity sources,the simulated patterns will be greatly improved.展开更多
文摘Aircraft mechanical and electrical equipment maintenance major requires students to master the basic maintenance skills of aircraft airframe and engine, and it is a major that attaches importance to students' comprehensive ability. Under the traditional education mode, it is difficult for graduates majoring in aircraft mechanical and electrical equipment maintenance to adapt to their jobs quickly. Therefore, the teaching reform research of aircraft mechanical and electrical equipment maintenance major is put forward with job demand-oriented. By analyzing the deficiency of the traditional teaching mode and considering the job demand, this paper tries to reform the teaching mode in order to provide more excellent professionals for the society.
基金Jiangxi Meteorological Bureau Project (JXCX202304,JX2024Y01)Geological Disaster Prevention and Control Project of Jiangxi Provincial Department of Natural Resources(B360000030004)+1 种基金Key Research and Development Project of Jiangxi Province (20243BBH81005)Weather Review Project of China Meteorological Administration (FPZJ2025-066)。
文摘The “3·31” severe squall line event in eastern China was notable for its exceptional intensity and persistence,posing significant challenges to forecast accuracy. This study analyzed the maintenance stage of this event using highresolution convection-permitting numerical simulations, with a focus on vorticity budgets of the environmental flow, multiscale synoptic diagnostics, and Rotunno-Klemp-Weisman(RKW) theory. These analyses aimed to elucidate the mechanisms governing the morphological transition, the generation of associated convective gales, and the prolonged maintenance of the squall line event. The results show that the numerical simulation accurately reproduced the development and evolution of the squall line, particularly its location, with surface wind errors remaining within a reasonable range. The development of a mesoscale vortex modulated the dynamic and water vapor fields, providing favorable mesoscale environmental conditions for the organization and maintenance of the squall line. Vorticity budget analysis indicates that the divergence and tilting terms were the primary contributors to vorticity tendency. After the squall line entered Jiangxi Province, it exhibited a sharper leading edge and enhanced upward motion. Dry intrusion from the mid-toupper troposphere led to rapid downward momentum transfer at the meso-γ scale, thereby generating convective gales. In addition, the enhancement of the rear-inflow jet(RIJ) was related to the pressure difference between the interior and exterior of system, which resulted from the phase change of condensate within tilted updrafts. The RIJ was orthogonal to the squall line, causing it to transform from a linear into a bowing shape. Diagnosis based on the RKW theory underscore the important roles in both low-level and deep vertical wind shear in maintenaning the squall line. The ratios of the cold pool propagation velocity to the vertical wind shear were close to 1, which balanced with the ambient horizontal vorticity that allowed the convection to remain upright, thus sustaining the squall line's intensity for an extended period. In summary, the squall line event was sustained by a favorable environment created by the environmental vortex. The dry intrusion from the mid-to-upper troposphere and intensified RIJ resulted in the severe convective winds, while the balance between cold pool and ambient vertical wind shear promoted the system's prolonged maintenance. These findings provide an effective reference for the short-range forecasting of squall lines throughout their lifecycle.
文摘With the sustained and rapid development of national economy in our country, as well as the quality of people's material life sustained steady growth in consumption level, the car is becoming more and more big, continuous ownership of the main selling car brand quantity and automobile brand in our country has increased steadily, to promote the current our country modern commercial car maintenance and maintenance, rapid and sound development of the industry. Because these vehicles in the daily use of the process of maintenance in the process of continuous occurrence of a variety of new automotive mechanical failure, therefore, also greatly promoted the current China's modern automobile maintenance and maintenance technology service industry healthy and rapid development.
文摘In this paper, a typical mei-yu front process with heavy rainfall from June 12 to 15 in 1998 is analyzed. The results show that the mei-yu front is a front system which consists of an iso-theta(e) dense area with strong horizontal gradient, a deep-convective cloud tower band, a passageway transporting warm and moist air flow from the summer monsoon surge in the mid and low levels to the south of the mei-yu front, and a migrating synoptic scale trough to the north of the mei-yu front, which transports cold and dry air southward in the mid and upper levels. The maintenance of the mei-yu front is realized by: (1) is a positive feedback between the moist physical process enhancing frontogenesis and the development of the strong convective system in front of the mei-yu front; (2) the sustaining system to the north of the mei-yu front which is a migrating synoptic scale trough transporting cold and dry air to the mei-yu front and positive vorticity to the mesoscale system in front of the mei-yu front.
基金supported by the National Natural Science Foundation of China (No. 30570332)the 11th Five-Year Plan of the National Scientific and Technological Support Projects (2008BADB0B05)
文摘The dynamic environments in riparian zones support a variety of life-history strategies, which constitute a fundamental mechanism for development and maintenance of biodiversity in riparian forest ecosystems. To demonstrate the effect of life-history strategies on biodiversity, we investigated community-level diversity and its relationship to environmental variability in the riparian Populus euphratica forests of the Ejina Oasis. Communities were divided into 14 associations on the basis of their species impor- tance values. The Simpson＇s index, Shannon-Wiener index, Pielou＇s evenness index and the regional Whittaker＇s index were applied to calculate community diversity. An ordination of the sample plots was carried out by correspondence analysis （CA）. Biodiversity was relatively low across the entire study area, but there was high community diversity （flw = 8.09） due to the spatial heterogeneity of habitats in different plots. In addition, we investigated the relationship between biodiversity and several environmental factors, such as water availability, community components and soil conditions. We conclude that the heterogeneity of soil and water availability drives community diversity patterns in riparian zones and that community-level diversity favors the maintenance of species diversity in the P euphratica forests in the Ejina Oasis.
文摘The thickest coal seam is 20 meters, and the thinnest one is generally 1 meter. In the process of coal mining, comprehensive mechanized equipment or other mining technology will be selected according to the thickness of coal seam. Therefore, in the process of mining coal mine, there are high requirements for the use of fully mechanized mining machinery and equipment. Coal mining enterprises should strengthen the research on the deficiencies in the use of fully mechanized mining machinery and equipment, and formulate scientific and reasonable improvement measures according to the actual situation of the enterprise, so as to continuously improve the mining efficiency of the coal mine and realize the high-quality development of the enterprise. In this paper, the author first studies the deficiencies in the use of fully mechanized mining machinery and equipment, and then discusses the reasons for the problems of fully mechanized mining machinery and equipment, and finally discusses and studies how to better maintain the fully mechanized mining machinery and equipment.
文摘Telomeres are the structures that locate at the terminals of linear eukaryotic chromosomes. They can play essential roles in many cellular processes. The terminal location ofArabidopsis-type TTTAGGG tandem repeats were thought to be highly conserved. The terminal location of Ginkgo biloba L. consisting of TTTAGGG tandem repeats, were confirmed by Bal31 exonuclease degradation and Southern blotting. By comparing telomeric restriction fragment （TRF） lengths at different developmental stages from embryos to seedlings, a fluctuant tendency towards variation was found in these samples. The TRF length of embryos was also compared with that of embryonal calli and an upward trend was discovered in callus culture. The results suggest that there should be a telomerase mechanism or/and ALT mechanism for the maintenance of telomere length.
文摘Tunnel boring machines require extensive maintenance and inspection effort to provide a high availability.The cutting tools of the cutting wheel must be changed timely upon reaching a critical condition.While one possible maintenance strategy is to change tools only when it is absolutely necessary,tools can also be changed preventively to avoid further damages.Such different maintenance strategies influence the maintenance duration and the overall project performance.However,determine downtime related to a particular mainte-nance strategy is still a challenging task.This paper shows an analysis of the robustness to achieve the planned project performance of a maintenance strategy considering uncertainties of wear behavior of the cutting tools.A simulation based analysis is presented,imple-menting an empirical wear prediction model.Different strategies of maintenance planning are compared by performing a parameter vari-ation study including Monte-Carlo simulations.The maintenance costs are calculated and evaluated with respect to their robustness.Finally,an improved and robust maintenance strategy has been determined.
文摘The spatial structure and temporal variations of the stationary wave anomalies in the upper troposphere during the Northern Hemisphere winter are studied with the ECMWF data of 1980— 1988 and PCA(principal component analysis)method.The vorticity source anomalies of the main teleconnection patterns are analyzed,and their roles in the maintenance of the stationary wave anomaly teleconnection patterns are investigated with the harotropic model.The results show that the anomalies of transient vorticity flux convergences tend to cancel the anomaly of vorticity sources generated by divergent winds.The stationary wave anomaly patterns caused by divergent wind anomalies only are very different from observations.However,if the anomalous transient vorticity flux convergences are also included in the vorticity sources,the simulated patterns will be greatly improved.
