当前,就业多元化的背景下,结构性矛盾是当前高校毕业生就业面临的主要问题之一。高校专业设置与市场需求不匹配,导致部分专业的毕业生供不应求,而另一些专业则供过于求。受年轻人就业观念固化和农村岗位结构单一的影响,毕业大学生很少...当前,就业多元化的背景下,结构性矛盾是当前高校毕业生就业面临的主要问题之一。高校专业设置与市场需求不匹配,导致部分专业的毕业生供不应求,而另一些专业则供过于求。受年轻人就业观念固化和农村岗位结构单一的影响,毕业大学生很少有人愿意在农村就业。实施乡村振兴战略是新时代中国特色社会主义的重大决策部署,而乡村振兴战略需要大量高素质人才的支持,大学生具备丰富的知识和技能,正是推动农村发展的关键力量,怎样实现乡村振兴与大学生就业的良性互动,成为就业政策改革的主要关键目标。基于此,本文先是对“BNF”(Be New Famer)“新农人”培养平台进行理论研究,其次分析“BNF”(Be New Famer)“新农人”培养平台的必要性,最后探究“BNF”(Be New Famer)“新农人”培养平台的有效策略,旨在就业多元化的背景下,促进农业农村的就业模式现代化,助力乡村振兴。展开更多
As potential wave-transparent materials applied at high temperatures, 3D BNf/Si3N4 ceramic matrix composites were prepared by low pressure chemical vapor infiltration or deposition（LPCVI/CVD） process from SiCl4-NH3-...As potential wave-transparent materials applied at high temperatures, 3D BNf/Si3N4 ceramic matrix composites were prepared by low pressure chemical vapor infiltration or deposition（LPCVI/CVD） process from SiCl4-NH3-H2-Ar gas precursor at 800 oC. The densification process, microstructure and dielectric properties of 3D BNf/Si3N4 composites were investigated. The results indicated that 3D BNf/Si3N4 was successfully fabricated by LPCVI/CVD, with final open porosity of 2.37% and density of 1.89 g/cm3. Densification kinetics of 3D BNf/Si3N4 is a typical exponential pattern. The Si3N4 matrix was uniformly infiltrated into porous BNf preform. The deposited Si3N4 matrix was amorphous by XRD analysis. Introduction of BN fiber into Si3N4 ceramic lowered the permittivity of Si3N4. The fabricated BNf/Si3N4 composites possess low permittivity of 3.68 and low dielectric loss of lower than 0.01, which are independent of temperature below400 oC. Transmission coefficient of BNf/Si3N4 composite is 0.57 and keeps stable below 400 oC. BNf/Si3N4 can be fabricated at low temperature and may be candidates for the microwave transparent materials.展开更多
Land degradation,unbalanced nutrition,change in climate and its extreme variability are the factors affecting the sustainability of agriculture and food security.In North-west Pakistan,more than 50%of the cultivated a...Land degradation,unbalanced nutrition,change in climate and its extreme variability are the factors affecting the sustainability of agriculture and food security.In North-west Pakistan,more than 50%of the cultivated area is rain-fed and the crop productivity is low.Conservation agriculture reduces greenhouse gas emissions by enhancing soil carbon sequestration and then improved soil fertility,WUE and crop productivity.A field experiment展开更多
Meta-modelling plays an important role in model driven software development. In this paper, a graphic exten- sion of BNF （GEBNF） is proposed to define the abstract syn- tax of graphic modelling languages. From a GEB...Meta-modelling plays an important role in model driven software development. In this paper, a graphic exten- sion of BNF （GEBNF） is proposed to define the abstract syn- tax of graphic modelling languages. From a GEBNF syntax definition, a formal predicate logic language can be induced so that meta-modelling can be performed formally by spec- ifying a predicate on the domain of syntactically valid mod- els. In this paper, we investigate the theoretical foundation of this meta-modelling approach. We formally define the se- mantics of GEBNF and its induced predicate logic languages, then apply Goguen and Burstall＇s institution theory to prove that they form a sound and valid formal specification lan- guage for meta-modelling.展开更多
Symbiotic and asymbiotic nitrogen fixation(SNF and ANF),two forms of biological nitrogen(N)fixation,are the main pathways for external N inputs into natural terrestrial ecosystems.However,the regulatory mechanisms of ...Symbiotic and asymbiotic nitrogen fixation(SNF and ANF),two forms of biological nitrogen(N)fixation,are the main pathways for external N inputs into natural terrestrial ecosystems.However,the regulatory mechanisms of SNF and ANF,particularly in response to changing environmental conditions,remain poorly understood.Here,we investigated changes in SNF and ANF rates along two altitudinal gradients in two subtropical forests on soils with granite and slate parent materials.Our results revealed distinct patterns for SNF and ANF rates.SNF rates consistently declined with increasing altitude,whereas ANF rates initially increased at lower altitudes but declined at higher altitudes.These contrasting trends were attributed to divergent regulatory mechanisms of SNF and ANF rates.Specifically,the decrease in SNF rates was primarily driven by increased soil N availability and decreased air temperature.However,the drivers of ANF rates shifted from soil properties(e.g.,phosphorus,iron,and moisture)at lower altitudes to climatic factors(e.g.,air temperature)at higher altitudes.We also observed opposite trends of SNF and ANF between forests on granite and slate,demonstrating that lithology is an important driver of both SNF and ANF.Collectively,our findings highlight the divergent mechanisms regulating SNF and ANF in subtropical forests,which contribute to improving the mechanistic representation of biological N fixation in Earth system models.展开更多
文摘当前,就业多元化的背景下,结构性矛盾是当前高校毕业生就业面临的主要问题之一。高校专业设置与市场需求不匹配,导致部分专业的毕业生供不应求,而另一些专业则供过于求。受年轻人就业观念固化和农村岗位结构单一的影响,毕业大学生很少有人愿意在农村就业。实施乡村振兴战略是新时代中国特色社会主义的重大决策部署,而乡村振兴战略需要大量高素质人才的支持,大学生具备丰富的知识和技能,正是推动农村发展的关键力量,怎样实现乡村振兴与大学生就业的良性互动,成为就业政策改革的主要关键目标。基于此,本文先是对“BNF”(Be New Famer)“新农人”培养平台进行理论研究,其次分析“BNF”(Be New Famer)“新农人”培养平台的必要性,最后探究“BNF”(Be New Famer)“新农人”培养平台的有效策略,旨在就业多元化的背景下,促进农业农村的就业模式现代化,助力乡村振兴。
基金Funded by the National Natural Science Foundation of China(Nos.51472201,51602258,and 51632007)
文摘As potential wave-transparent materials applied at high temperatures, 3D BNf/Si3N4 ceramic matrix composites were prepared by low pressure chemical vapor infiltration or deposition（LPCVI/CVD） process from SiCl4-NH3-H2-Ar gas precursor at 800 oC. The densification process, microstructure and dielectric properties of 3D BNf/Si3N4 composites were investigated. The results indicated that 3D BNf/Si3N4 was successfully fabricated by LPCVI/CVD, with final open porosity of 2.37% and density of 1.89 g/cm3. Densification kinetics of 3D BNf/Si3N4 is a typical exponential pattern. The Si3N4 matrix was uniformly infiltrated into porous BNf preform. The deposited Si3N4 matrix was amorphous by XRD analysis. Introduction of BN fiber into Si3N4 ceramic lowered the permittivity of Si3N4. The fabricated BNf/Si3N4 composites possess low permittivity of 3.68 and low dielectric loss of lower than 0.01, which are independent of temperature below400 oC. Transmission coefficient of BNf/Si3N4 composite is 0.57 and keeps stable below 400 oC. BNf/Si3N4 can be fabricated at low temperature and may be candidates for the microwave transparent materials.
文摘Land degradation,unbalanced nutrition,change in climate and its extreme variability are the factors affecting the sustainability of agriculture and food security.In North-west Pakistan,more than 50%of the cultivated area is rain-fed and the crop productivity is low.Conservation agriculture reduces greenhouse gas emissions by enhancing soil carbon sequestration and then improved soil fertility,WUE and crop productivity.A field experiment
文摘Meta-modelling plays an important role in model driven software development. In this paper, a graphic exten- sion of BNF （GEBNF） is proposed to define the abstract syn- tax of graphic modelling languages. From a GEBNF syntax definition, a formal predicate logic language can be induced so that meta-modelling can be performed formally by spec- ifying a predicate on the domain of syntactically valid mod- els. In this paper, we investigate the theoretical foundation of this meta-modelling approach. We formally define the se- mantics of GEBNF and its induced predicate logic languages, then apply Goguen and Burstall＇s institution theory to prove that they form a sound and valid formal specification lan- guage for meta-modelling.
基金supported by the Guangdong Basic and Applied Basic Research Foundation(No.2025A1515011004)the Shenzhen Science and Technology Program(No.JCYJ20220530150015035)+1 种基金the National Natural Science Foundation of China(No.42367035)the Chinese Scholarship Council(No.202306380142).
文摘Symbiotic and asymbiotic nitrogen fixation(SNF and ANF),two forms of biological nitrogen(N)fixation,are the main pathways for external N inputs into natural terrestrial ecosystems.However,the regulatory mechanisms of SNF and ANF,particularly in response to changing environmental conditions,remain poorly understood.Here,we investigated changes in SNF and ANF rates along two altitudinal gradients in two subtropical forests on soils with granite and slate parent materials.Our results revealed distinct patterns for SNF and ANF rates.SNF rates consistently declined with increasing altitude,whereas ANF rates initially increased at lower altitudes but declined at higher altitudes.These contrasting trends were attributed to divergent regulatory mechanisms of SNF and ANF rates.Specifically,the decrease in SNF rates was primarily driven by increased soil N availability and decreased air temperature.However,the drivers of ANF rates shifted from soil properties(e.g.,phosphorus,iron,and moisture)at lower altitudes to climatic factors(e.g.,air temperature)at higher altitudes.We also observed opposite trends of SNF and ANF between forests on granite and slate,demonstrating that lithology is an important driver of both SNF and ANF.Collectively,our findings highlight the divergent mechanisms regulating SNF and ANF in subtropical forests,which contribute to improving the mechanistic representation of biological N fixation in Earth system models.
