To make clear the emission characteristics of soil N20 from typical green- house vegetable fields in North China, an experiment was conducted in greenhouse tomato field in Shouguang city, Shandong province, China＇s ...To make clear the emission characteristics of soil N20 from typical green- house vegetable fields in North China, an experiment was conducted in greenhouse tomato field in Shouguang city, Shandong province, China＇s ＂Home of Vegetables＂. The N2O fluxes were observed in four experimental treatments, as follows： none N fertilizer （CK）, single organic fertilizer （OM）, conventional fertilization （FP） and opti- mized and reduced nitrogen fertilization （OPT）, by a close chamber-gas chromato- graph method. The effects of different fertilization treatments on N2O emission and tomato yield were analyzed. The results showed that following the fertilization and ir- rigation, the pulsed emissions of N2O were measured. The N2O emission peak ap- peared after basal fertilizer application and irrigation and could be maintained for about 20 days. While the N2O emission peak caused by topdressing was smaller and last only 3-5 days. The statistical analysis showed that the N2O fluxes were affected by air temperature, soil temperature and WFPS at soil depth of 3 cm. The total contents of soil N2O fluxes had significant differences among experimental groups. The total content orderly was FP of 14. 77 kg/hm^2, OPT of 9. 73 kg/hm^2, OM of 6.84 kg/hm^2 and CK of 2.37 kg/hm^2. The N~：~ emission coefficient ranged from 0.83%-1.10%,which was close to or more than the recommended value （1.0%） by IPCC. Compared with the FP treatment, the tomato yield in OPT treatment, whose application rate of chemical N fertilizer decreased by about 60%, increased by 2.2%. Under the current management measures, the reasonable reduction on ap- plicaUon rate of organic manure and chemical nitrogen fertilizer could effectively re- duce the N=O emissions in greenhouse vegetable fields.展开更多
Tropical cyclones(TCs)in the South China Sea(SCS)cause serious disasters and loss every year to the coastal and inland areas of southern China.The types of TCs are usually difficult to forecast,and studies on the unde...Tropical cyclones(TCs)in the South China Sea(SCS)cause serious disasters and loss every year to the coastal and inland areas of southern China.The types of TCs are usually difficult to forecast,and studies on the understanding of the TCs affecting the SCS are lacking.In this study,the authors use the TC data during 1965–2017 from two best-track datasets to analyse the climatic characteristics in terms of the frequency,the track activity,and the influencing indexes of the TCs affecting the SCS and investigate the possible causes.The results show that,during 1965–2017,there were 535 TCs affecting the SCS,mainly occurring from June to November of each year,with the annual average frequency exhibiting a significant downward trend.Meanwhile,the frequency of the track activity in most areas of the SCS also demonstrate a remarkable decreasing trend but an increase in the Gulf of Tonkin and the Taiwan Strait.The large-scale environmental anomalous westerlies and the decrease of humidity in the mid-and low-level over the northern part of the SCS are likely the main causes for the decrease in frequency and the track activity.In addition,the analysis using the cyclone activity index shows that the influence of the before mentioned TCs in southern China gradually decreases,while the influence of TCs in the SCS show a decreasing trend during past decades.展开更多
This paper reports results of investigations of some surface characteristics, and resulting performance of parts proc-essed using non-traditional finishing methods. The friction factor, precision keeping and anti-cong...This paper reports results of investigations of some surface characteristics, and resulting performance of parts proc-essed using non-traditional finishing methods. The friction factor, precision keeping and anti-conglutination performance of the finished surfaces are considered, and surface characteristics such as microtopography and machining texture were investigated. The overall performance of surfaces finished using non-traditional finishing methods was found to be significantly better than that of traditional finishing methods.展开更多
基金Supported by Special Fund for Agro-scientific Research in the Public Interest(201103039)Shandong Provincial Natural Science Foundation,China(ZR2013DQ023)+1 种基金Science and Technology Development Plan Project of Shandong Province(2013GNC11204)Major Agricultural Application Technology Innovation Project of Shandong Province(Study on Environmental Regulation and Fertilizer Application Techniques for High Yield and High Efficiency Utilization of Greenhouse Tomato)~~
文摘To make clear the emission characteristics of soil N20 from typical green- house vegetable fields in North China, an experiment was conducted in greenhouse tomato field in Shouguang city, Shandong province, China＇s ＂Home of Vegetables＂. The N2O fluxes were observed in four experimental treatments, as follows： none N fertilizer （CK）, single organic fertilizer （OM）, conventional fertilization （FP） and opti- mized and reduced nitrogen fertilization （OPT）, by a close chamber-gas chromato- graph method. The effects of different fertilization treatments on N2O emission and tomato yield were analyzed. The results showed that following the fertilization and ir- rigation, the pulsed emissions of N2O were measured. The N2O emission peak ap- peared after basal fertilizer application and irrigation and could be maintained for about 20 days. While the N2O emission peak caused by topdressing was smaller and last only 3-5 days. The statistical analysis showed that the N2O fluxes were affected by air temperature, soil temperature and WFPS at soil depth of 3 cm. The total contents of soil N2O fluxes had significant differences among experimental groups. The total content orderly was FP of 14. 77 kg/hm^2, OPT of 9. 73 kg/hm^2, OM of 6.84 kg/hm^2 and CK of 2.37 kg/hm^2. The N~：~ emission coefficient ranged from 0.83%-1.10%,which was close to or more than the recommended value （1.0%） by IPCC. Compared with the FP treatment, the tomato yield in OPT treatment, whose application rate of chemical N fertilizer decreased by about 60%, increased by 2.2%. Under the current management measures, the reasonable reduction on ap- plicaUon rate of organic manure and chemical nitrogen fertilizer could effectively re- duce the N=O emissions in greenhouse vegetable fields.
基金This work was jointly supported by General Project of Technological Innovation and Application Demonstration of Chongqing Municipality[cstc2018jscx-msybX0165]Special Project for Development of Key Technology for Meteorological Forecast Service of China Meteorological Administration[YBGJXM(2018)04-08]+1 种基金National Natural Science Foundation of China[41875111]Innovation Team Project of Intelligent Meteorological Technology of Chongqing Meteorological Bureau[ZHCXTD-201804].
文摘Tropical cyclones(TCs)in the South China Sea(SCS)cause serious disasters and loss every year to the coastal and inland areas of southern China.The types of TCs are usually difficult to forecast,and studies on the understanding of the TCs affecting the SCS are lacking.In this study,the authors use the TC data during 1965–2017 from two best-track datasets to analyse the climatic characteristics in terms of the frequency,the track activity,and the influencing indexes of the TCs affecting the SCS and investigate the possible causes.The results show that,during 1965–2017,there were 535 TCs affecting the SCS,mainly occurring from June to November of each year,with the annual average frequency exhibiting a significant downward trend.Meanwhile,the frequency of the track activity in most areas of the SCS also demonstrate a remarkable decreasing trend but an increase in the Gulf of Tonkin and the Taiwan Strait.The large-scale environmental anomalous westerlies and the decrease of humidity in the mid-and low-level over the northern part of the SCS are likely the main causes for the decrease in frequency and the track activity.In addition,the analysis using the cyclone activity index shows that the influence of the before mentioned TCs in southern China gradually decreases,while the influence of TCs in the SCS show a decreasing trend during past decades.
文摘This paper reports results of investigations of some surface characteristics, and resulting performance of parts proc-essed using non-traditional finishing methods. The friction factor, precision keeping and anti-conglutination performance of the finished surfaces are considered, and surface characteristics such as microtopography and machining texture were investigated. The overall performance of surfaces finished using non-traditional finishing methods was found to be significantly better than that of traditional finishing methods.
