In Chiapas highlands to southeast of Mexico, the scarcity of water is worrying, according to technical reports of the IPCC the runoff will less between 150 to 250 mm per year in the southeast of Mexico, this situation...In Chiapas highlands to southeast of Mexico, the scarcity of water is worrying, according to technical reports of the IPCC the runoff will less between 150 to 250 mm per year in the southeast of Mexico, this situation will increase the problems of water availability in Chiapas highlands in the future. For actually more of 18,160 small rural indigenous communities (SRIC) in Chiapas there is not drinking water. In order to contribute a given solution to scarcity of drinking water in the SRIC, The Autonomous University of Chiapas (UNACH in its Spanish acronym) and Mexican Institute of Water Technology (IMTA in its Spanish acronym) designed and constructed in 1999 the Rain Water Harvesting (RWH) in Yalentay municipality of Zinacantan in Chiapas, Mexico. The scientific and technical contributions of RWH are: The design guarantee the water quality for a prolonged time of storage avoiding the photosynthesis inside the system;Not emitted greenhouse gasses because it doesn’t need any kind of fossil fuels;Not produces anything kind of damage to the environment;It has to be inexpensive, using in its construction manpower and materials from de region;Store the maximum quantity of water in the minimum space. The RWH has increased the standard of living of the habitants from Yalentay and improving their health conditions.展开更多
Specific management of water regimes, soil and N in China might play an important role in regulating N2O and CH4 emissions in rice fields. Nitrous oxide and methane emissions from alternate non-flooded/flooded paddies...Specific management of water regimes, soil and N in China might play an important role in regulating N2O and CH4 emissions in rice fields. Nitrous oxide and methane emissions from alternate non-flooded/flooded paddies were monitored simultaneously during a 516-day incubation with lysimeter experiments. Two N sources (15N-(NH4)2SO4 and 15N-labeled milk vetch) were applied to two contrasting paddies: one derived from Xiashu loess (Loess) and one from Quaternary red clay (Clay). Both N2O and CH4 emissions were significantly higher in soil Clay than in soil Loess during the flooded period. For both soil, N2O emissions peaked at the transition periods shortly after the beginning of the flooded and non-flooded seasons. Soil type affected N2O emission patterns. In soil Clay, the emission peak during the transition period from non-flooded to flooded conditions was much higher than the peak during the transition period from flooded to non-flooded conditions. In soil Loess, the emission peak during the transition period from flooded to non-flooded conditions was obviously higher than the peak during the transition period from non-flooded to flooded conditions except for milk vetch treatment. Soil type also had a significant effect on CH4 emissions during the flooded season, over which the weighted average flux was 111 mg C m-2 h-1 and 2.2 mg C m-2 h-1 from Clay and Loess, respectively. Results indicated that it was the transition in the water regime that dominated N2O emissions while it was the soil type that dominated CH4 emissions during the flooded season. Anaerobic oxidation of methane possibly existed in soil Loess during the flooded season.展开更多
Carbon nanotubes(CNTs) are fabricated in carbon cloth by ultilizing the waste gasses when fabricating hafnium carbide nanowires(HfC_(NWS)) through thermal pyrolysis of Hf-containing polymer precursor.The formed HfC_(N...Carbon nanotubes(CNTs) are fabricated in carbon cloth by ultilizing the waste gasses when fabricating hafnium carbide nanowires(HfC_(NWS)) through thermal pyrolysis of Hf-containing polymer precursor.The formed HfC_(NWS) are distributed uniformly on the surface of the carbon fibers in carbon/carbon(C/C) composites and display perfect single crystal appearance.The pyrolysis of the Hf-containing organic precursor provides hafnium and carbon source for the growth of HfC_(NWS).The released waste gasses containing CO,CH4and CO_(2)are the main carbon source for the growth of CNTs.Specifically,the flexural strength of HfC_(NWS) reinforced carbon/carbon(HfC_(NWS)-C/C) composites is enhanced by ~105% compared with pure C/C,and the CNTs/carbon cloth also displays improved electrochemical performance with respect to capacitor applications.The present study introduces a novel sustainable and eco-friendly process related to polymer-derived ceramics to form advanced ceramic nanocomposites and proposes a deep understanding of the growth mechanism of CNTs.展开更多
Glasses in the system 24.5Na<sub><span style="font-size:12px;font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O·24.5CaO·6P</span>...Glasses in the system 24.5Na<sub><span style="font-size:12px;font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O·24.5CaO·6P</span><sub><span style="font-size:12px;font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-size:12px;font-family:Verdana;">5</span></sub><span style="font-family:Verdana;">·xSrO·(45-x)SiO</span><sub><span style="font-size:12px;font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> have been</span><span style="font-family:;" "=""><span style="font-family:Verdana;"> studied in the composition region of x = 0 - 15 mol%. The as prepared glasses are transparent and have an amorphous network structure. On the otherhand, heat treated glasses are transformed to opaque white glass ceramic characterized by their highly crystalline network structure. Crystalline apatite (calcium phosphate, Ca</span><sub><span style="font-size:12px;font-family:Verdana;">3</span></sub><span style="font-family:Verdana;">(PO</span><sub><span style="font-size:12px;font-family:Verdana;">4</span></sub><span style="font-family:Verdana;">)</span><sub><span style="font-size:12px;font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">, wollastonite (calcium silicate, CaSiO</span><sub><span style="font-size:12px;font-family:Verdana;">3</span></sub><span style="font-family:Verdana;">), and strontium calcium phosphate</span></span><span style="font-family:Verdana;"> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">Ca</span><sub><span style="font-size:12px;font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">Sr(PO</span><sub><span style="font-size:12px;font-family:Verdana;">4</span></sub><span style="font-family:Verdana;">)</span><sub><span style="font-size:12px;font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> </span></span><span style="font-family:;" "=""><span style="font-family:Verdana;">are the main well-formed crystalline species played the major role in material bioactivity. Increasing SrO leads to enhancing material crystallite and enhances the hardness of the host glass matrix. The change of XRD spectra, </span><sup><span style="font-size:12px;font-family:Verdana;">31</span></sup><span style="font-family:Verdana;">P NMR chemical shift and hardness number upon increasing SrO are considered due to modification of the apatit Ca(PO</span><sub><span style="font-size:12px;font-family:Verdana;">3</span></sub><span style="font-family:Verdana;">)</span><sub><span style="font-size:12px;font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> to involve Sr ions inducing Ca</span><sub><span style="font-size:12px;font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">Sr (PO</span><sub><span style="font-size:12px;font-family:Verdana;">4</span></sub><span style="font-family:Verdana;">)</span><sub><span style="font-size:12px;font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> apatite one. Such species play the role in enhancing material properties and hardness.</span></span>展开更多
Taking into account the properties of the arc plasma and the electromagnetic, heat and radiative phenomena, commercial computational fluid dynamics software PHOENICS has been adapted and modified to develop the three-...Taking into account the properties of the arc plasma and the electromagnetic, heat and radiative phenomena, commercial computational fluid dynamics software PHOENICS has been adapted and modified to develop the three-dimensional magneto-hydrodynamic （MHD） model of arc in a low voltage circuit breaker. The effects of the arc ignition location, venting size and gassing material on arc behavior have been investigated. The analysis of the results show that the arc velocity accelerates with the increase in the distance between arc ignition location and of the venting size, and the existence of the gassing material is beneficial to improving the arc voltage and reducing the arc temperature.展开更多
Computational fluid dynamics(CFD)and experimental analyses of some of the basic characteristics of air sparging in a tall stirred vessel equipped with a three-stage impeller are presented.The impeller was assembled fr...Computational fluid dynamics(CFD)and experimental analyses of some of the basic characteristics of air sparging in a tall stirred vessel equipped with a three-stage impeller are presented.The impeller was assembled from a radial ABT impeller as the lower,a turbine 6 PBT45 as the middle and an axial Scaba-type 3SHP1 impeller as the upper.All the impellers were of the same diameter,i.e.,225 mm,while the vessel diameter was 450 mm.The impeller’s rotational speed was 178 r·min-1.The aeration regime was established with an air volumetric flow rate of 28.3 m3·h-1.To the best of our knowledge,this study is the first to consider the very high gassing rate by means of CFD in a tank stirred by three-stage axial/radial impellers.The numerical simulation was performed using the ANSYS Fluent(R17.2,2016)code for solving the governing equations of fluid dynamics in single-and multi-phase systems.While discussing the bubble size distribution,a discrete population balance model(PBM)was used.Adopting CFD,the stirring power and the total void fraction(the total gas holdup)were calculated.The results were in good agreement with the measured values using a laboratory experimental device.展开更多
Influence of the gassing materials, such as PA6, PMMA, and POM on the dielectric properties of air are investigated. In this work, the fundamental electron collision cross section data were carefully selected and vali...Influence of the gassing materials, such as PA6, PMMA, and POM on the dielectric properties of air are investigated. In this work, the fundamental electron collision cross section data were carefully selected and validated. Then the species compositions of the air–organic vapor mixtures were calculated based on the Gibbs free energy minimization. Finally, the Townsend ionization coefficient, the Townsend electron attachment coefficient and the critical reduced electric field strength were derived from the calculated electron energy distribution function by solving the Boltzmann transport equation. The calculation results indicated that H;O with large attachment cross sections has a great impact on the critical reduced electric field strength of the air–organic vapor mixtures. On the other hand, the vaporization of gassing materials can help to increase the dielectric properties of air circuit breakers to some degree.展开更多
文摘In Chiapas highlands to southeast of Mexico, the scarcity of water is worrying, according to technical reports of the IPCC the runoff will less between 150 to 250 mm per year in the southeast of Mexico, this situation will increase the problems of water availability in Chiapas highlands in the future. For actually more of 18,160 small rural indigenous communities (SRIC) in Chiapas there is not drinking water. In order to contribute a given solution to scarcity of drinking water in the SRIC, The Autonomous University of Chiapas (UNACH in its Spanish acronym) and Mexican Institute of Water Technology (IMTA in its Spanish acronym) designed and constructed in 1999 the Rain Water Harvesting (RWH) in Yalentay municipality of Zinacantan in Chiapas, Mexico. The scientific and technical contributions of RWH are: The design guarantee the water quality for a prolonged time of storage avoiding the photosynthesis inside the system;Not emitted greenhouse gasses because it doesn’t need any kind of fossil fuels;Not produces anything kind of damage to the environment;It has to be inexpensive, using in its construction manpower and materials from de region;Store the maximum quantity of water in the minimum space. The RWH has increased the standard of living of the habitants from Yalentay and improving their health conditions.
基金Project supported by the National Natural Science Foundation of China (Nos. 30390080 and 30390081).
文摘Specific management of water regimes, soil and N in China might play an important role in regulating N2O and CH4 emissions in rice fields. Nitrous oxide and methane emissions from alternate non-flooded/flooded paddies were monitored simultaneously during a 516-day incubation with lysimeter experiments. Two N sources (15N-(NH4)2SO4 and 15N-labeled milk vetch) were applied to two contrasting paddies: one derived from Xiashu loess (Loess) and one from Quaternary red clay (Clay). Both N2O and CH4 emissions were significantly higher in soil Clay than in soil Loess during the flooded period. For both soil, N2O emissions peaked at the transition periods shortly after the beginning of the flooded and non-flooded seasons. Soil type affected N2O emission patterns. In soil Clay, the emission peak during the transition period from non-flooded to flooded conditions was much higher than the peak during the transition period from flooded to non-flooded conditions. In soil Loess, the emission peak during the transition period from flooded to non-flooded conditions was obviously higher than the peak during the transition period from non-flooded to flooded conditions except for milk vetch treatment. Soil type also had a significant effect on CH4 emissions during the flooded season, over which the weighted average flux was 111 mg C m-2 h-1 and 2.2 mg C m-2 h-1 from Clay and Loess, respectively. Results indicated that it was the transition in the water regime that dominated N2O emissions while it was the soil type that dominated CH4 emissions during the flooded season. Anaerobic oxidation of methane possibly existed in soil Loess during the flooded season.
基金financial supports of this work by the National Natural Science Foundation of China(Nos.52130205,51727804,91860203,52061135102)the National Key R&D Program of China(No.2021YFA0715803)the China Scholarship Program,2020(CSC No.202006290179)。
文摘Carbon nanotubes(CNTs) are fabricated in carbon cloth by ultilizing the waste gasses when fabricating hafnium carbide nanowires(HfC_(NWS)) through thermal pyrolysis of Hf-containing polymer precursor.The formed HfC_(NWS) are distributed uniformly on the surface of the carbon fibers in carbon/carbon(C/C) composites and display perfect single crystal appearance.The pyrolysis of the Hf-containing organic precursor provides hafnium and carbon source for the growth of HfC_(NWS).The released waste gasses containing CO,CH4and CO_(2)are the main carbon source for the growth of CNTs.Specifically,the flexural strength of HfC_(NWS) reinforced carbon/carbon(HfC_(NWS)-C/C) composites is enhanced by ~105% compared with pure C/C,and the CNTs/carbon cloth also displays improved electrochemical performance with respect to capacitor applications.The present study introduces a novel sustainable and eco-friendly process related to polymer-derived ceramics to form advanced ceramic nanocomposites and proposes a deep understanding of the growth mechanism of CNTs.
文摘Glasses in the system 24.5Na<sub><span style="font-size:12px;font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O·24.5CaO·6P</span><sub><span style="font-size:12px;font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-size:12px;font-family:Verdana;">5</span></sub><span style="font-family:Verdana;">·xSrO·(45-x)SiO</span><sub><span style="font-size:12px;font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> have been</span><span style="font-family:;" "=""><span style="font-family:Verdana;"> studied in the composition region of x = 0 - 15 mol%. The as prepared glasses are transparent and have an amorphous network structure. On the otherhand, heat treated glasses are transformed to opaque white glass ceramic characterized by their highly crystalline network structure. Crystalline apatite (calcium phosphate, Ca</span><sub><span style="font-size:12px;font-family:Verdana;">3</span></sub><span style="font-family:Verdana;">(PO</span><sub><span style="font-size:12px;font-family:Verdana;">4</span></sub><span style="font-family:Verdana;">)</span><sub><span style="font-size:12px;font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">, wollastonite (calcium silicate, CaSiO</span><sub><span style="font-size:12px;font-family:Verdana;">3</span></sub><span style="font-family:Verdana;">), and strontium calcium phosphate</span></span><span style="font-family:Verdana;"> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">Ca</span><sub><span style="font-size:12px;font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">Sr(PO</span><sub><span style="font-size:12px;font-family:Verdana;">4</span></sub><span style="font-family:Verdana;">)</span><sub><span style="font-size:12px;font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> </span></span><span style="font-family:;" "=""><span style="font-family:Verdana;">are the main well-formed crystalline species played the major role in material bioactivity. Increasing SrO leads to enhancing material crystallite and enhances the hardness of the host glass matrix. The change of XRD spectra, </span><sup><span style="font-size:12px;font-family:Verdana;">31</span></sup><span style="font-family:Verdana;">P NMR chemical shift and hardness number upon increasing SrO are considered due to modification of the apatit Ca(PO</span><sub><span style="font-size:12px;font-family:Verdana;">3</span></sub><span style="font-family:Verdana;">)</span><sub><span style="font-size:12px;font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> to involve Sr ions inducing Ca</span><sub><span style="font-size:12px;font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">Sr (PO</span><sub><span style="font-size:12px;font-family:Verdana;">4</span></sub><span style="font-family:Verdana;">)</span><sub><span style="font-size:12px;font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> apatite one. Such species play the role in enhancing material properties and hardness.</span></span>
基金The project supported by National Natural Science Foundation of China (No. 50507016) and the Specialized Research Fund forthe Doctoral Program of Higher Education (No. 20020698008) and the Doctorate Foundation of Xi'an Jiaotong University
文摘Taking into account the properties of the arc plasma and the electromagnetic, heat and radiative phenomena, commercial computational fluid dynamics software PHOENICS has been adapted and modified to develop the three-dimensional magneto-hydrodynamic （MHD） model of arc in a low voltage circuit breaker. The effects of the arc ignition location, venting size and gassing material on arc behavior have been investigated. The analysis of the results show that the arc velocity accelerates with the increase in the distance between arc ignition location and of the venting size, and the existence of the gassing material is beneficial to improving the arc voltage and reducing the arc temperature.
基金supported by the Slovenian Ministry of Education,Science and Sport under contract no.P2-0162.
文摘Computational fluid dynamics(CFD)and experimental analyses of some of the basic characteristics of air sparging in a tall stirred vessel equipped with a three-stage impeller are presented.The impeller was assembled from a radial ABT impeller as the lower,a turbine 6 PBT45 as the middle and an axial Scaba-type 3SHP1 impeller as the upper.All the impellers were of the same diameter,i.e.,225 mm,while the vessel diameter was 450 mm.The impeller’s rotational speed was 178 r·min-1.The aeration regime was established with an air volumetric flow rate of 28.3 m3·h-1.To the best of our knowledge,this study is the first to consider the very high gassing rate by means of CFD in a tank stirred by three-stage axial/radial impellers.The numerical simulation was performed using the ANSYS Fluent(R17.2,2016)code for solving the governing equations of fluid dynamics in single-and multi-phase systems.While discussing the bubble size distribution,a discrete population balance model(PBM)was used.Adopting CFD,the stirring power and the total void fraction(the total gas holdup)were calculated.The results were in good agreement with the measured values using a laboratory experimental device.
基金supported by the National Key Basic Research Program of China(973 Program)2015CB251002National Natural Science Foundation of China under Grant 51521065,51577145+1 种基金the Fundamental Research Funds for the Central UniversitiesShaanxi Province Natural Science Foundation 2013JM-7010
文摘Influence of the gassing materials, such as PA6, PMMA, and POM on the dielectric properties of air are investigated. In this work, the fundamental electron collision cross section data were carefully selected and validated. Then the species compositions of the air–organic vapor mixtures were calculated based on the Gibbs free energy minimization. Finally, the Townsend ionization coefficient, the Townsend electron attachment coefficient and the critical reduced electric field strength were derived from the calculated electron energy distribution function by solving the Boltzmann transport equation. The calculation results indicated that H;O with large attachment cross sections has a great impact on the critical reduced electric field strength of the air–organic vapor mixtures. On the other hand, the vaporization of gassing materials can help to increase the dielectric properties of air circuit breakers to some degree.
