This research examined nitrogen mineralization in the top 10 cm of soils along a vegetation gradient in Hong Kong at sites where fire has been absent for 0, 1, 3, 6 and 17 years (at the time of the study), and the rel...This research examined nitrogen mineralization in the top 10 cm of soils along a vegetation gradient in Hong Kong at sites where fire has been absent for 0, 1, 3, 6 and 17 years (at the time of the study), and the relationships between N mineralization and successional development of vegetation in the absence of fire. The sites including a newly burnt area (S1), short grassland (S2), tall grassland (S3), mixed tall grassland and shrubland (S4), and woodland (S5) were selected,and the in situ core incubation method was used to estimate nitrogen mineralization. Throughout the 60-day incubation in four periods, more nitrogen was mineralized at the S3 and S4 sites, the predominantly grassland sites, which contained the highest levels of soil organic matter (SOM) and total Kjeldahl nitrogen (TKN), than the S1 site, while immobilization occurred at the S2 and S5 sites. Leaching loss decreased with successional development of the vegetation, in the order of S1 > S2 > S3 > S4 > S5. The pattern of nitrogen uptake with ecological succession was less conspicuous, being complicated by the immediate effect of fire and possibly the ability of the woodland species to extract nitrogen from the deeper ground.In the absence of fire for 3 to 6 years, the build-up of SOM and TKN was accompanied by active mineralization, thus paving the way for the invasion of shrub and tree species. A close relationship existed between nitrogen mineralization and ecological succession with this vegetation gradient. Inherent mechanisms to preserve nitrogen in a fire-prone environment including immobilization and uptake and the practical relevance of nitrogen mineralization to reforestation are discussed.展开更多
A piston core Z14-6 was used in this study. The core, 896 cm long, was collected from eastern slope of the Okinawa Trough (27°07'N, 127°27'E, water depth 739m). The δ^18O and δ^13C values of the sedime...A piston core Z14-6 was used in this study. The core, 896 cm long, was collected from eastern slope of the Okinawa Trough (27°07'N, 127°27'E, water depth 739m). The δ^18O and δ^13C values of the sediment bearing planktonic foraminifera G. sacculifer and N. dutertrei were determined; and the abundance of volcanic glass was analyzed. The volcanic glass content high occurred in early stage of polar ice-sheet growth period, or the beginning of cold climate periods corresponding to Milankovitch cycles (Peak Ⅰ, Ⅱ and V are corresponding to the beginnings of oxygen isotopic stages 2, 4 and 6, and Peak Ⅲ and Ⅳ are matching oxygen isotopic stage 5b-5d.). It might be possible that volcanic episodes and climate changes were responding to orbital forcing in the Okinawa Trough in late Quaternary. The δ^18O difference between N. dutertrei and G. sacculifer shows no clear correlation to the volcanic glass content high, which suggests that the volcanic eruptions did not influence the structure of upper water column. However, the low δ^13C difference between G. sacculifer and N. dutertrei is coeval with the volcanic glass high or sub-high content. This fact suggests that volcanic eruptions might influence the reduction in vertical nutritional gradient and carbon cycle process in upper water column. A possible mechanism is that huge quantity of ash and dust had weakened the light intensity, resulting in photosynthesis reduction, productivity decrease, and biological pumping.展开更多
A numerical model is presented to investigate the performance of homogeneous charge compression ignition(HCCI) engines fueled with ethanol. Two approaches are studied. On one hand, two-step reaction mechanisms with Ar...A numerical model is presented to investigate the performance of homogeneous charge compression ignition(HCCI) engines fueled with ethanol. Two approaches are studied. On one hand, two-step reaction mechanisms with Arrhenius reaction rates are implemented in combustion chemistry modeling. On the other hand, a reduced mechanism containing important reactions of ethanol involving heat release rate and reaction rates compatible with experimental data is employed. Since controls of combustion phenomenon and ignition timing are the main issues of these engines, the effects of inlet temperature and equivalence ratio as the controlling factors on the operating parameters such as ignition timing, burn duration, in-cylinder temperature and pressure of HCCI engines are explored. The results show that the maximum predicted pressures for thermodynamic model are about 71.3×10~5 Pa and 79.79×10~5 Pa, and for chemical kinetic model, they are about 71.48×10~5 Pa and 78.123×10~5 Pa, fairly comparable with corresponding experimental values of 72×10~5 Pa and 78.7×10~5 Pa. It is observed that increasing the initial temperature advances the ignition timing, decreases the burn duration and increases the peak temperature and pressure. Moreover, the maximum temperature and pressure are associated with richer mixtures.展开更多
In order to minimise the bushfires negative impacts on society, an efficient andreliable bushfire detection system was proposed to assess the devastated effects of the2009 Victorian bushfires.It is possible to utilise...In order to minimise the bushfires negative impacts on society, an efficient andreliable bushfire detection system was proposed to assess the devastated effects of the2009 Victorian bushfires.It is possible to utilise the repetitive capability of satellite remotesensing imagery to identify the location of change to the Earth's surface and integrate thedifferent remotely sensed indices.The results confirm that the procedure can offer essentialspatial information for bushfire assessment.展开更多
This paper will apply a politically oriented description-critique paradigm developed from the works of Whitehall and Grewell that offers a way to examine works of popular culture, particularly Mars-based science ficti...This paper will apply a politically oriented description-critique paradigm developed from the works of Whitehall and Grewell that offers a way to examine works of popular culture, particularly Mars-based science fiction films. Because of the unique nature of these films, primarily which they are set in a future and distant world, they allow us to explore the socio-political landscape in which they were created from a remove that does not exist in "real-world" based works. Specifically we will be examining the governing power (in any particular Mars-based science fiction film) that might be either wielded by business interests or governmental interests. Although it is possible to have both a strong government and a strong business in a society, in many Mars-based science fiction films, government and business seem to represent two sides of a continuum. The stronger the business power structure in the film, the weaker the governmental power structure, and vice-versa.展开更多
A relatively perfect coalmine fire risk-evaluating and order-arranging model that includes sixteen influential factors was established according to the statistical information of the fully mechanized coalface ground o...A relatively perfect coalmine fire risk-evaluating and order-arranging model that includes sixteen influential factors was established according to the statistical information of the fully mechanized coalface ground on the uncertainty measure theory. Then the single-index measure function of sixteen influential factors and the calculation method of computing the index weight ground on entropy theory were respectively established. The value assignment of sixteen influential factors was carried out by the qualitative analysis and observational data, respectively, in succession. The sequence of fire danger class of four experimental coalfaces could be obtained by the computational aids of Matlab according to the confidence level criterion. Some conclusions that the fire danger class of the No.l, No.2 and No.3 coalface belongs to high criticality can be obtained. But the fire danger class of the No.4 coalface belongs to higher criticality. The fire danger class of the No.4 coalface is more than that of the No.2 coalface. The fire danger class of the No.2 coalface is more than that of the No.1 coalface. Finally, the fire danger class of the No.1 coalface is more than that of the No.3 coalface.展开更多
A new generation conical spray system for conventional diesel engines or premixed combustion diesel engines is introduced. By means of oriented impingement method, flexible spray penetration in design is realized. Hig...A new generation conical spray system for conventional diesel engines or premixed combustion diesel engines is introduced. By means of oriented impingement method, flexible spray penetration in design is realized. High-speed photograph was used to investigate the spatial distribution characteristics of the new spray for cases of different impingement angles and needle valve opening pressures. The results show that, by applying spray impingement orientation, fuel jets spread along the cone surface as shape of sectors, so the dispersion of jets is increased obviously. Changing on impingement angle leads to variation of penetration, which is critical in homogeneous mixture preparation. Due to the flexibility of spray penetration in design, the spray impingement on liner is avoided in a great extent. The results also indicate that higher needle valve opening pressure results in longer penetration and larger spray angle after impingement. Combustion characteristics of the impinged conical spray were studied in the 1135 type diesel engine. The new impinged conical spray system work smoothly in full load range with better fuel economy and lower emissions of NOx and soot than the original test engine.展开更多
The thermal conductivity values of ordinary concrete can be adjusted to those prescribed in constructions by entraining air bubbles to reduce the density of concrete in order to achieve good thermal insulation. This p...The thermal conductivity values of ordinary concrete can be adjusted to those prescribed in constructions by entraining air bubbles to reduce the density of concrete in order to achieve good thermal insulation. This paper concerns the analysis of air bubble distribution in concrete obtained by micro X-ray μCT (computed tomography) and correlates it with its thermal conductivity (k). The samples were prepared of ordinary concrete varying the density by air-entraining additives, ranging between 2,277 kg/m3 and 1,779 kg/m3, aiming to correlate the mechanical properties and k with the characteristics of the bubble distribution. The results show that air-entrainment leads to viable use of this material as sealer to achieve good thermal insulation, and it can be adjusted, but there seems to be a limit to air entraining. By analysis of the μCT images, it was possible to correlate the more quantity of bubbles of smaller diameter with the minor k, in dry or wet state, and to prove that there is a limit in the entrapped air content, and if it is exceeded, the coalescence occurs.展开更多
Objective To investigate the blood lead levels (BLLs) in the duration of pregnancy and 6-12 weeks after delivery, and analyze the influencing factors of BLLs in healthy pregnant women. Methods Pregnant women were r...Objective To investigate the blood lead levels (BLLs) in the duration of pregnancy and 6-12 weeks after delivery, and analyze the influencing factors of BLLs in healthy pregnant women. Methods Pregnant women were recruited from September 2009 to February 2010 at the prenatal clinic in Nanjing Maternity and Child Health Care Hospital. Altogether 174 healthy pregnant women without pregnant or obstetric complications or abnormal pregnancy outcomes were enrolled as the gravida group, and 120 healthy non-pregnant women as the control group. BLLs during pregnancy were determined by flame atomic absorption spectroscopy. Results BLLs in all the three pregnancy trimesters and postpartum were 59.8±24.3, 55.4±20.1, 55.9±19.7, and 67.6±17.4 μ/L, respectively, and the mean BLL in control group was 67.5±21.3 μg/L. BLLs during all the three trimesters were lower in the gravida group than in the control group (P=0.043, 0.021, and 0.028). Furthermore, occupations, nutrients supplementation, and time of house/apartment painted were associated with BLLs in pregnant women. Lead-related occupations, cosmetics use, and living in a house painted less than 1 year before are risk factors of high BLLs among pregnant women, while calcium, iron, zinc, and milk supplements are protective factors. Conclusion Supplementing calcium, iron, zinc, and milk, or avoiding contact with risk factors may help people, especially pregnant women, to reduce lead exposure.展开更多
Dragon fruit (Hylocereus undulates) was planted in a large area of karst region in recent years. To understand whether karst drought may impact on its physiological process is important and useful for planning and m...Dragon fruit (Hylocereus undulates) was planted in a large area of karst region in recent years. To understand whether karst drought may impact on its physiological process is important and useful for planning and management of this fruit. In this study, we contrasted with a relative species Hylocereus undatus, and set up experiment to study physiological and biochemical trait and its response to different karst soil water level deficiency, so as to understand the mechanism of H. undulates and H. undatus in adaptation to karst drought condition. The results showed that, trends of physiological and biochemical response to drought was similar between two species. With the intensive of soil water deficiency, such toxin substance as malonaldehyde (MDA) increased, but meanwhile, two protective enzymes superoxide dismutase (SOD) and peroxidases (POD) and osmotic adjustment Proline (Pro) increase as well. Under relative water content (RWC) 〉50% condition, the enzyme can effectively protect the cells from toxin MDA injure, and Pro can also maintain the water needs through osmotic adjustment. However, under RWC 〈 40% condition, protective enzymes were not enough for cleaning MDA. Biomass was largest under RWC=70%-80%, with low root shoot ratio and high aboveground biomass. Biomass significantly decreased under RWC 30%-40%, which decline by 73.28% and 73.56% in H. undulates and H. undatus respectively. Therefore, RWC=70%-80% would be an optimal soil moisture while developing dragon fruit in karst, which is favor to fruit production. Under moderate drought e.g. RWC=50%-60%, plants may regulate by metabolic process and balance unfavorable substance, but it allocated much more biomass to root, reduced the aboveground biomass, which is not advance for fruit production.展开更多
To address the increasing demands on pollution control and energy saving, the study of low-emission and high-efficiency burners has been emphasized worldwide. Swirl-induced environmental burners(EV-burners), have nota...To address the increasing demands on pollution control and energy saving, the study of low-emission and high-efficiency burners has been emphasized worldwide. Swirl-induced environmental burners(EV-burners), have notable features aligned with these requirements. In this study, an EV burner is investigated by both an ECT system and an OH-PLIF system. The aim is to detect the structure of a flame and obtain more information about the combustion process in an EV burner. 3D ECT sensitivity maps are generated for the measurement and OH-PLIF images are acquired in the same combustion zone as for the ECT measurements. The experimental images of a flame by ECT are in good agreement with the OH radical distribution pictures captured by OH-PLIF, which provide a mutual verification of the visualization method.展开更多
Tomographic techniques have great abilities to interrogate the combustion processes, especially when it is combined with the physical models of the combustion itself. In this study, a data fusion algorithm is develope...Tomographic techniques have great abilities to interrogate the combustion processes, especially when it is combined with the physical models of the combustion itself. In this study, a data fusion algorithm is developed to investigate the flame distribution of a swirl-induced environmental(EV) burner, a new type of burner for low NOx combustion. An electric capacitance tomography(ECT) system is used to acquire 3D flame images and computational fluid dynamics(CFD) is applied to calculate an initial distribution of the temperature profile for the EV burner. Experiments were also carried out to visualize flames at a series of locations above the burner. While the ECT images essentially agree with the CFD temperature distribution, discrepancies exist at a certain height. When data fusion is applied, the discrepancy is visibly reduced and the ECT images are improved. The methods used in this study can lead to a new route where combustion visualization can be much improved and applied to clean energy conversion and new burner development.展开更多
The phenomena of flame spread over aviation kerosene with an obstacle in liquid phase are investigated experimentally through surface temperature measurement by using infrared camera,schlieren images of subsurface flo...The phenomena of flame spread over aviation kerosene with an obstacle in liquid phase are investigated experimentally through surface temperature measurement by using infrared camera,schlieren images of subsurface flow in front of and behind obstacle and residence time of flame obtained from video recording.Experimental results reveal that obstacle has no effect on gas phase controlled flame spread.But for liquid phase controlled flame spread,flame can be stopped by an obstacle with its top edge flush with oil surface,and the residence time decreases with the increase of initial temperature of fuel.That conduction and radiation only play a subsidiary role in flame spread over liquid fuel was proved by schlieren images and surface temperature profiles.展开更多
基金Project supported by the Commonwealth Fellowship Scheme and the United College Endowment Fund of the Chinese University of Hong Kong
文摘This research examined nitrogen mineralization in the top 10 cm of soils along a vegetation gradient in Hong Kong at sites where fire has been absent for 0, 1, 3, 6 and 17 years (at the time of the study), and the relationships between N mineralization and successional development of vegetation in the absence of fire. The sites including a newly burnt area (S1), short grassland (S2), tall grassland (S3), mixed tall grassland and shrubland (S4), and woodland (S5) were selected,and the in situ core incubation method was used to estimate nitrogen mineralization. Throughout the 60-day incubation in four periods, more nitrogen was mineralized at the S3 and S4 sites, the predominantly grassland sites, which contained the highest levels of soil organic matter (SOM) and total Kjeldahl nitrogen (TKN), than the S1 site, while immobilization occurred at the S2 and S5 sites. Leaching loss decreased with successional development of the vegetation, in the order of S1 > S2 > S3 > S4 > S5. The pattern of nitrogen uptake with ecological succession was less conspicuous, being complicated by the immediate effect of fire and possibly the ability of the woodland species to extract nitrogen from the deeper ground.In the absence of fire for 3 to 6 years, the build-up of SOM and TKN was accompanied by active mineralization, thus paving the way for the invasion of shrub and tree species. A close relationship existed between nitrogen mineralization and ecological succession with this vegetation gradient. Inherent mechanisms to preserve nitrogen in a fire-prone environment including immobilization and uptake and the practical relevance of nitrogen mineralization to reforestation are discussed.
基金supported by the Knowledge Innovation Program ofChinese Academy of Sciences (Project No. KZCX3-SW-220), NSFC (No.90411014 and 40176019) and the National Major Fundamental Researchand Development Project (No. G20000467).
文摘A piston core Z14-6 was used in this study. The core, 896 cm long, was collected from eastern slope of the Okinawa Trough (27°07'N, 127°27'E, water depth 739m). The δ^18O and δ^13C values of the sediment bearing planktonic foraminifera G. sacculifer and N. dutertrei were determined; and the abundance of volcanic glass was analyzed. The volcanic glass content high occurred in early stage of polar ice-sheet growth period, or the beginning of cold climate periods corresponding to Milankovitch cycles (Peak Ⅰ, Ⅱ and V are corresponding to the beginnings of oxygen isotopic stages 2, 4 and 6, and Peak Ⅲ and Ⅳ are matching oxygen isotopic stage 5b-5d.). It might be possible that volcanic episodes and climate changes were responding to orbital forcing in the Okinawa Trough in late Quaternary. The δ^18O difference between N. dutertrei and G. sacculifer shows no clear correlation to the volcanic glass content high, which suggests that the volcanic eruptions did not influence the structure of upper water column. However, the low δ^13C difference between G. sacculifer and N. dutertrei is coeval with the volcanic glass high or sub-high content. This fact suggests that volcanic eruptions might influence the reduction in vertical nutritional gradient and carbon cycle process in upper water column. A possible mechanism is that huge quantity of ash and dust had weakened the light intensity, resulting in photosynthesis reduction, productivity decrease, and biological pumping.
文摘A numerical model is presented to investigate the performance of homogeneous charge compression ignition(HCCI) engines fueled with ethanol. Two approaches are studied. On one hand, two-step reaction mechanisms with Arrhenius reaction rates are implemented in combustion chemistry modeling. On the other hand, a reduced mechanism containing important reactions of ethanol involving heat release rate and reaction rates compatible with experimental data is employed. Since controls of combustion phenomenon and ignition timing are the main issues of these engines, the effects of inlet temperature and equivalence ratio as the controlling factors on the operating parameters such as ignition timing, burn duration, in-cylinder temperature and pressure of HCCI engines are explored. The results show that the maximum predicted pressures for thermodynamic model are about 71.3×10~5 Pa and 79.79×10~5 Pa, and for chemical kinetic model, they are about 71.48×10~5 Pa and 78.123×10~5 Pa, fairly comparable with corresponding experimental values of 72×10~5 Pa and 78.7×10~5 Pa. It is observed that increasing the initial temperature advances the ignition timing, decreases the burn duration and increases the peak temperature and pressure. Moreover, the maximum temperature and pressure are associated with richer mixtures.
文摘In order to minimise the bushfires negative impacts on society, an efficient andreliable bushfire detection system was proposed to assess the devastated effects of the2009 Victorian bushfires.It is possible to utilise the repetitive capability of satellite remotesensing imagery to identify the location of change to the Earth's surface and integrate thedifferent remotely sensed indices.The results confirm that the procedure can offer essentialspatial information for bushfire assessment.
文摘This paper will apply a politically oriented description-critique paradigm developed from the works of Whitehall and Grewell that offers a way to examine works of popular culture, particularly Mars-based science fiction films. Because of the unique nature of these films, primarily which they are set in a future and distant world, they allow us to explore the socio-political landscape in which they were created from a remove that does not exist in "real-world" based works. Specifically we will be examining the governing power (in any particular Mars-based science fiction film) that might be either wielded by business interests or governmental interests. Although it is possible to have both a strong government and a strong business in a society, in many Mars-based science fiction films, government and business seem to represent two sides of a continuum. The stronger the business power structure in the film, the weaker the governmental power structure, and vice-versa.
基金Supported by the National Foundation of China(50974055)the Program for Changjiang Scholars and Innovative Research Team in University(IRT0618)Henan Province Basic and Leading-edge Technology Research Program(082300463205)
文摘A relatively perfect coalmine fire risk-evaluating and order-arranging model that includes sixteen influential factors was established according to the statistical information of the fully mechanized coalface ground on the uncertainty measure theory. Then the single-index measure function of sixteen influential factors and the calculation method of computing the index weight ground on entropy theory were respectively established. The value assignment of sixteen influential factors was carried out by the qualitative analysis and observational data, respectively, in succession. The sequence of fire danger class of four experimental coalfaces could be obtained by the computational aids of Matlab according to the confidence level criterion. Some conclusions that the fire danger class of the No.l, No.2 and No.3 coalface belongs to high criticality can be obtained. But the fire danger class of the No.4 coalface belongs to higher criticality. The fire danger class of the No.4 coalface is more than that of the No.2 coalface. The fire danger class of the No.2 coalface is more than that of the No.1 coalface. Finally, the fire danger class of the No.1 coalface is more than that of the No.3 coalface.
文摘A new generation conical spray system for conventional diesel engines or premixed combustion diesel engines is introduced. By means of oriented impingement method, flexible spray penetration in design is realized. High-speed photograph was used to investigate the spatial distribution characteristics of the new spray for cases of different impingement angles and needle valve opening pressures. The results show that, by applying spray impingement orientation, fuel jets spread along the cone surface as shape of sectors, so the dispersion of jets is increased obviously. Changing on impingement angle leads to variation of penetration, which is critical in homogeneous mixture preparation. Due to the flexibility of spray penetration in design, the spray impingement on liner is avoided in a great extent. The results also indicate that higher needle valve opening pressure results in longer penetration and larger spray angle after impingement. Combustion characteristics of the impinged conical spray were studied in the 1135 type diesel engine. The new impinged conical spray system work smoothly in full load range with better fuel economy and lower emissions of NOx and soot than the original test engine.
文摘The thermal conductivity values of ordinary concrete can be adjusted to those prescribed in constructions by entraining air bubbles to reduce the density of concrete in order to achieve good thermal insulation. This paper concerns the analysis of air bubble distribution in concrete obtained by micro X-ray μCT (computed tomography) and correlates it with its thermal conductivity (k). The samples were prepared of ordinary concrete varying the density by air-entraining additives, ranging between 2,277 kg/m3 and 1,779 kg/m3, aiming to correlate the mechanical properties and k with the characteristics of the bubble distribution. The results show that air-entrainment leads to viable use of this material as sealer to achieve good thermal insulation, and it can be adjusted, but there seems to be a limit to air entraining. By analysis of the μCT images, it was possible to correlate the more quantity of bubbles of smaller diameter with the minor k, in dry or wet state, and to prove that there is a limit in the entrapped air content, and if it is exceeded, the coalescence occurs.
基金supported by Nanjing Maternity and Child Health Care Hospital
文摘Objective To investigate the blood lead levels (BLLs) in the duration of pregnancy and 6-12 weeks after delivery, and analyze the influencing factors of BLLs in healthy pregnant women. Methods Pregnant women were recruited from September 2009 to February 2010 at the prenatal clinic in Nanjing Maternity and Child Health Care Hospital. Altogether 174 healthy pregnant women without pregnant or obstetric complications or abnormal pregnancy outcomes were enrolled as the gravida group, and 120 healthy non-pregnant women as the control group. BLLs during pregnancy were determined by flame atomic absorption spectroscopy. Results BLLs in all the three pregnancy trimesters and postpartum were 59.8±24.3, 55.4±20.1, 55.9±19.7, and 67.6±17.4 μ/L, respectively, and the mean BLL in control group was 67.5±21.3 μg/L. BLLs during all the three trimesters were lower in the gravida group than in the control group (P=0.043, 0.021, and 0.028). Furthermore, occupations, nutrients supplementation, and time of house/apartment painted were associated with BLLs in pregnant women. Lead-related occupations, cosmetics use, and living in a house painted less than 1 year before are risk factors of high BLLs among pregnant women, while calcium, iron, zinc, and milk supplements are protective factors. Conclusion Supplementing calcium, iron, zinc, and milk, or avoiding contact with risk factors may help people, especially pregnant women, to reduce lead exposure.
基金the National Science and Technology Support Program(2012BAC16B01,2012BAC16B02)National Natural Science Foundation of China(41172313)
文摘Dragon fruit (Hylocereus undulates) was planted in a large area of karst region in recent years. To understand whether karst drought may impact on its physiological process is important and useful for planning and management of this fruit. In this study, we contrasted with a relative species Hylocereus undatus, and set up experiment to study physiological and biochemical trait and its response to different karst soil water level deficiency, so as to understand the mechanism of H. undulates and H. undatus in adaptation to karst drought condition. The results showed that, trends of physiological and biochemical response to drought was similar between two species. With the intensive of soil water deficiency, such toxin substance as malonaldehyde (MDA) increased, but meanwhile, two protective enzymes superoxide dismutase (SOD) and peroxidases (POD) and osmotic adjustment Proline (Pro) increase as well. Under relative water content (RWC) 〉50% condition, the enzyme can effectively protect the cells from toxin MDA injure, and Pro can also maintain the water needs through osmotic adjustment. However, under RWC 〈 40% condition, protective enzymes were not enough for cleaning MDA. Biomass was largest under RWC=70%-80%, with low root shoot ratio and high aboveground biomass. Biomass significantly decreased under RWC 30%-40%, which decline by 73.28% and 73.56% in H. undulates and H. undatus respectively. Therefore, RWC=70%-80% would be an optimal soil moisture while developing dragon fruit in karst, which is favor to fruit production. Under moderate drought e.g. RWC=50%-60%, plants may regulate by metabolic process and balance unfavorable substance, but it allocated much more biomass to root, reduced the aboveground biomass, which is not advance for fruit production.
基金sponsored by National Natural Science Foundation of China(61571189,61503137)State Administration of Foreign Experts Affairs for supporting the project‘Overseas Expertise Introduction Programme for Disciplines Innovation in Universities’(ref:B13009)
文摘To address the increasing demands on pollution control and energy saving, the study of low-emission and high-efficiency burners has been emphasized worldwide. Swirl-induced environmental burners(EV-burners), have notable features aligned with these requirements. In this study, an EV burner is investigated by both an ECT system and an OH-PLIF system. The aim is to detect the structure of a flame and obtain more information about the combustion process in an EV burner. 3D ECT sensitivity maps are generated for the measurement and OH-PLIF images are acquired in the same combustion zone as for the ECT measurements. The experimental images of a flame by ECT are in good agreement with the OH radical distribution pictures captured by OH-PLIF, which provide a mutual verification of the visualization method.
基金Financially supported by State Administration of Foreign Experts Affairs for supporting the project‘Overseas Expertise Introduction Program for Disciplines Innovation in Universities’(ref:B13009)the National Natural Science Foundation of China projects(61571189,61503137,61305056)
文摘Tomographic techniques have great abilities to interrogate the combustion processes, especially when it is combined with the physical models of the combustion itself. In this study, a data fusion algorithm is developed to investigate the flame distribution of a swirl-induced environmental(EV) burner, a new type of burner for low NOx combustion. An electric capacitance tomography(ECT) system is used to acquire 3D flame images and computational fluid dynamics(CFD) is applied to calculate an initial distribution of the temperature profile for the EV burner. Experiments were also carried out to visualize flames at a series of locations above the burner. While the ECT images essentially agree with the CFD temperature distribution, discrepancies exist at a certain height. When data fusion is applied, the discrepancy is visibly reduced and the ECT images are improved. The methods used in this study can lead to a new route where combustion visualization can be much improved and applied to clean energy conversion and new burner development.
基金supported by the National Natural Science Foundation of China (No.51036007)
文摘The phenomena of flame spread over aviation kerosene with an obstacle in liquid phase are investigated experimentally through surface temperature measurement by using infrared camera,schlieren images of subsurface flow in front of and behind obstacle and residence time of flame obtained from video recording.Experimental results reveal that obstacle has no effect on gas phase controlled flame spread.But for liquid phase controlled flame spread,flame can be stopped by an obstacle with its top edge flush with oil surface,and the residence time decreases with the increase of initial temperature of fuel.That conduction and radiation only play a subsidiary role in flame spread over liquid fuel was proved by schlieren images and surface temperature profiles.