To reduce the shielding effect of hardened layers on electrical resistivity tomography,a ratio method based on the distortion correction principle and the isolation coefficient is proposed.The effects of the resistivi...To reduce the shielding effect of hardened layers on electrical resistivity tomography,a ratio method based on the distortion correction principle and the isolation coefficient is proposed.The effects of the resistivity and thickness of hardened concrete layers on the detection of target objects are explored.Both numerical simulations and indoor tank tests indicate that when the ratio method is employed to correct the original collected data,the maximum allowable error for the isolation coefficient should not exceed 1%.Notably,when the ratio of hardened layer thickness to electrode spacing does not exceed 1,correction through this method significantly enhances the recognition capability of target objects.However,when the hardened layer thickness is greater than the electrode spacing by a factor of 2 or more,the ratio method cannot achieve satisfactory results.The case study of flood control engineering detection in the Zhangxi section of the Huangpen River in Dongzhi County demonstrates that the detection effect after correction by the ratio method is comparable to that for the adjacent unhardened pavement,and the influence of the hardened layer is obviously weakened,resulting in more reliable results.展开更多
Aim To obtain a kind of electrorheological (ER) flind with high comprehensive properties in order to satisfy the needs of engineering application. Methods A new type of dispersed phase── composite ultrafine particle...Aim To obtain a kind of electrorheological (ER) flind with high comprehensive properties in order to satisfy the needs of engineering application. Methods A new type of dispersed phase── composite ultrafine particles (UFP) was obtained by the method of microemulsion, which was used to mix with silicon oil. aam electroinduced stress and apparent viscosity of the ER fluids with three different volume fractions were tested under the conditions of different temperatures, electric fields and shear rates. Results A series of systematic tests show that the new type of ER fluids with volume fraction of 30% possesses obvious ER effect. Conclusion The double layers polarization plays an important role in ER effect.展开更多
The saturation behavior of stress current is studied.The three types of precursor sites for trap generation are also introduced by fitting method based on first order rate equation.A further investigation by statistic...The saturation behavior of stress current is studied.The three types of precursor sites for trap generation are also introduced by fitting method based on first order rate equation.A further investigation by statistics experiments shows that there are definite relationships among time constant of trap generation,the time to breakdown,and stress voltage.It also means that the time constant of trap generation can be used to predict oxide lifetime.This method is faster for TDDB study compared with usual breakdown experiments.展开更多
Based on the MASNUM wave-tide-circulation coupled numerical model, seasonal variability of thermocline in the Yellow Sea was simulated and compared with in-situ observations. Both simulated mixed layer depth (MLD) and...Based on the MASNUM wave-tide-circulation coupled numerical model, seasonal variability of thermocline in the Yellow Sea was simulated and compared with in-situ observations. Both simulated mixed layer depth (MLD) and thermocline intensity have similar spatial patterns to the observations. The simulated maximum MLD are 8 m and 22 m, while the corresponding observed values are 13 m and 27 m in July and October, respectively. The simulated thermocline intensity are 1.2℃/m and 0.5℃/m in July and October,respectively, which are 0.6℃/m less than those of the observations. It may be the main reason why the simulated thermocline is weaker than the observations that the model vertical resolution is less precise than that of the CTD data which is 1 m. Contours of both simulated and observed thermocline intensity present a circle in general. The wave-induced mixing plays a key role in the formation of the upper mixed layer in spring and summer. Tidal mixing enhances the thermocline intensity. Buoyancy-driven mixing destroys the thermocline in autumn and keeps the vertical temperature uniform in winter.展开更多
According to the different engineering mechanical states of top coal caving andnormal stoping of gaseous loose thick coal seams,the dialectical relation between thiscaving method and dynamic disasters was analyzed by ...According to the different engineering mechanical states of top coal caving andnormal stoping of gaseous loose thick coal seams,the dialectical relation between thiscaving method and dynamic disasters was analyzed by simulating the change of stressstates in the process of top coal initial caving with different mining and caving ratios basedon the ANSYS10.0.The variation of elastic energy and methane expansion energy duringfirst top coal caving was analyzed by first weighting and periodic weighting and combiningwith coal stress and deformation distribution of top coal normal stoping as well as positiveand negative examples in top coal caving of outburst coal seam.The research shows thatthe outburst risk increases along with the increase of the caving ratio in the initial miningstage.In the period of normal stoping,when the mining and caving ratio is smaller than1:3 and hard and massive overlying strata do not exist (periodic weighting is not obvious),it is beneficial to control ground stress leading type outburst.Thus,it is unreasonable toprohibit top coal caving in dangerous and outburst prone areas.展开更多
In this paper, we use the conductivity-temperature-depth (CTD) observation data and a three-dimensional ocean model in a seasonally-varying forcing field to study the barrier layer (BL) in the PN section in the East C...In this paper, we use the conductivity-temperature-depth (CTD) observation data and a three-dimensional ocean model in a seasonally-varying forcing field to study the barrier layer (BL) in the PN section in the East China Sea (ECS). The BL can be found along the PN section with obviously seasonal variability. In winter, spring and autumn, the BL occurs around the slope where the cold shelf water meets with the warm Kuroshio water. In summer, the BL can also be found in the shelf area near salinity front of the Changjiang (Yangtze) River Dilution Water (YRDW). Seasonal variations of BL in the PN section are caused by local hydrological characteristics and seasonal variations of atmospheric forcing. Strong vertical convection caused by sea surface cooling thickens the BL in winter and spring in the slope area. Due to the large discharge of Changjiang River in summer, the BL occurs extensively in the shelf region where the fresh YRDW and the salty bottom water meet and form a strong halocline above the seasonal thermocline. The formation mechanism of BL in the PN section can be explained by the vertical shear of different water masses, which is called the advection mechanism. The interannual variation of BL in summer is greatly affected by the YRDW. In the larger YRDW year (such as 1998), a shallow but much thicker BL existed on the shelf area.展开更多
By using 40-year NCEP reanalysis daily data (1958-1997), we have analyzed the climatic characteristics of summer monsoon onset in the South China Sea (105E ~ 120E, 5N ~ 20N, to be simplified as SCS in the text followe...By using 40-year NCEP reanalysis daily data (1958-1997), we have analyzed the climatic characteristics of summer monsoon onset in the South China Sea (105E ~ 120E, 5N ~ 20N, to be simplified as SCS in the text followed) pentad by pentad (5 days). According to our new definition, in the monsoon area of the SCS two of the following conditions should be satisfied: 1) At 850hPa, the southwest winds should be greater than 2m/s. 2) At 850 hPa, seq should be greater than 335K. The new definition means that the summer monsoon is the southwest winds with high temperature and high moisture. The onset of the SCS summer monsoon is defined to start when one half of the SCS area (105E ~ 120E,5N ~ 20N) is controlled by the summer monsoon. The analyzed results revealed the following: 1) The summer monsoon in the SCS starts to build up abruptly in the 4th pentad in May. 2) The summer monsoon onset in the SCS is resulted from the development and intensification of southwesterly monsoon in the Bay of Bengal. 3) The onset of the summer monsoon and establishment of the summer monsoon rainfall season in the SCS occur simultaneously. 4) During the summer monsoon onset in the SCS, troughs deepen and widen quickly in the lower troposphere of the India; the subtropical high in the Western Pacific moves eastward off the SCS in the middle troposphere; the easterly advances northward over the SCS in the upper troposphere.展开更多
Fertile topsoil was added onto the surface of barren slope land in Three Gorges Reservoir region of China in an anthropogenic process known as the foreign soil reconstruction project. The main goal of this paper was t...Fertile topsoil was added onto the surface of barren slope land in Three Gorges Reservoir region of China in an anthropogenic process known as the foreign soil reconstruction project. The main goal of this paper was to reveal the influence of anthropogenic activities on pedogenic processes and soil classifications. Chemical weathering indices and comparative analysis were applied to discuss changes in geochemical compositions and weathering features of purplish soils(Cambisols) before and after the project. Results showed that:(1) The foreign soil reconstruction project slightly altered the major element composition of topsoil and improved the soil structure. Although the distributions of major elements in the original topsoil, original subsoil, foreign topsoil and newly constructed topsoil were all similar to that in upper continental crust, newly constructed topsoil was the most similar soil.(2) The chemical index of alteration was more sensitive than the weathering index of Parker at indicating chemical weathering status of purplish soil. The chemical weathering status of newly constructed topsoil was higher than that of the original topsoil and lower than that of foreign topsoil.(3) Anthropogenic activities may provide a promising new thought for the anthropogenic soil classification system. The scope and subgroups of Anthrosols should be extended and strengthened. Or there may be a need to combine Anthrosols and Technosols orders to create a new soil order. The results may be used for optimizing soil mellowing engineering activities and enriching the soil classification system.展开更多
By monitoring the ionizing radiation from minute to minute in S^o Jos6 dos Campos, SP, Brazil (230 S, 450 W) using Geiger counter, during January to August 2015, it has confirmed the presence of radon gas in these m...By monitoring the ionizing radiation from minute to minute in S^o Jos6 dos Campos, SP, Brazil (230 S, 450 W) using Geiger counter, during January to August 2015, it has confirmed the presence of radon gas in these measures. The observation confirms the existence of a periodicity of 24 hours through the technique (Fast Fourier Transform) applied to the data set, and this cycle can be better visible in longer dry periods. On rainy days or with heavy fog in the region, this periodicity is modified or even disappears. As Geiger do not detect alpha particles due to absorption in the walls of the sensor tube, it measured X and gamma rays coming from the radon gas progeny. Radon gas (222Rn) has a half-life of 19.7 minutes to decays in 214Bi emitting gamma ray energy (45%) with 0.609 MeV which is monitored daily by Geiger. Also 222Rn decays in 26.8 minutes in 214pb giving (37%) with 0.35 MeV and others with less energy. It is confirmed the good performance ofa Geiger tube with LND 712 working with about 500 VDC rated voltage.展开更多
Hot compression was performed on a multilayered Au−20Sn eutectic alloy to investigate the deformation behavior and microstructure evolution.During hot compression,microstructural spheroidization was initiated from pla...Hot compression was performed on a multilayered Au−20Sn eutectic alloy to investigate the deformation behavior and microstructure evolution.During hot compression,microstructural spheroidization was initiated from plastic instability regions,and it was preferentially activated in vertical lamellae with a growth direction parallel to the compressive direction.Continuous dynamic recrystallization associated with lattice dislocations was the mechanism in both AuSn and Au5Sn multilayers.After spheroidization,strain accumulations were weakened in both of the equiaxed phases,and the deformation mechanism was substantially replaced by grain boundary sliding and migration.Based on these findings,hot rolling was conducted on an as-cast Au−20Sn alloy and a foil with a thickness of~50μm was successfully prepared.The present study can promote the development of Au−20Sn foils,and provide insights into the deformation behavior and microstructure evolution of multilayered eutectic alloys.展开更多
Influencing factors, and variations and trends of Antarctic ozone hole in recent decades are analyzed, and sudden change processes of ozone at Zhongshan station and the effect of atmospheric dynamic processes on ozone...Influencing factors, and variations and trends of Antarctic ozone hole in recent decades are analyzed, and sudden change processes of ozone at Zhongshan station and the effect of atmospheric dynamic processes on ozone changes are also discussed by using the satellite ozone data and the ground-measured ozone data at two Antarctic stations as well as the NCEP/NCAR reanalysis data. The results show that equivalent effective stratospheric chlorine (EESC) and stratospheric temperature are two important factors influencing the ozone hole. The column ozone at Zhongshan and Syowa stations is significantly related with EESC and stratospheric temperature, which means that even though the two stations are both located on the edge of the ozone hole, EESC and stratospheric temperature still played a very important role in column ozone changes, and mean while verifies that EESC is applicable on the coast of east Antarctic continent. Decadal changes in EESC are similar with those of the ozone hole, and inter-annual variations of ozone are closely related with stratospheric temperature. Based on the relation of EESC and ozone hole size, it can be projected that the ozone hole size will gradually reduce to the 1980's level from 2010 to around 2070. Of course there might exist many uncertainties in the projection, which therefore needs to be further studied.展开更多
Weak stratospheric polar vortex(WPV)events during winter months were investigated.WPV events were identified as being weakest in December,accompanied by the most dramatic increase in geopotential height over the polar...Weak stratospheric polar vortex(WPV)events during winter months were investigated.WPV events were identified as being weakest in December,accompanied by the most dramatic increase in geopotential height over the polar region.After the onset of a December WPV event,the dynamic processes influencing Eurasian temperature can be split into two separate periods.Period I(lag of 0-25 days)is referred to as the stratosphere-troposphere interactions period,as it is mainly characterized by stratospheric signals propagating downwards.In Period I,a stratospheric negative Northern Annular Mode(NAM)pattern associated with the WPV propagates downwards,inducing a negative NAM in the troposphere.The anomalous low centers over the Mediterranean and North Pacific bring cold advection to northern Eurasia,resulting in a north-cold-south-warm dipole pattern over Eurasia.The zero line between negative and positive temperature anomalies moves southwards during days 5-20.Stratospheric cold anomalies at midlatitudes propagate downwards to high latitudes in the troposphere and contribute to the dipole structure.During PeriodⅡ(lag of 25-40 days),as downward signals from the stratosphere have vanished,the dynamic processes mainly take place within the troposphere.Specifically,a wave train is initiated from the North Atlantic region to northern Europe.The propagation of wave activity flux intensifies a cyclonic anomaly over northern Europe,which brings cold advection to Scandinavia and warm advection to central Asia.Therefore,a northwest-cold-southeast-warm dipole structure occupies Eurasia and migrates southeastwards during this period.展开更多
Measurements of litter production, and the surface litter pool were made over a 1 year period in a tropical transitional forest near Sinop, Mato Grosso Brazil with the aim of quantifying the seasonal variation of nitr...Measurements of litter production, and the surface litter pool were made over a 1 year period in a tropical transitional forest near Sinop, Mato Grosso Brazil with the aim of quantifying the seasonal variation of nitrogen and phosphorus in the litter and the annual contribution of nutrients to the soil. Average annual litterfall (+95% confidence interval (CI)) was 8.20 ton.ha^-1 year^-1 and forest floor litter mass was 58.63 ton'hal. Nitrogen and phosphorus in the forest floor litter mass was highest during the dry and dry-wet season, being 38% higher than in the wet and wet-dry season. Seasonal variation in the litter and concentration of nutrients was explained by seasonal variations in the climate, for example in the precipition and soil humidity. Average annual nitrogen and phosphorus concentrations in the forest floor mass were 17.24 ton.ha^-1 and 16.46 ton.ha^-1, respectively. The more significant forest floor mass fraction for returning soil nutrients was the leaves. The concentration of nutrients was higher in the soil superficial layer (at depths between 0-5 cm) than at depths between 30-70 cm, approximately 83% and 93% for total nitrogen and available phosphorus, respectively.展开更多
Four climatologies on a monthly scale (January, April, May and November) of chlorophyll a within the South China Sea (SCS) were calculated using a Coastal Zone Color Scanner (CZCS) (1979-1983) and the Sea-viewing Wide...Four climatologies on a monthly scale (January, April, May and November) of chlorophyll a within the South China Sea (SCS) were calculated using a Coastal Zone Color Scanner (CZCS) (1979-1983) and the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) (1998-2002). We analyzed decadal variability of chlorophyll a by comparing the products of the two observation periods. The relationships of variability in chlorophyll a with sea surface wind speed (SSW), sea surface temperature (SST), wind stress (WS), and mixed layer depth (MLD) were determined. The results indicate that there is obvious chlorophyll a decadal variability in the SCS. The decadal chlorophyll a presents distinct seasonal variability in characteristics, which may be as a result of various different dynamic processes. The negative chlorophyll a concentration anomaly in January was associated with the warming of SST and a shallower MLD. Generally, there were higher chlorophyll a concentrations in spring during the SeaWiFS period compared with the CZCS period. However, the chlorophyll a concentration exhibits some regional differences during this season, leading to an explanation being difficult. The deepened MLD may have contributed to the positive chlorophyll a concentration anomalies from the northwestern Luzon Island to the northeastern region of Vietnam during April and May. The increases of chlorophyll a concentration in northwestern Borneo during May may be because the stronger SSW and higher WS produce a deeper mixed layer and convective mixing, leading to high levels of nutrient concentrations. The higher chlorophyll a off southeastern Vietnam may be associated with the advective transport of the colder water extending from the Karimata Strait to southeastern Vietnam.展开更多
By using the observational O3 data of Kunming and Hong Kong during the period of 1997 – 2001, the paper studies the distribution and variation of total ozone in low latitude region of China. The study shows that the ...By using the observational O3 data of Kunming and Hong Kong during the period of 1997 – 2001, the paper studies the distribution and variation of total ozone in low latitude region of China. The study shows that the characteristics of variation in Kunming and Hong Kong are very similar, and the total ozone in the western areas is larger than in the eastern ones. It is maximum in summer and minimum in winter.展开更多
The central structure belt in Turpan-Hami basin is composed of the Huoyanshan structure and Qiketai structure formed in late Triassic-early Jurassic, and is characterized by extensional tectonics. The thickness of str...The central structure belt in Turpan-Hami basin is composed of the Huoyanshan structure and Qiketai structure formed in late Triassic-early Jurassic, and is characterized by extensional tectonics. The thickness of strata in the hanging wall of the growth fault is obviously larger than that in the footwall,and a deposition center was evolved in the Taibei sag where the hanging wall of the fault is located. In late Jurassic the collision between Lhasa block and Eurasia continent resulted in the transformation of the Turpan-Hami basin from an extensional structure into a compressional structure, and consequently in the tectonic inversion of the central structure belt of the Turpan-Hami basin from the extensional normal fault in the earlier stage to the compressive thrust fault in the later stage. The Tertiary collision between the Indian plate and the Eurasian plate occurred around 55Ma, and this Himalayan orogenic event has played a profound role in shaping the Tianshan area, only the effect of the collision to this area was delayed since it culminated here approximately in late Oligocene-early Miocene. The central structure belt was strongly deformed and thrusted above the ground as a result of this tectonic event.展开更多
Waterborne acrylic emulsions modified with organic siloxanes and aziridine crosslinker were synthesized and applied as coating of controlled release fertilizer. The free films were characterized and the nutrient relea...Waterborne acrylic emulsions modified with organic siloxanes and aziridine crosslinker were synthesized and applied as coating of controlled release fertilizer. The free films were characterized and the nutrient release profiles of the coated fertilizers were determined. The results show that methyl silicone oil and methylsilanolate sodium could not improve water resistance performance and glass transition temperature Tgof coatings, while the firmness is enhanced. Aziridine crosslinker improves the water resistance performance, firmness and Tg. Incorporation of methyl silicone oil and aziridine crosslinker gives an excellent aqueous acrylic emulsion for coated controlled release fertilizer, with the 30-day cumulative nutrient release reduced to 16% and an estimated nutrient release duration over 190 days. Therefore, this waterborne coating is promising to meet the requirements for controlled release of nutrient and environmental protection.展开更多
The importance of simultaneous coal and methane extraction and its significance on green exploitation is stated, and current research situation of simultaneous coal and methane and faced new problems are introduced. T...The importance of simultaneous coal and methane extraction and its significance on green exploitation is stated, and current research situation of simultaneous coal and methane and faced new problems are introduced. The research progress on movement of overlying strata and stresses change in them, cracks development during mining in overlying strata and meth- ane emission under disturbance of mining as well as the changing rules of permeability and methane flow under the disturbance of mining is analyzed. The progress on practice of simultaneous coal and methane extraction is analyzed. The deficiencies of current research and further researching fields on simultaneous coal and methane extraction are pointed out.展开更多
基金National Key Research and Development Program of China(No.2021YFC3000103).
文摘To reduce the shielding effect of hardened layers on electrical resistivity tomography,a ratio method based on the distortion correction principle and the isolation coefficient is proposed.The effects of the resistivity and thickness of hardened concrete layers on the detection of target objects are explored.Both numerical simulations and indoor tank tests indicate that when the ratio method is employed to correct the original collected data,the maximum allowable error for the isolation coefficient should not exceed 1%.Notably,when the ratio of hardened layer thickness to electrode spacing does not exceed 1,correction through this method significantly enhances the recognition capability of target objects.However,when the hardened layer thickness is greater than the electrode spacing by a factor of 2 or more,the ratio method cannot achieve satisfactory results.The case study of flood control engineering detection in the Zhangxi section of the Huangpen River in Dongzhi County demonstrates that the detection effect after correction by the ratio method is comparable to that for the adjacent unhardened pavement,and the influence of the hardened layer is obviously weakened,resulting in more reliable results.
文摘Aim To obtain a kind of electrorheological (ER) flind with high comprehensive properties in order to satisfy the needs of engineering application. Methods A new type of dispersed phase── composite ultrafine particles (UFP) was obtained by the method of microemulsion, which was used to mix with silicon oil. aam electroinduced stress and apparent viscosity of the ER fluids with three different volume fractions were tested under the conditions of different temperatures, electric fields and shear rates. Results A series of systematic tests show that the new type of ER fluids with volume fraction of 30% possesses obvious ER effect. Conclusion The double layers polarization plays an important role in ER effect.
文摘The saturation behavior of stress current is studied.The three types of precursor sites for trap generation are also introduced by fitting method based on first order rate equation.A further investigation by statistics experiments shows that there are definite relationships among time constant of trap generation,the time to breakdown,and stress voltage.It also means that the time constant of trap generation can be used to predict oxide lifetime.This method is faster for TDDB study compared with usual breakdown experiments.
文摘Based on the MASNUM wave-tide-circulation coupled numerical model, seasonal variability of thermocline in the Yellow Sea was simulated and compared with in-situ observations. Both simulated mixed layer depth (MLD) and thermocline intensity have similar spatial patterns to the observations. The simulated maximum MLD are 8 m and 22 m, while the corresponding observed values are 13 m and 27 m in July and October, respectively. The simulated thermocline intensity are 1.2℃/m and 0.5℃/m in July and October,respectively, which are 0.6℃/m less than those of the observations. It may be the main reason why the simulated thermocline is weaker than the observations that the model vertical resolution is less precise than that of the CTD data which is 1 m. Contours of both simulated and observed thermocline intensity present a circle in general. The wave-induced mixing plays a key role in the formation of the upper mixed layer in spring and summer. Tidal mixing enhances the thermocline intensity. Buoyancy-driven mixing destroys the thermocline in autumn and keeps the vertical temperature uniform in winter.
文摘According to the different engineering mechanical states of top coal caving andnormal stoping of gaseous loose thick coal seams,the dialectical relation between thiscaving method and dynamic disasters was analyzed by simulating the change of stressstates in the process of top coal initial caving with different mining and caving ratios basedon the ANSYS10.0.The variation of elastic energy and methane expansion energy duringfirst top coal caving was analyzed by first weighting and periodic weighting and combiningwith coal stress and deformation distribution of top coal normal stoping as well as positiveand negative examples in top coal caving of outburst coal seam.The research shows thatthe outburst risk increases along with the increase of the caving ratio in the initial miningstage.In the period of normal stoping,when the mining and caving ratio is smaller than1:3 and hard and massive overlying strata do not exist (periodic weighting is not obvious),it is beneficial to control ground stress leading type outburst.Thus,it is unreasonable toprohibit top coal caving in dangerous and outburst prone areas.
基金Supported by National Basic Research Program of China (973 Program, No. 2005CB422303 and 2007CB411804)the Key Project of the International Science and Technology Cooperation Program of China (No. 2006DFB21250)+1 种基金the "111 Project" of the Ministry of Education (No. B07036)the Program for New Century Excellent Talents in University, China (No. NECT-07-0781)
文摘In this paper, we use the conductivity-temperature-depth (CTD) observation data and a three-dimensional ocean model in a seasonally-varying forcing field to study the barrier layer (BL) in the PN section in the East China Sea (ECS). The BL can be found along the PN section with obviously seasonal variability. In winter, spring and autumn, the BL occurs around the slope where the cold shelf water meets with the warm Kuroshio water. In summer, the BL can also be found in the shelf area near salinity front of the Changjiang (Yangtze) River Dilution Water (YRDW). Seasonal variations of BL in the PN section are caused by local hydrological characteristics and seasonal variations of atmospheric forcing. Strong vertical convection caused by sea surface cooling thickens the BL in winter and spring in the slope area. Due to the large discharge of Changjiang River in summer, the BL occurs extensively in the shelf region where the fresh YRDW and the salty bottom water meet and form a strong halocline above the seasonal thermocline. The formation mechanism of BL in the PN section can be explained by the vertical shear of different water masses, which is called the advection mechanism. The interannual variation of BL in summer is greatly affected by the YRDW. In the larger YRDW year (such as 1998), a shallow but much thicker BL existed on the shelf area.
基金National Scaling Project A The Scientific Experiment on South China Sea Monsoon
文摘By using 40-year NCEP reanalysis daily data (1958-1997), we have analyzed the climatic characteristics of summer monsoon onset in the South China Sea (105E ~ 120E, 5N ~ 20N, to be simplified as SCS in the text followed) pentad by pentad (5 days). According to our new definition, in the monsoon area of the SCS two of the following conditions should be satisfied: 1) At 850hPa, the southwest winds should be greater than 2m/s. 2) At 850 hPa, seq should be greater than 335K. The new definition means that the summer monsoon is the southwest winds with high temperature and high moisture. The onset of the SCS summer monsoon is defined to start when one half of the SCS area (105E ~ 120E,5N ~ 20N) is controlled by the summer monsoon. The analyzed results revealed the following: 1) The summer monsoon in the SCS starts to build up abruptly in the 4th pentad in May. 2) The summer monsoon onset in the SCS is resulted from the development and intensification of southwesterly monsoon in the Bay of Bengal. 3) The onset of the summer monsoon and establishment of the summer monsoon rainfall season in the SCS occur simultaneously. 4) During the summer monsoon onset in the SCS, troughs deepen and widen quickly in the lower troposphere of the India; the subtropical high in the Western Pacific moves eastward off the SCS in the middle troposphere; the easterly advances northward over the SCS in the upper troposphere.
基金the National Key Technology Research and Development Program of the Ministry of Science and Technology of China (Grant No. 2012BAD05B06)
文摘Fertile topsoil was added onto the surface of barren slope land in Three Gorges Reservoir region of China in an anthropogenic process known as the foreign soil reconstruction project. The main goal of this paper was to reveal the influence of anthropogenic activities on pedogenic processes and soil classifications. Chemical weathering indices and comparative analysis were applied to discuss changes in geochemical compositions and weathering features of purplish soils(Cambisols) before and after the project. Results showed that:(1) The foreign soil reconstruction project slightly altered the major element composition of topsoil and improved the soil structure. Although the distributions of major elements in the original topsoil, original subsoil, foreign topsoil and newly constructed topsoil were all similar to that in upper continental crust, newly constructed topsoil was the most similar soil.(2) The chemical index of alteration was more sensitive than the weathering index of Parker at indicating chemical weathering status of purplish soil. The chemical weathering status of newly constructed topsoil was higher than that of the original topsoil and lower than that of foreign topsoil.(3) Anthropogenic activities may provide a promising new thought for the anthropogenic soil classification system. The scope and subgroups of Anthrosols should be extended and strengthened. Or there may be a need to combine Anthrosols and Technosols orders to create a new soil order. The results may be used for optimizing soil mellowing engineering activities and enriching the soil classification system.
文摘By monitoring the ionizing radiation from minute to minute in S^o Jos6 dos Campos, SP, Brazil (230 S, 450 W) using Geiger counter, during January to August 2015, it has confirmed the presence of radon gas in these measures. The observation confirms the existence of a periodicity of 24 hours through the technique (Fast Fourier Transform) applied to the data set, and this cycle can be better visible in longer dry periods. On rainy days or with heavy fog in the region, this periodicity is modified or even disappears. As Geiger do not detect alpha particles due to absorption in the walls of the sensor tube, it measured X and gamma rays coming from the radon gas progeny. Radon gas (222Rn) has a half-life of 19.7 minutes to decays in 214Bi emitting gamma ray energy (45%) with 0.609 MeV which is monitored daily by Geiger. Also 222Rn decays in 26.8 minutes in 214pb giving (37%) with 0.35 MeV and others with less energy. It is confirmed the good performance ofa Geiger tube with LND 712 working with about 500 VDC rated voltage.
基金financial supports from the National Natural Science Foundation of China(Nos.U1502272,51901204)the Precious Metal Materials Genome Engineering in Yunnan Province,China(Nos.2019ZE001,202002AB080001)。
文摘Hot compression was performed on a multilayered Au−20Sn eutectic alloy to investigate the deformation behavior and microstructure evolution.During hot compression,microstructural spheroidization was initiated from plastic instability regions,and it was preferentially activated in vertical lamellae with a growth direction parallel to the compressive direction.Continuous dynamic recrystallization associated with lattice dislocations was the mechanism in both AuSn and Au5Sn multilayers.After spheroidization,strain accumulations were weakened in both of the equiaxed phases,and the deformation mechanism was substantially replaced by grain boundary sliding and migration.Based on these findings,hot rolling was conducted on an as-cast Au−20Sn alloy and a foil with a thickness of~50μm was successfully prepared.The present study can promote the development of Au−20Sn foils,and provide insights into the deformation behavior and microstructure evolution of multilayered eutectic alloys.
基金supported by the program of China Polar Environment Investigation and Assessment(2011-2015)the National Nature Science Foundation of China (No. 41076132)
文摘Influencing factors, and variations and trends of Antarctic ozone hole in recent decades are analyzed, and sudden change processes of ozone at Zhongshan station and the effect of atmospheric dynamic processes on ozone changes are also discussed by using the satellite ozone data and the ground-measured ozone data at two Antarctic stations as well as the NCEP/NCAR reanalysis data. The results show that equivalent effective stratospheric chlorine (EESC) and stratospheric temperature are two important factors influencing the ozone hole. The column ozone at Zhongshan and Syowa stations is significantly related with EESC and stratospheric temperature, which means that even though the two stations are both located on the edge of the ozone hole, EESC and stratospheric temperature still played a very important role in column ozone changes, and mean while verifies that EESC is applicable on the coast of east Antarctic continent. Decadal changes in EESC are similar with those of the ozone hole, and inter-annual variations of ozone are closely related with stratospheric temperature. Based on the relation of EESC and ozone hole size, it can be projected that the ozone hole size will gradually reduce to the 1980's level from 2010 to around 2070. Of course there might exist many uncertainties in the projection, which therefore needs to be further studied.
基金supported by the National Natural Science Foundation of China [grant numbers 41730964,41575079,and 41421004]
文摘Weak stratospheric polar vortex(WPV)events during winter months were investigated.WPV events were identified as being weakest in December,accompanied by the most dramatic increase in geopotential height over the polar region.After the onset of a December WPV event,the dynamic processes influencing Eurasian temperature can be split into two separate periods.Period I(lag of 0-25 days)is referred to as the stratosphere-troposphere interactions period,as it is mainly characterized by stratospheric signals propagating downwards.In Period I,a stratospheric negative Northern Annular Mode(NAM)pattern associated with the WPV propagates downwards,inducing a negative NAM in the troposphere.The anomalous low centers over the Mediterranean and North Pacific bring cold advection to northern Eurasia,resulting in a north-cold-south-warm dipole pattern over Eurasia.The zero line between negative and positive temperature anomalies moves southwards during days 5-20.Stratospheric cold anomalies at midlatitudes propagate downwards to high latitudes in the troposphere and contribute to the dipole structure.During PeriodⅡ(lag of 25-40 days),as downward signals from the stratosphere have vanished,the dynamic processes mainly take place within the troposphere.Specifically,a wave train is initiated from the North Atlantic region to northern Europe.The propagation of wave activity flux intensifies a cyclonic anomaly over northern Europe,which brings cold advection to Scandinavia and warm advection to central Asia.Therefore,a northwest-cold-southeast-warm dipole structure occupies Eurasia and migrates southeastwards during this period.
文摘Measurements of litter production, and the surface litter pool were made over a 1 year period in a tropical transitional forest near Sinop, Mato Grosso Brazil with the aim of quantifying the seasonal variation of nitrogen and phosphorus in the litter and the annual contribution of nutrients to the soil. Average annual litterfall (+95% confidence interval (CI)) was 8.20 ton.ha^-1 year^-1 and forest floor litter mass was 58.63 ton'hal. Nitrogen and phosphorus in the forest floor litter mass was highest during the dry and dry-wet season, being 38% higher than in the wet and wet-dry season. Seasonal variation in the litter and concentration of nutrients was explained by seasonal variations in the climate, for example in the precipition and soil humidity. Average annual nitrogen and phosphorus concentrations in the forest floor mass were 17.24 ton.ha^-1 and 16.46 ton.ha^-1, respectively. The more significant forest floor mass fraction for returning soil nutrients was the leaves. The concentration of nutrients was higher in the soil superficial layer (at depths between 0-5 cm) than at depths between 30-70 cm, approximately 83% and 93% for total nitrogen and available phosphorus, respectively.
基金Supported by the Knowledge Innovation Program of Chinese Academy of Sciences (Nos. KZCX1-YW-12-01, KZCX2-YW-Q11-02)the National Natural Science Foundation of China (Nos. 41006111, 40976106)the Project from Guangzhou City for the Pearl River New Star on Science and Technology (No. 2011J2200022)
文摘Four climatologies on a monthly scale (January, April, May and November) of chlorophyll a within the South China Sea (SCS) were calculated using a Coastal Zone Color Scanner (CZCS) (1979-1983) and the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) (1998-2002). We analyzed decadal variability of chlorophyll a by comparing the products of the two observation periods. The relationships of variability in chlorophyll a with sea surface wind speed (SSW), sea surface temperature (SST), wind stress (WS), and mixed layer depth (MLD) were determined. The results indicate that there is obvious chlorophyll a decadal variability in the SCS. The decadal chlorophyll a presents distinct seasonal variability in characteristics, which may be as a result of various different dynamic processes. The negative chlorophyll a concentration anomaly in January was associated with the warming of SST and a shallower MLD. Generally, there were higher chlorophyll a concentrations in spring during the SeaWiFS period compared with the CZCS period. However, the chlorophyll a concentration exhibits some regional differences during this season, leading to an explanation being difficult. The deepened MLD may have contributed to the positive chlorophyll a concentration anomalies from the northwestern Luzon Island to the northeastern region of Vietnam during April and May. The increases of chlorophyll a concentration in northwestern Borneo during May may be because the stronger SSW and higher WS produce a deeper mixed layer and convective mixing, leading to high levels of nutrient concentrations. The higher chlorophyll a off southeastern Vietnam may be associated with the advective transport of the colder water extending from the Karimata Strait to southeastern Vietnam.
基金National Natural Science Foundation of China (40265001) Natural Science Foundation ofYunnan Province (2002C0038M)Biography: ZHANG Xiu-nian (1968 –)+2 种基金 male native from Nantong city of Jiangsu Province postgraduate
文摘By using the observational O3 data of Kunming and Hong Kong during the period of 1997 – 2001, the paper studies the distribution and variation of total ozone in low latitude region of China. The study shows that the characteristics of variation in Kunming and Hong Kong are very similar, and the total ozone in the western areas is larger than in the eastern ones. It is maximum in summer and minimum in winter.
文摘The central structure belt in Turpan-Hami basin is composed of the Huoyanshan structure and Qiketai structure formed in late Triassic-early Jurassic, and is characterized by extensional tectonics. The thickness of strata in the hanging wall of the growth fault is obviously larger than that in the footwall,and a deposition center was evolved in the Taibei sag where the hanging wall of the fault is located. In late Jurassic the collision between Lhasa block and Eurasia continent resulted in the transformation of the Turpan-Hami basin from an extensional structure into a compressional structure, and consequently in the tectonic inversion of the central structure belt of the Turpan-Hami basin from the extensional normal fault in the earlier stage to the compressive thrust fault in the later stage. The Tertiary collision between the Indian plate and the Eurasian plate occurred around 55Ma, and this Himalayan orogenic event has played a profound role in shaping the Tianshan area, only the effect of the collision to this area was delayed since it culminated here approximately in late Oligocene-early Miocene. The central structure belt was strongly deformed and thrusted above the ground as a result of this tectonic event.
基金Supported by the National 12th Five-Year Science and Technology Supporting Program(2011BAD11B01)the Research & Development Projects Cooperation Project of Chinese Academy of Sciences(YDJDBNJ-2012-023)
文摘Waterborne acrylic emulsions modified with organic siloxanes and aziridine crosslinker were synthesized and applied as coating of controlled release fertilizer. The free films were characterized and the nutrient release profiles of the coated fertilizers were determined. The results show that methyl silicone oil and methylsilanolate sodium could not improve water resistance performance and glass transition temperature Tgof coatings, while the firmness is enhanced. Aziridine crosslinker improves the water resistance performance, firmness and Tg. Incorporation of methyl silicone oil and aziridine crosslinker gives an excellent aqueous acrylic emulsion for coated controlled release fertilizer, with the 30-day cumulative nutrient release reduced to 16% and an estimated nutrient release duration over 190 days. Therefore, this waterborne coating is promising to meet the requirements for controlled release of nutrient and environmental protection.
基金Supported by the National Science Foundation of China (51304006) the Key Project of Anhui Provincial Department of Education (KJ2011A075) the Youth Backbone Training Funds of Anhui University of Science &Technology (20120012)
文摘The importance of simultaneous coal and methane extraction and its significance on green exploitation is stated, and current research situation of simultaneous coal and methane and faced new problems are introduced. The research progress on movement of overlying strata and stresses change in them, cracks development during mining in overlying strata and meth- ane emission under disturbance of mining as well as the changing rules of permeability and methane flow under the disturbance of mining is analyzed. The progress on practice of simultaneous coal and methane extraction is analyzed. The deficiencies of current research and further researching fields on simultaneous coal and methane extraction are pointed out.