近年来随着无人机产业的迅猛发展,视觉定位技术已广泛应用于低成本轻量化的定位系统中,然而当无人机在水面等弱纹理区域飞行时,场景视觉特征稀疏且差异小,导致图像误匹配率激增,定位估计发散严重,限制了视觉定位技术在水域环境下的应用...近年来随着无人机产业的迅猛发展,视觉定位技术已广泛应用于低成本轻量化的定位系统中,然而当无人机在水面等弱纹理区域飞行时,场景视觉特征稀疏且差异小,导致图像误匹配率激增,定位估计发散严重,限制了视觉定位技术在水域环境下的应用。针对该问题提出了一种基于水纹识别的视觉定位技术(visual positioning technique based on water pattern recognition,WPRVP)。首先通过提取水纹多粒度相关特征得到相邻图像之间局部和全局的匹配关系;然后将匹配信息嵌入循环网络迭代处理,由粗到细逐步提高水纹图像的匹配精度;最后基于多视图几何约束进行匹配筛选和运动建模,实现了鲁棒的定位估计。实验结果表明,相比现有的图像匹配和视觉定位方法,WPRVP能够应用于水域环境且能保持更高的匹配与定位精度,能够为导航设备在水域场景下提供一个低成本高精度的导航信息源,辅助无人机执行水面飞行任务。展开更多
Biofilm-associated microorganisms play crucial roles in terrestrial and aquatic nutrient cycling and in the biodegradation of environmental pollutants. Biofilm formation was determined for a total of 18 bacterial isol...Biofilm-associated microorganisms play crucial roles in terrestrial and aquatic nutrient cycling and in the biodegradation of environmental pollutants. Biofilm formation was determined for a total of 18 bacterial isolates obtained from the biofilms of wastewater treatment systems and of little carpolite in soil. Among these isolates, seven showed strong biofilm-forming capacity. The phylogenetic affiliation of the isolates showing high biofilm formation capacity was determined through 16S rDNA sequencing and the isolates were grouped into 7 bacterial species including Pseudornonas sp., Pseudomonas putida, Aeromonas caviae, Bacillus cereus, Pseudornonas plecoglossicida, Aeromonas hydrophila, and Comamonas testosteroni. The biofilm-forming capacity was closely related with flagella, exopolysaccharide, and extracellular protein. According to the coefficient of determination, the relative importance of the five biological characteristics to biofilm formation was, in order from greatest to least, exopolysaccharide 〉 flagella 〉 N-acyl-homoserine lactones （AHLs） signaling molecules 〉 extracellular protein 〉 swarming motility.展开更多
Salidroside(SAL)is a phenolic substance with high solubility and low permeability,which make it easy to cause the efflux effect of P-glycoprotein and degradation of intestinal flora,resulting in lower bioavailability....Salidroside(SAL)is a phenolic substance with high solubility and low permeability,which make it easy to cause the efflux effect of P-glycoprotein and degradation of intestinal flora,resulting in lower bioavailability.The aim of this study was to develop and optimize a water-in-oil nanoemulsion of SAL(w/o SAL-N)to explore its suitability in oral drug delivery systems.In this work,SAL-N was successfully prepared by water titration method at K_(m)=1 to construct the pseudo-ternary phase diagrams.Physical characterization including the average viscosity,pH,refractive index,particle size,PDI,TEM,DSC,the content of SAL,and stability study were performed.It was evaluated for drug release in vitro and pharmacokinetic studies in vivo.The optimized nanoemulsion formulation consisted of Labrafil M 1944 CS(63%),Span-80/Tween-80/EtOH(27%)and 200 mg·mL^(-1) SAL solution(SAL-SOL)(10%).Low viscosity and suitable pH were expected for the nanoemulsion.The spherical morphology and nanoscale size of SAL-N enhanced the stability of the nanoemulsion system.In vitro drug release showed that SAL-N had a better controlled release property than SAL-SOL at earlier time points.The pharmacokinetic studies exhibited that SAL-N had significantly higher in t_(1/2)(2.11-fold),AUC_(0-48 h)(1.75-fold)and MRT0-48 h(2.63-fold)than SAL-SOL(P<0.01).The w/o SAL-N prepared in this work can be effectively delivered via the oral route.It can be seen w/o nanoemulsion is a strategy for the drug with polyphenols to delay the release,enhance oral absorption and reduce metabolic rate.展开更多
Furfural is an important inhibitor in ethanol fermentation process using lignocellulosic hydrolysates as raw materials. In order to find out the furfural concentration range in which furfural inhibits the fermentation...Furfural is an important inhibitor in ethanol fermentation process using lignocellulosic hydrolysates as raw materials. In order to find out the furfural concentration range in which furfural inhibits the fermentation process, we used one strain Saccharomyces kluyveri selected from soil and cultured in several different furfural content media under low glucose concentration condition. Experiment results showed that microorganism growth was stimulated and dry cell weight decreased when furfural concentration in the medium was 0.25 mg/ml. Furfural had negative effect on cell growth when its concentration was above 1.00 mg/ml. At the same time, the strain growed better and had a higher glucose consumption rate in 5% original glucose concentration condition than in 3% original glucose concentration condition. The results showed that appropriate exaltation of original glucose concentration in stalk hydrolysates will increase the strain resistance to furfural.展开更多
The dielectric constant of the lunar regolith can directly influence the reflection coefficient and the trans-mission coefficient of the Moon′s surface, and plays an important role in the Moon research. In order to s...The dielectric constant of the lunar regolith can directly influence the reflection coefficient and the trans-mission coefficient of the Moon′s surface, and plays an important role in the Moon research. In order to study the di-electric properties of the lunar regolith, the lunar regolith simulant was made according to the making procedure of the CAS-1 simulant made by Chinese Academy of Sciences. Then the dielectric constants of the lunar regolith simulant were measured with 85070E Aiglent Microwave Network Analyzer in the frequency ranging from 0.2 GHz to 20.0 GHz and at temperature of 25.1℃, 17.7℃, 13.1℃, 11.5℃, 9.6℃, 8.0℃, 4.1℃, -0.3℃, -4.7℃, -9.5℃, -18.7℃, -27.7℃, and -32.6℃, respectively. The Odelevsky model was employed to remove the influence of water in the air on the final effective dielectric constants. The results indicate that frequency and temperature have apparent influences on the dielectric constants of the lunar regolith simulant. The real parts of the dielectric constants increase fast over the range of 0.2 GHz to 3.0 GHz, but decrease slowly over the range of 4.0 GHz to 20.0 GHz. The opposite phenomenon occurs in the imaginary parts. The influences of the frequency and temperature on the brightness temperature were also estimated based on the radiative transfer equation. The result shows that the variation of the frequency and temperature results in great changes of the microwave brightness temperature emitting from the lunar regolith.展开更多
The seasonal cycle of ice thickness and temperature in Lake Wuliangsuhai,a typical shallow lake in the central Asian arid climate zone,was simulated using the HIGHTSI model and the MERRA-2 data as the meteorological f...The seasonal cycle of ice thickness and temperature in Lake Wuliangsuhai,a typical shallow lake in the central Asian arid climate zone,was simulated using the HIGHTSI model and the MERRA-2 data as the meteorological forcing.The average ice growth rate was 0.64 cm·d^(−1) and −1.65 cm·d^(−1) for the growth and melting stage of the ice cover,respectively.The ice thickness agreed well with the field observations conducted in winter 2017,with a correlation coefficient of 0.97.The ice temperature field also agreed with observations in both daily variations and the vertical profile,and a better agreement in the daily amplitude and profile shape of ice temperature could be achieved if field data on physical properties of snow cover andmelting ice were available.This study proved the feasibility of both the HIGHTSI model and the MERRA-2 data for modeling the ice cover evolution in Lake Wuliangsuhai,providing a basis for a deep insight into the difference of lake ice evolution between central Asian arid climate zone and polar/sub-polar regions.展开更多
The third Chinese National Arctic Research Expedition （CHINARE） was conducted in the summer of 2008. During the survey, the surface seawater partial pressure of CO2 （pCO2） was measured, and sea water samples were ...The third Chinese National Arctic Research Expedition （CHINARE） was conducted in the summer of 2008. During the survey, the surface seawater partial pressure of CO2 （pCO2） was measured, and sea water samples were collected for CO2 measurement in the Canada Basin. The distribution of pCO2 in the Canada Basin was determined, the influencing factors were addressed, and the air-sea CO2 flux in the Canada Basin was evaluated. The Canada Basin was divided into three regions： the ice-free zone （south of 77°N）, the partially ice-covered zone （77°-80°N）, and the heavily ice-covered zone （north of 80°N）. In the ice-free zone, pCO2 was high （320 to 368 patm, 1 patm=0.101 325 Pa）, primarily due to rapid equilibration with atmospheric CO2 over a short time. In the partially ice-covered zone, the surface pCOs was relatively low （250 to 270 patm） due to ice-edge blooms and icemelt water dilution. In the heavily ice-covered zone, the seawater pCO2 varied between 270 and 300 laatm due to biological COs removal, the transportation of low pCOs water northward, and heavy ice cover. The surface seawater pCO2 during the survey was undersaturated with respect to the atmosphere in the Canada Basin, and it was a net sink for atmospheric CO2. The summertime net CO2 uptake of the ice-free zone, the partially ice-covered zone and the heavily ice-covered zone was （4.14±1.08）, （1.79±0.19）, and （0.57±0.03） Tg/a （calculated by carbon, 1 Tg=10^12 g）, respectively. Overall, the net COs sink of the Canada Basin in the summer of 2008 was （6.5＋1.3） Tg/a, which accounted for 4%-10% of the Arctic Ocean COs sink.展开更多
For shallow lakes,ice mass balance is largely dominated by thermodynamic processes.The heat flux from lake water plays a critical role for ice growth and melting.In this study,we applied a numerical thermodynamic lake...For shallow lakes,ice mass balance is largely dominated by thermodynamic processes.The heat flux from lake water plays a critical role for ice growth and melting.In this study,we applied a numerical thermodynamic lake model to investigate the sensitivity of the lake ice mass balance to the lake heat flux during the growth and melting periods.Several groups of modelling experiments forced by simplified climatological weather data have been carried out.Two sites,Lake Wuliangsuhai inInner Mongolia,China’s arid region and Lake Orajärvi in snowy Finnish Lapland,were investigated.Lake heat flux affects inversely proportional maximum ice thickness followed by ice break-up date.The solar radiation and surface albedo complicate the effect of lake heat flux on lake ice mass balance during melting season.With heavy snowfall,the increase of lake heat flux adds on the formation of granular ice but reduces the formation of columnar ice.Under climatological weather conditions,theice cover winter seasonal mean lake heat flux were 14 W·m^(−2) and 4 W·m^(−2) in Lake Wuliangsuhai and Lake Orajärvi,respectively.展开更多
In recent years,when planning and determining a travel destination,residents often make the best of Internet techniques to access extensive travel information.Search engines undeniably reveal visitors'real-time pr...In recent years,when planning and determining a travel destination,residents often make the best of Internet techniques to access extensive travel information.Search engines undeniably reveal visitors'real-time preferences when planning to visit a destination.More and more researchers have adopted tourism-related search engine data in the field of tourism prediction.However,few studies use search engine data to conduct cluster analysis to identify residents'choice toward a tourism destination.In the present study,146 keywords related to“Beijing tourism”are obtained from Baidu index and principal component analysis(PCA)is applied to reduce the dimensionality of keywords obtained by Baidu index.Modified affinity propagation(MAP)clustering algorithm is used to classify provinces into several groups to identify the choice of residents to travel to Beijing.The result shows that residents in Hebei province are most likely to travel to Beijing.The cluster result also shows that PCA–MAP performs better than other clustering methods such as K-means,linkage,and Affinity Propogation(AP)in terms of silhouette coefficient and Calinski–Harabaz index.We also distinguish the difference of residents’choice to travel to Beijing during the peak tourist season and off-season.The residents of Tianjing are inclined to travel to Beijing during the peak tourist season.The residents of Guangdong,Hebei,Henan,Jiangsu,Liaoning,Shanghai,Shandong,and Zhejiang have high attention to travel to Beijing during both seasons.展开更多
文摘近年来随着无人机产业的迅猛发展,视觉定位技术已广泛应用于低成本轻量化的定位系统中,然而当无人机在水面等弱纹理区域飞行时,场景视觉特征稀疏且差异小,导致图像误匹配率激增,定位估计发散严重,限制了视觉定位技术在水域环境下的应用。针对该问题提出了一种基于水纹识别的视觉定位技术(visual positioning technique based on water pattern recognition,WPRVP)。首先通过提取水纹多粒度相关特征得到相邻图像之间局部和全局的匹配关系;然后将匹配信息嵌入循环网络迭代处理,由粗到细逐步提高水纹图像的匹配精度;最后基于多视图几何约束进行匹配筛选和运动建模,实现了鲁棒的定位估计。实验结果表明,相比现有的图像匹配和视觉定位方法,WPRVP能够应用于水域环境且能保持更高的匹配与定位精度,能够为导航设备在水域场景下提供一个低成本高精度的导航信息源,辅助无人机执行水面飞行任务。
基金supported by the National Natural Science Foundation of China (No.30600016)the Environment Protection Department of Jiangsu Province,China (No.2004007)
文摘Biofilm-associated microorganisms play crucial roles in terrestrial and aquatic nutrient cycling and in the biodegradation of environmental pollutants. Biofilm formation was determined for a total of 18 bacterial isolates obtained from the biofilms of wastewater treatment systems and of little carpolite in soil. Among these isolates, seven showed strong biofilm-forming capacity. The phylogenetic affiliation of the isolates showing high biofilm formation capacity was determined through 16S rDNA sequencing and the isolates were grouped into 7 bacterial species including Pseudornonas sp., Pseudomonas putida, Aeromonas caviae, Bacillus cereus, Pseudornonas plecoglossicida, Aeromonas hydrophila, and Comamonas testosteroni. The biofilm-forming capacity was closely related with flagella, exopolysaccharide, and extracellular protein. According to the coefficient of determination, the relative importance of the five biological characteristics to biofilm formation was, in order from greatest to least, exopolysaccharide 〉 flagella 〉 N-acyl-homoserine lactones （AHLs） signaling molecules 〉 extracellular protein 〉 swarming motility.
基金supported by Tianjin City High School Science Technology Fund Planning Project(No.2017KJ134)。
文摘Salidroside(SAL)is a phenolic substance with high solubility and low permeability,which make it easy to cause the efflux effect of P-glycoprotein and degradation of intestinal flora,resulting in lower bioavailability.The aim of this study was to develop and optimize a water-in-oil nanoemulsion of SAL(w/o SAL-N)to explore its suitability in oral drug delivery systems.In this work,SAL-N was successfully prepared by water titration method at K_(m)=1 to construct the pseudo-ternary phase diagrams.Physical characterization including the average viscosity,pH,refractive index,particle size,PDI,TEM,DSC,the content of SAL,and stability study were performed.It was evaluated for drug release in vitro and pharmacokinetic studies in vivo.The optimized nanoemulsion formulation consisted of Labrafil M 1944 CS(63%),Span-80/Tween-80/EtOH(27%)and 200 mg·mL^(-1) SAL solution(SAL-SOL)(10%).Low viscosity and suitable pH were expected for the nanoemulsion.The spherical morphology and nanoscale size of SAL-N enhanced the stability of the nanoemulsion system.In vitro drug release showed that SAL-N had a better controlled release property than SAL-SOL at earlier time points.The pharmacokinetic studies exhibited that SAL-N had significantly higher in t_(1/2)(2.11-fold),AUC_(0-48 h)(1.75-fold)and MRT0-48 h(2.63-fold)than SAL-SOL(P<0.01).The w/o SAL-N prepared in this work can be effectively delivered via the oral route.It can be seen w/o nanoemulsion is a strategy for the drug with polyphenols to delay the release,enhance oral absorption and reduce metabolic rate.
基金Project supported by the National Key Technology Research and Development Program of China(No.2006BAD07A01,2006BAD10B05-02).
文摘Furfural is an important inhibitor in ethanol fermentation process using lignocellulosic hydrolysates as raw materials. In order to find out the furfural concentration range in which furfural inhibits the fermentation process, we used one strain Saccharomyces kluyveri selected from soil and cultured in several different furfural content media under low glucose concentration condition. Experiment results showed that microorganism growth was stimulated and dry cell weight decreased when furfural concentration in the medium was 0.25 mg/ml. Furfural had negative effect on cell growth when its concentration was above 1.00 mg/ml. At the same time, the strain growed better and had a higher glucose consumption rate in 5% original glucose concentration condition than in 3% original glucose concentration condition. The results showed that appropriate exaltation of original glucose concentration in stalk hydrolysates will increase the strain resistance to furfural.
基金Under the auspices of National Natural Science Foundation of China (No. 40901159, 40901187)Doctoral Fund of Ministry of Education of China (No. 20090061120055)+1 种基金the Fundamental Research Funds for the Central Universities (No. 200903047)National High Technology Research and Development Program of China (No. 2010AA122203)
文摘The dielectric constant of the lunar regolith can directly influence the reflection coefficient and the trans-mission coefficient of the Moon′s surface, and plays an important role in the Moon research. In order to study the di-electric properties of the lunar regolith, the lunar regolith simulant was made according to the making procedure of the CAS-1 simulant made by Chinese Academy of Sciences. Then the dielectric constants of the lunar regolith simulant were measured with 85070E Aiglent Microwave Network Analyzer in the frequency ranging from 0.2 GHz to 20.0 GHz and at temperature of 25.1℃, 17.7℃, 13.1℃, 11.5℃, 9.6℃, 8.0℃, 4.1℃, -0.3℃, -4.7℃, -9.5℃, -18.7℃, -27.7℃, and -32.6℃, respectively. The Odelevsky model was employed to remove the influence of water in the air on the final effective dielectric constants. The results indicate that frequency and temperature have apparent influences on the dielectric constants of the lunar regolith simulant. The real parts of the dielectric constants increase fast over the range of 0.2 GHz to 3.0 GHz, but decrease slowly over the range of 4.0 GHz to 20.0 GHz. The opposite phenomenon occurs in the imaginary parts. The influences of the frequency and temperature on the brightness temperature were also estimated based on the radiative transfer equation. The result shows that the variation of the frequency and temperature results in great changes of the microwave brightness temperature emitting from the lunar regolith.
基金This research was supported by the National Natural Science Foundation of China(Grant nos.51979024,41876213,41676187)the Open Fund of State Key Laboratory of Frozen Soil Engineering(Grant no.SKLFSE201604)+1 种基金the Fundamental Research Funds for the Central Universities(Grant no.DUT20GJ206)Matti Leppäranta was supported by the Bilateral Exchange Programme of the Chinese Academy of Sciences and Academy of Finland(Grant no.325363).
文摘The seasonal cycle of ice thickness and temperature in Lake Wuliangsuhai,a typical shallow lake in the central Asian arid climate zone,was simulated using the HIGHTSI model and the MERRA-2 data as the meteorological forcing.The average ice growth rate was 0.64 cm·d^(−1) and −1.65 cm·d^(−1) for the growth and melting stage of the ice cover,respectively.The ice thickness agreed well with the field observations conducted in winter 2017,with a correlation coefficient of 0.97.The ice temperature field also agreed with observations in both daily variations and the vertical profile,and a better agreement in the daily amplitude and profile shape of ice temperature could be achieved if field data on physical properties of snow cover andmelting ice were available.This study proved the feasibility of both the HIGHTSI model and the MERRA-2 data for modeling the ice cover evolution in Lake Wuliangsuhai,providing a basis for a deep insight into the difference of lake ice evolution between central Asian arid climate zone and polar/sub-polar regions.
基金The National Natural Science Foundation of China(NSFC) under contract Nos 41476173 and 41406221the Chinese Projects for Investigations and Assessments of the Arctic and Ant Arctic under contract Nos CHINARE2012-04-04 and 2012-04-03+1 种基金the Fujian Science and Technology Innovation Leader Project 2016the Scientific Research Foundation of Third Institute of Oceanography,SOA under contract No.2014006
文摘The third Chinese National Arctic Research Expedition （CHINARE） was conducted in the summer of 2008. During the survey, the surface seawater partial pressure of CO2 （pCO2） was measured, and sea water samples were collected for CO2 measurement in the Canada Basin. The distribution of pCO2 in the Canada Basin was determined, the influencing factors were addressed, and the air-sea CO2 flux in the Canada Basin was evaluated. The Canada Basin was divided into three regions： the ice-free zone （south of 77°N）, the partially ice-covered zone （77°-80°N）, and the heavily ice-covered zone （north of 80°N）. In the ice-free zone, pCO2 was high （320 to 368 patm, 1 patm=0.101 325 Pa）, primarily due to rapid equilibration with atmospheric CO2 over a short time. In the partially ice-covered zone, the surface pCOs was relatively low （250 to 270 patm） due to ice-edge blooms and icemelt water dilution. In the heavily ice-covered zone, the seawater pCO2 varied between 270 and 300 laatm due to biological COs removal, the transportation of low pCOs water northward, and heavy ice cover. The surface seawater pCO2 during the survey was undersaturated with respect to the atmosphere in the Canada Basin, and it was a net sink for atmospheric CO2. The summertime net CO2 uptake of the ice-free zone, the partially ice-covered zone and the heavily ice-covered zone was （4.14±1.08）, （1.79±0.19）, and （0.57±0.03） Tg/a （calculated by carbon, 1 Tg=10^12 g）, respectively. Overall, the net COs sink of the Canada Basin in the summer of 2008 was （6.5＋1.3） Tg/a, which accounted for 4%-10% of the Arctic Ocean COs sink.
基金This research was supported by the Academy of Finland(Grant nos.317999/Cheng333889/Leppäranta)+2 种基金the National Natural Science Foundation of China(Grant nos.51979024,41876213)the Open Fund of State Key Laboratory of Coastal and Offshore Engineering(Grant no.LP2106)the Fundamental Research Funds for the Central Universities(Grant no.DUT20GJ206).
文摘For shallow lakes,ice mass balance is largely dominated by thermodynamic processes.The heat flux from lake water plays a critical role for ice growth and melting.In this study,we applied a numerical thermodynamic lake model to investigate the sensitivity of the lake ice mass balance to the lake heat flux during the growth and melting periods.Several groups of modelling experiments forced by simplified climatological weather data have been carried out.Two sites,Lake Wuliangsuhai inInner Mongolia,China’s arid region and Lake Orajärvi in snowy Finnish Lapland,were investigated.Lake heat flux affects inversely proportional maximum ice thickness followed by ice break-up date.The solar radiation and surface albedo complicate the effect of lake heat flux on lake ice mass balance during melting season.With heavy snowfall,the increase of lake heat flux adds on the formation of granular ice but reduces the formation of columnar ice.Under climatological weather conditions,theice cover winter seasonal mean lake heat flux were 14 W·m^(−2) and 4 W·m^(−2) in Lake Wuliangsuhai and Lake Orajärvi,respectively.
基金Humanities and Social Sciences Foundation of Chinese Ministry of Education,China(No.18YJA630005)National Natural Science Foundation of China(No.71810107003).
文摘In recent years,when planning and determining a travel destination,residents often make the best of Internet techniques to access extensive travel information.Search engines undeniably reveal visitors'real-time preferences when planning to visit a destination.More and more researchers have adopted tourism-related search engine data in the field of tourism prediction.However,few studies use search engine data to conduct cluster analysis to identify residents'choice toward a tourism destination.In the present study,146 keywords related to“Beijing tourism”are obtained from Baidu index and principal component analysis(PCA)is applied to reduce the dimensionality of keywords obtained by Baidu index.Modified affinity propagation(MAP)clustering algorithm is used to classify provinces into several groups to identify the choice of residents to travel to Beijing.The result shows that residents in Hebei province are most likely to travel to Beijing.The cluster result also shows that PCA–MAP performs better than other clustering methods such as K-means,linkage,and Affinity Propogation(AP)in terms of silhouette coefficient and Calinski–Harabaz index.We also distinguish the difference of residents’choice to travel to Beijing during the peak tourist season and off-season.The residents of Tianjing are inclined to travel to Beijing during the peak tourist season.The residents of Guangdong,Hebei,Henan,Jiangsu,Liaoning,Shanghai,Shandong,and Zhejiang have high attention to travel to Beijing during both seasons.
