The grid connection of a large-scale wind farm could change the load flow/configuration of a power system and introduce dynamic interactions with the synchronous generators(SGs),thus affecting system small-signal angu...The grid connection of a large-scale wind farm could change the load flow/configuration of a power system and introduce dynamic interactions with the synchronous generators(SGs),thus affecting system small-signal angular stability.This paper proposes an approach for the separate examination of the impact of those affecting factors,i.e.,the change of load flow/configuration and dynamic interactions brought about by the grid connection of the wind farm,on power system smallsignal angular stability.Both cases of grid connection of the wind farm,either displacing synchronous generators or being directly added into the power system,are considered.By using the proposed approach,how much the effect of the change of load flow/configuration brought about by the wind farm can be examined,while the degree of impact of the dynamic interaction of the wind farm with the SGs can be investigated separately.Thus,a clearer picture and better understanding of the power system small-signal angular stability as affected by grid connection of the large-scale wind farm can be achieved.An example of the power system with grid connection of a wind farm is presented to demonstrate the proposed approach.展开更多
In the traditional strength reduction method,the cohesion and the friction angle adopt the same reduction parameter,resulting in equivalent proportional reduction.This method does not consider the different effects of...In the traditional strength reduction method,the cohesion and the friction angle adopt the same reduction parameter,resulting in equivalent proportional reduction.This method does not consider the different effects of the cohesion and friction angle on the stability of the same slope and is defective to some extent.Regarding this defect,a strength reduction method based on double reduction parameters,which adopts different reduction parameters,is proposed.The core of the double-parameter reduction method is the matching reduction principle of the slope with different angles.This principle is represented by the ratio of the reduction parameter of the cohesion to that of the friction angle,described as η.With the increase in the slopeangle,ηincreases; in particular,when the slope angle is 45°,tηis 1.0.Through the matching reduction principle,different safety margin factors can be calculated for the cohesion and friction angle.In combination with these two safety margin factors,a formula for calculating the overall safety factor of the slope is proposed,reflecting the different contributions of the cohesion and friction angle to the slope stability.Finally,it is shown that the strength reduction method based on double reduction parameters acquires a larger safety factor than the classic limit equilibrium method,but the calculation results are very close to those obtained by the limit equilibrium method.展开更多
Layered double hydroxides（LDHs） as a class of anionic clays have extensive applications due to their unique structures. Nowadays, the emphasis is laid on the development of LDH coatings for corrosion resistance and ...Layered double hydroxides（LDHs） as a class of anionic clays have extensive applications due to their unique structures. Nowadays, the emphasis is laid on the development of LDH coatings for corrosion resistance and medical applications. Thus, this review highlights synthetic methods of LDH coatings and LDH-based composite coatings on magnesium alloys. Special attention is focused on self-healing,biocompatible and self-cleaning LDH-based composite coatings on magnesium alloys.展开更多
The grid-point atmospheric model of IAP LASG （GAMIL） was developed in and has been evaluated since early 2004. Although the model shows its ability in simulating the global climate, it suffers from some problems in ...The grid-point atmospheric model of IAP LASG （GAMIL） was developed in and has been evaluated since early 2004. Although the model shows its ability in simulating the global climate, it suffers from some problems in simulating precipitation in the tropics. These biases seem to result mainly from the treatment of the subgrid scale convection, which is parameterized with Tiedtke＇s massflux scheme （or the Zhang-McFarlane scheme, as an option） in the model. In order to reduce the systematic biases, several modifications were made to the Tiedtke scheme used in GAMIL, including （1） an increase in lateral convective entrainment/detrainment rate for shallow convection, （2） inclusion of a relative humidity threshold for the triggering of deep convection, and （3） a reduced efficiency for the conversion of cloud water to rainwater in the convection scheme. Two experiments, one with the original Tiedtke scheme used in GAMIL and the other with the modified scheme, were conducted to evaluate the performance of the modified scheme in this study. The results show that both the climatological mean state, such as precipitation, temperature and specific humidity, and interannual variability in the model simulation are improved with the use of this modified scheme. Results from several additional experiments show that the improvements in the model performance in different regions mainly result from either the introduction of the relative humidity threshold for triggering of the deep convection or the suppressed shallow convection due to enhanced lateral convective entrainment/detrainment rates.展开更多
[Objective] The aim of this study was to provide the theoretical basis for screening and utilizing salt-tolerant tomato varieties as well as for cultivating salt-resistance.[Method] Salinity tolerance of tomato during...[Objective] The aim of this study was to provide the theoretical basis for screening and utilizing salt-tolerant tomato varieties as well as for cultivating salt-resistance.[Method] Salinity tolerance of tomato during seed germination under simple salt sodium chloride and double salt calcium nitrate or sodium chloride stress were studied by Petri dish culturing.[Result] As the two kinds salt concentration increased,the germination regularity,the germination rate,the germination index and the growing vigor index of tomato seedlings decreased,but the germination losing rate increased.When salt concentration was from 0.2% to 0.4%,there was little difference among all indexes under two kinds of salt stress.However,when salt concentration was from 0.6% to 1.0%,the difference among all indexes under two kinds of salt stress was significant.[Conclusion] Salinity tolerance of tomato seeds under double salt calcium nitrate or sodium chloride stress was higher than that under simple salt sodium chloride stress.展开更多
A new type of double salient starter/generator is presented, which can be used in aircraft Low Voltage Direct Current (LVDC), Variable Speed Constant Frequency (VSCF) and High Voltage Direct Current (HVDC) systems. Th...A new type of double salient starter/generator is presented, which can be used in aircraft Low Voltage Direct Current (LVDC), Variable Speed Constant Frequency (VSCF) and High Voltage Direct Current (HVDC) systems. The operational theory of the motor and generator is analyzed, and corresponding control strategies are given. An 18kW prototype has been implemented to verify the system performance. It is shown that the DSM S/G system possesses simple structure, high efficiency and flexible control. It is ap...展开更多
Capsule endoscopy has revoluzionized the study of the small bowel by providing a reliable method to evaluate, endoscopically, the entire small bowel. In the last six years several papers have been published exploring ...Capsule endoscopy has revoluzionized the study of the small bowel by providing a reliable method to evaluate, endoscopically, the entire small bowel. In the last six years several papers have been published exploring the possible role of this examination in different clinical conditions. At the present time capsule endoscopy is generally recommended as a third examination, after negative bidirectional endoscopy, in patients with obscure gastrointestinal bleeding. A growing body of evidence suggests also an important role for this examination in other clinical conditions such as Crohn＇s disease, celiac disease, small bowel polyposis syndromes or small bowel tumors. The main complication of this examination is the retention of the device at the site of a previously unknown small bowel stricture. However there are also some other open issues mainly due to technical limitations of this tool （which is not driven from remote control, is unable to take biopsies, to insufflate air, to suck fluids or debris and sometimes to correctly size and locate lesions）.The recently developed double balloon enteroscope, owing to its capability to explore a large part of the small bowel and to take targeted biopsies, although being invasive and time consuming, can overcome some limitations of capsule endoscopy. At the present time, in the majority of clinical conditions （i.e. obscure GI bleeding）, the winning strategy seems to be to couple these two techniques to explore the small bowel in a painless, safe and complete way （with capsule endoscopy） and to define and treat the lesions identified （with double balloon enteroscopy）.展开更多
On the basis of a long-term（30 years） field experiment that involved four rotation systems, rice-rice-winter fallow（RRF）, rice-rice-ryegrass（RRG）, rice-rice-rape（RRP）, and rice-rice-milk vetch（RRV）, this stu...On the basis of a long-term（30 years） field experiment that involved four rotation systems, rice-rice-winter fallow（RRF）, rice-rice-ryegrass（RRG）, rice-rice-rape（RRP）, and rice-rice-milk vetch（RRV）, this study described the effects of green manure on the microbial communities in the red paddy soils using 454 pyrosequencing for the 16 S r RNA gene. The Chao1 richness and non-parametric Shannon＇s index increased in all soil samples that received green manure treatments. The communities＇ structures with the green manure applications were significantly dissimilar from that under the winter fallow. Using Metastats tests, many genera in the RRG, RRP and RRV soils were significantly different from those in the RRF soil, including a number of genera that functioned in the nitrogen and sulfur cycles. Analyses of the genera with these functions revealed the shifts in microbial ecosystem functions after long-term green manuring. Changes in the microbial communities increased the ammonium supply and decreased the soil acidification in green-manure-amended soils. Together, these data suggested powerful effects of green manure on both the microbial communities and the biogeochemical cycle driven by the shifts in bacterial functional groups.展开更多
A cost-efficient and stable oxygen evolution electrocatalyst is essential for improving energy storage and conversion efficiencies. Herein, 2D nanosheets with randomly cross-linked CoNi layered double hydroxide （LDH...A cost-efficient and stable oxygen evolution electrocatalyst is essential for improving energy storage and conversion efficiencies. Herein, 2D nanosheets with randomly cross-linked CoNi layered double hydroxide （LDH） and small CoO nanocrystals were designed and synthesized via in situ reduction and interface- directed assembly in air. The formation of CoNi LDH/CoO nanosheets was attributed to the strong extrusion of hydrated metal-oxide clusters driven by the interfacial tension. The obtained loose and porous nanosheets exhibited low crystallinity due to the presence of numerous defects. Owing to the orbital hybridization between metal 3d and O 2p orbitals, and electron transfer between metal atoms through Ni-O-Co, a number of Co and Ni atoms in the CoNi LDH present a high ＋3 valency. These unique characteristics result in a high density of oxygen evolution reaction （OER） active sites, improving the affinity between OH- and catalyst, and resulting in a large accessible surface area and permeable channels for ion adsorption and transport. Therefore, the resulting nanosheets exhibited high catalytic activity towards the OER. The CoNi LDH/CoO featured a low onset potential of 1.48 V in alkaline medium, and required an overpotential of only 300 mV at a current density of 10 mA.cm-2, while displaying good stability in accelerated durability tests.展开更多
提出了一种基于双层Counter Bloom Filter的长流识别算法(algorithm based on double counter bloom filter for long flows identification,简称CCBF).该算法使用两层Counter Bloom Filter结构,将长流过滤和长流存在分开处理.分析了该...提出了一种基于双层Counter Bloom Filter的长流识别算法(algorithm based on double counter bloom filter for long flows identification,简称CCBF).该算法使用两层Counter Bloom Filter结构,将长流过滤和长流存在分开处理.分析了该算法的误判率,通过模拟数据分析了算法错误率和内存资源限制的关系,并在相同内存资源限制的条件下,将该算法与类似算法的准确性进行了比较.结果表明,在数据量较大的情况下,该算法具有比现有算法更小的平均错误率;对算法的时间效率分析表明,该算法可以达到1500kpps的处理速度.各项指标反映出,该算法可以应用于大规模主干网的长流监测.展开更多
AIM:To compare the diagnostic yield of capsule endoscopy (CE) with that of double-balloon enteroscopy (DBE). METHODS:Pubmed,Embase,Elsevier ScienceDirect,the China Academic Journals Full-text Database,and Cochrane Con...AIM:To compare the diagnostic yield of capsule endoscopy (CE) with that of double-balloon enteroscopy (DBE). METHODS:Pubmed,Embase,Elsevier ScienceDirect,the China Academic Journals Full-text Database,and Cochrane Controlled Trials Register were searched for the trials comparing the yield of CE with that of DBE. Outcome measure was odds ratio (OR) of the yield. Fixed or random model method was used for data analysis. RESULTS:Eight studies (n = 277) which prospectively compared the yield of CE and DBE were collected. The results of meta-analysis indicated that there was no difference between the yield of CE and DBE 170/277 vs 156/277,OR 1.21 (95% CI:0.64-2.29). Based on sub analysis,the yield of CE was significantly higher than that of double-balloon enteroscopy without combination of oral and anal insertion approaches 137/219 vs 110/219,OR 1.67 (95% CI:1.14-2.44),P < 0.01),but not superior to the yield of DBE with combination of the two insertion approaches 26/48 vs 37/48,OR 0.33 (95% CI:0.05-2.21),P > 0.05). A focused meta-analysis of the fully published articles concerning obscure GI bleeding was also performed and showed similar results wherein the yield of CE was significantly higher than that of DBE without combination of oral and anal insertion approaches 118/191 vs 96/191,fixed model:OR 1.61 (95% CI:1.07-2.43),P < 0.05) and the yield of CE was significantly lower than that of DBE by oral and anal combinatory approaches 11/24 vs 21/24,fixed model:OR 0.12 (95% CI:0.03-0.52),P < 0.01). CONCLUSION:With combination of oral and anal approaches,the yield of DBE might be at least as high asthat of CE. Decisions made regarding the initial approach should depend on patient's physical status,technology availability,patient's preferences,and potential for therapeutic endoscopy.展开更多
A long-term experiment beginning in 1981 in Jinxian County of Jiangxi Province, subtropical China, was conducted in a paddy field under a double rice cropping system with four different fertilization regimes, includin...A long-term experiment beginning in 1981 in Jinxian County of Jiangxi Province, subtropical China, was conducted in a paddy field under a double rice cropping system with four different fertilization regimes, including 1) no fertilizer as control (CK), 2) balanced chemical N, P, and K fertilizers (NPK), 3) organic manure using milk vetch and pig manure in the early and late rice growing season, respectively (OM), and 4) balanced chemical fertilizers combined with organic manure (NPKM). Samples (0-17 cm) of the paddy field soil, which was derived from Quaternary red clay, were collected after the late rice harvest in November 2003 for determination of total organic carbon (TOC) and total nitrogen (TN) and fractions of organic C and N. Results showed that TOC and TN in the NPKM and OM treatments were significantly higher than those in other two treatments (CK and NPK). Application of organic manure with or without chemical fertilizers significantly increased the contents of all fractions of organic C and N, whereas chemical fertilizer application only increased the contents of occluded particulate organic C (oPOC) and amino acid N. In addition, application of organic manure significantly enhanced the proportions of free particulate organic carbon (fPOC) and oPOC in total C, and those of amino sugar N and amino acid N (P < 0.01) in total N. In contrast, chemical fertilizer application only increased the proportions of oPOC and amino acid N (P < 0.05). There were no significant differences in either contents or proportions of soil organic C and organic N fractions between the NPKM and OM treatments. These indicated that organic manure application with or without chemical fertilizers played the most significant role in enhancing soil organic C and N quantity and quality in the paddy field studied.展开更多
X-rays are widely used in probing inside information nondestructively,enabling broad applications in the medical radiography and electronic industries.X-ray imaging based on emerging lead halide perovskite scintillato...X-rays are widely used in probing inside information nondestructively,enabling broad applications in the medical radiography and electronic industries.X-ray imaging based on emerging lead halide perovskite scintillators has received extensive attention recently.However,the strong self-absorption,relatively low light yield and lead toxicity of these perovskites restrict their practical applications.Here,we report a series of nontoxic double-perovskite scintillators of Cs_(2)Ag_(0.6)Na_(0.4)In_(1-y)Bi_(y)Cl_(6).By controlling the content of the heavy atom Bi^(3+),the X-ray absorption coefficient,radiative emission efficiency,light yield and light decay were manipulated to maximise the scintillator performance.A light yield of up to 39,000±7000 photons/MeV for Cs_(2)Ag_(0.6)Na_(0.4)In_(0.85)Bi_(0.15)Cl_(6) was obtained,which is much higher than that for the previously reported lead halide perovskite colloidal CsPbBr_(3)(21,000 photons/MeV).The large Stokes shift between the radioluminescence(RL)and absorption spectra benefiting from self-trapped excitons(STEs)led to a negligible selfabsorption effect.Given the high light output and fast light decay of this scintillator,static X-ray imaging was attained under an extremely low dose of ∼1μGy_(air),and dynamic X-ray imaging of finger bending without a ghosting effect was demonstrated under a low-dose rate of 47.2μGy_(air) s^(−1).After thermal treatment at 85℃ for 50 h followed by X-ray irradiation for 50 h in ambient air,the scintillator performance in terms of the RL intensity and X-ray image quality remained almost unchanged.Our results shed light on exploring highly competitive scintillators beyond the scope of lead halide perovskites,not only for avoiding toxicity but also for better performance.展开更多
Vehicle suspension design includes a number of compromises to provide good leveling of stability and ride comfort. Optimization of off-road vehicle suspension system is one of the most effective methods, which could c...Vehicle suspension design includes a number of compromises to provide good leveling of stability and ride comfort. Optimization of off-road vehicle suspension system is one of the most effective methods, which could considerably enhance the vehicle stability and controllability. In this work, a comprehensive optimization of an off-read vehicle suspension system model was carried out using software ADAMS. The geometric parameters of suspension system were optimized using genetic algorithm (GA) in a way that ride comfort, handling and stability of vehicle were improved. The results of optimized suspension system and variations of geometric parameters due to road roughness and different steering angles were presented in ADAMS and the results of optimized and conventional suspension systems during various driving maneuvers were compared. The simulation results indicate that the camber angle variations decrease by the optimized suspension system, resulting in improved handling and ride comfort characteristics.展开更多
A study on the production of low phosphorus steel by double slag operation in 210 t converter was carried out. A phosphorus content of less than 0.005% （mass percent） was obtained before tapping. About 80% phosphoru...A study on the production of low phosphorus steel by double slag operation in 210 t converter was carried out. A phosphorus content of less than 0.005% （mass percent） was obtained before tapping. About 80% phosphorus could be removed by the first slag after 5 min. High Fe^3＋ content and high basicity in the first slag were in favor of dephosphorization. On the other hand,Fe3＋ content had less effect on dephosphorization during second slag treatment. In the second slag period,the fraction of dephosphorization increased with the increase of basicity up to a basicity of 6. Further increase of basicity of the second slag had very little effect on dephosphorization. The tapping temperature had great impact on dephosphorization. It was impossible to get phosphorus less that 0.005% when the tapping temperature was higher than 1 943 K. The optimum operation conditions were suggested. On the basis of these conditions,the amount of the second slag and the effect of the remaining first slag were estimated.展开更多
Major pulmonary disorders may occur after brain injuries as ventilator-associated pneumonia, acute respiratory distress syndrome or neurogenic pulmonary edema. They are key points for the management of brain-injured p...Major pulmonary disorders may occur after brain injuries as ventilator-associated pneumonia, acute respiratory distress syndrome or neurogenic pulmonary edema. They are key points for the management of brain-injured patients because respiratory failure and mechanical ventilation seem to be a risk factor for increased mortality, poor neurological outcome and longer intensive care unit or hospital length of stay. Brain and lung strongly interact via complex pathways from the brain to the lung but also from the lung to the brain. Several hypotheses have been proposed with a particular interest for the recently described "double hit" model. Ventilator setting in brain-injured patients with lung injuries has been poorly studied and intensivists are often fearful to use some parts of protective ventilation in patients with brain injury. This review aims to describe the epidemiology and pathophysiology of lung injuries in brain-injured patients, but also the impact of different modalities of mechanical ventilation on the brain in the context of acute brain injury.展开更多
基金supported by the National Basic Research Program of China (973 Program) (2012CB215204)the key project of the SKLAEPS and the international collaborative project jointly funded by the NSFC (51311122) Chinathe EPSRC,UK.
文摘The grid connection of a large-scale wind farm could change the load flow/configuration of a power system and introduce dynamic interactions with the synchronous generators(SGs),thus affecting system small-signal angular stability.This paper proposes an approach for the separate examination of the impact of those affecting factors,i.e.,the change of load flow/configuration and dynamic interactions brought about by the grid connection of the wind farm,on power system smallsignal angular stability.Both cases of grid connection of the wind farm,either displacing synchronous generators or being directly added into the power system,are considered.By using the proposed approach,how much the effect of the change of load flow/configuration brought about by the wind farm can be examined,while the degree of impact of the dynamic interaction of the wind farm with the SGs can be investigated separately.Thus,a clearer picture and better understanding of the power system small-signal angular stability as affected by grid connection of the large-scale wind farm can be achieved.An example of the power system with grid connection of a wind farm is presented to demonstrate the proposed approach.
基金Project(KZCX2-YW-T12)supported by the Chinese Academy of Science,China
文摘In the traditional strength reduction method,the cohesion and the friction angle adopt the same reduction parameter,resulting in equivalent proportional reduction.This method does not consider the different effects of the cohesion and friction angle on the stability of the same slope and is defective to some extent.Regarding this defect,a strength reduction method based on double reduction parameters,which adopts different reduction parameters,is proposed.The core of the double-parameter reduction method is the matching reduction principle of the slope with different angles.This principle is represented by the ratio of the reduction parameter of the cohesion to that of the friction angle,described as η.With the increase in the slopeangle,ηincreases; in particular,when the slope angle is 45°,tηis 1.0.Through the matching reduction principle,different safety margin factors can be calculated for the cohesion and friction angle.In combination with these two safety margin factors,a formula for calculating the overall safety factor of the slope is proposed,reflecting the different contributions of the cohesion and friction angle to the slope stability.Finally,it is shown that the strength reduction method based on double reduction parameters acquires a larger safety factor than the classic limit equilibrium method,but the calculation results are very close to those obtained by the limit equilibrium method.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51601108, 51571134)the Natural Science Foundation of Shandong Province (Grant No. 2016ZRB01A62)the SDUST Research Fund (No. 2014TDJH104) and the Ministry-province jointly-constructed cultivation base for state key laboratory of Processing for non-ferrous metal and featured materials, "Guangxi Zhuang Autonomous Region"
文摘Layered double hydroxides（LDHs） as a class of anionic clays have extensive applications due to their unique structures. Nowadays, the emphasis is laid on the development of LDH coatings for corrosion resistance and medical applications. Thus, this review highlights synthetic methods of LDH coatings and LDH-based composite coatings on magnesium alloys. Special attention is focused on self-healing,biocompatible and self-cleaning LDH-based composite coatings on magnesium alloys.
基金This work is jointly supported by CAS International Partnership Creative Group ＂The Climate System Model Development and Application Studies＂, the 973 Project （Grant No. 2005CB321703） the Fund for Innovative Research Groups （Grant No. 40221503） the National Natural Science Foundation of China （Grant No. 40233031）.
文摘The grid-point atmospheric model of IAP LASG （GAMIL） was developed in and has been evaluated since early 2004. Although the model shows its ability in simulating the global climate, it suffers from some problems in simulating precipitation in the tropics. These biases seem to result mainly from the treatment of the subgrid scale convection, which is parameterized with Tiedtke＇s massflux scheme （or the Zhang-McFarlane scheme, as an option） in the model. In order to reduce the systematic biases, several modifications were made to the Tiedtke scheme used in GAMIL, including （1） an increase in lateral convective entrainment/detrainment rate for shallow convection, （2） inclusion of a relative humidity threshold for the triggering of deep convection, and （3） a reduced efficiency for the conversion of cloud water to rainwater in the convection scheme. Two experiments, one with the original Tiedtke scheme used in GAMIL and the other with the modified scheme, were conducted to evaluate the performance of the modified scheme in this study. The results show that both the climatological mean state, such as precipitation, temperature and specific humidity, and interannual variability in the model simulation are improved with the use of this modified scheme. Results from several additional experiments show that the improvements in the model performance in different regions mainly result from either the introduction of the relative humidity threshold for triggering of the deep convection or the suppressed shallow convection due to enhanced lateral convective entrainment/detrainment rates.
基金Supported by the International Science and Technology Cooperation Program(2008DFA31820)~~
文摘[Objective] The aim of this study was to provide the theoretical basis for screening and utilizing salt-tolerant tomato varieties as well as for cultivating salt-resistance.[Method] Salinity tolerance of tomato during seed germination under simple salt sodium chloride and double salt calcium nitrate or sodium chloride stress were studied by Petri dish culturing.[Result] As the two kinds salt concentration increased,the germination regularity,the germination rate,the germination index and the growing vigor index of tomato seedlings decreased,but the germination losing rate increased.When salt concentration was from 0.2% to 0.4%,there was little difference among all indexes under two kinds of salt stress.However,when salt concentration was from 0.6% to 1.0%,the difference among all indexes under two kinds of salt stress was significant.[Conclusion] Salinity tolerance of tomato seeds under double salt calcium nitrate or sodium chloride stress was higher than that under simple salt sodium chloride stress.
文摘A new type of double salient starter/generator is presented, which can be used in aircraft Low Voltage Direct Current (LVDC), Variable Speed Constant Frequency (VSCF) and High Voltage Direct Current (HVDC) systems. The operational theory of the motor and generator is analyzed, and corresponding control strategies are given. An 18kW prototype has been implemented to verify the system performance. It is shown that the DSM S/G system possesses simple structure, high efficiency and flexible control. It is ap...
文摘Capsule endoscopy has revoluzionized the study of the small bowel by providing a reliable method to evaluate, endoscopically, the entire small bowel. In the last six years several papers have been published exploring the possible role of this examination in different clinical conditions. At the present time capsule endoscopy is generally recommended as a third examination, after negative bidirectional endoscopy, in patients with obscure gastrointestinal bleeding. A growing body of evidence suggests also an important role for this examination in other clinical conditions such as Crohn＇s disease, celiac disease, small bowel polyposis syndromes or small bowel tumors. The main complication of this examination is the retention of the device at the site of a previously unknown small bowel stricture. However there are also some other open issues mainly due to technical limitations of this tool （which is not driven from remote control, is unable to take biopsies, to insufflate air, to suck fluids or debris and sometimes to correctly size and locate lesions）.The recently developed double balloon enteroscope, owing to its capability to explore a large part of the small bowel and to take targeted biopsies, although being invasive and time consuming, can overcome some limitations of capsule endoscopy. At the present time, in the majority of clinical conditions （i.e. obscure GI bleeding）, the winning strategy seems to be to couple these two techniques to explore the small bowel in a painless, safe and complete way （with capsule endoscopy） and to define and treat the lesions identified （with double balloon enteroscopy）.
基金supported by the Special Fund for Agro-scientific Research in the Public Interest of China(201103005)the Science and Technology Innovation Project of Chinese Academy of Agricultural Sciences(2013–2017)
文摘On the basis of a long-term（30 years） field experiment that involved four rotation systems, rice-rice-winter fallow（RRF）, rice-rice-ryegrass（RRG）, rice-rice-rape（RRP）, and rice-rice-milk vetch（RRV）, this study described the effects of green manure on the microbial communities in the red paddy soils using 454 pyrosequencing for the 16 S r RNA gene. The Chao1 richness and non-parametric Shannon＇s index increased in all soil samples that received green manure treatments. The communities＇ structures with the green manure applications were significantly dissimilar from that under the winter fallow. Using Metastats tests, many genera in the RRG, RRP and RRV soils were significantly different from those in the RRF soil, including a number of genera that functioned in the nitrogen and sulfur cycles. Analyses of the genera with these functions revealed the shifts in microbial ecosystem functions after long-term green manuring. Changes in the microbial communities increased the ammonium supply and decreased the soil acidification in green-manure-amended soils. Together, these data suggested powerful effects of green manure on both the microbial communities and the biogeochemical cycle driven by the shifts in bacterial functional groups.
基金We gratefully acknowledge the support of this research by the Key Program Projects of the National Natural Science Foundation of China （No. 21031001）, the National Natural Science Foundation of China （Nos. 21371053 and 21573062）, the Cultivation Fund of the Key Scientific and Technical Innovation Project, Program for Innovative Research Team in University （No. IRT-1237）, Application Technology Research and Development Projects in Harbin （No. 2013AE4BW051）, International Science ＆ Technology Cooperation Program of China （No. 2014DFR41110）, and the Foundation of Heilongjiang Province of China （No. QC2013C009）.
文摘A cost-efficient and stable oxygen evolution electrocatalyst is essential for improving energy storage and conversion efficiencies. Herein, 2D nanosheets with randomly cross-linked CoNi layered double hydroxide （LDH） and small CoO nanocrystals were designed and synthesized via in situ reduction and interface- directed assembly in air. The formation of CoNi LDH/CoO nanosheets was attributed to the strong extrusion of hydrated metal-oxide clusters driven by the interfacial tension. The obtained loose and porous nanosheets exhibited low crystallinity due to the presence of numerous defects. Owing to the orbital hybridization between metal 3d and O 2p orbitals, and electron transfer between metal atoms through Ni-O-Co, a number of Co and Ni atoms in the CoNi LDH present a high ＋3 valency. These unique characteristics result in a high density of oxygen evolution reaction （OER） active sites, improving the affinity between OH- and catalyst, and resulting in a large accessible surface area and permeable channels for ion adsorption and transport. Therefore, the resulting nanosheets exhibited high catalytic activity towards the OER. The CoNi LDH/CoO featured a low onset potential of 1.48 V in alkaline medium, and required an overpotential of only 300 mV at a current density of 10 mA.cm-2, while displaying good stability in accelerated durability tests.
文摘提出了一种基于双层Counter Bloom Filter的长流识别算法(algorithm based on double counter bloom filter for long flows identification,简称CCBF).该算法使用两层Counter Bloom Filter结构,将长流过滤和长流存在分开处理.分析了该算法的误判率,通过模拟数据分析了算法错误率和内存资源限制的关系,并在相同内存资源限制的条件下,将该算法与类似算法的准确性进行了比较.结果表明,在数据量较大的情况下,该算法具有比现有算法更小的平均错误率;对算法的时间效率分析表明,该算法可以达到1500kpps的处理速度.各项指标反映出,该算法可以应用于大规模主干网的长流监测.
文摘AIM:To compare the diagnostic yield of capsule endoscopy (CE) with that of double-balloon enteroscopy (DBE). METHODS:Pubmed,Embase,Elsevier ScienceDirect,the China Academic Journals Full-text Database,and Cochrane Controlled Trials Register were searched for the trials comparing the yield of CE with that of DBE. Outcome measure was odds ratio (OR) of the yield. Fixed or random model method was used for data analysis. RESULTS:Eight studies (n = 277) which prospectively compared the yield of CE and DBE were collected. The results of meta-analysis indicated that there was no difference between the yield of CE and DBE 170/277 vs 156/277,OR 1.21 (95% CI:0.64-2.29). Based on sub analysis,the yield of CE was significantly higher than that of double-balloon enteroscopy without combination of oral and anal insertion approaches 137/219 vs 110/219,OR 1.67 (95% CI:1.14-2.44),P < 0.01),but not superior to the yield of DBE with combination of the two insertion approaches 26/48 vs 37/48,OR 0.33 (95% CI:0.05-2.21),P > 0.05). A focused meta-analysis of the fully published articles concerning obscure GI bleeding was also performed and showed similar results wherein the yield of CE was significantly higher than that of DBE without combination of oral and anal insertion approaches 118/191 vs 96/191,fixed model:OR 1.61 (95% CI:1.07-2.43),P < 0.05) and the yield of CE was significantly lower than that of DBE by oral and anal combinatory approaches 11/24 vs 21/24,fixed model:OR 0.12 (95% CI:0.03-0.52),P < 0.01). CONCLUSION:With combination of oral and anal approaches,the yield of DBE might be at least as high asthat of CE. Decisions made regarding the initial approach should depend on patient's physical status,technology availability,patient's preferences,and potential for therapeutic endoscopy.
基金Project supported by the National Natural Science Foundation of China (No. 30571094)the New Century Excellent Talents in University of China (No. NCET-05-0492)the Eleventh Five-Year Plan of China (Nos. 2006BAD15B02 and 2006BAD02A15)
文摘A long-term experiment beginning in 1981 in Jinxian County of Jiangxi Province, subtropical China, was conducted in a paddy field under a double rice cropping system with four different fertilization regimes, including 1) no fertilizer as control (CK), 2) balanced chemical N, P, and K fertilizers (NPK), 3) organic manure using milk vetch and pig manure in the early and late rice growing season, respectively (OM), and 4) balanced chemical fertilizers combined with organic manure (NPKM). Samples (0-17 cm) of the paddy field soil, which was derived from Quaternary red clay, were collected after the late rice harvest in November 2003 for determination of total organic carbon (TOC) and total nitrogen (TN) and fractions of organic C and N. Results showed that TOC and TN in the NPKM and OM treatments were significantly higher than those in other two treatments (CK and NPK). Application of organic manure with or without chemical fertilizers significantly increased the contents of all fractions of organic C and N, whereas chemical fertilizer application only increased the contents of occluded particulate organic C (oPOC) and amino acid N. In addition, application of organic manure significantly enhanced the proportions of free particulate organic carbon (fPOC) and oPOC in total C, and those of amino sugar N and amino acid N (P < 0.01) in total N. In contrast, chemical fertilizer application only increased the proportions of oPOC and amino acid N (P < 0.05). There were no significant differences in either contents or proportions of soil organic C and organic N fractions between the NPKM and OM treatments. These indicated that organic manure application with or without chemical fertilizers played the most significant role in enhancing soil organic C and N quantity and quality in the paddy field studied.
基金the support from the National Key Research and Development Program of China(2017YFA0207700)Outstanding Youth Fund of Zhejiang Natural Science Foundation of China(LR18F050001)National Natural Science Foundation of China(61804134,61525106,U1809204).
文摘X-rays are widely used in probing inside information nondestructively,enabling broad applications in the medical radiography and electronic industries.X-ray imaging based on emerging lead halide perovskite scintillators has received extensive attention recently.However,the strong self-absorption,relatively low light yield and lead toxicity of these perovskites restrict their practical applications.Here,we report a series of nontoxic double-perovskite scintillators of Cs_(2)Ag_(0.6)Na_(0.4)In_(1-y)Bi_(y)Cl_(6).By controlling the content of the heavy atom Bi^(3+),the X-ray absorption coefficient,radiative emission efficiency,light yield and light decay were manipulated to maximise the scintillator performance.A light yield of up to 39,000±7000 photons/MeV for Cs_(2)Ag_(0.6)Na_(0.4)In_(0.85)Bi_(0.15)Cl_(6) was obtained,which is much higher than that for the previously reported lead halide perovskite colloidal CsPbBr_(3)(21,000 photons/MeV).The large Stokes shift between the radioluminescence(RL)and absorption spectra benefiting from self-trapped excitons(STEs)led to a negligible selfabsorption effect.Given the high light output and fast light decay of this scintillator,static X-ray imaging was attained under an extremely low dose of ∼1μGy_(air),and dynamic X-ray imaging of finger bending without a ghosting effect was demonstrated under a low-dose rate of 47.2μGy_(air) s^(−1).After thermal treatment at 85℃ for 50 h followed by X-ray irradiation for 50 h in ambient air,the scintillator performance in terms of the RL intensity and X-ray image quality remained almost unchanged.Our results shed light on exploring highly competitive scintillators beyond the scope of lead halide perovskites,not only for avoiding toxicity but also for better performance.
文摘Vehicle suspension design includes a number of compromises to provide good leveling of stability and ride comfort. Optimization of off-road vehicle suspension system is one of the most effective methods, which could considerably enhance the vehicle stability and controllability. In this work, a comprehensive optimization of an off-read vehicle suspension system model was carried out using software ADAMS. The geometric parameters of suspension system were optimized using genetic algorithm (GA) in a way that ride comfort, handling and stability of vehicle were improved. The results of optimized suspension system and variations of geometric parameters due to road roughness and different steering angles were presented in ADAMS and the results of optimized and conventional suspension systems during various driving maneuvers were compared. The simulation results indicate that the camber angle variations decrease by the optimized suspension system, resulting in improved handling and ride comfort characteristics.
文摘A study on the production of low phosphorus steel by double slag operation in 210 t converter was carried out. A phosphorus content of less than 0.005% （mass percent） was obtained before tapping. About 80% phosphorus could be removed by the first slag after 5 min. High Fe^3＋ content and high basicity in the first slag were in favor of dephosphorization. On the other hand,Fe3＋ content had less effect on dephosphorization during second slag treatment. In the second slag period,the fraction of dephosphorization increased with the increase of basicity up to a basicity of 6. Further increase of basicity of the second slag had very little effect on dephosphorization. The tapping temperature had great impact on dephosphorization. It was impossible to get phosphorus less that 0.005% when the tapping temperature was higher than 1 943 K. The optimum operation conditions were suggested. On the basis of these conditions,the amount of the second slag and the effect of the remaining first slag were estimated.
文摘Major pulmonary disorders may occur after brain injuries as ventilator-associated pneumonia, acute respiratory distress syndrome or neurogenic pulmonary edema. They are key points for the management of brain-injured patients because respiratory failure and mechanical ventilation seem to be a risk factor for increased mortality, poor neurological outcome and longer intensive care unit or hospital length of stay. Brain and lung strongly interact via complex pathways from the brain to the lung but also from the lung to the brain. Several hypotheses have been proposed with a particular interest for the recently described "double hit" model. Ventilator setting in brain-injured patients with lung injuries has been poorly studied and intensivists are often fearful to use some parts of protective ventilation in patients with brain injury. This review aims to describe the epidemiology and pathophysiology of lung injuries in brain-injured patients, but also the impact of different modalities of mechanical ventilation on the brain in the context of acute brain injury.
