We have established a set of laboratory measurements which is used for capturing element gammma spectrum. Standard captured gamma ray spectra for ten elements, including Si, Ca, Fe, are obtained using the measurements...We have established a set of laboratory measurements which is used for capturing element gammma spectrum. Standard captured gamma ray spectra for ten elements, including Si, Ca, Fe, are obtained using the measurements for the first time in China. We also simulated the capture gamma ray spectra of the ten elements using Monte Carlo methodology with the same parameters of our experimental measurements. Comparing the experiment and simulation results with the data from the International Atomic Energy Agency's Nuclear Data Center, we obtained the standard captured gamma ray spectra of the ten elements, which, as calibration spectra, are used to calibrate the raw spectrum in data processing. This method solved the key problem during the conversion from the original measuring spectrum to the yield of each element in the data processing. The method can effectively improve the accuracy of the element yield calculation.展开更多
Taking variability and uncertainty involved in performance prediction into account, in order to make the prediction reliable and meaningful, a distribution-based method is developed to predict future PSI. This method,...Taking variability and uncertainty involved in performance prediction into account, in order to make the prediction reliable and meaningful, a distribution-based method is developed to predict future PSI. This method, which is based on the AASHTO pavement performance model, treats predictor variables as random variables with certain probability distributions and obtains the distribution of future PSI through the method of Monte-Carlo simulation. A computer program PERFORM using Monte Carlo simulation is developed to implement the numerical computation. Simulation results based on pavement and traffic parameters show that traffic, surface layer material property, and initial pavement performance are the most significant factors affecting pavement performance. Once the distribution of future PSI is determined, statistics such as the mean and the variance of future PSI are readily available.展开更多
AIM: To evaluate the efficiency and safety of combined recombinant human growth hormone (rhGH) and lactulose for treatment and/or prevention of multiple organ dysfunction in patients with chronic severe hepatitis B. M...AIM: To evaluate the efficiency and safety of combined recombinant human growth hormone (rhGH) and lactulose for treatment and/or prevention of multiple organ dysfunction in patients with chronic severe hepatitis B. METHODS: Forty-eight inpatients with chronic severe hepatitis B were randomly divided into rhGH group (n = 28)and control group (n = 20). In rhGH group, 4-4.5 IU of rhGH was injected intramuscularly once daily for 2-4 wk,and 100 mL of enema containing 30 mL of lactulose, 2 g of metronidazole and 0.9% saline was administered every 2 d for 2-4 wk. Their symptoms and complications were noted. Liver and kidney functions were analyzed by an Olympus analyzer. Serum GH, IGF-1, IGFBP1 and IGFBP3 were measured by ELISA.RESULTS: Clinical symptoms of 90% of these patients in rhGH group were obviously improved. The total effectiveness in rhGH group was better than that in control group (75% vs40%, P<0.05). After 2- and 4-wk treatment of rhGH respectively, serum albumin (26.1±4.1 vs 30.2±5.3,31.9±5.1 g/L), prealbumin (79.6±28.0 vs 106.6±54.4,108.4±55.0 g/L), cholesterol (76.3±16.7 vs 85.6±32.3,96.1±38.7 mg/dL), and IGFBP1 (56.8±47.2 vs 89.7±50.3ng/mL after 2 wk) were significantly increased compared to control group (P<0.05). However, serum GH was decreased. The increase of serum IGF1 and IGFBP3 after rhGH treatment was also observed.CONCLUSION: rhGH in combination with lactulose may be beneficial to the prevention and treatment of multiple organ dysfunction in patients with chronic severe hepatitis.展开更多
Influenced by strong winds associated with a southeastward-moving Mongolian cyclone,a severe transmission line galloping occurred in Baiyin City,Gansu Province,on 14 April 2020.This caused a tripping incident of the t...Influenced by strong winds associated with a southeastward-moving Mongolian cyclone,a severe transmission line galloping occurred in Baiyin City,Gansu Province,on 14 April 2020.This caused a tripping incident of the transmission line in this region.Based on the hourly,0.5°×0.5°,ECMWF ERA5 reanalysis data,this study investigated the formation mechanisms of the Mongolian cyclone and its associated strong winds.Results from the vorticity budget indicate that the convergence-related vertical stretching and the upward transport of cyclonic vorticity governed formation of the Mongolian cyclone in this event;whereas,tilting and export of cyclonic vorticity from the central region of the cyclone mainly decelerated the cyclone’s formation.The kinetic energy(KE)budget shows that the wind associated with the Mongolian cyclone was mainly enhanced by the positive work of the pressure gradient force.Unlike some typical strong wind events in Northwest China,during this event,no significant downward momentum transportation from the upper troposphere was found.The vertical transport of KE exerted a slightly favorable effect on the KE increase around the location where the transmission line galloping trip appeared.In contrast,the horizontal transport mainly caused an export of KE from this region,which applied an overall negative effect on the wind enhancement associated with the Mongolian cyclone.展开更多
Energy conservation in Wireless Sensor Networks (WSNs) has always been a crucial issue and has received increased attention in the recent years. A transmission scheme for energy-constrained WSNs is proposed in this pa...Energy conservation in Wireless Sensor Networks (WSNs) has always been a crucial issue and has received increased attention in the recent years. A transmission scheme for energy-constrained WSNs is proposed in this paper. The scheme, called MIHOP (MIMO and Multi-hop), combines cluster-based virtual MIMO and multi-hop technologies. The multihop mode is employed in transmitting data when the related sensors are located within a specific number of hops from the sink, and the virtual MIMO mode is used in transmitting data from the remaining sensor nodes. We compare the energy consumption of different transmission schemes and propose an algorithm for determining the optimal hop count in MIHOP. A controllable mobile sink that reduces the energy consumed in sensor transmission is also adopted for data collection. The theoretical analysis and the Monte Carlo simulation demonstrate that the proposed scheme significantly outperforms individual virtual MIMO, multi-hop technologies, and double-string networks in terms of energy conservation. The energy consumption levels under the MIHOP scheme are approximately 12.98%, 47.55% and 48.30% less than that under virtual MIMO schemes, multi-hop networks and doublestring networks, respectively.展开更多
On basis of bond dissociation energies (BDEs) for BH2, B(OH)2, BCl2, and BCl, the diffusion Monte Carlo (DMC) method is applied to explore the BDEs of HB-H, HOB-OH, ClB-Cl, and B-Cl. The effect of the choice of ...On basis of bond dissociation energies (BDEs) for BH2, B(OH)2, BCl2, and BCl, the diffusion Monte Carlo (DMC) method is applied to explore the BDEs of HB-H, HOB-OH, ClB-Cl, and B-Cl. The effect of the choice of orbitals, as well as the backflow transformation, is studied. The Slater-Jastrow DMC algorithm gives BDEs of 359.1±0.12 kJ/mol for HB-H, 410.5±0.50 kJ/mol for HOB-OH, 357.8±1.46 kJ/mol for ClB-Cl, and 504.5±0.96 kJ/mol for B-Cl using B3PW91 orbitals and similar BDEs when B3LYP orbitals are used. DMC with backflow corrections (BF-DMC) gives a HB-H BDE of 369.9±0.12 kJ/mol which is close to one of the available experimental value (375.8 kJ/mol). In the case of HOB-OH BDE, the BF-DMC calculation is 446.04-1.84 k J/mol that is closer to the experimental BDE. The BF-DMC BDE for ClB-Cl is 343.2±2.34 kJ/mol and the BF-DMC B-Cl BDE is 523.3±0.33 kJ/mol, which are close to the experimental BDEs, 341.9 and 530.0 kJ/mol, respectively.展开更多
In this work grand canonical Monte Carlo simulations were performed to study gas separation in three pairs of isoreticular metal-organic frameworks (IRMOFs) with and without catenation at room temperature.Mixture comp...In this work grand canonical Monte Carlo simulations were performed to study gas separation in three pairs of isoreticular metal-organic frameworks (IRMOFs) with and without catenation at room temperature.Mixture composed of CO2 and H2 was selected as the model system to separate.The results show that CO2 selectivity in catenated MOFs with multi-porous frameworks is much higher than their non-catenated counterparts.The simulations also show that the electrostatic interactions are very important for the selectivity,and the contributions of different electrostatic interactions are different,depending on pore size,pressure and mixture composition.In fact,changing the electrostatic interactions can even qualitatively change the adsorption behavior.A general conclusion is that the electrostatic interactions between adsorbate molecules and the framework atoms play a dominant role at low pressures,and these interactions in catenated MOFs have much more pronounced effects than those in their non-catenated counterparts,while the electrostatic interactions between adsorbate molecules become evident with increasing pressure,and eventually dominant.展开更多
The effects of the cell parameter and chemical composition on the surface charge properties of five kinds of different colour montmorillonites were studied. The results indicate that the surface isoelectric point(IEP...The effects of the cell parameter and chemical composition on the surface charge properties of five kinds of different colour montmorillonites were studied. The results indicate that the surface isoelectric point(IEP) of the montmorillonite shows positive correlation with the mass fractions of Fe203 and K20, but it has little relation to the mass fractions of other chemical compositions. At around pH=6.8, the surface zeta potential of the montmorillonite shows the negative relationship with the mass fractions of Fe203 and MgO, but it does not linearly correlate to the mass fractions of other chemical compositions. Cell parameter(bo) of the montmorillonite expresses negative linear relationship with mass fractions of K2O and Na2O, so does cosinβ with mass fractions of SlOE and Fe2O3. And there is no specific relationship between bo and IEP of different montmorillonites, but there is positive correlation between cosinβ and IEP of different montmorillonite samples.展开更多
In this paper,we proposed a framework for evaluating the performance of ecosystem strategies prepared for enhancing vulnerability reduction in the face of hazards due to climate change.The framework highlights the pos...In this paper,we proposed a framework for evaluating the performance of ecosystem strategies prepared for enhancing vulnerability reduction in the face of hazards due to climate change.The framework highlights the positive effects of human activities in the coupled human and natural system(CHANS) by introducing adaptive capacity as an evaluation criterion.A built-in regional vulnerability to a certain hazard was generated based upon interaction of three dimensions of vulnerability:exposure,sensitivity and adaptive capacity.We illustrated the application of this framework in the temperate farming-grazing transitional zone in the middle Inner Mongolia of the northern China,where drought hazard is the key threat to the CHANS.Specific indices were produced to translate such climate variance and social-economic differences into specific indicators.The results showed that the most exposed regions are the inner land areas,while counties located in the eastern part are potentially the most adaptive ones.Ordos City and Bayannur City are most frequently influenced by multiple climate variances,showing highest sensitivity.Analysis also indicated that differences in the ability to adapt to changes are the main causes of spatial differences.After depiction of the spatial differentiations and analysis of the reasons,climate zones were divided to depict the differences in facing to the drought threats.The climate zones were shown to be similar to vulnerability zones based on the quantitative structure of indexes drafted by a triangular map.Further analysis of the composition of the vulnerability index showed that the evaluation criteria were effective in validating the spatial differentiation but potentially ineffective because of their limited time scope.This research will be a demonstration of how to combine the three dimensions by quantitative methods and will thus provide a guide for government to vulnerability reduction management.展开更多
In this paper,organic montmorillonite(OMMT)was added into crumb rubber modified asphalt(CRMA)to improve its high temperature performance,anti-aging performance and storage stability.The effects of different OMMT conte...In this paper,organic montmorillonite(OMMT)was added into crumb rubber modified asphalt(CRMA)to improve its high temperature performance,anti-aging performance and storage stability.The effects of different OMMT content on properties of CRMA were studied.The rutting factor obtained by dynamic shear rheological(DSR)test was adopted to evaluate the high-temperature performance.The creep stiffness and m value determined by the bending beam rheometer(BBR)test were employed to evaluate the low-temperature performance.The softening point,ductility,rutting factor before and after rolling thin film ovens test(RTFOT)and pressure aging vessel test(PAV)were compared to characterize the aging properties.Moreover,the segregation test after being reserved for 48 h and 7 d was conducted,and the softening point and rutting factor of upper and lower layers of segregation pipe were adopted to evaluate the storage stability.The results indicated that the high-temperature performance and anti-aging performance were developed with the increasing content of OMMT,while the low-temperature performance deteriorated.The storage stability was improved with the increasing content of OMMT before the content exceeded 4%,after which the storage stability declined.Taking account of all factors,it is suggested that the optimum content of OMMT is 3%−4%.展开更多
Precipitation is the major driver of ecosystem functions and processes in semiarid and arid regions. In such waterlimited ecosystems, pulsed water inputs directly control the belowground processes through a series of ...Precipitation is the major driver of ecosystem functions and processes in semiarid and arid regions. In such waterlimited ecosystems, pulsed water inputs directly control the belowground processes through a series of soil drying and rewetting cycles. To investigate the effects of sporadic addition of water on soil CO2 effux, an artificial precipitation event (3 mm) was applied to a desert shrub ecosystem in the Mu Us Sand Land of the Ordos Plateau in China. Soil respiration rate increased 2.8 4.1 times immediately after adding water in the field, and then it returned to background level within 48 h. During the experiment, soil CO2 production was between 2 047.0 and 7 383.0 mg m^-2. In the shrubland, soil respiration responses showed spatial variations, having stronger pulse effects beneath the shrubs than in the interplant spaces. The spatial variation of the soil respiration responses was closely related with the heterogeneity of soil substrate availability. Apart from precipitation, soil organic carbon and total nitrogen pool were also identified as determinants of soil CO2 loss in desert ecosystems.展开更多
In this paper, a sensing model for the coverage analysis of wireless sensor networks is provided. Using this model and Monte Carlo method, the ratio of private range to sensing range required to obtain the desired cov...In this paper, a sensing model for the coverage analysis of wireless sensor networks is provided. Using this model and Monte Carlo method, the ratio of private range to sensing range required to obtain the desired coverage can be derived considering the scale of deployment area and the number of sensor nodes. Base on the coverage analysis, an energy-efficient distributed node scheduling scheme is proposed to prolong the network lifetime while maintaining the desired sensing coverage, which does not need the geographic or neighbor information of nodes. The proposed scheme can also handle uneven distribution, and it is robust against node failures. Theoretical and simulation results demonstrate its efficiency and usefulness.展开更多
Western heuristic teaching method was originated from Socrates who initiated the teaching mode of "teachers ask, students answer". A distinctive feature of this mode was that teachers were the decisive factor in the...Western heuristic teaching method was originated from Socrates who initiated the teaching mode of "teachers ask, students answer". A distinctive feature of this mode was that teachers were the decisive factor in the process of teaching and learning, who raised the questions at the very beginning and gave conclusions in the end. On the contrary, oriental style of heuristic teaching method based itself on the principle that students put forward their puzzles and then asked the teachers for advice. This paper will reconsider Confucius enlightening reflection and probe into how to develop students' ability of thinking by questioning strategies in the heuristic teaching methodology.展开更多
To investigate the impact of antenna correlation on secrecy performance in MIMO wiretap channels with Nakagami-m fading, the expressions of secrecy outage probability and positive secrecy probability were derived. Div...To investigate the impact of antenna correlation on secrecy performance in MIMO wiretap channels with Nakagami-m fading, the expressions of secrecy outage probability and positive secrecy probability were derived. Diversity order and array gain were also achieved for further insight. The study was based on the information theory that physical layer security can be guaranteed when the quality of the main channel is higher than that of the eavesdropper's channel. Monte Carlo simulations well validated the numerical results of analytic expressions. It was shown that antenna correlation is detrimental to secrecy performance when average SNR of the main channel is at medium and high level. Interestingly, when average SNR of the main channel reduces to low level, the effect of antenna correlation becomes benefi cial to secrecy performance.展开更多
基金sponsored by the National S&T Major Special Project(No. 2011ZX05020-008)
文摘We have established a set of laboratory measurements which is used for capturing element gammma spectrum. Standard captured gamma ray spectra for ten elements, including Si, Ca, Fe, are obtained using the measurements for the first time in China. We also simulated the capture gamma ray spectra of the ten elements using Monte Carlo methodology with the same parameters of our experimental measurements. Comparing the experiment and simulation results with the data from the International Atomic Energy Agency's Nuclear Data Center, we obtained the standard captured gamma ray spectra of the ten elements, which, as calibration spectra, are used to calibrate the raw spectrum in data processing. This method solved the key problem during the conversion from the original measuring spectrum to the yield of each element in the data processing. The method can effectively improve the accuracy of the element yield calculation.
基金The US National Science Foundation (No. CMMI-0408390,CMMI-0644552)the American Chemical Society Petroleum Research Foundation(No. PRF-44468-G9 )+2 种基金Chang Jiang Scholars Program,the Fok Ying-Tong Education Foundation (No. 114024 )the Natural Science Foundation of Jiangsu Province(No. SBK200910046 )the Postdoctoral Science Foundation of Jiangsu Province (No.0901005C)
文摘Taking variability and uncertainty involved in performance prediction into account, in order to make the prediction reliable and meaningful, a distribution-based method is developed to predict future PSI. This method, which is based on the AASHTO pavement performance model, treats predictor variables as random variables with certain probability distributions and obtains the distribution of future PSI through the method of Monte-Carlo simulation. A computer program PERFORM using Monte Carlo simulation is developed to implement the numerical computation. Simulation results based on pavement and traffic parameters show that traffic, surface layer material property, and initial pavement performance are the most significant factors affecting pavement performance. Once the distribution of future PSI is determined, statistics such as the mean and the variance of future PSI are readily available.
基金Supported by the Foundation of Beijing Science and Technology Commission, No. H010210110129
文摘AIM: To evaluate the efficiency and safety of combined recombinant human growth hormone (rhGH) and lactulose for treatment and/or prevention of multiple organ dysfunction in patients with chronic severe hepatitis B. METHODS: Forty-eight inpatients with chronic severe hepatitis B were randomly divided into rhGH group (n = 28)and control group (n = 20). In rhGH group, 4-4.5 IU of rhGH was injected intramuscularly once daily for 2-4 wk,and 100 mL of enema containing 30 mL of lactulose, 2 g of metronidazole and 0.9% saline was administered every 2 d for 2-4 wk. Their symptoms and complications were noted. Liver and kidney functions were analyzed by an Olympus analyzer. Serum GH, IGF-1, IGFBP1 and IGFBP3 were measured by ELISA.RESULTS: Clinical symptoms of 90% of these patients in rhGH group were obviously improved. The total effectiveness in rhGH group was better than that in control group (75% vs40%, P<0.05). After 2- and 4-wk treatment of rhGH respectively, serum albumin (26.1±4.1 vs 30.2±5.3,31.9±5.1 g/L), prealbumin (79.6±28.0 vs 106.6±54.4,108.4±55.0 g/L), cholesterol (76.3±16.7 vs 85.6±32.3,96.1±38.7 mg/dL), and IGFBP1 (56.8±47.2 vs 89.7±50.3ng/mL after 2 wk) were significantly increased compared to control group (P<0.05). However, serum GH was decreased. The increase of serum IGF1 and IGFBP3 after rhGH treatment was also observed.CONCLUSION: rhGH in combination with lactulose may be beneficial to the prevention and treatment of multiple organ dysfunction in patients with chronic severe hepatitis.
基金supported by the National Key R&D Program of China grant number 2018YFC0809400the science and technol-ogy foundation of State Grid Corporation of China grant number5200-202016243A-0-0-00the Innovation Fund of China Electric Power Research Institute grant number NY83-19-002。
文摘Influenced by strong winds associated with a southeastward-moving Mongolian cyclone,a severe transmission line galloping occurred in Baiyin City,Gansu Province,on 14 April 2020.This caused a tripping incident of the transmission line in this region.Based on the hourly,0.5°×0.5°,ECMWF ERA5 reanalysis data,this study investigated the formation mechanisms of the Mongolian cyclone and its associated strong winds.Results from the vorticity budget indicate that the convergence-related vertical stretching and the upward transport of cyclonic vorticity governed formation of the Mongolian cyclone in this event;whereas,tilting and export of cyclonic vorticity from the central region of the cyclone mainly decelerated the cyclone’s formation.The kinetic energy(KE)budget shows that the wind associated with the Mongolian cyclone was mainly enhanced by the positive work of the pressure gradient force.Unlike some typical strong wind events in Northwest China,during this event,no significant downward momentum transportation from the upper troposphere was found.The vertical transport of KE exerted a slightly favorable effect on the KE increase around the location where the transmission line galloping trip appeared.In contrast,the horizontal transport mainly caused an export of KE from this region,which applied an overall negative effect on the wind enhancement associated with the Mongolian cyclone.
基金funded by National Natural Science Foundation of China under Grant No.61171107Beijing Natural Science Foundation under Grant No.4122034+1 种基金863 Program of China under Grant No.2011AA100706the Fundamental Research Funds for the Central Universities under Grant No.G470519
文摘Energy conservation in Wireless Sensor Networks (WSNs) has always been a crucial issue and has received increased attention in the recent years. A transmission scheme for energy-constrained WSNs is proposed in this paper. The scheme, called MIHOP (MIMO and Multi-hop), combines cluster-based virtual MIMO and multi-hop technologies. The multihop mode is employed in transmitting data when the related sensors are located within a specific number of hops from the sink, and the virtual MIMO mode is used in transmitting data from the remaining sensor nodes. We compare the energy consumption of different transmission schemes and propose an algorithm for determining the optimal hop count in MIHOP. A controllable mobile sink that reduces the energy consumed in sensor transmission is also adopted for data collection. The theoretical analysis and the Monte Carlo simulation demonstrate that the proposed scheme significantly outperforms individual virtual MIMO, multi-hop technologies, and double-string networks in terms of energy conservation. The energy consumption levels under the MIHOP scheme are approximately 12.98%, 47.55% and 48.30% less than that under virtual MIMO schemes, multi-hop networks and doublestring networks, respectively.
文摘On basis of bond dissociation energies (BDEs) for BH2, B(OH)2, BCl2, and BCl, the diffusion Monte Carlo (DMC) method is applied to explore the BDEs of HB-H, HOB-OH, ClB-Cl, and B-Cl. The effect of the choice of orbitals, as well as the backflow transformation, is studied. The Slater-Jastrow DMC algorithm gives BDEs of 359.1±0.12 kJ/mol for HB-H, 410.5±0.50 kJ/mol for HOB-OH, 357.8±1.46 kJ/mol for ClB-Cl, and 504.5±0.96 kJ/mol for B-Cl using B3PW91 orbitals and similar BDEs when B3LYP orbitals are used. DMC with backflow corrections (BF-DMC) gives a HB-H BDE of 369.9±0.12 kJ/mol which is close to one of the available experimental value (375.8 kJ/mol). In the case of HOB-OH BDE, the BF-DMC calculation is 446.04-1.84 k J/mol that is closer to the experimental BDE. The BF-DMC BDE for ClB-Cl is 343.2±2.34 kJ/mol and the BF-DMC B-Cl BDE is 523.3±0.33 kJ/mol, which are close to the experimental BDEs, 341.9 and 530.0 kJ/mol, respectively.
基金Supported by the National Natural Science Foundation of China (20725622, 20706002, and 20876006), Beijing Nova Program (2008B15) and the Dutch STW/CW Separation Technology Program (700.56.655-DPC.6243).
文摘In this work grand canonical Monte Carlo simulations were performed to study gas separation in three pairs of isoreticular metal-organic frameworks (IRMOFs) with and without catenation at room temperature.Mixture composed of CO2 and H2 was selected as the model system to separate.The results show that CO2 selectivity in catenated MOFs with multi-porous frameworks is much higher than their non-catenated counterparts.The simulations also show that the electrostatic interactions are very important for the selectivity,and the contributions of different electrostatic interactions are different,depending on pore size,pressure and mixture composition.In fact,changing the electrostatic interactions can even qualitatively change the adsorption behavior.A general conclusion is that the electrostatic interactions between adsorbate molecules and the framework atoms play a dominant role at low pressures,and these interactions in catenated MOFs have much more pronounced effects than those in their non-catenated counterparts,while the electrostatic interactions between adsorbate molecules become evident with increasing pressure,and eventually dominant.
基金Project(2005CB623701) supported by the Major State Basic Research Development Program of China
文摘The effects of the cell parameter and chemical composition on the surface charge properties of five kinds of different colour montmorillonites were studied. The results indicate that the surface isoelectric point(IEP) of the montmorillonite shows positive correlation with the mass fractions of Fe203 and K20, but it has little relation to the mass fractions of other chemical compositions. At around pH=6.8, the surface zeta potential of the montmorillonite shows the negative relationship with the mass fractions of Fe203 and MgO, but it does not linearly correlate to the mass fractions of other chemical compositions. Cell parameter(bo) of the montmorillonite expresses negative linear relationship with mass fractions of K2O and Na2O, so does cosinβ with mass fractions of SlOE and Fe2O3. And there is no specific relationship between bo and IEP of different montmorillonites, but there is positive correlation between cosinβ and IEP of different montmorillonite samples.
基金Under the auspices of Public Welfare Scientific Research Project of Chinese Ministry of Land and Resource (No. 200911015-2)
文摘In this paper,we proposed a framework for evaluating the performance of ecosystem strategies prepared for enhancing vulnerability reduction in the face of hazards due to climate change.The framework highlights the positive effects of human activities in the coupled human and natural system(CHANS) by introducing adaptive capacity as an evaluation criterion.A built-in regional vulnerability to a certain hazard was generated based upon interaction of three dimensions of vulnerability:exposure,sensitivity and adaptive capacity.We illustrated the application of this framework in the temperate farming-grazing transitional zone in the middle Inner Mongolia of the northern China,where drought hazard is the key threat to the CHANS.Specific indices were produced to translate such climate variance and social-economic differences into specific indicators.The results showed that the most exposed regions are the inner land areas,while counties located in the eastern part are potentially the most adaptive ones.Ordos City and Bayannur City are most frequently influenced by multiple climate variances,showing highest sensitivity.Analysis also indicated that differences in the ability to adapt to changes are the main causes of spatial differences.After depiction of the spatial differentiations and analysis of the reasons,climate zones were divided to depict the differences in facing to the drought threats.The climate zones were shown to be similar to vulnerability zones based on the quantitative structure of indexes drafted by a triangular map.Further analysis of the composition of the vulnerability index showed that the evaluation criteria were effective in validating the spatial differentiation but potentially ineffective because of their limited time scope.This research will be a demonstration of how to combine the three dimensions by quantitative methods and will thus provide a guide for government to vulnerability reduction management.
基金Projects(51838001,51878070,51908069)supported by the National Natural Science Foundation of China。
文摘In this paper,organic montmorillonite(OMMT)was added into crumb rubber modified asphalt(CRMA)to improve its high temperature performance,anti-aging performance and storage stability.The effects of different OMMT content on properties of CRMA were studied.The rutting factor obtained by dynamic shear rheological(DSR)test was adopted to evaluate the high-temperature performance.The creep stiffness and m value determined by the bending beam rheometer(BBR)test were employed to evaluate the low-temperature performance.The softening point,ductility,rutting factor before and after rolling thin film ovens test(RTFOT)and pressure aging vessel test(PAV)were compared to characterize the aging properties.Moreover,the segregation test after being reserved for 48 h and 7 d was conducted,and the softening point and rutting factor of upper and lower layers of segregation pipe were adopted to evaluate the storage stability.The results indicated that the high-temperature performance and anti-aging performance were developed with the increasing content of OMMT,while the low-temperature performance deteriorated.The storage stability was improved with the increasing content of OMMT before the content exceeded 4%,after which the storage stability declined.Taking account of all factors,it is suggested that the optimum content of OMMT is 3%−4%.
基金Project supported by the National Natural Science Foundation of China (Nos. 40730105, 40501072 and 40673067)the National Key Basic Research Program (973 Program) of China (No. 2002CB412503)the Knowledge Innovation Program of the Chinese Academy of Sciences (No. KZCX2-YW-149)
文摘Precipitation is the major driver of ecosystem functions and processes in semiarid and arid regions. In such waterlimited ecosystems, pulsed water inputs directly control the belowground processes through a series of soil drying and rewetting cycles. To investigate the effects of sporadic addition of water on soil CO2 effux, an artificial precipitation event (3 mm) was applied to a desert shrub ecosystem in the Mu Us Sand Land of the Ordos Plateau in China. Soil respiration rate increased 2.8 4.1 times immediately after adding water in the field, and then it returned to background level within 48 h. During the experiment, soil CO2 production was between 2 047.0 and 7 383.0 mg m^-2. In the shrubland, soil respiration responses showed spatial variations, having stronger pulse effects beneath the shrubs than in the interplant spaces. The spatial variation of the soil respiration responses was closely related with the heterogeneity of soil substrate availability. Apart from precipitation, soil organic carbon and total nitrogen pool were also identified as determinants of soil CO2 loss in desert ecosystems.
基金Supported by China Scholarship Council(No.201306255014)
文摘In this paper, a sensing model for the coverage analysis of wireless sensor networks is provided. Using this model and Monte Carlo method, the ratio of private range to sensing range required to obtain the desired coverage can be derived considering the scale of deployment area and the number of sensor nodes. Base on the coverage analysis, an energy-efficient distributed node scheduling scheme is proposed to prolong the network lifetime while maintaining the desired sensing coverage, which does not need the geographic or neighbor information of nodes. The proposed scheme can also handle uneven distribution, and it is robust against node failures. Theoretical and simulation results demonstrate its efficiency and usefulness.
文摘Western heuristic teaching method was originated from Socrates who initiated the teaching mode of "teachers ask, students answer". A distinctive feature of this mode was that teachers were the decisive factor in the process of teaching and learning, who raised the questions at the very beginning and gave conclusions in the end. On the contrary, oriental style of heuristic teaching method based itself on the principle that students put forward their puzzles and then asked the teachers for advice. This paper will reconsider Confucius enlightening reflection and probe into how to develop students' ability of thinking by questioning strategies in the heuristic teaching methodology.
文摘To investigate the impact of antenna correlation on secrecy performance in MIMO wiretap channels with Nakagami-m fading, the expressions of secrecy outage probability and positive secrecy probability were derived. Diversity order and array gain were also achieved for further insight. The study was based on the information theory that physical layer security can be guaranteed when the quality of the main channel is higher than that of the eavesdropper's channel. Monte Carlo simulations well validated the numerical results of analytic expressions. It was shown that antenna correlation is detrimental to secrecy performance when average SNR of the main channel is at medium and high level. Interestingly, when average SNR of the main channel reduces to low level, the effect of antenna correlation becomes benefi cial to secrecy performance.