A stratum grouting-soil-structure interaction model which simplified the grouted zone into a series of spherical grout bulbs was established using FLAC3D program. The hypothetical non-uniform expansion process to reac...A stratum grouting-soil-structure interaction model which simplified the grouted zone into a series of spherical grout bulbs was established using FLAC3D program. The hypothetical non-uniform expansion process to reach an assigned volume strain due to soil compression by grouting was achieved by imposing radial velocity on outer mesh nodes of these spheres. This new method avoids the repeated trial calculation needed in the traditional method which applied a fictitious expanding pressure in the grouting element. The deformation and additional internal forces of structure were investigated during each grouting strategy and the influences of various stiffness of grouting proof curtain and bearing capacity of pile tip were discussed simultaneously. The numerical model is proved to be effective to replicate general behavior expected in the field and is capable of modeling the uplifting effect for the surface structure by grouting.展开更多
The ecological environment in the East China Sea(ECS)and the Yellow Sea(YS)has changed significantly due to sea-level rising and the Kuroshio incursion since the last deglaciation.In this study,biomarker records of co...The ecological environment in the East China Sea(ECS)and the Yellow Sea(YS)has changed significantly due to sea-level rising and the Kuroshio incursion since the last deglaciation.In this study,biomarker records of core F10B from the mud area southwest off Cheju Island(MSWCI)were generated to evaluate phytoplankton productivity and community structure changes in response to environmental evolution during the last 14 kyr.The contents of diatom,dinoflagellate and haptophyte biomarkers(brassicasterol,dinosterol and C37alkenones)display similar trends,with increasing phytoplankton productivity during the last 14kyr due to the increased influences of the Kuroshio,and especially due to the eddy-induced upwelling during the late Holocene.On the other hand,the contents of terrestrial biomarkers(C28+C30+C32n-alkanols)and terrestrial organic matter(TOM)proxies(TMBR′and BIT)all reveal decreasing TOM input into the area around the sampling site for the 14 kyr,mostly due to sea-level ris-ing.Phytoplankton biomarker ratios reveal a shift from a haptophyte-dominated community at 6.2 2.5 kyr BP to a diatom-dominated community at 2.5 1.45 kyr BP,likely caused by a stronger cold eddy circulation system at 2.5 1.45 kyr BP in the MSWCI.展开更多
A new iron-making process using carburized pre-reduced iron ore pellets and microwave heating is investigated. The pre-reduced pellets, with a porous structure, and fine particles are carburized homogeneously at 400-6...A new iron-making process using carburized pre-reduced iron ore pellets and microwave heating is investigated. The pre-reduced pellets, with a porous structure, and fine particles are carburized homogeneously at 400-650 ℃ in a CO atmosphere. The carburized carbon not only acts reaction as a reduction agent, but also absorbs microwave in the reduction process. Hence, the carburized pre-reduced pellets can be rapidly reduced by microwave heating. There are three procedures involved in the process, namely, gas-based pre-reduction, low-temperatttre carburization and deep reduction by microwave heating. Carburized pre-reduced iron ore pellets show a rapid temperature rise that is twice as fast as the results for pre-reduced pellets in the laboratory. This not only improves the efficiency of the microwave heating, but also accelerates the reduction of iron oxides. The temperature of the pre-reduced pellets rises to 1050 ℃ in 45 min when the carburization rate is 2.02%, and the metallization rate and compressive strength reach 94.24% and 1725 N/pellet, respectively.展开更多
In this paper we discuss the basic properti es of hyper relationR i, which is upgraded from the base re lation R. The relationship between R i and R is con sidered.
Splash zone crossing of the structures with large horizontal surface （e.g. manifolds） and the structures having large weight variation in water and air （e.g. suction anchors） is a critical marine operation. This i...Splash zone crossing of the structures with large horizontal surface （e.g. manifolds） and the structures having large weight variation in water and air （e.g. suction anchors） is a critical marine operation. This is due to the large slamming forces and added mass of the structure, which results in high dynamic loads on the crane. The solution to this could be attaching a PHC （Passive Heave Compensator） between the crane hook and the payload. This paper analyzes the deployment of a subsea manifold with and without PHC unit in North Sea at a water depth of approximately 370 m. A detailed dynamic analysis is done for a seastate of 3 m significant wave height （Hs） over a range of zero up-crossing period （Tz） varying from 3s to 13 s. For better understanding of the result analysis has been done in two stages. The first stage covers the lowering of manifold through the splash zone while second stage covers the seabed landing of the manifold. Based on the results of the analyses it is concluded that PHC tends to reduce the dynamic peak load on the crane. Besides this, it also mitigates the risk of slack wire situations during splash zone crossing of the payload. Furthermore, reduction in both landing velocity and crane tip velocity is also achieved by using a well-designed PHC unit.展开更多
In large cities, news about fires in buildings are powered by problems such as old wiring and no maintenance. Accidents with chemicals and human error, which when added to the different characteristics of each fire an...In large cities, news about fires in buildings are powered by problems such as old wiring and no maintenance. Accidents with chemicals and human error, which when added to the different characteristics of each fire and structures can generate the factors causing these disasters. The gradual rise in temperature causes a different effect in mortar and concrete parts, verifying the change in coloring provided to loss of mechanical strength and surface crumbling, cracking and disintegration of the structure itself. This paper presents a case study in which a building that is located in the metropolitan region of Recife was exposed to a fire situation. The metropolitan region of Recife is composed of several old buildings that by virtue of their age may have delayed construction methods, and may expose the fragility of the concrete used in its construction on a fire situation. The concrete structures are recognized by the good resistance to fire because of the thermal characteristics of the material, however, the temperature rise in the concrete elements in characteristic causes a reduction in strength and modulus of elasticity of the material, the loss in stiffness leading to polyphase degradation of reinforced concrete, structural parts can lead to ruin, but when properly sized and executed, the concrete can serve as a proactive agent to be exposed to high temperatures, as the same may be subjected to high temperatures accidentally or they may be part of their normal work.展开更多
The inverted charge structure formation of a hailstorm was investigated using the Advanced Weather Research and Forecasting（WRF-ARW） model coupled with electrification and discharge schemes. Different processes may ...The inverted charge structure formation of a hailstorm was investigated using the Advanced Weather Research and Forecasting（WRF-ARW） model coupled with electrification and discharge schemes. Different processes may be responsible for inverted charge structure in different storms and regions.A dynamical-derived mechanism of inverted charge structure formation was confirmed by the numerical model： the inverted structure was formed by strong updraft and downdraft under normal-polarity charging conditions such that the graupel charged negatively in the main charging region in the middle-upper level of the cloud. The simulation results showed the storm presented a normal charge structure before and after hail-fall; while during the hail-fall stage, it showed an inverted charge structure—negative charge region in the upper level of the cloud and a positive charge region in the middle level of the cloud—appearing at the front edge near the strong updraft in the hailstorm. The charging processes between the two particles mainly occurred at the top of the cloud, where the graupel charged negatively and ice crystals positively due to the strong updraft. When the updraft air reached the top of the storm, it would spread to the rear and front. The light ice crystals were transported backward and forward more easily. Meanwhile, the positively charged ice crystals were transported downward by the frontal subsidence, and then a positive charge region formed between the -10°C and -25°C levels. Subsequently, a negative charge region materialized in the upper level of the cloud, and the inverted charge structure formed.展开更多
The purpose of this study was to understand the reasons why frequent positive cloud-to-ground(+CG) flashes occur in severe thunderstorms. A three-dimensional dynamics-electrification coupled model was used to simulate...The purpose of this study was to understand the reasons why frequent positive cloud-to-ground(+CG) flashes occur in severe thunderstorms. A three-dimensional dynamics-electrification coupled model was used to simulate a severe thunderstorm to permit analysis of the conditions that might easily cause +CG flashes. The results showed that strong updrafts play an important role in the occurrence of intracloud flashes. However, frequent +CG flashes require not only strong updrafts but also strong downdrafts in the lower cloud region, conditions that correspond to the later phase of the mature stage and the period of the heaviest solid precipitation of a thunderstorm. During this stage, strong updrafts elevated each charge area in the updraft region to a higher level, which resulted in an inverted tripole charge structure. A wide mid-level region of strong positive charge caused largely by positively charged graupel, presented in the middle of the updraft region because of a non-inductive ice-ice collisional charging mechanism. The charge structure in the downdraft region was consistently more complex and revealed several vertically stacked charge regions, alternating in polarity. Much of the graupel/hail outside the updrafts was lowered to cloud-base by strong downdrafts. In this area, the graupel/hail was charged negatively because of the transportation of negatively charged graupel/hail from higher regions of negative charge in the updrafts, and via the inductive charging mechanism of collisions between graupel/hail and cloud droplets at the bottom of the cloud. Consequently, a large region of negative charge formed near the ground. This meant that +CG flashes were initiated more easily in the lower inverted dipole, i.e., the middle region of positive charge and lower region of negative charge. Frequent +CG flashes began almost synchronously with dramatic increases in the storm updrafts, hail volume, and total flash rate. Therefore, the occurrence of +CG flashes appears a good indicator of storm intensification and it could have some use as a predictor of severe weather in the form of hail.展开更多
Two-dimensional （2D） MoS2 is used as a catalyst or support and has received increased research interest because of its superior structural and electronic properties compared with those of bulk structures. In this ar...Two-dimensional （2D） MoS2 is used as a catalyst or support and has received increased research interest because of its superior structural and electronic properties compared with those of bulk structures. In this article, we illustrate the active sites of 2D MoS2 and various strategies for enhancing its intrinsic catalytic activity. The recent advances in the use of 2D MoS2-based materials for applications such as thermocatalysis, electrocatalysis, and photocatalysis are discussed. We also discuss the future opportunities and challenges for 2D MoS2-based materials, in both fundamental research and industrial applications.展开更多
基金Project(2007AA11Z134)supported by the National High Technology Research and Development Program of ChinaProject(10JJ4035)supported by the Natural Science Foundation of Hunan Province,ChinaProject(2010ybfz046)supported by the Fund of Excellent Doctoral Dissertation of Central South University,China
文摘A stratum grouting-soil-structure interaction model which simplified the grouted zone into a series of spherical grout bulbs was established using FLAC3D program. The hypothetical non-uniform expansion process to reach an assigned volume strain due to soil compression by grouting was achieved by imposing radial velocity on outer mesh nodes of these spheres. This new method avoids the repeated trial calculation needed in the traditional method which applied a fictitious expanding pressure in the grouting element. The deformation and additional internal forces of structure were investigated during each grouting strategy and the influences of various stiffness of grouting proof curtain and bearing capacity of pile tip were discussed simultaneously. The numerical model is proved to be effective to replicate general behavior expected in the field and is capable of modeling the uplifting effect for the surface structure by grouting.
基金supported by the National Basic Research Program of China (973 Program 2010CB428901)the National Natural Science Foundation of China (Grant Nos.41020164005,41221004)the ‘111’ Project
文摘The ecological environment in the East China Sea(ECS)and the Yellow Sea(YS)has changed significantly due to sea-level rising and the Kuroshio incursion since the last deglaciation.In this study,biomarker records of core F10B from the mud area southwest off Cheju Island(MSWCI)were generated to evaluate phytoplankton productivity and community structure changes in response to environmental evolution during the last 14 kyr.The contents of diatom,dinoflagellate and haptophyte biomarkers(brassicasterol,dinosterol and C37alkenones)display similar trends,with increasing phytoplankton productivity during the last 14kyr due to the increased influences of the Kuroshio,and especially due to the eddy-induced upwelling during the late Holocene.On the other hand,the contents of terrestrial biomarkers(C28+C30+C32n-alkanols)and terrestrial organic matter(TOM)proxies(TMBR′and BIT)all reveal decreasing TOM input into the area around the sampling site for the 14 kyr,mostly due to sea-level ris-ing.Phytoplankton biomarker ratios reveal a shift from a haptophyte-dominated community at 6.2 2.5 kyr BP to a diatom-dominated community at 2.5 1.45 kyr BP,likely caused by a stronger cold eddy circulation system at 2.5 1.45 kyr BP in the MSWCI.
基金Project(NCET-04-0748)supported by the New Century Excellent Talent Planning of China
文摘A new iron-making process using carburized pre-reduced iron ore pellets and microwave heating is investigated. The pre-reduced pellets, with a porous structure, and fine particles are carburized homogeneously at 400-650 ℃ in a CO atmosphere. The carburized carbon not only acts reaction as a reduction agent, but also absorbs microwave in the reduction process. Hence, the carburized pre-reduced pellets can be rapidly reduced by microwave heating. There are three procedures involved in the process, namely, gas-based pre-reduction, low-temperatttre carburization and deep reduction by microwave heating. Carburized pre-reduced iron ore pellets show a rapid temperature rise that is twice as fast as the results for pre-reduced pellets in the laboratory. This not only improves the efficiency of the microwave heating, but also accelerates the reduction of iron oxides. The temperature of the pre-reduced pellets rises to 1050 ℃ in 45 min when the carburization rate is 2.02%, and the metallization rate and compressive strength reach 94.24% and 1725 N/pellet, respectively.
文摘In this paper we discuss the basic properti es of hyper relationR i, which is upgraded from the base re lation R. The relationship between R i and R is con sidered.
文摘Splash zone crossing of the structures with large horizontal surface （e.g. manifolds） and the structures having large weight variation in water and air （e.g. suction anchors） is a critical marine operation. This is due to the large slamming forces and added mass of the structure, which results in high dynamic loads on the crane. The solution to this could be attaching a PHC （Passive Heave Compensator） between the crane hook and the payload. This paper analyzes the deployment of a subsea manifold with and without PHC unit in North Sea at a water depth of approximately 370 m. A detailed dynamic analysis is done for a seastate of 3 m significant wave height （Hs） over a range of zero up-crossing period （Tz） varying from 3s to 13 s. For better understanding of the result analysis has been done in two stages. The first stage covers the lowering of manifold through the splash zone while second stage covers the seabed landing of the manifold. Based on the results of the analyses it is concluded that PHC tends to reduce the dynamic peak load on the crane. Besides this, it also mitigates the risk of slack wire situations during splash zone crossing of the payload. Furthermore, reduction in both landing velocity and crane tip velocity is also achieved by using a well-designed PHC unit.
文摘In large cities, news about fires in buildings are powered by problems such as old wiring and no maintenance. Accidents with chemicals and human error, which when added to the different characteristics of each fire and structures can generate the factors causing these disasters. The gradual rise in temperature causes a different effect in mortar and concrete parts, verifying the change in coloring provided to loss of mechanical strength and surface crumbling, cracking and disintegration of the structure itself. This paper presents a case study in which a building that is located in the metropolitan region of Recife was exposed to a fire situation. The metropolitan region of Recife is composed of several old buildings that by virtue of their age may have delayed construction methods, and may expose the fragility of the concrete used in its construction on a fire situation. The concrete structures are recognized by the good resistance to fire because of the thermal characteristics of the material, however, the temperature rise in the concrete elements in characteristic causes a reduction in strength and modulus of elasticity of the material, the loss in stiffness leading to polyphase degradation of reinforced concrete, structural parts can lead to ruin, but when properly sized and executed, the concrete can serve as a proactive agent to be exposed to high temperatures, as the same may be subjected to high temperatures accidentally or they may be part of their normal work.
基金supported by the National Key Basic Research and Development Program of China (Grant No. 2014CB441406)the National Natural Science Foundation of China (Grant Nos. 91537209 & 41405005)the Basic Research Fund of Chinese Academy of Meteorological Sciences (Grant No. 2014R017)
文摘The inverted charge structure formation of a hailstorm was investigated using the Advanced Weather Research and Forecasting（WRF-ARW） model coupled with electrification and discharge schemes. Different processes may be responsible for inverted charge structure in different storms and regions.A dynamical-derived mechanism of inverted charge structure formation was confirmed by the numerical model： the inverted structure was formed by strong updraft and downdraft under normal-polarity charging conditions such that the graupel charged negatively in the main charging region in the middle-upper level of the cloud. The simulation results showed the storm presented a normal charge structure before and after hail-fall; while during the hail-fall stage, it showed an inverted charge structure—negative charge region in the upper level of the cloud and a positive charge region in the middle level of the cloud—appearing at the front edge near the strong updraft in the hailstorm. The charging processes between the two particles mainly occurred at the top of the cloud, where the graupel charged negatively and ice crystals positively due to the strong updraft. When the updraft air reached the top of the storm, it would spread to the rear and front. The light ice crystals were transported backward and forward more easily. Meanwhile, the positively charged ice crystals were transported downward by the frontal subsidence, and then a positive charge region formed between the -10°C and -25°C levels. Subsequently, a negative charge region materialized in the upper level of the cloud, and the inverted charge structure formed.
基金supported by the National Key Basic Research Program of China (Grant No. 2014CB441403)the National Natural Science Foundation of China (Grant No. 41275008)+1 种基金R&D Special Fund for Public Welfare Industry (Grant No. GYHY201306069)Open Project of Key Laboratory of Meteorological Disaster of Ministry of Education (Grant No. KLME1004)
文摘The purpose of this study was to understand the reasons why frequent positive cloud-to-ground(+CG) flashes occur in severe thunderstorms. A three-dimensional dynamics-electrification coupled model was used to simulate a severe thunderstorm to permit analysis of the conditions that might easily cause +CG flashes. The results showed that strong updrafts play an important role in the occurrence of intracloud flashes. However, frequent +CG flashes require not only strong updrafts but also strong downdrafts in the lower cloud region, conditions that correspond to the later phase of the mature stage and the period of the heaviest solid precipitation of a thunderstorm. During this stage, strong updrafts elevated each charge area in the updraft region to a higher level, which resulted in an inverted tripole charge structure. A wide mid-level region of strong positive charge caused largely by positively charged graupel, presented in the middle of the updraft region because of a non-inductive ice-ice collisional charging mechanism. The charge structure in the downdraft region was consistently more complex and revealed several vertically stacked charge regions, alternating in polarity. Much of the graupel/hail outside the updrafts was lowered to cloud-base by strong downdrafts. In this area, the graupel/hail was charged negatively because of the transportation of negatively charged graupel/hail from higher regions of negative charge in the updrafts, and via the inductive charging mechanism of collisions between graupel/hail and cloud droplets at the bottom of the cloud. Consequently, a large region of negative charge formed near the ground. This meant that +CG flashes were initiated more easily in the lower inverted dipole, i.e., the middle region of positive charge and lower region of negative charge. Frequent +CG flashes began almost synchronously with dramatic increases in the storm updrafts, hail volume, and total flash rate. Therefore, the occurrence of +CG flashes appears a good indicator of storm intensification and it could have some use as a predictor of severe weather in the form of hail.
基金We gratefully acknowledge the financial support from the Ministry of Science and Technology of China （Grant Nos. 2016YFA0204100 and 2016YFA0200200）, the Na- tional Natural Science Foundation of China （Grant Nos. 21573220 and 21621063）, the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences （Grant No. QYZDB-SSW- JSC020）, and the Strategic Priority Research Program of the Chi- nese Academy of Sciences （Grant No. XDA09030100）.
文摘Two-dimensional （2D） MoS2 is used as a catalyst or support and has received increased research interest because of its superior structural and electronic properties compared with those of bulk structures. In this article, we illustrate the active sites of 2D MoS2 and various strategies for enhancing its intrinsic catalytic activity. The recent advances in the use of 2D MoS2-based materials for applications such as thermocatalysis, electrocatalysis, and photocatalysis are discussed. We also discuss the future opportunities and challenges for 2D MoS2-based materials, in both fundamental research and industrial applications.
