Here we report a left cheek plate of Psarolepis,a postparietal shield of Youngolepis,a skull of Diabolepis,and a scale of Styloichthys from the Lianhuashan and Nahkaoling formations(Lochkovian,Lower Devonian)of Nannin...Here we report a left cheek plate of Psarolepis,a postparietal shield of Youngolepis,a skull of Diabolepis,and a scale of Styloichthys from the Lianhuashan and Nahkaoling formations(Lochkovian,Lower Devonian)of Nanning,Guangxi.This marks the first report of Diabolepis and Styloichthys beside Qujing,Yunnan,and the latest occurrence of Psarolepis to date.The fossil community displays significant similarities to the Xujiachong Assemblage,and provides new data for the Lower Devonian stratigraphic correlation between southwestern China and northern Vietnam.Given the latest dating constraint based on the conodont evidence,we regard that the Xujiachong Assemblage has a much longer range than previously supposed,extending from the latest Lochkovian to the end of Pragian.We propose that the transition of the Nahkaoling and Lianhuashan formations in Nanning might correspond to the Guijiatun Formation in Qujing.The relatively large size of fish individuals from Guangxi is probably attributed to the increase in the oxygen content of the ocean.展开更多
Mineral contents and fractures of shale from well Yuye-1 and outcrops were examined mainly based on systematic description of the cores and outcrops, and data from experimental analyses. The data enabled us to thoroug...Mineral contents and fractures of shale from well Yuye-1 and outcrops were examined mainly based on systematic description of the cores and outcrops, and data from experimental analyses. The data enabled us to thoroughly explore the mineralogy and developmental features of shale of the Lower Silurian Longmaxi Formation in the study area. The results show that,the Lower Silurian Longmaxi Shale(SLS) in the southeastern margin of Sichuan Basin, China, is primarily characterized by a high content of brittle minerals and a relatively low content of clay minerals. The total content of brittle minerals is approximately 57%,including 27% quartz, 12.2% feldspar, 11.2% carbonate and 2.4% pyrite. The total content of clay minerals reaches 41.6%,composed of illite(23.8%), mixed-layer of illite and smectite(I/S)(10.8%) and chlorite(7.0%). The SLS accommodates the widespread development of various types of fractures, including tectonic fractures, diagenetic fractures, inter-layer fractures and slip fractures. The developmental level of the fracture in the SLS is mainly influenced by faults, lithology, mineral contents and total organic carbon content(TOC) in study area.展开更多
In the South Yellow Sea Basin,Mesozoic–Paleozoic marine strata are generally well developed with large thickness,and no substantial breakthroughs have been made in hydrocarbon exploration.Through research,it is belie...In the South Yellow Sea Basin,Mesozoic–Paleozoic marine strata are generally well developed with large thickness,and no substantial breakthroughs have been made in hydrocarbon exploration.Through research,it is believed that the Upper Permian–Lower Triassic can be regarded as a long-term base-level cycle.Based on drilling data,characteristics of the lithology–electric property combination cyclicity,and the special lithology,the long-term base-level cycle was divided into five medium-term base-level cycles(MC1–MC5).On this basis,the Permian–Triassic sedimentary systems and their filling model were analyzed in accordance with the change of base-level cycle and transition of sedimentary environment,as well as characteristics of the drilling sedimentary facies and seismic facies.The results show that there were six sedimentary systems(fluvial,delta,tidal flat,open platform,restricted platform,and continental shelf)developed in the Upper Permian–Lower Triassic,the sedimentary systems were distributed such that the water was deep in the northwest and shallow in the southeast,and there were two base-level cycle filling models(a relatively stable tidal flat facies and a rapidly transgressive continental shelf facies to stable platform facies)developed in the Upper Permian–Lower Triassic.These models can provide a basis for evaluation of the Mesozoic–Paleozoic hydrocarbon geology in the South Yellow Sea Basin.展开更多
A series of marine natural gas fields were recently discovered in oolitic dolomites of the Lower Triassic Feixianguan formation, northeastern Sichuan Basin, southwest China. The mechanism forming these reservoir dolom...A series of marine natural gas fields were recently discovered in oolitic dolomites of the Lower Triassic Feixianguan formation, northeastern Sichuan Basin, southwest China. The mechanism forming these reservoir dolomites is debatable, limiting the ability to characterize these reservoir successfully. Based on the investigation of the representative Dukouhe, Luojiazhai, and Puguang areas, this issue was addressed by examining the distribution, petrology, and geochemistry of the dolomites, the most comprehensive study to date was provided. Dolomitization occurred at a very early stage of diagenesis, as shown by the petrological features of the rock fabric. Vadose silt, which is composed primarily of dolomitic clasts, is found in the primary and secondary pores of the oolitic dolomite. This indicates that the overlying strata were subjected to dolomitization when the Feixianguan formation was located in the vadose zone. Therefore, it may be inferred that the dolomitization which occurred before the formation was exposed to meteoric conditions. The spatial distribution and geochemical characteristics of the dolomite indicate that dolomitization occurred as a result of seepage reflux. The degree of dolomitization decreases with increasing distance from the evaporative lagoon. Furthermore, the type and porosity of the dolomite vary in different zones of the upward-shoaling sequence, with the porosity gradually decreasing from the highest layer to the lowest layer. This reflects a close relationship between dolomitization and seawater evaporation during the formation of the dolomite. Geochemical analysis provided further evidence for the relationship between the dolomitization fluid and the coeval seawater. The 87Sr/86Sr and 813C isotopes, as well as the abundances of trace elements, Fe and Mn, indicate that seawater concentrated by evaporation acted as the dolomitization fluid. These results also show that dolomitization most likely occurred in a semi-closed diagenetic environment. Therefore, the main mechanism of oolitic dolomite formation is seepage reflux, which occurred at an early stage of diagenesis.展开更多
Eocene Fenghuoshan Group and lower Oligocene Yaxicuo Group are represented by mainly fluvial, lacustrine and fan\|deltaic redbeds cropping out in Hoh Xil basin, the largest redbed basin in northern Tibet plateau. Lith...Eocene Fenghuoshan Group and lower Oligocene Yaxicuo Group are represented by mainly fluvial, lacustrine and fan\|deltaic redbeds cropping out in Hoh Xil basin, the largest redbed basin in northern Tibet plateau. Lithic sandstone, lithic quartzose sandstone, conglomerate, as well as siltstone, consist of the major rock composition of the redbeds. The petrography of sandstone and conglomerate reveals the relationship between regional tectonic uplift events and the provenance of lower Tertiary redbeds.The outcrop rock data show that the detritus were derived from sedimentary rocks, volcanic rocks, and metamorphic rocks. Phyllite and quartzite rock fragments are most common in the metamorphic rock fragments .The sedimentary rock fragments are composed of chert, limestone, siltstone, and mudstone fragments. But volcanic rock fragments are minor and occasionally occur. In Hantaishan area, the northwestern part of Hoh Xil basin, clastic composition of sandstones and conglomerates testify to mainly southward and northeastward provenances. The metamorphic rock fragments, which are more common than volcanic and sedimentary rock fragments, can be directly correlated with metamorphic rock of Triassic metasedimentary Bayankara Group around the basin. In Fenghuoshan area, the southwestern part of the basin, there are less metamorphic rock fragment composition and more limestone fragments than in Hantaishan area.The limestone fragments were obviously derived from Carboniferous—Permian or Jurassic limestone beds. These limestone strata can not be found in the Bayankara block mass at which Hoh Xil basin locates, thus it is deduced that the limestone detritus were derived from the south, that is, Qiangtang blockmass.展开更多
The distribution of Lower Silurian conodonts from the sections on the Kozhym River was studied first by S.V. Melnikov.After additional studies of the Upper Ordovician-Lower Silurian strata,Oulodus? aff.nathani, Wallis...The distribution of Lower Silurian conodonts from the sections on the Kozhym River was studied first by S.V. Melnikov.After additional studies of the Upper Ordovician-Lower Silurian strata,Oulodus? aff.nathani, Walliserodus cf.curvatus,Panderodus sp.and Ozarkodina sp.were identified by P.M(a|¨)nnik in the Subpolar Urals.Studies of conodonts from the展开更多
Based on geographical and hydrological characteristics of lakes in the middle and lower reaches of Yangtze River, this paper analyzes the factors restricting the sustainable utilization of lake resources, including th...Based on geographical and hydrological characteristics of lakes in the middle and lower reaches of Yangtze River, this paper analyzes the factors restricting the sustainable utilization of lake resources, including the conflict among agriculture water conservancy, and fishery, lake water pollution and eutrophication, lake siltation and swamping. The countermeasures and suggestions, such as improving the strategic status of lake harnessing, strengthening integrated management of lakes and their watershed, strengthening researches on lake environment and lake resources, are proposed to practice the sustainable utilization of lake resources.展开更多
This paper presents an analysis of the changes of the longitudinal and lateral profiles in the meander- ing reach of the Lower Wei River over the period from October 1973 to October 1976 during the course of degradati...This paper presents an analysis of the changes of the longitudinal and lateral profiles in the meander- ing reach of the Lower Wei River over the period from October 1973 to October 1976 during the course of degradation.Analysis results indicated that retrogressive erosion and subsequent downstream erosion occurred in the reach due to the lowering in the Tongguan elevation and the inflowing water carrying low sediment con- centrations.At the end of the degradation,the main channel widths of the majority ...展开更多
Synchronization with lower SNR hadn't been considered by the conventional publications. Based on the Synchronized multi-carrier CDMA plus (SMCC+) system, which is one of the candidate schemes of digital terrestria...Synchronization with lower SNR hadn't been considered by the conventional publications. Based on the Synchronized multi-carrier CDMA plus (SMCC+) system, which is one of the candidate schemes of digital terrestrial TV broadcasting (DTTB) standard in China, a scheme under lower SNR with one short training sequence and one Barker code group, which were constructed in time domain. Computer simulation results show that the timing estimator here is designed to avoid the ambiguity which occured in Tufvesson's timing synchronization method. The 99.9% correct timing synchronization probability and lower false probability are got in AWGN and Rayleigh fading channels with SNR under -20 dB, and the optimum properties of frequency synchronization are obtained at the same time. It is shown that the proposed scheme is much better than the conventional synchronization methods.展开更多
Usually, only the Cramer-Rao lower bound （CRLB） of single target is taken into consideration in the state estimate of passive tracking systems. As for the case of multitarget, there are few works done due to its com...Usually, only the Cramer-Rao lower bound （CRLB） of single target is taken into consideration in the state estimate of passive tracking systems. As for the case of multitarget, there are few works done due to its complexity. The recursion formula of the posterior Cramer-Rao lower bound （PCRLB） in multitarget bearings-only tracking with the three kinds of data association is presented. Meanwhile, computer simulation is carried out for data association. The final result shows that the accuracy probability of data association has an important impact on the PCRLB.展开更多
River cutoff works have been implemented on Lower Jingjiang section for 30 years. Engineering practices have shown that channel straightening has been the river regulation measure for the permanent control of the mean...River cutoff works have been implemented on Lower Jingjiang section for 30 years. Engineering practices have shown that channel straightening has been the river regulation measure for the permanent control of the meandering Lower Jingjiang section. River cutoff have been carried out in accordance with the evolution property of meandering rivers and these works have brought about expected benefits. It has also been noted that certain aspects in river cutoff had not been fully understood. River cutoff is a dynamic engineering. River channel evolution properties shall be fully understood so as to adroitly guide actions according to circumstances in cutoff works. In addition, river channel evolution observation and engineering effectiveness monitoring should be strengthened with a view to update the designs. The diversion canals for channel shortening are of great importance that will account for the success or failure of river cutoff works. The newly formed river channels and the river regime control works on the adjacent upper and lower reaches are guarantees for river cutoff works to be brought into play in the long run.展开更多
Background Adjunct RCP to DHCA ensures some extent uninterrupted cerebral perfusion and that promotes one-stage repair of complex aortic arch anomaly.One-stage repair may induce longer myocardial ischemic time.So ther...Background Adjunct RCP to DHCA ensures some extent uninterrupted cerebral perfusion and that promotes one-stage repair of complex aortic arch anomaly.One-stage repair may induce longer myocardial ischemic time.So there evolved cerebral-myocardial perfusion to reduce myocardial ischemic time.Methods We reviewed 78 patients from January 2010 to July 2017 in our center.展开更多
The primary goal of this work is to characterize the impact of weighting selection strategy and multistatic geometry on the multistatic radar performance. With the relationship between the multistatic ambiguity functi...The primary goal of this work is to characterize the impact of weighting selection strategy and multistatic geometry on the multistatic radar performance. With the relationship between the multistatic ambiguity function （AF） and the multistatie Cram6r-Rao lower bound （CRLB）, the problem of calculating the multistatic AF and the multistatic CRLB as a performance metric for multistatic radar system is studied. Exactly, based on the proper selection of the system parameters, the multistatic radar performance can be significantly improved. The simulation results illustrate that the multistatic AF and the multistatic CRLB can serve as guidelines for future multistatic fusion rule development and multistatic radars deployment.展开更多
There are abundant water power resources in the Yalong River which are suitable for the large hydroelectric engineering. But a reliability study should be made for the valley which liable to frequent earthquakes. The ...There are abundant water power resources in the Yalong River which are suitable for the large hydroelectric engineering. But a reliability study should be made for the valley which liable to frequent earthquakes. The color infrared aerophotos, multi-spectral photography and thermal infrared scanning had been specially done besides MSS image, processing. Researches on remote sensing applications to engineering geology, hydrogeology, deformation of neo-tectonics, Iandslide, mud-rock flow, ecological environment and geographical information system had been carried out by more than 20 research units.展开更多
The evaluation method, model and process for the flood and waterlogging disaster condition by GIS,RS and GPS technology and the method for setting up disaster condition database, dyke database and historical disaster ...The evaluation method, model and process for the flood and waterlogging disaster condition by GIS,RS and GPS technology and the method for setting up disaster condition database, dyke database and historical disaster damage database are presented. An index of flood damage degree(FDD) used to evaluate the relative degree of disaster loss and divide flood and waterlogging area is suggested. The value of flood damage degree can be calculated as follows :taking the various disaster losses of sample area in a base year as standard value and computing the ratios of various disaster loss values in different areas and years to the standard flood disaster loss values, then summing up the weighted ratios. The computed results are the value of flood damage degree in the every year. The macroscopic flood disaster distribution can be evaluated by the values of flood loss degree.展开更多
Purpose To analyze the sources of errors and discuss the techniques to eliminate pitfalls in detecting deep vein thrombosis (DVT) of the proximal lower extremities with color duplex ultrasonography (CDUS). Methods Six...Purpose To analyze the sources of errors and discuss the techniques to eliminate pitfalls in detecting deep vein thrombosis (DVT) of the proximal lower extremities with color duplex ultrasonography (CDUS). Methods Sixty-eight cases with initial and repeat venous CDUS of the proximal lower extremities were retrospectively reviewed. The repeat was done within 24 hours after initial CDUS scanning. Comparing repeated images to initial ones, the pitfalls and sources of error in CDUS of the proximal lower extremities were discussed. Results In total 68 repeat studies, there were 62 results as same as initials and 4 cases of false negative DVT and 2 cases of false positive DVT. Conclusion Venous CDUS in detecting DVT is observer dependent. Some pitfalls and errors can be eliminated and corrected with proper scan techniques. CDUS is the most valuable imaging modality for assessing suspected DVT in the proximal lower extremities.展开更多
Modern human has different body proportion from early hominids and great apes.Comparing with others,in general,modern human adults have relatively long lower limb and heavier body weight.Since the lower limbs provide ...Modern human has different body proportion from early hominids and great apes.Comparing with others,in general,modern human adults have relatively long lower limb and heavier body weight.Since the lower limbs provide support to the whole body and play an important role in walking,it is proposed that the ratio of the lower limb to the whole body for modern human could be beneficial to bipedal walking.This study tried to estimate the muscle parameters of the lower limb in walking for the subjects with various body proportions.Using a simplified musculoskeletal model,some muscle parameters of the lower limb,e.g.muscle force,stress,work and power,were estimated for modern human adult,child,AL 288-1(the fossil specimens of Australopithecus afarensis,3.18 million years old)and apes.The results show that with the body proportion modern human adult spends less muscle work and power in walking than other subjects.The results imply that using the cost of transport(i.e.the muscle work of the lower limb per unit of displacement)as the criteria,the early hominids,if their body proportions were structurally similar to AL 288-1,could evolve towards what modern human adult looks like,in order to save energy during bipedal walking.展开更多
文摘Here we report a left cheek plate of Psarolepis,a postparietal shield of Youngolepis,a skull of Diabolepis,and a scale of Styloichthys from the Lianhuashan and Nahkaoling formations(Lochkovian,Lower Devonian)of Nanning,Guangxi.This marks the first report of Diabolepis and Styloichthys beside Qujing,Yunnan,and the latest occurrence of Psarolepis to date.The fossil community displays significant similarities to the Xujiachong Assemblage,and provides new data for the Lower Devonian stratigraphic correlation between southwestern China and northern Vietnam.Given the latest dating constraint based on the conodont evidence,we regard that the Xujiachong Assemblage has a much longer range than previously supposed,extending from the latest Lochkovian to the end of Pragian.We propose that the transition of the Nahkaoling and Lianhuashan formations in Nanning might correspond to the Guijiatun Formation in Qujing.The relatively large size of fish individuals from Guangxi is probably attributed to the increase in the oxygen content of the ocean.
基金Project(41302076)supported by the National Natural Science Foundation of ChinaProject(BJ14266)supported by Special Fund of Ministry of Science and Technology from the State Key Laboratory of Continental Dynamics(Northwest University),China
文摘Mineral contents and fractures of shale from well Yuye-1 and outcrops were examined mainly based on systematic description of the cores and outcrops, and data from experimental analyses. The data enabled us to thoroughly explore the mineralogy and developmental features of shale of the Lower Silurian Longmaxi Formation in the study area. The results show that,the Lower Silurian Longmaxi Shale(SLS) in the southeastern margin of Sichuan Basin, China, is primarily characterized by a high content of brittle minerals and a relatively low content of clay minerals. The total content of brittle minerals is approximately 57%,including 27% quartz, 12.2% feldspar, 11.2% carbonate and 2.4% pyrite. The total content of clay minerals reaches 41.6%,composed of illite(23.8%), mixed-layer of illite and smectite(I/S)(10.8%) and chlorite(7.0%). The SLS accommodates the widespread development of various types of fractures, including tectonic fractures, diagenetic fractures, inter-layer fractures and slip fractures. The developmental level of the fracture in the SLS is mainly influenced by faults, lithology, mineral contents and total organic carbon content(TOC) in study area.
基金Projects(41506080,41702162)supported by the National Natural Science Foundation of ChinaProjects(DD20160152,DD20160147,GZH200800503)supported by China Geological Survey+1 种基金Projects(XQ-2005-01,2009GYXQ10)supported by China Ministry of Land and ResourcesProject(201602004)supported by the Postdoctoral Innovation Foundation of Shandong Province,China
文摘In the South Yellow Sea Basin,Mesozoic–Paleozoic marine strata are generally well developed with large thickness,and no substantial breakthroughs have been made in hydrocarbon exploration.Through research,it is believed that the Upper Permian–Lower Triassic can be regarded as a long-term base-level cycle.Based on drilling data,characteristics of the lithology–electric property combination cyclicity,and the special lithology,the long-term base-level cycle was divided into five medium-term base-level cycles(MC1–MC5).On this basis,the Permian–Triassic sedimentary systems and their filling model were analyzed in accordance with the change of base-level cycle and transition of sedimentary environment,as well as characteristics of the drilling sedimentary facies and seismic facies.The results show that there were six sedimentary systems(fluvial,delta,tidal flat,open platform,restricted platform,and continental shelf)developed in the Upper Permian–Lower Triassic,the sedimentary systems were distributed such that the water was deep in the northwest and shallow in the southeast,and there were two base-level cycle filling models(a relatively stable tidal flat facies and a rapidly transgressive continental shelf facies to stable platform facies)developed in the Upper Permian–Lower Triassic.These models can provide a basis for evaluation of the Mesozoic–Paleozoic hydrocarbon geology in the South Yellow Sea Basin.
基金Project(2012CB214803)supported by the Major State Basic Research Development Program,ChinaProject(2011ZX5017-001-HZO2)supported by the National Science & Technology Special Project,China+1 种基金Project(2011D-5006-0105)supported by the PetroChina Research Fund,ChinaProject(SZD0414)supported by the Key Subject Construction Project of Sichuan Province,China
文摘A series of marine natural gas fields were recently discovered in oolitic dolomites of the Lower Triassic Feixianguan formation, northeastern Sichuan Basin, southwest China. The mechanism forming these reservoir dolomites is debatable, limiting the ability to characterize these reservoir successfully. Based on the investigation of the representative Dukouhe, Luojiazhai, and Puguang areas, this issue was addressed by examining the distribution, petrology, and geochemistry of the dolomites, the most comprehensive study to date was provided. Dolomitization occurred at a very early stage of diagenesis, as shown by the petrological features of the rock fabric. Vadose silt, which is composed primarily of dolomitic clasts, is found in the primary and secondary pores of the oolitic dolomite. This indicates that the overlying strata were subjected to dolomitization when the Feixianguan formation was located in the vadose zone. Therefore, it may be inferred that the dolomitization which occurred before the formation was exposed to meteoric conditions. The spatial distribution and geochemical characteristics of the dolomite indicate that dolomitization occurred as a result of seepage reflux. The degree of dolomitization decreases with increasing distance from the evaporative lagoon. Furthermore, the type and porosity of the dolomite vary in different zones of the upward-shoaling sequence, with the porosity gradually decreasing from the highest layer to the lowest layer. This reflects a close relationship between dolomitization and seawater evaporation during the formation of the dolomite. Geochemical analysis provided further evidence for the relationship between the dolomitization fluid and the coeval seawater. The 87Sr/86Sr and 813C isotopes, as well as the abundances of trace elements, Fe and Mn, indicate that seawater concentrated by evaporation acted as the dolomitization fluid. These results also show that dolomitization most likely occurred in a semi-closed diagenetic environment. Therefore, the main mechanism of oolitic dolomite formation is seepage reflux, which occurred at an early stage of diagenesis.
文摘Eocene Fenghuoshan Group and lower Oligocene Yaxicuo Group are represented by mainly fluvial, lacustrine and fan\|deltaic redbeds cropping out in Hoh Xil basin, the largest redbed basin in northern Tibet plateau. Lithic sandstone, lithic quartzose sandstone, conglomerate, as well as siltstone, consist of the major rock composition of the redbeds. The petrography of sandstone and conglomerate reveals the relationship between regional tectonic uplift events and the provenance of lower Tertiary redbeds.The outcrop rock data show that the detritus were derived from sedimentary rocks, volcanic rocks, and metamorphic rocks. Phyllite and quartzite rock fragments are most common in the metamorphic rock fragments .The sedimentary rock fragments are composed of chert, limestone, siltstone, and mudstone fragments. But volcanic rock fragments are minor and occasionally occur. In Hantaishan area, the northwestern part of Hoh Xil basin, clastic composition of sandstones and conglomerates testify to mainly southward and northeastward provenances. The metamorphic rock fragments, which are more common than volcanic and sedimentary rock fragments, can be directly correlated with metamorphic rock of Triassic metasedimentary Bayankara Group around the basin. In Fenghuoshan area, the southwestern part of the basin, there are less metamorphic rock fragment composition and more limestone fragments than in Hantaishan area.The limestone fragments were obviously derived from Carboniferous—Permian or Jurassic limestone beds. These limestone strata can not be found in the Bayankara block mass at which Hoh Xil basin locates, thus it is deduced that the limestone detritus were derived from the south, that is, Qiangtang blockmass.
文摘The distribution of Lower Silurian conodonts from the sections on the Kozhym River was studied first by S.V. Melnikov.After additional studies of the Upper Ordovician-Lower Silurian strata,Oulodus? aff.nathani, Walliserodus cf.curvatus,Panderodus sp.and Ozarkodina sp.were identified by P.M(a|¨)nnik in the Subpolar Urals.Studies of conodonts from the
文摘Based on geographical and hydrological characteristics of lakes in the middle and lower reaches of Yangtze River, this paper analyzes the factors restricting the sustainable utilization of lake resources, including the conflict among agriculture water conservancy, and fishery, lake water pollution and eutrophication, lake siltation and swamping. The countermeasures and suggestions, such as improving the strategic status of lake harnessing, strengthening integrated management of lakes and their watershed, strengthening researches on lake environment and lake resources, are proposed to practice the sustainable utilization of lake resources.
基金Supported by the Natural Science Foundation of China (50409002)by the Science Fund for Creative Research Groups of the Natural Science Foundation of China (50221903).
文摘This paper presents an analysis of the changes of the longitudinal and lateral profiles in the meander- ing reach of the Lower Wei River over the period from October 1973 to October 1976 during the course of degradation.Analysis results indicated that retrogressive erosion and subsequent downstream erosion occurred in the reach due to the lowering in the Tongguan elevation and the inflowing water carrying low sediment con- centrations.At the end of the degradation,the main channel widths of the majority ...
文摘Synchronization with lower SNR hadn't been considered by the conventional publications. Based on the Synchronized multi-carrier CDMA plus (SMCC+) system, which is one of the candidate schemes of digital terrestrial TV broadcasting (DTTB) standard in China, a scheme under lower SNR with one short training sequence and one Barker code group, which were constructed in time domain. Computer simulation results show that the timing estimator here is designed to avoid the ambiguity which occured in Tufvesson's timing synchronization method. The 99.9% correct timing synchronization probability and lower false probability are got in AWGN and Rayleigh fading channels with SNR under -20 dB, and the optimum properties of frequency synchronization are obtained at the same time. It is shown that the proposed scheme is much better than the conventional synchronization methods.
文摘Usually, only the Cramer-Rao lower bound （CRLB） of single target is taken into consideration in the state estimate of passive tracking systems. As for the case of multitarget, there are few works done due to its complexity. The recursion formula of the posterior Cramer-Rao lower bound （PCRLB） in multitarget bearings-only tracking with the three kinds of data association is presented. Meanwhile, computer simulation is carried out for data association. The final result shows that the accuracy probability of data association has an important impact on the PCRLB.
文摘River cutoff works have been implemented on Lower Jingjiang section for 30 years. Engineering practices have shown that channel straightening has been the river regulation measure for the permanent control of the meandering Lower Jingjiang section. River cutoff have been carried out in accordance with the evolution property of meandering rivers and these works have brought about expected benefits. It has also been noted that certain aspects in river cutoff had not been fully understood. River cutoff is a dynamic engineering. River channel evolution properties shall be fully understood so as to adroitly guide actions according to circumstances in cutoff works. In addition, river channel evolution observation and engineering effectiveness monitoring should be strengthened with a view to update the designs. The diversion canals for channel shortening are of great importance that will account for the success or failure of river cutoff works. The newly formed river channels and the river regime control works on the adjacent upper and lower reaches are guarantees for river cutoff works to be brought into play in the long run.
文摘Background Adjunct RCP to DHCA ensures some extent uninterrupted cerebral perfusion and that promotes one-stage repair of complex aortic arch anomaly.One-stage repair may induce longer myocardial ischemic time.So there evolved cerebral-myocardial perfusion to reduce myocardial ischemic time.Methods We reviewed 78 patients from January 2010 to July 2017 in our center.
基金Project(61271441)supported by the National Natural Science Foundation of ChinaProject(NCET-10-0895)supported by the Program for New Century Excellent Talents in Universities of China
文摘The primary goal of this work is to characterize the impact of weighting selection strategy and multistatic geometry on the multistatic radar performance. With the relationship between the multistatic ambiguity function （AF） and the multistatie Cram6r-Rao lower bound （CRLB）, the problem of calculating the multistatic AF and the multistatic CRLB as a performance metric for multistatic radar system is studied. Exactly, based on the proper selection of the system parameters, the multistatic radar performance can be significantly improved. The simulation results illustrate that the multistatic AF and the multistatic CRLB can serve as guidelines for future multistatic fusion rule development and multistatic radars deployment.
文摘There are abundant water power resources in the Yalong River which are suitable for the large hydroelectric engineering. But a reliability study should be made for the valley which liable to frequent earthquakes. The color infrared aerophotos, multi-spectral photography and thermal infrared scanning had been specially done besides MSS image, processing. Researches on remote sensing applications to engineering geology, hydrogeology, deformation of neo-tectonics, Iandslide, mud-rock flow, ecological environment and geographical information system had been carried out by more than 20 research units.
文摘The evaluation method, model and process for the flood and waterlogging disaster condition by GIS,RS and GPS technology and the method for setting up disaster condition database, dyke database and historical disaster damage database are presented. An index of flood damage degree(FDD) used to evaluate the relative degree of disaster loss and divide flood and waterlogging area is suggested. The value of flood damage degree can be calculated as follows :taking the various disaster losses of sample area in a base year as standard value and computing the ratios of various disaster loss values in different areas and years to the standard flood disaster loss values, then summing up the weighted ratios. The computed results are the value of flood damage degree in the every year. The macroscopic flood disaster distribution can be evaluated by the values of flood loss degree.
文摘Purpose To analyze the sources of errors and discuss the techniques to eliminate pitfalls in detecting deep vein thrombosis (DVT) of the proximal lower extremities with color duplex ultrasonography (CDUS). Methods Sixty-eight cases with initial and repeat venous CDUS of the proximal lower extremities were retrospectively reviewed. The repeat was done within 24 hours after initial CDUS scanning. Comparing repeated images to initial ones, the pitfalls and sources of error in CDUS of the proximal lower extremities were discussed. Results In total 68 repeat studies, there were 62 results as same as initials and 4 cases of false negative DVT and 2 cases of false positive DVT. Conclusion Venous CDUS in detecting DVT is observer dependent. Some pitfalls and errors can be eliminated and corrected with proper scan techniques. CDUS is the most valuable imaging modality for assessing suspected DVT in the proximal lower extremities.
基金Supported in part by the grants fromthe BiotechnologyBiological Sciences Research Council,the Leverhulme Trustthe Natural Environment Research Council,U.K.
文摘Modern human has different body proportion from early hominids and great apes.Comparing with others,in general,modern human adults have relatively long lower limb and heavier body weight.Since the lower limbs provide support to the whole body and play an important role in walking,it is proposed that the ratio of the lower limb to the whole body for modern human could be beneficial to bipedal walking.This study tried to estimate the muscle parameters of the lower limb in walking for the subjects with various body proportions.Using a simplified musculoskeletal model,some muscle parameters of the lower limb,e.g.muscle force,stress,work and power,were estimated for modern human adult,child,AL 288-1(the fossil specimens of Australopithecus afarensis,3.18 million years old)and apes.The results show that with the body proportion modern human adult spends less muscle work and power in walking than other subjects.The results imply that using the cost of transport(i.e.the muscle work of the lower limb per unit of displacement)as the criteria,the early hominids,if their body proportions were structurally similar to AL 288-1,could evolve towards what modern human adult looks like,in order to save energy during bipedal walking.
