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Search Results: 1 - 10 of 81063 matches for " Shuguang Liu "
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Detachment within subducted continental crust and multi-slice successive exhumation of ultrahigh-pressure metamorphic rocks: Evidence from the Dabie-Sulu orogenic belt
YiCan Liu,ShuGuang Li
Chinese Science Bulletin , 2008, DOI: 10.1007/s11434-008-0387-1
Abstract: Although tectonic models were presented for exhumation of ultrahigh-pressure (UHP) metamorphic rocks during the continental collision, there is increasing evidence for the decoupling between crustal slices at various depths within deeply subducted continental crust. This lends support to the multi-slice successive exhumation model of the UHP metamorphic rocks in the Dabie-Sulu orogen. The available evidence is summarized as follows: (1) the low-grade metamorphic slices, which have geotectonic affinity to the South China Block and part of them records the Triassic metamorphism, occur in the northern margin of the Dabie-Sulu UHP metamorphic zone, suggesting decoupling of the upper crust from the underlying basement during the initial stages of continental subduction; (2) the Dabie and Sulu HP to UHP metamorphic zones comprise several HP to UHP slices, which have an increased trend of metamorphic grade from south to north but a decreased trend of peak metamorphic ages correspondingly; and (3) the Chinese Continental Science Drilling (CCSD) project at Donghai in the Sulu orogen reveals that the UHP metamorphic zone is composed of several stacked slices, which display distinctive high and low radiogenic Pb from upper to lower parts in the profile, suggesting that these UHP crustal slices were derived from the subducted upper and middle crusts, respectively. Detachment surfaces within the deeply subducted crust may occur either along an ancient fault as a channel of fluid flow, which resulted in weakening of mechanic strength of the rocks adjacent to the fault due to fluid-rock interaction, or along the low-viscosity zones which resulted from variations of geotherms and lithospheric compositions at different depths. The multi-slice successive exhumation model is different from the traditional exhumation model of the UHP metamorphic rocks in that the latter assumes the detachment of the entire subducted continental crust from the underlying mantle lithosphere and its subsequent exhumation as a whole. This also reveals the difference between the continental subduction and oceanic subduction. In addition, several important proposals concerning the multi-slice successive exhumation model are made for further studies.
Baseline-Dependent Responses of Soil Organic Carbon Dynamics to Climate and Land Disturbances
Zhengxi Tan,Shuguang Liu
Applied and Environmental Soil Science , 2013, DOI: 10.1155/2013/206758
Abstract:
Baseline-Dependent Responses of Soil Organic Carbon Dynamics to Climate and Land Disturbances
Zhengxi Tan,Shuguang Liu
Applied and Environmental Soil Science , 2013, DOI: 10.1155/2013/206758
Abstract: Terrestrial carbon (C) sequestration through optimizing land use and management is widely considered a realistic option to mitigate the global greenhouse effect. But how the responses of individual ecosystems to changes in land use and management are related to baseline soil organic C (SOC) levels still needs to be evaluated at various scales. In this study, we modeled SOC dynamics within both natural and managed ecosystems in North Dakota of the United States and found that the average SOC stock in the top 20 cm depth of soil lost at a rate of 450?kg?C?ha?1?yr?1 in cropland and 110?kg?C?ha?1?yr?1 in grassland between 1971 and 1998. Since 1998, the study area had become a SOC sink at a rate of 44?kg?C?ha?1?yr?1. The annual rate of SOC change in all types of lands substantially depends on the magnitude of initial SOC contents, but such dependency varies more with climatic variables within natural ecosystems and with management practices within managed ecosystems. Additionally, soils with high baseline SOC stocks tend to be C sources following any land surface disturbances, whereas soils having low baseline C contents likely become C sinks following conservation management. 1. Introduction Soil carbon (C) dynamics and change rate caused by land surface disturbances and climate change are generally related to the magnitude of initial soil organic C (SOC) [1–10]. These investigators observed a strong negative relationship between the rate of change in SOC and the baseline SOC content, and this relationship has been thought to have no effect on any other soil properties [4]. However, the effect of the baseline SOC content has been neither evaluated under considerations of individual land use and land cover (LULC) types and their temporal change nor counted in the assessment on the potential of terrestrial ecosystem C sequestration through adaptation strategies. To further assess ecosystem-climate system feedback and define a strategy to reduce the buildup of atmospheric greenhouse gases using terrestrial C sequestration as an option, it is necessary to improve our understanding of not only the C biogeochemical cycles associated with LULC dynamics, but also the sensitivity of SOC stock to transient land disturbances and its relation to the baseline SOC level at multiple temporal and spatial scales. And the data obtained from specific sites have to be upscaled to a regional scope through modeling algorithms that can constrain uncertainties derived from local scales. The General Ensemble biogeochemical Modeling System (GEMS) is a new type of multilevel
Optimal Fiscal Policy Instrument under Different Shocks  [PDF]
Shuguang Xing
Theoretical Economics Letters (TEL) , 2017, DOI: 10.4236/tel.2017.76115
Abstract: This paper constructs a New Keynesian model to study optimal tax and government spending rules and compares their welfare. The output gap, inflation and the difference between the output gap and the government spending gap all affect welfare. This paper finds that the optimal fiscal policy instruments under technical shock and cost-push shock are government spending and tax, respectively. If the policymaker is only concerned with the output gap and inflation, the optimal fiscal policy rule and actual social welfare loss will change. However, the optimal fiscal policy instruments under technical shock and cost-push shock are still government spending and tax. This paper also finds that an imperfect financial market affects social welfare but does not change the optimal fiscal policy instrument under different shocks.
Generalized Cut-Set Bounds for Broadcast Networks
Amir Salimi,Tie Liu,Shuguang Cui
Mathematics , 2013,
Abstract: A broadcast network is a classical network with all source messages collocated at a single source node. For broadcast networks, the standard cut-set bounds, which are known to be loose in general, are closely related to union as a specific set operation to combine the basic cuts of the network. This paper provides a new set of network coding bounds for general broadcast networks. These bounds combine the basic cuts of the network via a variety of set operations (not just the union) and are established via only the submodularity of Shannon entropy. The tightness of these bounds are demonstrated via applications to combination networks.
Rapeseed Oil Monoester of Ethylene Glycol Monomethyl Ether as a New Biodiesel
Jiang Dayong,Wang Xuanjun,Liu Shuguang,Guo Hejun
Journal of Biomedicine and Biotechnology , 2011, DOI: 10.1155/2011/293161
Abstract: A novel biodiesel named rapeseed oil monoester of ethylene glycol monomethyl ether is developed. This fuel has one more ester group than the traditional biodiesel. The fuel was synthesized and structurally identified through FT-IR and P1PH NMR analyses. Engine test results show that when a tested diesel engine is fueled with this biodiesel in place of 0# diesel fuel, engine-out smoke emissions can be decreased by 25.0%–75.0%, CO emissions can be reduced by 50.0%, and unburned HC emissions are lessened significantly. However, NOx emissions generally do not change noticeably. In the area of combustion performance, both engine in-cylinder pressure and its changing rate with crankshaft angle are increased to some extent. Rapeseed oil monoester of ethylene glycol monomethyl ether has a much higher cetane number and shorter ignition delay, leading to autoignition 1.1°CA earlier than diesel fuel during engine operation. Because of certain amount of oxygen contained in the new biodiesel, the engine thermal efficiency is improved 13.5%–20.4% when fueled with the biodiesel compared with diesel fuel.
Simulated responses of soil organic carbon stock to tillage management scenarios in the Northwest Great Plains
Zhengxi Tan, Shuguang Liu, Zhengpeng Li, Thomas R Loveland
Carbon Balance and Management , 2007, DOI: 10.1186/1750-0680-2-7
Abstract: Model simulations show that the average amount of C (kg C ha-1yr-1) released from croplands between 1972 and 2000 was 246 with ATM, 261 with CT, and 210 with NT. The reduction in the rate of C emissions with conversion of CT to NT at the ecoregion scale is much smaller than those reported at plot scale and simulated for other regions. Results indicate that the response of SOC to tillage practices depends significantly on baseline SOC levels: the conversion of CT to NT had less influence on SOC stocks in soils having lower baseline SOC levels but would lead to higher potentials to mitigate C release from soils having higher baseline SOC levels.For assessing the potential of agricultural soils to mitigate C emissions with conservation tillage practices, it is critical to consider both the crop rotations being used at a local scale and the composition of all cropping systems at a regional scale.Many studies have identified the potential of soils cultivated with conservation practices (e.g., no-till) to sequester large amounts of carbon (C) [1,2]. It is estimated that conservation tillage practices across the United States may drive large-scale sequestration on the order of 24–40 Tg C yr-1 (Tg: teragram; 1 Tg = 1012 g), and that additional C sequestration of 25–63 Tg C yr-1 can be achieved through other modifications to traditional agricultural practices [3]. In regard to the C credit scenario established by the Kyoto Protocol, it is widely suggested that conversion of conventional tillage (CT) to no-till (NT) can help to support the profitability of C credits for farmers. The uncertainties of these sequestration scenarios, however, depend on soil organic carbon (SOC) monitoring and/or models [2].Recently, eddy-covariance measurements have been used to evaluate the contribution of NT practice to C dynamics in corn (Zea mays L.) and soybean (Glycine max (L.) Merr.) rotation ecosystems at regional and national scales [1,2]. However, the relationships between net ecosystem
Zircon SHRIMP U-Pb dating for olivine gabbro at Wangmuguan in the Beihuaiyang zone and its geological significance
Yican Liu,Shuguang Li,Xiaofeng Gu,Zhenhui Hou
Chinese Science Bulletin , 2006, DOI: 10.1007/s11434-006-2150-9
Abstract: Zircon SHRIMP U-Pb dating was performed for olivine gabbro at Wangmuguan in the Beihuaiyang zone of the Dabie orogen and its country rock (garnet-bearing epidote-mica-quartz schist). The results show that the gabbro was crystallized at 635 ± 5 Ma, in the late Neoproterozoic rather than in the late Paleozoic as previously suggested; its country rocks formed at 464±7 Ma, younger than the enclosed gabbro. The U-Pb age for the gabbro is in good agreement with ages for tuff interbedded with sediments from the Doushantuo Formation in the South China Block and late-Neoproterozoic basic dyke swarms distributed on a large scale over areas of Suizhou to Zaoyang of Hubei Province in the northern margin of the South China Block. This suggests a large-scale magmatic activity occurred at the late Neoproterozoic in the South China Block, so that the gabbro at Wangmuguan in the western segment of the Beihuaiyang zone is geotectonic affinity to the northern margin of the South China Block. Since the olivine gabbro occurs within the schist of Ordovician protolith with tectonic contact between them but forming in different tectonic settings, it is concluded that the late-Neoproterozoic gabbro was detached from the Precambrian basement of the South China Block during the Triassic subduction of the South China Block, and tectonically thrusted over the metamorphosed rocks in the southern margin of the North China Block.
Formation Mechanism of Microstructure of Fe2(MoO4)3/Si3N4 Composite Powder by Hydrogen Reduction

YIN Ruiming,FAN Jinglian,LIU Xun,ZHANG Shuguang,

材料研究学报 , 2010,
Abstract: The microstructure characterization of Fe2(MoO4)3 and Fe2(MoO4)3/Si3N4 composite powder reduced by hydrogen were investigated, and the formation mechanism of the latter was analyzed. The results show that the microstructure of Fe2(MoO4)3 powder particles reduced by hydrogen was consisted by Mo particles coated with thin layer of Fe with thickness around 20 nm. The microstructure of the other were two kinds of particles with different structure which were consisted by Mo particles coated with nanometer-thin layers of Fe with thickness about 3–5 nm and nano Fe–Mo nitride, Si and Mo as adhesive materials on Si3N4 particles surface. The formation reason of the microstructure of Fe2(MoO4)3/Si3N4 composite powder reduced by hydrogen powder was two reactions during the reduction process. One is the decomposition-reduction reaction of Fe2(MoO4)3, the other is the reaction between the surface of Fe2(MoO4)3 and Si3N4.
Softwares and methods for estimating genetic ancestry in human populations
Liu Yushi,Nyunoya Toru,Leng Shuguang,Belinsky Steven A
Human Genomics , 2013, DOI: 10.1186/1479-7364-7-1
Abstract: The estimation of genetic ancestry in human populations has important applications in medical genetic studies. Genetic ancestry is used to control for population stratification in genetic association studies, and is used to understand the genetic basis for ethnic differences in disease susceptibility. In this review, we present an overview of genetic ancestry estimation in human disease studies, followed by a review of popular softwares and methods used for this estimation.
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