High total dissolved solids (TDS) content is one of the most important pollution contributors in lakes in arid and semiarid areas.Ulansuhai Lake,located in Urad Qianqi,Inner Mongolia,China,was selected as the object o...High total dissolved solids (TDS) content is one of the most important pollution contributors in lakes in arid and semiarid areas.Ulansuhai Lake,located in Urad Qianqi,Inner Mongolia,China,was selected as the object of study.Temperatures and TDS contents of both ice and under-ice water were collected together with corresponding ice thickness.TDS profiles were drawn to show the distribution of TDS and to describe TDS migration.The results showed that about 80% (that is 3.602×10 8 kg) of TDS migrated from ice to water during the whole growth period of ice.Within ice layer,TDS migration only occurred during initial ice-on period,and then perished.The TDS in ice decreased with increasing ice thickness,following a negative exponential-like trend.Within under-ice water,the TDS migrated from ice-water interface to the entire water column under the effect of concentration gradient until the water TDS content was uniform.In winter,6.044×10 7 kg (16.78% of total TDS) TDS migrated from water to sediment,which indicated that winter is the best time for dredging sediment.The migration effect gives rise to TDS concentration in under-ice water and sediment that is likely to affect ecosystem and water quality of the Yellow River.The trend of transfer flux of ice-water and water-sediment interfaces is similar to that of ice growth rate,which reveals that ice growth rate is one of the determinants of TDS migration.The process and mechanism of TDS migration can be referenced by research on other lakes with similar TDS content in cold and arid areas.展开更多
Current evidence shows that apolipoprotein E(APOE), apolipoprotein CI(APOC1) and low density lipoprotein receptor-related protein(LRP) variations are related to late-onset Alzheimer's disease. However, it remains ...Current evidence shows that apolipoprotein E(APOE), apolipoprotein CI(APOC1) and low density lipoprotein receptor-related protein(LRP) variations are related to late-onset Alzheimer's disease. However, it remains unclear if genetic polymorphisms in these genes are associated with cognitive decline in late-onset Alzheimer's disease patients. We performed a 30-month longitudinal cohort study to investigate the relationship between Alzheimer's disease and APOE, APOC1, and LRP. In this study, 78 Chinese Han patients with late-onset Alzheimer's disease were recruited form Guangxi Zhuang Autonomous Region in China. APOE, APOC1, and LRP genotyping was performed using polymerase chain reaction-restriction fragment length polymorphisms. The Mini-Mental State Examination and Clinical Dementia Rating Scale were used to assess patients' cognitive function. After a 30-month follow-up period, we found a significant reduction in Mini-Mental State Examination total score, a higher proportion of patients fulfilling cognitive impairment progression criteria, and a higher proportion of APOC1 H2 carriers in APOE ε4 carriers compared with non-carriers. In addition, the APOE ε4 allele frequency was significantly higher in the cognitive impairment progression group compared with the non-cognitive impairment progression group. In conclusion, APOE ε4 plays an important role in augmenting cognitive decline, and APOC1 H2 may act synergistically with APOE ε4 in increasing the risk of cognitive decline in Chinese patients with late-onset Alzheimer's disease.展开更多
Hydraulic fracturing technique is widely used for methane drainage and has achieved good effects in numerous coal mines,but negative effects may occur as the fracturing fluids are absorbed into the coal seam.Gas wetta...Hydraulic fracturing technique is widely used for methane drainage and has achieved good effects in numerous coal mines,but negative effects may occur as the fracturing fluids are absorbed into the coal seam.Gas wettability alteration(GWA)technology can be used as it can enhance the gas and water mobility during dewatering process as a result of capillary pressure change.However,there have been few reported field tests in coal mines using GWA technology.This paper describes a pilot-scale field test in Xinjing coal mine,Yangquan,China.The fluorocarbon surfactants perfluorooctyl methacrylate monomer-containing polymethacrylate(PMP)was used to alter the wettability of coal seam to strong gas-wetness during the hydraulic fracturing process.The study focuses on the comparison of two boreholes(Boreholes#9 and#10)and one other borehole(Borehole#8)with and without using GWA approach.A well-defined monitoring program was established by measuring the dewatering volume of the fracturing fluid and the drainage volume of methane as well as the concentration.The field test results showed that the average methane drainage rates of Boreholes#9(39.28 m^(3)/d)and#10(51.04 m^(3)/d)with GWA treatment exceeded that of Borehole#8(21.09 m^(3)/d)without GWA treatment,with an increase of 86.3%and 142.1%,respectively.The average methane concentrations of Boreholes#9(4.05%)and#10(6.18%)were 64.6%and 151.2%higher than that of Borehole#8(2.46%),respectively.On the other hand,the dewatering ratio of Boreholes#9(4.36%)and#10(3.11%)was almost 19 times and 13 times greater than that of Borehole#8(0.22%).These field test results were in agreement with the experimental data.The significant increase in both methane concentration and dewatering ratio demonstrated that GWA technology could be applied for enhanced methane drainage in coal mines.Important lessons learned at Xinjing coal mine might be applied to other coal mines in China and elsewhere.展开更多
This paper presents a high efficiency spread spectrum scheme using approximate orthogonal complex (AOC) sequences. In this scheme, the 64 AOC sequences picked up from 84 complex sequences space are employed for spread...This paper presents a high efficiency spread spectrum scheme using approximate orthogonal complex (AOC) sequences. In this scheme, the 64 AOC sequences picked up from 84 complex sequences space are employed for spreading spectrum. In modulation, 6 input bits is used to select one AOC sequence, and the selected sequence is then phase-rotated by another 2 input bits. In demodulator, a complex correlator detects the transmitted AOC sequence. Simulation results show that the proposed scheme has better BER performance than the existing complementary code keying (CCK) modulation scheme. For AOC, additional processing gain of 1.79dB can be obtained when the sequence length is 8.展开更多
With the continuous demand of material performance,the development of materials is rapid,and the professional curriculum teaching of“new inorganic materials”as well as its teaching methods related to the internet ma...With the continuous demand of material performance,the development of materials is rapid,and the professional curriculum teaching of“new inorganic materials”as well as its teaching methods related to the internet mandate a reform,in order to meet the needs of innovative high-quality personnel training.The update and optimization of the teaching content and methods assisted by the internet meet the needs of modern teaching and research work.More than 90%of students believe that internet teaching is conducive to the understanding of classroom knowledge and the development of innovative projects.展开更多
To improve the oxidation resistance of carbon/carbon (C/C) composites, mullite coating was prepared on the surface of SiC-coated C/C composites by supersonic plasma spraying. Phases and microstructures of mullite coat...To improve the oxidation resistance of carbon/carbon (C/C) composites, mullite coating was prepared on the surface of SiC-coated C/C composites by supersonic plasma spraying. Phases and microstructures of mullite coating were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The coating primarily consists of a single phase of mullite (3Al2O3-2SiO2). The SEM results show that mullite coating was continuous and well bonded with the SiC inner layer without penetrating crack. Mullite coating exhibited good oxidation resistance. After 98.5 h oxidation at 1773 K and 9 thermal shock cycles between 1773 K and room temperature, the weight loss of the coated C/C composites was only 2.57%.展开更多
How layer-segregated distribution of SiC affects the ablation of C/C-SiC composites was studied in the present work.A certain amount of SiC particles was deposited at the non-woven(C/C—SiC-1) and web(C/C-SiC-2) layer...How layer-segregated distribution of SiC affects the ablation of C/C-SiC composites was studied in the present work.A certain amount of SiC particles was deposited at the non-woven(C/C—SiC-1) and web(C/C-SiC-2) layer of 2D needle-punched carbon fibre fabric reinforced pyrocarbon composites,respectively.Ablation under oxyacetylene torch demonstrated that the two composites have similar ablation rates in heat flux of 2.38 MW/m^2 whereas ablation rates of C/C-SiC-2 were much higher than those of C/C—SiC-1 when heat flux was 4.18 MW/m^2.SiO_2 covered partially the defective surface of both composites in the lower heat flux.The different SiC locations induced distinct defects and then led to the two composites' dissimilar ablation rates in the higher heat flux.展开更多
With the use of Ti/Ni/Cu/Ni multiple foils as interlayer,carbon/carbon(C/C) composite was bonded to Nibased superalloy GH3044 by partial transient liquid-phase bonding technique.The effect of bonding temperature on th...With the use of Ti/Ni/Cu/Ni multiple foils as interlayer,carbon/carbon(C/C) composite was bonded to Nibased superalloy GH3044 by partial transient liquid-phase bonding technique.The effect of bonding temperature on the microstructures and strengths of the joints was investigated.The results showed that gradient structural multiple interlayers composed of ‘‘C–Ti reaction layer/Ti–Ni intermetallic compound layer/Ni–Cu sosoloid/residual Cu layer/Ni-GH3044 diffusion layer'' were formed between C/C composite and GH3044.The shear strength of the C/C composite/GH3044 joint reached the highest value of 26.1 MPa when the bonding temperature was 1,030 °C.In addition,the fracture morphology showed that the fracture mode changed with the increase of bonding temperature.展开更多
SiC nanowires reinforced C/(PyC-SiC)_(n)multilayered matrix composites(SM-CS for short)were prepared by combined with sol-gel and chemical vapor infiltration(CVI)method.Firstly,(PyC-Si OC);multilayered structure was f...SiC nanowires reinforced C/(PyC-SiC)_(n)multilayered matrix composites(SM-CS for short)were prepared by combined with sol-gel and chemical vapor infiltration(CVI)method.Firstly,(PyC-Si OC);multilayered structure was formed by cycles of impregnation and deposition.Then SiOC was transformed into SiC by heat-treatment,and(PyC-SiC)_(n)multilayered structure would be obtained.At the same time,the PyC layer which was designed as the outmost layer could decrease gas supersaturation to form in-situ tubular SiC nanowires on the surface of multilayered structure.The results of three-point bending test showed that the maximum force of SM-CS composites was increased by the number of cycles of the preparation process,which were up to enhanced by 74.38%compared with C/C composite materials.The fracture surface showed that the improvement was due to the multiscale reinforcing system of(PyC-SiC)_(n)multilayered structure and SiC nanowires.Multilayered structure can protect carbon fibers and release stress concentration by induction of cracks.And the mechanical interlocking effect of SiC nanowires could reinforce bonding force of the remaining matrix.展开更多
基金Financial support was provided by the National Natural Science Foundation of China (50569002,50669004 and 51069007)Natural Science Foundation of Inner Mongolia (200711020604)Key Project from Department of Water Resources of Inner Mongolia (20080105)
文摘High total dissolved solids (TDS) content is one of the most important pollution contributors in lakes in arid and semiarid areas.Ulansuhai Lake,located in Urad Qianqi,Inner Mongolia,China,was selected as the object of study.Temperatures and TDS contents of both ice and under-ice water were collected together with corresponding ice thickness.TDS profiles were drawn to show the distribution of TDS and to describe TDS migration.The results showed that about 80% (that is 3.602×10 8 kg) of TDS migrated from ice to water during the whole growth period of ice.Within ice layer,TDS migration only occurred during initial ice-on period,and then perished.The TDS in ice decreased with increasing ice thickness,following a negative exponential-like trend.Within under-ice water,the TDS migrated from ice-water interface to the entire water column under the effect of concentration gradient until the water TDS content was uniform.In winter,6.044×10 7 kg (16.78% of total TDS) TDS migrated from water to sediment,which indicated that winter is the best time for dredging sediment.The migration effect gives rise to TDS concentration in under-ice water and sediment that is likely to affect ecosystem and water quality of the Yellow River.The trend of transfer flux of ice-water and water-sediment interfaces is similar to that of ice growth rate,which reveals that ice growth rate is one of the determinants of TDS migration.The process and mechanism of TDS migration can be referenced by research on other lakes with similar TDS content in cold and arid areas.
基金supported by the National Natural Science Foundation of China,No.81370445,81061120527,81241082Major Funding from Beijing Hospital,No.BJ-2010-30+4 种基金Key Project of Clinical Disciplines at the Subordinate Hospital,Ministry of Health,No.10120101National Department Public Benefit Research Foundation by the Ministry of Health,No.20130200812th 5-year National Program from Ministry of Scientific Technology,No.2012BAI10B01Science and Technology Development Foundation of Guangxi Zhuang Autonomous Region,No.1355005-62Canadian Institute of Health Research(CIHR),No.109606
文摘Current evidence shows that apolipoprotein E(APOE), apolipoprotein CI(APOC1) and low density lipoprotein receptor-related protein(LRP) variations are related to late-onset Alzheimer's disease. However, it remains unclear if genetic polymorphisms in these genes are associated with cognitive decline in late-onset Alzheimer's disease patients. We performed a 30-month longitudinal cohort study to investigate the relationship between Alzheimer's disease and APOE, APOC1, and LRP. In this study, 78 Chinese Han patients with late-onset Alzheimer's disease were recruited form Guangxi Zhuang Autonomous Region in China. APOE, APOC1, and LRP genotyping was performed using polymerase chain reaction-restriction fragment length polymorphisms. The Mini-Mental State Examination and Clinical Dementia Rating Scale were used to assess patients' cognitive function. After a 30-month follow-up period, we found a significant reduction in Mini-Mental State Examination total score, a higher proportion of patients fulfilling cognitive impairment progression criteria, and a higher proportion of APOC1 H2 carriers in APOE ε4 carriers compared with non-carriers. In addition, the APOE ε4 allele frequency was significantly higher in the cognitive impairment progression group compared with the non-cognitive impairment progression group. In conclusion, APOE ε4 plays an important role in augmenting cognitive decline, and APOC1 H2 may act synergistically with APOE ε4 in increasing the risk of cognitive decline in Chinese patients with late-onset Alzheimer's disease.
文摘Hydraulic fracturing technique is widely used for methane drainage and has achieved good effects in numerous coal mines,but negative effects may occur as the fracturing fluids are absorbed into the coal seam.Gas wettability alteration(GWA)technology can be used as it can enhance the gas and water mobility during dewatering process as a result of capillary pressure change.However,there have been few reported field tests in coal mines using GWA technology.This paper describes a pilot-scale field test in Xinjing coal mine,Yangquan,China.The fluorocarbon surfactants perfluorooctyl methacrylate monomer-containing polymethacrylate(PMP)was used to alter the wettability of coal seam to strong gas-wetness during the hydraulic fracturing process.The study focuses on the comparison of two boreholes(Boreholes#9 and#10)and one other borehole(Borehole#8)with and without using GWA approach.A well-defined monitoring program was established by measuring the dewatering volume of the fracturing fluid and the drainage volume of methane as well as the concentration.The field test results showed that the average methane drainage rates of Boreholes#9(39.28 m^(3)/d)and#10(51.04 m^(3)/d)with GWA treatment exceeded that of Borehole#8(21.09 m^(3)/d)without GWA treatment,with an increase of 86.3%and 142.1%,respectively.The average methane concentrations of Boreholes#9(4.05%)and#10(6.18%)were 64.6%and 151.2%higher than that of Borehole#8(2.46%),respectively.On the other hand,the dewatering ratio of Boreholes#9(4.36%)and#10(3.11%)was almost 19 times and 13 times greater than that of Borehole#8(0.22%).These field test results were in agreement with the experimental data.The significant increase in both methane concentration and dewatering ratio demonstrated that GWA technology could be applied for enhanced methane drainage in coal mines.Important lessons learned at Xinjing coal mine might be applied to other coal mines in China and elsewhere.
文摘This paper presents a high efficiency spread spectrum scheme using approximate orthogonal complex (AOC) sequences. In this scheme, the 64 AOC sequences picked up from 84 complex sequences space are employed for spreading spectrum. In modulation, 6 input bits is used to select one AOC sequence, and the selected sequence is then phase-rotated by another 2 input bits. In demodulator, a complex correlator detects the transmitted AOC sequence. Simulation results show that the proposed scheme has better BER performance than the existing complementary code keying (CCK) modulation scheme. For AOC, additional processing gain of 1.79dB can be obtained when the sequence length is 8.
基金the National Natural Science Foundations of China(Grant Number:51772247).
文摘With the continuous demand of material performance,the development of materials is rapid,and the professional curriculum teaching of“new inorganic materials”as well as its teaching methods related to the internet mandate a reform,in order to meet the needs of innovative high-quality personnel training.The update and optimization of the teaching content and methods assisted by the internet meet the needs of modern teaching and research work.More than 90%of students believe that internet teaching is conducive to the understanding of classroom knowledge and the development of innovative projects.
基金supported by the National Natural Science Foundation of China under Grant No. 51072166 and No.50902111the "111" Project under Grant No.D08040NPU Foundation for Fundamental Research and the Research Fund of the State Key Laboratory of Solidification Processing(NWPU), China (Grant No.73-QP-2010)
文摘To improve the oxidation resistance of carbon/carbon (C/C) composites, mullite coating was prepared on the surface of SiC-coated C/C composites by supersonic plasma spraying. Phases and microstructures of mullite coating were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The coating primarily consists of a single phase of mullite (3Al2O3-2SiO2). The SEM results show that mullite coating was continuous and well bonded with the SiC inner layer without penetrating crack. Mullite coating exhibited good oxidation resistance. After 98.5 h oxidation at 1773 K and 9 thermal shock cycles between 1773 K and room temperature, the weight loss of the coated C/C composites was only 2.57%.
基金supported by the National Natural Science Foundation of China under Grant No.51402238 and 51221001the Fundamental Research Foundation of Northwestern Polytechnical University under Grant No.GBKY1021+1 种基金the Research Fund of State Key Laboratory of Solidification Processing(NWPU),China(Grant No.25-TZ-2009)the"111"Project under Grant No.B08040
文摘How layer-segregated distribution of SiC affects the ablation of C/C-SiC composites was studied in the present work.A certain amount of SiC particles was deposited at the non-woven(C/C—SiC-1) and web(C/C-SiC-2) layer of 2D needle-punched carbon fibre fabric reinforced pyrocarbon composites,respectively.Ablation under oxyacetylene torch demonstrated that the two composites have similar ablation rates in heat flux of 2.38 MW/m^2 whereas ablation rates of C/C-SiC-2 were much higher than those of C/C—SiC-1 when heat flux was 4.18 MW/m^2.SiO_2 covered partially the defective surface of both composites in the lower heat flux.The different SiC locations induced distinct defects and then led to the two composites' dissimilar ablation rates in the higher heat flux.
基金financially supported by the National Natural Science Foundation of China(Nos.51202193 and 51221001)the Fundamental Research Foundation of Northwestern Polytechnical University(No.GBKY1021)the‘‘111’’Project(No.08040)
文摘With the use of Ti/Ni/Cu/Ni multiple foils as interlayer,carbon/carbon(C/C) composite was bonded to Nibased superalloy GH3044 by partial transient liquid-phase bonding technique.The effect of bonding temperature on the microstructures and strengths of the joints was investigated.The results showed that gradient structural multiple interlayers composed of ‘‘C–Ti reaction layer/Ti–Ni intermetallic compound layer/Ni–Cu sosoloid/residual Cu layer/Ni-GH3044 diffusion layer'' were formed between C/C composite and GH3044.The shear strength of the C/C composite/GH3044 joint reached the highest value of 26.1 MPa when the bonding temperature was 1,030 °C.In addition,the fracture morphology showed that the fracture mode changed with the increase of bonding temperature.
基金supported by the National Natural Science Foundation of China(Nos.51772247 and 5172780072)the Creative Research Foundation of Science and Technology on Thermostructural Composite Materials Laboratory(No.6142911050217)the Natural Science Basic Research Plan in Shaanxi Province of China(No.2017JM5098)。
文摘SiC nanowires reinforced C/(PyC-SiC)_(n)multilayered matrix composites(SM-CS for short)were prepared by combined with sol-gel and chemical vapor infiltration(CVI)method.Firstly,(PyC-Si OC);multilayered structure was formed by cycles of impregnation and deposition.Then SiOC was transformed into SiC by heat-treatment,and(PyC-SiC)_(n)multilayered structure would be obtained.At the same time,the PyC layer which was designed as the outmost layer could decrease gas supersaturation to form in-situ tubular SiC nanowires on the surface of multilayered structure.The results of three-point bending test showed that the maximum force of SM-CS composites was increased by the number of cycles of the preparation process,which were up to enhanced by 74.38%compared with C/C composite materials.The fracture surface showed that the improvement was due to the multiscale reinforcing system of(PyC-SiC)_(n)multilayered structure and SiC nanowires.Multilayered structure can protect carbon fibers and release stress concentration by induction of cracks.And the mechanical interlocking effect of SiC nanowires could reinforce bonding force of the remaining matrix.