Seismic attenuation is a fundamental property of the Earth's media.Attenuation structure for the complicated geological structures with strong seismicity in the Sichuan-Yunnan region is poorly studied.In this stud...Seismic attenuation is a fundamental property of the Earth's media.Attenuation structure for the complicated geological structures with strong seismicity in the Sichuan-Yunnan region is poorly studied.In this study,we collected 108,399 waveforms of 11,517 local small earthquakes with magnitudes between 1.5 and 3.5 from January 2014 to September 2021 in the Sichuan-Yunnan region and its adjacent areas.We employed an envelope inversion technique for separating the intrinsic and scattering attenuations of the S coda wave,and obtained the intrinsic and scattering attenuation structures for frequencies between 0.25 and 8.00 Hz.The attenuation structures correlate well with the geological units,and some major faults mark the attenuation variations where historic large earthquakes have occurred.The regional average attenuation shows a negative frequency dependence.The average scattering attenuation has a faster descending rate than the average intrinsic attenuation,and is dominant at low frequencies,while at high frequencies the average intrinsic attenuation is stronger.The lateral variation in the intrinsic attenuation is consistent with the variation in heat flow,the scattering attenuation may be related to the scatter distribution and size.The total attenuation is consistent with the previous studies in this region,and the separate intrinsic and scattering attenuation may be useful in understanding regional tectonics and important in earthquake prevention and disaster reduction.展开更多
The ultramafic dikes in the Tarim large igneous province（Tarim LIP）, exposed in the Xiaohaizi area in the northwestern Tarim Basin of northwestern China, have porphyritic textures, and the olivine and clinopyroxene ...The ultramafic dikes in the Tarim large igneous province（Tarim LIP）, exposed in the Xiaohaizi area in the northwestern Tarim Basin of northwestern China, have porphyritic textures, and the olivine and clinopyroxene are as the major phenocryst phases. The groundmass therein consists of clinopyroxene, plagioclase and Fe-Ti oxides, with the cryptocrystalline texture. The olivine phenocrysts in one typical ultramafic dike have Fo（Mg/（Mg＋Fe）） numbers ranging from 73 to 85, which are not in equilibrium with the olivine（Mg# of 89） from the host rock crystalized. Combined with microscope observation, both the olivine and clinopyroxene phenocrysts as well as some Fe-Ti oxides in the ultramafic rock are accounted as cumulates. The liquid（parental magma） composition of SiO2 of 45.00 wt.%–48.82 wt.%, MgO of 9.93 wt.%– 18.56 wt.%, FeO of 5.85 wt.%–14.17 wt.%, CaO of 7.54 wt.%–11.52 wt.%, Al2O3 of 8.70 wt.%–11.62 wt.% and TiO2 of 0.00 wt.%–3.43 wt.% in the Xiaohaizi ultramafic rock was estimated by mass balance, and the results show a reasonable liquid proportion in the cumulate-bearing ultramafic dike（ca. 45%–60% in the whole rock）. The estimated parental magma composition corresponds to a melting temperature of 1 300–1 550 oC, which is equal or higher than those of a normal asthenosphere mantle, supporting the involvement of a mantle plume. Combined with other previous studies, an evolution model for the formation processes of the Xiaohaizi ultramafic dike of the Tarim LIP is proposed.展开更多
In the northwest of the Himalayan-Tibetan Orogen, the ~250 km-long Kongur Shan extensional system in the eastern Pamir was formed during the convergence between the Indian and Asian plates. Tectonic activity of the Ko...In the northwest of the Himalayan-Tibetan Orogen, the ~250 km-long Kongur Shan extensional system in the eastern Pamir was formed during the convergence between the Indian and Asian plates. Tectonic activity of the Kongur Shan normal fault and the Tashkurgan normal fault can help to reveal the origin of east-west extension along the Kongur Shan extensional system. The Kongur Shan fault has been extensively studied, while the Tashkurgan fault calls for systemic research. In this study, low-temperature thermochronology including apatite fission track analysis and apatite and zircon(U-Th)/He analyses is applied to constrain the timing of activity of the Tashkurgan fault. Results indicate that the Tashkurgan fault initiated at 10–5 Ma, and most likely at 6–5 Ma. The footwall of the Tashkurgan fault has been exhumed at an average exhumation rate of 0.6–0.9 mm/a since the initiation of the Tashkurgan fault. Combined with previous research on the Kongur Shan fault, we believe that the origin of east-west extension along the Kongur Shan extensional system was driven by gravitational collapse of over-thickened Pamir crust.展开更多
This study employed microwave-assisted hydrothermal method to synthesize Ti-MCM-41,which are mesoporous materials with a high surface area and excellent photocatalytic ability. Fourier transform infrared spectroscopy...This study employed microwave-assisted hydrothermal method to synthesize Ti-MCM-41,which are mesoporous materials with a high surface area and excellent photocatalytic ability. Fourier transform infrared spectroscopy（FTIR）, X-ray diffraction（XRD）, X-ray photoelectron spectroscopy（XPS）, transmission electron microscopy（TEM）, and ultraviolet–visible spectroscopy（UV–Vis） were employed. The XRD findings showed that Ti-MCM-41 exhibited a peak at 2θ of 2.2°, which was attributed to the hexagonal MCM-41 structure. The BET（Brunauer–Emmett–Teller） results agreed with the TEM findings that Ti-MCM-41 has a pore size of about 3–5 nm and a high surface area of 883 m-2/g. FTIR results illustrated the existence of Si–O–Si and Si–O–Ti bonds in Ti-MCM-41. The appearance of Ti2 p peaks in the XPS results confirmed the FTIR findings that the Ti was successfully doped into the MCM-41 structure. Zeta（ζ）-potential results indicated that the iso-electric point（IEP） of Ti-MCM-41 was at about pH 3.02. In this study, the photocatalytic degradation of oxytetracycline（OTC） at different pH was investigated under Hg lamp irradiation（wavelength 365 nm）. The rate constant（K′obs） for OTC degradation was 0.012 min-1at pH 3. Furthermore, TOC（total organic carbon） and high resolution LC–MS（liquid chromatography–mass spectrometry） analyses were conducted to elucidate the possible intermediate products and degradation pathway for OTC. The TOC removal efficiency of OTC degradation was 87.0%, 74.4% and 50.9% at pH 3, 7 and 10, respectively. LC–MS analysis results showed that the degradation products from OTC resulted from the removal of functional groups from the OTC ring.展开更多
In the paper, the homoclinic (hateroclinic) breather limit method (HBLM) is applied to seek rogue wave solution of the Benjamin Ono equation. We find that the rational breather wave solution is just a rogue wave solut...In the paper, the homoclinic (hateroclinic) breather limit method (HBLM) is applied to seek rogue wave solution of the Benjamin Ono equation. We find that the rational breather wave solution is just a rogue wave solution. This result shows that rogue wave can come from the extreme behavior of the breather solitary wave for (1+1)-dimensional nonlinear wave fields.展开更多
With the complexity and uncertainty of mobile communication network environment, solving the classical mathematical analysis also becomes more complicated. The model tree of basis function method based on Fourier seri...With the complexity and uncertainty of mobile communication network environment, solving the classical mathematical analysis also becomes more complicated. The model tree of basis function method based on Fourier series is proposed in this paper. Model tree method is the improvement of regression tree analysis. Basis function applied here is four-order Fourier series. When the Fourier coefficients are calculated, the Gauss elimination method is implemented for solving equations. The complexity of the algorithm is n3log(n).展开更多
Ceria is widely used as a catalyst for soot combustion,but effects of Zr substitution on the reaction mechanism is ambiguous.The present work elucidates effects of Zr substitution on soot combustion over cubic fluorit...Ceria is widely used as a catalyst for soot combustion,but effects of Zr substitution on the reaction mechanism is ambiguous.The present work elucidates effects of Zr substitution on soot combustion over cubic fluorite-structured nanoceria.The nanostructured CeO_(2),Ce_(0.92)Zr_(0.08)O_(2),and Ce_(0.84)Zr_(0.16)O_(2)composed of 5-6 nm crystallites display T_(m-CO2)(the temperature at maximum CO_2 yield)at 383,355,and 375℃under 10 vol.%O_(2)/N_(2),respectively.The size of agglomerate decreases from 165.5 to 51.9-57.3 nm,which is beneficial for the sootceria contact.Moreover,Zr increases the amount of surface oxygen vacancies,generating more active oxygen(O_(2)^-and O^(-))for soot oxidation.Thus,the activities of Ce_(0.92)Zr_(0.08)O_(2)and Ce_(0.84)Zr_(0.16)O_(2)in soot combustion are better than that of CeO_(2).Although oxygen vacancies promote the migration of lattice O~(2-),the enriched surface Zr also inhibits the mobility of lattice O^(2-).Therefore,the T_(m-CO2)of Ce_(0.84)Zr_(0.1)6 O_(2)is higher than that of Ce_(0.92)Zr_(0.08)O_(2).Based on reaction kinetic study,soot in direct contact with ceria preferentially decomposes with low activation energy,while the oxidation of isolated soot occurs through diffusion with high activation energy.The obtained findings provide new understanding on the soot combustion over nanoceria.展开更多
The change of channel is caused by Doppler effect, and the degree of change is related to relative velocity in the condition of the certain carrier frequency. The multipath fading channel is independent of each other,...The change of channel is caused by Doppler effect, and the degree of change is related to relative velocity in the condition of the certain carrier frequency. The multipath fading channel is independent of each other, whose amplitude obeys Rayleigh distribution and the phase obeys uniform distribution. The model of multipath time-varying transmission channel is built. Through the pro-cess of channel model building, the simulation results produced by the channel model verify the effect of the proposed model in the aspect of reducing test data. In a communication system, signal passing through the channel is involved with the process of digital modulation and demodulation. Binary sequence signal is modulated into a complex sequence in the process of modulation before the transmission in the channel, in order to accommodate the wireless channel transmission. With the increase of SNR, BER is overall slightly drops. However there exists violent fluctuation and it presents the random variation of details in the multipath channel. I employ the mathematical model of multipath time-varying channel, i.e. Jakes model to be simulated so as to compare with the AGWN channel in the same situation. Jakes model has the characteristics of the reference chan-nel compared with the AGWN. BER does not change with the increase of SNR significantly and coincides with multipath time-varying channel. The BER considerably decreases with the increase of SNR in the AGWN channel.展开更多
In this paper, by using bilinear form and extended three-wave type of ans¨atz approach, we obtain new cross-kink multi-soliton solutions of the (3+1)-dimensional Jimbo-Miwa equation, including the periodic breath...In this paper, by using bilinear form and extended three-wave type of ans¨atz approach, we obtain new cross-kink multi-soliton solutions of the (3+1)-dimensional Jimbo-Miwa equation, including the periodic breather-type of kink three-soliton solutions, the cross-kink four-soliton solutions, the doubly periodic breathertype of soliton solutions and the doubly periodic breather-type of cross-kink two-soliton solutions. It is shown that the generalized three-wave method, with the help of symbolic computation, provides an effective and powerful mathematical tool for solving high dimensional nonlinear evolution equations in mathematical physics.展开更多
In response to the limitations of the traditional education and teaching model,this article proposes a smart education model based on ChatGPT.The model actively breaks the constraint of time and space and the design p...In response to the limitations of the traditional education and teaching model,this article proposes a smart education model based on ChatGPT.The model actively breaks the constraint of time and space and the design patterns of traditional education,providing smart education services including personalized learning,smart tutoring and evaluation,educational content creation support,and education big data analysis.Through constructing an open and inclusive learning space and creating flexible and diverse educational models,ChatGPT can help to meet students’individuality and overall development,as well as assist teachers in keeping up with the students’learning performance and developmental requirements in real-time.This provides an important basis for optimizing teaching content,offering personalized and accurate cultivation,and planning the development path of students.展开更多
The northeasternmost active deformation front of the Tibetan Plateau is defined by the North Qilian Shan and the Jiuquan Basin,located~1,500 km away from the India-Asia collision zone.Understanding the lithospheric-sc...The northeasternmost active deformation front of the Tibetan Plateau is defined by the North Qilian Shan and the Jiuquan Basin,located~1,500 km away from the India-Asia collision zone.Understanding the lithospheric-scale convergence between these units is critical for deciphering the mechanisms driving the northeastward plateau expansion.In this study,we conduct systematic geometric and kinematic analysis of upper-crustal deformation across the northern margin of the North Qilian Shan and the Jiuquan Basin,by integrating multiple datasets including high-resolution seismic reflection data,borehole loggings,surface geology and deformed fluvial terraces.Our results indicated that this region is dominated by NE-directed,thick-skinned,basement-involved reverse faults that root into a gently south-dipping(~10°)décollement at~13-15 km depth,likely within the brittle-ductile transition zone.Wedge-shaped foreland basin deposits in the Middle-Late Miocene Shulehe Formation indicate that uplift of the North Qilian Shan initiated during this time.Palinspastic reconstruction reveals that the upper-crustal shortening is limited to 7.6-11.7 km,with up to 54%-95%accommodated by the frontal thrusts of the North Qilian Shan.These observations indicate that North Qilian Shan has acted as a stable plateau margin since the Middle Miocene,with limited northeastward propagation of deformation into the Jiuquan Basin.Reinterpretation of previously published deep geophysical data identifies a north-dipping lithospheric-scale fault offsetting the Moho by~7.8 km.Collectively,our results support a lithospheric-scale tectonic wedge model along the northeastern margin of the Tibetan Plateau,in which the rigid Jiuquan Basin indents into the weakened North Qilian lower crust under horizontal compression,accommodating limited convergence without large-scale subduction.Our findings suggest that northeastward plateau growth occurs through lithospheric wedging of mechanically distinct tectonic units characterized by distributed deformation,rather than by intracontinental subduction localized along a discrete subduction zone.展开更多
The Pamir region, located to the northwest of the Tibetan Plateau, provides important information that can aid the understanding of the plateau＇s tectonic evolution. Here we present new findings on the deforma- tion ...The Pamir region, located to the northwest of the Tibetan Plateau, provides important information that can aid the understanding of the plateau＇s tectonic evolution. Here we present new findings on the deforma- tion geometry and timing of the Wupoer thrust belt at the northeastem margin of Pamir. Field investigations and interpretations of seismic profiles indicate that the eastern portion of the Wupoer thrust belt is dominated by an underlying foreland basin and an overlying piggy-back basin. A regional unconformity occurs between the Pliocene （N2） and the underlying Miocene （NI） or Paleogene （Pg） strata associated with two other local unconformities between Lower Pleistocene （Q1） and N2 and between Middle Pleistocene （Q2-4） and Q1 strata. Results of structural restorations suggest that compres- sional deformation was initiated during the latest Miocene to earliest Pliocene, contributing a total shortening magnitude of 48.6 km with a total shortening rate of 48.12%, most of which occurred in the period from the latest Miocene to earliest Pliocene. These results, com- bined with previous studies on the Kongur and Tarshkor- gan extensional system, suggest an interesting picture of strong piedmont compressional thrusting activity concur- rent with interorogen extensional rifting. Combining these results with previously published work on the lithospheric architecture of the Pamir, we propose that gravitational collapse drove the formation of simultaneous extensional and compressional structures with a weak, ductile middle crustal layer acting as a decollement along which both the extensional and compressional faults merged.展开更多
The global rise in sea level during the Late Cretaceous has been an issue under discussion by the international geological community. Despite the signifi- cance, its impact on the deposition of continental basins is n...The global rise in sea level during the Late Cretaceous has been an issue under discussion by the international geological community. Despite the signifi- cance, its impact on the deposition of continental basins is not well known. This paper presents the systematic review on stratigraphy and sedimentary facies compiled from 22 continental basins in northern Africa. The results indicate that the region was dominated by sediments of continental facies during Early Cretaceous, which were replaced by deposits of marine facies in Late Cretaceous. The spatio- temporal distribution of sedimentary facies suggests marine facies deposition reached as far south as Taou- deni-Iullemmeden-Chad-A1 Kufra-Upper Egypt basins during Turonian to Campanian. These results indicate that northern Africa underwent significant transgression during Late Cretaceous reaching its peak during Turonian to Coniacian. This significant transgression has been attributed to the global high sea-level during this time. Previous studies show that global rise in sea level in Late Cretaceous may have been driven by an increase in the volume of ocean water （attributed to high C02 concentra- tion and subsequently warm climate） and a decrease in the volume of the ocean basin （attributed to rapid production of oceanic crust and seamounts）. Tectonic mechanism of rapid production of oceanic crust and seamounts could play a fimdamental role in driving the global rise in sea level and subsequent transgression in northern Africa during Late Cretaceous.展开更多
基金supported by the Fundamental Research Funds for the Institute of Earthquake Forecas-ting,China Earthquake Administration(No.2021IEF0603)the Special Fund of the Institute of Geophysics,China Earthquake Administration(No.DQJB21B32).
文摘Seismic attenuation is a fundamental property of the Earth's media.Attenuation structure for the complicated geological structures with strong seismicity in the Sichuan-Yunnan region is poorly studied.In this study,we collected 108,399 waveforms of 11,517 local small earthquakes with magnitudes between 1.5 and 3.5 from January 2014 to September 2021 in the Sichuan-Yunnan region and its adjacent areas.We employed an envelope inversion technique for separating the intrinsic and scattering attenuations of the S coda wave,and obtained the intrinsic and scattering attenuation structures for frequencies between 0.25 and 8.00 Hz.The attenuation structures correlate well with the geological units,and some major faults mark the attenuation variations where historic large earthquakes have occurred.The regional average attenuation shows a negative frequency dependence.The average scattering attenuation has a faster descending rate than the average intrinsic attenuation,and is dominant at low frequencies,while at high frequencies the average intrinsic attenuation is stronger.The lateral variation in the intrinsic attenuation is consistent with the variation in heat flow,the scattering attenuation may be related to the scatter distribution and size.The total attenuation is consistent with the previous studies in this region,and the separate intrinsic and scattering attenuation may be useful in understanding regional tectonics and important in earthquake prevention and disaster reduction.
基金funded by the National Basic Research of China (Nos. 2011CB808902 and 2007CB411303)the National Natural Science Foundation of China (Nos. 41541018, 40930315 and 41072048)+1 种基金the Doctoral Program of Higher Education of China (No. 20110101110001)the State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, CAS (No. 201208)
文摘The ultramafic dikes in the Tarim large igneous province（Tarim LIP）, exposed in the Xiaohaizi area in the northwestern Tarim Basin of northwestern China, have porphyritic textures, and the olivine and clinopyroxene are as the major phenocryst phases. The groundmass therein consists of clinopyroxene, plagioclase and Fe-Ti oxides, with the cryptocrystalline texture. The olivine phenocrysts in one typical ultramafic dike have Fo（Mg/（Mg＋Fe）） numbers ranging from 73 to 85, which are not in equilibrium with the olivine（Mg# of 89） from the host rock crystalized. Combined with microscope observation, both the olivine and clinopyroxene phenocrysts as well as some Fe-Ti oxides in the ultramafic rock are accounted as cumulates. The liquid（parental magma） composition of SiO2 of 45.00 wt.%–48.82 wt.%, MgO of 9.93 wt.%– 18.56 wt.%, FeO of 5.85 wt.%–14.17 wt.%, CaO of 7.54 wt.%–11.52 wt.%, Al2O3 of 8.70 wt.%–11.62 wt.% and TiO2 of 0.00 wt.%–3.43 wt.% in the Xiaohaizi ultramafic rock was estimated by mass balance, and the results show a reasonable liquid proportion in the cumulate-bearing ultramafic dike（ca. 45%–60% in the whole rock）. The estimated parental magma composition corresponds to a melting temperature of 1 300–1 550 oC, which is equal or higher than those of a normal asthenosphere mantle, supporting the involvement of a mantle plume. Combined with other previous studies, an evolution model for the formation processes of the Xiaohaizi ultramafic dike of the Tarim LIP is proposed.
基金funded by the National Natural Science Foundation of China (Nos. 41720104003 and 41330207)the National Science and Technology Major Project of China (Nos. 2017ZX05008-001 and 2016ZX05003-001)Chen S Q receives a PhD grant (No. 201706320352) from the China Scholarship Council。
文摘In the northwest of the Himalayan-Tibetan Orogen, the ~250 km-long Kongur Shan extensional system in the eastern Pamir was formed during the convergence between the Indian and Asian plates. Tectonic activity of the Kongur Shan normal fault and the Tashkurgan normal fault can help to reveal the origin of east-west extension along the Kongur Shan extensional system. The Kongur Shan fault has been extensively studied, while the Tashkurgan fault calls for systemic research. In this study, low-temperature thermochronology including apatite fission track analysis and apatite and zircon(U-Th)/He analyses is applied to constrain the timing of activity of the Tashkurgan fault. Results indicate that the Tashkurgan fault initiated at 10–5 Ma, and most likely at 6–5 Ma. The footwall of the Tashkurgan fault has been exhumed at an average exhumation rate of 0.6–0.9 mm/a since the initiation of the Tashkurgan fault. Combined with previous research on the Kongur Shan fault, we believe that the origin of east-west extension along the Kongur Shan extensional system was driven by gravitational collapse of over-thickened Pamir crust.
基金financial support provided by the Tunghai University Global Research and Education on Environment and Society (No. 103GREEnS 005-2)
文摘This study employed microwave-assisted hydrothermal method to synthesize Ti-MCM-41,which are mesoporous materials with a high surface area and excellent photocatalytic ability. Fourier transform infrared spectroscopy（FTIR）, X-ray diffraction（XRD）, X-ray photoelectron spectroscopy（XPS）, transmission electron microscopy（TEM）, and ultraviolet–visible spectroscopy（UV–Vis） were employed. The XRD findings showed that Ti-MCM-41 exhibited a peak at 2θ of 2.2°, which was attributed to the hexagonal MCM-41 structure. The BET（Brunauer–Emmett–Teller） results agreed with the TEM findings that Ti-MCM-41 has a pore size of about 3–5 nm and a high surface area of 883 m-2/g. FTIR results illustrated the existence of Si–O–Si and Si–O–Ti bonds in Ti-MCM-41. The appearance of Ti2 p peaks in the XPS results confirmed the FTIR findings that the Ti was successfully doped into the MCM-41 structure. Zeta（ζ）-potential results indicated that the iso-electric point（IEP） of Ti-MCM-41 was at about pH 3.02. In this study, the photocatalytic degradation of oxytetracycline（OTC） at different pH was investigated under Hg lamp irradiation（wavelength 365 nm）. The rate constant（K′obs） for OTC degradation was 0.012 min-1at pH 3. Furthermore, TOC（total organic carbon） and high resolution LC–MS（liquid chromatography–mass spectrometry） analyses were conducted to elucidate the possible intermediate products and degradation pathway for OTC. The TOC removal efficiency of OTC degradation was 87.0%, 74.4% and 50.9% at pH 3, 7 and 10, respectively. LC–MS analysis results showed that the degradation products from OTC resulted from the removal of functional groups from the OTC ring.
文摘In the paper, the homoclinic (hateroclinic) breather limit method (HBLM) is applied to seek rogue wave solution of the Benjamin Ono equation. We find that the rational breather wave solution is just a rogue wave solution. This result shows that rogue wave can come from the extreme behavior of the breather solitary wave for (1+1)-dimensional nonlinear wave fields.
文摘With the complexity and uncertainty of mobile communication network environment, solving the classical mathematical analysis also becomes more complicated. The model tree of basis function method based on Fourier series is proposed in this paper. Model tree method is the improvement of regression tree analysis. Basis function applied here is four-order Fourier series. When the Fourier coefficients are calculated, the Gauss elimination method is implemented for solving equations. The complexity of the algorithm is n3log(n).
基金financially supported by Guangdong Major Project of Basic and Applied Basic Research(No.2019B030302013)the Natural Science Foundation for Distinguished Young Scientists of Guangdong Province(No.2020B1515020015)+1 种基金Pearl River S&T Nova Program of Guangzhou(No.201806010069)。
文摘Ceria is widely used as a catalyst for soot combustion,but effects of Zr substitution on the reaction mechanism is ambiguous.The present work elucidates effects of Zr substitution on soot combustion over cubic fluorite-structured nanoceria.The nanostructured CeO_(2),Ce_(0.92)Zr_(0.08)O_(2),and Ce_(0.84)Zr_(0.16)O_(2)composed of 5-6 nm crystallites display T_(m-CO2)(the temperature at maximum CO_2 yield)at 383,355,and 375℃under 10 vol.%O_(2)/N_(2),respectively.The size of agglomerate decreases from 165.5 to 51.9-57.3 nm,which is beneficial for the sootceria contact.Moreover,Zr increases the amount of surface oxygen vacancies,generating more active oxygen(O_(2)^-and O^(-))for soot oxidation.Thus,the activities of Ce_(0.92)Zr_(0.08)O_(2)and Ce_(0.84)Zr_(0.16)O_(2)in soot combustion are better than that of CeO_(2).Although oxygen vacancies promote the migration of lattice O~(2-),the enriched surface Zr also inhibits the mobility of lattice O^(2-).Therefore,the T_(m-CO2)of Ce_(0.84)Zr_(0.1)6 O_(2)is higher than that of Ce_(0.92)Zr_(0.08)O_(2).Based on reaction kinetic study,soot in direct contact with ceria preferentially decomposes with low activation energy,while the oxidation of isolated soot occurs through diffusion with high activation energy.The obtained findings provide new understanding on the soot combustion over nanoceria.
文摘The change of channel is caused by Doppler effect, and the degree of change is related to relative velocity in the condition of the certain carrier frequency. The multipath fading channel is independent of each other, whose amplitude obeys Rayleigh distribution and the phase obeys uniform distribution. The model of multipath time-varying transmission channel is built. Through the pro-cess of channel model building, the simulation results produced by the channel model verify the effect of the proposed model in the aspect of reducing test data. In a communication system, signal passing through the channel is involved with the process of digital modulation and demodulation. Binary sequence signal is modulated into a complex sequence in the process of modulation before the transmission in the channel, in order to accommodate the wireless channel transmission. With the increase of SNR, BER is overall slightly drops. However there exists violent fluctuation and it presents the random variation of details in the multipath channel. I employ the mathematical model of multipath time-varying channel, i.e. Jakes model to be simulated so as to compare with the AGWN channel in the same situation. Jakes model has the characteristics of the reference chan-nel compared with the AGWN. BER does not change with the increase of SNR significantly and coincides with multipath time-varying channel. The BER considerably decreases with the increase of SNR in the AGWN channel.
文摘In this paper, by using bilinear form and extended three-wave type of ans¨atz approach, we obtain new cross-kink multi-soliton solutions of the (3+1)-dimensional Jimbo-Miwa equation, including the periodic breather-type of kink three-soliton solutions, the cross-kink four-soliton solutions, the doubly periodic breathertype of soliton solutions and the doubly periodic breather-type of cross-kink two-soliton solutions. It is shown that the generalized three-wave method, with the help of symbolic computation, provides an effective and powerful mathematical tool for solving high dimensional nonlinear evolution equations in mathematical physics.
基金Ministry of Education of New Engineering Project Research and Practice(No.E-AQGABQ20202704)Undergraduate Teaching Reform and Innovation Project of Beijing Higher Education(No.202110018002)+3 种基金First-Class Discipline Construction Project of Beijing Electronic Science and Technology Institute(No.20210064Z0401,No.20210056Z0402)Fundamental Research Funds for the Central Universities(No.328202205,No.328202271,No.328202269)Research on Graphical Development Platform of Reconfigurable Cryptographic Chip Based on Model Driven(No.20220153Z0114)National Key Research and Development Program Funded Project(No.2017YFB0801803)。
文摘In response to the limitations of the traditional education and teaching model,this article proposes a smart education model based on ChatGPT.The model actively breaks the constraint of time and space and the design patterns of traditional education,providing smart education services including personalized learning,smart tutoring and evaluation,educational content creation support,and education big data analysis.Through constructing an open and inclusive learning space and creating flexible and diverse educational models,ChatGPT can help to meet students’individuality and overall development,as well as assist teachers in keeping up with the students’learning performance and developmental requirements in real-time.This provides an important basis for optimizing teaching content,offering personalized and accurate cultivation,and planning the development path of students.
基金supported by the National Natural Science Foundation of China(Grant Nos.U22B6002,42272233)。
文摘The northeasternmost active deformation front of the Tibetan Plateau is defined by the North Qilian Shan and the Jiuquan Basin,located~1,500 km away from the India-Asia collision zone.Understanding the lithospheric-scale convergence between these units is critical for deciphering the mechanisms driving the northeastward plateau expansion.In this study,we conduct systematic geometric and kinematic analysis of upper-crustal deformation across the northern margin of the North Qilian Shan and the Jiuquan Basin,by integrating multiple datasets including high-resolution seismic reflection data,borehole loggings,surface geology and deformed fluvial terraces.Our results indicated that this region is dominated by NE-directed,thick-skinned,basement-involved reverse faults that root into a gently south-dipping(~10°)décollement at~13-15 km depth,likely within the brittle-ductile transition zone.Wedge-shaped foreland basin deposits in the Middle-Late Miocene Shulehe Formation indicate that uplift of the North Qilian Shan initiated during this time.Palinspastic reconstruction reveals that the upper-crustal shortening is limited to 7.6-11.7 km,with up to 54%-95%accommodated by the frontal thrusts of the North Qilian Shan.These observations indicate that North Qilian Shan has acted as a stable plateau margin since the Middle Miocene,with limited northeastward propagation of deformation into the Jiuquan Basin.Reinterpretation of previously published deep geophysical data identifies a north-dipping lithospheric-scale fault offsetting the Moho by~7.8 km.Collectively,our results support a lithospheric-scale tectonic wedge model along the northeastern margin of the Tibetan Plateau,in which the rigid Jiuquan Basin indents into the weakened North Qilian lower crust under horizontal compression,accommodating limited convergence without large-scale subduction.Our findings suggest that northeastward plateau growth occurs through lithospheric wedging of mechanically distinct tectonic units characterized by distributed deformation,rather than by intracontinental subduction localized along a discrete subduction zone.
文摘The Pamir region, located to the northwest of the Tibetan Plateau, provides important information that can aid the understanding of the plateau＇s tectonic evolution. Here we present new findings on the deforma- tion geometry and timing of the Wupoer thrust belt at the northeastem margin of Pamir. Field investigations and interpretations of seismic profiles indicate that the eastern portion of the Wupoer thrust belt is dominated by an underlying foreland basin and an overlying piggy-back basin. A regional unconformity occurs between the Pliocene （N2） and the underlying Miocene （NI） or Paleogene （Pg） strata associated with two other local unconformities between Lower Pleistocene （Q1） and N2 and between Middle Pleistocene （Q2-4） and Q1 strata. Results of structural restorations suggest that compres- sional deformation was initiated during the latest Miocene to earliest Pliocene, contributing a total shortening magnitude of 48.6 km with a total shortening rate of 48.12%, most of which occurred in the period from the latest Miocene to earliest Pliocene. These results, com- bined with previous studies on the Kongur and Tarshkor- gan extensional system, suggest an interesting picture of strong piedmont compressional thrusting activity concur- rent with interorogen extensional rifting. Combining these results with previously published work on the lithospheric architecture of the Pamir, we propose that gravitational collapse drove the formation of simultaneous extensional and compressional structures with a weak, ductile middle crustal layer acting as a decollement along which both the extensional and compressional faults merged.
文摘The global rise in sea level during the Late Cretaceous has been an issue under discussion by the international geological community. Despite the signifi- cance, its impact on the deposition of continental basins is not well known. This paper presents the systematic review on stratigraphy and sedimentary facies compiled from 22 continental basins in northern Africa. The results indicate that the region was dominated by sediments of continental facies during Early Cretaceous, which were replaced by deposits of marine facies in Late Cretaceous. The spatio- temporal distribution of sedimentary facies suggests marine facies deposition reached as far south as Taou- deni-Iullemmeden-Chad-A1 Kufra-Upper Egypt basins during Turonian to Campanian. These results indicate that northern Africa underwent significant transgression during Late Cretaceous reaching its peak during Turonian to Coniacian. This significant transgression has been attributed to the global high sea-level during this time. Previous studies show that global rise in sea level in Late Cretaceous may have been driven by an increase in the volume of ocean water （attributed to high C02 concentra- tion and subsequently warm climate） and a decrease in the volume of the ocean basin （attributed to rapid production of oceanic crust and seamounts）. Tectonic mechanism of rapid production of oceanic crust and seamounts could play a fimdamental role in driving the global rise in sea level and subsequent transgression in northern Africa during Late Cretaceous.
