Since most of the natural disasters in the Yellow River are caused by sediment,the study of sediment composition,erosion and transport law is a fundamental part of sediment management in the Yellow River.As a method o...Since most of the natural disasters in the Yellow River are caused by sediment,the study of sediment composition,erosion and transport law is a fundamental part of sediment management in the Yellow River.As a method of in-situ testing,shear wave detection can obtain physical parameters such as the shear modulus of sediment.This paper,based on the Biot–Stoll model,deduces the equations for calculating the reflection and transmission coefficients when a shear wave is incident at the interface between sediment layer,and analyzes the effects of frequency,incident angle and porosity on the reflection and transmission coeffi cients of shear waves,as well as the diff erences in the propagation characteristics of longitudinal and shear waves at the interface between sediment layer.The results indicate that the refl ection and transmission coeffi cients of shear waves are linearly related to the porosity of sediment,and the refl ection coeffi cient of shear waves increases with the increase of porosity.The incident angle has a great infl uence on the changes of the reflection and transmission coefficients of shear waves,especially near the critical angle,the coeffi cients change abruptly.The frequency has a great infl uence on the refl ection and transmission coeffi cients of shear waves only near the characteristic frequency of sediment,while deviation from the characteristic frequency,the infl uence is small.The research results have certain signifi cance for obtaining the physical parameters of sediment and analyzying the composition of the Yellow River sediment and its erosion law.展开更多
BACKGROUND: Medulloblastoma is a primitive neuro-ectodermal tumor. It is common in childhood, but rarely seen at adult age, comprising only 1% of primary brain tumors.METHODS: We treated a 31-year-old man presented to...BACKGROUND: Medulloblastoma is a primitive neuro-ectodermal tumor. It is common in childhood, but rarely seen at adult age, comprising only 1% of primary brain tumors.METHODS: We treated a 31-year-old man presented to the emergency department(ED) with a chief complaint of nausea and vomiting for one week duration. Immediate frozen section revealed a grade IV medulloblastoma. During the hospital course, the patient was given craniospinal irradiation with chemotherapy.RESULTS: The patient was eventually discharged from the hospital to an assisted living facility after an uneventful 15-day course with the aid of social work.CONCLUSIONS: Despite intracranial tumors generally being slow growing masses, this patient demonstrates how quickly one can decompensate, and how important it is to recognize these clinical signs and symptoms of an intracranial lesion. Although these symptoms(i.e. Cushing response) are extremely rare, the ED physician should be aware and appreciate their clinical signifi cance.展开更多
Sherwood Anderson is an American famous short story writer.The most enduring work of his is the short story sequence Winesburg,Ohio.He is good at capturing the real sound of everyday speech in his writing and creating...Sherwood Anderson is an American famous short story writer.The most enduring work of his is the short story sequence Winesburg,Ohio.He is good at capturing the real sound of everyday speech in his writing and creating it in new forms and styles.And Death in the Woods is considered as one of his most distinctive stories.It depicts a miserable old woman who feeds others all her life by using symbols to enrich the simple story.This paper intends to reveal the author's deep reflection of American's indifferent and apathetic attitudes in the whole society by means of the symbols of the person,color and dog.展开更多
A neural statistical approach to the reconstruction of novel viewpoint image us ing general regression neural networks(GRNN) is presented. Different color value will be obtained by watching the same surface point of a...A neural statistical approach to the reconstruction of novel viewpoint image us ing general regression neural networks(GRNN) is presented. Different color value will be obtained by watching the same surface point of an object from different viewpoints due to specular reflection, and the difference is related to the pos ition of viewpoint. The relationship between the position of viewpoint and the c olor of image is non linear, neural network is introduced to make curve fitting , where the inputs of neural network are only a few calibrated images with obvio us specular reflection. By training the neural network, network model is obtaine d. By inputing an arbitrary virtual viewpoint to the model, the image of the vir tual viewpoint can be computed. By using the method presented here, novel viewpo int image with photo realistic property can be obtained, especially images with obvious specular reflection can accurately be generated. The method is an image based rendering method, geometric model of the scene and position of lighting are not needed.展开更多
In order to realize the communicative function of English and reduce the disadvantages of large-class teaching,group work can be adopted to achieve the goal to some extent with its practical significance.This paper ai...In order to realize the communicative function of English and reduce the disadvantages of large-class teaching,group work can be adopted to achieve the goal to some extent with its practical significance.This paper aims to illustrate the advantages of group work and some reflections on the real application of group work activities in teaching.展开更多
With great a quantity of upgraded colleges accounted in Guangxi Zhuang Automous Region,self-development of college English teachers directly appeals to the quality of teaching,English curriculum program and academic d...With great a quantity of upgraded colleges accounted in Guangxi Zhuang Automous Region,self-development of college English teachers directly appeals to the quality of teaching,English curriculum program and academic development competence.The paper preliminarily stepped in the internal and external elements on the them to carry on inquiry to the findings that these teachers are in good consciousness of language skills,specialized knowledge and personal communication,common improvement conformed with the achievements abroad.And by interviewing the convenient sampling the inquiryshows that they have the consciousness of changing with times.The hardest challenging is deficiency of quality education channels to promote their teaching competence and academic ability.The paper is advisory for playing vital role in their self-development inquiry in a whole perspective.展开更多
To identify refl ector fractures near borehole by using dipole-source refl ected-shearwave logging, we need to understand the relation between the amplitude of the refl ected shear wave and the source radiation, boreh...To identify refl ector fractures near borehole by using dipole-source refl ected-shearwave logging, we need to understand the relation between the amplitude of the refl ected shear wave and the source radiation, borehole conditions, and attenuation owing to the surrounding formations. To assess the effect of these factors on the amplitude of the refl ected waves, we first studied the radiation performance and radiation direction of the dipole source in fast, medium, and slow formations by using the asymptotic solution in the far fi eld of the borehole. Then, the relation between the fracture parameters, and the refl ected-shear-wave amplitude as well as the ratio of the refl ected-shear-wave amplitude to the direct-wave amplitude (relative amplitude, RA) was evaluated by the three-dimensional fi nite-difference (3D FDTD) method. Finally, the fracture detection capability of the dipole reflected-shear-wave logging tool in different formations was analyzed by using the RA. The results suggest that the radiation amplitude of the SH-wave in the slow formation is weaker than those in the fast and medium formations, and the amplitude of the refl ected shear wave is lower. However, the RA in the slow formation is close to or even greater than in the fast and medium formations, which means that dipole-source shear-wave logging has the same or even better fracture detection capability in the slow formation as in the fast and medium formations. In addition, when RA is small, there is a good correlation between the RA and the various fracture parameters in the different types of formation, which can be used in determining the lower limit of the fracture parameters identifi ed by refl ection logging.展开更多
Coal seams have a pronounced bedding structure with developed cracks and exhibit signifi cant anisotropy.However,few studies have examined the frequency dispersion properties of channel waves in anisotropic coal seams...Coal seams have a pronounced bedding structure with developed cracks and exhibit signifi cant anisotropy.However,few studies have examined the frequency dispersion properties of channel waves in anisotropic coal seams.In this study,numerical solutions are calculated using the generalized reflection–transmission coefficient method for the dispersion curves of Love channel waves in vertical transversely isotropic(VTI)and horizontal transversely isotropic(HTI)medium models.Moreover,the frequency dispersion characteristics of Love channel waves in several typical transversely isotropic models are analyzed.We fi nd that the dispersion curves for isotropic and VTI media diff er signifi cantly.In addition,the phase and Airy-phase velocities in VTI media are higher than those in isotropic media.Thus,neglecting this difference in practical channel wave detection will result in large detection errors.The dispersion curves for the isotropic and HTI media do not differ signifi cantly,and the Airy-phase velocities of various modes are similar.The group-velocity curve for a coal seam model containing a dirt band is found to be extremely irregular.The fundamental-mode Airy phase is not pronounced,but the fi rst-mode Airy phase can be clearly observed.Hence,fi rst-mode channel waves are suitable for detecting dirt bands.展开更多
Seismic deconvolution plays an important role in the seismic characterization of thin-layer structures and seismic resolution enhancement.However,the trace-by-trace processing strategy is applied and ignores the spati...Seismic deconvolution plays an important role in the seismic characterization of thin-layer structures and seismic resolution enhancement.However,the trace-by-trace processing strategy is applied and ignores the spatial connection along seismic traces,which gives the deconvolved result strong ambiguity and poor spatial continuity.To alleviate this issue,we developed a structurally constrained deconvolution algorithm.The proposed method extracts the refl ection structure characterization from the raw seismic data and introduces it to the multichannel deconvolution algorithm as a spatial refl ection regularization.Benefi ting from the introduction of the reflection regularization,the proposed method enhances the stability and spatial continuity of conventional deconvolution methods.Synthetic and field data examples confi rm the correctness and feasibility of the proposed method.展开更多
This study proposes an elastic finite difference(FD)time domain method with variable grids in three-dimensional cylindrical coordinates.The calculations will diverge and become less accurate by conventional cylindrica...This study proposes an elastic finite difference(FD)time domain method with variable grids in three-dimensional cylindrical coordinates.The calculations will diverge and become less accurate by conventional cylindrical FD as the grid size gradually becomes more extensive with the increasing radius.To prevent grids from being too coarse in far fields,we compensate for the grid cell infl ation by refi ning the grid step in the azimuthal direction.The variable grid FD in the cylindrical coordinate systems has a higher effi ciency in solving acoustic logging while drilling(LWD)problems because the grid boundaries are consistent with those of the drill collar and the borehole.The proposed algorithm saves approximately 94%of the FD grids,80%of the computation time,and memory with a higher calculation accuracy than the FD on rectangular grids for the same models.We also calculate the acoustic LWD responses of the fl uid-fi lled borehole intersecting with fractures.Refl ections are generated at the fractures,which can be equivalent to an additional scattering source.The mode conversions between the collar and the Stoneley waves are revealed.The Stoneley spectra are more sensitive to the fracture.Finally,the logs in a heterogeneous formation with two refl ectors far from the borehole are modeled,and a means of estimating the azimuth of geological interfaces from refl ections is proposed.展开更多
基金supported by the Natural Science Foundation of Henan Province(Grant No.202300410547)National Natural Science Foundation of China(Grant No.41774066)Fundamental Research Funds for Yellow River Institute of Hydraulic Research(Grant No.HKY-JBYW-2021-10).
文摘Since most of the natural disasters in the Yellow River are caused by sediment,the study of sediment composition,erosion and transport law is a fundamental part of sediment management in the Yellow River.As a method of in-situ testing,shear wave detection can obtain physical parameters such as the shear modulus of sediment.This paper,based on the Biot–Stoll model,deduces the equations for calculating the reflection and transmission coefficients when a shear wave is incident at the interface between sediment layer,and analyzes the effects of frequency,incident angle and porosity on the reflection and transmission coeffi cients of shear waves,as well as the diff erences in the propagation characteristics of longitudinal and shear waves at the interface between sediment layer.The results indicate that the refl ection and transmission coeffi cients of shear waves are linearly related to the porosity of sediment,and the refl ection coeffi cient of shear waves increases with the increase of porosity.The incident angle has a great infl uence on the changes of the reflection and transmission coefficients of shear waves,especially near the critical angle,the coeffi cients change abruptly.The frequency has a great infl uence on the refl ection and transmission coeffi cients of shear waves only near the characteristic frequency of sediment,while deviation from the characteristic frequency,the infl uence is small.The research results have certain signifi cance for obtaining the physical parameters of sediment and analyzying the composition of the Yellow River sediment and its erosion law.
文摘BACKGROUND: Medulloblastoma is a primitive neuro-ectodermal tumor. It is common in childhood, but rarely seen at adult age, comprising only 1% of primary brain tumors.METHODS: We treated a 31-year-old man presented to the emergency department(ED) with a chief complaint of nausea and vomiting for one week duration. Immediate frozen section revealed a grade IV medulloblastoma. During the hospital course, the patient was given craniospinal irradiation with chemotherapy.RESULTS: The patient was eventually discharged from the hospital to an assisted living facility after an uneventful 15-day course with the aid of social work.CONCLUSIONS: Despite intracranial tumors generally being slow growing masses, this patient demonstrates how quickly one can decompensate, and how important it is to recognize these clinical signs and symptoms of an intracranial lesion. Although these symptoms(i.e. Cushing response) are extremely rare, the ED physician should be aware and appreciate their clinical signifi cance.
文摘Sherwood Anderson is an American famous short story writer.The most enduring work of his is the short story sequence Winesburg,Ohio.He is good at capturing the real sound of everyday speech in his writing and creating it in new forms and styles.And Death in the Woods is considered as one of his most distinctive stories.It depicts a miserable old woman who feeds others all her life by using symbols to enrich the simple story.This paper intends to reveal the author's deep reflection of American's indifferent and apathetic attitudes in the whole society by means of the symbols of the person,color and dog.
文摘A neural statistical approach to the reconstruction of novel viewpoint image us ing general regression neural networks(GRNN) is presented. Different color value will be obtained by watching the same surface point of an object from different viewpoints due to specular reflection, and the difference is related to the pos ition of viewpoint. The relationship between the position of viewpoint and the c olor of image is non linear, neural network is introduced to make curve fitting , where the inputs of neural network are only a few calibrated images with obvio us specular reflection. By training the neural network, network model is obtaine d. By inputing an arbitrary virtual viewpoint to the model, the image of the vir tual viewpoint can be computed. By using the method presented here, novel viewpo int image with photo realistic property can be obtained, especially images with obvious specular reflection can accurately be generated. The method is an image based rendering method, geometric model of the scene and position of lighting are not needed.
文摘In order to realize the communicative function of English and reduce the disadvantages of large-class teaching,group work can be adopted to achieve the goal to some extent with its practical significance.This paper aims to illustrate the advantages of group work and some reflections on the real application of group work activities in teaching.
文摘With great a quantity of upgraded colleges accounted in Guangxi Zhuang Automous Region,self-development of college English teachers directly appeals to the quality of teaching,English curriculum program and academic development competence.The paper preliminarily stepped in the internal and external elements on the them to carry on inquiry to the findings that these teachers are in good consciousness of language skills,specialized knowledge and personal communication,common improvement conformed with the achievements abroad.And by interviewing the convenient sampling the inquiryshows that they have the consciousness of changing with times.The hardest challenging is deficiency of quality education channels to promote their teaching competence and academic ability.The paper is advisory for playing vital role in their self-development inquiry in a whole perspective.
基金supported by the National Petroleum Major Projects(No.2017ZX05019-005)CNPC Fundamental Research Projects(No.2016A-3605)
文摘To identify refl ector fractures near borehole by using dipole-source refl ected-shearwave logging, we need to understand the relation between the amplitude of the refl ected shear wave and the source radiation, borehole conditions, and attenuation owing to the surrounding formations. To assess the effect of these factors on the amplitude of the refl ected waves, we first studied the radiation performance and radiation direction of the dipole source in fast, medium, and slow formations by using the asymptotic solution in the far fi eld of the borehole. Then, the relation between the fracture parameters, and the refl ected-shear-wave amplitude as well as the ratio of the refl ected-shear-wave amplitude to the direct-wave amplitude (relative amplitude, RA) was evaluated by the three-dimensional fi nite-difference (3D FDTD) method. Finally, the fracture detection capability of the dipole reflected-shear-wave logging tool in different formations was analyzed by using the RA. The results suggest that the radiation amplitude of the SH-wave in the slow formation is weaker than those in the fast and medium formations, and the amplitude of the refl ected shear wave is lower. However, the RA in the slow formation is close to or even greater than in the fast and medium formations, which means that dipole-source shear-wave logging has the same or even better fracture detection capability in the slow formation as in the fast and medium formations. In addition, when RA is small, there is a good correlation between the RA and the various fracture parameters in the different types of formation, which can be used in determining the lower limit of the fracture parameters identifi ed by refl ection logging.
基金supported by the National Key R&D Program of China (No. 2018YFC0807804-3)Key R&D Program of Anhui Province (No. 1804a0802213)Scientifi c Research Foundation for the introduction talent of Anhui University of Science and Technology。
文摘Coal seams have a pronounced bedding structure with developed cracks and exhibit signifi cant anisotropy.However,few studies have examined the frequency dispersion properties of channel waves in anisotropic coal seams.In this study,numerical solutions are calculated using the generalized reflection–transmission coefficient method for the dispersion curves of Love channel waves in vertical transversely isotropic(VTI)and horizontal transversely isotropic(HTI)medium models.Moreover,the frequency dispersion characteristics of Love channel waves in several typical transversely isotropic models are analyzed.We fi nd that the dispersion curves for isotropic and VTI media diff er signifi cantly.In addition,the phase and Airy-phase velocities in VTI media are higher than those in isotropic media.Thus,neglecting this difference in practical channel wave detection will result in large detection errors.The dispersion curves for the isotropic and HTI media do not differ signifi cantly,and the Airy-phase velocities of various modes are similar.The group-velocity curve for a coal seam model containing a dirt band is found to be extremely irregular.The fundamental-mode Airy phase is not pronounced,but the fi rst-mode Airy phase can be clearly observed.Hence,fi rst-mode channel waves are suitable for detecting dirt bands.
基金National Key R&D Program of China(No.2018YFA0702504)the National Natural Science Foundation of China(Nos.42074141,41874141)the Strategic Cooperation Technology Projects of CNPC and CUP(ZLZX2020-03).
文摘Seismic deconvolution plays an important role in the seismic characterization of thin-layer structures and seismic resolution enhancement.However,the trace-by-trace processing strategy is applied and ignores the spatial connection along seismic traces,which gives the deconvolved result strong ambiguity and poor spatial continuity.To alleviate this issue,we developed a structurally constrained deconvolution algorithm.The proposed method extracts the refl ection structure characterization from the raw seismic data and introduces it to the multichannel deconvolution algorithm as a spatial refl ection regularization.Benefi ting from the introduction of the reflection regularization,the proposed method enhances the stability and spatial continuity of conventional deconvolution methods.Synthetic and field data examples confi rm the correctness and feasibility of the proposed method.
基金supported by the National Natural Science Foundation of China(Grant Nos.12174421,11774373,11734017,and 42074215).
文摘This study proposes an elastic finite difference(FD)time domain method with variable grids in three-dimensional cylindrical coordinates.The calculations will diverge and become less accurate by conventional cylindrical FD as the grid size gradually becomes more extensive with the increasing radius.To prevent grids from being too coarse in far fields,we compensate for the grid cell infl ation by refi ning the grid step in the azimuthal direction.The variable grid FD in the cylindrical coordinate systems has a higher effi ciency in solving acoustic logging while drilling(LWD)problems because the grid boundaries are consistent with those of the drill collar and the borehole.The proposed algorithm saves approximately 94%of the FD grids,80%of the computation time,and memory with a higher calculation accuracy than the FD on rectangular grids for the same models.We also calculate the acoustic LWD responses of the fl uid-fi lled borehole intersecting with fractures.Refl ections are generated at the fractures,which can be equivalent to an additional scattering source.The mode conversions between the collar and the Stoneley waves are revealed.The Stoneley spectra are more sensitive to the fracture.Finally,the logs in a heterogeneous formation with two refl ectors far from the borehole are modeled,and a means of estimating the azimuth of geological interfaces from refl ections is proposed.
