The finite element artificial transmitting boundary method is employed here to treat the near field scattering of a cylindrical wave from an irregular cylinder. A comparison is made between this method and the analy...The finite element artificial transmitting boundary method is employed here to treat the near field scattering of a cylindrical wave from an irregular cylinder. A comparison is made between this method and the analytical one. And then examples are given to demonstrate the solution of several problems of the irregular object scattering. The method can not only produce clear physical pictures, but can efficiently handle many complicated scattering problems.展开更多
To obtain good trade-offs between complexity and performance onpeak-to-average power ratio (PAPR) reduction in orthogonal frequency division multiplexing (OFDM)using partial transmitting sequence (PTS) schemes, a trel...To obtain good trade-offs between complexity and performance onpeak-to-average power ratio (PAPR) reduction in orthogonal frequency division multiplexing (OFDM)using partial transmitting sequence (PTS) schemes, a trellis structure based PTS factor searchmethod is proposed. The trellis search is with a variant constraint length L_C, 1 ≤ L_C ≤ V-1,where V is the number of PTS subblocks. The method is to decide a PTS factor by searching all thepossible paths obtained by varying L_C consecutive factors. The trellis search can be viewed as ageneral PTS factor search model. If L_C = V-1, it is a full search, and if L_C = 1, it is aniterative search. Using different constraint lengths, trellis factor search PTS exhibits differentPAPR reduction performances. A larger L_C results in a better performance and L_C = V-1 results inthe optimum. However, a larger L_C requires more computation. This helps to choose a good trade-offbetween complexity and performance.展开更多
We investigated image processing algorithms of the original infrared glass flaw image. Using the Laplacian edge enhancement following LSD (Line Segment Detector) algorithm, we can get a good flaw image very consiste...We investigated image processing algorithms of the original infrared glass flaw image. Using the Laplacian edge enhancement following LSD (Line Segment Detector) algorithm, we can get a good flaw image very consistent with the original one. This study is very helpful to further enhance the infrared glass flaw inspection technique.展开更多
Based on the modified scale boundary finite element method and continued fraction solution,a high-order doubly asymptotic transmitting boundary(DATB)is derived and extended to the simulation of vector wave propagation...Based on the modified scale boundary finite element method and continued fraction solution,a high-order doubly asymptotic transmitting boundary(DATB)is derived and extended to the simulation of vector wave propagation in complex layered soils.The high-order DATB converges rapidly to the exact solution throughout the entire frequency range and its formulation is local in the time domain,possessing high accuracy and good efficiency.Combining with finite element method,a coupled model is constructed for time-domain analysis of underground station-layered soil interaction.The coupled model is divided into the near and far field by the truncated boundary,of which the near field is modelled by FEM while the far field is modelled by the high-order DATB.The coupled model is implemented in an open source finite element software,OpenSees,in which the DATB is employed as a super element.Numerical examples demonstrate that results of the coupled model are stable,accurate and efficient compared with those of the extended mesh model and the viscous-spring boundary model.Besides,it has also shown the fitness for long-time seismic response analysis of underground station-layered soil interaction.Therefore,it is believed that the coupled model could provide a new approach for seismic analysis of underground station-layered soil interaction and could be further developed for engineering.展开更多
The transmitting properties of acoustic emission(AE) signal is investigated in order to provide experimental basis for application of AE technique. In the paper, the influences of the geometric shape and material prop...The transmitting properties of acoustic emission(AE) signal is investigated in order to provide experimental basis for application of AE technique. In the paper, the influences of the geometric shape and material properties of the mediums and the bearing type on AE transmission are analyzed for providing the theoretic foundation for selecting the transmission route of AE signal and the fixing location of the AE sensor reasonably. According to the transmitting properties of AE, an apparatus of detecting AE signal for the tool breakage monitoring system has been set up. Its application results show that it is of benefit to improving the sensitivity of the tool breakage monitoring system.展开更多
Local coupling instability will occur when the numerical scheme of absorbing boundary condition and that of the field wave equation allow energies to spontaneously enter into the computational domain. That is, the two...Local coupling instability will occur when the numerical scheme of absorbing boundary condition and that of the field wave equation allow energies to spontaneously enter into the computational domain. That is, the two schemes support common wave solutions with group velocity pointed into the computation domain. The key to eliminate local coupling instability is to avoid such wave solutions. For lumped-mass finite element simulation of P-SV wave motion in a 2D waveguide, an approach for stable implementation of high order multi-transmitting formula is provided. With a uniform rectangular mesh, it is proven and validated that high-freqaency local coupling instability can be eliminated by setting the ratio of the element size equal to or greater than x/2 times the ratio of the P wave velocity to the S wave velocity. These results can be valuable for dealing instability problems induced by other absorbing boundary conditions.展开更多
This paper summarizes the basic situation of the Binchuan Transmitting Seismic Station and the geophysical observations of the area where it is located,with a focus on the constitution of the observation system of the...This paper summarizes the basic situation of the Binchuan Transmitting Seismic Station and the geophysical observations of the area where it is located,with a focus on the constitution of the observation system of the transmitting seismic station,the excitation characteristics and propagation distance of signals excited by the airgun source in the reservoir and well. The paper also summarizes and discusses on the results of the observations and problems encountered since the Transmitting Seismic Station was built.Finally,this paper proposes the main research to be carried out on the basis of the project aims.展开更多
The influence derived from atmosphere transmitting of radar wave, in the application of high-resolution airborne Synthetic Aperture Radar (SAR) stereo positioning, may produce some phase errors, and eventually be intr...The influence derived from atmosphere transmitting of radar wave, in the application of high-resolution airborne Synthetic Aperture Radar (SAR) stereo positioning, may produce some phase errors, and eventually be introduced into positioning model. This paper described the principle of airborne SAR stereo positioning and the error sources of stereo positioning accuracy that arose from atmosphere transmitting, established a corresponding assess- ment model of atmosphere transmitting influence, and testified the model and the assessment principle taking the 1-m resolution airborne SAR images of Zigong City, Sichuan Province in China, as the test dataset. The test result has proved that the assessment model is reliable and reasonable. And, it has shown that the phase error arisen from time delay is the main error source during the atmosphere transmitting, which has much more influences on cross-track di- rection and introduces a stereo positioning error of about eight meters, but less on the along-track direction.展开更多
Common clay, Kaolin and Bentonite were used as additives to prepare water-transmitting coating fiber, respectively, and the water-transmitting characteristic of coating fiber was studied. Different water-transmitting ...Common clay, Kaolin and Bentonite were used as additives to prepare water-transmitting coating fiber, respectively, and the water-transmitting characteristic of coating fiber was studied. Different water-transmitting coating fibers were prepared by coating fiber using coating material with different mass proportions of additives to adhesive. And the coating materials were made from three kinds of inorganic clays as additives respectively and polyvinyl alcohol (PVA) as adhesive. Furthermore, the surface morphology and water-transmitting capacity of coating fiber were studied by SEM, Perkin Elmer Diamond SII thermal multi-analyzer and instrument for quick measurement moisture M30. The experimental results indicate that water-transmitting coating fibers made from three kinds of clays all have water-transmitting capacity. The surface of water-transmitting coating fiber prepared by common clay T is continuous and compact, and the water-transmitting effect is better than coating fibers made from other clays.展开更多
An accurate numerical simulation for wave equations is essential for understanding of wave propagation in the earth's interior as well as full waveform inversion and reverse time migration. However, due to computa...An accurate numerical simulation for wave equations is essential for understanding of wave propagation in the earth's interior as well as full waveform inversion and reverse time migration. However, due to computational cost and hardware capability limitations, numerical simulations are often performed within a finite domain. Thus, an adequate absorbing boundary condition (ABC) is indispensable for obtaining accurate numerical simulation results. In this study, we develop a hybrid ABC based on a transmitting boundary, which is referred to as THABC, to eliminate artificial boundary reflections in 3D second-order fractional viscoacoustic numerical simulations. Furthermore, we propose an adaptive weighted coefficient to reconcile the transmitting and viscoacoustic wavefields in THABC. Through several numerical examples, we determine that the proposed THABC approach is characterized by the following benefits. First, with the same number of absorbing layers, THABC exhibits a better ability in eliminating boundary reflection than traditional ABC schemes. Second, THABC is more effective in computation, since it only requires the wavefields at the current and last time steps to solve the transmitting formula within the absorbing layers. Benefiting from a simple but effective combination between the transmitting equation and the second-order wave equation, our scheme performs well in the 3D fractional Laplacian viscoacoustic numerical simulation.展开更多
In this paper, we conduct research on the novel mode of plane graphic design from the core angle of the primary visual language transmitting. Relationship between nationality and cosmopolitan processing in graphic des...In this paper, we conduct research on the novel mode of plane graphic design from the core angle of the primary visual language transmitting. Relationship between nationality and cosmopolitan processing in graphic design in the design of image symbol expression and significance of the symbol on the one hand require symbolic form must have enough openness and the cognitive function on the other hand with semiotics method can let the designer to extract the most representative and symbolic notation style to carry on the design expression. As a non- verbal symbols, from the perspective of the view, the design image is no national boundaries, but the human form to beauty and should express the symbolism of cognition is the same. In the form of the ethnic groups of the cosmopolitan codes are for identification of Chinese contemporary design possible effective methods. Our research proposes novel perspective of the design which is meaningful.展开更多
The flexibility of unmanned aerial vehicles(UAVs)allows them to be quickly deployed to support ground users.Intelligent reflecting surface(IRS)can reflect the incident signal and form passive beamforming to enhance th...The flexibility of unmanned aerial vehicles(UAVs)allows them to be quickly deployed to support ground users.Intelligent reflecting surface(IRS)can reflect the incident signal and form passive beamforming to enhance the signal in the specific direction.Motivated by the promising benefits of both technologies,we consider a new scenario in this paper where a UAV uses non-orthogonal multiple access to serve multiple users with IRS.According to their distance to the UAV,the users are divided into the close users and remote users.The UAV hovers above the close users due to their higher rate requirement,while the IRS is deployed near the remote users to enhance their received power.We aim at minimizing the transmit power of UAV by jointly optimizing the beamforming of UAV and the phase shift of IRS while ensuring the decoding requirement.However,the problem is non-convex.Therefore,we decompose it into two sub-problems,including the transmit beamforming optimization and phase shift optimization,which are transformed into second-order cone programming and semidefinite programming,respectively.We propose an iterative algorithm to solve the two sub-problems alternatively.Simulation results prove the effectiveness of the proposed scheme in minimizing the transmit power of UAV.展开更多
The theory of perfectly matched layer (PML) artificial boundary condition (ABC), which is characterized by absorption any wave motions with arbitrary frequency and arbitrarily incident angle, is introduced. The co...The theory of perfectly matched layer (PML) artificial boundary condition (ABC), which is characterized by absorption any wave motions with arbitrary frequency and arbitrarily incident angle, is introduced. The construction process of PML boundary based on elastodynamic partial differential equation (PDE) system is developed. Combining with velocity-stress hybrid finite element formulation, the applicability of PML boundary is investigated and the numerical reflection of PML boundary is estimated. The reflectivity of PML and multi-transmitting formula (MTF) boundary is then compared based on body wave and surface wave simulations. The results show that although PML boundary yields some reflection, its absorption performance is superior to MTF boundary in the numerical simulations of near-fault wave propagation, especially in comer and large angle grazing incidence situations. The PML boundary does not arise any unstable phenomenon and the stability of PML boundary is better than MTF boundary in hybrid finite element method. For a specified problem and analysis tolerance, the computational efficiency of PML boundary is only a little lower than MTF boundary.展开更多
Objectives: To understand trends and epidemiology of STDs in Chongqing from 1998 to 2003 and to provide scientific evidence for developing preventive strategies and distributing government health resources effectivel...Objectives: To understand trends and epidemiology of STDs in Chongqing from 1998 to 2003 and to provide scientific evidence for developing preventive strategies and distributing government health resources effectively. Methods: STD case-reporting data collected from 43 counties and districts in Chongqing from 1998 to 2003 were analyzed with STD Data Management Software and Excel Software. Results: A total of 133,323 cases of eight different STDs were reported from 1998-2003. The annual incidence of all eight STDs combined was 71.89/10^5.Generally, reported cases and incidence have decreased since 2001. Although gonorrhoea diagnoses made up a significant proportion of the STD burden, this proportion decreased annually. The proportion of the STD burden attributed to Condyloma accuminatum (CA) was always above 30 percent. The proportions of non-gonoccocal urethritis, genital herpes and syphilis within the combinedSTD burden increased gradually from 1998 to 2003.Reported cases of HIV increased rapidly over this time. A total of 214 HIV cases were reported from 1998 to 2003,the majority of which were among men. For HIV, the maleto-female ratio was 1.17, but CA was found among more women than men. Incidence for all STDs was highest among 20-39 year olds, who accounted for 72.2% of reported infections. The majority of STDs were transmitted through extra-marital intercourse,accounting for 55.3%. Conclusion: The STD epidemic in Chongqing changed from 1998-2003. STD incidence declined, as a result of various factors. The epidemiology of STDs has changed.HIV incidence has increased rapidly. This indicates that the AIDS epidemic has reached a critical period. The results of this study suggest a need for readjusting control measures and redistributing health resources.展开更多
Transmitted ultrasonic wave simulation (TUWS) in a digital core is one of the important elements of digital rock physics and is used to study wave propagation in porous cores and calculate equivalent velocity. When ...Transmitted ultrasonic wave simulation (TUWS) in a digital core is one of the important elements of digital rock physics and is used to study wave propagation in porous cores and calculate equivalent velocity. When simulating wave propagates in a 3D digital core, two additional layers are attached to its two surfaces vertical to the wave-direction and one planar wave source and two receiver-arrays are properly installed. After source excitation, the two receivers then record incident and transmitted waves of the digital rock. Wave propagating velocity, which is the velocity of the digital core, is computed by the picked peak-time difference between the two recorded waves. To evaluate the accuracy of TUWS, a digital core is fully saturated with gas, oil, and water to calculate the corresponding velocities. The velocities increase with decreasing wave frequencies in the simulation frequency band, and this is considered to be the result of scattering. When the pore fluids are varied from gas to oil and finally to water, the velocity-variation characteristics between the different frequencies are similar, thereby approximately following the variation law of velocities obtained from linear elastic statics simulation (LESS), although their absolute values are different. However, LESS has been widely used. The results of this paper show that the transmission ultrasonic simulation has high relative precision.展开更多
Sexually transmitted diseases (STDs) are among the first ten causes of unpleasant diseases in young adult males in developing countries and the second major cause of unpleasant diseases in young adult women. Adolesc...Sexually transmitted diseases (STDs) are among the first ten causes of unpleasant diseases in young adult males in developing countries and the second major cause of unpleasant diseases in young adult women. Adolescents and young adults (15-24 years old) make up only 25% of the sexually active population, but represent almost 50% of all new acquired STDs. In general, STDs are epidemics and present an enormous health and economic consequences. An adequate screening for STDs should be done on a routine basis in every part of the world. Many STDs are asymptomatic and therefore can difficult to control. The purpose of reporting of STDs is to ensure that persons who are infected will be quickly diagnosed and appropriately treated to control the spread of infection and also so that partners are notified, tested and appropriately treated. It is estimated that reported cases of STDs represent only 50%-80% of reportable STD infections in the United States, reflecting limited screening and low disease reporting. High-risk sexual behavior is a highly contributive factor of this process as it often leads to teenage pregnancies and HIV/AIDS. One possible explanation for this behavior is that people do not have enough information about the transmission of STDs or ignore the precautions required for safe sex. Approximately 60% of new HIV infections worldwide occur in young people. The frequency of high-risk behaviors among youths may also be influenced by opportunity to engage in them, particularly the amount of time that they are unsupervised by adults. However, in diagnosing and treating these patients, we can effectively prevent the spread of HIV/AIDS. Individuals infected with STDs are 5-10 times more likely than uninfected individuals to acquire or transmit HIV through sexual contact. The breaking of the genital tract lining or skin creates a portal of entry for HIV and, hence, HIV-infected individuals with other STDs are more likely to shed HIV in their genital secretions. To date, the condom is the most effective method available for males for protection against STDs. It is important to control STDs, and prevention can be the key of this process. Prevention can be achieved through education of the population, identification of symptomatic and asymptomatic people, and effective diagnosis and treatment of these patients and their partners.展开更多
INIRODUCIIONA newly discovered DNA virus,transfusiontransmitted virus (TTV),was reported as a cause ofpost-transfusion hepatitis of unknown etiology inJapan.In order to investigate TTV prevalence insouthern China,a st...INIRODUCIIONA newly discovered DNA virus,transfusiontransmitted virus (TTV),was reported as a cause ofpost-transfusion hepatitis of unknown etiology inJapan.In order to investigate TTV prevalence insouthern China,a study was carried out amongblood donors,patients with liver diseases andhemodialysis to determine the epidemiologicalcharateristics.展开更多
Surface or submerged horizontal or vertical plate can be considered as a new concept breakwater. This paper investigates the wave-plate interaction of this type of breakwater by use of the boundary element method. The...Surface or submerged horizontal or vertical plate can be considered as a new concept breakwater. This paper investigates the wave-plate interaction of this type of breakwater by use of the boundary element method. The relationships of wave transmitted and reflected among plate thickness, submergence and length are carefully studied by numerical simulation. It is shown that: (1) The transmitted coefficients of submerged horizontal plate or vertical plate will become larger with the increase of plate thickness and reduce rapidly with the decrease of plate submergence. (2) Both surface horizontal and vertical plate are efficient for intermediate and short wave elimination, but vertical plate is more effective. (3) Submerged horizontal plate can act more effectively than submerged vertical plate does. With all wave frequencies, the vertical plate almost has no wave elimination effect.展开更多
In this paper,a sexually transmitted disease model is proposed on complex networks,where contacts between humans are treated as a scale-free social network.There are three groups in our model,which are dangerous male,...In this paper,a sexually transmitted disease model is proposed on complex networks,where contacts between humans are treated as a scale-free social network.There are three groups in our model,which are dangerous male,non-dangerous male,and female.By mathematical analysis,we obtain the basic reproduction number for the existence of endemic equilibrium and study the effects of various immunization schemes about different groups.Furthermore,numerical simulations are undertaken to verify more conclusions.展开更多
Cancers in solid organ recipients may be classified as donor transmitted,donor derived,de novo or recurrent.The risk of donor-transmitted cancer is very low and can be reduced by careful screening of the donor but can...Cancers in solid organ recipients may be classified as donor transmitted,donor derived,de novo or recurrent.The risk of donor-transmitted cancer is very low and can be reduced by careful screening of the donor but cannot be abolished and,in the United Kingdom series is less than 0.03%.For donors with a known history of cancer,the risks will depend on the nature of the cancer,the interventions given and the interval between diagnosis and organ donation.The risks of cancer transmission must be balanced against the risks of death awaiting a new graft and strict adherence to current guidelines may result increased patient death.Organs from selected patients,even with high-grade central nervous system(CNS)malignancy and after a shunt,can,in some circumstances,be considered.Of potential donors with non-CNS cancers,whether organs may be safely used again depends on the nature of the cancer,the treatment and interval.Data are scarce about the most appropriate treatment when donor transmitted cancer is diagnosed:sometimes substitution of agents and reduction of the immunosuppressive load may be adequate and the impact of graft removal should be considered but not always indicated.Liver al-lograft recipients are at increased risk of some de novo cancers,especially those grafted for alcohol-related liver disease and hepatitis C virus infection.The risk of lymphoproliferative disease and cancers of the skin,upper airway and bowel are increased but not breast.Recipients should be advised to avoid risk behavior and monitored appropriately.展开更多
文摘The finite element artificial transmitting boundary method is employed here to treat the near field scattering of a cylindrical wave from an irregular cylinder. A comparison is made between this method and the analytical one. And then examples are given to demonstrate the solution of several problems of the irregular object scattering. The method can not only produce clear physical pictures, but can efficiently handle many complicated scattering problems.
文摘To obtain good trade-offs between complexity and performance onpeak-to-average power ratio (PAPR) reduction in orthogonal frequency division multiplexing (OFDM)using partial transmitting sequence (PTS) schemes, a trellis structure based PTS factor searchmethod is proposed. The trellis search is with a variant constraint length L_C, 1 ≤ L_C ≤ V-1,where V is the number of PTS subblocks. The method is to decide a PTS factor by searching all thepossible paths obtained by varying L_C consecutive factors. The trellis search can be viewed as ageneral PTS factor search model. If L_C = V-1, it is a full search, and if L_C = 1, it is aniterative search. Using different constraint lengths, trellis factor search PTS exhibits differentPAPR reduction performances. A larger L_C results in a better performance and L_C = V-1 results inthe optimum. However, a larger L_C requires more computation. This helps to choose a good trade-offbetween complexity and performance.
基金Funded by the Program for New Century Excellent Talents in University (11-0687)the National Natural Science Foundation of China (51172169)the Fundamental Research Funds for the Central Universities (Wuhan University of Technology)
文摘We investigated image processing algorithms of the original infrared glass flaw image. Using the Laplacian edge enhancement following LSD (Line Segment Detector) algorithm, we can get a good flaw image very consistent with the original one. This study is very helpful to further enhance the infrared glass flaw inspection technique.
基金This research investigation was supported by the National Natural Science Foundation of China(Grant No.51678248 and Grant No.51878296)the Fundamental Research Funds for the Central Universities.And sincere thanks also to State Key Lab of Subtropical Building Science,South China University of Technology under Grant No.2017KB15 and the Open Research Fund of State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin under Grant No.IWHRSKL-KF201818.
文摘Based on the modified scale boundary finite element method and continued fraction solution,a high-order doubly asymptotic transmitting boundary(DATB)is derived and extended to the simulation of vector wave propagation in complex layered soils.The high-order DATB converges rapidly to the exact solution throughout the entire frequency range and its formulation is local in the time domain,possessing high accuracy and good efficiency.Combining with finite element method,a coupled model is constructed for time-domain analysis of underground station-layered soil interaction.The coupled model is divided into the near and far field by the truncated boundary,of which the near field is modelled by FEM while the far field is modelled by the high-order DATB.The coupled model is implemented in an open source finite element software,OpenSees,in which the DATB is employed as a super element.Numerical examples demonstrate that results of the coupled model are stable,accurate and efficient compared with those of the extended mesh model and the viscous-spring boundary model.Besides,it has also shown the fitness for long-time seismic response analysis of underground station-layered soil interaction.Therefore,it is believed that the coupled model could provide a new approach for seismic analysis of underground station-layered soil interaction and could be further developed for engineering.
基金Supported by the Laboratory of Robotics, Chinese Academy of Sciences
文摘The transmitting properties of acoustic emission(AE) signal is investigated in order to provide experimental basis for application of AE technique. In the paper, the influences of the geometric shape and material properties of the mediums and the bearing type on AE transmission are analyzed for providing the theoretic foundation for selecting the transmission route of AE signal and the fixing location of the AE sensor reasonably. According to the transmitting properties of AE, an apparatus of detecting AE signal for the tool breakage monitoring system has been set up. Its application results show that it is of benefit to improving the sensitivity of the tool breakage monitoring system.
基金the Key Projects in the National Science & Technology Pillar Program during the Twelfth Five-year Plan Period(Grant No.2015BAK17B01)Science Foundation of Institute of Engineering Mechanics,CEA under Grant No.2014B10+1 种基金Natural Science Foundation of Heilongjiang Province of China under Grant No.LC201403National Natural Science Foundation under Grant No.51378479 and No.51108431
文摘Local coupling instability will occur when the numerical scheme of absorbing boundary condition and that of the field wave equation allow energies to spontaneously enter into the computational domain. That is, the two schemes support common wave solutions with group velocity pointed into the computation domain. The key to eliminate local coupling instability is to avoid such wave solutions. For lumped-mass finite element simulation of P-SV wave motion in a 2D waveguide, an approach for stable implementation of high order multi-transmitting formula is provided. With a uniform rectangular mesh, it is proven and validated that high-freqaency local coupling instability can be eliminated by setting the ratio of the element size equal to or greater than x/2 times the ratio of the P wave velocity to the S wave velocity. These results can be valuable for dealing instability problems induced by other absorbing boundary conditions.
基金jointly sponsored by the National Natural Foundation of China(41474048)the Special Fund of Academician Chen Yong Workstation Project of Yunnan Province(2014IC007)
文摘This paper summarizes the basic situation of the Binchuan Transmitting Seismic Station and the geophysical observations of the area where it is located,with a focus on the constitution of the observation system of the transmitting seismic station,the excitation characteristics and propagation distance of signals excited by the airgun source in the reservoir and well. The paper also summarizes and discusses on the results of the observations and problems encountered since the Transmitting Seismic Station was built.Finally,this paper proposes the main research to be carried out on the basis of the project aims.
基金Under the auspices of National High Technology Research and Development Program of China (No. 2001AA132010)
文摘The influence derived from atmosphere transmitting of radar wave, in the application of high-resolution airborne Synthetic Aperture Radar (SAR) stereo positioning, may produce some phase errors, and eventually be introduced into positioning model. This paper described the principle of airborne SAR stereo positioning and the error sources of stereo positioning accuracy that arose from atmosphere transmitting, established a corresponding assess- ment model of atmosphere transmitting influence, and testified the model and the assessment principle taking the 1-m resolution airborne SAR images of Zigong City, Sichuan Province in China, as the test dataset. The test result has proved that the assessment model is reliable and reasonable. And, it has shown that the phase error arisen from time delay is the main error source during the atmosphere transmitting, which has much more influences on cross-track di- rection and introduces a stereo positioning error of about eight meters, but less on the along-track direction.
基金Funded by the National High Technology Research and Development Program of China (2001AA322100)the Ministry of Education of Republic of China (106086)the Cooperation and Merger Found of Beijing ( ZH114140537)
文摘Common clay, Kaolin and Bentonite were used as additives to prepare water-transmitting coating fiber, respectively, and the water-transmitting characteristic of coating fiber was studied. Different water-transmitting coating fibers were prepared by coating fiber using coating material with different mass proportions of additives to adhesive. And the coating materials were made from three kinds of inorganic clays as additives respectively and polyvinyl alcohol (PVA) as adhesive. Furthermore, the surface morphology and water-transmitting capacity of coating fiber were studied by SEM, Perkin Elmer Diamond SII thermal multi-analyzer and instrument for quick measurement moisture M30. The experimental results indicate that water-transmitting coating fibers made from three kinds of clays all have water-transmitting capacity. The surface of water-transmitting coating fiber prepared by common clay T is continuous and compact, and the water-transmitting effect is better than coating fibers made from other clays.
基金National Natural Science Foundation of China under Grant Nos.41930431 and 41974116Natural Science Foundation of Heilongjiang Province No.YQ2021D008CNPC Innovation Found No.2021DQ02-0302 for supporting this work.
文摘An accurate numerical simulation for wave equations is essential for understanding of wave propagation in the earth's interior as well as full waveform inversion and reverse time migration. However, due to computational cost and hardware capability limitations, numerical simulations are often performed within a finite domain. Thus, an adequate absorbing boundary condition (ABC) is indispensable for obtaining accurate numerical simulation results. In this study, we develop a hybrid ABC based on a transmitting boundary, which is referred to as THABC, to eliminate artificial boundary reflections in 3D second-order fractional viscoacoustic numerical simulations. Furthermore, we propose an adaptive weighted coefficient to reconcile the transmitting and viscoacoustic wavefields in THABC. Through several numerical examples, we determine that the proposed THABC approach is characterized by the following benefits. First, with the same number of absorbing layers, THABC exhibits a better ability in eliminating boundary reflection than traditional ABC schemes. Second, THABC is more effective in computation, since it only requires the wavefields at the current and last time steps to solve the transmitting formula within the absorbing layers. Benefiting from a simple but effective combination between the transmitting equation and the second-order wave equation, our scheme performs well in the 3D fractional Laplacian viscoacoustic numerical simulation.
文摘In this paper, we conduct research on the novel mode of plane graphic design from the core angle of the primary visual language transmitting. Relationship between nationality and cosmopolitan processing in graphic design in the design of image symbol expression and significance of the symbol on the one hand require symbolic form must have enough openness and the cognitive function on the other hand with semiotics method can let the designer to extract the most representative and symbolic notation style to carry on the design expression. As a non- verbal symbols, from the perspective of the view, the design image is no national boundaries, but the human form to beauty and should express the symbolism of cognition is the same. In the form of the ethnic groups of the cosmopolitan codes are for identification of Chinese contemporary design possible effective methods. Our research proposes novel perspective of the design which is meaningful.
基金supported by the National Natural Science Foundation of China(NSFC)under Grant 62271099。
文摘The flexibility of unmanned aerial vehicles(UAVs)allows them to be quickly deployed to support ground users.Intelligent reflecting surface(IRS)can reflect the incident signal and form passive beamforming to enhance the signal in the specific direction.Motivated by the promising benefits of both technologies,we consider a new scenario in this paper where a UAV uses non-orthogonal multiple access to serve multiple users with IRS.According to their distance to the UAV,the users are divided into the close users and remote users.The UAV hovers above the close users due to their higher rate requirement,while the IRS is deployed near the remote users to enhance their received power.We aim at minimizing the transmit power of UAV by jointly optimizing the beamforming of UAV and the phase shift of IRS while ensuring the decoding requirement.However,the problem is non-convex.Therefore,we decompose it into two sub-problems,including the transmit beamforming optimization and phase shift optimization,which are transformed into second-order cone programming and semidefinite programming,respectively.We propose an iterative algorithm to solve the two sub-problems alternatively.Simulation results prove the effectiveness of the proposed scheme in minimizing the transmit power of UAV.
基金National Natural Science Foundation of China (50608024 and 50538050).
文摘The theory of perfectly matched layer (PML) artificial boundary condition (ABC), which is characterized by absorption any wave motions with arbitrary frequency and arbitrarily incident angle, is introduced. The construction process of PML boundary based on elastodynamic partial differential equation (PDE) system is developed. Combining with velocity-stress hybrid finite element formulation, the applicability of PML boundary is investigated and the numerical reflection of PML boundary is estimated. The reflectivity of PML and multi-transmitting formula (MTF) boundary is then compared based on body wave and surface wave simulations. The results show that although PML boundary yields some reflection, its absorption performance is superior to MTF boundary in the numerical simulations of near-fault wave propagation, especially in comer and large angle grazing incidence situations. The PML boundary does not arise any unstable phenomenon and the stability of PML boundary is better than MTF boundary in hybrid finite element method. For a specified problem and analysis tolerance, the computational efficiency of PML boundary is only a little lower than MTF boundary.
文摘Objectives: To understand trends and epidemiology of STDs in Chongqing from 1998 to 2003 and to provide scientific evidence for developing preventive strategies and distributing government health resources effectively. Methods: STD case-reporting data collected from 43 counties and districts in Chongqing from 1998 to 2003 were analyzed with STD Data Management Software and Excel Software. Results: A total of 133,323 cases of eight different STDs were reported from 1998-2003. The annual incidence of all eight STDs combined was 71.89/10^5.Generally, reported cases and incidence have decreased since 2001. Although gonorrhoea diagnoses made up a significant proportion of the STD burden, this proportion decreased annually. The proportion of the STD burden attributed to Condyloma accuminatum (CA) was always above 30 percent. The proportions of non-gonoccocal urethritis, genital herpes and syphilis within the combinedSTD burden increased gradually from 1998 to 2003.Reported cases of HIV increased rapidly over this time. A total of 214 HIV cases were reported from 1998 to 2003,the majority of which were among men. For HIV, the maleto-female ratio was 1.17, but CA was found among more women than men. Incidence for all STDs was highest among 20-39 year olds, who accounted for 72.2% of reported infections. The majority of STDs were transmitted through extra-marital intercourse,accounting for 55.3%. Conclusion: The STD epidemic in Chongqing changed from 1998-2003. STD incidence declined, as a result of various factors. The epidemiology of STDs has changed.HIV incidence has increased rapidly. This indicates that the AIDS epidemic has reached a critical period. The results of this study suggest a need for readjusting control measures and redistributing health resources.
基金supported by the Open Fund of the Key Laboratory of Exploration Technologies for Oil and Gas Resources(Yangtze University)the Ministry of Education(No.K2014-06)the Reservoir Geophysical Research Center at Yangtze University
文摘Transmitted ultrasonic wave simulation (TUWS) in a digital core is one of the important elements of digital rock physics and is used to study wave propagation in porous cores and calculate equivalent velocity. When simulating wave propagates in a 3D digital core, two additional layers are attached to its two surfaces vertical to the wave-direction and one planar wave source and two receiver-arrays are properly installed. After source excitation, the two receivers then record incident and transmitted waves of the digital rock. Wave propagating velocity, which is the velocity of the digital core, is computed by the picked peak-time difference between the two recorded waves. To evaluate the accuracy of TUWS, a digital core is fully saturated with gas, oil, and water to calculate the corresponding velocities. The velocities increase with decreasing wave frequencies in the simulation frequency band, and this is considered to be the result of scattering. When the pore fluids are varied from gas to oil and finally to water, the velocity-variation characteristics between the different frequencies are similar, thereby approximately following the variation law of velocities obtained from linear elastic statics simulation (LESS), although their absolute values are different. However, LESS has been widely used. The results of this paper show that the transmission ultrasonic simulation has high relative precision.
文摘Sexually transmitted diseases (STDs) are among the first ten causes of unpleasant diseases in young adult males in developing countries and the second major cause of unpleasant diseases in young adult women. Adolescents and young adults (15-24 years old) make up only 25% of the sexually active population, but represent almost 50% of all new acquired STDs. In general, STDs are epidemics and present an enormous health and economic consequences. An adequate screening for STDs should be done on a routine basis in every part of the world. Many STDs are asymptomatic and therefore can difficult to control. The purpose of reporting of STDs is to ensure that persons who are infected will be quickly diagnosed and appropriately treated to control the spread of infection and also so that partners are notified, tested and appropriately treated. It is estimated that reported cases of STDs represent only 50%-80% of reportable STD infections in the United States, reflecting limited screening and low disease reporting. High-risk sexual behavior is a highly contributive factor of this process as it often leads to teenage pregnancies and HIV/AIDS. One possible explanation for this behavior is that people do not have enough information about the transmission of STDs or ignore the precautions required for safe sex. Approximately 60% of new HIV infections worldwide occur in young people. The frequency of high-risk behaviors among youths may also be influenced by opportunity to engage in them, particularly the amount of time that they are unsupervised by adults. However, in diagnosing and treating these patients, we can effectively prevent the spread of HIV/AIDS. Individuals infected with STDs are 5-10 times more likely than uninfected individuals to acquire or transmit HIV through sexual contact. The breaking of the genital tract lining or skin creates a portal of entry for HIV and, hence, HIV-infected individuals with other STDs are more likely to shed HIV in their genital secretions. To date, the condom is the most effective method available for males for protection against STDs. It is important to control STDs, and prevention can be the key of this process. Prevention can be achieved through education of the population, identification of symptomatic and asymptomatic people, and effective diagnosis and treatment of these patients and their partners.
文摘INIRODUCIIONA newly discovered DNA virus,transfusiontransmitted virus (TTV),was reported as a cause ofpost-transfusion hepatitis of unknown etiology inJapan.In order to investigate TTV prevalence insouthern China,a study was carried out amongblood donors,patients with liver diseases andhemodialysis to determine the epidemiologicalcharateristics.
基金supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars, Ministry of Education of China (Grant No. 2007[24])supported by Science and Technology Project of Dalian (Grant No. 2008A16GX248)
文摘Surface or submerged horizontal or vertical plate can be considered as a new concept breakwater. This paper investigates the wave-plate interaction of this type of breakwater by use of the boundary element method. The relationships of wave transmitted and reflected among plate thickness, submergence and length are carefully studied by numerical simulation. It is shown that: (1) The transmitted coefficients of submerged horizontal plate or vertical plate will become larger with the increase of plate thickness and reduce rapidly with the decrease of plate submergence. (2) Both surface horizontal and vertical plate are efficient for intermediate and short wave elimination, but vertical plate is more effective. (3) Submerged horizontal plate can act more effectively than submerged vertical plate does. With all wave frequencies, the vertical plate almost has no wave elimination effect.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10901145)the Natural Science Foundation of Shanxi Province,China(Grant Nos. 2009011005-1 and 2012011002-1)the Top Young Academic Leaders of Higher Learning Institutions of Shanxi Province,China
文摘In this paper,a sexually transmitted disease model is proposed on complex networks,where contacts between humans are treated as a scale-free social network.There are three groups in our model,which are dangerous male,non-dangerous male,and female.By mathematical analysis,we obtain the basic reproduction number for the existence of endemic equilibrium and study the effects of various immunization schemes about different groups.Furthermore,numerical simulations are undertaken to verify more conclusions.
文摘Cancers in solid organ recipients may be classified as donor transmitted,donor derived,de novo or recurrent.The risk of donor-transmitted cancer is very low and can be reduced by careful screening of the donor but cannot be abolished and,in the United Kingdom series is less than 0.03%.For donors with a known history of cancer,the risks will depend on the nature of the cancer,the interventions given and the interval between diagnosis and organ donation.The risks of cancer transmission must be balanced against the risks of death awaiting a new graft and strict adherence to current guidelines may result increased patient death.Organs from selected patients,even with high-grade central nervous system(CNS)malignancy and after a shunt,can,in some circumstances,be considered.Of potential donors with non-CNS cancers,whether organs may be safely used again depends on the nature of the cancer,the treatment and interval.Data are scarce about the most appropriate treatment when donor transmitted cancer is diagnosed:sometimes substitution of agents and reduction of the immunosuppressive load may be adequate and the impact of graft removal should be considered but not always indicated.Liver al-lograft recipients are at increased risk of some de novo cancers,especially those grafted for alcohol-related liver disease and hepatitis C virus infection.The risk of lymphoproliferative disease and cancers of the skin,upper airway and bowel are increased but not breast.Recipients should be advised to avoid risk behavior and monitored appropriately.