Discusses block truncation coding (BTC) a simple and fast image compression technique suitable for real time image transmission with high channel error resisting capability and good reconstructed image quality, and it...Discusses block truncation coding (BTC) a simple and fast image compression technique suitable for real time image transmission with high channel error resisting capability and good reconstructed image quality, and its main drawback of high bit rate of 2 bits/pixel for a 256 gray image for the purpose of reducing the bit rate, and introduces a simple look up table method for coding the higher mean and the lower mean of a block, and a set of 24 visual patterns used to encode 4×4 bit plane of the high detail block and proposes a new algorithm, when needs only 19 bits to encode 4×4 high detail block and 12 bits to encode the 4×4 low detail block.展开更多
Objective To systemically explore the range of visual angles that affect visual acuity, and to establish the relationship between the P 1 component （peak latency -100 ms） of the pattern-reversal visual-evoked potent...Objective To systemically explore the range of visual angles that affect visual acuity, and to establish the relationship between the P 1 component （peak latency -100 ms） of the pattern-reversal visual-evoked potential （PRVEP） and the visual acuity at particular visual angles. Methods Two hundred and ten volunteers were divided into seven groups, according to visual acuity as assessed by the standard logarithmic visual acuity chart （SLD-II）. For each group, the PRVEP components were elicited in response to visual angle presentations at 8°, 4°, 2°, 1°/60＇, 30＇, 15＇, and 7.5＇, in the whiteblack chess-board reversal mode with a contrast level of 100% at a frequency of 2 Hz. Visual stimuli were presented monocularly, and 200 presentations were averaged for each block of trials. The early and stable component P1 was recorded at the mid-line of the occipital region （Oz） and analyzed with SPSS 13.00. Results （1） Oz had the maximum Pl amplitude; there was no significant difference between genders or for interocular comparison in normal controls and subjects with optic myopia. （2） The P1 latency decreased slowly below 30＇, then increased rapidly. The P1 amplitude initially increased with check size, and was maximal at -1° and -30＇. （3） The P1 latency in the group with visual acuity 〈0.2 was signifi- cantly different at 8°, 15＇ and 7.5＇, while the amplitude differed at all visual angles, compared with the group with normal vision. Differences in P1 for the groups with 0.5 and 0.6 acuity were only present at visual angles 〈1°. （4） Regression analysis showed that the P1 latency and amplitude were associated with visual acuity over the full range of visual angles. There was a moderate correlation at visual angles 〈30＇. Regression equations were calculated for the P1 components and visual acuity, based on visual angle. Conclusion （1） Visual angle should be taken into consideration when exploring the function of the visual pathway, especially visual acuity. A visual angle -60＇ might be appropriate when using PRVEP com- ponents to evaluate poor vision and to identify malingerers. （2） Increased P1 amplitude and decreased P1 latency were as- sociated with increasing visual acuity, and the P1 components displayed a linear correlation with visual acuity, especially in the range of optimal visual angles. Visual acuity can be deduced from P 1 based on visual angle.展开更多
Visual fire detection technologies can detect fire and alarm warnings earlier than conventional fire detectors. This study proposes an effective visual fire detection method that combines the statistical fire color mo...Visual fire detection technologies can detect fire and alarm warnings earlier than conventional fire detectors. This study proposes an effective visual fire detection method that combines the statistical fire color model and sequential pattern mining technology to detect fire in an image. Furthermore, the proposed method also supports real-time fire detection by integrating adaptive background subtraction technologies. Experimental results show that the proposed method can effectively detect fire in test images and videos. The detection accuracy of the proposed hybrid method is better than that of Celik＇s method.展开更多
AIM:To evaluate whether glaucomatous visual field defect particularly the pattern standard deviation(PSD)of Humphrey visual field could be associated with visual evoked potential(VEP)parameters of patients having prim...AIM:To evaluate whether glaucomatous visual field defect particularly the pattern standard deviation(PSD)of Humphrey visual field could be associated with visual evoked potential(VEP)parameters of patients having primary open angle glaucoma(POAG).METHODS:Visual field by Humphrey perimetry and simultaneous recordings of pattern reversal visual evoked potential(PRVEP)were assessed in 100 patients with POAG.The stimulus configuration for VEP recordings consisted of the transient pattern reversal method in which a black and white checker board pattern was generated(full field)and displayed on VEP monitor(colour 14')by an electronic pattern regenerator inbuilt in an evoked potential recorder(RMS EMG EP MARK II).RESULTS:The results of our study indicate that there is a highly significant(P【0.001)negative correlation of P100 amplitude and a statistically significant(P【0.05)positive correlation of N70 latency,P100 latency and N155 latency with the PSD of Humphrey visual field in the subjects of POAG in various age groups as evaluated by Student’s t-test.CONCLUSION:Prolongation of VEP latencies were mirrored by a corresponding increase of PSD values.Conversely,as PSD increases the magnitude of VEP excursions were found to be diminished.展开更多
Sensitivity analysis is a powerful method for discovering the significant factors that contribute to understanding the interaction between variables in multivariate datasets. A number of sensitivity analysis methods f...Sensitivity analysis is a powerful method for discovering the significant factors that contribute to understanding the interaction between variables in multivariate datasets. A number of sensitivity analysis methods fall into the class of local analysis, in which the sensitivity is defined as the partial derivatives of a target variable with respect to a group of independent variables. In a recent paper, we presented a novel pointwise local pattern exploration system for visual sensitivity analysis. Using this system, analysts are able to explore local patterns and the sensitivity at individual data points, which reveals the relationships between a focal point and its neighbors this paper we present several evaluations of the system, including case studies with real datasets, user studies the effectiveness of the visualizations and interactions, and a detailed description of the experience of a user In on展开更多
In order to explore the travel characteristics and space-time distribution of different groups of bikeshare users,an online analytical processing(OLAP)tool called data cube was used for treating and displaying multi-d...In order to explore the travel characteristics and space-time distribution of different groups of bikeshare users,an online analytical processing(OLAP)tool called data cube was used for treating and displaying multi-dimensional data.We extended and modified the traditionally threedimensional data cube into four dimensions,which are space,date,time,and user,each with a user-specified hierarchy,and took transaction numbers and travel time as two quantitative measures.The results suggest that there are two obvious transaction peaks during the morning and afternoon rush hours on weekdays,while the volume at weekends has an approximate even distribution.Bad weather condition significantly restricts the bikeshare usage.Besides,seamless smartcard users generally take a longer trip than exclusive smartcard users;and non-native users ride faster than native users.These findings not only support the applicability and efficiency of data cube in the field of visualizing massive smartcard data,but also raise equity concerns among bikeshare users with different demographic backgrounds.展开更多
Purposes: To observe the characteristics of local electroretinogram (LERG) in normal subjects and patients with maculopathies, and to evaluate the applied worth of LERG and pattern visual evoked potential (PVEP) in ma...Purposes: To observe the characteristics of local electroretinogram (LERG) in normal subjects and patients with maculopathies, and to evaluate the applied worth of LERG and pattern visual evoked potential (PVEP) in maculopathies. Methods: LERGs at 5° and 15° macular regions were recorded from 27 normal subjects (54 eyes). The factors of age, different eyes and stimulate areas for LERG influence were observed. Meanwhile, the LERG and PVEP were recorded from 25 patients (35 eyes) with maculopathies for making contrast study. Results: In normal subjects, there was no significant influence of age to LERG. As the stimulated areas increased, the a- and b-wave amplitudes of LERG increased. In the patients with maculopathies, the a- and b-wave amplitudes of LERG at 5°, 10°and 15° macular regions were significantly lowered and the mean values of P1 latency were prolonged and N1-P1 amplitudes of VEP were lowered, comparing with the control group. In the nearing stimulated area (5°LERG and 14. 9×19°PVEP.),展开更多
近年来随着无人机产业的迅猛发展,视觉定位技术已广泛应用于低成本轻量化的定位系统中,然而当无人机在水面等弱纹理区域飞行时,场景视觉特征稀疏且差异小,导致图像误匹配率激增,定位估计发散严重,限制了视觉定位技术在水域环境下的应用...近年来随着无人机产业的迅猛发展,视觉定位技术已广泛应用于低成本轻量化的定位系统中,然而当无人机在水面等弱纹理区域飞行时,场景视觉特征稀疏且差异小,导致图像误匹配率激增,定位估计发散严重,限制了视觉定位技术在水域环境下的应用。针对该问题提出了一种基于水纹识别的视觉定位技术(visual positioning technique based on water pattern recognition,WPRVP)。首先通过提取水纹多粒度相关特征得到相邻图像之间局部和全局的匹配关系;然后将匹配信息嵌入循环网络迭代处理,由粗到细逐步提高水纹图像的匹配精度;最后基于多视图几何约束进行匹配筛选和运动建模,实现了鲁棒的定位估计。实验结果表明,相比现有的图像匹配和视觉定位方法,WPRVP能够应用于水域环境且能保持更高的匹配与定位精度,能够为导航设备在水域场景下提供一个低成本高精度的导航信息源,辅助无人机执行水面飞行任务。展开更多
The present work is a visualization study of a typical kerosene （RP-3） flowing through vertical and horizontal quartz-glass tubes under both sub- and supercritical conditions by a high speed camera. The experiments ...The present work is a visualization study of a typical kerosene （RP-3） flowing through vertical and horizontal quartz-glass tubes under both sub- and supercritical conditions by a high speed camera. The experiments are accomplished at temperatures of 300-730 K under pressures from 0.107-5 MPa. Six distinctive two-phase flow patterns are observed in upward flow and the critical point of RP-3 is identified as critical pressure pc=2.33 MPa and critical temperature Tc=645.04 K and it is found that when the fluid pressure exceeds 2.33 MPa the flow can be considered as a single phase flow. The critical opalescence phenomenon of RP-3 is observed when the temperature is between 643.16 K and 648.61 K and the pressure is between 2.308 MPa and 2.366 MPa. The region filled by the critical opalescence in the upward flow is clearly larger than that in the downward flow due to the interaction between the buoyancy force and fluid inertia. Morecover, obvious layered flow phenomenon is observed in horizontal flow under supercritical pressures due to the differences of gravity and density.展开更多
The changing pattern of the Lower Yellow River （LYR） obtained from the traditional studies, which mainly did literal analysis based on historical documents related to the LYR are too macroscopic and absent of intuit...The changing pattern of the Lower Yellow River （LYR） obtained from the traditional studies, which mainly did literal analysis based on historical documents related to the LYR are too macroscopic and absent of intuitiveness. This paper integrates all the records in historical documents related to course shift, flood and overflow of the last 3000 years and stores them in a GIS database. Then, all the data will be visualized in the form of map, which is helpful to show and understand the rules those events conform more intuitively and accurately. Taking these data as foundation, this study summarizes characteristics of the LYR＇s courses and influence scope, and classifies them both into three types; divides the flow directions of the LYR＇s courses into two periods, and proposes its changing pattern; concludes the character- istic of diversion points of courses shift events; calculates the velocity of courses shifts, gra- dient and sinuosity, and analyzes their changing patterns. Finally, this study classifies factors that may influence the occurrence of a course shift into two types： the internal factors, such as sediment rate, gradient and sinuosity of the river, and the external factors, such as precipita- tion and human activities.展开更多
AIM: To explore changes and possible communication relationship of local potential signals recorded simultaneously from retina and visual cortex I(V1).·METHODS: Fourteen C57BL/6J mice were measured with pattern e...AIM: To explore changes and possible communication relationship of local potential signals recorded simultaneously from retina and visual cortex I(V1).·METHODS: Fourteen C57BL/6J mice were measured with pattern electroretinogram(PERG) and pattern visually evoked potential(PVEP) and fast Fourier transform has been used to analyze the frequency components of those signals.· RESULTS: The amplitude of PERG and PVEP was measured at about 36.7 μV and 112.5 μV respectively and the dominant frequency of PERG and PVEP, however,stay unchanged and both signals do not have second, or otherwise, harmonic generation.· CONCLUSION: The results suggested that retina encodes visual information in the way of frequency spectrum and then transfers it to primary visual cortex.The primary visual cortex accepts and deciphers the input visual information coded from retina. Frequency spectrum may act as communication code between retina and V1.展开更多
A method for creating digital image copyright protection is proposed in this paper. The proposed method in this paper is based on visual cryptography defined by Noor and Shamir. The proposed method is working on selec...A method for creating digital image copyright protection is proposed in this paper. The proposed method in this paper is based on visual cryptography defined by Noor and Shamir. The proposed method is working on selection of random pixels from the original digital image instead of specific selection of pixels. The new method proposed does not require that the watermark pattern to be embedded in to the original digital image. Instead of that, verification information is generated which will be used to verify the ownership of the image. This leaves the marked image equal to the original image. The method is based on the relationship between randomly selected pixels and their 8-neighbors’ pixels. This relationship keeps the marked image coherent against diverse attacks even if the most significant bits of randomly selected pixels have been changed by attacker as we will see later in this paper. Experimental results show the proposed method can recover the watermark pattern from the marked image even if major changes are made to the original digital image.展开更多
Visual functions and nutrition metabolic characteristics werestudied in 8 subjects(16 eyes)with tobacco-toxic optic neuropathy(TTON).Their visual functions tested by psychophysical and electrophysiologicmethods showed...Visual functions and nutrition metabolic characteristics werestudied in 8 subjects(16 eyes)with tobacco-toxic optic neuropathy(TTON).Their visual functions tested by psychophysical and electrophysiologicmethods showed that:1.central vision diminished in 16 eyes,2.dyschromatopsias were found in 14 tested eyes,3.bilateral symmetricalcentral or cecocentral scotomas were the visual field characteristics in allcases,4.PVEP were severe abnormal in 3 spatial frequencies in all cases and56.3% of 15' checkboard ...展开更多
This work develops a system to visualize the information for radar systems interfaces. It is a flexible, portable software system that allows to be used for radars that have different technologies and that is able to ...This work develops a system to visualize the information for radar systems interfaces. It is a flexible, portable software system that allows to be used for radars that have different technologies and that is able to be adapted to the specific needs of each application domain in an efficient way. Replacing the visualization and processing units on existing radar platforms by this new system, a practical and inexpensive improvement is achieved.展开更多
By means of flow visualization on the wall surface and three dimensional flow field numerical simulation for the turbine cascade with 3.6% relative tip clearance, characteristics of the wall flow of the turbine cascad...By means of flow visualization on the wall surface and three dimensional flow field numerical simulation for the turbine cascade with 3.6% relative tip clearance, characteristics of the wall flow of the turbine cascade with large tip clearance is analyzed. The flow pattern on the wall surface near the trailing edge is especially discussed in detail by numerical simulation. Results of the experimental and numerical simulation show that the flow near the cascade trailing edge is very complex, and the wall flow patterns near the upper and down trailing edges are clearly different due to the influence of blade tip clearance.展开更多
To determine the type of surface roughness pattern that is suitable for adaptive suppression of the drag of an obstacle, we observed flow structures introduced by such obstacles. Several roughness patterns were tested...To determine the type of surface roughness pattern that is suitable for adaptive suppression of the drag of an obstacle, we observed flow structures introduced by such obstacles. Several roughness patterns were tested: geometric patterns, fractal patterns, reptile-skin patterns, and patterns of circular cylinders arranged in a lattice and in a zigzag manner. A suitable pattern for adaptive control of flow is one that generates longitudinal vortices with nonconstant distances. The preferred instability mode of a laminar boundary layer is expected to be selected automatically from fluctuations involving many frequencies and caused by fractal patterns. Snake- and reptile-skin patterns may have a similar ability as fractal patterns because they consist of multiscale patterns. The longitudinal vortices generated from peculiar positions and concave corners in patterns were observed. The distance between these vortices is not constant because the onset of vortices is at concave corners in fractal patterns. These vortices have differing strengths and easily cause nonlinear interactions, so they can disturb a laminar boundary layer with several higher-harmonic frequencies. The velocity profiles of the laminar boundary-layer flow over the fractal patterns were measured by using hydrogen bubbles. The results show the down-wash flow between the longitudinal vortices, which means that the vortices may effectively suppress the boundary layer separation in an adverse pressure gradient.展开更多
文摘Discusses block truncation coding (BTC) a simple and fast image compression technique suitable for real time image transmission with high channel error resisting capability and good reconstructed image quality, and its main drawback of high bit rate of 2 bits/pixel for a 256 gray image for the purpose of reducing the bit rate, and introduces a simple look up table method for coding the higher mean and the lower mean of a block, and a set of 24 visual patterns used to encode 4×4 bit plane of the high detail block and proposes a new algorithm, when needs only 19 bits to encode 4×4 high detail block and 12 bits to encode the 4×4 low detail block.
基金supported by grants from the National Nature Science Foundation of China(30872666,81172911 and 81271379)Shanghai Key Lab of Forensic Medicine(KF1005)
文摘Objective To systemically explore the range of visual angles that affect visual acuity, and to establish the relationship between the P 1 component （peak latency -100 ms） of the pattern-reversal visual-evoked potential （PRVEP） and the visual acuity at particular visual angles. Methods Two hundred and ten volunteers were divided into seven groups, according to visual acuity as assessed by the standard logarithmic visual acuity chart （SLD-II）. For each group, the PRVEP components were elicited in response to visual angle presentations at 8°, 4°, 2°, 1°/60＇, 30＇, 15＇, and 7.5＇, in the whiteblack chess-board reversal mode with a contrast level of 100% at a frequency of 2 Hz. Visual stimuli were presented monocularly, and 200 presentations were averaged for each block of trials. The early and stable component P1 was recorded at the mid-line of the occipital region （Oz） and analyzed with SPSS 13.00. Results （1） Oz had the maximum Pl amplitude; there was no significant difference between genders or for interocular comparison in normal controls and subjects with optic myopia. （2） The P1 latency decreased slowly below 30＇, then increased rapidly. The P1 amplitude initially increased with check size, and was maximal at -1° and -30＇. （3） The P1 latency in the group with visual acuity 〈0.2 was signifi- cantly different at 8°, 15＇ and 7.5＇, while the amplitude differed at all visual angles, compared with the group with normal vision. Differences in P1 for the groups with 0.5 and 0.6 acuity were only present at visual angles 〈1°. （4） Regression analysis showed that the P1 latency and amplitude were associated with visual acuity over the full range of visual angles. There was a moderate correlation at visual angles 〈30＇. Regression equations were calculated for the P1 components and visual acuity, based on visual angle. Conclusion （1） Visual angle should be taken into consideration when exploring the function of the visual pathway, especially visual acuity. A visual angle -60＇ might be appropriate when using PRVEP com- ponents to evaluate poor vision and to identify malingerers. （2） Increased P1 amplitude and decreased P1 latency were as- sociated with increasing visual acuity, and the P1 components displayed a linear correlation with visual acuity, especially in the range of optimal visual angles. Visual acuity can be deduced from P 1 based on visual angle.
基金supported by National Science Council under Grant No. NSC98-2221-E-218-046
文摘Visual fire detection technologies can detect fire and alarm warnings earlier than conventional fire detectors. This study proposes an effective visual fire detection method that combines the statistical fire color model and sequential pattern mining technology to detect fire in an image. Furthermore, the proposed method also supports real-time fire detection by integrating adaptive background subtraction technologies. Experimental results show that the proposed method can effectively detect fire in test images and videos. The detection accuracy of the proposed hybrid method is better than that of Celik＇s method.
文摘AIM:To evaluate whether glaucomatous visual field defect particularly the pattern standard deviation(PSD)of Humphrey visual field could be associated with visual evoked potential(VEP)parameters of patients having primary open angle glaucoma(POAG).METHODS:Visual field by Humphrey perimetry and simultaneous recordings of pattern reversal visual evoked potential(PRVEP)were assessed in 100 patients with POAG.The stimulus configuration for VEP recordings consisted of the transient pattern reversal method in which a black and white checker board pattern was generated(full field)and displayed on VEP monitor(colour 14')by an electronic pattern regenerator inbuilt in an evoked potential recorder(RMS EMG EP MARK II).RESULTS:The results of our study indicate that there is a highly significant(P【0.001)negative correlation of P100 amplitude and a statistically significant(P【0.05)positive correlation of N70 latency,P100 latency and N155 latency with the PSD of Humphrey visual field in the subjects of POAG in various age groups as evaluated by Student’s t-test.CONCLUSION:Prolongation of VEP latencies were mirrored by a corresponding increase of PSD values.Conversely,as PSD increases the magnitude of VEP excursions were found to be diminished.
基金Supported by the National Science Foundation of USA (No.IIS-0812027)
文摘Sensitivity analysis is a powerful method for discovering the significant factors that contribute to understanding the interaction between variables in multivariate datasets. A number of sensitivity analysis methods fall into the class of local analysis, in which the sensitivity is defined as the partial derivatives of a target variable with respect to a group of independent variables. In a recent paper, we presented a novel pointwise local pattern exploration system for visual sensitivity analysis. Using this system, analysts are able to explore local patterns and the sensitivity at individual data points, which reveals the relationships between a focal point and its neighbors this paper we present several evaluations of the system, including case studies with real datasets, user studies the effectiveness of the visualizations and interactions, and a detailed description of the experience of a user In on
基金Supported by Projects of International Cooperation and Exchange of the National Natural Science Foundation of China(51561135003)Key Project of National Natural Science Foundation of China(51338003)Scientific Research Foundation of Graduated School of Southeast University(YBJJ1842)
文摘In order to explore the travel characteristics and space-time distribution of different groups of bikeshare users,an online analytical processing(OLAP)tool called data cube was used for treating and displaying multi-dimensional data.We extended and modified the traditionally threedimensional data cube into four dimensions,which are space,date,time,and user,each with a user-specified hierarchy,and took transaction numbers and travel time as two quantitative measures.The results suggest that there are two obvious transaction peaks during the morning and afternoon rush hours on weekdays,while the volume at weekends has an approximate even distribution.Bad weather condition significantly restricts the bikeshare usage.Besides,seamless smartcard users generally take a longer trip than exclusive smartcard users;and non-native users ride faster than native users.These findings not only support the applicability and efficiency of data cube in the field of visualizing massive smartcard data,but also raise equity concerns among bikeshare users with different demographic backgrounds.
文摘Purposes: To observe the characteristics of local electroretinogram (LERG) in normal subjects and patients with maculopathies, and to evaluate the applied worth of LERG and pattern visual evoked potential (PVEP) in maculopathies. Methods: LERGs at 5° and 15° macular regions were recorded from 27 normal subjects (54 eyes). The factors of age, different eyes and stimulate areas for LERG influence were observed. Meanwhile, the LERG and PVEP were recorded from 25 patients (35 eyes) with maculopathies for making contrast study. Results: In normal subjects, there was no significant influence of age to LERG. As the stimulated areas increased, the a- and b-wave amplitudes of LERG increased. In the patients with maculopathies, the a- and b-wave amplitudes of LERG at 5°, 10°and 15° macular regions were significantly lowered and the mean values of P1 latency were prolonged and N1-P1 amplitudes of VEP were lowered, comparing with the control group. In the nearing stimulated area (5°LERG and 14. 9×19°PVEP.),
文摘近年来随着无人机产业的迅猛发展,视觉定位技术已广泛应用于低成本轻量化的定位系统中,然而当无人机在水面等弱纹理区域飞行时,场景视觉特征稀疏且差异小,导致图像误匹配率激增,定位估计发散严重,限制了视觉定位技术在水域环境下的应用。针对该问题提出了一种基于水纹识别的视觉定位技术(visual positioning technique based on water pattern recognition,WPRVP)。首先通过提取水纹多粒度相关特征得到相邻图像之间局部和全局的匹配关系;然后将匹配信息嵌入循环网络迭代处理,由粗到细逐步提高水纹图像的匹配精度;最后基于多视图几何约束进行匹配筛选和运动建模,实现了鲁棒的定位估计。实验结果表明,相比现有的图像匹配和视觉定位方法,WPRVP能够应用于水域环境且能保持更高的匹配与定位精度,能够为导航设备在水域场景下提供一个低成本高精度的导航信息源,辅助无人机执行水面飞行任务。
基金National Natural Science Foundation of China(50676005)
文摘The present work is a visualization study of a typical kerosene （RP-3） flowing through vertical and horizontal quartz-glass tubes under both sub- and supercritical conditions by a high speed camera. The experiments are accomplished at temperatures of 300-730 K under pressures from 0.107-5 MPa. Six distinctive two-phase flow patterns are observed in upward flow and the critical point of RP-3 is identified as critical pressure pc=2.33 MPa and critical temperature Tc=645.04 K and it is found that when the fluid pressure exceeds 2.33 MPa the flow can be considered as a single phase flow. The critical opalescence phenomenon of RP-3 is observed when the temperature is between 643.16 K and 648.61 K and the pressure is between 2.308 MPa and 2.366 MPa. The region filled by the critical opalescence in the upward flow is clearly larger than that in the downward flow due to the interaction between the buoyancy force and fluid inertia. Morecover, obvious layered flow phenomenon is observed in horizontal flow under supercritical pressures due to the differences of gravity and density.
基金Project supported by the Ministry of Science and Technology of China, No.2009BAH50B01No.2008BAK50B05
文摘The changing pattern of the Lower Yellow River （LYR） obtained from the traditional studies, which mainly did literal analysis based on historical documents related to the LYR are too macroscopic and absent of intuitiveness. This paper integrates all the records in historical documents related to course shift, flood and overflow of the last 3000 years and stores them in a GIS database. Then, all the data will be visualized in the form of map, which is helpful to show and understand the rules those events conform more intuitively and accurately. Taking these data as foundation, this study summarizes characteristics of the LYR＇s courses and influence scope, and classifies them both into three types; divides the flow directions of the LYR＇s courses into two periods, and proposes its changing pattern; concludes the character- istic of diversion points of courses shift events; calculates the velocity of courses shifts, gra- dient and sinuosity, and analyzes their changing patterns. Finally, this study classifies factors that may influence the occurrence of a course shift into two types： the internal factors, such as sediment rate, gradient and sinuosity of the river, and the external factors, such as precipita- tion and human activities.
基金Supported by 973 Program of the Ministry of Science and Technology of China (No.2013CB967101)Shanghai Science Committee Foundation (No.13PJ1433200)
文摘AIM: To explore changes and possible communication relationship of local potential signals recorded simultaneously from retina and visual cortex I(V1).·METHODS: Fourteen C57BL/6J mice were measured with pattern electroretinogram(PERG) and pattern visually evoked potential(PVEP) and fast Fourier transform has been used to analyze the frequency components of those signals.· RESULTS: The amplitude of PERG and PVEP was measured at about 36.7 μV and 112.5 μV respectively and the dominant frequency of PERG and PVEP, however,stay unchanged and both signals do not have second, or otherwise, harmonic generation.· CONCLUSION: The results suggested that retina encodes visual information in the way of frequency spectrum and then transfers it to primary visual cortex.The primary visual cortex accepts and deciphers the input visual information coded from retina. Frequency spectrum may act as communication code between retina and V1.
文摘A method for creating digital image copyright protection is proposed in this paper. The proposed method in this paper is based on visual cryptography defined by Noor and Shamir. The proposed method is working on selection of random pixels from the original digital image instead of specific selection of pixels. The new method proposed does not require that the watermark pattern to be embedded in to the original digital image. Instead of that, verification information is generated which will be used to verify the ownership of the image. This leaves the marked image equal to the original image. The method is based on the relationship between randomly selected pixels and their 8-neighbors’ pixels. This relationship keeps the marked image coherent against diverse attacks even if the most significant bits of randomly selected pixels have been changed by attacker as we will see later in this paper. Experimental results show the proposed method can recover the watermark pattern from the marked image even if major changes are made to the original digital image.
基金This study was supported by Zhongshan ophthalmic Center,SUMS.
文摘Visual functions and nutrition metabolic characteristics werestudied in 8 subjects(16 eyes)with tobacco-toxic optic neuropathy(TTON).Their visual functions tested by psychophysical and electrophysiologicmethods showed that:1.central vision diminished in 16 eyes,2.dyschromatopsias were found in 14 tested eyes,3.bilateral symmetricalcentral or cecocentral scotomas were the visual field characteristics in allcases,4.PVEP were severe abnormal in 3 spatial frequencies in all cases and56.3% of 15' checkboard ...
文摘This work develops a system to visualize the information for radar systems interfaces. It is a flexible, portable software system that allows to be used for radars that have different technologies and that is able to be adapted to the specific needs of each application domain in an efficient way. Replacing the visualization and processing units on existing radar platforms by this new system, a practical and inexpensive improvement is achieved.
文摘By means of flow visualization on the wall surface and three dimensional flow field numerical simulation for the turbine cascade with 3.6% relative tip clearance, characteristics of the wall flow of the turbine cascade with large tip clearance is analyzed. The flow pattern on the wall surface near the trailing edge is especially discussed in detail by numerical simulation. Results of the experimental and numerical simulation show that the flow near the cascade trailing edge is very complex, and the wall flow patterns near the upper and down trailing edges are clearly different due to the influence of blade tip clearance.
文摘To determine the type of surface roughness pattern that is suitable for adaptive suppression of the drag of an obstacle, we observed flow structures introduced by such obstacles. Several roughness patterns were tested: geometric patterns, fractal patterns, reptile-skin patterns, and patterns of circular cylinders arranged in a lattice and in a zigzag manner. A suitable pattern for adaptive control of flow is one that generates longitudinal vortices with nonconstant distances. The preferred instability mode of a laminar boundary layer is expected to be selected automatically from fluctuations involving many frequencies and caused by fractal patterns. Snake- and reptile-skin patterns may have a similar ability as fractal patterns because they consist of multiscale patterns. The longitudinal vortices generated from peculiar positions and concave corners in patterns were observed. The distance between these vortices is not constant because the onset of vortices is at concave corners in fractal patterns. These vortices have differing strengths and easily cause nonlinear interactions, so they can disturb a laminar boundary layer with several higher-harmonic frequencies. The velocity profiles of the laminar boundary-layer flow over the fractal patterns were measured by using hydrogen bubbles. The results show the down-wash flow between the longitudinal vortices, which means that the vortices may effectively suppress the boundary layer separation in an adverse pressure gradient.
