Vector-to-raster conversion is a process accompanied with errors.The errors are classified into predicted errors before rasterization and actual errors after that.Accurate prediction of the errors is beneficial to dev...Vector-to-raster conversion is a process accompanied with errors.The errors are classified into predicted errors before rasterization and actual errors after that.Accurate prediction of the errors is beneficial to developing reasonable rasterization technical schemes and to making products of high quality.Analyzing and establishing a quantitative relationship between the error and its affecting factors is the key to error prediction.In this study,land cover data of China at a scale of 1:250 000 were taken as an example for analyzing the relationship between rasterization errors and the density of arc length(DA),the density of polygon(DP) and the size of grid cells(SG).Significant correlations were found between the errors and DA,DP and SG.The correlation coefficient(R2) of a model established based on samples collected in a small region(Beijing) reaches 0.95,and the value of R2 is equal to 0.91 while the model was validated with samples from the whole nation.On the other hand,the R2 of a model established based on nationwide samples reaches 0.96,and R2 is equal to 0.91 while it was validated with the samples in Beijing.These models depict well the relationships between rasterization errors and their affecting factors(DA,DP and SG).The analyzing method established in this study can be applied to effectively predicting rasterization errors in other cases as well.展开更多
The discrete iterative map model of peak current-mode controlled buck converter with constant current load（CCL）,containing the output voltage feedback and ramp compensation, is established in this paper. Based on th...The discrete iterative map model of peak current-mode controlled buck converter with constant current load（CCL）,containing the output voltage feedback and ramp compensation, is established in this paper. Based on this model the complex dynamics of this converter is investigated by analyzing bifurcation diagrams and the Lyapunov exponent spectrum. The effects of ramp compensation and output voltage feedback on the stability of the converter are investigated. Experimental results verify the simulation and theoretical analysis. The stability boundary and chaos boundary are obtained under the theoretical conditions of period-doubling bifurcation and border collision. It is found that there are four operation regions in the peak current-mode controlled buck converter with CCL due to period-doubling bifurcation and border-collision bifurcation. Research results indicate that ramp compensation can extend the stable operation range and transfer the operating mode, and output voltage feedback can eventually eliminate the coexisting fast-slow scale instability.展开更多
In this paper, we study the behavior of the solution at the crack edges for a nearly circular crack with developing cusps subject to shear loading. The problem of finding the resulting force can be written in the form...In this paper, we study the behavior of the solution at the crack edges for a nearly circular crack with developing cusps subject to shear loading. The problem of finding the resulting force can be written in the form of a hypersingular integral equation. The equation is then trans-formed into a similar equation over a circular region using conformal mapping. The equation is solved numerically for the unknown coefficients, which will later be used in finding the stress intensity factors. The sliding and tearing mode stress intensity factors are evaluated for cracks and displayed graphically. Our results seem to agree with the existing asymptotic solution.展开更多
A question about the analytical capability of Google maps is answered for three examples of pin maps, and polyline and polygon maps that are computer-programmed with the third version of the Google maps application. O...A question about the analytical capability of Google maps is answered for three examples of pin maps, and polyline and polygon maps that are computer-programmed with the third version of the Google maps application. One map reads XML data stored on the home server, whereas another downloads its data from an online fusion table, and the third includes pre-programmed data. Each map permits users to query mashup layers after the map has loaded. However, an analytical capability comparable to GIS should require users to have access to their data for analysis with their own functions while the map is loading. The technical constraint of asynchronous loading of data for Google maps is illustrated for each map. In conclusion, only one map has an analytical capability that is achieved by means of deprecated synchronous loading of data.展开更多
Skin integrity breakdown and pressure ulcer formation on the heel are predictable and preventable healthcare occurrences. By minimizing surface contact pressures that can cause heel capillary occlusion, heel off-loadi...Skin integrity breakdown and pressure ulcer formation on the heel are predictable and preventable healthcare occurrences. By minimizing surface contact pressures that can cause heel capillary occlusion, heel off-loading devices help mitigate the risk of decubitus ulceration. The purpose of this study is to investigate the efficacy of six off-loading methods commonly used in clinical settings to decrease heel contact pressure. Pressure mapping is used to evaluate contact pressure at the heel for underweight, normal weight, and overweight simulations. Based upon averages across four trials, it is shown that all devices reduce heel contact pressure when compared to no off-load- ing. The PRUventor™ boot exhibits significantly lower average pressure values than other off-load- ing strategies tested, suggesting that the PRUventor™ is the most effective off-loading device. From the analysis of the experimental data and comparison to similar data for respective off-loading alternatives, it is concluded that the PRUventor™ boot is an effective heel off-loading device for use in clinical settings.展开更多
基金Under the auspices of Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA05050000)Special Program for Informatization of Chinese Academy of Sciences(No.INF0-115-C01-SDB3-02)
文摘Vector-to-raster conversion is a process accompanied with errors.The errors are classified into predicted errors before rasterization and actual errors after that.Accurate prediction of the errors is beneficial to developing reasonable rasterization technical schemes and to making products of high quality.Analyzing and establishing a quantitative relationship between the error and its affecting factors is the key to error prediction.In this study,land cover data of China at a scale of 1:250 000 were taken as an example for analyzing the relationship between rasterization errors and the density of arc length(DA),the density of polygon(DP) and the size of grid cells(SG).Significant correlations were found between the errors and DA,DP and SG.The correlation coefficient(R2) of a model established based on samples collected in a small region(Beijing) reaches 0.95,and the value of R2 is equal to 0.91 while the model was validated with samples from the whole nation.On the other hand,the R2 of a model established based on nationwide samples reaches 0.96,and R2 is equal to 0.91 while it was validated with the samples in Beijing.These models depict well the relationships between rasterization errors and their affecting factors(DA,DP and SG).The analyzing method established in this study can be applied to effectively predicting rasterization errors in other cases as well.
基金Project supported by the National Natural Science Foundation of China(Grant No.61371033)the Fok Ying-Tung Education Foundation for Young Teachers in the Higher Education Institutions of China(Grant No.142027)+1 种基金the Sichuan Provincial Youth Science and Technology Fund,China(Grant Nos.2014JQ0015and 2013JQ0033)the Fundamental Research Funds for the Central Universities,China(Grant No.SWJTU11CX029)
文摘The discrete iterative map model of peak current-mode controlled buck converter with constant current load（CCL）,containing the output voltage feedback and ramp compensation, is established in this paper. Based on this model the complex dynamics of this converter is investigated by analyzing bifurcation diagrams and the Lyapunov exponent spectrum. The effects of ramp compensation and output voltage feedback on the stability of the converter are investigated. Experimental results verify the simulation and theoretical analysis. The stability boundary and chaos boundary are obtained under the theoretical conditions of period-doubling bifurcation and border collision. It is found that there are four operation regions in the peak current-mode controlled buck converter with CCL due to period-doubling bifurcation and border-collision bifurcation. Research results indicate that ramp compensation can extend the stable operation range and transfer the operating mode, and output voltage feedback can eventually eliminate the coexisting fast-slow scale instability.
基金supported by the Ministry Of Higher Education Malaysia for the Fundamental Research Grant scheme,project No. 01-04-10-897FRthe NSF scholarship
文摘In this paper, we study the behavior of the solution at the crack edges for a nearly circular crack with developing cusps subject to shear loading. The problem of finding the resulting force can be written in the form of a hypersingular integral equation. The equation is then trans-formed into a similar equation over a circular region using conformal mapping. The equation is solved numerically for the unknown coefficients, which will later be used in finding the stress intensity factors. The sliding and tearing mode stress intensity factors are evaluated for cracks and displayed graphically. Our results seem to agree with the existing asymptotic solution.
文摘A question about the analytical capability of Google maps is answered for three examples of pin maps, and polyline and polygon maps that are computer-programmed with the third version of the Google maps application. One map reads XML data stored on the home server, whereas another downloads its data from an online fusion table, and the third includes pre-programmed data. Each map permits users to query mashup layers after the map has loaded. However, an analytical capability comparable to GIS should require users to have access to their data for analysis with their own functions while the map is loading. The technical constraint of asynchronous loading of data for Google maps is illustrated for each map. In conclusion, only one map has an analytical capability that is achieved by means of deprecated synchronous loading of data.
文摘Skin integrity breakdown and pressure ulcer formation on the heel are predictable and preventable healthcare occurrences. By minimizing surface contact pressures that can cause heel capillary occlusion, heel off-loading devices help mitigate the risk of decubitus ulceration. The purpose of this study is to investigate the efficacy of six off-loading methods commonly used in clinical settings to decrease heel contact pressure. Pressure mapping is used to evaluate contact pressure at the heel for underweight, normal weight, and overweight simulations. Based upon averages across four trials, it is shown that all devices reduce heel contact pressure when compared to no off-load- ing. The PRUventor™ boot exhibits significantly lower average pressure values than other off-load- ing strategies tested, suggesting that the PRUventor™ is the most effective off-loading device. From the analysis of the experimental data and comparison to similar data for respective off-loading alternatives, it is concluded that the PRUventor™ boot is an effective heel off-loading device for use in clinical settings.
