When evaluating the accessibility of a large website, we rely on sampling methods to reduce the cost of evaluation. This may lead to a biased evaluation when the distribution of checkpoint violations in a website is s...When evaluating the accessibility of a large website, we rely on sampling methods to reduce the cost of evaluation. This may lead to a biased evaluation when the distribution of checkpoint violations in a website is skewed and the selected samples do not provide a good representation of the entire website. To improve sampling quality, stratified sampling methods first cluster web pages in a site and then draw samples from each cluster. In existing stratified sampling methods, however, all the pages in a website need to be analyzed for clustering, causing huge I/O and computation costs. To address this issue, we propose a novel page sampling method based on URL clustering for web accessibility evaluation, namely URLSamp. Using only the URL information for stratified page sampling, URLSamp can efficiently scale to large websites. Meanwhile, by exploiting similarities in URL patterns, URLSamp cluster pages by their generating scripts and can thus effectively detect accessibility problems from web page templates. We use a data set of 45 web sites to validate our method. Experimental results show that our URLSamp method is both effective and efficient for web accessibility evaluation.展开更多
Public transportation(PT)often fails to provide door-to-door service.Passengers often have to walk a distance to reach their destination after getting off the public transportation station.Therefore,the walking access...Public transportation(PT)often fails to provide door-to-door service.Passengers often have to walk a distance to reach their destination after getting off the public transportation station.Therefore,the walking accessibility of the station area directly affects the attractiveness of the PT.For walking,accurate calculation or prediction of accessibility should consider not only the objective distance,but also the environment and psychological perception factors of pedestrians.This paper aims to map the pedestrian perceived cost to the transportation environment to evaluate the walking accessibility of the public transportation station area accurately.From the perspective of psychological perception of walking environment,four key impedance factors are selected and a pedestrian perceived impedance model is established.Then an evaluation model of station area accessibility is set employing POIs(Point of Interests)based on the accumulative opportunity method.Finally,the case is given to show the application of the model.The results show that the number of crosswalks with signal lights,mixed use of sidewalk and non-motorized lane,the obstacle quantity and the vehicle entrance quantity on sidewalks can increase perceived impedance significantly.For example,pedestrians are willing to spend 4.21 extra minutes to adopt routes with one fewer obstacle per 100 meters.Within 10 minutes of walking time,walking perception has a greater impact on station area accessibility.The perceived walking time thresholds for evaluating bus and rail transit station area accessibility are recommended to be 15 minutes and 20 minutes,respectively.The evaluation results can provide a reliable basis for improving the walking network around public transportation station.展开更多
Background The need to develop new methods of surgical training combined with advances in computing has led to the development of virtual reality surgical simulators. The PERC MentorTM is designed to train the user in...Background The need to develop new methods of surgical training combined with advances in computing has led to the development of virtual reality surgical simulators. The PERC MentorTM is designed to train the user in percutaneous renal collecting system access puncture. This study aimed to validate the use of this kind of simulator, in percutaneous renal access training. Methods Twenty-one urologists were enrolled as trainees to learn a fluoroscopy-guided percutaneous renal accessing technique. An assigned percutaneous renal access procedure was immediately performed on the PERC MentorTM after watching instruction video and an analog operation. Objective parameters were recorded by the simulator and subjective global rating scale （GRS） score were determined. Simulation training followed and consisted of 2 hours daily training sessions for 2 consecutive days. Twenty-four hours after the training session, trainees were evaluated performing the same procedure. The post-training evaluation was compared to the evaluation of the initial attempt. Results During the initial attempt, none of the trainees could complete the appointed procedure due to the lack of experience in fluoroscopy-guided percutaneous renal access. After the short-term training, all trainees were able to independently complete the procedure. Of the 21 trainees, 10 had primitive experience in ultrasound-guided percutaneous nephrolithotomy. Trainees were thus categorized into the group of primitive experience and inexperience. The total operating time and amount of contrast material used were significantly lower in the group of primitive experience versus the inexperience group （P=0.03 and 0.02, respectively）. Conclusions The training on the virtual reality simulator, PERC MentorTM, can help trainees with no previous experience of fluoroscopy-guided percutaneous renal access to complete the virtual manipulation of the procedure independently. This virtual reality simulator may become an important training and evaluation tool in teaching fluoroscopy-guided percutaneous renal access.展开更多
基金Project supported by the National Natural Science Foundation of China （Nos. 61173185 and 61173186） and the Natural Science Foun- dation of Zhejiang Province, China （No. LZ13F020001）
文摘When evaluating the accessibility of a large website, we rely on sampling methods to reduce the cost of evaluation. This may lead to a biased evaluation when the distribution of checkpoint violations in a website is skewed and the selected samples do not provide a good representation of the entire website. To improve sampling quality, stratified sampling methods first cluster web pages in a site and then draw samples from each cluster. In existing stratified sampling methods, however, all the pages in a website need to be analyzed for clustering, causing huge I/O and computation costs. To address this issue, we propose a novel page sampling method based on URL clustering for web accessibility evaluation, namely URLSamp. Using only the URL information for stratified page sampling, URLSamp can efficiently scale to large websites. Meanwhile, by exploiting similarities in URL patterns, URLSamp cluster pages by their generating scripts and can thus effectively detect accessibility problems from web page templates. We use a data set of 45 web sites to validate our method. Experimental results show that our URLSamp method is both effective and efficient for web accessibility evaluation.
基金supported the National Social Science Found of China(No.20BGL291).
文摘Public transportation(PT)often fails to provide door-to-door service.Passengers often have to walk a distance to reach their destination after getting off the public transportation station.Therefore,the walking accessibility of the station area directly affects the attractiveness of the PT.For walking,accurate calculation or prediction of accessibility should consider not only the objective distance,but also the environment and psychological perception factors of pedestrians.This paper aims to map the pedestrian perceived cost to the transportation environment to evaluate the walking accessibility of the public transportation station area accurately.From the perspective of psychological perception of walking environment,four key impedance factors are selected and a pedestrian perceived impedance model is established.Then an evaluation model of station area accessibility is set employing POIs(Point of Interests)based on the accumulative opportunity method.Finally,the case is given to show the application of the model.The results show that the number of crosswalks with signal lights,mixed use of sidewalk and non-motorized lane,the obstacle quantity and the vehicle entrance quantity on sidewalks can increase perceived impedance significantly.For example,pedestrians are willing to spend 4.21 extra minutes to adopt routes with one fewer obstacle per 100 meters.Within 10 minutes of walking time,walking perception has a greater impact on station area accessibility.The perceived walking time thresholds for evaluating bus and rail transit station area accessibility are recommended to be 15 minutes and 20 minutes,respectively.The evaluation results can provide a reliable basis for improving the walking network around public transportation station.
文摘Background The need to develop new methods of surgical training combined with advances in computing has led to the development of virtual reality surgical simulators. The PERC MentorTM is designed to train the user in percutaneous renal collecting system access puncture. This study aimed to validate the use of this kind of simulator, in percutaneous renal access training. Methods Twenty-one urologists were enrolled as trainees to learn a fluoroscopy-guided percutaneous renal accessing technique. An assigned percutaneous renal access procedure was immediately performed on the PERC MentorTM after watching instruction video and an analog operation. Objective parameters were recorded by the simulator and subjective global rating scale （GRS） score were determined. Simulation training followed and consisted of 2 hours daily training sessions for 2 consecutive days. Twenty-four hours after the training session, trainees were evaluated performing the same procedure. The post-training evaluation was compared to the evaluation of the initial attempt. Results During the initial attempt, none of the trainees could complete the appointed procedure due to the lack of experience in fluoroscopy-guided percutaneous renal access. After the short-term training, all trainees were able to independently complete the procedure. Of the 21 trainees, 10 had primitive experience in ultrasound-guided percutaneous nephrolithotomy. Trainees were thus categorized into the group of primitive experience and inexperience. The total operating time and amount of contrast material used were significantly lower in the group of primitive experience versus the inexperience group （P=0.03 and 0.02, respectively）. Conclusions The training on the virtual reality simulator, PERC MentorTM, can help trainees with no previous experience of fluoroscopy-guided percutaneous renal access to complete the virtual manipulation of the procedure independently. This virtual reality simulator may become an important training and evaluation tool in teaching fluoroscopy-guided percutaneous renal access.
