Objective To investigate the performance of dual-source computed tomography （DSCT） using high-pitch spiral fliPS） mode for coronary stents patency. Methods We conducted a prospective study on 120 patients with 260 ...Objective To investigate the performance of dual-source computed tomography （DSCT） using high-pitch spiral fliPS） mode for coronary stents patency. Methods We conducted a prospective study on 120 patients with 260 previous stents implanted due to recurred suspicious symptoms of angina scheduled for invasive coronary angiography （ICA）, while DSCT were conducted using HPS mode. Results There was no significant impact of age, body mass index or heat rate （HR） on image quality （P 〉 0.05）, while HR variability had a slight impact on that （P 〈 0.05）. Sensitivity, specificity, positive predictive value （PPV）, negative predictive value （NPV） of DSCT in detection of in-stent restenosis （ISR） based per-patient were 92.3%, 96.7%, 88.9%, and 97.8%, respectively. And those based per-stent were 87%, 96.8%, 83.3%, and 97.7% with un-assessment stents, 97.4%, 99.5%, 97.4%, and 99.5% without un-assessment stents. There was significant differ- ence on sensitivity, specificity, PPV and NPV between diameter 〉 3.0 mm group （93.3%, 97.9%, 87.5%, and 98.9%） and diameter 〈 3.0 mm group （80%, 93.3%, 80.0%, and 93.3%） （P 〈 0.05）, and that between stent number 〉 3 group （82.3%, 77.8%, 66.7%, and 60%） with 〈 3 group （97.3%, 80%, 96.5%, and 75%）. The effective dose of DSCT （1.4 ± 0.5 mSv） is significantly less than that by invasive coronary angiography [4.0 ± 0.8 mSv （P 〈 0.01）]. Conclusion DSCT using HPS mode provides good diagnostic performance on stent patency with lower effective dose in patients with HR 〈 65 beats/rain.展开更多
Natural ventilation is driven by either buoyancy forces or wind pressure forces or their combinations that inherit stochastic variation into ventilation rates. Since the ventilation rate is a nonlinear function of mul...Natural ventilation is driven by either buoyancy forces or wind pressure forces or their combinations that inherit stochastic variation into ventilation rates. Since the ventilation rate is a nonlinear function of multiple variable factors including wind speed, wind direction, internal heat source and building structural thermal mass, the conventional methods for quantifying ventilation rate simply using dominant wind direction and average wind speed may not accurately describe the characteristic performance of natural ventilation. From a new point of view, the natural ventilation performance of a single room building under fluctuating wind speed condition using the Monte-Carlo simulation approach was investigated by incorporating building facade thermal mass effect. Given a same hourly turbulence intensity distribution, the wind speeds with 1 rain frequency fluctuations were generated using a stochastic model, the modified GARCH model. Comparisons of natural ventilation profiles, effective ventilation rates, and air conditioning electricity use for a three-month period show statistically significant differences （for 80% confidence interval） between the new calculations and the traditional methods based on hourly average wind speed.展开更多
In the near future, active safety systems will take more control over the vehicle driving, even up to introducing fully autonomous vehicles. Nowadays, it is expected that the active safety systems will aid avoiding co...In the near future, active safety systems will take more control over the vehicle driving, even up to introducing fully autonomous vehicles. Nowadays, it is expected that the active safety systems will aid avoiding collisions much more efficiently than human drivers. These systems can protect not only the passengers, but also other road users. To mitigate collision, certain maneuvers （e.g., sudden braking, lane change, etc.） need to be done in a reasonably quick time. However, this may lead to low-g energy pulses. The latter fact, may cause unexpected and, in some cases, unwanted occupant body motion resulting even in OOP （out of position） postures. New patterns of occupant reactions in such cases are, to some extent, confirmed experimentally [1-3]. This paper evaluates the limits of standard ATDs （anthropometric test devices） and chosen human models in well established maneuver scenarios. Obtained results are compared with experimental data available in the literature. Drawbacks identify new challenges for the near future simulation based safety engineering. One scenario with combined conditions of emergency braking during lane change has been used as an example of OOP posture after maneuver.展开更多
文摘Objective To investigate the performance of dual-source computed tomography （DSCT） using high-pitch spiral fliPS） mode for coronary stents patency. Methods We conducted a prospective study on 120 patients with 260 previous stents implanted due to recurred suspicious symptoms of angina scheduled for invasive coronary angiography （ICA）, while DSCT were conducted using HPS mode. Results There was no significant impact of age, body mass index or heat rate （HR） on image quality （P 〉 0.05）, while HR variability had a slight impact on that （P 〈 0.05）. Sensitivity, specificity, positive predictive value （PPV）, negative predictive value （NPV） of DSCT in detection of in-stent restenosis （ISR） based per-patient were 92.3%, 96.7%, 88.9%, and 97.8%, respectively. And those based per-stent were 87%, 96.8%, 83.3%, and 97.7% with un-assessment stents, 97.4%, 99.5%, 97.4%, and 99.5% without un-assessment stents. There was significant differ- ence on sensitivity, specificity, PPV and NPV between diameter 〉 3.0 mm group （93.3%, 97.9%, 87.5%, and 98.9%） and diameter 〈 3.0 mm group （80%, 93.3%, 80.0%, and 93.3%） （P 〈 0.05）, and that between stent number 〉 3 group （82.3%, 77.8%, 66.7%, and 60%） with 〈 3 group （97.3%, 80%, 96.5%, and 75%）. The effective dose of DSCT （1.4 ± 0.5 mSv） is significantly less than that by invasive coronary angiography [4.0 ± 0.8 mSv （P 〈 0.01）]. Conclusion DSCT using HPS mode provides good diagnostic performance on stent patency with lower effective dose in patients with HR 〈 65 beats/rain.
文摘Natural ventilation is driven by either buoyancy forces or wind pressure forces or their combinations that inherit stochastic variation into ventilation rates. Since the ventilation rate is a nonlinear function of multiple variable factors including wind speed, wind direction, internal heat source and building structural thermal mass, the conventional methods for quantifying ventilation rate simply using dominant wind direction and average wind speed may not accurately describe the characteristic performance of natural ventilation. From a new point of view, the natural ventilation performance of a single room building under fluctuating wind speed condition using the Monte-Carlo simulation approach was investigated by incorporating building facade thermal mass effect. Given a same hourly turbulence intensity distribution, the wind speeds with 1 rain frequency fluctuations were generated using a stochastic model, the modified GARCH model. Comparisons of natural ventilation profiles, effective ventilation rates, and air conditioning electricity use for a three-month period show statistically significant differences （for 80% confidence interval） between the new calculations and the traditional methods based on hourly average wind speed.
文摘In the near future, active safety systems will take more control over the vehicle driving, even up to introducing fully autonomous vehicles. Nowadays, it is expected that the active safety systems will aid avoiding collisions much more efficiently than human drivers. These systems can protect not only the passengers, but also other road users. To mitigate collision, certain maneuvers （e.g., sudden braking, lane change, etc.） need to be done in a reasonably quick time. However, this may lead to low-g energy pulses. The latter fact, may cause unexpected and, in some cases, unwanted occupant body motion resulting even in OOP （out of position） postures. New patterns of occupant reactions in such cases are, to some extent, confirmed experimentally [1-3]. This paper evaluates the limits of standard ATDs （anthropometric test devices） and chosen human models in well established maneuver scenarios. Obtained results are compared with experimental data available in the literature. Drawbacks identify new challenges for the near future simulation based safety engineering. One scenario with combined conditions of emergency braking during lane change has been used as an example of OOP posture after maneuver.
