Modeling the runout behavior of the July 23rd, 2015 Cancia debris-flow event using two numerical models

On 23 July 2015, a typical volume-enlarging debris flow was triggered by heavy rainfall that occurred a few days before the event. The available data corresponding to this event is obtained from detailed field investigations conducted before and after the event, as well as the monitoring station installed in June 2014. This study aims to reproduce the July 23 debris-flow event using two different numerical methods, analyse the influence of entrainment on the runout behavior of the debris flow and compare the performance of different numerical methods when simulating the same debris-flow event. The results showed the following: (1) The expanded inundated area and unrealistic overflowing were observed in the scenario without entrainment while the simulation that takes entrainment into account presented more perfect results. It illustrates that entrainment is a non-negligible factor for the simulation of these volume-enlarging debris flows. (2) Two models considering the entrainment performed a good match between the simulation and the field survey. However, some noticeable differences can be observed in terms of the erosion-deposition distribution because different numerical schemes were adopted in the two models. Specifically, the DAN3D code always gives higher mobility and larger lateral spreading relative to the Shen model

Localization Accuracy of Ultrasound-Actuated Needle with Color Doppler Imaging

An ultrasonic needle-actuating device for tissue biopsy and regional anaesthesia offers enhanced needle visibility with color Doppler imaging. However, its specific performance is not yet fully determined. This work investigated the influence on needle visibility of the insertion angle and drive voltage, as well as determined the accuracy and agreement of needle tip localization by comparing color Doppler measurements with paired photographic and B-mode ultrasound measurements. Needle tip accuracy measurements in a gelatin phantom gave a regression trend, where the slope of trend is 0.8808; coefficient of determination (R2) is 0.8877; bias is −0.50 mm; and the 95% limits of agreement are from −1.31 to 0.31 mm when comparing color Doppler with photographic measurements. When comparing the color Doppler with B-mode ultrasound measurements, the slope of the regression trend is 1.0179; R2 is 0.9651; bias is −0.16 mm; and the 95% limits of agreement are from −1.935 to 1.605 mm. The results demonstrate the accuracy of this technique and its potential for application to biopsy and ultrasound guided regional anaesthesia

Numerical modelling of an alpine debris flow by considering bed entrainment

Numerical models have become a useful tool for predicting the potential risk caused by debris flows. Although a variety of numerical models have been proposed for the runout simulation of debris flows, the performances of these models in simulating specific events generally vary due to the difference in solving methods and the simulation of the entrainment/deposition processes. In this paper, two typical depth-averaged models have been used to analyze a well-documented debris-flow event that occurred in the Cancia basin on 23 July 2015. The simulations with and without bed entrainment are conducted to investigate the influence of this process on the runout behavior of the debris flow. Results show that the actual runout can be reproduced only by considering bed entrainment. If basal erosion is not taken into account, part of the debris mass deviates from the main path and both models predict unrealistic bank overflows not observed in the field. Moreover, the comparison between measured and simulated inundated areas shows that both models perform generally well in the terms of simulating the erosion-deposition pattern, although the DAN3D model predicts a greater lateral spreading and a thinner depositional thickness compared to Shen’s model. A simple numerical experiment obtains similar consequences and further illustrates the possible reasons that cause these differences

Modeling the runout behavior of the July 23rd, 2015 Cancia debris-flow event using two numerical models

On 23 July 2015, a typical volume-enlarging debris flow was triggered by heavy rainfall that occurred a few days before the event. The available data corresponding to this event is obtained from detailed field investigations conducted before and after the event, as well as the monitoring station installed in June 2014. This study aims to reproduce the July 23 debris-flow event using two different numerical methods, analyse the influence of entrainment on the runout behavior of the debris flow and compare the performance of different numerical methods when simulating the same debris-flow event. The results showed the following: (1) The expanded inundated area and unrealistic overflowing were observed in the scenario without entrainment while the simulation that takes entrainment into account presented more perfect results. It illustrates that entrainment is a non-negligible factor for the simulation of these volume-enlarging debris flows. (2) Two models considering the entrainment performed a good match between the simulation and the field survey. However, some noticeable differences can be observed in terms of the erosion-deposition distribution because different numerical schemes were adopted in the two models. Specifically, the DAN3D code always gives higher mobility and larger lateral spreading relative to the Shen model

Threshold Definition for Monitoring Gapa Landslide under Large Variations in Reservoir Level Using GNSS

The triggering threshold is one of the most important parameters for landslide early warning systems (EWSs) at the slope scale. In the present work, a velocity threshold is recommended for an early warning system of the Gapa landslide in Southwest China, which was reactivated by the impoundment of a large reservoir behind Jinping’s first dam. Based on GNSS monitoring data over the last five years, the velocity threshold is defined by a novel method, which is implemented by the forward and reverse double moving average of time series. As the landslide deformation is strongly related to the fluctuations in reservoir water levels, a crucial water level is also defined to reduce false warnings from the velocity threshold alone. In recognition of the importance of geological evolution, the evolution process of the Gapa landslide from topping to sliding is described in this study to help to understand its behavior and predict its potential trends. Moreover, based on the improved Saito’s three-stage deformation model, the warning level is set as “attention level”, because the current deformation stage of the landslide is considered to be between the initial and constant stages. At present, the early warning system mainly consists of six surface displacement monitoring sites and one water level observation site. If the daily recorded velocity in each monitoring site exceeds 4 mm/d and, meanwhile, the water level is below 1820 m above sea level (asl), a warning of likely landslide deformation accelerations will be released by relevant monitoring sites. The thresholds are always discretely exceeded on about 3% of annual monitoring days, and they are most frequently exceeded in June (especially in mid-June). The thresholds provide an efficient and effective way for judging accelerations of this landslide and are verified by the current application. The work presented provides critical insights into the development of early warning systems for reservoir-induced large-scale landslides

Threshold Definition for Monitoring Gapa Landslide under Large Variations in Reservoir Level Using GNSS

The triggering threshold is one of the most important parameters for landslide early warning systems (EWSs) at the slope scale. In the present work, a velocity threshold is recommended for an early warning system of the Gapa landslide in Southwest China, which was reactivated by the impoundment of a large reservoir behind Jinping’s first dam. Based on GNSS monitoring data over the last five years, the velocity threshold is defined by a novel method, which is implemented by the forward and reverse double moving average of time series. As the landslide deformation is strongly related to the fluctuations in reservoir water levels, a crucial water level is also defined to reduce false warnings from the velocity threshold alone. In recognition of the importance of geological evolution, the evolution process of the Gapa landslide from topping to sliding is described in this study to help to understand its behavior and predict its potential trends. Moreover, based on the improved Saito’s three-stage deformation model, the warning level is set as “attention level”, because the current deformation stage of the landslide is considered to be between the initial and constant stages. At present, the early warning system mainly consists of six surface displacement monitoring sites and one water level observation site. If the daily recorded velocity in each monitoring site exceeds 4 mm/d and, meanwhile, the water level is below 1820 m above sea level (asl), a warning of likely landslide deformation accelerations will be released by relevant monitoring sites. The thresholds are always discretely exceeded on about 3% of annual monitoring days, and they are most frequently exceeded in June (especially in mid-June). The thresholds provide an efficient and effective way for judging accelerations of this landslide and are verified by the current application. The work presented provides critical insights into the development of early warning systems for reservoir-induced large-scale landslides

Investigation of Microstructures and Mechanical Properties of Ultra-High Strength Al-Zn-Mg-Cu Alloy Prepared by Rapid Solidification and Hot Extrusion

Al-Zn-Mg-Cu aluminum alloys have the advantages of high specific strength, easy processing, and high toughness, showing great potential application in the aerospace field. However, ultra-high strength aluminum alloys usually contain coarse microstructures, micro-segregation, and casting defects that seriously deteriorate mechanical properties. Here, we report a high-strength aluminum alloy (Al-10.5Zn-2.0Mg-1.2Cu-0.12Zr-0.1Er) prepared by rapid solidification and hot extrusion to explore the microstructure modification of the alloy based on this strategy. The results show that: rapid-solidification technology can significantly refine alloy grains, alloy ribbons were composed of α (Al) equiaxed fine grains, and the average grain size was less than 6 μm. After extrusion, the alloy had partially recrystallized, existing coarse second-phase (T-phase) and needle-shaped precipitates were MgZn2 (η-phase), and the tensile strength and elongation of the extruded bar were 466.4 MPa and 12.9%, respectively. After T6 heat treatment, the tensile strength of the alloy reached 635.8 MPa, while elongation decreased to 10.5%. According to microstructure analysis and considering the contributions of grain boundary, dislocation, and precipitation-strengthening to the improvement of the mechanical properties, it was found that precipitation-strengthening is the main strengthening mechanism. Our research shows that rapid-solidification and hot-extrusion technology have great potential for improving the microstructures and mechanical properties of aluminum alloys

Multimodal Detection for Cryptogenic Epileptic Seizures Based on Combined Micro Sensors

The cryptogenic epilepsy of the neocortex is a disease in which the seizure is accompanied by intense cerebral nerve electrical activities but the lesions are not observed. It is difficult to locate disease foci. Electrocorticography (ECoG) is one of the gold standards in seizure focus localization. This method detects electrical signals, and its limitations are inadequate resolution which is only 10 mm and lack of depth information. In order to solve these problems, our new method with implantable micro ultrasound transducer (MUT) and photoplethysmogram (PPG) device detects blood changes to achieve higher resolution and provide depth information. The basis of this method is the neurovascular coupling mechanism, which shows that intense neural activity leads to sufficient cerebral blood volume (CBV). The neurovascular coupling mechanism established the relationship between epileptic electrical signals and CBV. The existence of mechanism enables us to apply our new methods on the basis of ECoG. Phantom experiments and in vivo experiments were designed to verify the proposed method. The first phantom experiments designed a phantom with two channels at different depths, and the MUT was used to detect the depth where the blood concentration changed. The results showed that the MUT detected the blood concentration change at the depth of 12 mm, which is the position of the second channel. In the second phantom experiments where a PPG device and MUT were used to monitor the change of blood concentration in a thick tube, the results showed that the trend of superficial blood concentration change provided by the PPG device is the same as that provided by the MUT within the depth of 2.5 mm. Finally, in the verification of in vivo experiments, the blood concentration changes on the surface recorded by the PPG device and the changes at a certain depth recorded by the MUT all matched the seizure status shown by ECoG. These results confirmed the effectiveness of the combined micro sensors