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We consider absorbing chemical reactions in a fluid flow modelled by the coupled advection–reaction–diffusion equations. In these systems, the interplay between chemical diffusion and fluid transportation causes the enhanced dissipation phenomenon. We show that the enhanced dissipation time scale, together with the reaction coupling strength, determines the characteristic time scale of the reaction.

The nematodeCaenorhabditis elegansis one of the most widely studied organisms in biology due to its small size, rapid life cycle, and manipulable genetics. Research withC. elegansdepends on labor-intensive and time-consuming manual procedures, imposing a major bottleneck for many studies, especially those involving large numbers of animals. Here we describe the first general-purpose tool, WormPicker, a robotic system capable of performing complex genetic manipulations and other tasks by imaging, phenotyping, and transferringC. eleganson standard agar media. Our system uses a motorized stage to move an imaging system and a robotic arm over an array of plates. Machine vision tools identify animals and assay developmental stage, morphology, sex, expression of fluorescent reporters, and other phenotypes. Based on the results of these assays the robotic arm selectively transfers individual animals using an electrically self-sterilized wire loop, with the aid of machine vision and electrical capacitance sensing. AutomatedC. elegansmanipulation shows reliability and throughput comparable to standard manual methods. We developed software to enable the system to autonomously carry out complex protocols. To validate the effectiveness and versatility of our methods we used the system to perform a collection of commonC. elegansprocedures, including genetic crossing, genetic mapping, and genomic integration of a transgene. Our robotic system will accelerateC. elegansresearch and opens possibilities for performing genetic and pharmacological screens that would be impractical using manual methods.Significance StatementThe nematodeCaenorhabditis elegansis a powerful genetic model organism in life sciences due to its compact anatomy, short life cycle, and optical transparency. Current methods for worm genetics rely on laborious, time-consuming, and error-prone manual work. Here, we describe the first general-purpose automated tool capable of genetically manipulatingC. elegans. Our robotic system will accelerate a broad variety ofC. elegansresearch and opens possibilities for performing genetic and pharmacological screens that would be impractical using manual methods.

Environmental noise in spread spectrum induced polarization (SSIP) data seriously affects many steps in SSIP data processing and imaging. An effective denoising approach for environmental noise is still a challenging task for traditional denoising approaches. We introduce coherence theory into the frequency-domain induced polarization approach to extract the amplitude spectrum of complex resistivity from SSIP records. This fusion approach calculates frequency-domain correlations between a signal source and a collected signal based on coherence theory. The useful components of the power spectrum for the collected signal are next extracted by exploiting the correlations. This amplitude spectrum can be calculated from these useful components. This approach is tested using synthetic and real SSIP data. The simulation test shows that the relative error of the amplitude spectrum processed by the effective approach is 3.9% at 160 Hz when the signal-to-noise ratio (SNR) is −44.2 dB. The field experiment shows that this approach minimizes the standard deviation (SD) of the data, is better able to distinguish adjacent high-resistivity anomalies, and improves the reliability of the amplitude spectrum in subsequent processing and interpretation.

We study the (hydro-)dynamics of multi-species driven by alignment. What distinguishes the different species is the protocol of their interaction with the rest of the crowd: the collective motion is described by different communication kernels, ϕ α β , between the crowds in species α and β. We show that flocking of the overall crowd emerges provided the communication array between species forms a connected graph. In particular, the crowd within each species need not interact with its own kind, i.e., ϕ α α = 0 ; different species which are engaged in such ‘game’ of alignment require a connecting path for propagation of information which will lead to the flocking of overall crowd. The same methodology applies to multi-species aggregation dynamics governed by first-order alignment: connectivity implies concentration around an emerging consensus.

Defense structures are commonly constructed on the upstream side of bridge piers to mitigate the impact of potential debris-flow events. In this study, field investigations were carried out to obtain the geological conditions and geometric layout of engineering structures on a typical debris-flow site. A two-phase numerical model was adopted to simulate the dynamic processes of the debris flow rushing through a group of defense structures, and the V-shape debris-flow wakes detached from the defense structures were numerically studied. The results show that an oval-shape two-phase flow structure was formed due to the dynamic interaction between two neighboring debris-flow wakes. The shape of this flow structure is related to the viscosity, impact velocity, base fiction and structural arrangement. The corresponding center position and the maximum thickness of this superposed wakes are found to be correlated (nonlinearly or linearly) to the Froude number, Reynolds number, Manning friction number and lateral spacing of the defense structures. The present study improves the understandings toward the effects of the protective structural system on the debris-flow dynamics and can be used to optimize the structural design in debris-flow risk area.

In electrical exploration techniques, an effective suppression method for Gaussian and impulsive random noise in spread-spectrum induced-polarization (SSIP) data continues to be challenging for conventional denoising methods. Remnant noise influences the complex resistivity spectrum and damages the subsequent interpretation of geophysical surveys. We have developed a hybrid method based on a correlation function and complex resistivity, which introduces the correlation analyses among the transmitting source, the measured potential, and the injected current signal. According to the analyses, reliable results for complex resistivity spectra can be calculated, which can be further used for noise suppression. We apply the hybrid method to numerical and field experiments to process the measured SSIP data. Simulation tests find that the hybrid method not only suppresses the two types of noise but also improves the relative error of the complex resistivity spectrum. Field data processing indicates that the hybrid method can minimize the standard deviation of the data and can have a greater ability to distinguish adjacent objects, which can improve the reliability of the data in subsequent processing and interpretation.

The strength recovery (healing) of the shear zone soil of a landslide during the dormant phase after the sliding affects the reactivation of the landslide, and may play a key role in determining the stability of the landslide. In this paper, we report the laboratory measurements of frictional strengthening characteristics of a red-bed landslide soil. Slide-hold-slide (SHS) experiments and ultrasonic tests are performed on soil samples under natural moisture content and saturated conditions. The roles of holding time, normal stress, and drainage conditions in friction enhancement are evaluated. All the experiments are performed under room temperature. The saturated soil samples show the lowest recovery value of shear strength. It is found that red-bed landslides have obvious healing properties. The recovery value log-linear depends on the holding time and proportional to the normal stress, and the better the drainage condition is, the more obvious the recovery. Ultrasonic tests show that the wave speed difference of soil sample before and after holding is proportional to the holding time.

Rock slope failures are controlled by a complex interplay of geological structures and anthropogenic activities. In this study, data from structural geology, rock mass characterization, and ground-based monitoring networks are integrated into a numerical model. This model is used to explore the relationships among structural features, damages, anthropogenic activities, and slope failures occurring on the Tibetan Plateau in China. In particular, a model for the interpretation of brittle tectonic structures is illustrated, which characterizes the fracture patterns and explains the role of these features in the development of rock slope instability. Additionally, the relationships between tectonic structure-related fractures and slope failure mechanisms are investigated by characterizing the rock mass damage using the geological strength index. Finally, a numerical model is developed, which integrates the available data. It is found that the tectonic structure-related fractures controlled by an anticline are primarily responsible for slope failure, while an excavation was identified as its triggering mechanism. This research can serve as a reference for studies on excavation-induced rockslides.

The material point method (MPM) has been increasingly used to simulate coupled hydro-mechanical problems involving large deformations. However, when addressing saturated porous media with an almost incompressible liquid phase, the classic explicit MPM with low-order interpolation functions is not stable if no further stabilization approach is used. In this study, a solid-velocity–liquid-velocity-based hydro-mechanical governing formulation is adopted to construct a two-phase single-point explicit generalized interpolation material point (GIMP) method. To stabilize this set of formulation, the XPIC(m) (extended PIC of order m) method is extended to erase null space noise and damp high-frequency waves in both solid and liquid phases; additionally, a cell-based averaging approach is adopted to solve locking issues and smooth stress field variables. Several numerical examples have been presented to demonstrate the capabilities of the stabilized coupled GIMP method in simulating coupled hydro-mechanical problems involving dynamic effects and large deformations.

Accurate measurements of bedload flux in mountain rivers remain an important issue in hydraulic engineering. Diverse acoustic-based monitoring devices have been utilized to record continuous vibration signals triggered by bedload particle impacts, aiming to translate bedload information such as transport rates and grain size distributions from the generated signals. However, the spatial variability of bedload impacts on the river bed (or on an impact plate) contributes to uncertainty in the calibration relationship between the recorded signal and bedload flux.The present study develops an acoustic model based on microphone data to determine the characteristics of the air shock waves induced by the bedload particle impacts on the bed. A phased microphone array (PMA) system is established on the plane underside of an impact plate flush with the river bed, which includes a number of mini microphone elements set apart from each other at a specific spacing distance. The model allows for a calculation of the cross-power matrix of the air vibrations recorded by each microphone of the array. The acoustic vibrations recorded on the PMA plane are subsequently reconstructed and transformed to an acoustic image of the sound source on a scanning plane of the plate surface, considering different air propagation models corresponding to monopole, multipole and moving sources. As a result, the locations of the bedload particle impacts can be detected, connecting to the central coordinates of the reconstructed sound source. The signal amplitude extracted from the sound intensity in the reconstructed acoustic image potentially provides a better way for classifying bedload particle size than just utilizing the raw data recorded by one of the microphone elements.The findings of this study contribute to the measurement and monitoring of the bedload transport with an acoustic system, illustrating a promising way to identify bedload impact locations, which could be helpful in grain size classification during the transport process.

Measuring debris-flow properties remains a significant challenge in studies of natural hazards. Recent works suggest that the seismic signals generated by debris flows can help analyze flow dynamics, but theoretical details for estimating bulk flow properties from seismic signals are not fully understood or comprehensively tested. Here, we invert basal force fluctuations on the torrent bed using high frequency seismic signals generated by 6 well-documented debris flows at Illgraben, Switzerland. Verified against independent measurements, our seismically-derived basal force fluctuations match well with the measured basal fluctuations at a force plate and correlate with the bulk flow properties, including flow depth and weight. We propose a physical model employing the multi-particle force chains and random single-particle impacts within a debris flow to simulate the generation of high frequency seismic signals. We find that the random impacts of single particles and of multi-particle force chains are active at the same time, and together they control the debris-flow’s basal force fluctuations. For different events and different positions within events, the relative contributions of single particle impacts and of multi-particle force chains dominating the basal fluctuations vary significantly and control the non-linear relation between the high-frequency seismic signal strength and the bulk flow characteristics. According to our model, fluctuating basal forces are strongly controlled by particle sizes and flow depth. Our results open new perspectives for the understanding of high frequency seismic signals generated by debris flows and the estimation of bulk flow characteristics, such as flow depth and weight.

Debris flows are typical two-phase flows that commonly occur with entrainment. By involving sediment materials, the fluid viscosity of debris flow may change significantly along with the variety of...

This study aimed to investigate the formation and propagation processes of a landslide-generated debris flow within a small catchment while considering the effects of vegetation. This process is divided into three stages: rainfall infiltration, slope failure, and debris flow routing, according to their different mechanisms. Existing models that involve the effect of vegetation for each stage, including Richards’s model, infinite slope stability model, and the enhanced two-phase debris flow model (Pudasaini 2012), were coupled. The tridiagonal matrix algorithm and finite volume method were applied to solve these equations, respectively. Finally, the approach was tested by application to the 2018 debris flow event in the Yindongzi catchment, China. The results showed that the proposed comprehensive model could effectively describe the behaviors of each stage during the formation and propagation processes of landslide-generated debris flows in vegetated area. The roles of vegetation on each stage, such as root water uptake and root soil reinforcement, were also analyzed by performing several scenarios.

Rapid long-runout landslide is a hot topic in the field of landslide researches. Many researchers have proposed different models and hypotheses to explain the superfluidity of long-runout landslides. In this paper, the mechanism of sliding surface weakening caused by particle breakage is studied. Particle breakage can not only cause the excess pore water pressure but also weaken the friction coefficient of the sliding surface. These two factors are both the causes of the superfluidity of the landslide induced by particle breakage. In addition, the evolutions of breakage potential and excess pore water pressure are coupled into landslide dynamic equations to simulate how the particle characteristics such as porosity, crushing hardness, and particle shape influence the landslide fluidity. During sliding process, the numerical results indicate that the breakage potential of sliding surface decreases nonlinearly with time, the excess pore water pressure generated by particle breakage increases first and then decreases nonlinearly, and the effective friction coefficient decreases nonlinearly with time and tends to a residual value.

In Western China, a large number of bridges are located in debris flow gullies and are exposed to a great risk of damage in case of a geological disaster. To ensure the safety of the bridge and extend its service period, in this study, we propose a modular protective device for bridge piers against the impact of debris flow, especially large boulders. The device is composed of a set of independent modules in the form of a closed-cell aluminium foam-filled composite structure (AFCS) that are set at predetermined spacings and fixed by prestressed steel fasteners. The mechanical behaviour and energy absorption characteristics of five AFCS configurations were evaluated by quasi-static compression testing using both experimental and numerical modelling methods, which produced similar results. The two-layer foam-filled lattice structure AFCS05 exhibited the best comprehensive energy absorption performance, and the effects of the material and geometric parameters on the performance were investigated based on the validated finite element models. A prototype protective device based on the AFCS05 design was attached to a model bridge pier. The dynamic response of the prototype indicated that the device prolonged the impact duration and reduced the largest impact force by 84.89%, and absorbed 81.96% of the impact kinetic energy, which effectively protected the pier. The device design and production can be standardised, making it convenient for installation and on-site repair.

This study aimed to develop an integrated model of the runoff-generated debris flow that considers the initial conditions, movement mechanisms, and entrainment effect. The study focused on the formation and propagation processes of debris flow within a catchment, and the process is divided into three stages: rainfall infiltration, runoff, and debris flow routing. Soil saturation, rainfall, and entrainment are the main factors that influence the debris flow formation and propagation processes. Existing models for each stage, including Richards’s equations, shallow water equations, and two-phase debris flow equations, were coupled. The tridiagonal matrix algorithm and finite volume method were applied to solve these equations. Finally, several experimental cases and the 2010 debris flow event in the Hongchun catchment in China were simulated by using the proposed model. The results showed that the proposed model could effectively describe the behaviours of each stage during the debris flow formation and propagation processes. Although several aspects of the model require further improvement, the physical-parameter-based prediction of runoff-generated debris flows from formation to propagation is effectively performed by the model.

To mitigate potential damage from debris flows, numerous check dams have been constructed in thousands of debris flow gullies all over the world. However, the efficiencies of these check dams are largely unknown because they are normally designed based on empirical methods. This paper presents an assessment of the impeding effect of check dams constructed in the Hongchun debris flow gully in Sichuan Province, China by using an improved finite difference model. Compared with other models, the improved model can consider both the impeding effect of check dams and bed entrainment. We analyzed the impeding effect of these check dams on different initial scales of debris flows. The results show that these check dams perform quite well in constraining bed entrainment downstream of the gully. The average velocity, peak discharge, and final scale of a debris flow in the gully can be substantially reduced by constructed check dams. The impeding effect is sufficient when the initial volume of the debris flow is less than 1.5 times that of the catastrophic debris flow event that occurred in this gully on 14 August 2010. This study improves our understanding of the influence of check dams on the dynamic and bed entrainment processes of debris flows. The model adopted in this study can be a robust tool to quantify the efficiencies of existing check dams and provide reasonable guidance in the design of check dams in debris flow gullies.

Due to global climatic warming, the possibility of collapse of polythermal glaciers is increasing. In the summer of 2016, two massive glaciers suddenly collapsed at Aru Village, Ali District, Xizang Autonomous Region, China, running out up to 7 km and killing nine herders. These events occurred suddenly in a remote area, and quantitative data about them was difficult to obtain quickly. Their seismic waves, however, could be quickly inverted to estimate the event motion parameters; the inversion results reflecting the average state. In order to have an initial judgment on the deposit range and the kinematic parameters at different positions after the collapse, seismic-wave inversions were used to estimate parameters (e.g., mass and friction coefficient) for numerical simulation to quickly simulate the motion processes that are important for the initial rescue, especially in the absence of topographic data. Numerical simulation showed that even though the shape and depth of the source area as assigned from such inversion were slightly different from the real situation, the effect on the final deposit morphology was not so great, which can be used as a reference for useful assessment after future disasters.

Rock avalanches are unpredictable due to their complex geological conditions and dynamics and such features have been regarded as important reasons for property damage and fatalities. The Ganluo rock avalanche of August 14, 2019 in China provides an outstanding case to evaluate the failure mechanism and dynamic process of long-runout rock avalanches. To understand the failure mechanism and dynamics of such events, a combination of in situ investigation, remote sensing data study, and simulation is performed. The result shows that the Ganluo rock avalanche released a rock mass volume of approximately 5.20 × 104 m3 that detached from the slope, and 1.52 × 104 m3 of unstable rock mass is still in the source zone. The analysis indicated that the prerequisite for the rock avalanche was continuous heavy rainfall, which occurred in the preceding months. The simulation shows the maximum sliding velocity is approximately 22 m/s. Additionally, the potential destructive zone of the unstable rock mass is evaluated, which can provide a reference for secondary disaster prediction.

A mountain disaster chain always brings about potential danger to the safety of people and the environment based on its characteristics of long time-scale, great destructive power, and broad scope. Mechanisms responsible for this hazard are represented by studying a landslide-caused disaster chain that occurred in the bank of Jinshajiang River, China on 10 October 2018. The evolution process of this disaster chain is simulated and analyzed using a coupled model that consists of several depth-averaged equations, and the results agree well with the measured data. Furthermore, several factors, including frictional coefficient, inflow flux, and critical dam slope coefficient, are tested by applying different values. Results indicate that the evolution of a mountain disaster chain can change at each stage with different initial conditions.

Blockchain applications are considered as “trustless” machines, because they reduce business’s needs of trust in others. The “trustless” nature draws researchers’ attention on investigating the implications of blockchain in a business environment. From a view of business ethics, this paper aims at evaluating the impacts of blockchain applications on trust and business. After expounding the relations between trust in blockchain and trust in business partners, I evaluate the impacts based on a framework of competence trust, contractual trust, and goodwill trust. My conclusion is that full acceptance of trust in blockchain over trust in others is not good and will cause several risks that cannot be neglected. The main contribution of this paper is investigating and summarizing ethical and commercial risks of blockchain applications including disintermediation fallacy, centralization of trust, ambiguous contract, noncognitive trust in untrustworthy partners, and more actions guided by moral minimum.

Heterogeneous graph neural networks (HGNNs) have been blossoming in recent years, but the unique data processing and evaluation setups used by each work obstruct a full understanding of their advancements. In this work, we present a systematical reproduction of 12 recent HGNNs by using their official codes, datasets, settings, and hyperparameters, revealing surprising findings about the progress of HGNNs. We find that the simple homogeneous GNNs, e.g., GCN and GAT, are largely underestimated due to improper settings. GAT with proper inputs can generally match or outperform all existing HGNNs across various scenarios. To facilitate robust and reproducible HGNN research, we construct the Heterogeneous Graph Benchmark (HGB), consisting of 11 diverse datasets with three tasks. HGB standardizes the process of heterogeneous graph data splits, feature processing, and performance evaluation. Finally, we introduce a simple but very strong baseline Simple-HGN--which significantly outperforms all previous models on HGB--to accelerate the advancement of HGNNs in the future., KDD 2021 research track