Movement Of Debris Research Articles

Space debris detection over intersatellite communication signals

In this paper, we apply a space-borne radar and communications (SBRC) concept for detecting space debris over signals that are designed solely for communication purposes. By using a hidden capability of intersatellite communications signals to act as a radar signal as well, we propose a new approach for debris detection that can be used to address the challenges of long-distance and ground-based detection without introducing a separate space-borne radar infrastructure. The performance of the proposed SBRC approach is evaluated from the two timely perspectives in emerging satellite communications, i.e. high-density constellations and 5G satellites. Several new findings are discovered and demonstrated via sophisticated simulations. These include the effect of system-level cooperation gain in small debris detection and link-level estimation of high-velocity debris motion.

Study on motion and distribution of debris in USV-MF complex–assisted WEDM-LS

Study on motion and distribution of debris in USV-MF complex–assisted WEDM-LS

CD33M inhibits microglial phagocytosis, migration and proliferation, but the Alzheimer's disease-protective variant CD33m stimulates phagocytosis and proliferation, and inhibits adhesion.

CD33 is a Siglec (sialic acid-binding immunoglobulin-type lectin) receptor on microglia. Human CD33 can be alternatively spliced into two isoforms: the long isoform (CD33M) and a shorter isoform (CD33m) that lacks the sialic acid-binding site. CD33m appears to protect against Alzheimer's disease; however, it remains unclear how. To investigate potential mechanisms by which CD33m may confer protection, we expressed the CD33m and CD33M isoforms of human CD33 in mouse BV-2 and human CHME3 microglial cells and assessed microglia functions. In the BV-2 cells, CD33M inhibited microglial phagocytosis of beads, synapses, debris and dead cells, while CD33m increased phagocytosis of beads, debris and cells. RNAi knockdown of the endogenous mouse CD33 increased phagocytosis and prevented CD33m's (but not CD33M's) effect on phagocytosis. CD33M increased cell attachment but inhibited cell proliferation, while CD33m did the opposite. We also found that CD33M inhibited cell migration. In human CHME3 cells, CD33M increased cell attachment, but inhibited phagocytosis, proliferation and migration, whereas CD33m did the opposite. We conclude that CD33M inhibits microglial phagocytosis, inhibits migration and increases adhesion, while CD33m increases phagocytosis, proliferation and inhibits adhesion. Thus, CD33m might protect against Alzheimer's disease by increasing microglial proliferation, movement and phagocytosis of debris and dead cells.

Simulating the postfailure behavior of the seismically- triggered Chiu-fen-erh-shan landslide using 3DEC

The dip-slope Chiu-fen-erh-shan landslide, estimated to have a volume of 36 × 106 m3, was triggered by the Mw 7.6 Chi-Chi earthquake. The debris covered an area of 1.95 km2 and claimed 36 lives. Although different discrete element methods have been applied to simulate the postfailure behavior of the Chiu-fen-erh-shan landslide in the last two decades, the lateral and dip-slope rock movements, the impact of the sliding debris against the hill in front of the slope toe and its final deposition have not been fully simulated. The major objective of this study was to investigate the possibility of applying three-dimensional (3D) numerical modeling code 3DEC to numerically model the debris movement and deposition of the Chiu-fen-erh-shan landslide under the impact of the Chi-Chi earthquake. By incorporating the spacing and orientation information of the joints and bedding planes, the slope was modeled as an assemblage of polyhedrons. Seismic ground motions were simultaneously applied in three dimensions. The shoveling effect was considered to erode the hill in front of the slope toe so as to extend the impact area and match more closely actual depositional topography. This study showed that the 3DEC simulations captured essential 3D characteristics of the landslide and resulted in a postfailure configuration similar to that observed in the field.

Autoregression models of large space debris motion

A statistical method was developed for modeling the large space debris motion in the class of autoregressive models. The method improves the quality of description and forecasting of the movement of large fragments of space debris based on their TLE elements.

Spacecraft survivability in the natural debris environment near the stable Earth-Moon Lagrange points

The theoretical analysis of the motion of natural space debris near the stable Earth-Moon Lagrange Points, L4 and L5, is presented with a focus on the potential debris risks to spacecraft operating near these points. Specifically, the research formulates a debris propagation model using four-body dynamics, then applies candidate probabilistic survivability models to a notional spacecraft operating at the L4 and L5 Lagrange points to quantify the collision risks to the spacecraft from natural debris particles. Of the survivability models implemented, the natural debris collision risks to spacecraft survivability are found to be incredibly low, but mitigation strategies to reduce the risk further are identified in this study. Overall, research into stable Lagrange point natural debris propagation improves understanding of the collision risks posed by the naturally occurring Kordylewski clouds and enhances operational planning for Lagrange point space missions.

Experimental investigation on rock mechanical properties and infrared radiation characteristics with freeze-thaw cycle treatment

The effect of freeze-thaw weathering cycles caused by diurnal and seasonal temperature changes is a significant disadvantage in the stability of rock engineering in cold regions. To investigate the evolution rule of rock strength and infrared radiation characteristics of igneous, metamorphic, and sedimentary rock subjected to freeze-thaw weathering cycles, freeze-thaw weathering cycle treatment was conducted on coarse-grained granite, fine-grained marble and soft red sandstone from cold regions in Western China. The nondestructive detection technique of nuclear magnetic resonance (NMR) was used for rock damage detection. Infrared thermography was used to monitor the rock debris movement, crack propagation and average infrared radiation temperature (AIRT) during unconfined compressive strength (UCS) testing. The mechanisms of rock damage and change in AIRT induced by freeze-thaw weathering cycles were carefully analyzed. According to the UCS evolution rule, the ranking order (from high to low) of the results of rock resistance to freeze-thaw weathering processes is as follows: marble, granite and sandstone. An indicator called the infrared radiation rate was proposed to measure the rate of increase in infrared radiation temperature with increasing stress during the UCS tests. The rank order (from high to low) of the infrared radiation rate results is as follows: sandstone, marble and granite. Based on the infrared images and photographs of the failed rock specimens, the failure patterns and processes of the different rock types are investigated.

Hydro-Magneto-PIC hybrid model for description of debris motion in high altitude nuclear explosions

A Hydro-Magneto-PIC (particle-in-cell) hybrid model is proposed to describe the motion of the fission debris in high altitude nuclear explosions (HANEs). Compared with the state-of-art numerical models, our model is able to stably compute the motion of the fission debris in a broader spatial region. In a real HANE, the physical process contains many spatial scales. The upward moving debris particles manifest kinetic properties due to the fact that the dilute ambient atmosphere and the downward expanding particles manifest a fluid-like pattern and can be approximated by the usual hydro-dynamical models. Meanwhile, the debris particles receive electromagnetic forces from both the geomagnetic fields and the charged particles at all frequencies. This broad scale of frequencies can induce large- and small-scale instabilities, which cannot be solved by the usual hydrodynamic equations. Considering the motions of the debris and the different properties of the high temperature ions, the low temperature ions and the neutral atmosphere, we consistently combine three models for completely describing the debris expansion. The high temperature ions are described by the PIC model for their intrinsic kinetic behaviors, the low temperature ions are described by the magneto-hydrodynamic model for their fluid property, and fluid equations are applied to the neutral particles with no electromagnetic force. The corresponding interactions among the three components are added into the equations as the source terms. With the combination of the three models, our algorithm can stably calculate the regions that are a few thousand kilometers in altitude. Our proposed model contains both the kinetic and fluid properties, and is stable in numerical implementations. Finally, we calculate the debris motion in the Starfish experiment. The results confirm a consistency of our proposed model with the observations. The spatial scale of our simulation results is consistent with the result in the Starfish experiment. In addition, we also plot the distribution of the debris with different projection angles at various snapshots. These results give us an intuition to understand the influence of the various factors, such as the friction of atmosphere, the magnetic pressure, flute instability and the Hall currents. Our model provides a tool for implementing the HANE simulation in a broader scheme, and can also be utilized in other plasma systems.

Study of Debris Movement in South and West Coast of Sumatra and Java and Its Impact on Bali Strait During Western Monsoon

Bali Strait is one of the most unique and important water areas, especially for the coastal communities of Banyuwangi and Jembrana up to Badung Regency. The Bali Strait has Sardinella lemuru fish resources where it is widely exploited and is the main livelihood income of the coastal communities. In recent years, the quality of Sardinella lemuru fish has begun to decline due to contamination of microscopic plastic debris in the Bali Strait during western monsoon. Many previous researches have carried out the movement of debris in the Bali Strait using numerical model to find out the source and location of the marine debris, however it only carried out local simulations within the Bali Strait. This study aims to determine the movement of debris that reaches the Bali Strait assuming debris originates from coastal areas on south and west coast of Sumatra and Java during the western monsoon (December 2018 - February 2019). The Finite Volume Coastal Ocean Model (FVCOM) model is used to obtain circulation of current patterns and debris particles movement patterns using the Lagrangian Particle Tracking module. The verification result of the model current pattern and field data using the Root Mean Square Error (RMSE) equation. In the u velocity component the RMSE value is 0.014 m/s with a correlation of 0.968 and the v velocity component is 0.011 m/s with a correlation of 0.945. In general, the current pattern in the waters of southern of Sumatra Island to Java Island in the dominant western monsoon moves eastward due to the influence of western monsoon. The simulation results show particles that reached the Bali Strait as much as 3.47% originating only from the coastal waters of East Java.

Dynamics and control of space debris during its contactless ion beam assisted removal

The space debris removal is one of the most important challenges of astronautics. The creation of contactless transportation systems based on the ion beam is a promising direction for solving this problem. The orientation of the debris object in the ion beam has a great influence on the magnitude and direction of the force transmitted by this beam. The aims of the work are to study the attitude dynamics of space debris during its transportation by ion beam, to search angular motion modes, which are most favourable from the point of view of the force transmission efficiency by the ion beam, and to develop the engine thrust control law that ensures the transfer of the object to these motion modes. A mathematical model describing the space debris motion under the influence of gravitational, and ion beam forces and torques is developed. An analysis of the cylindrical space debris object’s undisturbed attitude motion is carried out, and the most favourable orientation of space debris is determined. Control law for transferring the space debris in the required angular motion mode by a change in the thrust of the ion engine are considered. Numerical simulation confirmed the effectiveness of the proposed control law.

Aspects of comet-like acceleration of ablating dust in tokamak SOL

Vertical Disruption Events (VDE) in tokamaks, may cause significant melting along tile ridges of the vessel upper dump plates with release of metallic particulate and droplets as shown in and in references therein. Accurate studies of the motion of such debris released in the vessel are important for the inventory of tritiated composites in a reactor. Recently numerical codes have been developed to track this particulate of variable mass and charge, in interaction with the Scrape-Off layer (SOL) plasma. Here a contribution is given for a more consistent discussion of the additional acceleration of the dust due to asymmetric loss of mass in flight. A simplified description is constructed in analogy with the physics of comets.

Marine macro debris transport based on hydrodynamic model before and after reclamation in Jakarta Bay, Indonesia

Jakarta Bay as an area with the densest population in Indonesia became one of the highest contamination level waters in the world includes pollution of debris. Reclamation activities in Jakarta Bay will change the water conditions will also affect the distribution of debris at sea. Therefore, this study conducted to determine the movement of the macro debris before and after island reclamation in Jakarta Bay. The method used is a model that simulated by the hydrodynamic model and particle trajectory model. Data needed for the hydrodynamic model were wind, tides, bathymetry, and shoreline, while for the trajectory of the particles using a data type of macro debris, debris weight, and debris flux. Hydrodynamics simulations indicate if a reclamation island formation does not change surface current patterns significantly, but causes a decrease in the flow velocity of ± 0.002 to 0.02 m/s at some point. The trajectory of particles of debris indicate if after reclamation, debris tends to accumulate in the eastern Jakarta Bay in the rainy season (January) as there are anticlockwise eddy current, as well as in the western and eastern regions during the dry season (July), because there is a clockwise eddy current in the eastern Jakarta Bay.

Windborne debris trajectories in tornado-like flow field initiated from a low-rise building

This paper examines compact debris flight in tornado-like flow fields. The research focuses on physically simulating a specific tornado-like vortex and on investigating windborne debris flight with and without a low-rise building model. The low-rise building model, 1/8th scale with regard to the vortex core radius, was used to initiate the flight of Styrofoam spheres from its top. Debris motion was recorded using three high-speed cameras and data reduction was performed on open-source OpenPTV software. Flow field characterisation showed that including a building model does not considerably affect the averaged flow field but only the local instantaneous flow field. Debris flight analysis shows that the mean flight distance is not affected by the building model, but a change in the initial direction occurs. Comparison between local wind flow field and initial debris velocities shows good agreement, and therefore the variability in initial directions of the debris flight can be attributed to a wind-driven process. To compare with experimental data, experimental data were incorporated into debris flight equations to compute debris motion. Debris trajectories computed from experimental data show strong visual similarities with experimental trajectories and debris flight analysis presents good agreement with experimental data.

A simple method to evaluate the performance of an intercept dam for debris-flow mitigation

This study aimed to establish a simple approach to evaluate the performance of an intercept dam during a debris-flow event. We applied the two-phase debris-flow model proposed by Pudasaini (2012) and combined it with the dam moment-balance equation, to describe the state of the debris flow and the structural integrity and functions of such dams. To delineate dam performance, we introduced two new variables, representing reservoir capacity and anti-overturning stability of the dam, respectively. In addition, we developed a grid optimization technique to improve calculation efficiency. The feasibility of the proposed model was validated by simulating a debris-flow event in the Hongchun catchment, Sichuan, China, where a system of structures had been constructed to prevent debris flows, or to mitigate the possible hazard. Our results suggested that the process of debris-flow propagation and the variation in dam performance caused by the interaction between the debris motion and the dam were appropriately described. Further, we have presented a discussion on dam collapse and solid–fluid separation to clarify their effects on debris-flow mitigation.

Machining Characteristics of USV-MF Complex Assisted WEDM-LS Based on Multi-physical Coupling

Ultrasonic vibration (USV) and magnetic field (MF) complex assisted techniques are combined with low speed wire electrical discharge machining (USV-MF complex assisted WEDM-LS) to improve the machining performance of conventional WEDM-LS. Firstly, the simulation results of multi-physical coupling simulation model show that under the influence of ultrasonic vibration, the working fluid fluidity is greatly enhanced and its temperature is significantly decreased. Then, a three-phase flow model of bubble, working fluid and debris in the machining area is established to investigate the effects of ultrasonic vibration on bubble and debris, and the process of bubble rupture is simulated. The simulation results show that with the increase of ultrasonic frequency, the movement of bubble and debris becomes fiercer and fiercer, when ultrasonic frequency is 30 kHz and ultrasonic amplitude is 10 μm, the bubble is collapsed. Finally, comparison of the experimental results of conventional WEDM-LS, USV assisted WEDM-LS, MF assisted WEDM-LS and USV-MF complex assisted WEDM-LS in machining TiNi-01 shape memory alloy reveals that the ratio of normal discharge and the material removal rate are both increased, the workpiece surface roughness value is decreased and the workpiece surface quality is improved in the process of USV-MF complex assisted WEDM-LS.

Wildfire risk, post-fire debris flows, and transportation infrastructure vulnerability

ABSTRACT Wildfires have grown in number, size and intensity in the American West and forecasts predict worsening trends. Evidence mounts that post-fire debris flows pose a major hazard to infrastructure, particularly roadways. Vulnerabilities of assets to post-fire flows requires consideration of geologic, vegetative, and hydrologic conditions. A model that considers environmental conditions, post-fire effects, and transportation asset use is developed, and applied to a fire prone region in Arizona. 17% of watersheds have a greater than 20% chance of post-fire debris movements and flooding under a minor precipitation event. Additionally, there is a greater than 50% probability of post-fire debris flows where recent fires have occurred, validating the underlying model. The model shows the vulnerability of infrastructure to environmental and technological variables, drawing attention to the need to manage the risk as a broader system.

A novel micro-EDM method to improve microhole machining performances using ultrasonic circular vibration (UCV) electrode

The difficulties in circulating working fluid and expelling discharge debris are major challenges for microhole machining by micro electrical discharge machining (micro-EDM). To solve this issue, a novel micro-EDM method that adopts ultrasonic circular vibration (UCV) electrode was proposed in this study, aiming at effectively improving the microhole machining performances. A piezoelectric device for UCV electrode with 32.85 kHz frequency and 3 μm trajectory radius was developed and its basic principle was analyzed. To better understand the effect of UCV electrode on microhole machining process, the solid-liquid two-phase flow simulation was conducted, and the flow field distribution and discharge debris movement in machining gap were studied. Machining experiments of deep microhole (aspect ratio = 9.4) showed that the UCV electrode can effectively lower the electrode retreat frequency and prevent the debris adhesion at the inner wall. 10 × 10 microhole array machining experiments were also carried out in this study. Results showed that the inlet and outlet of microhole array have better morphologies when using UCV electrode, and the diameter consistency of inlet and outlet were improved by 22% and 2.8% compared with rotating electrode. The advantages of UCV electrode in improve microhle machining performances can be mainly attributed to the significantly enlarged flow velocity of working fluid and enhanced capacity of working fluid to expel debris particles in terms of number and efficiency. Meanwhile, the increased relative velocity between electrode and workpiece is also effective to discontinue the abnormal discharges and achieve stable machining process.

Study on Gap Phenomena Before and After the Breakout Event of Fast Electrical Discharge Machining Drilling

Abstract Fast electrical discharge drilling is broadly used to manufacture small holes on molds, dies, filters, and automobile and aerospace components. Breakout is the event when the tool electrode reaches the opposite surface of the workpiece. When a breakout happens, the machining efficiency drops sharply and the process becomes unstable. To gain a deep understanding of the breakout process, this paper observed the gap phenomena before and after the breakout with cameras through a quartz glass flake. Experiments were conducted on the workpiece tilted to 45 deg. From the observation, it was found that the deformation of the electrode was not negligible. The electrode would vibrate or shake before and after the breakout. Side-gap sparks were common in the process, and even more were observed after the breakout. The fluid flow in the discharge gap and the side gap did not vanish immediately when a breakout happened and could still evacuate debris for a short period. The debris gradually accumulated as the fluid flow in the gap vanished. A series of simulations were conducted to study the fluid flow and debris movement after the breakout. And simulations were also performed to find the influence on electrode vibration of high-pressure flush fluid and discharge location. The results of simulations agreed well with the observed phenomena. From the observation and simulation results, the deformation or vibration of the electrode and the accumulation of debris were found to be the main factors that led to the low machining efficiency after the breakout.

Debris Flow Generation Based on Critical Discharge: A Case Study of Xiongmao Catchment, Southwestern China

Generation of debris flows is related to poorly sorted mixtures of soil, catchment topography, and rainfall characteristics. Runoff in a valley resulting from intensive rainfall can induce sediment movement within stream beds or along adjacent banks. The water flow in channels is affected by rainfall parameters such as duration, intensity, cumulative rainfall, etc., and is the key factor in debris movement. In this paper, the rainfall characteristics and occurrence conditions of debris flow in Xiongmao Gully on 26 July 2016 were explored. Using data from field surveys and indoor simulation experiments, evaluations of critical discharge parameters for debris movement were performed. Furthermore, debris distribution and the critical discharge characteristics were analyzed via investigation of the catchment topography and cause of the debris flow, and analysis was made of the critical discharge parameters initiating channel debris movement. A K-value clustering analysis method was applied to characterize the rainfall pattern of the study area and its effects on calculation of debris flow. The results showed that for the debris flow in Xiongmao Gully, the debris initiation in the middle reaches of the gully provided the majority of solid particles for the disaster on 26 July 2016, and the upstream confluent provided catchment. Based on the relationship determined by laboratory tests, the calculated critical discharge was 43.8 m3/s, less than the peak discharge (Qc = 66.7 m3/s) calculated by morphological method. In addition, it was indicated that the dominant rainfall patterns of the studied area were first-quartile and second-quartile, i.e., the rainfall occurred primarily at the early or middle stage of this rainfall event. The critical discharge for the debris flow on 26 July was achieved at 5% rainfall frequency, and the larger runoff volume was generated from a short heavy rainfall. According to specific catchment characteristics, such as distributed hydrological analysis, critical discharge, and rainfall pattern of debris flow, forewarning of a damaging debris flow could be made more effective.

Investigation of influence of baffles on landslide debris mobility by 3D material point method

In mountainous terrain, landslide debris is a common occurrence around the world that can potentially result in catastrophic consequences to downstream residents and facilities. Arrays of baffles are increasingly used as energy dissipaters for the protection from debris flow due to their low cost and environmental impact. However, the development of a numerical tool for the rational design of such structures is still a challenge. In this work, a material point method computational framework is presented, using two contact models to describe the landslide debris movement and interaction with structures, respectively. Flume model experiments are adopted as calibration and good agreements are exhibited in flow kinematics between computed results and physical model tests. Simulations on an idealized scenario of landslide debris flow show how the baffle geometry/arrangement has key effects on the debris movement and deposition. The impact force in soil-structure interaction has also been studied, showing the ability of this method on evaluation force characteristics acted on baffle structures.