Movement Of Debris Research Articles

Study on the Mechanism of Carbon Steel Sparks

Abstract Spark testing is an effective and convenient method that can be used be identify general classification of the steel material by observing the sparks projected by the grinding wheel. In order to more accurately identify the type of spark, the spark streams of carbon steels are described and illustrated by a high-speed camera. The appearance and phase analysis of the residues collected from the spark streams are studied separately by scanning electron microscope and X-ray diffractometer. Results show that the spark streams are the trajectory of the movement of carbon steel wear debris. The luminescence of the debris is provided by the heat released by the iron oxidation reaction. The carbon burst is caused by the explosion of carbon monoxide (CO) on the surface of carbon steel wear debris, and CO is produced by the reduction reaction of carbon and iron oxides. The main shape of the residues is flaky and spherical. There are some holes caused by carbon burst on the surface of the spherical residues. For the qualitative phase analysis of the residues, the main phase is composed of iron, ferrous oxide (FeO), ferric oxide (Fe2O3), and ferroferric oxide (Fe3O4). As the increase of the carbon content of steel, the quantity of iron phase is greatly reduced, and the quantity of Fe2O3 and Fe3O4 phase is gradually increased. Moreover, the amount and density of carbon burst is increased, and the number of the holes in the spherical residues are also increased.

Measurement of Attitude and Motion of Space Debris in Orbit

Measurement of Attitude and Motion of Space Debris in Orbit

Dynamics and Control of a Two-Spacecraft Coulomb Formation: Challenges and Prospects

The paper is devoted to the issue of active large space debris removal. The contactless method of influencing space debris through the electrostatic interaction is considered. The main advantages of this method are possibility of space debris removal in geosynchronous orbit with low energy costs and absence of a dangerous and complex stage of space debris capturing or docking. This paper introduces the trends and features of a relative attitude dynamics and control of the two-spacecraft coulomb formation. The advantages of the multi-sphere method are discussed for modeling and analyzing the attitude motion of space debris. Two towing schemes (push or pull) are studied in detail. It is shown that the pushing scheme has distinct advantages. The features of the attitude motion of the towed object are identified including chaotic phenomenas and control laws of attitude motion are presented. In the final, the possibilities removal of non-functioning GEO satellites of complicated configuration using electrostatic tug are discussed.

Applicability of tracking simulations for probabilistic assessment of floating debris collision in tsunami inundation flow

ABSTRACTTo improve the applicability of numerical simulations in tracking debris motion for probabilistic assessments of debris collisions with buildings and components installed in coastal industrial sites at a local scale (O (1 km)), the applicability of the numerical approach is investigated through numerical simulations of laboratory experiments. Two characteristic phenomena are found that cannot be expressed by the numerical simulations. The first characteristic phenomenon is debris motion approaching a building model in a reflected wave. To simulate this phenomenon, the incorporation of a turbulent bore model into the numerical model is proposed. The second characteristic phenomenon is debris diffusion due to various perturbations. For simulation of this phenomenon, two approaches are proposed. In the first approach, some causes of debris diffusions are separately modeled. In the second approach, diffusions due to various perturbations are simulated by artificially intensifying debris diffusions. By investigating impacts of the two approaches on probabilistic assessments of debris collision, it is found that debris spreads and the exceedance probabilities of collision speed can be predicted well by considering epistemic uncertainties in determination of diffusion intensity by the latter approach.

Landslide Susceptibility Mapping Using Landslide Numerical Risk Factor Model and Landslide Inventory Prepared Through OBIA in Chenab Valley, Jammu and Kashmir (India)

A landslide is the movement of rock, debris or earth down along the slope under the gravity. It may cause to loss of people’s life and their private and public properties. Landslide is a common hazard in steep slope areas, especially during the rainy season. A study of landslide helps urban planners, engineers and local communities to reduce losses caused by existing and future landslides by means of prevention, mitigation and avoidance. Therefore, the prime aim of this paper is to produce acceptable landslide hazard map for Chenab valley, Jammu and Kashmir. Semiautomatic extraction of the landslide is a suitable method that has been used in this paper to extract the location and extent of the landslides. IRS LISS-IV and CartoDEM have been used for object-based image analysis to extract and prepare a landslide inventory map. About 84 landslide potential sites have been identified by the semiautomatic extraction approach. Landslide numerical risk factor model is derived by using thirteen thematic layers with landslide inventory to prepare the landslide hazard map. The result showed that 21% area of the Chenab valley is falling under the very high hazard zone category of the landslide. The final result of the investigation will definitely be useful in the decision-making procedure at the time of emergency and will be used to prepare a preparedness plan for high-risk areas of Chenab valley. The ROC curve method is used for accuracy assessment that signifies the acceptable result for landslide susceptibility zonation of Chenab valley with 0.956 AUC value.

GIS-ASSISTED RAIN-INDUCED LANDSLIDE SUSCEPTIBILITY MAPPING OF BENGUET USING A LOGISTIC REGRESSION MODEL

Abstract. Landslides are a major concern in disaster risk reduction and management in Southeast Asia due to the region’s geographic location and setting. These are massive downward movement of rock, soil and/or debris under the influence of gravity. Benguet, lying within the Cordilleran mountains of the Philippines, is landslide prone. The increasing demand for sustainable development and expansion of human settlements and infrastructures deems landslides as a problem for the mountainous province. More than half of Benguet’s land area is highly susceptible to landslides. Hence, landslide potential identification and assessment, associated with topography, is vital in ensuring efficiency while minimizing collateral damage and unwanted casualties. This study developed a logistic regression model to map susceptibility to rainfall-induced landslides. Causative factors for the analysis in this study include rock types, soil types, land use, elevation, slope, aspect, precipitation, topographic wetness index (TWI), normalized difference vegetation index (NDVI), and leaf area index (LAI). These layers were prepared using GIS. Based on the logistic regression, the most statistically significant variables were aspect, elevation, and leaf area index (LAI). The model considered with the combination of the causative variables resulted with an R squared value of 86% which indicates good variability for the conditioning factors used for the mapping procedure. Results indicate that 69% of Benguet is highly susceptible to landslides, 7% area is moderately susceptible to landslides, and 24% area is low susceptible to landslides.

Determination of Phase-Eigenvalues by Rational Factorization and Enhanced Simulation of Two-Phase Mass Flow

In this paper, we present simple and exact eigenvalues for both the solid- and fluid-phases of the real two-phase general model developed by Pudasaini (2012); we call these phase-eigenvalues, the solid- phase-eigenvalues and the fluid-phase-eigenvalues. Results are compared by applying the derived phase- eigenvalues that incorporate the phase-interactions in the two-phase debris movements against the simple and classical solid and fluid eigenvalues without any phase interaction. We have constructed several different set of eigenvalues including the coupled phase eigenvalues by using rational factorization method. At first, we consider for general debris height; factorizing the solid and fluid lateral pressure contributions by considering the negligible pressure gradient; negligible solid lateral pressure; negligible fluid lateral pressure; negligible solid and fluid lateral pressure. Secondly, for a thin debris ow height, we also construct the fourth set of eigenvalues in three different cases. These phase-eigenvalues incorporate strong interaction between the solid and fluid dynamics. The simulation results are produced by taking all these different sets of coupled phase-eigenvalues and are compared with the classical uncoupled set of solid and fluid eigenvalues. The results indicate the importance of phase-eigenvalues and supports for a complete description of the phase- eigenvalues for the enhanced description of real two-phase debris flows and landslide motions.

Simulation Study on Gap Flow Field in EDM Micro-hole Machining Based on Gas-liquid-solid Three-phase Flow

In the process of micro-hole machining in EDM, if the debris and bubbles are not removed from the gap flow field, the concentration of debris and bubbles will increase, which will cause arcing discharge and seriously affect the processing efficiency and surface quality. In this paper, the geometric model of three-dimensional cylindrical gap flow field was established. The influence of bubble generation on the gap flow field and the debris under single pulse discharge condition was analyzed by Fluent. Then using the secondary development function of Fluent, the process of the debris and bubble on the bottom surface is continuously generated and the influence of bubble on the movement of debris under continuous discharge conditions were simulated and analyzed. Finally, by considering side flushing, the motion process of bubbles and debris under the conditions of flushing was analyzed.

Effects of river flow velocity on the formation of landslide dams

Natural dams are formed when landslides are triggered by heavy rainfall during extreme weather events in the mountainous areas of Taiwan. During landslide debris movement, two processes occur simultaneously: the movement of landslide debris from a slope onto the riverbed and the erosion of the debris under the action of high-velocity river flow. When the rate of landslide deposition in a river channel is higher than the rate of landslide debris erosion by the river flow, the landslide forms a natural dam by blocking the river channel. In this study, the effects of the rates of river flow erosion and landslide deposition (termed the erosive capacity and depositional capacity, respectively) on the formation of natural dams are quantified using a physics-based approach and are tested using a scaled physical model. We define a dimensionless velocity index vde as the ratio between the depositional capacity of landslide debris (vd) and the erosive capacity of water flow (ve). The experimental test results show that a landslide dam forms when landslide debris moves at high velocity into a river channel where the river-flow velocity is low, that is, the dimensionless velocity index vde > 54. Landslide debris will not have sufficient depositional capacity to block stream flow when the dimensionless velocity index vde < 47. The depositional capacity of a landslide can be determined from the slope angle and the friction of the sliding surface, while the erosive capacity of a dam can be determined using river flow velocity and rainfall conditions. The methodology described in this paper was applied to seven landslide dams that formed in Taiwan on 8 August 2009 during Typhoon Morakot, the Tangjiashan landslide dam case, and the Yingxiu-Wolong highway K24 landslide case. The dimensionless velocity index presented in this paper can be used before a rainstorm event occurs to determine if the formation of a landslide dam is possible.

Effects of electrode rotational speed on processing performances of AISI 304 in micro-electrical discharge machining

Rotating electrodes can effectively improve the processing performance of micro-electrical discharge machining (micro-EDM), but there is still a lack of systematic research on the specific effects of electrode rotation and rotational speed changes. In this paper, the effects of electrode rotation and rotational speed on the discharge channel, debris stress, and debris motion in micro-EDM were analyzed theoretically. An AISI304 sheet was used as the workpiece and helical tungsten carbide alloy as the electrode. The through-hole drilling experiments of micro-EDM were carried out at low and high discharge energy and different electrode rotational speeds. In terms of processing efficiency, the effects of electrode rotation and rotational speed on material removal rate (MRR), relative tool wear ratio (RTWR), and short circuit number were analyzed. The results show that MRR increases first and then decreases, RTWR and short circuit number decrease first and then increase. In the aspect of processing precision, the impacts of electrode rotation and rotational speed on taper angle and overcut were analyzed. The results show that the electrode rotational speed has little effect on the change of the taper angle. In addition, when the electrode rotational speed is small, there is no obvious change in overcut. When the speed is too high, the overcut increases obviously and shows a trend of continuous increase. Finally, by comparing the experimental results, the optimal electrode rotational speeds of micro-EDM with two kinds of discharge energy were determined. The final experimental results also verify the correctness of the previous theoretical analysis.

Investigation and numerical simulation of the 22 February 2018 landslide-triggered long-traveling debris flow at Pasir Panjang Village, Brebes Regency of Central Java, Indonesia

On 22 February 2018 at 08:00 am, a landslide occurred in the dense conserved forest area of the Cigunung Sub-River Basin at Pasir Panjang Village, Brebes Regency of Central Java Province, Indonesia. The landslide materials transformed into debris and flowed down along the river channel rapidly with a distance of more than 2 km, causing 18 people dead and 14 people injured. About 8.5 ha of farm fields, two bridges, 507 m of the provincial road, and 25 houses were destroyed due to the impact of debris flow. This paper reports the site investigation of Pasir Panjang landslide conducted in early June 2018 which covers geological on-site measurement, soil sampling for laboratory tests, and mapping using the unmanned aerial vehicle. Results imply that the source of Pasir Panjang landslide came from a highly weathered layer of volcanic breccia which fails from a steep slope. The landslide materials then entrained weathered tuffaceous sandstone and volcanic breccia layers along the river bank. Hydro-meteorological data shows that the two series of antecedent rainfalls in 10 consecutive days may generate the excess pore water pressure and high saturation condition within the landslide and debris flow area. The balancing depth of saturated soil layer then calculated to estimate the pore water pressure by using the slope infiltration distributed equilibrium model at each time interval of rainfall. We used the LS-RAPID numerical model to simulate the integration of failure mechanism of Pasir Panjang landslide and its debris motion behavior. The simulation results show that the slope fails from the unstable area of approximately 28,000 m2 with the velocity around 13–14 m/s and the maximum depth of 25–26 m. The landslide materials transformed into debris when hit the provincial road with the velocity of more than 30 m/s and traveling down rapidly to the farm field and civilization area. From this study and investigation, we concluded the enlarging volume, flow velocity, and long traveling of the debris materials of Pasir Panjang landslide controlled by the steep slope topography, highly weathered volcanic breccia, and saturated layers in the vicinity of the river and farm field area.

Recolonization of native and invasive plants after large-scale clearance of a temperate coastal dunefield

In the management of alien invasive plants in coastal dunes, plot-based approaches have generally been adopted: researchers establish a set of experimental (often topographically homogeneous) plots of a given size where the plants are removed, and recovery patterns are monitored for a period of time. Therefore, the literature still lacks a detailed understanding of where (i.e., under what topographic circumstances) native and invasive species are likely to recolonize after clearance of a large dunefield. In this study, we report on an unprecedented case from the Sindu dunefield in western Korea in which both native and invasive plants had been thoroughly removed to bare sand over a vast area (ca. 11.0 ha), followed by in situ exhaustive mapping of regeneration patterns throughout the entire cleared zone twelve times within four years. The results showed that, after removal, natives and invaders increased to occupy larger (>50%) areas than those in the pre-removal state. Furthermore, Ecological-Niche Factor Analysis revealed that these two vegetation types exhibited markedly and significantly contrasting regeneration hotspots: invasive plants expanded primarily in low-lying sites that were close to trails. These findings indicate that the recolonization of invasive species was not a spatially random process but rather concentrated along the trails through which local employees transported removed plant material, inadvertently dropping invader propagules. We conclude that removal is often costly, and if executed without a careful plan for the movement of workers, equipment, and plant debris, these efforts may even increase the extent of invasions beyond the initial state.

Sitting Up Vertigo. Proposed Variant of Posterior Canal Benign Paroxysmal Positional Vertigo.

To describe a variant of posterior canal benign paroxysmal positional vertigo (BPPV). Retrospective case review. Tertiary referral center. Fifteen patients with symptoms of BPPV and oculomotor evidence of activation of posterior semicircular canal (P-SCC) cupula that arises when sitting up from Dix-Hallpike maneuver (DH). All patients were examined with videonystagmography and underwent brain magnetic resonance imaging (MRI). All patients showed up-beating nystagmus with ipsilateral torsional component when coming up from right or left side DH. Most patients described vertiginous symptoms when sitting up from bed and many described severe non-positional disequilibrium. Eight patients had been treated with Epley canalith repositioning maneuver (CRM) at our clinic for posterior canal BPPV. Four of them were re-tested within an hour for CRM effectiveness and the rest, a week later. Three patients had been diagnosed with BPPV and were being treated with CRM in other institutions. Four patients showed these findings but they had not previously undergone CRM. All patients were treated with CRM without success, but they resolved their positional vertigo by means of Brandt Daroff exercises. No patient showed evidence of central vestibular disorder. We propose a P-SCC canalolithiasis limited to the periampullar portion by means of an anatomical restriction of distal movement of the otoconial debris. This syndrome seems to be more frequent early after CRM of classical P-SCC canalolithiasis. Close attention to ocular movement on sitting up after DH on patients is warranted.

THE MODEL OF MACRO DEBRIS TRANSPORT BEFORE RECLAMATION AND IN EXISTING CONDITION IN JAKARTA BAY

Jakarta Bay as one of 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, and will also affect the distribution of debris at sea. Therefore, this study conducted is to determine the movement of the marine macro debris before and on the condition of the existing reclamation island in the Bay of Jakarta. The method used is simulated by the hydrodynamic model and particle trajectory models using MIKE software. Data needed for the hydrodynamic model, namely wind, tides, bathymetry, and shoreline, while for the trajectory of the particles using a data type of debris, marine macro debris weight, and debris flux. The analysis was performed for hydrodynamic model simulation results and comparison of particle trajectory models. Hydrodynamics simulations indicate if a reclamation island formation does not change significantly in the offshore area, but a simple change in the surface current pattern of the reclamation area, it also causes a decrease in the flow velocity of ± 0.002 to 0.02 m/s at some point. Macro debris particle trajectory simulation shows if after reclamation, macro debris tends to accumulate in the eastern Jakarta Bay in the rainy season (January), as well as in the western and eastern regions during the dry season (July).

Application of GIS for the mapping of landslide-vulnerable areas by through android-based Analytical Hierarchy Process (AHP) method in Bantul Regency

Landslide is a general term that covers a wide variety of soil forms and processes involving earth, rock, or debris movements falling on the lower slopes below due to the influence of gravity. This disaster occurs in many parts of Indonesia, including in Bantul Regency due to its relatively unstable land and vulnerability to land movement. In addition, a landslide disaster can lead to casualties and considerable material losses. This study aims to build an Android-based GIS application that can map landslide-vulnerable areas by dividing the vulnerability into three categories, namely low, medium, and high, using the Analytical Hierarchy Process (AHP) method. This research is expected to be useful for the community and the Government in order to be alert and responsive to handle landslide disasters in areas that have been declared vulnerable to landslide disasters. The results of research by using the GIS application produced showed that from 17 districts in Bantul Regency, 6 are districts that have a high vulnerability level of landslide disasters. The six districts are Pleret, Imogiri, Kretek, Sanden, Srandakan, and Bambanglipuro.

Tiangong-1\u2019s accelerated self-spin before reentry

The detection and study of the rotational motion of space debris, which is affected by environmental factors, is a popular topic. However, relevant research in extremely low-orbit regions cannot be conducted due to a lack of observational data. Here, we fill in the gaps to present the rotational evolution of Tiangong-1 in the 5 months prior to reentry. Derived from the changes in the relative distance of its two corner cube reflectors from satellite laser ranging data, the angular momentum of Tiangong-1, which is relatively stable during observation, deviates from its maximum principal axis of inertia and precesses around the normal direction of the orbital plane due to gravity gradient torque at an angle of 23.1^circ pm,2.5^circ. Requiring consistency with the relationship between the angular momentum and precession rate leads to a solution for the rotation rate, which is thus found to increase. This result cannot be explained by any previously developed torque models. Hence, an atmospheric density gradient torque (ADGT) model that considers the torque generated by the change in atmospheric density with orbital altitude at the satellite scale is proposed to explain the rotational acceleration mechanism of extremely low-orbit objects. The numerical results show that the ADGT model provides a non-negligible ability to explain, but cannot fully describe, the acceleration effect. The data on the rotational evolution of Tiangong-1 can provide an important basis for aerodynamic model improvement by addressing minor factors omitted in previous models.

Pedestrian evacuation simulation under the scenario with earthquake-induced falling debris

Earthquake-induced collapse of building structures has been effectively controlled in recent years, however, failure of non-structural components and secondary disasters induced by falling debris remain a serious matter, making the outdoor evacuation more dangerous. A pedestrian evacuation simulation framework considering earthquake-induced falling debris is proposed herein, and the associated prediction model to calculate the falling debris distribution is also established. Moreover, experiments are conducted to quantify the influence of falling debris on pedestrian movement. After establishing the evacuation environment, a social force model is adopted to conduct the evacuation simulation. A case study of the teaching area located in Tsinghua University campus is performed using the proposed method for regional evacuation simulation. The results show that when considering the motion of debris after hitting the ground, the width of road covered by debris may be more than twice the first landing distance of debris, especially in densely built-up areas. Besides, whether the debris exists or not has more influence on the total evacuation time. The proposed method can assist with the identification of high-risk areas among the evacuation roads, as well as the provision of scientific basis for future urban planning and emergency evacuation drill development.

Embedded Board Development Interfaced with GPS/IRNSS/NavIC Receiver for Disaster Applications

Landslides are considered to be spontaneous overarching process which results with egregious attack. Landslides are also called as landslip and deals with the loss of assemblage of displacement of movement followed by ground along with falling of rocks. It leads to the loss of slopes deeper and deeper along with debris movement. The transformation of slope from favorable to unfavorable situation followed by certain factors like ground water in order to undermine of the slope, erosion followed by appendage of slope through either river or oceans, diminishing of slope carried by snow melt, deluge of heavy rainfall, earthquakes, etc. Use of navigation grasp the nettle for the prediction of landslide prior to its occurrence and waxed eloquent on it.GPS is considered to be an essential factor in terms of power constraints, accuracy, energy, bandwidths and so on. Sensors are considered to be essential devices as it deals with high sensitivity, less power consumption, linearity, less noise detection and disturbance. Inaccurate placing of the components results in error. Formulation of errors occurs because of station point and set up made for the antenna. Absence of signal includes concealment of satellite signals, presence of interference, barricades, jungles, constructed dwelling and hills. Multiple errors might occur in the presence of undesirable signal reflection with water or fences. Identification of location and timing are oracular sign and plays most important role in prophesy of landslides.

COASTAL FLOODING-INDUCED DEBRIS MOTION

Extreme coastal events such as the 2004 Indian Ocean Tsunami, the 2011 Tohoku Tsunami as well as the 2005 Katrina and 2012 Sandy hurricanes demonstrated that, hydrodynamic loading aside, debris loading represents a major factor in the extreme loading conditions experienced by inland infrastructure. While extreme hydrodynamic loading due to coastal flooding events has been the object of intense research over the past decade, few studies dealing with debris impact due to coastal flooding have been conducted. Post-tsunami forensic engineering field investigations conducted by the authors (Nistor et al. 2005; Shibayama et al., 2006; Nistor et al. 2010) or other researchers (Chock et al. 2012, Sato et al. 2014;) revealed that debris loading and debris damming have a significant effect on the structural integrity of buildings and infrastructure in general, especially in high-density urban areas. Current design guidelines (FEMA P-55, 2011; FEMA P-646, 2012) and the new ASCE-7 Chapter 6 - Tsunami Effects and Loads suggest conservative estimations of the debris spatial spreading based on limited sets of field data to assess debris impact potential (Chock et al., 2012; Naito et al., 2014). The primary objective of this study was to investigate the spatial and temporal displacement of floating debris due to rapid coastal flooding in a built-in port environment using two novel different measuring techniques: (1) high-accuracy video debris detection and tracking system and (2) a real-time locating “smart” sensor-tracking system. Results are compared with prescriptions of the ASCE7 Chapter 6 pertaining to debris motion.

Analysis on anti‐wear mechanism of bionic non‐smooth surface based on discrete phase model

In order to study the lubrication and anti-wear mechanism of the pit-type bionic non-smooth surface used in the low-speed and high-torque seawater hydraulic motor valve plate pair, the discrete phase models of the four pits are simulated under different working conditions. In this study, the trajectories of different diameters particles in the hemispherical pits are analysed, which can reflect the movement of different sizes and masses wear debris in the pits. The discrete phase concentration distributions of the four-kind pits, hemispherical pits, cylindrical pits, four-prism pits and tri-prism pits, are simulation under the same working conditions, which reflects the effect of pit geometry on the movement of wear debris. The discrete phase concentration distributions of four pits moving at different rotation speeds and different rotation radii are calculated, which indicates that the rotation speed of the motor and the distribution of pits on the valve plate will affect the ability of the pit to store wear debris.