Debris Material Research Articles

A Magnetized, Moon-forming Giant Impact

Abstract The Moon is believed to have formed in the aftermath of a giant impact between a planetary-mass body and the proto-Earth. In a typical giant impact scenario, a disk of vapor, liquid, and solid debris forms around the proto-Earth and—after possibly decades of evolution—condenses to form the Moon. Using state-of-the-art numerical simulations, we investigate the dynamical effects of magnetic fields on the Moon-forming giant impact. We show that turbulence generated by the collision itself, shear in the boundary layer between the post-impact debris field and the proto-Earth, and turbulence in the vapor component of the disk amplify the field to dynamically significant strengths. Magnetically driven turbulence promotes angular momentum transport in the protolunar disk. Debris material is accreted onto the proto-Earth, making Moon formation less efficient, while the disk is forced to spread to larger radii, cooling at its outer edge. Magnetic fields speed the evolution of the vapor component of the protolunar disk and hasten the formation of the Moon.

New simple method for measuring impact force on a flexible barrier from rockfall and debris flow based on large-scale flume tests

Accurate determination of impact loads is of great necessity for safe and economical design of flexible barriers. Nevertheless, measurement of the impact force on a flexible barrier is still an open problem due to the highly deformable flexible net under impact and stress concentration on force transducers. In this study, large-scale flume tests with new design of instrumentation were adopted to validate and optimise existing methods for measuring the impact forces on a flexible barrier. Specifically, single-boulder impact tests were conducted to verify the accuracy of those methods. A debris flow impact test was performed to quantitatively investigate the dynamic behaviour of a flexible barrier under the impact of a debris flow. Thanks to the well-designed instrumentation, the impact force distribution characteristics of a debris flow on a flexible barrier are discovered. During the interaction process, the debris flow first impacted on the bottom area of the flexible net, then the dynamic impact moved up with gradual deposition of debris material. It is found that the impact pressure on the central area of the net is much larger than that on two sides. Therefore, triangular-shaped load distribution is used to optimise the existing methods for measuring the impact force induced by a debris flow. Attributable to the good accuracy and simple instrumentation requirement, a new simple method can be generalized for real-time monitoring of impacts on flexible barriers installed in natural terrains

Finite Element Model of a Melting Terminal Debris Bed in a CANDU Calandria

Abstract Melting of the terminal debris bed at the bottom of a Canada deuterium uranium (CANDU) 6 calandria vessel during a severe accident is studied using a three-dimensional transient finite element analysis. Settling of the debris is modeled, as are the effects of changing temperature and porosity on debris material properties. The time and magnitude of maximum heat rejection from the debris bed, and the maximum mass of molten debris, are calculated as functions of the accident timing. The results are compared with those from the modular accident analysis program (MAAP)-CANDU severe accident code.

Numerical analyses of the influence of baffles on the dynamics of debris flow in a gully

After the 2008 Ms 8.0 Wenchuan earthquake, a huge amount of loose debris materials were accumulated on the surface of slopes in the mountainous areas of Southwestern China. Under heavy rainfalls and earthquakes, these loose debris materials can flow, washed away, and subsequently enter the mountainous rivers due to landslides and debris flows. They can change the sediment supply of the river channel and result in the adjustment of riverbed. To mitigate the adverse impacts, baffles are usually installed on slopes in front of the protected areas to reduce the kinetic energy of incoming debris flows. In order to clarify the interacting mechanism between debris materials and baffles structure, the dynamics of granular transportation and deposition in a typical gully have been analyzed via the three-dimensional discrete element method (DEM). The numerical results indicate that the arrangement of baffles (e.g., spacing distance, layout row, and height) has a significant influence on the dissipation of debris energy and the final sediment deposition pattern. The kinetic energy, the velocity of granular flow, and the total mass of debris materials entering the river channel decrease with the increase of the baffles lateral spacing distance, layout row, and height. Correspondingly, the amount of debris materials retained by the baffles will increase. Thickness and volume of particle deposits in the upstream region increased with increase in lateral spacing, rows, and height of the baffles, but decreased in the downstream area. In addition, the baffle configuration can affect the particle size distribution along the channel. The results of this research can provide a theoretical basis for baffle designs and the prevention of debris flows in mountainous areas.

Impact of air pollution on reproductive health in Afghanistan

The presence of one or more contaminants (harmful substances) in the atmosphere in a specific quantity, for such duration, which is injurious or tends to be injurious to human health, welfare, animal, or plant life is called air pollution. Air pollutants are of commonly two types, which are produced through natural pollutants; they include dust (crustal material), sea salts, biological material, pollen, spores or plant-animal debris, volcanic eruptions (which release a very large quantity of gases and particles into the atmosphere), periodic forest fires, thunderbolts, wind erosion, and low concentration ozone. Other types of pollutants are produced in human-made (technical) environments, like mobile sources (cars, trucks, airplanes, marine engines, etc.) or point sources (factories, electric power plants, etc.). The high level of air pollution is a big problem all over the world and also in Afghanistan, and all residents of this country are severely exposed to this ever-worsening situation. Air pollution and other extraordinary environmental problems are factors that threaten the livelihood of millions of Afghans, as a study report shows that 60% of Kabul’s residents are exposed to increased levels of harmful toxins, such as, nitrous oxides and sulfur dioxide. According to the State of Global Air report, more than 26,000 afghan deaths could be attributed to pollution in 2007, but United Nations Assistance Mission in Afghanistan (UNAMA) documented nearly 3,500 civilian casualties from the war for the same time period, so air pollution is killing more Afghans than war because they burn anything possible to get energy and heat they need. Result of air sampling in major urban centers of Afghanistan shows high amounts of particulate matters (PM), benzo-a-pyrene, and polycyclic aromatic hydrocarbons (PAHs) originating from vehicle exhaust emission. The highest concentrations were founded in Kabul and Mazar-e-Sharif (13.6 ng/m3 ). The absence of industrial parks, nonconformity of environmental protection rules, especially by industries, urbanization, degradation of fertile lands, deforestation, seasonal winds, drought, internal migration, and low knowledge about pesticides and herbicides use, are factors that boost the severity of air pollution in Afghanistan. In Afghanistan, women are more exposed to high levels of indoor air pollution because they spend more time at home due to their cultural rules; also, women have responsibility for household activities, working in the kitchen to prepare food, they are exposed to poor sanitation and contaminated water supplies, they clean and sweep rooms and yards with inadequate protection equipment, which are significant sources of dust, so they are often exposed to high levels of smoke and dust for long periods.

Unified constitutive model for granular–fluid mixture in quasi-static and dense flow regimes

Most granular materials encountered in nature and industry lie either in the quasi-static regime or the intermediate dense flow regime. Debris materials are a typical granular material with viscous interstitial fluid and show solid-like behaviors before failure and fluid-like behaviors after failure. Based on Bagnold’s pioneering work on granular–fluid flows, we propose a framework for constitutive model development, which has an additive form. Based on this framework, a unified constitutive model for granular–fluid material in the quasi-static and dense flow regimes is developed. The main intergranular interactions and granular–fluid interactions controlling the mechanical behaviors are taken into account using the Mohr–Coulomb model and a Bagnold-type relation. Dry granular flows in three simple configurations, i.e., plain shear, vertical chute flow and flow on an inclined plane, are studied. Analytical solutions based on the presented unified model are obtained. Comparisons between results from the presented model and the $$\mu (I)$$ model indicate that the explicit partition of frictional and collisional stress components provides insights into dense granular flows. In addition, the new model is used to predict the stress–strain relations in two annular shear tests. The applicability and advantages of the unified model are discussed.

Experimental and numerical study of dynamic soil debris impact load on reinforced concrete debris-resisting barriers

In Hong Kong, design practice adopts the hydrodynamic load model to estimate the dynamic soil debris impact load on reinforced concrete debris-resisting barriers. A dynamic coefficient of 2.5 is empirically adopted, which takes into account the effect of the impact of boulders up to 0.5 m in diameter. With a view to rationalising the design of reinforced concrete debris-resisting barriers, the Geotechnical Engineering Office (GEO), in collaboration with the Hong Kong University of Science and Technology (HKUST), initiated a study to investigate the dynamic impact of soil debris. In particular, a series of large-scale impact tests using 4 m3 realistic debris mix and a 1.8-m-high reinforced concrete model barrier were conducted in the flume facility in the Kadoorie Centre in Hong Kong. The tests were well controlled, and the flow kinematics, including flow depth and flow speed, and the time history of the impact load at the wall stem subject to the debris impact were measured, which provided critical test data on assessment of the hydrodynamic load of soil debris hitting reinforced concrete structures. The scale of these physical impact tests under such a controlled environment was unique as compared with other studies in the literature. To further examine the dynamic impact force, a calibrated numerical model using a three-dimensional finite-element computer package, namely LS-DYNA, was adopted to simulate the impact scenario for a real-scale debris flow event of 400 m3, where an arbitrary Lagrangian-Eulerian technique was adopted to simulate debris materials. Based on both the experiments and numerical analyses, debris run-up along the wall stem was observed when the debris hit the model barriers. Under the experimental setting, the hydrodynamic soil debris pressure coefficients were consistently found close to unity, which are generally in line with that used in overseas technical guidelines or design practice. This study enhances fundamental understanding of the soil debris impact mechanism on reinforced concrete barriers and provides scientific evidence to rationalise the design guidelines used in Hong Kong.

Processes controlling the development of talus slopes in SW Spitsbergen: The role of deglaciation and periglacial conditions

AbstractThe location of Svalbard at the interface between the warm Atlantic and cold Arctic oceans causes the terrestrial environment to be highly sensitive to contemporary climate warming. Talus slopes provide a component of glaciated areas that has been registering these changes on a scale of several thousand years. However, knowledge about their development during glacial recession is still limited. This paper fills this gap by providing unique data obtained by geophysical methods: electrical resistivity tomography (ERT) and ground‐penetrating radar (GPR), regarding the talus slopes in Revdalen (SW Spitsbergen), which was last glaciated in the Neoglacial period. The results indicate that the thickness of talus slopes depends first of all on the size of the sediment supply area and only secondarily on the stage of development. The initial content of buried glacial ice in the talus deposits is differential and depends on both the rate of deglaciation and the local intensity of rock wall denudation. Over time, as a result of creep, the presence of massive ice is limited to ever lower parts of the slope. Above, there is aggradation of pore ice in delivered debris material. At the end of this stage, the buried glacial ice can form, or co‐create together with pore ice, the core of subslope rock glaciers. The relatively long period since the beginning of the Revdalen deglaciation allowed a general model of the development of talus slopes in the polar environment to be prepared.

Numerical study of retention efficiency of a flexible barrier in mitigating granular flow comparing with large-scale physical modeling test data

Retention behavior of a flexible barrier in mitigating a granular flow is still an open problem not fully understood, especially due to the complexity of the granular material and the flexible barrier. Understanding the retention mechanism and quantifying the influencing factors of retention efficiency are desirable for optimizing the design and minimizing the maintenance cost of a debris-resisting flexible barrier. In this paper, a numerical model, based on the discrete element method, is presented, calibrated, and validated to analyze the interaction between a granular flow and a flexible net. A full-scale numerical simulation is first performed to compare with a large-scale physical modeling test in the literature and validate the applied parameters in the simulation. The interaction and deposition characteristics of the granular flow interacting with a flexible net are revealed. Afterward, parametric study is performed to investigate the effects of the internal friction angle (φ) of debris material and the relative mesh size of flexible net on the retention efficiency and clogging mechanism of a flexible barrier. The simulation results illustrate that the particle passing ratio (P) increases with increment of the friction angle of particles and enlargement of the mesh size of a flexible net. Both parameters have critical effects on the retention efficiency of a flexible barrier in intercepting a granular flow. Therefore, the friction angle and the particle size distribution characteristics of the debris material are suggested being used for optimization of the mesh size and more efficient design of debris-resisting flexible barriers.

The Difference of Irrigant Solution between Red Pine Extract (Pinus densiflora) and Green Pine Extract (Pinus merkusii) Against Cleanliness of Root Canal Walls

Background: Smear layer is an accumulation of organic material, debris, and inorganic material in root canal wall. Irrigant solution must be able to eliminate organic and inorganic materials. Herbal extract such as pine contain saponins that can dissolve organic and inorganic materials. Korea is a country that has used pine in this case red pine as an antibacterial medicament. In Indonesia, there are also green pine species. Purpose: To explain the differences in cleanliness of the root canals after irrigation using extracts of red pine (Pinus densiflora) and green pine (Pinus merkusii). Methods: This study used twenty-seven mandibular premolar teeth which were divided into 3 groups each group consisted of 9 premolar teeth. All samples were prepared using ProTaper for Hand Use and irrigated. Group I was irrigated using 2.5% NaOCl, group II was irrigated with red pine extract, and group III was irrigated using green pine extract. Tooth that has been prepared, were cut vertically into 2 and cut horizontally in 1/3 apical section. The root canal surface was observed using a scanning electron microscope. Photomicrograph was observed by three observers using a score and performed an analysis test. Results: There were no difference between red pine (Pinus densiflora) and green pine (Pinus merkusii) in root canal cleanliness with a significance value of 0.169 (p> 0.05) Conclusion: Red pine extract had the same smear layer cleaning power as green pine extract.

SUN-LB86 Case Report: Killian-Jamieson Diverticulum Presenting as a Thyroid Nodule

Introduction: Multitudinous endocrine and non-endocrine disorders cause thyroid nodules, thus in an effort to diagnostically exclude various thyroid malignancies, endocrinologists are obligated to perform a thorough investigative workup. A Killian-Jamieson diverticulum (KJD) is a rare form of cervical esophageal diverticulum that results from anterolateral, mucosal protrusion below the cricopharyngeal muscle. Due to the vicinity of the thyroid gland, this lesion can mistakenly present as a thyroid nodule. Case Description:A 71-year-old female with a past medical history of invasive ductal carcinoma clinical stage 1A, T1a/bN0M0 grade 1 ER+PR+HER2- with treatment composed of radioactive seed localized partial mastectomy and sentinel lymph node biopsy, whole breast radiotherapy, and anastrozole therapy was referred to an endocrinology clinic for evaluation of a left 1.0 cm thyroid nodule incidentally discovered on a CT without contrast scan conducted for bronchitis. Immediate pre-office TSH level collected was normal at 3.28 mIU/L and thyroid ultrasound (US) demonstrated a left lower lobe 2.0 cm AP x 1.7 cm transverse x 2.1cm cephalocaudad heterogenous, solid, well-circumscribed, microcalcified, TI-RADS 4 nodule. In the endocrinology office, the patient’s only symptoms were hoarseness, an improving cough, and neck stiffness. The blood pressure collected was 128/74. Office physical exam demonstrated thyromegaly without nodules. The patient met criteria for a fine-needle aspiration (FNA). A first FNA performed was an uncomplicated biopsy of the lesion, but demonstrated insufficient cellularity on pathology. A second FNA performed was also an uncomplicated biopsy of the lesion, and demonstrated squamous cells, debris material suggestive of vegetable material, and rare benign follicular epithelial cells. Fluoroscopic esophagram was performed subsequently demonstrating a moderate left-sided KJD. Discussion: While literature exists documenting the etiology, pathogenesis, and medical/surgical treatments for KJDs, only a few case reports exist reporting the resemblance KJDs have with thyroid nodules. This case report hopes to illustrate non-endocrinology pathologies that can mimic thyroid nodules while encouraging current healthcare practitioners to recognize the existence of these conditions so that wasteful diagnostic tests or invasive procedures can be avoided.

Role of baffle shape on debris flow impact in step-pool channel: an SPH study

Drainage channels with step-pool system are widely used to control debris flow. The blocking of debris flow often gives rise to local damage at the steps and baffles. Hence, the estimation of impact force of debris flow is crucial for designing step-pool channel. Existing empirical models for impact pressure prediction cannot consider the influence of baffle shape. In this work, a three-dimensional smoothed particle hydrodynamics (SPH) study on the impact behavior of debris flows in step-pool systems is presented, where debris material is modeled using the regularized Bingham model. The SPH method is first checked using the results from two laboratory tests. Then, it is used to investigate the influence of baffle shape and flow density. Numerical results show that the impact pressure at the first baffle highly depends on the baffle shape; however, the largest impact pressure usually occurs at subsequent baffles due to the violent impact induced by jet flows. The peak impact pressure at the first baffle initially grows with increasing flow density; however, it starts to drop as density is beyond a threshold. Based on the numerical results, an empirical relation considering the influence of baffle shape is proposed for better prediction of debris impact pressure.

Load-Settlement Behavior of Concrete Debris Pile in Fly Ash Fill

Abstract This study addresses the problem of disposal and effective reuse of waste material, fly ash, and construction concrete debris in order to find an optimized solution for their bulk disposal...

Critical deflagration criterion of PTFE/Al/W reactive materials

The unique reaction regime of reactive materials includes processes of impact-induced fracture, pre-ignition, post-perforation dispersion, local initiation, and deflagration. The complex interaction between reactive materials and target leads to difficulty in describing critical deflagration criterion of reactive materials. As such, a fundamental projectile/target interaction condition for the complete deflagration of reactive material fragment is derived based on the 1-dimensional shock wave relationships. The critical deflagration pressure Pc of reactive materials is fitted based on the energy release experiments of reactive material fragments. The results show the importance and necessity of the fracture behavior to the deflagration, and the deflagration behavior depends on impact velocity, geometry of reactive material fragment, target material and thickness, et al. As for the deflagration of fractured reactive materials behind the target, the critical deflagration size for reactive material debris is obtained based on the Grady energy model.

Application of high power pulsed nanosecond fibre lasers in processing ultra-thin aluminium foils

This study is directed at developing a micro-scale laser scoring process and understanding the laser-material interaction in ultra-thin aluminium foils (160 μm thickness). The research is carried out by the latest generation of nanosecond pulsed fibre lasers manufactured by SPI Lasers. Presented comparative analysis of 70 W and 120 W laser types gives important insights for laser functionality and can provide recommendations for scalability of the process and quality assurance. High average power lasers were used to meet the requirement of high processing speed in aluminium foils. Scoring in aluminium foils was analysed using the fundamental laser-material interaction parameters that fully determine the way the material responds to the laser energy independent of the laser system. This approach permits transferring the results from the micro-scale laser process between various laser systems. Energy density and laser power density calculated for considered beam spot area at various frequencies were found to be the parameters that determine the scoring ablation depth in the range of 40 μm–60 μm. Microscopic examination of the ablation depth and score quality was carried out by an LED illumination 3D microscope. The SEM micrographs indicated minor growth of material debris from the ejected material.

Wear debris of friction materials for linear standing-wave ultrasonic motors: Theory and experiments

This study focuses on the wear debris of different friction materials for linear standing-wave ultrasonic motors (SWUMs). Wear debris with different morphology and sizes derive from wear mechanisms and has a critical influence on the contact state. The generation mechanisms of the wear debris are analyzed by using the elastic-plastic indentation mechanics and the typical morphography of the wear debris are discussed by considering of the energy balance. Oxide ceramics with high strength and fracture toughness were used as the friction materials of the driving tips, which are in contact with the carbon steel and oxide ceramic sliders. The wear tests were conducted using a homemade reciprocating apparatus. The worn surfaces and debris of different couples were investigated by scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS). The statistical results of the debris size analysis were consistent with the results of the theoretical analysis of the indentation fracture mechanics. The wear debris was characterized with regard to size parameters, roundness factor, aspect ratio, and fractal dimension using image processing, and the relationships of the parameters and the wear modes are discussed. The generation mechanisms of the wear debris differ for the different friction couples due to the complex states and the differences in the mechanical properties. The plastic factor (E/H) and brittleness factor (H/KIC) are critical to the maximum dimension of the wear debris for given friction couples.

Reactor environment during the Fukushima nuclear accident inferred from radiocaesium-bearing microparticles

Radiocaesium-bearing microparticles (CsMPs), which are substantially silicate glass, were formed inside the damaged reactor and released to the environment by the Fukushima Dai-ichi Nuclear Power Plant accident in March 2011. The present study reports several valuable findings regarding their composition and structure using advanced microanalytical techniques. X-ray absorption near-edge structure of Fe L3-absorption indicated that the oxidation state of the iron dissolved in the glass matrix of the CsMPs was originally nearly divalent, suggesting that the atmosphere in which the CsMPs were formed during the accident was considerably reductive. Another major finding is that sodium, which has not been recognised as a constituent element of CsMPs thus far, is among the major elements in the glass matrix. The atomic percent of Na is higher than that of other alkali elements such as K and Cs. Furthermore, halite (NaCl) was found as an inclusion inside a CsMP. The existence of Na in CsMPs infers that seawater injected for cooling might reach the inside of the reactor before or during the formation of the CsMPs. These results are valuable to infer the environment inside the reactor during the accident and the debris materials to be removed during the decommissioning processes.

An extreme May 2018 debris flood case study in northern Slovenia: analysis, modelling, and mitigation

Debris floods can cause large economic damage and endanger human lives. This paper presents an extreme May 2018 debris flood that occurred in northern Slovenia near the Krvavec ski resort and caused large economic damage. The debris flood was initiated by an extreme rainfall event with a return period of over 50 years. There were large differences in the measured rainfall amounts using different equipment. The estimated volume of the debris material during the event was 4000 m3/km2 for the Brezovski graben. In order to mitigate the risk due to future debris flood and debris flow events, a check is planned to be constructed. The part of the design process is presented in this paper. Additionally, RAMMS model was used to validate the empirical equations that were used in the process of the check dam stability design. The model was calibrated using information about the deposition area. Two adjacent torrents were modelled, and we were not able to find a common RAMMS parameter set that would yield adequate simulation performance in both cases.

The Meso‐Analysis of the Rock‐Burst Debris of Rock Similar Material Based on SEM

In order to explore the specimen failure characteristics during rock‐burst under different gradient stress conditions, in this paper, a novel experimental technique was proposed; a common series of tests under two gradient stress paths were conducted on rock similar material specimens using the true‐triaxial gradient and hydraulic‐pneumatic combined test apparatus. And plaster was used as the rock similar material. In the experimental process, several rock‐burst debris with area sizes of 100 mm2 were collected, and the fractal dimensions of typical detrital section crystal contours were analyzed and calculated using a scanning electron microscopy (SEM) method. The results showed that the specimens’ failure characteristics which had been induced by the two gradient stress processes were various. Also, the mesoscopic morphology of the rock‐burst detrital section had effectively reflected its macroscopic failure characteristics. It was found that the fractal dimensions of the crystal contours of the specimen’s detrital section had fractal characteristics, and the box‐counting dimension based on the SEM image could quantitatively describe the rock‐burst failure characteristics. Furthermore, under the same magnification, the fractal dimensions of the crystal contours of the splitting failures were found to be relatively smaller than those of the shearing failures.

Emission rate assessment of airborne brake particles by characterization of the pad and disc surfaces from a pin-on-disc tribometer

Particles from brake, road and tire wear contribute to about half of the emissions (PM10) of particulate traffic pollution. It is estimated that 50 to 70% of the brake debris material is transformed into an emission of polydisperse aerosols. In order to improve the understanding of the brake debris generation and its dependency on the brake material, the wear of a disc and a brake pad from a standard production car were studied. The disc was made of perlitic cast iron with lamellar graphite and subjected to standard braking cycles. Microscopic evaluation was performed on the disc track, as well as analyses by Energy Dispersive Spectroscopy (EDS). Finally, a metallographic section has been made in the longitudinal direction of friction to better understand the morphology. The study focuses on disc surface oxidation and morphology of a thin layer on both disc and pin surface. Particle concentrations increase with the friction power and the area of contact surface. The observations show that the generation of particles can be the result of the oxidation of the disc surface during friction by two- and three-body abrasion when braking.