Crater Creation Research Articles

Impact of landmark crater creation on improving accuracy of pedicle screw insertion in robot-assisted scoliosis surgery.

This study evaluated the impact of the Landmark Crater (LC) method on pedicle perforation rates in robot-guided surgery for pediatric scoliosis for each pedicle diameter. Seventy-six scoliosis patients underwent robot-assisted posterior spinal fusion. The cohort consisted of 19 male and 57 female patients, with a mean ± standard deviation age of 17.5 ± 7.7 years and a preoperative Cobb angle of 57.0 ± 18.5°. The LC method is a method in which craters that serves as a landmark are created in advance at the planned PS insertion site of all pedicles within the intraoperative CT imaging area. The patients were divided into the LC group, in which PS insertion was performed using the LC method, and the control group using the conventional PS insertion method. Overall and pedicle perforation rates for each pedicle outer diameter were compared between the groups by Fisher's exact test. The LC group exhibited a significantly lower pedicle major perforation rate than did the control group (2.7% vs. 6.2%, P = 0.001). The perforation rates in pedicles with a pedicle outer diameter > 6mm, 4-6mm, 2-4mm, and < 2mm were 0.61%, 1.6%, 5.1%, and 21%, in the LC group and 0.75%, 4.1%, 12%, and 50% in the control group, respectively. In robot-assisted surgery for pediatric scoliosis, the LC method enabled significantly lower pedicle perforation rates over the conventional method. Both the LC and conventional methods exhibited higher perforation rates for smaller pedicle diameters.

Elevation Anomalies of the Volcanic Floor Unit and Their Relationships to the Multiple Lakes of Jezero Crater, Mars

AbstractWe reassessed several orbital topographic data sets for the Perseverance rover landing site at Jezero Crater, Mars to better understand its floor units. Tens‐of‐meters deep topographic anomalies occur in the volcanic floor of Jezero crater and are not a result of impact cratering. Eight km‐scale steep escarpment‐bounded depressions may be locations of paleotopographic highs that were embayed by the volcanic floor lava flows, forming inverted topography from either contemporaneous upward inflation of embaying lavas or later deep scour due to differential erosion over 107−9 years. Five multi km‐scale shallow‐sloped depressions linked by channel‐like forms may record locations of buried paleolakes and channels that predate the volcanic floor units or a drained magma system. These results indicate Jezero experienced multiple closed‐basin or dry phases, allowing erosion of the crater floor and creation of topography, which provides new geologic context for the samples gathered by Perseverance.

Failure Prevention in Large-Diameter Water Pipelines Using Reliability-Centered Maintenance

The consequences of failures from large-diameter water pipelines can be severe. Results can include significant property damage, adjacent damage to infrastructure such as roads and bridges resulting in transportation delays or shutdowns, adjacent structural damage to buildings resulting in loss of business, service disruption to a significant number of customers, loss of water, costly emergency repairs, and even loss of life. The Washington Suburban Sanitary Commission (WSSC) in the United States found that flooding was the greatest concern due to its potential duration, the potential for broad geographic impact, and its role in crater creation. Public safety, property damage, social and economic consequences, and loss of water service and for how long is also of paramount concern. The American Water Works Association’s (AWWA) 2020 “State of the Water Industry” report states that the top issue facing the water industry since 2016 is aging infrastructure, with the second being financing for improvements. The industry needs to find novel ways of extending asset life and reducing maintenance expenditures. While there are many different assets that comprise the water/wastewater industry, pipelines are a major component and are often neglected because they are typically buried. Reliability-Centered Maintenance (RCM) is a process used to determine the most effective maintenance strategy for an asset, with the ultimate goal being to establish the required function of the asset considering the required reliability and availability at the lowest cost. The RCM philosophy considers Preventive Maintenance, Predictive Maintenance, Condition Based Monitoring, Reactive Maintenance, and Proactive Maintenance techniques in an integrated manner to increase the probability an asset will perform its designed function throughout its design life with minimal maintenance. RCM requires maintenance decisions be based on maintenance requirements supported by sound technical and economic justification. However, one industry where principles of RCM are in its infancy is the water/wastewater industry. This paper provides a case example and numeric modeling for use in RCM analyses for developing maintenance strategies for large-diameter water pipelines, particularly prestressed concrete pipelines, and proposes an approach for determining the most effective and efficient maintenance activities for large-diameter prestressed concrete water pipelines. The case study discussed in this paper analyzed wire breaks over time to predict when certain thresholds would be reached. The intent of this study is to predict when a specified threshold will be reached. From the RCM, a threshold was set to begin planning, budgeting, and scheduling maintenance activities when 55% of the wires in a frame or two adjoining frames are distressed or when 65% of the wires in non-adjacent frames are distressed. The results from the numeric model predict the 55% threshold may be reached in August 2025 for the most distressed pipe segment.

A Step-Wise Workflow for SAR Remote Sensing of Perennial Heaving Mound/Crater on the Yamal Peninsula, Western Siberia

Climate change in the Arctic region is more significant than in other parts of our planet. One of the manifestations of these changes is crater creation with blowouts of a gas, ice and frozen soil mixture. In this context, dynamics studies of long-term heaving mounds that turn into craters as a result are relevant. A workflow for detecting and assessing anomalous dynamics of heaving mounds in the Arctic regions is proposed. Areas with anomalous increase of ALOS-2 PALSAR-2 synthetic aperture radar (SAR) backscattering intensity are detected in the first stage. These increases take place due to sudden changes in local terrain slopes when the scattering surface (mound slope) turns toward the radar. Radar backscattering intensity also rises due to depolarization at newly formed frost cracks. Validation of the detected anomaly is carried out at the second stage through a comparison of multi-temporal digital elevation models obtained from bistatic radar interferometry TerraSAR-X/TanDEM-X data. At the final stage, the deformations are assessed within the detected areas using differential SAR interferometry (DInSAR) technique by ALOS-2 PALSAR-2 data. The magnitude of the heaving along the line of sight (LOS) was 22–24 cm in the period from January 2019 to January 2020. In general, effectiveness for detecting the perennial heaving mounds and the rate assessment of their increase were demonstrated in the suggested workflow.

The effect of crater creation on the surface of steel targets under irradiated of high-current pulsed electron beams

The present paper reviews the experimental results dedicated by the effect of the irradiation conditions by intense pulsed electron beams on crater creation taking place on the surface of EP866sh refractory steel targets. The most probable mechanisms of crater creation are also described.

Deployable Camera (DCAM3) System for Observation of Hayabusa2 Impact Experiment

An asteroid exploration probe “Hayabusa2”, that was developed by Japan Aerospace Exploration Agency (JAXA), was launched on December 3rd, 2014 to challenge complicated and accurate operations during the mission phase around the C-type asteroid 162137 Ryugu (1999 JU3) (Tsuda et al. in Acta Astron. 91:356–362, 2013). An impact experiment on a surface of the asteroid will be conducted using the Small Carry-on Impactor (SCI) system, which will be the world’s first artificial crater creation experiment on asteroids (Saiki et al. in Proc. International Astronautical Congress, IAC-12.A3.4.8, 2012, Acta Astron. 84:227–236, 2013a; Proc. International Symposium on Space Technology and Science, 2013b). We developed a new micro Deployable CAMera (DCAM3) system for remote observations of the impact phenomenon applying our conventional DCAM technology that is one of the smallest probes in space missions and gained a great success in past Japanese mission IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun). DCAM3 is a miniaturized separable unit that contains two cameras and radio communication devices for transmission image data to the mothership “Hayabusa2”, and it observes the impact experiment at an unsafe region in where the “Hayabusa2” is difficult to stay because of a risk of exploding and impacting debris hitting. In this paper, we report details of the DCAM3 system and development results as well as our mission plan for the DCAM3 observation during the SCI experiment.

Dynamics of ripple formation on silicon surfaces by ultrashort laser pulses in subablation conditions

An investigation of ultrashort pulsed laser--induced surface modification due to conditions that result in a superheated melted liquid layer and material evaporation are considered. To describe the surface modification occurring after cooling and resolidification of the melted layer and understand the underlying physical fundamental mechanisms, a unified model is presented to account for crater and subwavelength ripple formation based on a synergy of electron excitation and capillary wave solidification. The proposed theoretical framework aims to address the laser--material interaction in subablation conditions and thus the minimal mass removal in combination with a hydrodynamics-based scenario of the crater creation and ripple formation following surface irradiation with single and multiple pulses, respectively. The development of the periodic structures is attributed to the interference of the incident wave with a surface plasmon wave. Details of the surface morphology attained are elaborated as a function of the imposed conditions, and results are tested against experimental data.

New Data on the Post-Impact Material in Radiolarian Horizons in Outer Flysh Carpathians and Search for a Source Crater

New Data on the Post-Impact Material in Radiolarian Horizons in Outer Flysh Carpathians and Search for a Source Crater In the Outer Carpathians in Barnasiówka radiolarian shale formation, there is an intercalation underlied by bentonite. There were found very rare elements and minerals in this intercalation. It was recognized that this horizon has been filled with products of a big object collision with Earth. The age of the manganese-iron intercalation was determined by potassium-argon (K-Ar) dating of illites to be (89.3±1.2) Ma. Similar age, (85.2±0.6) Ma, was found for the post-impact glass from the Boltysh crater in Ukraine. It was concluded that the formation of this intercalation was synchronous with the Boltysh crater formation at the Cenomanian/Turonian boundary. The research for the K-Ar age of the crater creation in Logoisk (Belarus) established its formation to (124.2±1.2) Ma ago.

Recent highlights of the PALS research program

The Prague Asterix Laser System (PALS) research program covers a broad spectrum of laser–plasma experiments in the range of power densities of 1014-5 × 1016W/cm2, aimed at development and applications of laser plasma-based ion and soft X-ray sources of plasma based ultra-bright XUV lasers in particular. In parallel to these two main lines of research, various principal tasks of laser plasma physics are being studied, such as generation and propagation of laser-induced shock waves, laser ablation, and crater creation processes or laser imprint treatment. Results selected of numerous experimental projects performed at PALS within the period 2002–2004 are surveyed in the paper, experiments with intense soft XUV laser beams being highlighted on the first place.

Investigation of Shock Wave Loading and Crater Creation by Means of Single and Double Targets in the PALS-Laser Experiment

The efficiency of crater creation for different types of Al targets, namely, single massive targets and double targets consisting of a foil or a disk placed before the massive target at a chosen distance (300 and 500 µm), is studied. Targets were irradiated by the PALS facility laser beam with E L = 100 – 400 J at the first harmonic λ = 1315 nm, a focal spot radius of 125 µm, and pulse duration of 400 ps. Velocities of the accelerated foil’s fragments or disks and electron density distributions of the plasma streams are determined by means of three-frame interferometry. Shapes and volumes of craters are obtained using the crater replica technology and microscopy measurements. It is shown that direct laser action is the most efficient way of energy transfer to the massive target and the most efficient method of crater creation. Somewhat lower efficiencies of shock wave loading and crater creation in comparison with direct laser action are found in the case of double targets where the energy is transferred to the massive target by colliding laser-driven foils or disks. The efficiencies of such a colliding energy transfer are close to 60% for foils and 40% for disks. The experimental results are in a good agreement with two-dimensional hydrodynamic models of shock wave generation under direct laser action and laser-driven macroparticle impact.

Investigation of the wavelength influence on the efficiency of macroparticles acceleration and craters creation in the PALS double targets experiment

This paper describes investigation of efficiency of macroparticles acceleration and craters creation processes for two wavelength of the PALS facility laser beam: λ1 = 1.315 μm and λ3 = 0.438 μm, and different types of targets made of Al: single massive targets and double targets consisting of a foil or a disk (thickness of 6 μm) placed before the massive target at the distance of 200 or 500 μm. Targets were irradiated by the iodine laser beam:EL=130 J for the both harmonics, the focal spot diameter of 250 μm, and the pulse duration of 400 ps. Velocities of accelerated extracted foil fragments or disks as well as electron density distributions of plasma streams were determined by means of 3-frame interferometry. Shapes and volumes of craters were obtained employing crater replica technology and microscopy measurement. This investigation has shown, that the shorter wavelength is much more effective, i.e. velocity of macroparticles accelerated by means of the third harmonic is 2÷2.5 times higher in comparison with that for the first harmonic whereas the crater volumes are about 5 times larger. Efficiencies of macroparticles acceleration and crater creation by means of foil fragments and disks are similar and with respect to craters creation by direct laser beam action amount to 60% and 40÷45% for the first and the third harmonic, respectively.

The effect of crater creation on the fatigue strength and corrosion resistance of steels and titanium alloys irradiated by high-power pulsed ion beams

The effect of high-power pulsed ion-beam (HPPIB) irradiation and various methods of the surface treatment on the crater creation phenomenon (cratering) was examined with the use of Auger electron spectroscopy, X-ray diffraction analysis, and scanning electron microscopy. The crater distribution density, sizes and shape, along with the microhardness and chemical composition inside and outside them were determined. It was shown that cratering on the surface of refractory alloys is due to the cathode material erosion and the nonstability in the physical and chemical state of the irradiated targets. The samples were treated with HPPIB. The irradiated samples were subjected to fatigue and corrosion tests. It was established that cratering leads to catastrophic fracture of the irradiated targets under the cycle load. For example, as a result of crater creation, the fatigue strength of VT18U alloy was decreased from 380 to 240 MPa. In this case the nucleation of fracture lies near the craters. Furthermore, the titanium alloys irradiated by HPPIB are subjected to pitting corrosion in seawater. It was shown that according to the test results, adjacent and dent-shape craters are the most dangerous defects under the cycle load.

Crater formation by ion bombardment as a function of incident angle

Ion bombardment of surfaces at an angle with respect to the surface normal produces surface modification with more varied and rich features than normal incidence bombardment. This allows more possibilities for nanopatterning and surface processing. Megaelectronvolt ion bombardment of insulators can create a track of electronic excitations which can decay non-radiatively and couple to the lattice, leading to sputtering and crater creation. Using molecular dynamics simulations we present a systematic study of the craters produced by a cylindrical track of excitations with its axis at several angles with respect to the surface normal (in the range Θ=0–80°). We also use different energy densities inside the track, from 0.5 nU to 12.5 nU, where n is the density of the material and U its binding energy. Crater length is found to vary as cos −1 Θ.

Plastic flow in FCC metals induced by single-ion impacts

Irradiation of Au and Pb foils with Xe ions at temperatures between 30 and 450 K has been monitored using in situ transmission electron microscopy. Single ion impacts give rise to surface craters on the irradiated surface with sizes as large as 12 nm. Approximately 2%–5% of impinging ions produce craters on Au while only about 0.6% produce craters on Pb. Larger craters on Au frequently have expelled material associated with them. Temporal details of crater formation and annihilation has been recorded on video with a time-resolution of 33 ms. Craters annihilate in discrete steps due to subsequent ion impacts or anneal in a continuous manner due to surface diffusion. Craters production (those persisting for one or more video-frames) as a function of temperature indicates that the surface diffusion process responsible for thermal annealing of craters has an activation energy of 0.76 eV in Au. Crater creation results from plastic flow associated with near surface cascades. Crater annihilation in discrete steps results from plastic flow induced by subsequent ion impacts, including those that do not themselves produce a crater.

Heavy ion cratering of gold

Irradiation of gold films with Xe ions in the energy range 50{endash}400 keV has been monitored using {ital in situ} transmission electron microscopy. Craters are produced and annihilated on the irradiated surface at all ion energies studied. Approximately 2{endash}5{percent} of impinging ions in the energy range 50{endash}400 keV produce craters with sizes as large as 12 nm for the higher-energy irradiations. Crater annihilation occurs in discrete steps, due to subsequent ion impacts, or by annealing in a continuous manner due to surface diffusion processes. Crater creation results from flow associated with near surface cascades. Discrete crater annihilation results from plastic flow induced by ion impacts, including those that do not themselves leave a crater, and annealing that may occur during the quenching phase of cascade thermal spikes. {copyright} {ital 1997} {ital The American Physical Society}

Effects of holmium: YAG laser energy on cartilage metabolism, healing, and biochemical properties of lesional and perilesional tissue in a weight-bearing model.

Comparison of perilesional cartilage, lesional repair tissue, and subchondral bone activity 6 months after application of holmium-yttrium-aluminum-garnet (Ho:YAG) laser energy to chronic (10 week) induced 10-mm full-thickness (FT) circular articular cartilage craters followed by 6 months' intermittent active motion (IAM) in a free exercise environment was investigated. The 2.1-microns wavelength was delivered in hand-controlled near-contact mode by arthroscopic surgery in a saline medium. Bilateral arthroscopy was performed on normal antebrachiocarpal, intercarpal, and metacarpophalangeal joints of six adult horses. Full-thickness craters were created in nine sites per limb on weight-bearing articular surfaces with a motorized bur. Right limb craters served as sham operated controls. Animals were killed at 10 weeks after FT crater creation (n = 2), and at 24 weeks (6 months) after laser energy application (n = 4). Histological analysis using hematoxylineosin (HE) and Safranin-O staining consisted of a modified Mankin grading of perilesional cartilage and lesional repair tissue scoring. Biochemical analysis was performed for cellularity and glycosaminoglycan (GAG) synthesis. Histological analysis showed clustering of chondrocytes or perilesional zonal cloning (PZC) in 83% of laser-treated lesions and in no control lesions. No differences were observed between treated and control lesional repair activity. Laser-treated perilesional cartilage showed a significant (P < .02) decrease in GAG synthesis. No adverse effects to distant cartilage were observed after application of laser energy regarding cell proliferation or GAG synthesis. Significance of decreased GAG synthesis in treated perilesional cartilage and perilesional zonal cloning of chondrocytes in treated cartilage is unknown. Additional study of Ho:YAG laser energy application to cartilage and subchondral bone is needed before its application in the surgical management and repair of cartilage damage.

The analysis of tiiin films by SSMS - A more detailed discharge model and recent experiments

Surface analysis and depth profiling by SSMS demands that the spark craters have a small and reproducible shape. A detailed knowledge of vacuum spark progress and sample erosion processes is a prerequisite for control of these parameters. Consideration of the various RF single spark stages — prebreakdown, breakdown initiation, spark and are — shows that spark crater creation takes place mainly during breakdown initiation and spark stages. Estimates show that only ≈1% of the total power density of a single spark is consumed by sample erosion. Possible methods for controlling the power density of single sparks (additional R and C, respectively) are described and their analytical application to layers (thickness 0.1–10 μ) is demonstrated. The main processes for initiation and maintenance of RF spark discharge in a vacuum and the erosion of the anodic sample have been described on the basis of published data and investigations carried out by the authors. The depths and areas of craters formed during breakdown at the sample surface have been studied. It has been found that the total power density consumed by a single spark is of the order of q σ ≈ 3 × 10 8 W CM 2̄, whereas the power density dissipated at the anode surface is as low as q a ≈ 3 × 10 6 W cm 2̄. The values of q a and qσ are nearly independent of the gap width 1. The crater depth is mainly determined by q a and the length of the current period t 1. Possible methods of influencing these parameters have been discussed. The analytical applications described indicate that SSMS is able to analyze layers of thickness between ≈0-.1 and 10 μm.