Changes In Surface Characteristics Research Articles

Influence of calcination temperature on the 3D nanoscale topography of LaMnO3 thin films: A comprehensive surface analysis

In this paper, we present a comprehensive study on the 3D nanoscale topography of LaMnO3 thin films, focusing on the influence of calcination temperature on surface morphology. The study reveals significant structural, chemical, and morphological changes as a function of the calcination temperature. XRD analysis confirmed the formation of the orthorhombic LaMnO3 structure at 700 °C, 750 °C, and 800 °C, with increasing unit cell volume and crystallite size observed at higher temperatures. FTIR spectra identified characteristic functional groups associated with molecular vibrations, indicating the perovskite structure. SEM imaging showed grain growth with temperature, while EDS analysis confirmed compound formation and substrate interactions. AFM analysis revealed increased surface roughness with temperature, attributed to nucleation and crystal growth. Morphological and microtextural analyses further detailed changes in surface features, peaks, valleys, and voids. Fractal characterization highlighted variations in surface texture with temperature, with a decrease in dominant wavelength indicating changes in microtexture complexity. Overall, the findings provide insights into the temperature-dependent properties of LaMnO3 thin films, essential for optimizing growth conditions and understanding their potential applications in various fields.

The Effect of Silanized Halloysite Nanotubes on the Structure of Polyethylene-Based Composite.

Chemical modification of the surface of halloysite nanotubes (HNT) by alkalization (with sodium hydroxide (NaOH)) and grafting with silanes (bis(trimethylsilyl)amine (HMDS)) was carried out. The efficiency of the alkalization and grafting process was evaluated by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and the nitrogen adsorption method were used. XRD and FTIR analysis confirmed the formation of bonds of trimethylsilyl groups to the HNT surface which changed the nature of the surface from hydrophilic to hydrophobic. In addition, it was noted that grafting with silanes decreases by 7.2% the specific surface area of the halloysite compared to the alkalized material. High-density polyethylene (HDPE) composites with halloysite (HNT), alkalized halloysite (alk-HNT), and HMDS-modified halloysite (m-HNT) were processed in the molten state in a Brabender mixer chamber. On SEM/EDS micrographs of HDPE composites with silanized HNT, a change in surface characteristics from smooth to ductile was observed. Higher melting point values based on differential scanning calorimetry (DSC) analysis of HDPE composites with 5%wt silanized halloysite in comparison with HNT and alk-HNT of, respectively, 2.2% and 1.4% were found, which indicates a slight beneficial influence of the filler on the quality of ordering of the crystalline phase of the matrix.

The implementation method of point cloud denoising filter based on KinectV2

Abstract In the process of collecting data from point clouds, some factors, such as precision equipment, operator experience, environmental conditions, as well as characteristic diffraction effects of electromagnetic waves, changes in surface characteristics of test objects, and the impact of integration processes, are involved data and records that may display some point noise in the data point cloud. In addition to noise caused by measurement errors, practical applications can be affected by external interference and obstacles, which causes deviating values in the data point cloud to differ from the measurement entity. A 3D scanner, represented by the depth of the camera, is used to collect data. To eliminate these noises and anomalies, it is necessary to filter the initial points of the cloud. In this article, we suggest using statistical filtering algorithms to perform statistical analysis on each point community, remove points that do not meet predetermined standards, and remove outliers. To verify the effectiveness of the algorithm, it is compared with other filtering algorithms. The experimental results show that the filter algorithm proposed in this thesis has better effects on outlier points and can obtain the general shape properties of the point cloud.

Size reduction of biochar to nanoscale decrease polycyclic aromatic hydrocarbons (PAHs) and metals content and bioavailability in nanobiochar

Objective of this research was to investigate ball milling of biochar from various feedstocks (willow, rice husk, oilseed rape, sewage sludge) under different pyrolysis conditions (500 and 750 °C, N2 and CO2 atmosphere) on polycyclic aromatic hydrocarbons (PAHs) and metals content. A significant reduction in both total (Ctotal Σ16) (1.1 to 2.4-fold decrease) and freely available (Cfree Σ16) (1.1 to 2.9-fold decrease) PAHs in nanobiochar (n-BC), particularly in sewage sludge (SSL)-derived n-BC was observed. The changes in biochar surface characteristics induced by ball milling, such as surface area, pore volume, and hydrophilicity, contribute to the decreased PAHs content. Mechanisms involving mechanochemical degradation, free-radical reactions, and defects on the biochar surface may explain the decrease of PAHs. The n-BC showed lower log Kd values for PAHs (reduced by 14 to 41 %) compared to bulk biochar (b-BC), indicating reduced effectiveness in immobilizing PAHs. The ball milling significantly reduced also metal contents by 37 to 55 %, especially in willow pellets and agricultural residue (rice husk and oilseed rape straw) with optimal reduction (by 55 %) observed for WL-derived n-BC produced at 650 °C. Importantly, no metals were detected in the aqueous phase after ball milling, ensuring environmental safety of these materials. Reduction mechanisms of metals during ball milling include stable aggregate formation, enhanced defects in crystalline structures, and irreversible adsorption onto new surfaces. The results demonstrate that the application of an eco-friendly ball milling method allows for the production of materials characterized by reduced contamination levels, which is crucial from an environmental protection viewpoint.

Recombinant Production of Hydrophobin DewA in Pichia pastoris and Determination of Its Functions

Background Hydrophobins have great potential in many biotechnological applications due to changing surface characteristics. In recent years, although there has been a significant increase in the biotechnological applications of hydrophobins, industrial production has still not been achieved due to yield problems. Therefore, more studies are needed on the recombinant production of hydrophobins. In this work, the recombinant production of class I hydrophobin DewA from Aspergillus nidulans, which is determined to have high contact angle in the literature, was aimed. As a result, DewA protein was recombinantly produced using P. pastoris X-33 strain under AOX1 promoter by transferring into pPICZα-A vector. Results The optimal culture condition for DewA expression was obtained at 1% methanol concentration as 77 mg/L in 96 hour. Recombinant DewA has been proven to change the surface characteristics on the teflon and glass surfaces. Then, the surface stability of the protein was evaluated by applying hot SDS and UV to these surfaces. The surface-coated DewA was resistant to hot SDS application on both glass and teflon surfaces; in the UV application, it was understood that while the protein was degraded by UV exposure on glass surfaces, it preserved its structure on teflon surfaces. Conclusions In the study, the DewA protein of A.nidulans was cloned into the pPICZα-A vector and recombinantly produced in the P.pastoris X-33 strain for the first time.

Effect of bioceramic powder abrasion on different implant surfaces.

Bioceramic coatings have been shown to promote bone repair, which aids in the early integration of implants. This study aimed to evaluate the influence of air abrasion with a bioceramic abrasive on the surface characteristics of different implant materials and surfaces. The dissolution of the applied treatment from the surfaces over 3 weeks was also assessed. Discs of three alloys used for dental implants were studied and compared: two types of commercially pure titanium (CpTi)/ (CpTi SLActive) and titanium-zirconia (TiZr). The tested surfaces were: CpTi control (CpC), sandblasted (SB), sandblasted and acid-etched (SBE), and CpTi SLActive®, (TiZr) Roxolid®. Three discs from each group underwent air abrasion with apatite bioceramic powders, 95% hydroxyapatite (HA)/5% calcium oxide (CaO), and 90% hydroxyapatite (HA)/10% calcium oxide (CaO). The treated discs were surface characterized by optical profilometry to obtain surface roughness, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS) to compare element weight percentages of titanium, calcium, and phosphate. Dissolution was assessed using inductively coupled plasma optic emission spectrometry (ICP-OES). Bioceramic powders were deposited on all tested surfaces leading to changes in surface characteristics. The only statistically significant differences between the material groups for surface roughness were found with 95% HA/5% CaO powder in the Sp and Rp parameters (p = 0.03 and 0.04, respectively). There were no significant differences in the Ca and P wt% between all groups and powders 95% HA/5% CaO and 90% HA/10% CaO (p = 0.14, 0.18, and p = 0.15, 0.12, respectively). A non-uniform dispersion of the treatment on the surface layer was visible on all treated surfaces. The bioceramic powder continued to dissolute from the tested surfaces for 3 weeks. Bioceramic abrasion modifies implant surface characteristics, although the change in surface characteristics resulting from such treatment was not influenced by the implant material or surface treatment. Air abrasion with hydroxyapatite and calcium oxide bioceramics leaves powder deposits on the treated implant surfaces that could potentially influence the healing of implants affected by peri-implantitis.

Enhancing methane production potential of biodegradable plastics by hydrothermal pretreatment

Anaerobic digestion (AD) is considered a promising method to treat biodegradable plastic (BP) wastes, while low CH4 production yields (MPYs) of BPs limit field application of AD. To overcome such limitation, the impact of hydrothermal pretreatment (HTP) on MPYs of four commercial BPs such as polylactic acid (PLA), polyhydroxyalkanoate (PHA), polybutylene adipate terephthalate (PBAT), and polybutylene succinate (PBS) was investigated in this study. Solubilization efficiencies of BPs increased as BPs were pretreated under higher temperature and longer duration. After pretreatment at 150 °C for 3 hr, MPYs of PLA, PHA, PBAT, and PBS under mesophilic conditions were 450–460, 530–545, 165–175, and 460–490 L CH4/kg VS, respectively, which were significantly higher than one of untreated BPs. Pretreatment temperature was found to be the most important parameter affecting CH4 production from BPs compared to pretreatment duration and particle size. It was confirmed that HTP could depolymerize the long polymeric chain in BPs into the monomers of each BP, such as lactate, 2-butenoic acid, 1,4-butanediol, and succinic acid, together with significant changes in surface characteristics. Such changes might be the main reasons for enhancing CH4 production from BPs. These results suggest that the application of HTP to AD can potentially offer to treat diverse BP waste simultaneously with high CH4 production efficiency.

Soil erosion resistance of gully system under different plant communities on the Loess Plateau of China

AbstractGully erosion, considered as a type of intensive erosion, is the dominant source of sediment at small watershed scales in certain environments. Variation of vegetation may result in the changes in near soil surface characteristics, which likely further affect the resistance of gully systems to erosion. However, the potential effects of near soil surface characteristics of plant communities on resistance to erosion are still unclear in gully systems. This study was performed to investigate the variations in resistance of gully systems to erosion under different plant communities and to identify the dominant influencing factors leading to these variations on the Loess Plateau. Five typical plant communities (two grasses, two shrubs and one forest) that distributed on different gully systems were selected. Six hundred undisturbed soil samples collected from different sites of gully systems were subjected to detach by overland flow under six different shear stresses (6.66 to 15.02 Pa). The results showed that the mean soil detachment capacity of gully systems covered by grass and shrub communities was 0.15 and 0.37 times to that of gully system covered by forest. Compared to forest gully systems, rill erodibility reduced by 29.8% to 85.6% for the other four plant communities. The relative rill erodibility of different vegetation communities generally increased from grass to shrub and forest communities. The critical shear stress of forest gully system was 58.7% and 63.8% of gully systems covered by grass (6.22 Pa) and shrub (5.73 Pa) communities. Bulk density, soil cohesion, water stable aggregate, root mass density, and the thickness of biological soil crust were the dominant factors affecting the resistance of gully systems to soil erosion. Rill erodibility decreased logarithmically with increasing soil cohesion, water stable aggregate and root mass density. Critical shear stress increased with the increase of soil cohesion and root mass density as a power function, and linearly with the increase of water stable aggregate. These results show how vegetation can mitigate against the erosion induced by concentrated flow in relatively stable gully systems.

Sub-Surface Soil Characterization Using Image Analysis: Material Recognition Using the Grey Level Co-Occurrence Matrix Applied to a Video-CPT-Cone

The geotechnical characterization of the subsurface is a key requirement for most soil investigations, incl. those for reclaiming landfills and waste dumps associated with mining operations. New sensor technology, combined with intelligent analysis algorithms, allow for a faster and less expensive acquisition of the necessary information without loss of data quality. The use of advanced technologies to support and back up common site investigation techniques, such as cone penetration testing (CPT), can enhance the underground characterization process. This study aims to investigate the possibilities of image analysis for material recognition to advance the geotechnical characterization process. The grey level co-occurrence matrix (GLCM) image processing technique is used in a wide range of study fields to estimate textures, patterns and structure anomalies. This method was adjusted and applied to process the video recorded during a CPT sounding, in order to distinguish soil types by its changing surface characteristics. From the results of the video processing, it is evident that the GLCM technique can identify transitions in soil types that were captured in the video recording. This enables the prospect of image analysis not just for soil investigations, but also for monitoring of the conveyor belt in the mining field, to allow for efficient preliminary decision making, material documentation and quality control by providing information in a cost effective and efficient manner.

Cavitation resistance of laser-sintered MS1 steel

This study focuses on the determination of cavitation rate for samples produced by Direct Metal Laser Sintering (DMLS) of MS1 maraging steel powder without any post-processing thermal or mechanical treatment (as-built). The test samples, fabricated using an EOSINT M280 machine in a nitrogen atmosphere, were evaluated for their cavitation resistance using the ultrasonic vibration method as proposed by the ASTM G32 standard. Surface characterization to determine the duration of the experiment, as well as during and after the experiment to analyze changes in surface characteristics, was conducted using Scanning Electron Microscopy (SEM). Additionally, chemical analysis was performed using the Energy Dispersive X-ray Spectroscopy (EDS) method before and after the experiment to identify any changes and locations of significant surface damage. The mass loss of the samples over time was measured to calculate the cavitation rate. The goal of this research was to explore the potential applications of laser-sintered MS1 steel powder for manufacturing machine components and parts that are subject to cavitation erosion, due to the numerous benefits of additive manufacturing over traditional conventional technologies.

Sertraline associated with gold nanoparticles reduce cellular toxicity and induce sex-specific responses in behavior and neuroinflammation biomarkers in a mouse model of anxiety

This study aimed to evaluate the effects of sertraline associated with gold nanoparticles (AuNPs) in vitro cell viability and in vivo behavior and inflammatory biomarkers in a mouse model of anxiety. Sertraline associated with AuNPs were synthesized and characterized. For the in vitro study, NIH3T3 and HT-22 cells were treated with different doses of sertraline, AuNPs, and sertraline + AuNPs and their viability was evaluated using the MTT assay. For the in vivo study, pregnant Swiss mice were administered a single dose of lipopolysaccharide (LPS) on the ninth day of gestation. The female and male offspring were divided into five treatment groups on PND 60 and administered chronic treatment for 28 days. The animals were subjected to behavioral testing and were subsequently euthanized. Their brains were collected and analyzed for inflammatory biomarkers. Sertraline associated with AuNPs exhibited significant changes in surface characteristics and increased diameters. Different doses of sertraline + AuNPs showed higher cell viability in NIH3T3 and HT-22 cells compared with sertraline alone. The offspring of LPS-treated dams exhibited anxiety-like behavior and neuroinflammatory biomarker changes during adulthood, which were ameliorated via sertraline + AuNPs treatment. The treatment response was sex-dependent and brain region–specific. These results suggest that AuNPs, which demonstrate potential to bind to other molecules, low toxicity, and reduced inflammation, can be synergistically used with sertraline to improve drug efficacy and safety by decreasing neuroinflammation and sertraline toxicity.

A Review on Carbon Nanotubes and its Biomedical Applications

Abstract: Carbon nanotubes, as their name implies, are nanotubes made of carbon. Carbon nanotubes, liposomes, dendrimers, quantum dots, nanogels, and others are carbon nanoparticles. CNTs are synthesized using a variety of processes, including laser ablation, chemical vapor deposition, and arc discharge. Each method affects the nanotubes' final structure, diameter, and chirality, which affects their qualities and future applications. Furthermore, CNT functionalization and doping allow for changes in surface characteristics, compatibility with various materials, and improving performance in multiple applications. Carbon nanotubes are used in drug delivery systems to transport drugs from one place to another to achieve therapeutic effects. Carbon nanotubes have a wide variety of applications like those used in gene therapy, the treatment of cancer, diagnosis, tissue regeneration or engineering, etc. Moreover, CNTs (carbon nanotubes) have been recently revealed as promising antioxidants. They have great results in medicine and pharmacy. Its simple structure, high thermal and electronic conductivity, and nanometer size attract. Carbon nanotubes can deliver proteins, bioactive peptides, drugs, and nucleic acids to organs and cells. CNTs have a thin graphene sheet, which classifies them and changes their functions. This manuscript covers carbon nanotube history, classification, and applications

Surface, Structural, and Electrochemical Analysis of High-Voltage Spinel Cathode LiNi0.5Mn1.5O4 Evolution Upon Ambient Storage Conditions

Spinel LiNi0.5Mn1.5O4 as one of the high-energy positive electrode materials for next generation Li-ion batteries has attracted significant interest due to its economic and environmental advantages. However, the sensitivity of this type of material upon short to long term ambient storage conditions and the impact on the electrochemical performances remains poorly explored. Nevertheless, this remains an important aspect for practical large-scale synthesis, storage and utilization. Herein, we study and compare the evolution of surface chemistry, bulk crystal structure and elemental content evolution and distribution of LiNi0.5Mn1.5O4 using a variety of characterization techniques including XPS and STEM-EDS-EELS, as well as electrochemical analysis. We show that Mn species dominate the outer surface (0–5 nm), while Ni and Li are preferentially located further away and in the bulk. The studied LiNi0.5Mn1.5O4 material is found to be stable, with minor changes in surface or bulk characteristics detected, even after 12 months of storage under ambient air conditions. The low surface reactivity to air also accounts for the minor changes to the electrochemical performance of the air-exposed LiNi0.5Mn1.5O4, compared to the pristine material. This study provides guidance for the appropriate storage, handling and processing of this high-performance cathode material.

Nickel ion release and surface analyses on instrument fragments fractured beyond the apex: a laboratory investigation

BackgroundTo analyse the changes in surface and nickel ion release characteristics of fractured root canal shaping instruments in a simulated body fluid environment.MethodsA total of 54 new instruments were studied. The instrument groups consisted of five different NiTi alloys and a stainless-steel alloy. To standardize instrument fracture, a torsional type of failure was created on each instrument. The fractured specimens of each instrument group were randomly divided into three static immersion subgroups of 1 h, 7-day, and 30-day (n = 3). Simulated body fluid (SBF) was prepared to mimic human blood plasma by Kokubo&Takadama protocol for ex situ static immersions at 37ºC. The surfaces were examined via scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. To determine the quantitative ion release, the retrieved SBFs were analyzed using inductively coupled plasma mass spectrometry. Two-way ANOVA and Tukey post hoc tests sought the statistical significance of the nickel ion values(p < 0.05).ResultsIn 1 h of immersion, the newly formed structures, exhibiting mostly oxygen signals, were widespread and evident on NiTi surfaces. In contrast, fewer structures were detected on the SS surface in that subgroup. In 7 days of immersion, a tendency for a decrease in the density of the new structures was revealed in NiTi groups. The oxygen signals on NiTi group surfaces significantly increased, contrary to their decrease in SS. Signals of sodium, chlorine, and calcium were detected, indicating salt precipitates in groups. In 30 days of immersion, salt precipitates continued to form. The Ni-ion release values in all instrument groups presented significant differences in comparison to the SBF control in all immersion periods(p < 0.001). No significant differences were observed in immersion time periods or instrument groups(p > 0.05).ConclusionsWithin the limitations of the presented study, it was concluded that the fractured SS and NiTi root canal instruments release Ni ions in contact with body fluid. However, the Ni ion release values determined during the observation periods are lower than the critical toxic or allergic thresholds defined for the human body. This was due to the ionic dissolution cycle reaching a stable state from 1-hour to 30-day exposure to the body fluid of fractured instruments.

Surface Mesonet and Upper Air Analysis of the 21 August 2017 Total Solar Eclipse

The total solar eclipse of 21 August 2017 was unique in that the path of totality swept across the high spatial and temporal resolution QuantumWeather® mesonet and was very near the city of St. Louis Missouri. Thus, the meteorological response to the eclipse was complicated by the St. Louis urban heat island. Temperature changes of up 4 °C were observed across the network. Composite meteograms for rural, suburban, and urban stations displayed significant differences in the observed temperature and pressure response to the eclipse with a peak amplitude at the time of the eclipse. The differing response suggests that the urban heat island and changes in land surface characteristics alter the temperature and pressure response by the passage of the eclipse shadow. Oscillations in the composite meteograms appear to be the consequence of the passage of an outflow boundary across the network. As the outflow boundary moves north to south, the outflow boundary manifests its presence in the pressure field as a damped oscillation. Sounding data were collected along the center line of eclipse and along the southern edge of the eclipse before and during the eclipse. The soundings show that the eclipse altered the boundary layer height, the lowest layer of the atmosphere, in an unexpected way.

Optical profilometry for forensic bloodstain imaging.

Understanding the physical, chemical and biological changes that occur during the drying of a bloodstain is important in many aspects of forensic science including bloodstain pattern analysis and time since deposition estimation. This research assesses the use of optical profilometry to analyze changes in the surface morphology of degrading bloodstains created using three different volumes (4, 11, and 20 μL) up to 4 weeks after deposition. We analyzed six surface characteristics, including surface average roughness, kurtosis, skewness, maximum height, number of cracks and pits, and height distributions from the topographical scans obtained from bloodstains. Full and partial optical profiles were obtained to examine long-term (minimum of 1.5-h intervals) and short-term (5-min intervals) changes. The majority of the changes in surface characteristics occurred within the first 35 min after bloodstain deposition, in agreement with current research in bloodstain drying. Optical profilometry is a nondestructive and efficient method to obtain surface profiles of bloodstains, and can be integrated easily into additional research workflows including but not limited to time since deposition estimation. Optical profilometry is a non-contact tool to scan bloodstains in ambient conditions Drying phases are observable in small drip bloodstains Significant surface morphology changes occur within 35 min after deposition.

Nucleate boiling enhancement on bubble-induced assembly of graphene oxide/carbon black hybrid networks

The efficiency and capacity of nucleate boiling can be enhanced by the bubble-induced assembly of nanoparticles, which are dispersed in a boiling liquid. Recently, carbon nanomaterials have attracted appreciable research interest for boiling heat transfer enhancement. This study presents nucleate boiling performance on interconnected graphene/carbon black hybrid films formed through the bubble-induced self-assembly of suspended particles. Aqueous graphene/carbon black hybrid solutions at varying concentration ratios (GO:CB; 1:0, 1:1, 1:5) were prepared via probe sonication. The solutions were then saturated and subjected to pool boiling under atmospheric pressure on a custom-made boiling test apparatus with a flat copper heating surface. Experiments were carried out at a stepwise increasing heat flux until the critical heat flux was reached. A heat transfer coefficient and critical heat flux enhancement of 223.0% and 182.4%, respectively, were achieved at a GO:CB concentration ratio of 1:5. The change in surface characteristics and, subsequently, the boiling performance were elaborated by conducting a series of surface characterizations such as Field Emission Scanning Electron Microscopy, Energy Dispersive X-Ray analysis, contact angle analysis, and surface profilometry. Nucleate boiling enhancement was attributed to the contribution of multiple factors such as surface roughening, increased effective surface area, decent interfacial contact within the assembly structure, improved capillarity, and lateral heat conduction.

Effect of Hydrophobic Moieties on the Assembly of Silica Particles into Colloidal Crystals

To boost the implementation of colloidal crystals (CCs) in separation science, the effects of the most common chromatographic reversed phases, that is, butyl and octadecyl, on the assembly of silica particles into CCs and on the optical properties of CCs are investigated. Interestingly, particle surface modification can cause phase separation during sedimentation because the assembly is highly sensitive to minute changes in surface characteristics. Solvent-induced surface charge generation through acid-base interactions of acidic residual silanol groups with the solvent is enough to promote colloidal crystallization of modified silica particles. In addition, solvation forces at small interparticle distances are also involved in colloidal assembly. The characterization of CCs formed during sedimentation or via evaporative assembly revealed that C4 particles can form CCs more easily than C18 particles because of their low hydrophobicity; the latter can only form CCs in tetrahydrofuran when C18 chains with a high bonding density have extra hydroxyl side groups. These groups can only be hydrolyzed from trifunctional octadecyl silane but not from a monofunctional one. Moreover, after evaporative assembly, CCs formed from particles with different surface moieties exhibit different lattice spacings because their surface hydrophobicity and chemical heterogeneity can modulate interparticle interactions during the two main stages of assembly: the wet stage of crystal growth and the late stage of nano dewetting (evaporation of interparticle solvent bridges). Finally, short, alkyl-modified CCs were effectively assembled inside silica capillaries with a 100 μm inner diameter, laying the foundation for future chromatographic separation using capillary columns.

A Review on Life Prediction Methods of Gun Barrel

In large caliber gun system, the high speed, high temperature and high pressure gas produced by propellant combustion will cause serious erosion damage to the inner wall of barrel, which will lead to continuous decline of gun performance and termination of the maximum life of barrel. The theories and methods of gun barrel life prediction mainly involve thermodynamics, chemistry, material and machinery science and so on. This paper mainly introduces the main mechanism of gun erosion and the calculation model of gun erosion which involves the numerical solution in internal ballistic combustion process, the heat transfer and erosion calculation of gun barrel. In view of the accurate calculation of parameters such as the temperature of gunpowder gas can more accurately reflect the erosion of inner wall of gun barrel, this paper summarizes the calculation methods of the temperature, thermal physical property parameters and convective heat transfer coefficient of high temperature and high pressure gas in gun barrel. In order to determine the erosion wear quantity and study the effect of heat input on the erosion process of inner wall of gun, erosion experiments are usually required. At present, the common erosion experiments mainly include the measurement of erosion quantity with semi-closed explosive device and the change of surface characteristics of gun steel target with laser pulse heating. By analyzing the criterion of barrel life, the establishment method of barrel life prediction model is studied deeply, and the main barrel life prediction model is introduced, which is convenient to guide engineering application.

Last deglacial abrupt climate changes caused by meltwater pulses in the Labrador Sea

Freshwater perturbations are often thought to be associated with abrupt climate changes during the last deglaciation, while many uncertainties remain regarding the exact timing, pathway, mechanism, and influence of meltwater release. Here, we present very well-dated and high-resolution records from the eastern Labrador Sea representing the last 19.000 years, which demonstrate abrupt changes in sea surface characteristics. Four millennial-scale meltwater events have been identified between the last 14.000 and 8.200 years based on independent biomarker proxies and X-ray fluorescence scanning data. These events are characterized by increased sea ice formation and decreased sea surface temperatures which might have occurred within a few decades. We propose these abrupt changes were triggered by meltwater pulsing into the Labrador Sea periodically, resulting from collapse of the Laurentide-Greenland Ice Sheets caused by (sub-)surface ocean warming in the Labrador Sea. Our findings provide more precise information about impact of freshwater forcing on abrupt climate changes, which may help to improve simulations for past and future changes in ocean circulation and climate.