To improve the effect of table tennis tactical analysis, this study proposed a table tennis video tactical analysis method based on image fuzzy edge recognition algorithm. This algorithm can ...effectively recognize edges in images to improve recognition accuracy and reduce errors and rejection rates. In addition, this research combines the methods of target tracking and trajectory estimation to build a table tennis video game tactical analysis platform. The experimental data show that the recognition accuracy of the proposed fuzzy edge recognition algorithm is 98.1%, and the error and rejection rates are less than 1.6%. Compared with the image edge detection algorithm based on interval value fuzzy, the proposed algorithm has better performance. When the positioning error is 10%, the precision of the table tennis target tracking algorithm can reach 94.3%, which is 9.3% higher than that of the direct linear transform algorithm. The table tennis video game tactical analysis platform can analyze the velocity of ping-pong ball according to the video, and records the droppoint of ping-pong ball, which helps the players to develop more effective tactics and strategies to improve their competitive level and achievements.
An important mechanism of carbonate mineral growth is dissolution-reprecipitation, including the transformation of amorphous precursor to crystalline carbonates, and coarsening (ripening) of fine ...carbonate crystals. However, the mechanistic details of cation exchange associated with carbonate mineral growth via a dissolution-reprecipitation process are still not well understood. In this study, we used Mg isotopes to probe the exchange of Mg between aqueous solutions and norsethite BaMg(CO3)2 by systematic synthesis experiments. Norsethite is a model double carbonate, with a general formula of AB(CO3)2, where A and B stand for two different divalent ions. Formation of norsethite is comprised of three stages, including: (1) precipitation of barium-magnesium (Ba-Mg) amorphous carbonate; (2) transformation of Ba-Mg amorphous carbonate to nano-crystalline norsethite by fast dissolution-reprecipitation; and (3) coarsening (ripening) of nano-norsethite by slow dissolution-reprecipitation. Magnesium isotopes displayed distinct fractionation behaviors in each of the three stages. The Mg isotope fractionation factors (Δ26Mgsolid-aq) associated with precipitation of Ba-Mg amorphous carbonate were slightly negative and temperature-dependent, from -0.83 per mill at 30°C to -0.83 per mill at 70°C. During the transformation of Ba-Mg amorphous carbonate to nano-crystalline norsethite, isotopically light Mg isotopes were further enriched in the solid phase, with apparent Δ26Mgsolid-aq decreasing to -2.12 per mill at 30°C and -1.56 per mill at 70°C. In the ripening stage, norsethite became isotopically heavier, with Δ26Mgsolid-aq increasing up to -1.95 per mill at 30°C and -1.17 per mill at 70°C. The experimental results show that non-equilibrium isotope fractionation occurred during the transformation of amorphous carbonate to nano-crystalline norsethite (i.e., fast dissolution-reprecipitation). By contrast, the subsequent ripening of the norsethite led to the evolution toward isotopic equilibrium of the system by slower exchange with a longer reaction time (i.e., slow dissolution-reprecipitation). Moreover, our first-principles calculation results indicate that the equilibrium isotope fractionation was approached, but not attained, even after 276 days of recrystallization at temperatures below 70°C. In short, this study has identified two different types of dissolution-reprecipitation process during the carbonate mineral growth and highlights the importance of understanding formation mechanism and post-depositional history of carbonate in interpreting the isotopic data of carbonate minerals.
Banded iron formations (BIFs) record a time of extensive Fe deposition in the Precambrian oceans, but the sources and pathways for metals in BIFs remain controversial. Here, we present Fe- and ...Nd-isotope data that indicate two sources of Fe for the large BIF units deposited 2.5 billion y ago. High-ε Nd and -δ âµâ¶Fe signatures in some BIF samples record a hydrothermal component, but correlated decreases in ε Nd- and δ âµâ¶Fe values reflect contributions from a continental component. The continental Fe source is best explained by Fe mobilization on the continental margin by microbial dissimilatory iron reduction (DIR) and confirms for the first time, to our knowledge, a microbially driven Fe shuttle for the largest BIFs on Earth. Detailed sampling at various scales shows that the proportions of hydrothermal and continental Fe sources were invariant over periods of 10 â°â10 ³ y, indicating that there was no seasonal control, although Fe sources varied on longer timescales of 10 âµâ10 ⶠy, suggesting a control by marine basin circulation. These results show that Fe sources and pathways for BIFs reflect the interplay between abiologic (hydrothermal) and biologic processes, where the latter reflects DIR that operated on a basin-wide scale in the Archean.
Mass-dependent K isotopic fractionations can be used to trace cosmochemical, geological, and biological processes such as evaporation/condensation, core formation, magmatic processes, weathering, and ...cellular metabolism. However, the application of stable K isotopes has been limited by major isobaric interferences from Ar, common on conventional multi-collector inductively-coupled-plasma mass-spectrometer (MC-ICP-MS), particularly for the low-K samples. Here, we present a set of high-precision K isotopic data acquired on terrestrial rocks, seawater, as well as a lunar meteorite using the recently released Nu Sapphire™ MC-ICP-MS that utilizes a collision cell to minimize Ar based interferences while maintaining remarkably high K sensitivity (≈ 2000 V/ppm). The influence of several parameters on the precision and accuracy of the K isotopic data has been evaluated, including total K concentration, K intensity mismatch between sample and standard, HNO3 molarity mismatch between sample and standard, and the presence of matrix elements. We found that the Nu Sapphire™ can be used to acquire precise and accurate data using as little as 125 ng of K, which represents an improvement by a factor 10 compared to what has been done on previous instruments. We present data for 23 previously analyzed samples; these data are highly consistent with literature values. On the other hand, accurate measurements are conditioned 1) to the close matching of sample and standard K intensities (a 1% mismatch creates a 0.02‰ offset on the 41K/39K ratio), and 2) to the absence of Ca (a Ca/K ratio of 1% creates a 0.069‰ offset on the 41K/39K ratio). In addition, Rb/K, Na/K, Ti/K and Cr/K ratio should also be maintained under 2.5% to avoid isotopic offset.
We confirm the existence of significant mass-dependent K isotopic variations in terrestrial samples and that lunar rocks are isotopically heavier than terrestrial rocks. The incomparable sensitivity offered by the Nu Sapphire opens the possibility for high-precision K isotopic measurements across a wide range of samples for diverse applications.
Display omitted
Interactions between aqueous Zn and mineral surfaces can lead to notable Zn isotope fractionation that affects Zn source fingerprinting, which needs an atomic-level understanding. In this study, we ...demonstrate that Zn isotope fractionation (Δ66Znsorbed‑aqueous) during Zn sorption onto γ-Al2O3 depends on both pH and Zn concentration and ultimately correlates to surface coverage (Γ). At pH values of 6.0–6.5 and/or Zn concentrations of 0.1–0.2 mM, where Γ < 0.8 μmol m–2, Δ66Znsorbed‑solution is 0.47 ± 0.03‰, whereas Δ66Znsorbed‑aqueous decreases to 0.02 ± 0.07‰ at pH values of 7.0–8.0 and Zn concentrations of 0.4–0.8 mM, with a high Γ ranging from 1.5 to 3.2 μmol m–2. Using extended X-ray absorption fine structure (EXAFS) spectroscopy, we elucidated that a Zn–Al layered double hydroxide (LDH) with a Zn–O bond length of 2.06 Å forms at high surface coverage (1.5 < Γ < 3.2 μmol m–2). In contrast, at low surface coverage (Γ < 0.8 μmol m–2), the sorbed Zn occurs as a tetrahedrally coordinated inner-sphere surface complex with an average Zn–O interatomic distance of 1.98 Å. Such contrasts lead to an atomic level understanding of the strong links between isotope fractionation, local bonding structures (i.e., coordination and bond distances), and solution chemistry, which is crucial for more effective applications of stable metal isotopes as environmental tracers.
Crystallization from an amorphous precursor is an important pathway of carbonate precipitation in nature. However, the mechanistic details of the transformation from an amorphous phase to a ...crystalline phase of carbonates remain a topic of intense debate. Two competing mechanisms, including solid-state transition and coupled dissolution-reprecipitation, have been proposed to explain this transformation process. Magnesium is a common element in carbonate crystal lattices and its isotopes may provide unique insights into this problem. In this study, we investigated the transformation of the amorphous carbonate (AC) precursor for norsethite BaMg(CO3)2, a dolomite analogue mineral, by in situ XRD analysis and isotope exchange experiments using a 25Mg enriched tracer coupled with high precision isotope analyses of δ26Mg and δ25Mg values for aqueous and solid phases. In situ XRD experiments revealed that the AC can transformed to crystalline norsethite at various temperatures (25 °C, 50 °C and 70 °C) and no intermediate mineral formed during the AC transformation process. 25Mg tracers indicated that near-complete Mg isotope exchange occurred in all exchange experiments during AC transformation. More importantly, after the AC transformation, the system showed surprising apparent non-mass dependent fractionation relationship, that the δ25Mg value of solid phase became greater than that of aqueous solution from a lower value, producing positive Δ25Mgsolid-aq fractionation, whereas the Δ26Mgsolid-aq fractionation remained negative. We numerically modeled the behavior of Mg isotopes (in both δ26Mg and δ25Mg) for the experimental system according to the two competing mechanisms of AC transformation. The modeling results suggest that the apparent non-mass dependent isotope behavior can only be explained by the coupled dissolution-reprecipitation process. Therefore, this study does not support the solid-state transition mechanism for AC transformation. Further, this study rigorously proves that norsethite can form by precipitation from aqueous solution without replacement, and implies that Mg2+ in aqueous solutions can be efficiently dehydrated and incorporated into a well ordered dolomite-group mineral (norsethite) under abiotic, low temperature conditions, thus providing new insights for understanding dolomite precipitation in nature.
In this study, we used an improved “diffusion cell” method to precisely determine the diffusion-driven kinetic isotope fractionation factors of the Li, K, Rb, Mg, Ca, Sr, and Ba cations in aqueous ...solutions under room temperature. The obtained isotope fractionation factors (±2σ errors) are, α7/6Li = 0.996139 ± 0.000140, α41/39K = 0.998572 ± 0.000072, α87/85Rb = 0.999333 ± 0.000020, α26/24Mg = 0.999877 ± 0.000010, α44/42Ca = 0.999704 ± 0.000010, α88/86Sr = 0.999781 ± 0.000014, α138/135Ba = 0.999716 ± 0.000018. The results show that the charge of the cation and the ion-water bond length for the aquo ions are the two predominant factors affecting the mass dependence of isotope fractionation (β factor) during cation diffusion in aqueous solutions. Cations with higher charge numbers and shorter ion-water bond lengths exhibit less kinetic isotope fractionation during diffusion. Therefore, the isotope separation effect during diffusion (or β factor) in fluids is fundamentally controlled by the intensity of ion-water interaction. Weaker ion-water interaction (e.g., lower charge number, longer ion-water bond length) leads to less prominent hydrodynamic behavior for diffusing ions at the molecular level, thus more significant isotope fractionation in bulk solutions, and vice versa. Ions of larger radius would show stronger mass dependence of isotope fractionation (β factor), which can cancel the effect of decreasing relative isotope mass difference for heavier elements, thus kinetic isotope fractionation during diffusion in aqueous solutions remains prominent even for heavy elements such as Rb, Sr, and Ba. The diffusion-driven kinetic isotope fractionation factors measured in this study could provide a useful basis for interpreting specific natural isotopic variability of alkaline and alkaline-earth elements in supergene environments where chemical diffusion takes place.
Improvements in mass spectrometry have made it possible to identify naturally occurring K isotope (39K/41K) variability in terrestrial samples that can be used in a variety of geological and ...biological applications that involve cycling of K such as clay or evaporite formation. However, our ability to interpret K isotope variability is limited by a poor understanding of how K isotopes are fractionated at low temperatures. In this study, we conducted recrystallization experiments of eight K-salts in order to measure the K isotope fractionation factor between the salt and the saturated K solution (Δ41Kmin-sol). Measured Δ41Kmin-sol are +0.50‰ for K2CO3·1.5H2O, +0.32‰ for K2SO4, +0.23‰ for KHCO3, +0.06‰ for K2C2O4·H2O, +0.02‰ for KCl, −0.03‰ for K2CrO4, −0.15‰ for KBr, and −0.52‰ for KI. Overall the Δ41Kmin-sol decreases with increasing r for K in crystals, where r is the average distance between a K atom and its neighboring atoms of negative charge. Salts with monovalent anions and salts with divalent anion complexes define different linear trends with distinct slopes on a plot of Δ41Kmin-sol - r. We applied ab initio lattice dynamics and empirical crystal-chemistry models to calculation of K isotope fractionation factors between K salts; both methods showed that the calculated inter-mineral K isotope fractionation factors (Δ41Kmin-KCl) are highly consistent with experimentally derived Δ41Kmin-KCl under the assumption of consistent β factors for different saturated K solutions. Formulations for the crystal-chemistry model further indicate that both anion charge and bond length r are the principle controlling factors for K isotope fractionation, and the K isotope fractionation factors correlate with r following a 1/r3 relationship. Our experiment and theoretical study confirms the existence of significant equilibrium K isotope fractionation at ambient conditions, and the K isotope fractionation factors for halides and sulfate obtained in this study provide a basis for future K isotope studies on evaporites.
High precision potassium isotope ratio measurements were made using a collision-cell equipped single focusing Multi-Collector Inductively Coupled Plasma Mass Spectrometer (MC-ICP-MS). Interferences ...on 41 K from 40 ArH + were largely suppressed through collision with He gas atoms, and reaction with H 2 or D 2 gas molecules in the collision cell under optimum collision gas flow conditions. Using H 2 or D 2 as the collision gas, we distinguish charged argon–deuterium molecules (ArD + ) generated in the collision cell from argon hydride (ArH + ) generated in the plasma or in the interface region (referred to as “plasma-related AH + ” hereafter), and demonstrate, for the first time, that both plasma-related and collision cell-generated ArH + are important sources of ArH + that interfere with 41 K + in collision-cell ICP-MS instruments that use H 2 as a collision gas. The use of D 2 instead of H 2 as a reactive gas in the collision cell resulted in better overall performance in K isotope ratio measurements. By combining these mass spectrometry methods with chemical purification of K by ion exchange chromatography, we achieved an internal precision of <±0.07‰ (2 standard error) and an external reproducibility of <±0.21‰ (2 standard deviation, or 95% confidence) in the 41 K/ 39 K ratio measurement for geological and biological samples. With the improved precision, it is possible to distinguish a ∼1.3‰ variation in K isotope compositions ( 41 K/ 39 K ratios) among seawater, igneous rocks, and biological samples. The K isotope system is likely to be beneficial in providing a better understanding of potassium cycling during continental weathering and the uptake of nutrients by plants.
PDF
