Search

Moringa oleifera leaves (MOL) are native to India and have high biological activities. To better understand the basic pharmacodynamic materials, the chemical components in MOL and their pharmacokinetic properties were studied and quantitated using UPLC-Q-Exactive Orbitrap-MS. Forty-two compounds were identified, including phenolic acids and their derivatives, flavonoids, isothiocyanates, nucleosides, alkaloids, and other compounds. Two phenolic acids and six flavonoids were studied for their pharmacokinetic properties using UHPLC-MS/MS. Precision, accuracy, stability, matrix effects, and extraction recovery were verified. All substances that were measured reached their maximum within 0.5 h. Vicenin-2 had a high peak concentration and bioavailability. Kaempferol-3-O-rutinoside had a longer biological half-life than other components. The results from this study provide the data basis for subsequent comprehensive qualitative evaluation and potential MOL use in clinical applications.

Regional surface deformation resulting from the development and utilization of underground space resources poses a significant threat to the safety of urban areas, and the combination of Synthetic Aperture Radar and Gravity Recovery and Climate Experiment (GRACE) satellite data has become a new means to study the impact of underground space evolution on surface deformation. We combine the Interferometric Synthetic Aperture Radar (InSAR) technology and gravity satellite data to extract information on regional surface deformation and groundwater storage changes in Shanxi Province, to explore the patterns of their temporal and spatial variations, to discover their links with seasonal climate change, to re-conceptualize the laws of the regional water cycle, and to quantify the contribution of multiple fields to the evolution of the surface. Furthermore, we propose a novel multi-source neural network prediction model (LSTM/BP) based on signal decomposition (VMD) and algorithm optimization to handle the complex time series characteristics of groundwater storage. Our findings reveal that groundwater storage in Shanxi Province has been consistently declining, with a monthly deficit rate of approximately 1.05 mm. Additionally, there is a notable spatial variation in the annual rate of change, ranging from −21 to 4 mm/year from north to south. Furthermore, we observe a close relationship between inter-annual and seasonal groundwater storage changes and local rainfall patterns, and we find that regional surface deformation is influenced by these groundwater storage changes. The new prediction model outperforms other models, with a root mean square error of 1.56 mm and a correlation coefficient of more than 0.98 on the test set. The model improves the prediction accuracy of the groundwater reserves in the basin, and it can be used to provide a reference for the comprehensive management of the groundwater in Shanxi Province, the rational development of mineral resources, and other major national needs.

In order to overcome the dilemma of insufficient effective sample number for subsurface microcrack depth in the lapping of brittle materials with fixed abrasives and achieve accurate prediction, a co-training SVR was used to construct the prediction model. The effects of different labeled training set partitioning methods on the mean square error of the test set were compared. Then the predictive performance of supervised learning PSO-SVR model was compared with that of the model. Finally, brittle materials such as microcrystalline glass and calcium fluoride, which were not included in the labeled training set, were taken as processing objects for lapping and angular polishing experiments to examine crack depth values. The examined subsurface microcrack depths of four groups were compared with the predicted values of the co-training SVR model. The results show that the co-training SVR model under the separate partitioning method has a smaller mean square error. Compared with the PSO-SVR model, the mean square error and the mean absolute percentage error of the co-training SVR model are reduced by 9% and 17%, respectively. The prediction error of the model for the four groups of verification experiments is between 1.2% and 13.8%. The above results show that the co-training SVR model can predict the subsurface microcrack depth accurately when lapping brittle materials with fixed abrasives.

Abstract Joshimath has received much attention for its massive ground subsidence at the beginning of the year. Rapid urbanization and its unique geographical location may have been one of the factors contributing to the occurrence of this geological disaster. In high mountain valley areas, the complex occurrence mechanism and diverse disaster patterns of geological hazards highlight the inadequacy of manual monitoring. To address this problem, the inversion of deformation of the Joshimath surface in multiple directions can be achieved by multidimensional InSAR techniques. Therefore, in this paper, the multidimensional SBAS-InSAR technique was used to process the lift-track Sentinel-1 data from 2020 to 2023 to obtain the two-dimensional vertical and horizontal deformation rates and time series characteristics of the Joshimath ground surface. To discover the causes of deformation and its correlation with anthropogenic activities and natural disasters by analyzing the spatial and temporal evolution of surface deformation. The results show that the area with the largest cumulative deformation is located in the northeastern part of the town, with a maximum cumulative subsidence of 271.2 mm and a cumulative horizontal movement of 336.5 mm. The spatial distribution of surface deformation is based on the lower part of the hill and develops towards the upper part of the hill, showing a trend of expansion from the bottom to the top. The temporal evolution is divided into two phases: gentle to rapid, and it is tentatively concluded that the decisive factor that caused the significant change in the rate of surface deformation and the early onset of the geological subsidence hazard was triggered by the 4.7 magnitude earthquake that struck near the town on 11 September 2021.

El Niño-Southern Oscillation (ENSO), a cyclic climate phenomenon spanning interannual and decadal timescales, exerts substantial impacts on the global weather patterns and ecosystems. Recently, deep learning has brought considerable advances in the accurate prediction of ENSO occurrence. However, the current models are insufficient to characterize the evolutionary behavior of the ENSO, particularly lacking comprehensive modeling of local-range and longrange spatiotemporal interdependencies, and the incorporation of calendar monthly and seasonal properties. To make up this gap, we propose a Two-Stage SpatioTemporal (TSST) autoregressive model that couples the meteorological factor prediction with ENSO indicator prediction. The first stage predicts the meteorological time series by leveraging self-attention ConvLSTM network which captures both the local and the global spatial-temporal dependencies. The temporal embeddings of calendar months and seasonal information are further incorporated to preserves repeatedly-occurring-yet-hidden patterns in meteorological series. The second stage uses multiple layers to extract higher level of features from predicted meteorological factors progressively to generate ENSO indicators. The results demonstrate that our model outperforms the state-of-the-art ENSO prediction models, effectively predicting ENSO up to 24 months and mitigating the spring predictability barrier.

An important question of earthquake science is to what extent fluids such as water play an important role in modulating seismicity. While many models of earthquake rupture assume that fluids are critical for dynamic weakening during slip and evidence for fluids is well documented for shallow injection‐induced or hydrothermally induced earthquakes, there has been limited conclusive evidence for the role of fluids for tectonic earthquakes in the middle‐to‐lower crust. Here, we provide evidence for fluid migration during the 2016 Meinong, Taiwan, aftershock sequence, occurring at 10–20 km depth within a classic fold‐and‐thrust belt. We find high Vp/Vs ratios, characteristic of highly fluid saturated regions, in the Meinong aftershock region and that the Vp/Vs ratios in the central aftershock region change with time during the aftershock sequence. The central aftershock sequence distinguishes itself from other aftershocks by having a swarm‐like magnitude distribution and aftershock decay rate, as well as a slower migration rate that may be related to fluid diffusion. The estimated permeability (~3.8 × 10−15 m2) and temporal changes in Vp/Vs suggest that moderate earthquakes may be able to strongly affect permeabilities in the midcrust. The results also suggest that fluid processes play a critical role in regulating seismicity in a classic continental collision tectonic setting and may also have a role in modifying earthquake hazards more generally. Plain Language Summary: A long‐standing question is how fluids like water influence earthquakes. While the effect of fluids on earthquake rupture is widely observed for shallow injection‐induced or hydrothermally induced earthquakes, we know relatively less about their effect on deep earthquakes. Here, we provide evidence for fluid movement during the 2016 Meinong aftershock sequence in southwestern Taiwan. The analysis shows that seismic waves traveling through the aftershock region change their speed during the aftershock sequence, which is strongly suggestive of fluid movement. An estimate of the speed of fluid migration also suggests that the midcrust of southwestern Taiwan can easily transport fluids. These results suggest that fluids may generally play an important role for deep crustal earthquakes and affect earthquake hazards. Key Points: Temporal Vp/Vs changes and aftershock migration suggest that fluid migration occurred during the 2016 Meinong, Taiwan, earthquake sequenceSpatial correlation analysis suggests that seismic hazards may be higher around the fringes rather than at the center of fluid‐rich regionsMidcrustal permeability may vary temporally due to deep crustal earthquakes [ABSTRACT FROM AUTHOR]

Landslides are one major kind of natural disasters and geomorphological processes on Earth's surface. Accurate geodetic observations are crucial for understanding morphological changes, providing a quantitative basis of further research in surface process and hazard management. In recent years, the development of UAVs and SfM technology enhance research to build high quality digital surface models of landforms with low budget and efficiency. In areas of extreme topography where landslides occur on steep slopes, however, it is required to specifically design the UAV-SfM workflow to keep the data quality. This study aims to use UAS-SfM workflow to develop a low-cost, efficient methodology to detect detailed morphological change of landslide morphology in extreme topography. The study focuses on examining results of different flight design and GCPs distribution geometry, which are important components in the workflow. In addition, we applied a mathematical model to compare point clouds to calculate volumetric change of the landslide with reduced distortion. [ABSTRACT FROM AUTHOR]

Large dip‐slip earthquakes have a major contribution to mountain building while earthquake‐induced landslides lower mountains simultaneously. The amount of the coseismic uplift and landslides may dominate long‐term mountain evolution. However, how earthquakes contribute to mountain evolution through coseismic uplift and landslides is less constrained in real cases. We present the regional coseismic uplift of the 1999 Mw7.6 Chi‐Chi earthquake by using synthetic aperture radar (SAR) images and GPS. The coseismic uplift pattern is consistent with field observations showing increasing movement to the north with ~8 m of uplift toward the northern end. We estimated uplifted rock volume of 2.60 ± 1.09 km3, which is five times greater than the coseismic landslide volume. Intense erosion of the Taiwan orogen may erode elevated rocks rapidly, but the uplift and landslide distributions do not match and correlate more inversely, suggesting the frontal orogenic topography should be increased rather than annulled over earthquake cycles. Plain Language Summary: Earthquakes can raise mountains but they can cause landslides to lower the mountains at the same time. For large earthquakes, mountains could reduce the size due to more landslides than uplift. It is important to analyze earthquakes occurred within mountain ranges to examine how much volume of rocks is elevated and how much volume of rocks is trampled down. Because complete observations of uplift and landslides for large earthquakes are rare, we used geodetic methods to estimate the volume of the elevated rocks for one of the largest earthquakes in mountain ranges in the world, the Chi‐Chi, Taiwan, earthquake in 1999. The volume of elevated rocks is much larger than the landslide volume, and the uplift area is close to the frontal mountains and the landslide areas are distributed in the deeper mountains. If this finding holds for other mountain ranges in similar settings, this means that large earthquakes should raise mountains, especially in the frontal part of the mountains. Key Points: We estimate the regional pattern of the coseismic uplift of the Chi‐Chi earthquakeIncreased rock volume is significantly greater than coseismic landslide volume for the Chi‐Chi earthquakeThe distributions of coseismic uplift and landslides suggest differential topographic increase at frontal orogen [ABSTRACT FROM AUTHOR]

Gallium nitride (GaN) ultraviolet metal-semiconductor-metal photodetectors (PDs) grown on Si substrates were demonstrated. The dark current of PDs fabricated on Si substrates was substantially smaller in magnitude compared to identical devices prepared on sapphire substrates. With an incident wavelength of 359 nm, the maximum responsivities of the n--GaN MSM photodetectors with TiW and Ni/Au contact electrodes were 0.187 and 0.0792 A/W, corresponding to quantum efficiencies of 64.7% and 27.4%, respectively. For a given bandwidth of 1 kHz and a given bias of 5 V, the corresponding noise equivalent powers of our n--GaN MSM photodetectors with TiW and Ni/Au electrodes were 1.525×10-12 and 5.119×10-12 W, respectively. Consequently, the values of detectivity (D*) determined for devices with TiW and Ni/Au electrodes were then calculated to be 1.313×1012 and 3.914×1011 cm Hz0.5 W-1, respectively. [ABSTRACT FROM AUTHOR]

Aromatic hydrocarbon molecules with π-conjugated structure have great potential for the search of exotic states such as high temperature superconductivity and novel quantum magnetism. In this work, we found that high temperature weak ferromagnetism can be achieved by intercalating rubidium into the shortest poly(para-phenylene) molecule—biphenyl. Both dc and ac magnetic susceptibility measurements showed that the synthesized material exhibits a typical antiferromagnetic transition at 48.5 K, accompanying a ferromagnetic character in the magnetically ordered region. Combining theoretical calculations and Raman spectroscopic studies, it was found that the mole ratio between rubidium and biphenyl is 1:1, and the molecular magnetic moments are formed by transferring the Rb-5s electrons to the C-2p orbitals. The weak ferromagnetism is produced by intralayer spin-canted antiferromagnetic and interlayer ferromagnetic spin couplings. Our finding enriches the physicochemical functionality of biphenyl and opens a window for the search of π-electron organic magnets in poly(para-phenylene) molecules.

We propose an efficient way of axial magnetic fields generation in a nonrelativistic laser intensity regime by using a twisted light carrying orbital angular momentum (OAM) to stimulate two-plasmon decay (TPD) in a plasma. The growth of TPD driven by an OAM light in a Laguerre-Gauss (LG) mode is investigated through three-dimensional fluid simulations and theory. A theory based on the assumption that the electron plasma waves (EPWs) are locally driven by a number of local plane-wave lasers predicts the maximum growth rate proportional to the peak amplitude of the pump laser field and is verified by the simulations. The OAM conservation during its transportation from the laser to the TPD daughter EPWs is shown by both the theory and the simulations. The theory predicts generation of ≈40 T axial magnetic fields through the OAM absorption via TPD, which has perspective applications in the field of high energy density physics.

• It is conducive to Bull Camphor tree cultivation and industry development. • The polarity of the solvent affects the content of active substances in CKHLE. • CKHLE showed antioxidant properties ascribed to the abundance of TPC and TFC. • CKHLE with antioxidant capacity has certain research value for developing functional foods. • CKHLE is a potential source of bacteriostatic and NSAIDs development. Bull Camphor tree (Cinnamomum kanehirae Hayata; CKH) (Lauraceae) is an endemic species in Taiwan. Its trunk is the main host of Taieanofugus camphoratus , traditional medical fungi. There are few research involving the functional properties and antibacterial activity of Cinnamomum kanehirae Hayata leaves (CKHL), although its abundant leaves. The purpose of the study was to investigate the effects of the different concentrations of ethanol solvents on the chemical compositions and biological activities of the CKHL extract (CKHLE). Furthermore, the antioxidant, antibacterial activity, anti-inflammatory, and anticancer ability of the extracts were tested. The results showed that the 50% ethanol CKHLE indicated the highest total polyphenols (TPC) and total flavonoids (TFC) (16.98 ± 0.18 mg GAE/g and 1.90 ± 0.04 mg QE/g, respectively) among the CKHLEs. The 50% ethanol CKHLE also indicated the best antioxidant performance in DPPH and ABTS+ free radical scavenging, reducing power, and ferric reducing antioxidant power (FRAP). The antioxidant performance of the four CKHLEs were exhibited in a dose-dependent manner. As well as, the 95% ethanol extract CKHLE indicated moderate antibacterial activity against Candida albicans , Escherichia coli, and Bacillus cereus. In terms of anti-inflammatory ability, all CKHLEs showed the best COX-2 inhibition at the concentration of 10 mg/mL. The 80% ethanol CKHLE reduced by 50.05% of NO production in Raw 264.7 cells compared to the control. The 80% and 95% CKHLEs also exhibited decreases in cell viability of colorectal cancer cells (C2BBe1) up to 94.64% and 93.99%, respectively, at the CKHLE's concentration of 1000 μg/mL. These results demonstrated the different solvents affected the chemical compositions and biological activities (antibacterial, antioxidant, anti-inflammatory and anticancer activities) of CKHLE. Furthermore, the CKHLE are a potential source of healthy foods, bacteriostatic and non-steroidal anti-inflammatory drugs (NSAIDs) development. [ABSTRACT FROM AUTHOR]

We present particle-in-cell (PIC) simulations of laser plasma instabilities (LPIs) with a laser pulse duration of a few picoseconds. The simulation parameters are appropriate to the planar-target LPI experimental conditions on SG-II. In this regime, the plasmas are characterized by a long electron density scale length and a large electron density range. It is found that when the incident laser intensity is well above its backward stimulated Raman scattering (backward SRS, BSRS) threshold, the backscattered light via the primary BSRS is intense enough to excite secondary SRS (Re-SRS) in the region below one-ninth of the critical density of the incident laser. The daughter light wave via the secondary BSRS (Re-BSRS) is amplified as it propagates toward the higher-density region in the bath of broadband light generated through the primary BSRS process. A higher intensity of the incident laser not only increases the amplitude of the BSRS light but also increases the convective amplification lengths of the Re-BSRS modes by broadening the spectrum of the BSRS light. Convective amplification of Re-BSRS causes pump depletion of the primary BSRS light and may lead to an underestimate of the primary BSRS level in SP-LPI experiments. A significant fraction of the generation of energetic electrons is strongly correlated with the Re-BSRS modes and should be considered as a significant energy loss.

This paper studies a battery energy storage system based on the hexagonal modular multilevel direct ac/ac converter with focus on a control method for state-of-charge (SOC) balancing of the battery units. First, the system structure and the operating principle of the hexagonal multilevel converter, including the branch voltage and the power, are analyzed and simulated, respectively. Then, the mathematical model of the energy storage submodule consisting of the battery energy storage unit and H-bridge submodule cell is developed in PSCAD/EMTDC software. After that, a SOC balancing control strategy is proposed, including the branch SOC balancing between the converter's six branches and the individual SOC balancing between the 14 cascaded converter cells in each branch, which is realized by controlling currents in branch modules. Currents in the branches are controlled by the internal model principle. Finally, the effectiveness of the control strategy is verified in simulation.

UV metal-semiconductor-metal (MSM) photodetectors (PDs) based on the AIGaN/GaN high-electron-mobility transistor (HEMT) structure with the low-temperature (LT) AIGaN intermediate layer atop were fabricated. A much lower dark current subsequently obtained was in fact benefited by the insertion of the LT AIGaN intermediate layer. In addition, the foregoing structure also rendered PDs with better gate controllability. For the MSM PD structure grown on the LT AIGaN intermediate layer, the resultant responsivity at 360 nm varied from 0.11 to 0.12 A/W when the device was biased from 2 to 5 V while the UV/visible rejection was estimated to be around 10³. With a 5 V applied bias, the corresponding noise equivalent power and normalized detectivity (D*) determined were 2.65 X 10-10 W and 1.74 X 109 cm Hz0.5 W-1, respectively. [ABSTRACT FROM AUTHOR]

We report the growth of InN by metalorganic chemical vapor deposition on Si(111) substrates. It was found that the sharpest InN(002) x-ray diffraction peak could be achieved from the sample prepared on a complex buffer layer that consists of a low-temperature AlN, a graded AlxGa1-xN (x = 1 → 0), and a high-temperature GaN. The resultant mobility of 275 cm²/V s thus obtained was 75% larger than that of the InN prepared on a single LT-AlN buffer layer only. [ABSTRACT FROM AUTHOR]

Dilute-nitride materials have attracted much attention due to their capability of operating in the wavelength range of optical communication. However, their optical properties degrade with the nitrogen incorporation into the host material such as InGaAs or GaAs, which can be recovered slightly by performing thermal treatment. More recently, the surfactant effect of Sb was verified by molecular beam epitaxy grown samples. Adding Sb into dilute-nitride materials can help to maintain the luminescence efficiency while increasing the emission wavelength toward 1.55 μm. But its effect on the metal organic vapor phase epitaxy grown samples is not very clear. In this article, we performed a series of experiments on the InGaAsN(Sb) quantum wells to clarify the role of Sb. The photoluminescence (PL) intensities of InGaAsN:Sb were higher than those of the undoped samples and the extent of blueshift after annealing was slighter than that of the InGaAsN quantum wells. However, the PL intensities were still low and thus we tried another material (InGaAs:Sb) to achieve the 1.3 μm emission. The temperature dependent PL measurements were also carried out to investigate the optical properties of InGaAs:Sb quantum wells. [ABSTRACT FROM AUTHOR]

Epidermolysis bullosa (ER) pruriginosa is a subtype of dominant dystrophic ER (DDER), characterized by severe pruritus and blistering localized to the extensor surface of the extremities. EB pruriginosa exhibits extensive clinical heterogeneity with variable expression and delayed age of onset. Mutations in the COL7A1 gene, especially in glycine residues within (Gly-X-Y repeats, have been shown to cause this form of DDEB. Here, we report a novel COL7A1 mutation in a Taiwanese pedigree with ER pruriginosa. Using PCR and direct sequence analysis we have identified a G→ T transversion at nucleotide 7097 in exon 92 of COL7A1, converting a glycine residue to valine (G2366V). The mutation resides within a consecutive, uninterrupted stretch of 17 Gly-X-Y residues in the triple-helical domain of type VII collagen. Interestingly, an affected member of this family also displayed elevated IgE levels, previously reported in some patients with this disorder. Our finding further implicates COL7A1 mutation in the pathogenesis of ER pruriginosa and underscores the heterogeneous clinical symptoms of glycine mutations in DDEB. [ABSTRACT FROM AUTHOR]

The effort-reward imbalance (ERI) model is a theoretical model of a psychosocial work environment with adverse effects on health and well-being that focuses on a mismatch between high efforts spent and low rewards received at work. This study aimed to develop and psychometrically test an effort-reward imbalance questionnaire for teachers (Teacher ERIQ) based on the ERI model. The structure validity, reliability, and criterion validity of the new questionnaire’s scores were evaluated in a sample of 475 Chinese teachers. The results of exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) showed that a structure of four factors of effort (workload, emotional demands, student-related issues, and social responsibility) and two factors of reward (emotional reward and material reward) in accordance with the ERI model had significant factor loadings and acceptable model fit. The Cronbach’s Alpha coefficients of all dimensions’ scores showed that the questionnaire scores had good reliability. Criterion validity was indicated by significant correlation coefficients of scores of most dimensions along with teachers’ self-reported job burnout and non-reciprocal social relations, as well as the ANOVA results showing that the differences of the scores of the two criterion scales in different ERI ratio levels were significant. The results also showed that teacher’s ERI level varied with demographic variables such as age, gender and school type. The Teacher ERIQ is a valid and reliable new measurement for assessing teachers’ psychosocial work characteristics. It can be an important tool to provide new explanations of stress-related health risks among teachers and to guide the development of preventive measurements.

Rhesus monkeys (Macaca mulatta) and the simian immunodeficiency virus (SIV) were used as an animal model system to evaluate longitudinally the effects of opioid dependence on the development of AIDS. Results have shown that in addition to weakening the host's T cell and PMN functions, chronic opioid treatment of SIVmac239-infected animals caused (a) an increased virus replication rate, (b) an increased rate of viral mutation, (c) a nascent humoral (antibody) response against mutated autologous strains of virus, (d) an alteration of CD8 + cell-mediated immunity toward the mutant virus, (e) an increased tolerance of AZT among the infectious virus and (f) a shorter life span for the infected animals. These results suggest that chronic administration of opioids alters general fundamental aspects of the AIDS viremia. [ABSTRACT FROM AUTHOR]

InGaN-GaN multiple-quantum-well metal-semiconductor-metal photodiodes (PDs) with in situ grown 40-nm-thick unactivated semi-insulating Mg-doped GaN cap layer were successfully fabricated. The dark leakage current of this PD was comparably much smaller than that of conventional PD without the semi-insulating layer, because of a thicker and higher potential barrier of semi-insulating cap layer, and also a smaller number of surface states involved. For the PDs with the semi-insulating Mg-doped GaN cap layers, the responsivity at 380nm was 0.372A/W when biasing at 5 V. In short, incorporating a semi-insulating Mg-doped GaN cap layer into the PDs beneficially leads to the suppression of dark current and a corresponding improvement in the ultraviolet-to-visible rejection ratio [ABSTRACT FROM PUBLISHER]

Fabrication of metal–semiconductor–metal near-infrared photodetectors with 0.4 µm-thick GaInNAs absorption layer was demonstrated. Better crystal quality and fewer dislocations were obtained from samples with lower nitrogen content based on the results of photoluminescence and high-resolution X-ray diffraction. The absorption edge located at 1.2 µm under 4 V bias was realised owing to the nitrogen incorporation effect, and the responsivity of GaInNAs MSM photodetectors higher than 60 mA/w was also successfully achieved when compared to other conventional InGaAs detectors. The devices, hereby demonstrated believably, should have potential applications in fibre optics communications. [ABSTRACT FROM AUTHOR]

Nitride-based light-emitting diodes (LEDs) with n--GaN current spreading layers were proposed and fabricated. With a 0.1-μm-thick n--GaN current spreading layer, it was found that the output power could be enhanced by 35% without increasing the operation voltage of the LEDs at 20 mA. In addition, implementing the n--GaN current spreading layer also significantly improved the electrostatic discharge characteristics of nitride-based LEDs. [ABSTRACT FROM AUTHOR]

The complex strain hardening behaviors of dual phase (DP) steel are subjected to the heterogeneous microstructures. The current work aims to predict the strain hardening behaviors of ferrite-martensite DP steel, focusing on the effects of heterogeneous microstructure on mechanical properties. The flow stress of material was calculated based on the dislocation-based work-hardening model with considering the multi-boundaries hardening. The ferrite-martensite phase boundary percent and grain shape factor were selected as the heterogeneous feature parameters, which were introduced into the new proposed model. The theoretical calculated stress-strain responses were verified with experimental results using the tensile test. The model with the boundary strengthening consideration has more accurate results. The parameter effects of ferrite-ferrite boundary (FFB) spacing, ferrite-martensite boundary (FMB) percent, and grain shape factor on the flow stress-strain curve were researched.

The similar crystal structures of martensite (BCT) and ferrite (BCC) cause difficulty in distinguishing the grain orientations of individual phases in dual-phase (DP) steels. A dislocation-based multiphase mixed hardening model is presented, considering both ferrite and martensite strain partitioning, to describe the texture-dependent mechanical behavior of DP steels more precisely. This model is based on the ideals that (i) the volume fractions of the constituent phases and the corresponding strain partitioning function are obtained through in situ tensile experimentation, and (ii) the grain orientations of ferrite and martensite are assumed to be in accordance with the overall texture. We applied the model to calculate the macroscopic and microscopic mechanical behavior of DP800 steel using a crystal plasticity finite element (CPFE) code. The results show that the calculated stress-strain response and textural evolution are in good agreement with the experimental results. The dislocation evolution indicates that the rapid hardening of ferrite induces a high hardening rate for DP steels early in plastic deformation. In addition, for the grains corresponding to the texture center orientations of DP800, the activity and dislocation density evolutions of the slip systems are studied.