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In recent research works on coverless text information hiding, there are two main problems to be solved: low hiding success rate and small hiding capacity caused by the small amount of redundant information in the cover text. In order to overcome these problems, a method of coverless information hiding based on the combination of Chinese character components is proposed. This method is based on the traditional “location tag [Formula: see text] keywords” mode for coverless information hiding, but with an improved design to extend the scope of available keywords for data hiding beyond the original cover texts. In our proposed method, each Chinese character in the keyword is split into two components: radicals and independent Chinese character, which are collected and will be recombined in pairs to generate the new Chinese characters. This method increases the hiding success rate and hiding capacity by generating Chinese characters that do not exist in the original cover text. The experimental result shows that the proposed method can utilize less size of carrier text database for efficient information hiding. When the size of carrier text database is reduced to 198[Formula: see text]MB, the highest hidden capacity and hidden success that can be achieved are 13.45 and 0.99, respectively.

MMTNS were introduced into carboxymethyl cellulose-chitosan system to synthesize porous hydrogel adsorbent with stable structure and high dye handling capacity. Al-OH on edge of MMTNS formed hydrogen-bond (-OH···+NH3-) with -NH2 on CS, CS then cooperated with CMC via amidation and chains interleaving, forming three-dimensional hydrogel. Morphology characterization revealed that hydrogel possessed microporous open-framework structure, facilitating free entrance of macromolecular MB dye to react with internal reaction sites in hydrogel. Factor tests indicated that high removal (97%) of MB was achieved via 0.2 g/L hydrogel within 360 min even after 5 adsorption-regeneration cycles. Adsorption process followed Pseudo-first-order, Pseudo-second-order kinetic model and Sips isotherm model, owing to both monolayer physical and chemical adsorption behavior of MB molecules onto homogeneous surface of hydrogel. Adsorption mechanism was attributed to ion-exchange, groups combination of carboxyl and hydroxyl, and Si active sites reaction. Such hydrogel realized promotion of polysaccharide polymers in materials design and wastewater treatment.

The grain refinement resulting from the addition of yttrium (Y) (1, 3 pct, and 9 wt pct) and zirconium (Zr) (0.1, 0.2, and 0.5 wt pct) to magnesium (Mg) under a wide range of cooling rates (0.8 to 160 K/s) has been investigated. This study quantifies the effect of Y and Zr on the grain size (dgs) of Mg-Y base alloys followed by examination of the effect of cooling rate on these alloys. The Interdependence Model was able to describe the reduction in grain size caused by the growth restriction provided by Y and soluble Zr, and the introduction of potent Zr particles. It is shown that by incorporating a term for cooling rate into the Interdependence model the effect of cooling rate on grain size can be assessed for the range of growth restriction values and cooling rates investigated.

Different atmospheric gas molecules (e.g., N2, O2, CO2, H2O, CO, NO, NO2, NH3, and SO2) are absorbed on the pristine hexagonal boron arsenide (BAs) through density functional theory calculations. For each gas molecules, various adsorption positions were considered. The most stable adsorption depended on position, adsorption energy, charge transfer, and work function. SO2 gas molecules had the best adsorption energy, the shortest distance for BAs surface in the atmospheric gas molecule, and a certain amount of charge transfer. The calculation of work function was important for exploring the possibilities of adjusting the electronic and optical properties. Our results presented BAs materials can be the potential gas sensor of SO2 with high sensitivity and selectivity.

In this paper, we investigated SO2 adsorption on B, N, P and Al doped MoS2, which band structure, density of states, charge transfer, etc by the density function theory (DFT) calculation. Results show that the SO2 prefer to be absorbed at the top of Mo atom of MoS2. It is found that SO2 is strongly adsorbed on Al-MoS2 with considerable adsorption energy of −1 to −2.33 eV, however, the best adsorption position is the top of Mo atom of Al-MoS2, which the biggest Ea is −2.33 eV, the best charge is −0.343e and the shortest d is 1.763 A. So these findings confirm that Al-MoS2 can be used to detect the presence of SO2 in the environment.

Through a first-principles study based on density functional theory, a physical model of CO2 gas molecule adsorption on an InSe monolayer was designed and built. The geometric structures of the InSe monolayer doped with different transition metal elements were optimized, and the spin-polarized energy band structure and magnetoelectric properties, such as the density of states, semimetallicity and magnetic moment of nanosheets with stable adsorbed phases, were calculated. The microscopic mechanism of these properties was analyzed by crystal field theory, and it was found that InSe monolayers are typical semiconductors, but transition metal–InSe monolayers can conduct electricity and are typical semi-metallic nanosheets. Second, the adsorption mechanism of CO2 gas molecule adsorption on InSe monolayers is studied. The calculation results show that when the O atom of the CO2 gas molecule is adsorbed on the surface of an InSe monolayer, the adsorption structure is relatively stable. The surface adsorption is mainly due to the transition of electrons on the InSe monolayer surface to the CO2 gas molecule. The doping of metal atoms gives CO2 gas molecules strong adsorption energy, promotes the magnetic properties of the adsorption system, and completes the transition from semiconductor to metal. The change of the work function of the adsorption system before and after doping indicates that this doping method can also enhance the sensitivity of the InSe monolayer to CO2 gas molecules.

Non-penetration laser welding of lap joints in austenitic stainless steel sheets is commonly preferred in fields where the surface quality is of utmost importance. However, the application of non-penetration welded austenitic stainless steel parts is limited owing to the micro bulging distortion that occurs on the back surface of the partial penetration side. In this study, non-penetration lap laser welding experiments, were conducted on galvanized and SUS304 austenitic stainless steel plates using a fiber laser, to investigate the mechanism of bulging distortion. A comparative experiment of DC01 galvanized steel-Q235 carbon steel lap laser welding was carried out, and the deflection and distortion profile of partially penetrated side of the sheets were measured using a non-contact laser interferometer. In addition, the cold-rolled SUS304 was subjected to heat holding at different temperatures and water quenching after bending to characterize its microstructure under tensile and compressive stress. The results show that, during the heating stage of the thermal cycle of laser lap welding, the partial penetration side of the SUS304 steel sheet generates compressive stress, which extrudes the material in the heat-affected zone to the outside of the back of the SUS304 steel sheet, thereby forming a bulge. The findings of these experiments can be of great value for controlling the distortion of the partial penetrated side of austenitic stainless steel sheet during laser non-penetration lap welding.

The interaction of CH4 gas molecule on pure graphene and Al, B, N, P doped mono-vacancy graphene by using the density functional theory (DFT) to explore their potential applications as gas sensors. The results demonstrate that the system of Al doped mono-vacancy graphene is the most stable, and Al-doped mono-vacancy graphene performs the largest adsorption energies upon CH4 with the most appreciable effects on the electronic structures. In addition, the adsorption of CH4 can largely enhance the conductivity of these graphene. In summary, we believe that the Al-doped mono-vacancy graphene could be a promising candidate material for the CH4 gas sensors.

The adsorption of Hg2+ on thermally modified molybdenum disulfide was explored in this work. The X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM) results revealed that thermal treatment led to partial oxidation of MoS2 to MoO3 and a creation of edge defects on the surface of molybdenum disulfide. The density functional theory (DFT) calculation indicated that the oxidative etchings were terminated with oxygen atoms, and both the vacancy and perfect surface could be oxidized during thermal treatment. The batch tests indicated that thermal treatment enabled the surface of molybdenum disulfide to be highly reactive as Hg2+ adsorbent. The adsorption rate and capacity of 500 °C heated molybdenum disulfide were 17.6 times faster and 11-fold higher compared to that of molybdenum disulfide without thermal modification. The tremendous enhancement of Hg2+ adsorption was significantly related to the oxidation of molybdenum disulfide and the increase of atom activity ...

In this work, graphene for use as methane (CH4) sensors has been designed and evaluated via first-principles theory. Firstly, the effect of the number of layers of graphene on methane adsorption is investigated. The results show that the methane adsorption will be increased with the number of layers, the maximum energy is 0.267 eV. Furthermore, the adsorption of CH4 leads to a small opening of the band structure of graphene. As for the doping (Al-doped) in graphene, we mainly focus on the concentration of Al atoms. The Al atom was found to cause a huge increment in methane adsorption energy that can be up to 3.212 eV when the concentration of Al atoms is 5.555%. Meanwhile, the doping of Al atoms also enhances the conductive properties of graphene. Lastly, the effect of defects was also investigated. While slightly smaller than that of pristine graphene, the methane adsorption energy of defected graphene is also increased with the number of layers. It was found that the model with the methane on the top of the empty atom and the H atoms on the top of the center of the carbon ring results in the best methane adsorption. Keywords: Adsorption, Band structure, Density-functional theory, Methane sensor

For the problems of privacy data protection caused by massive data sharing in the construction of power Internet of things, a data sensitivity measurement and classification model based on information entropy and BP neural network is proposed. Firstly, a recognition matching algorithm is proposed to identify the sensitive level of attributes in the dataset, and the information entropy is used to determine the weight of attributes sensitivity level, so as to calculate the sensitivity measurement value of records in the dataset; finally, the BP neural network is used to output the data classification results. The experimental results show that the model can achieve accurate measurement and classification of data, with low incorrect judgment rate and error rate.

Hg0 has gradually become a serious environmental problem that need to be solved, due to its strong volatility and insolubility in water. In this study, the adsorption behavior of X(O, Se, Te)-doped monolayer MoS2 for was studied via DFT calculation to evaluate its potential for Hg0 removal. Oxygen group atoms X(O, Se, Te) doped MoS2 systems all have extremely high bonding energies, in which the strong interaction between the dopant atoms and the S vacancy of monolayer MoS2, resulting that dopant systems were greatly stable. Compared with pristine monolayer MoS2, X(O, Se, Te)-doped MoS2 has stronger adsorption performance and electrical conductivity in adsorbing Hg0, which is mainly attributed to the facilitation of electrons transfer between Hg0 and MoS2. The oxygen doping system exhibits best adsorption performance to Hg0, primarily due to the relatively stronger interaction between the dopant oxygen and Hg0. The results reveal that the O-doped monolayer MoS2 can effectively improve the adsorption efficiency of Hg0 increasing the application potential for mercury emissions control in coal-fired power plants.

Strain modulation is one of the most popular tuning methods for the electronic properties of low-dimensional systems. In the present work, by using first-principle calculations, strain engineering is used to module the band gap transition of two novel van der Waals (vdW) heterostructures based on 2D Blue Phosphorene (Blue P) supported on XC (X = Ge, Si), producing Blue P/XC bilayer systems. The results show that the biaxial strain is more effective than uniaxial strain for controlling the electronic properties of Blue P materials. The band gap of Blue P/GeC vdW heterostructures increases when increasing the strain value from −8% to 0%, whereas after 0% strain value not increases in the band gap is observed. The band gap of Blue P/SiC vdW heterostructures increased and reached the maximum of 1.09 eV at strain value of 0%, and it decreased with further increasing of strain value. The present work provides an effective avenue to tune the electronic structure and band gap of Blue P/XC vdW heterostructures.

Base on the strong activation activity and affinity of transition metal ions and MoS2 for peroxymonosulfate (PMS), respectively, Co(Ⅱ)-doped MoS2 nano-flowers (Co-MoS2 NFs) with a great photo-response property was facilely synthesized to achieve a more efficient PMS activation for ofloxacian (OFX) degradation. It was found that Co-MoS2 NFs exhibits superior catalytic activity for OFX degradation under visible-light irradiation, which was attributed to the synergetic effect of doped Co(Ⅱ) and photo-generated carriers to PMS activation. Besides, Co-MoS2 NFs was able to efficiently degrade OFX within 4 cycles in the presence of PMS while leaked minute amount of Mo and Co ions, implying the excellent cycle stability of Co-MoS2 NFs. Furthermore, SO4•− and 1O2 were detected as the primary reactive radicals for OFX degradation in the Co-MoS2 NFs-PMS system through EPR and quenching tests. This new strategy of coupling doped Co(Ⅱ) and photo-generated carriers for more efficient PMS activation, which will greatly benefit the development of SO4•−-based AOPs as well as cater to the demand for environmental remediation in the future.

Optimizing post-deformation cooling conditions can to a great extent control grain size and texture in the hot forming components, especially larger-size ones. Here, we investigated the effects of pre-strains and 400 °C isothermal annealing on the microstructural evolution of AZ31B magnesium alloy after isothermal compression. For the pre-strain exceeding ~6%, grains coarsen immediately without the need of an incubation period. The rapid coarsening mainly happens for a group of strain-free grains with grain orientation spread value lower than 0.5°. Two kinds of strain-free grains in the pre-strained microstructure are mainly responsible for the rapid increase in grain size. One is the undeformed grains at the pre-strain of 6%. The other is the dynamic recrystallized grains when the pre-strain is higher than 10%. Driving force for the preferential grain growth is ascribed to the difference in stored strain energy between deformed and strain-free grains. The final grain size after 900 s annealing decreases with the increase in pre-strain level. As both c-axes of undeformed grains and dynamic recrystallized grains are nearly parallel to the compression direction, the preferential growth of these grains results in an enhanced basal texture after annealing. These results demonstrate that larger deformation extent and instant cooling can effectively refine grains and weaken the texture of magnesium alloy during hot forming.

Herein, we report on the doping of monolayer WSe2 with Pd, Ag, Au, and Pt as a promising approach to improve the gas sensing performance of the 2D material. The adsorption of CO2, NO2 and SO2 gas molecules on Pd, Ag, Au, and Pt-doped monolayer WSe2 are studied in terms of adsorption energy, charge transfer and band structure. Results suggest that NO2 adsorption on Ag-WSe2 monolayer is energetically favorable giving rise to the most stable configuration. NO2 is chemisorb on the doped monolayer surface due to a strong interaction. We study the influence of applying strain on the gas molecule/TM-WSe2 adsorption systems. Increasing the stain, the adsorption properties decrease for NO2. Our results indicate that Ag-WSe2 monolayer is a great candidate for the development of efficient NO2 gas sensors.

Novel molybdenum disulfide-montmorillonite (MoS2@2DMMT) hydrogels for Cu(II) removal and inhibition on bacterial growth were successfully prepared. MoS2 was first in-situ growth onto 2DMMT platelet through hydrothermal method and then cross-linked with organic reagents to form hydrogels. The flower-like structure of synthesized MoS2 could be clearly observed in MoS2@2DMMT by SEM. The synthesized hydrogels possessed a three-dimensional macroporous structure, offering a free access for contaminants to get inside and combine with the active sites. Adsorption tests revealed that efficient Cu(II) removal (65.75 mg/g) could be achieved within a short time (30 min) at pH 5. The pseudo-second-order kinetics model and Langmuir isotherm model indicated the existence of chemisorption and monolayer absorption for Cu(II) onto MoS2@2DMMT hydrogels. Characterizations of EDS and XPS indicated that Cu(II) reacted with groups of carboxyl, hydroxyl and amidogen. Bacteriostatic tests revealed that almost a complete bacteriostatic was achieved with just small dosage (0.8 mg/mL) of MoS2@2DMMT hydrogels after the Cu(II) removal under the normal illumination. The mechanism was ascribed to the destructive effect of Cu(II) to the cytomembrane and the damage of reactive oxygen species (ROS) to the DNA. Such hydrogel not only provided insights for treating co-existing contaminates, but also guides for designing novel polymer materials from two-dimensional (2D) nano-materials.

Aiming at the problems that the experience of network security personnel in power system is difficult to solidify, and the basic and repetitive vulnerability mining work is intelligently replaced by the lack of experience guidance, this paper studies the experience solidification learning technology of power system vulnerability intelligent mining. Format specification and parsing language of vulnerability intelligent mining experience tree are proposed, which can transform flexible and complex vulnerability mining experience into a language that can be recognized and understood by machine. At the same time, it puts forward the solidification and intelligent learning technology of vulnerability mining experience, through the automatic pervasion test for the target, combined with reinforcement learning algorithm, intelligent learning generates vulnerability mining experience tree, and finally forms the high-efficient transformation of the red team personnel experience and the intelligent substitution of part of the work.

We predict the CO2, NO, NO2 and SO2 gas molecule absorption and sensing performance of transition metal (Fe, Ni, Co and Cu) doped graphene by a systematic density functional theory (DFT) study. Our results demonstrate that graphene doped with different transition metal atoms produces completely different adsorption behaviors of small gas molecules originated from changes in the electronic structure of the systems under strain. Graphene doped with Fe atoms was the best platform for sensing NO2 gas molecules (NO2/Fe-MG). The NO2/Fe-MG system showed the best adsorption rate, the higher charge transfer and the shortest distance between the graphene platform and the gas molecule of all the calculated systems. As the strain increases, the adsorption energy and charge transfer decreases. So the NO2 gas molecule adsorption properties of Fe-MG without strain would help in guiding experimentalists to develop better materials based on graphene for efficient gas detection or sensing applications.

The adsorption behaviors of methane adsorbed on different graphenes (pristine, and B-, N-, P-, and Al-doped monolayer and multilayer) are analyzed using density-functional theory. The results demonstrate that the sensing performance of graphene as a methane sensor strongly depends on the selection of dopants and the number of layers. The adsorption energy on monolayer P-doped or Al-doped graphene shows about one order of magnitude higher than that with other dopants. In addition, graphenes doped with different impurities show different responses to the charge transfer. A further analysis indicates that the multilayer structure has a positive effect on the adsorption energy on the pristine, B-doped, and N-doped graphene, while the P-doped or Al-doped graphene shows a significant decrease with the increase in the number of layers. Moreover, the multilayer structure has a minor effect on the charge transfer. Based on the combined effects on the adsorption energy and the charge transfer, Al-doped monolayer graphene is the optimal candidate for methane sensing.

The weld metal with high strength and good toughness was obtained for medium thickness microalloyed steel by using high power laser hybrid welding technology. Mechanical properties of weld metal were evaluated by using room temperature tensile test and low temperature three-side Charpy V-notch (CVN) impact test. The results show that the yield strength and ultimate tensile strength of weld metal are up to 713 MPa and 918 MPa, respectively. Both of them are almost 1.5 times higher than those of base metal. Under the strict three sides CVN condition, the −40 °C low temperature impact absorbed energy is up to 32 J and also higher than that of base metal. Weld metal predominately consists of granular bainite and carbon-free bainite. Both of them mainly contain lath morphology bainitic ferrite. The lath morphology bainitic ferrite with fine grain size plays an important role in higher strength. Dispersive carbide and high density dislocation are found in strengthening weld metal.

At present, the sensor is widely used and its types are varied, such as biosensor, gas sensor, humidity sensor, optics sensor, pressure sensor, etc. However, many defects of sensors remain to be optimized in many aspects such as conductivity, stability and adsorption capacity. According to the performance of materials, the study of the adsorption behavior of H 2 , CO 2 , CH 4 , Ar and N 2 on the pristine graphene has been performed through First-principle calculation. The graphene has been attracted popular attention all over the world, because the two-dimensional crystal structure of graphene has a good mechanical, electrical properties etc. The graphene also has a great specific surface area, so it has a well adsorption capacity. The graphene is a zero-n gap semiconductor with no magnetism, however, the graphene will be magnetic if it adsorbed or doped with other materials even the band gap is opened. Therefore, the graphene has a promising future in nano electronic devices such as gas sensor. We compared the electronic structures and the magnetism between the pristine graphene and the gas molecule-adsorbed graphene through the first principle calculation. We have found that the different types of graphene have different electronic band structures. Most of the molecules adsorption on graphene can be weakly charged took as donor or acceptor. We discovered that the band gap and the adsorption energy is different when the gas molecules adsorped on the graphene with different number of layers. The different layers have different impacts on the adsorption of graphene. Therefore, according to First principles calculation, with the number of layers increasing, the gas adsorption property of graphene is getting better and better. This study provides a rational way using first principle simulation to evaluate the different number of layers of graphene for the adsorption of sensors.

Recently, the polytype transformation of SiC has been studied at temperatures over 2000 K or at high pressures. However, there are no theoretical or experimental works exploring phase transformation during grinding process of SiC to date. In this work, the grinding characteristics such as temperature rise, high dynamic pressure and shock effect are compared with conditions for phase transition. For the first time, X-ray diffraction analysis of ground SiC under different machining conditions reveals that phase transition in high-speed cylindrical grinding occurs and strongly affects the residual stresses on the surface layer. Furthermore, a way to reduce the residual stresses by a combination of the elevated grinding wheel velocity and the higher workpiece speed is proposed.