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α-4CaO·5B 2 O 3 ·7H 2 O (sheet-like structure) and three polymorphs of β-4CaO·5B 2 O 3 ·7H 2 O (flower-like, succulent plant-like and book-like structure) were prepared by hydrothermal method, and characterized by XRD, FTIR, TG-DTA-DTG, SEM. The activation energies (Ea) of the two-step thermal dehydration of 4CaO·5B 2 O 3 ·7H 2 O with different morphologies and phases were calculated by Kissinger-Akahira-Sunoes (KAS) method. The most probable mechanism function of the two-step dehydration reaction was determined by Coats-Redfern (CR) method, and the average pre-exponential factor (A) of the two-step thermal dehydration of the sample was calculated. The results showed that the thermal dehydration of 4CaO·5B 2 O 3 ·7H 2 O was divided into two steps. The activation energy of thermal dehydration reaction was affected by the phase, morphology and particle size. The activation energies of the two-step thermal dehydration of β-4CaO·5B 2 O 3 ·7H 2 O(flower-like, succulent plant-like and book-like structure) all decrease in turn, which is consistent with the change trend of particle size. The average pre-exponential factor of the first-step thermal dehydration of all samples is smaller than that of the second-step thermal dehydration. The mechanism functions of the first-step and second-step thermal dehydration stages are Jander equation [1-(1-α)1/3]2 and Z-L-T equation [(1-α)−1/3-1]2, respectively, which belong to three-dimensional diffusion. The three-dimensional diffusion process of the two-step thermal dehydration was analyzed and explained. [Display omitted] • α-4CaO·5B 2 O 3 ·7H 2 O and three polymorphs of β-4CaO·5B 2 O 3 ·7H 2 O were prepared by hydrothermal method. • The activation energy of thermal dehydration reaction is affected by the phase, morphology and particle size. • The activation energy of β-4CaO·5B 2 O 3 ·7H 2 O two-step thermal dehydration varies with its orphology. • The mechanism functions of the first-step and second-step thermal dehydration stage were proposed. • The three-dimensional diffusion process of the two-step thermal dehydration is analyzed and explained. [ABSTRACT FROM AUTHOR]

Purpose: This study proposes a tensegrity-based traction structure with D-bar dual cable units. It is used to connect the airship and the ground to stabilize the airship. Design/methodology/approach: The mathematical models and dynamic models of the D-bar dual cable (hereafter referred to as DD cable) unit of the tensegrity-based traction structure are established. Based on the minimum mass method, the mass of the DD cable unit in the critical state (cable member is yielding, or bar member is buckling or yielding) is analyzed. Then, the tensile strength of the DD cable unit and single cable unit under the same condition is compared using the control variate method. Finally, based on ANSYS dynamic simulation, the stability of the two structures under the same external force disturbance was tested. Findings: Expressions for the minimum mass of the DD cable unit under different failure conditions are solved. Dynamic simulation results show that the capacity of resisting disturbance of the DD cable unit is much better than that of the single cable unit under the same wind speed. So, we find a structure more suitable for the fixed connection of an airship. Originality/value: This study helps to provide theoretical reference and thinking for the practical application of the traction structure with a D-bar dual cable unit. [ABSTRACT FROM AUTHOR]

Sheet-like and rod-like nano Ca 5 (PO 4) 3 (OH):0.05 Eu3+, xLi+(x = 0.01−0.07) phosphors were prepared by hydrothermal method. The structure, morphology and luminescent properties of samples were characterized by XRD, EDS, SEM, TEM and PL. The effects of morphology and Li+ doping on the luminescent properties of Ca 5 (PO 4) 3 (OH):Eu3+ were studied. The results show that Li+ doping has little effect on the luminescent peak position and CIE color coordinate of sample, but it affects the crystallinity of sample and effectively improves its luminescence intensity. It was found that the luminescent properties of the samples were greatly affected by their morphology. The optimum Li+ doping amounts of nano sheet-like and rod-like Ca 5 (PO 4) 3 (OH):0.05 Eu3+, xLi+ are 5 mol% and 3 mol% respectively. The luminescent intensity of the sheet-like sample was stronger than that of the rod-like sample. The luminescent lifetimes of nano rod-like sample is longer than that of the nano sheet-like sample. [ABSTRACT FROM AUTHOR]

A 6G network is not only faster, but also offers a wider range of services than 5G networks, which will lead to an increased number of participants. However, combined with the Internet of Everything, 6G networks face security issues such as man-in-the-middle hijacking and bypass listening. Because covert transmission is inherently highly concealed and difficult to detect, a 6G network based on information hiding has become a new paradigm to solve such security problems. In this article, we propose a large-capacity local multi-dimensional information hiding method based on orthogonal space and spread transform. By extending the quantization index modulation hiding approach, the proposed method hides the multi-layer information in digital signals' multi-dimensional space using orthogonal space and spread transform. In theory, this method can hide information in multiple layers at the same location while allowing the extraction of information from multiple layers independently. This proposed method offers a much higher hiding capacity than prior work. Through performance analysis and comparison against existing advanced methods, we demonstrate the superiority of the proposed scheme. [ABSTRACT FROM AUTHOR]

Polycrystalline 4ZnO·B 2 O 3 ·H 2 O with flower-like, spherical-like and sheet-like morphologies have been synthesized and characterized by XRD, TG–DSC, SEM and TEM. The molar enthalpies of solution of 4ZnO·B 2 O 3 ·H 2 O with different morphologies in 1 mol L−1 HCl(aq) were measured. With the incorporation of the previously determined enthalpy of solution of H 3 BO 3 in 1 mol L−1 HCl(aq), the enthalpy of solution of ZnO in (HCl + H 3 BO 3)(aq) and the standard molar enthalpies of formation of ZnO(s), H 3 BO 3 (s) and H 2 O(l), the standard molar enthalpies of formation of 4ZnO·B 2 O 3 ·H 2 O with flower-like, spherical-like, and sheet-like morphologies were calculated to be -(3033.91 ± 2.03), -(3030.91 ± 2.03) and -(3025.94 ± 2.04) kJ·mol−1, respectively. [Display omitted] • The standard molar enthalpies of formation of 4ZnO·B 2 O 3 ·H 2 O with three different morphologies were measured. • The enthalpies of solution of 4ZnO·B 2 O 3 ·H 2 O with three different morphologies were determined by microcalorimeter. • The standard molar enthalpies of formation of 4ZnO·B 2 O 3 ·H 2 O with different morphologies are different. [ABSTRACT FROM AUTHOR]

For the current, the thermal analysis sample cups used to predict the carbon and silicon content of cast iron melts are relatively large and take a long time for each measurement, a smaller cylindrical thermal analysis sample cup with an inner diameter of 25 mm and a height of 55 mm was studied for the analysis of carbon and silicon. The thermal analysis system can quickly measure the temperature characteristic values of the liquidus temperature TL and the eutectic temperature TE of the temperature curves related to carbon equivalent, carbon content and silicon content within 2 min, and mathematical models for the prediction of carbon equivalent CEL (3.2–4.7), carbon content C% (3.0–4.0%) and silicon content Si% (1.0–2.5%) was established by multiple linear regression in combination with optical emission spectroscopy: C E L = 15.3426 − 0.009565 × T L , C % = − 6.36 − 0.007934 × T L + 0.01717 × T E , S i % = 58.7207 − 0.049322 × T E − 0.001619 × T L. We had checked the accuracy, the average error of carbon equivalent and carbon content and silicon content did not exceed 0.05%. [ABSTRACT FROM AUTHOR]

• A novel Ti 1−x Fe x O 2 nanoarchitectures (NAs-Ti 1−x Fe x O 2) was facilely prepared by a hydrothermal process. • NAs-Ti 1−x Fe x O 2 exhibit excellent photocatalytic performance due to the active atoms exposed on (101) and (001) surfaces. • Fe3+ could convert Fe2+ and Fe4+ by capturing carrier (e- and h+) on the (101) and (001) surfaces. • NAs-Ti 1−x Fe x O 2 have promising applications in environmental remediation due to its efficient performance. • Photocatalytic mechanism of degradation of antibiotics was proposed. [Display omitted] Facing the increasing antibiotics pollution, it is essential to develop novel and highly efficient photocatalysts in purification systems. Herein, Fe3+-incorporated tetragonal bipyramid anatase TiO 2 nanoarchitectures (NAs-Ti 1−x Fe x O 2) with exposure of highly active atoms (Fe, O and Ti) on the (101) and (001) surfaces were prepared via a hydrothermal process. Experimental studies show that these fabricated NAs-Ti 1−x Fe x O 2 exhibit excellent photocatalytic performance for degradation of pollutant antibiotics. Based on the stabilization mechanism, a detailed analysis of many active atoms were stabilized on the (101) and (001) surfaces of NAs-Ti 1−x Fe x O 2 due to Ti–O/Ti–F/Fe–F bond attractions. A series of characterization experiments show that Fe3+ is regarded as a significant component and participated in the reaction process for antibiotics degradation. Besides, high exposure of active atoms due to this Fe3+ incorporated tetragonal bipyramid anatase TiO 2 (one dimensional sizes verge on 1–3 nm) further improves the separation efficiency of photogenerated carriers and free radical yield than traditional nanomaterials. What's more, the photoinduced electrons are also easier to transfer to the (101) crystal plane and the holes remained on the (001) crystal plane. In conclusion, excellent performance can be amplified, which is derived from smaller nanometric size. This study provides an insight into the enhanced photocatalytic degradation of pollutant antibiotics employing the Fe3+-incorporated tetragonal bipyramid anatase TiO 2. [ABSTRACT FROM AUTHOR]

In the indoor environment, where global positioning system (GPS) fails, the presence of multipath, non-line-of-sight (NLOS), and dense scatterer yields unreliable position estimation. In the massive multiple-input multiple-output (massive MIMO) system, the sparse channel property is exploited here for user localization as an integral part of the network to reduce the power of user equipment (UE). In this study, a novel spatial spectrum fusion estimation and localization (SSFEAL) algorithm using the uniform circular array (UCA) structure is proposed, which is based on the 2-D direction of arrival (DOA) estimation. The spatial spectrum of the incoherent narrowband uplink pilot signal on each frequency bin received at the distributed massive MIMO base stations (BSs) is used for spectrum fusion. The main contributions of this work are as follows: 1) the channel’s sparse characteristics at individual BSs are used to synthesize the covariance matrix of the received signal at the central fusion center and 2) the proposed method has 2-D spatial information measurement fusion to generate informative spatial spectrum followed by grid refinement processing to reduce the localization error to submeter level. It is demonstrated that the proposed method using UCA gives higher resolution estimation performance compared with the rectangular array in the localization accuracy. Comprehensive Monte Carlo simulation and real application test results show the validity and submeter precision in the indoor environment. [ABSTRACT FROM AUTHOR]

The effects of rare-earth (RE) micro-alloying on the microstructures, mechanical properties, and internal friction (IF) of 51CrV4 steels after quenching and tempering were investigated. The addition of RE elements was beneficial for refining the size of the martensite and increasing the fraction of twins in the 51CrV4 steels. The RE-51CrV4 steel possessed a high dislocation density and a large fraction of low-angle grain boundaries after quenching. Cr7C3 carbides of RE-51CrV4 steel tended to precipitate along the lath martensite interfaces and were easily spheroidized during tempering. With the addition of RE elements, the Snoek–Köster–Kê (SKK) peak was increased after quenching but decreased after different tempering times. The results of the IF and high-resolution transmission electron microscopy analyses indicated that RE atoms formed micro-segregations at the lath martensite interfaces and resulted in a pinning effect on the carbon atoms. Therefore, the hardenability of the RE-51CrV4 steel was reduced, whereas its elongation improved significantly due to the presence of high-density twins and spheroidized carbides. • Rare earth (RE) atoms formed micro–segregations at lath martensite interfaces. • RE atoms have a pinning effect on carbon atoms in heat treatment process. • The morphology of the carbides becomes spherification in RE-51CrV4 steel. • The addition of RE elements is helpful to refine the size of martensite. [ABSTRACT FROM AUTHOR]

In cognitive radio enabled vehicular ad-hoc networks (CR-VANETs), the secondary users, i.e., the secondary intelligent vehicles have the ability to perceive the driving environment and use the unoccupied spectrum of primary users for data transmission. In this paper, we consider the radar assisted CR-VANETs, in which the secondary users firstly sense the surroundings using radar modules periodically and Swerling 0, Swerling 2 and Swerling 4 target models are considered respectively. Note that the secondary users access the spectrum of primary users and communicate with their corresponding receivers when no one is detected by the low range radar module. Moreover, we design the joint radar sensing and data transmission frame structure and formulate the radar sensing-throughput tradeoff problem mathematically. It is proved that the formulated tradeoff indeed has the optimal radar sensing time which yields the maximum throughput for the secondary networks. Numerical results and simulations verify that the optimal radar sensing time achieving the maximum throughput for Swerling 0 target model is ${0.05}\; \text{ms}$ when the radius of the radar sensing region is 320 meters, the densities of the primary users and secondary users are $\lambda _p=0.01 / m^2$ and $\lambda _s=0.2 / m^2$ , the received radar SNR is 10 dB and the detection probability is 99.9%. For the Swerling 2 and Swerling 4 target models, the optimal radar sensing times achieving the maximum throughput is ${0.14}\; \text{ms}$ and ${0.08}\; \text{ms}$ respectively when the detection probability is 99%. [ABSTRACT FROM AUTHOR]

This paper investigates a cache-aided mobile edge computing (MEC) network, where the source offloads the computation task to multiple destinations with computation capacity, with the help of a cache-aided relay. For the proposed cache-aided MEC networks, two destination selection criteria have been proposed to maximize the computation capacity of the selected destination, the channel gain of relay link and the channel gain of direct link, respectively. Similarly, three destination selection criteria have been proposed for the cache-free MEC networks based on the computation capacities of destinations and the channel gains of transmission links, respectively. To evaluate the system performance regarding the latency constraint, we provide the outage probability for the proposed network which is defined based on the transmission-plus-computation time. Our analysis suggests that caching can significantly alleviate the impact of increasing the size of computation task, since only half of the transmission time of cache-free network is required. However, the cache-aided network can not fully exploit the signal from both direct and relay links, thus the improvement by caching is less significant in the high signal-to-noise ratio (SNR) region, compared with the cache-free network employing the destination with maximal channel gain of direct link. Numerical results are given to validate our analysis. [ABSTRACT FROM AUTHOR]

A novel flame retardant poly (piperazine phosphaphenanthrene) (DOPMPA) was successfully synthesized via two step reactions using DOPO and piperazine as reactants and characterized by infrared spectrometry (FT-IR), nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). The DOPMPA was used to enhance flame retardancy of epoxy resin (EP). When the addition content of DOPMPA in EP was 13 wt%, the EP/DOPMPA sample passed a UL-94 V-0 rating and possessed a high limited oxygen index (LOI) value of 34%. Cone calorimeter tests showed that the release of heat and smoke for EP/DOPMPA samples decreased significantly compared with neat EP. Moreover, the reduction of average effective heat of combustion (av-EHC) value with the increased addition of DOPMPA confirmed that DOPMPA had a flame-inhibition activity in gashouse phase. The analysis of the char residues after cone calorimeter test exhibited that DOPMPA promoted the swell of the sample and compacted char layer. Furthermore, the pyrolysis analysis of DOPMPA was investigated by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), which illustrated that DOPMPA decomposed into many fragments with quenching effect toward combustion. • A novel flame retardant (DOPMPA) containing DOPO and piperazine structure was synthesized. • DOPMPA endowed EP with excellent fire safety. • DOPMPA played a flame-retardant role in both condensed and gaseous phases. [ABSTRACT FROM AUTHOR]

The Xianshuihe fault (XSHF) zone is an important lithospheric structure in east Tibetan Plateau. The Zheduo-Gonggar massif, about 120 km long and 13–18 km wide, developed along its eastern segment. Based on geological mapping, meso- and micro-structure studying and geochronology testing, the massif is divided into 5 units: (1) Intrusions of 216–204 Ma, (2) Intrusions of ∼170 Ma, (3) mid-Jurassic sillmanite-grade metasediments, (4) Oligo-Miocene migmatite zone, (5) Intrusions less than 20 Ma ago. Intrusions of 216–204 Ma related to the Songpan–Garze folding and distributes on the southern segment of the massif. The middle Jurassic intrusions which were found for the first time in the region, includes the syn-kinematic Zheduoshan granite and a suit of leucogranite. The former constrained by the youngest U–Pb age of 171 Ma which provides a minimum shear age of the XSH fault. The latter, U–Pb age of 170 Ma, is a common feature of convergent orogens or intracontinental subduction. The Oligo-Miocene migmatite zone, about 80 km long and 1–3 km wide, developed on the eastern edge of the massif. Intrusions less than 20 Ma ago is located on the northern segment of the massif. It had been widely researched that the latter two units are associated to the Cenozoic deformation of the XSH fault. While the mid-Jurassic syn-kinematic magmatism, anatexis and metamorphism along the XSH fault suggests a more strong Mesozoic tectono-thermal event in the fault zone. The discoveries provide us with a new perspective on understanding the Mesozoic and Cenozoic deformation of the XSH fault zone, southeastern Tibet. [ABSTRACT FROM AUTHOR]

Water injection into coal seams is important for dust prevention in mines. However, owing to the hydrophobicity of coal itself, the wetting effect of water injection on coal seams has yet to be enhanced. Herein, based on the hydrophobicity of coal, hydrophilic modification of the coal surface has been proposed via co-deposition of polydopamine (PDA) and polyacrylamide (PAM). Using water contact angle (WCA) test, atomic force microscope (AFM) test, X-ray photoelectron spectroscopy (XPS) characterization, and 1H nuclear magnetic resonance spectroscopy (1H NMR) measurements, the feasibility of hydrophilicity modification of coal by PDA/PAM has been investigated. The results indicate that when DA concentration is 2 mg/mL, deposition time is 45 min, and DA/PAM feeding molar ratio is 1:1, the wettability of modified coal sample clearly improves. In the water content test and dust-production test using gravity drop hammer, the modified coal exhibits good wettability and low dust production. Also, UV-Vis absorption spectroscopy and WCA results suggest that PDA/PAM coating exhibits good stability. Therefore, the modification method can effectively enhance the wetting effect of injected water on coal seam, providing a novel approach for dust prevention. [Display omitted] • A method of hydrophilic modification of coal by injecting water into coal seam with PDA/PAM is proposed. • Hydrophilic modification of coal by PDA/PAM can significantly improve the wettability of coal. • PDA/PAM modified coal samples have lower dust production ability. [ABSTRACT FROM AUTHOR]