bluuebunny/crossref_metadata_2025 huggingface dataset:
Multifractal structure of the monthly rainfall regime in Catalonia (NE Spain): Evaluation of the non-linear structural complexity
Authors: Lana X. , Rodríguez-Solà R. , Martínez M. D. , Casas-Castillo M. C. , Serra C. , Kirchner R.
Published: July 2020

The complex non-linear regime of the monthly rainfall in Catalonia (NE Spain) is analyzed by means of the reconstruction fractal theorem and the multifractal detrended fluctuation analysis algorithm. Areas with a notable degree of complex physical mechanisms are detected by using the concepts of persistence (Hurst exponent), complexity (embedding dimension), predictive uncertainty (Lyapunov exponents), loss of memory of the mechanism (Kolmogorov exponent), and the set of multifractal parameters (Hölder exponents, spectral asymmetry, spectral width, and complexity index). Besides these analyses permitting a detailed description of monthly rainfall pattern characteristics, the obtained results should also be relevant for new research studies concerning monthly amounts forecasting at a monthly scale. On one hand, the number of necessary monthly data for autoregressive processes could change with the complexity of the multifractal structure of the monthly rainfall regime. On the other hand, the discrepancies between real monthly amounts and those generated by some autoregressive algorithms could be related to some parameters of the reconstruction fractal theorem, such as the Lyapunov and Kolmogorov exponents.
Guided search for desired functional responses via Bayesian optimization of generative model: Hysteresis loop shape engineering in ferroelectrics
Authors: Kalinin Sergei V. , Ziatdinov Maxim , Vasudevan Rama K.
Published: July 2020

Advances in theoretical modeling across multiple disciplines have yielded generative models capable of high veracity in predicting macroscopic functional responses of materials emerging as a result of complex non-local interactions. Correspondingly, of interest is the inverse problem of finding the model parameter that will yield desired macroscopic responses, such as stress–strain curves, ferroelectric hysteresis loops, etc. Here, we suggest and implement Gaussian process based methods that allow to effectively sample the degenerate parameter space of a complex non-local model to output regions of parameter space which yield desired functionalities. We discuss the specific adaptation of the acquisition function and sampling function to make the process efficient and balance the efficient exploration of parameter space for multiple possible minima and exploitation to densely sample the regions of interest where target behaviors are optimized. This approach is illustrated via the hysteresis loop engineering in ferroelectric materials but can be adapted to other functionalities and generative models.
Molecular simulation of liquid–vapor coexistence for NaCl: Full-charge vs scaled-charge interaction models
Authors: Kussainova Dina , Mondal Anirban , Young Jeffrey M. , Yue Shuwen , Panagiotopoulos Athanassios Z.
Published: July 2020

Scaled-charge models have been recently introduced for molecular simulations of electrolyte solutions and molten salts to attempt to implicitly represent polarizability. Although these models have been found to accurately predict electrolyte solution dynamic properties, they have not been tested for coexistence properties, such as the vapor pressure of the melt. In this work, we evaluate the vapor pressure of a scaled-charge sodium chloride (NaCl) force field and compare the results against experiments and a non-polarizable full-charge force field. The scaled-charge force field predicts a higher vapor pressure than found in experiments, due to its overprediction of the liquid-phase chemical potential. Reanalyzing the trajectories generated from the scaled-charge model with full charges improves the estimation of the liquid-phase chemical potential but not the vapor pressure.
Charge reactions on crystalline/amorphous lanthanum nickel oxide cocatalyst modified hematite photoanode
Authors: Yang Xiaogang , Li Lei , Yang Zhongzheng , Hu Jundie , Lei Yan , Li Pinjiang , Zheng Zhi
Published: July 2020

Understanding the charge reactions at the semiconductor/cocatalyst interface is of great interest for boosting photoelectrochemical water splitting since the charge transfer to water molecules is the sluggish one. Besides the dopants, porosity, or ion-penetration of the cocatalyst, the crystallinity of the cocatalyst may also influence the charge reactions at the interface. Herein, we prepared amorphous LaNiOx and crystalline La-doped NiO (c-LaNiOx) cocatalysts through photochemical decomposition and ion-exchange of Ni(OH)2 precipitation, respectively. Both lanthanum nickel oxides (LaNiOx) showed considerable improvement of hematite photoanodes. By using electrochemical impedance measurements, we confirmed that the catalyst could store photogenerated charges with reduced transfer resistance and passivate the surface state, resulting in the overall charge transfer rate enhancement. This study may lead to a chance to uncover the kinetic bottleneck with an efficient cocatalyst in well-controlled crystallinity in the future.
Thermal transport in phase-stabilized lithium zirconate phosphates
Authors: Yazdani Sajad , Kashfi-Sadabad Raana , Morales-Acosta Mayra Daniela , Montaño Raul David , Vu Tuoc Ngoc , Tran Huan Doan , Zhou Menghan , Liu Yufei , He Jian , Thompson Pettes Michael
Published: July 2020

The thermal properties of yttrium-stabilized lithium zirconate phosphate [LZP: Li1+x+yYxZr2−x(PO4)3 with x = 0.15, −0.2 ≤ y ≤ 0.4 and with x = 0.0, y = 0.0] are presented over a wide temperature range from 30 to 973 K, elucidating the interplay between structural phase transformations and thermal properties in a solid state superionic conducting material. At room temperature, the thermal conductivity decreases by more than 75% as the stoichiometry is changed from lithium deficient to excess and increases with increasing temperature, indicative of defect-mediated transport in the spark plasma sintered materials. The phase transformations and their stabilities are examined by x-ray diffraction and differential scanning calorimetry and indicate that the Y3+ substitution of Zr4+ is effective in stabilizing the ionically conductive rhombohedral phase over the entire temperature range measured, the mechanism of which is found through ab initio theoretical calculations. These insights into thermal transport of LZP superionic conductors are valuable as they may be generally applicable for predicting material stability and thermal management in the ceramic electrolyte of future all-solid-state-battery devices.
Forecasting the daily and cumulative number of cases for the COVID-19 pandemic in India
Authors: Khajanchi Subhas , Sarkar Kankan
Published: July 2020

The ongoing novel coronavirus epidemic was announced a pandemic by the World Health Organization on March 11, 2020, and the Government of India declared a nationwide lockdown on March 25, 2020 to prevent community transmission of the coronavirus disease (COVID)-19. Due to the absence of specific antivirals or vaccine, mathematical modeling plays an important role in better understanding the disease dynamics and in designing strategies to control the rapidly spreading infectious disease. In our study, we developed a new compartmental model that explains the transmission dynamics of COVID-19. We calibrated our proposed model with daily COVID-19 data for four Indian states, namely, Jharkhand, Gujarat, Andhra Pradesh, and Chandigarh. We study the qualitative properties of the model, including feasible equilibria and their stability with respect to the basic reproduction number R0. The disease-free equilibrium becomes stable and the endemic equilibrium becomes unstable when the recovery rate of infected individuals increases, but if the disease transmission rate remains higher, then the endemic equilibrium always remains stable. For the estimated model parameters, R0>1 for all four states, which suggests the significant outbreak of COVID-19. Short-time prediction shows the increasing trend of daily and cumulative cases of COVID-19 for the four states of India.
Chiral BINAPO Induced Circularly Polarized Luminescence in a Triple-Stranded Eu2L3(BINAPO)2 Helicate
Authors: Bi Shuang , Zhou Yanyan , Yao Yuan , Cheng Zhenyu , Gao Ting , Yan Pengfei , Li Hongfeng
Published: July 2020

Chiral lanthanide helicates with circularly polarized luminescence (CPL) properties have found potential application in bioanalyses and chirality sensing. However, the preparation of the enantiopure helicates through a coordination-directed self-assembly strategy is challenging due to the greatly labile coordination geometries of lanthanide ions. Herein, a pair of enantiopure triple-stranded EuIII helicates [(Eu2L3)(R/S-BINAPO)2] are assembled by three achiral C2-symmeric bis-β-diketones (4,4′-bis(4,4,4-trifluoro-1,3-dioxobutyl)(phenoxyl)-1,1′-biphenyl, L) helically twisting around two EuIII ions, and two chiral R/S-bis(diphenylphosphoryl)-1,1′-binaphthyl (R/S-BINAPO) as ancillary ligands. Electrospray ionization–mass spectrometry, NMR, and circular dichroism (CD) spectra confirm the formation of a pair of enantiopure chiral topological helicates (Eu2L3)(R-BINAPO)2 and (Eu2L3)(S-BINAPO)2. As expected, the helicates present strong CPL with the |glum| up to 0.09, and the higher luminescent quantum yields (QYs) of up to 51%.
Acquiring the polysemous adverb HAI in Chinese by English-speaking, Japanese-speaking, and Korean-speaking CSL learners
Authors: Hsieh Miao-Ling , Wang Yu-Fang
Published: July 2020

Using corpus analysis and error analysis, this study investigates English-speaking, Japanese-speaking, and Korean-speaking Chinese learners’ acquisition of various meanings ofhaiin Mandarin Chinese, including its temporal meaning ‘still, yet’ as well as its abundant atemporal meanings involving addition, comparison and counter-expectation. We found a preponderance of misselection errors across the three groups of learners. The next most common error type for the Japanese-speaking and Korean-speaking learners was omission, while omission and over-inclusion were equally challenging for the English-speaking learners. Further analysis of errors in misselection shows that many learners failed to distinguish the temporalhaifrom the atemporalhaishirequired in a concessive sentence for the counter-expectation meaning.
Morphological generalization of Hebrew verb classes
Authors: Farhy Yael
Published: July 2020

The present work investigated how morphological generalization, namely the way speakers extend their knowledge to
novel complex words, is influenced by sources of variability in language and speaker properties. For this purpose, the study
focused on a Semitic language (Hebrew), characterized by unique non-concatenative morphology, and native (L1) as well as
non-native (L2) speakers. Two elicited production tasks tested what information sources speakers employ in verbal inflectional
class generalization, i.e., in forming complex novel verbs. Phonological similarity was tested in Experiment 1 and argument structure in Experiment 2. The analysis focused on the
two most common Hebrew inflectional classes, Paal and Piel, which also constituted the vast
majority of responses in the two tasks. Unlike the commonly found outcomes in Romance inflectional class generalization, the
results yielded, solely for Piel, a graded phonological similarity effect and a robust argument structure effect, i.e., more Piel
responses in a direct object context than without. The L2 pattern partially differed from the L1: (i) argument structure effect
for L2 speakers was weaker, and (ii) L2 speakers produced more Paal than Piel responses. The results are discussed within the
framework of rule-based and input-based accounts.
Variability and its limits in bilingual word recognition
Authors: Clahsen Harald , Jessen Anna
Published: July 2020

This study examines the processing of morphologically complex words focusing on how morphological (in addition to
orthographic and semantic) factors affect bilingual word recognition. We report findings from a large experimental study with groups of
bilingual (Turkish/German) speakers using the visual masked-priming technique. We found morphologically mediated effects on the response
speed and the inter-individual variability within the bilingual participant group. We conclude that the grammar (qua morphological parsing)
not only enhances speed of processing in bilingual language processing but also yields more uniform performance and thereby constrains
variability within a group of otherwise heterogeneous individuals.
Surveying views of metaphor vs. literal language in psychotherapy
Authors: Tay Dennis
Published: July 2020

Five key therapeutic functions of metaphors are often discussed by psychotherapists. They (i) help clients express
emotions and experiences, (ii) help therapists and clients explain difficult concepts, (iii) introduce new frames of reference,
(iv) help work through client resistance, and (v) build a collaborative relationship between therapists and clients. Research on
how these functions are enacted in psychotherapy talk tends to assume that they are indeed perceived as such by clients, and that
metaphorical language is preferred to comparable literal language in performing them. This paper reports a survey study
(N = 84) to critically interrogate these assumptions. Participants read two constructed therapy dialogues,
controlled and counterbalanced for presentation sequence, where therapist and client discuss an issue using metaphorical and
literal language respectively. Each dialogue is followed by a 15-item questionnaire to rate how well the presumed functions were
performed (e.g. the therapist and client can work effectively together, the therapist is able to explain difficult
concepts). A combined Confirmatory (CFA) and Exploratory Factor Analysis (EFA) suggests that, instead of the five
distinct functions proposed in the literature, participants discerned three functions which reflect a more holistic view of what
metaphors can do. A second EFA conducted on literal responses yielded only two factors. This contrast in factor structure further
suggests that (i) literal language is less functionally nuanced, and (ii) metaphors are not simply perceived as an ‘add-on’ to
literal language, but are evaluated across an extended narrative in fundamentally different ways. Within-subjects metaphor vs.
literal ratings of the items under the emergent three-factor structure were then compared. Metaphor ratings were significantly
higher in all factors (p < 0.01), suggesting that metaphorical language is indeed perceived as more effective
than literal language when discussing clients’ issues. Implications, limitations, and future directions are discussed.
Design of retractile fins actuator based on hollow piezoelectric motor
Authors: Liu Jilei , Chen Chao
Published: July 2020

In the initial stage of the exterior ballistic, the centroid of the simple guided rocket will change with the fuel consumption of rocket engine, so the flight stability in the initial stage and the manoeuvrability in the whole trajectory correction process must to be comprehensively considered. For this challenge, in this paper, a specific actuator and aerodynamic configuration based on the integration of retractile fins structure and rotor of hollow piezoelectric motor is proposed. And the research on the structure of the actuator and the scheme of the retractile mechanism are carried out. The wind-induced rolling moment of the actuator under different flight conditions (angle of attack, Mach number) is simulated and analyzed by numerical computation method, and the load characteristics of the piezoelectric motor of the actuator is analyzed and tested. The results show that when the flight speed is 0.8 Ma, 1.0 Ma, the angle of attack is 0∼6°, the maximum induced rolling moment of the actuator is 0.30 N.m, and the load speed of the piezoelectric motor is 25r/min when the excitation voltage is 450V and the excitation frequency is 40.2kHz, which can meet the requirements of the projectile flying environment.
Several methods for improving the accuracy of Rockwell hardness testing
Authors: Yao Ch Ch , Wang M L , Ruan Y Y , Lv X M , Wang J L , Ge J M , Jiao H W
Published: July 2020

In order to reduce the testing errors in Rockwell hardness of metal specimens and improve the accuracy of hardness testing, several methods had been tried out and examined based on GB/T 230 and other relevant inspection specifications, firstly, correct the hardness of testing pieces directly by using the hardness reference blocks to calibrate the hardness tester; secondly, correct the hardness of testing pieces by linear calculation of the errors in different hardness values to calibrate the hardness tester; for a great deal of testing pieces, check the hardness twice and the second time in a reverse order. The result shows that the applied methods are effective to further improve the accuracy of Rockwell hardness testing.
The effect of cooling method on damping capacity of Fe-16Cr-2.5Mo alloy
Authors: Zhang C , Guo J B , Wang C , Hasi G W , Man P , Guo P F , Lin G Q
Published: July 2020

Damping capacity and magnetic domain structure of Fe-16Cr-2.5Mo alloy at different cooling rates have been investigated in this paper. DMA (Dynamic Mechanical Analyzer) was used to test the damping capacity. MFM (Magnetic Force Microscope) was used to observe the magnetic domain structures. The results indicated that furnace cooled alloy exhibited significantly higher damping capacity than water cooled alloy. For water cooled alloy, higher internal stress resulted in labyrinth domains’ formation and pinned the domain walls from moving, so the damping capacity was poor. However in the furnace cooled alloy, lamellar domains with larger size were responsible for higher damping capacity. In addition, higher initial permeability could be obtained to favor the movement of domain walls and contributed to higher damping capacity, due to the decrease of magnetocrystalline anisotropy.
Research on sealing ring complex curved surface grinding technology
Authors: Shan L , Qingtang W , Huan W , Dong X , Bo G , Xuejun D , Wei W
Published: July 2020

In order to solve the problem of the precision machining of the complex surface of the hydrodynamic seal ring, the precision grinding equipment is used to grind the complex surface. According to the surface structure of the sealing ring, a grinding mathematical model is established, adopting radial ring stacking method and trigonometric formulas to calculate the grinding wheel center movement trace during precision spot grinding. It can provide a strict theoretical basis for the next ultra-precision grinding experiment. According to the movement track, the numerical control program is compiled, and the grinding test of the seal ring is carried out on the self-developed equipment. During the grinding process, the workpiece and the grinding wheel run smoothly. The seal ring test sample meeting the requirements of the face shape is processed, which solves the technical problem of processing the complex face shape. It provides reliable technical support for the subsequent high-precision processing and universal application of the seal ring.
Optimization design of spinning process of titanium alloy cylinder based on numerical simulation technology
Authors: Guan R Y , Xu H Q , Tao H , Guo Y M , Lu B , Zheng H W
Published: July 2020

Power spinning is a very complicated plastic forming process, and its processing quality involves many and complicated process parameters. The simufact.forming software is used to simulate the power spinning of the titanium alloy cylindrical parts. The effects of technological parameters such as attacking angle, roller nose radius, feed rate, spinning temperature, etc. on cylindrical parts accuracy, spinning force, and stress-strain distribution are systematically studied. The causes of spinning process defects are analyzed, and the sensitivity of process parameters that affected spinning quality is ranked. Through orthogonal test analysis, it is determined that a set of optimal process parameters for the titanium alloy cylindrical part spinning process: attacking angle is attacking angle 20°, the roller nose radius is 10mm, feed rate is 1mm/r, spinning temperature is 850°C. The spinning process of titanium alloy cylindrical parts is initially formed, which lays the foundation for the subsequent spinning process tests of titanium alloy cylindrical parts.
Study on the solid propellant burning rate enhanced by plasma in the closed bomb
Authors: Ni Yanjie , Jin Yong , Wan Gang , Yang Chunxia , Li Baoming
Published: July 2020

A closed bomb experimental system is employed to discuss the ignition and combustion characteristics of the solid propellant with the capillary plasma generator (CPG). 4/7 high-nitrogen solid propellant, 5/7 high-graphite solid propellant and 5/7 low temperature sensitivity coated propellant are ignited in the closed bomb. Compared with the experimental results with the conventional ignition, the ignition delay time with the CPG is reduced and the burning process of the propellant is enhanced. The pressure changing rate is used to analyse the enhanced gas generation rate (EGGR) of the propellant with the plasma. Compared with the pressure changing rate with different igniters, the enhanced gas generation rate during electrical discharge (EGGRDED) is proved. When 4/7 high-nitrogen solid propellant and 5/7 low temperature sensitivity coated propellant are ignited in the closed bomb, the enhanced gas generation rate post electrical discharge (EGGRPED) appears. The EGGRPED is mainly influenced by the composition of the propellant. The influence of the electrical parameters of the CPG and the distance between the CPG and the solid propellant is studied by the closed bomb experiments. The ignition delay time and the burning time of the propellant reduce with the increasing of the electric power or the decreasing of the distance between the CPG and the propellant. Depending on the pressure changing rate in the closed bomb experiments, the EGGRDED increases with the increasing of the electric power or the decreasing of the distance between the CPG and the propellant, while the EGGRPED is not influenced by the electric power or the distance between the CPG and the propellant.
Internal ballistic simulation and optimum design of gas-fired rodless cylinder ejection device
Authors: Wang X Q , Ma D W , Ren J , Yao L , Hong J L Z , Wang Z L
Published: July 2020

A kind of gas-fired rodless cylinder ejection device which is stoke and weight controlled and suitable for mobile launch was designed. The leakage test of the ejection device is carried out based on the principle prototype of rodless cylinder ejection device and the empirical formula between leakage rate and pressure and travel length was fitted. The mathematical model of gas-fired rodless cylinder ejector internal ballistic with considering the leakage rate is established based on the assumption of zero-dimensional internal ballistic. When comparing the results of internal ballistics considering and not considering the leakage rate, it can be seen that the influence of leakage rate on the results of internal ballistics can not be ignored. The internal ballistic model which coupled the leakage rate is optimized, taking the shortest design stroke and smallest ejection stability index as design target and the parameters of the grain are used as design variables. The results show that after the optimization, the mass flow rate of gas at the end of ejection is increased by 19%, the stroke required for piston speed reaching the design target is shortened by 13.1%, and the launch stability index is increased by 10.7%.
Synthesis, crystal structure and properties of aminourea salt of 4,8-dihydrodifurazano[3,4-b,e] pyrazine
Authors: Duan B H , Liu N , Wang B Z , Lu X M
Published: July 2020

To reduce the acidity defect of 4,8-dihydrodifurazano[3,4-b,e]pyrazine(DFP), a new energetic ionic compound aminourea salt of 4,8-dihydrodifurazano[3,4-b,e]pyrazine (DSDFP) was designed and synthesized with a yield of 72.6%. The structure of target compound was characterized by means of NMR (1H and 13C), IR spectra, elemental analysis and single crystal X-ray diffraction. The thermal stability was tested by DSC and TG method and DSDFP shows good thermal stability with exothermic decomposition peaks in the range of 267.3 °C ∼ 282.3 °C. The impact sensitivity was measured using BAM standard method and the detonation performance was computed by Kamlet-Jacobs equations. Results show that DSDFP exhibits excellent impact sensitivity of greater than 40 J and desirable detonation performance with detonation velocity of 7891 m/s and detonation pressure of 27.1 GPa. These results highlight its great promise of potential candidates for high-performance energetic salt.
A rigid elliptical cross-sectional projectile with different geometrical characteristics penetration into concrete target
Authors: Dai X H , Wang K H , Duan J , Li M R , Qian B W , Zhou G
Published: July 2020

Elliptical cross-sectional projectiles have recently attracted attention because they fit the flattened shape of earth-penetrating weapons. This study aims to investigate a rigid elliptical cross-sectional projectile with different geometrical characteristics penetration into the semi-infinite concrete targets by implementing a theoretical method. The general geometric models of four types of elliptical cross-sectional projectiles are introduced; closed-form penetration equations are then derived based on the dynamic cavity-expansion theory. Furthermore, the present models are validated by comparing the predicted penetration depths with the predictions obtained using the semi-empirical formulae and test data; the maximum deviation from the test data is 15.8%. In addition, the deceleration, velocity, and displacement of the projectiles during the penetration process are obtained based on the present models, and the penetration performance of the four types of elliptical cross-sectional projectiles is discussed by comparing the penetration depths. The conical-nose elliptical cross-sectional projectile exhibits the best penetration performance than the other three types if the nose length is sufficiently large, and the ogive-nose elliptical cross-sectional projectile gradually exhibits its penetration performance advantage with the increase in the nose length.
Bionic stab-resistant body armor based on triangular pyramid structure
Authors: Guo Yaxin , Yuan Mengqi , Qian Xinming
Published: July 2020

A stab-resistant substrate was designed and realized with a triangular pyramidal structure inspired by the biological armor model in the nature. Through numerical simulation and experimental testing of a knife impacting a substrate, the stab-resistant behavior and dynamic response mechanisms were studied. It was found the stab-resistant performance on the triangular pyramidal substrate was better than the flat plate. The surface of the triangular pyramidal substrate effectively avoided the normal force generated from impacting due to a significant dispersion effect on the tilted pyramid structure. The substrate tended to be inclined and the stress of the backing material was inhomogeneous, absorbing more energy. Much of the deformation energy and others, such as heat and light energy, were caused due to intensive collision between the knife and the substrate, all of which leading to a rapid drop of the knife kinetic energy. The substrate with higher tilted angle led to improved energy dispersion, as well as larger area density. The optimal design parameters were achieved with the knife impacting tests, of which the tilted angle was 22.5° and thickness 1.2 mm. The stab-resistant layer made of the titanium alloy through compression molding consisted of the optimal design parameters. A new riveting method was used to perform the total layer, which passed the GA 68-2008 National Standard. The overall areal density of the stab-resistant layer was 5.85 kg/m2, which was 45% lower than a commonly used stab-resistant layer. The method provided may enlighten the future design and manufacturing of stab-resistant clothing.

The full version of this abstract will appear in Defence Technology in 2020.
Experimental study on impact-induced initiation thresholds of al/ptfe/w composite
Authors: Xu T , He Y , He Y , Wang Ch T , Yang X L
Published: July 2020

Al/PTFE/W is a typical kind of reactive material, which has a variety of potential applications in the future. Impact experiments were conducted with a gas gun and a steel target to investigate the impact-induced initiation thresholds of Al/PTFE/W (18.55 wt.%/51.45 wt.%/30 wt.%) rods. The Al/PTFE/W rods were prepared by using the cold press and hot sinter method. A high-speed camera was used to observe the time sequence of events and to measure the speed of the rods by the grids on the background board. At low velocity, no initiation occurred and the rods only appeared upsetting. Above an initiation threshold of around 127m/s, extensive chemical reaction with strong flare was observed after impact. There was a time interval for the flare after impact, and this time interval decreased with increasing of impact velocity, from 138μs(127.4m/s) to 68μs (235m/s). Several experiments were performed for PTFE and Al/PTFE (26.5 wt.%/73.5 wt.%) rods for comparison with the Al/PTFE/W rods. The effect of impact velocity and composition on the impact-induced reaction of Al/PTFE/W was discussed.
Experimental preparation and property analysis of rare earth modified impact resistant steel
Authors: Zhang M Y , Geng W Y , Gao P , Gao X J , Zhao H R , Wang X F
Published: July 2020

To further improve the comprehensive performance of existing impact-resistant steel, rare-earth-modified steel samples were experimentally prepared and their performance was analyzed. Different amounts of mixed rare earths were added into the 30MnCrNiMo impact-resistant steel, followed by vacuum smelting, forging, and rolling to prepare the steel plate. The effects of rare earths on the phase transformation critical points, high-temperature deformation behavior, microstructure, and mechanical properties were studied. The results show that rare earths can play a purifying role in the test steel. The Ac1-Ac3 phase transition temperatures were increased, and those of the Bs-Bf phase transition were decreased significantly. When compressed at 1000 °C, the deformation resistance of the test steel with rare earth became higher. Thus, the added rare earths improve the microstructural morphology and inclusions in the steel, as well as the comprehensive mechanical properties.
Numerical simulation of the asymmetric bullet penetrating the perforated steel plate
Authors: Li J Sh , Li N , Wang J , Tao Zh G
Published: July 2020

In this study, the perforated steel plates were demonstrated to exhibit high efficiency in protecting against small-caliber armor-piercing projectiles. The oblique hipped armor plates combined with the perforated steel plates acted as an armored vehicle exhaust vent protect against 7.62mm bullet. To enhance the efficiency of the vehicle exhaust, the numerical model was built, consisting of the hipped armor plate, the perforated steel plate and the bullet core. By performing a simple test, the efficiency of the model was verified. After the bullet penetrates the hipped armor plate, the shape of its core changed to be asymmetric. The sizes of the perforated steel plate were preliminarily designed in accordance with the statistical results of numerical simulation. Effects of the perforated steel thickness and the impacting positions on the residual bullet were ascertained. The results of this study were conducive to designing exhaust vents.
Dynamic Necking of a Near α Titanium alloy at High Strain Rates: Experiments and Modelling
Authors: Zhang Longhui , Pellegrino Antonio , Petrinic Nik
Published: July 2020

The tensile behaviour of near α Ti3Al2.5V alloy, conceived for applications in aerospace and automotive engineering, is characterized from quasi-static to high strain rates. The material presents noticeable strain rate sensitivity. The dynamic true strain rate in the necking cross-section reaches values up to one order of magnitude higher than the nominal strain rate. It is also observed that beyond necking the true stress-strain curves present limited rate dependence in the dynamic loading regime. The experimental results at various strain rates and temperatures are used to determine the material parameters of a suitable constitutive model for finite element simulations of the dynamic tensile tests. The model predicts the experimentally macroscopic force-time response, true stress-strain response and effective strain rate evolution with good agreement.
The energy distribution characteristics of a cylindrical cased charge with two end caps
Authors: Liao W , Jiang J W , Men J B , Wang S Y , Li M
Published: July 2020

The energy distribution characteristics are the key parameters for analysing the energy distribution of the cylindrical cased charge and improving the damage efficiency of the warhead. To investigate the initial velocities from a cylindrical cased charge detonated at the point on the axis, the flash X-ray radiography system was used to test the velocities of the end caps, and the influence of the axial position of the detonation point was further studied by simulation. The experimental results show that when the thickness of the end cap is equal to that of the casing and the ratio of length to diameter is 3, the velocity of the front end cap is 0.53 times that of the rear end cap. The simulation results show that the initial velocities and energy distribution are affected by the height from the detonation point to the end, and the conversion efficiency of the explosive energy can be increased by adjusting the detonation height and the charge length.
Air blast pressure characteristics of moving charge
Authors: Xu Q P , Su J J , Li Z R , Liu Y , Jiang H Y , Huang F L
Published: July 2020

Air blast pressure between moving charge and static charge are obviously different, however, due to the limitation of testing means, most blast or impact experiments were conducted under static state, which bring risks to evaluate safety of the target structures. In this paper, based on the finite element software and theoretical analysis, we investigated characteristics of the air blast pressure of moving charge. By introduced the toroidal distribution coefficient and radial distribution coefficient, a calculation model, used to calculate the overpressure with scope of relative distance at range of 0.4∼2 m/kg1/3 around blast center was established. The model could quickly calculate overpressure distribution around the blast center. Furthermore, isobars lines of moving charge were obtained by solving the model, some other phenomena were also analyzed.
Study on the shock wave effect and engineering algorithm in the tunnel after structure damage under different explosion conditions
Authors: He X , Sun G J , Liu F , Ren X J , Wang X , Chen L
Published: July 2020

In this paper, according to dimensional analysis, the dimensionless function of the intensity of the air shock wave overpressure of the explosion in structure leaking into a tunnel is established. Forty-eight experiments were carried out focusing on some influencing factors such as explosive charge, explosive depth, ratio of reinforcement, concrete matrix strength, and existence of the structure, revealing the influence laws of explosive charge, explosive height, ratio of reinforcement and concrete matrix strength on the overpressure intensity of air shock wave. Then, engineering calculation methods for leak shock wave effect are obtained, which include the overpressure distribution of shock wave in explosive tunnel in structure, equivalent coefficient of explosive charge compared with explosion in tunnel as well as the reduction factor of shock wave with or without structure.
Experimental study of hot pressed sintered modified materials
Authors: Tang X Z , Wang Z J , Yi JY , Han Y Y , Wang Y F , Jia Z J
Published: July 2020

The PTFE/Cu composite powder was selected as the experimental raw material, and the modified material PTFE/Cu with dense structure was prepared by hot pressing sintering process. The morphology of the product before and after the test was compared and observed by SEM. The effect of different material ratios on the densification results of the powder was studied, and the difference between molding and hot pressing sintering was analyzed. The results show that hot-pressed sintering can produce modified PTFE/Cu with a density of up to 99.9%, which is higher than that obtained by molding under the same pressure. The SEM image shows that, unlike the molding, hot-pressing sintering makes the crystal grains of the two materials exist independently in the modified polymer, and makes the powder crystal grains gradually perpendicular to the hot pressing direction.
Research on damage of typical water-containing composite structure under different types of charge
Authors: Wang C L , Zhou G , Ma K , Li M , Chen C L , Feng N , Ke M
Published: July 2020

The damage of the water-containing composite structure subjected to underwater explosion is caused by multiple damage elements, such as charge structures, water-containing composite structure, experimental mode and so on. The underwater explosion experiments and the numerical calculations have been performed to study the damage of water-containing composite structure under the different kinds of charge underwater explosion and under different experimental mode, The result shows that the damage of structure under the action of shaped charge is more serious than that of blasting charge in the case of the same charge equivalent. The combined action of shaped penetrator and shock wave can cause perforation and plastic deformation of the rear plate and target of the water-containing composite structure e. The tearing hole on the front board is 2∼3 times of the shaped charge diameter. The damage of the rear plate is the penetration of the penetrator which is about 1/3 times of the shaped charge diameter. When shaped charge explodes in air or underwater, the plastic deformation of the rear plate is very different.
Research on the SDT technology based on a two-stage structure
Authors: Xian M C , Meng Y G , Xie J Y , Wu L Z , Shen R Q
Published: July 2020

The SDT (shock to detonation transition) technology based on a two-stage structure has been researched. The models of mass block’s velocity and shock-wave convergence produced from mass block impacting charge have been built, which reveal the mechanism of detonation caused by the impact. The influence characteristics of some parameters on the shock-wave convergence have been obtained. According to the analysis, the related parameters have been decided and the grope experiments were carried out. The result shows that the detonator employing the SDT structure, whose igniting time is less than 2ms, has good environmental adaptability. The technique of reliable and fast detonation of high explosive without using sensitive explosive has been realized.
Mechanical properties of steel gun barrel processed by cold radial forging with stepped mandrel under different forgingratios
Authors: Yang Yuzhao , Zhang Xiaoyun , Fan Lixia , Xu Cheng
Published: July 2020

Mechanical properties of 30SiMn2MoVA steel gun barrel processed by cold radial forging with stepped mandrel under the different forging ratios were investigated in the present work. This work mainly reported the axial and circumferential mechanical properties of forged gun barrel before and after annealing. The axial and circumferential mechanical properties were measured by tensile test and bulging test, respectively. The results suggested that the strength was enhanced and elongation was decreased by forging which was caused by cold work hardening. After annealing, the anisotropy of elongation was observed. The circumferential elongation was weaker than the axial. With the increasing of forging ratios, strength anisotropy was exacerbated gradually. The circumferential strength was inferior to the axial. Besides, there were axial penetrating cracks in the failure state of circumferential bulging test specimens. Through the electron microscopic examination, the axial micro cracks and wrinkles in the inner wall of the forged tubes were observed. It showed that the cold radial forging with stepped mandrel may result in the defect in the inner surface of the gun barrel which should be paid attention.
Neural network based adaptive rise control of tank gun systems
Authors: Ma X , Deng W X , Yuan Sh S , Yao J Y , Yang G L
Published: July 2020

With the development of the all-electric fourth-generation tank, higher requirements have been put forward for the accuracy and response speed of tank gun control and the traditional tank gun system modeling methods and control strategies failed to meet the requirements. For this reason, a neural network based adaptive robust integral of the error sign (ARISE) control for tank gun system is proposed considering two-axis dynamic coupling and nonlinear friction characteristics. Firstly, a two-axis coupling nonlinear dynamic model of the tank gun system is established and a continuous static friction model is used to characterize the nonlinear friction characteristics of the system. Then, an adaptive law is designed based on the desired position instruction to realize the online update of unknown system parameters. In addition, the neural network is used to compensate other unmodeled dynamic errors and the influence of neural network approximation error is suppressed by the nonlinear integral robust control term. The stability analysis results show that the proposed neural network based adaptive robust integral of the sign of the error control strategy can obtain excellent asymptotic tracking performance, and the simulation results verify its effectiveness.
Discrete Element Simulation of Durability for Bionic Wheels of Mars Rover
Authors: Lin Y C , Yan Y P , Yuan B F , Liu Y F , Zou M
Published: July 2020

Four kinds of bionic surfaces (convex, scale-like, ribbed and concave shape) for Mars rover wheels were designed to improve wheel durability. A discrete element wheel-soil simulation system was developed, and three-dimensional discrete element analysis and soil bin tests were conducted. The results show that the masses of the convex and scale-like forms increased by 5.4% and 17%, respectively, and that the tangential cumulative forces decreased by about 40% and 70%, respectively. The wear mass decreased by 53% and 47%, respectively, compared with a prototypical wheel. The simulation shows that the durability increased significantly. The average tangential cumulative forces of the concave and ribbed shapes increased by more than 50%, and the wear mass decreased by 35% and 32%, respectively, compared with a prototypical wheel. The simulation shows that the results were not definitive. The analysis shows that the durability of the wheels can be improved via bionic optimization method. These results therefore provide a basis and reference for the design and optimization of the Mars rover’s wheel surface.
The fuzzy adaptive PID control of brushless DC motor
Authors: Yin H Q , Yi W J , Li C C , Wang K J , Wu J T
Published: July 2020

Brushless direct current motor (BLDCM) is a complicated system with multivariable, nonlinear and strong coupled. The present work devotes to design a fuzzy adaptive PID algorithm based on the speed loop so that it could crack the traditional PID problems which include bad parameter setting, poor adaptability, imprecise control and weak anti-interference so on. In this paper, the mathematical model and operating characteristics of BLDCM are analyzed. Then, the simulation platform is built by MATLAB/Simulink. Finally, the control effects of PI, PID and fuzzy adaptive PID are compared and analyzed. The results indicate that the fuzzy adaptive PID is better robustness, faster response, smaller overshoot and more stable operation than others.
Real-time instance-aware semantic mapping
Authors: Xu X C , Liu L l , Xiong R , Jiang L
Published: July 2020

The semantic information helps robots to understand its surroundings like human beings and enables robots to achieve human-robot interaction. In recent years, there have been many interests in semantic mapping. Numerous approaches manage to build a semantic map and achieve good accuracy, but the existing mapping methods which create the metric semantic map ignore the subsequent applications of the semantic map. However, the metric map with the simple semantic class label has no direct benefit to localization. In this paper, we propose an approach to construct an object-centric map with promising applications. Employing the traditional metric and deep learning methods, we can extract objects from the environment and along with semantics. This object representation of the semantic map can be useful in other applications of robots, our local map and global map framework can be useful for navigation. At last, we report on the quality and speed of our object-centric mapping method.
Effects of heat treatment and deformation on tensile strength and conductivity of Cu-Cr-Zr alloy doped with lanthanum and yttrium
Authors: Ren X Y , Gao P , Zheng H W , Yu W J , Wang S L , Lei Y , Yang Ch X , Lan L , Li YF
Published: July 2020

Copper chromium zirconium alloy Cu-0.684Cr-0.077Zr-0.012La-0.020Y mixed with lanthanum and yttrium, after treatment at different solid temperatures, through metallographic microstructure and energy spectrum analysis, determine the alloy solid solution temperature is 920°C. After solution treatment at 920°C, the alloy underwent 40%, 60% and 80% deformation after quenching and water cooling, the results showed that after 60% deformation, 520°C and 0.5 hour aging treatment, the alloy could obtain better comprehensive performance, with tensile strength of 527MPa and electrical conductivity of 73%IACS.
Experimental study on fabrication and impact characteristics of PTFE/Al/W reactive materials with different molding pressures
Authors: Geng B , He S , Guo H , Cun H , Wang H , Ge C
Published: July 2020

Here we focus on the impact characteristics of polytetrafluoroethylene/aluminum/tu-ngsten (PTFE/Al/W) reactive materials under various molding pressures. Reactive materials of the density of 3.0 g/cm3 were fabricated via pressing and sintering processes. Drop weight tests were carried out to study impact characteristics of the reactive materials. Experiment shows that, critical forming pressure and compaction pressure are approximately 5MPa and 100MPa, separately, and meanwhile, the sintering cycle could enhance the strength of the material pressed under the critical forming pressure. Furthermore, reactive materials show strain rate effect on impact characteristics, and the increase of mounding pressure attributes to the transition from inertness to sensitivity of the material. Within the molding pressure range of 15MPa, impact sensitivity of the material increases exceedingly, whereas, the impact sensitivity remains relatively stable when the molding pressure ranging from 15 MPa to 100 MPa. Phenomenologically, with the increase of the molding pressure, the drop impact induced initiation flame transits from weak and unsustainable to intense and continuous. From the point of initiation mechanism, low molding pressure introduced high porosity plays negative role against the formation and growth of the hot spots in the microstructure of the material, which was demonstrated by the experiments. The conclusion drawn from this research reveals that a well pressed condition would be beneficial for increasing the impact sensitivities of low density reactive materials.