bluuebunny/crossref_metadata_2025 huggingface dataset:
A binary quadratic function negative‐determination lemma and its application to stability analysis of systems with two additive time‐varying delay components
Authors: Liu Meng , He Yong , Jiang Lin
Published: September 2021

This paper concentrates on the stability problem of systems with two additive time‐varying delay components. For the construction of Lyapunov–Krasovskii functional (LKF), in the case that the introduced augmented vector contains the double integral term of the state vector, a special form of the binary quadratic function with respect to two time‐varying delays has often been introduced into the derivative of the LKF. In order to determine the negative definiteness of such function, by making full use of the idea of partial differential, the convex/concave property and the slope characteristic of tangent lines of the binary quadratic function, a binary quadratic function negative‐determination lemma is proposed in the case of the pluses or minuses of quadratic coefficients are unknown. Then, the obtained stability criterion in the form of linear matrix inequality shows a greater advantage than the previous criteria since not only some advanced techniques are employed to treat some integral terms, but also the proposed lemma is employed to deal with quadratic terms in functional derivative. Finally, a typical example is given to verify the superiority of the derived criterion.
Coal gangue detection and recognition algorithm based on deformable convolution YOLOv3
Authors: Li De‐yong , Wang Guo‐fa , Zhang Yong , Wang Shuang
Published: September 2021

The intelligentisation of coal mines is the only approach to the high‐quality development of the coal industry. Detection, identification and sorting of coal gangue is an important part of the intelligentisation of coal mines. Focusing on various problems in coal gangue detecting and recognising algorithms, such as limited receptive field, slow convergence rate and low accuracy of small particle recognition, this paper proposes a coal gangue detection and recognition algorithm based on deformable convolution YOLOv3 (DCN‐YOLOv3). To improve the accuracy of anchor frame positioning and enhance the diversity of the dataset, the deformed convolution YOLOv3 network model is established based on the detection algorithm YOLOv3, using deformable convolution, multiple k‐means clustering results average method and data enhancement technology as means. The model was trained through the self‐designed dataset, and the algorithm's correctness and accuracy for coal gangue recognition under different size and illumination conditions are verified. The test results showed that the algorithm effectively detects and recognises coal gangue, improves the accuracy and efficiency of detecting and recognising small‐size coal and gangue and improves environmental robustness. Furthermore, compared with the traditional recognition algorithm, the network convergence speed of this algorithm is significantly improved, the mAP is increased to 99.45%, and the maximum FLOPs value is reduced by 61.4%. Accordingly, this research is considered to be of certain theoretical value and technical reference for identifying coal gangue.
Noise suppression in PD signal based on Prony time series energy spectrum
Authors: Wang Chang , Yu Chunxiao , Shu Qin , Zhang Dakun , He Yuhang
Published: September 2021

On‐line partial discharge (PD) monitoring is related to the safe and stable operation of power grid. However, the measured signal is inevitably affected by noise. Among a variety of noises, white noise is the most difficult to suppress and ubiquitous. It mainly determines the Cramer–Rao lower bound that cannot be crossed by all methods. This article proposes the Prony time‐series energy spectrum method to suppress white noise in a low signal‐to‐noise ratio environment. This method is divided into two parts: First, Prony time series energy spectrum is used to detect whether there is PD signals in the measured signal. Then, based on the least square method, the PD signal is estimated with the Prony model. In data analysis, this method can suppress ‐10dB white noise, while other methods have performed poorly or even failed under the same conditions. In general, this method has excellent anti‐noise performance compared to several other algorithms.
The effect of thermal conductivity on the outgassing and local gas dynamics from cometary nuclei
Authors: Pinzón-Rodríguez O. , Marschall R. , Gerig S.-B. , Herny C. , Wu J. S. , Thomas N.
Published: September 2021

Aims.The aim of this work is to investigate the parameters influencing the generation of the inner comae of a comet with a spherical nucleus and to model the gas activity distribution around its nuclei. Here, we investigate the influence of thermal conductivity combined with sub-surface H2O and CO2-ice sources on insolation-driven sublimation and the resulting gas flow field. In the process, we adopted some of the rotational and surface properties of the target of the Rosetta mission, comet 67P/Churyumov-Gerasimenko (67P/CG).

Methods.We used a simplified model of heat transport through the surface layer to establish sublimation rates from a H2O- and CO2-ice sub-surface into a vacuum. We then applied the 3D Direct Simulation Monte Carlo method to model the coma as a sublimation-driven flow. The free parameters of the model were used to test the range of effects arising from thermal inertia and the depth of the source on the gas outflow.

Results.Thermal inertia and the depth of the sublimation front can have a strong effect on the emission distribution of the flow at the surface. In models with a thermal inertia up to 80 TIU (thermal inertia units: J m−2K−1s−1∕2), the H2O distribution can be rotated about the rotation axis by about 20° relative to models with no thermal lag. For CO2, the maximum activity can be shifted towards the sunset terminator with activity going far into the nightside for cases with low thermal diffusivity. The presence of a small amount of CO2can reduce the presence of H2O by at least an order of magnitude on the nightside by blocking H2O flow. In addition, CO2can also decrease the speed of the mixed flow in the same region up to 200 m s−1, compared to cases with no CO2activity.

Conclusions.Even low values of the thermal inertia can substantially modify the gas flow field. Including CO2leads to strong variations in the local CO2/H2O density ratio between the dayside and nightside. CO2can dominate the gas composition above the nightside and can also act to modify the H2O flow field close to the terminator.
Constraining the radius and atmospheric properties of directly imaged exoplanets through multi-phase observations
Authors: Carrión-González Ó. , García Muñoz A. , Santos N. C. , Cabrera J. , Csizmadia Sz. , Rauer H.
Published: September 2021

Context. The theory of remote sensing shows that observing a planet at multiple phase angles (α) is a powerful strategy to characterize its atmosphere. Here, we study this observing strategy as applied to future disc-integrated direct imaging of exoplanets in reflected starlight.

Aims. We analyse how the information contained in reflected-starlight spectra of exoplanets depends on the phase angle and the potential of multi-phase measurements to better constrain the atmospheric properties and the planet radius (Rp).

Methods. We simulate spectra (500−900 nm) at α = 37°, 85°, and 123° with a spectral resolution of R ~ 125−225 and signal-to-noise ratio (S∕N) = 10, consistent with the expected capabilities of future direct-imaging space telescopes. Assuming a H2-He atmosphere, we use a seven-parameter model that includes the atmospheric methane abundance (fCH4), the optical properties of a cloud layer and Rp. All these parameters are assumed to be unknown a priori and are explored with a Markov chain Monte Carlo retrieval method.

Results. No single-phase observation can robustly identify whether the atmosphere has clouds or not. A single-phase observation at α = 123° and S∕N = 10 can constrain Rp with a maximum error of 35%, regardless of the cloud coverage. We find that combining small (37°) and large (123°) phase angles is a generally effective strategy to break multiple parameter degeneracies. This enables us to determine the presence or absence of a cloud and its main properties, fCH4 and Rp, with higher confidence in all the explored scenarios. Other strategies, such as doubling S∕N to 20 for a single-phase observation or combining small (37°) and moderate (85°) phase angles, fail to achieve this. We show that the improvements in multi-phase retrievals are associated with the shape of the scattering phase function of the cloud aerosols and that the improvement is more modest for isotropically scattering aerosols. We finally discuss that misidentifying the background gas in the retrievals of super-Earth observations leads to systematic underestimation of the absorbing gas abundance.

Conclusions. Exoplanets with wide ranges of observable phase angles should be prioritized for atmospheric characterization in reflected starlight.
The Calculation Method of Shielding Failure Trip Rate of UHV Transmission Lines in Mountainous Areas
Authors: Alanazi Hani Owaid S , Xiaoming Ma
Published: September 2021

Since the second industrial revolution, electric energy has always been the most important and indispensable clean energy in the international community. As a kind of transmission technology with small loss ratio and long transmission distance, UHV transmission is widely used and vigorously promoted in the world. However, UHV transmission lines are often assumed to be vulnerable to thunderstorm discharge in some harsh geographical environment. In order to improve the calculation accuracy of line shielding failure rate, an improved electrical geometric model is proposed to study the shielding failure characteristics of transmission lines under complex mountainous areas, and various typical characteristics including mountain tops, valleys, slopes, climbing, and crossing trenches are summarized.
Analysis and Prediction of Water Consumption in Nanjing—A Comparative Study Based on Stepwise Regression and Nonparametric Mode
Authors: Zhou Xu
Published: September 2021

Accurate prediction of urban water consumption is of great significance to the management and improvement of water supply system. In this thesis, through correlation analysis on 16 factors affecting total water consumption in Nanjing from 2005 to 2019, the factors among them that have more obvious influence are selected, and then they are fitted by stepwise linear regression model and nonparametric regression model respectively. By comparing the fitting results, it is found that nonparametric regression model has better prediction effect than stepwise regression model. The analysis results show that the prediction of urban water consumption is very important for the rational allocation of water resources.
Energy Reserves and Industrial Development in Northeast India
Authors: Liu Changwei
Published: September 2021

The northeast of India is rich have abundant natural resources and has superior energy reserves, but the economic development of the region is backward which is difficult to forming industrial effects. Based on the energy conditions and economic endowment of northeast of India, this paper examines the development dilemma of this region and analyzes the policies adopted by India to promote the economic and industrial development of the region, so that the local economic potential can be released, energy development can be enhanced, and the industrial layout can be more reasonable.
“Blockchain Plus Supply Chain Finance” Boosts Pharmaceutical Industry: A Case Study of Jixiangtian Blockchain Medical and Health Service Platform
Authors: Yan Kong , Yanna Wang
Published: September 2021

China’s pharmaceutical industry has enormous potential. With the launch of relevant state policies and the innovations being made on the financial front, the country’s medical industry has a closer tie with its financial institutions in the supply chain. On the other hand, the booming of supply chain finance provides excellent platforms for financial institutions, pharmaceutical companies and third-part logistics to interact with each other. Nevertheless, supply chain finance in a traditional sense is still facing many challenges. Taking Jixiangtian, a blockchain and medical service platform as an example, this paper illustrated the problems faced by the traditional pharmaceutical supply chain, and analyzed pharmaceutical supply chain platforms using blockchain technology to propose solutions to tackle the financial challenges faced by traditional supply chains.
Overview of Fusion Technology in Food Safety Big Data
Authors: Wang Yajie , Yang Bing , Yang Hong , Hao Miao , Zhang Chengmei , Tao Heng
Published: September 2021

Large amounts of organised and unstructured data from various sources and origins are increasingly being handled by technology. Big data is a term used to describe these technologies, which open up new fields of research and applications that will have an expanding impact on all aspects of our society. Because of its potential to turn massive amounts of data into insights for informed business and operational choices, big data has found uses in a variety of industries. In the food industry, advanced techniques have been used for providing Food Safety. We present an overview of how and to what extent big data is being used in the food safety domain in this study. Mobile phones as food safety detecting devices and the use of social media as an early warning system for food safety issues are just two examples of the new advancements made feasible by big data.
Research Status and Prospect of Matcha Blending Based on Intelligent Algorithm
Authors: Yang Bing , Yu Jie , Chen Kai , Yang Xin , Xin Fangjian , Qin Meiyuan
Published: September 2021

Matcha green tea, a Japanese specialty, is commonly thought to have health advantages. Tea quality will improve taste which results in increased sales. Polypeptide, methionine acids (mostly additive), and cappuccino all contribute to the beverage’s phytonutrients qualities. Infusions prepared from Traditional Matcha blending techniquesR from the initial and subsequent harvests and Daily Matcha from the second and third harvests were tested for phytonutrients potential and gratified of chemicals with an phytonutrients effect additive at different temperatures and other approach is the fundamental fusion model is built using a regularity method with the attempt’s lowest cost as the impulsion aim, total polypeptide gratified including flavanones in recent research. This study will give overview of recent advancements and future aspects of Matcha blending.
The impact of e-commerce platform merchants’ reputation on consumer decision making
Authors: Tang Genghua , Wu Lishan , Guo Lei
Published: September 2021

By crawling Meituan take-out merchant data, this paper studies the influence of e-commerce platform merchants’ reputation on consumer decision making. The empirical results show that the merchant reputation based on the overall score of merchants has a significant impact on consumers’ purchase decision and then affects the monthly sales volume of merchants. At the same time, brand merchants have higher monthly sales than ordinary merchants, and a series of food safety guarantee measures such as food safety insurance purchase and food material publicity also significantly affect monthly sales. In addition, the overall score of platform merchants has a marginal diminishing effect on monthly sales. Based on the empirical research conclusions, this paper also puts forward relevant countermeasures and suggestions for Meituan platform merchants and government regulatory authorities.
Internal Control, Manager ability and Enterprise performance – Empirical Analysis Based on DEA data Envelopment Model
Authors: Huijiao Duan
Published: September 2021

Internal control has become an important part of corporate governance. This paper selects all Chinese A-share listed companies from 2015 to 2019 as samples to study the relationship between internal control and corporate performance, and to investigate the effect of managers’ ability on the process of internal control affecting corporate performance. It is found that there is a significant negative correlation between internal control defects and enterprise performance, which indicates that there are significant internal control defects, which will restrain the enterprise’s financial performance; the effectiveness of internal control operation is significantly positively correlated with enterprise performance, which shows that the operation of effective internal control helps to promote the financial performance of enterprises. When we introduce management competence as a moderating variable, we find that competent managers can improve financial performance in an effective internal control environment.
Research on Stock Price Forecast Based on ARIMA-GARCH Model
Authors: Gao Jie
Published: September 2021

The stock plays a vital role in economic life, and the economic development of enterprises can be measured by the development and change of stocks. In this paper, the closing price of Ping An stock in China from 2017 to 2019 is selected as the time series empirical analysis data, and the ARIMA-GARCH model is established to predict the law and trend of the stock price change. The results show that the compound model can fit the fluctuation law well, and reasonably predict the short-term fluctuation trend.
Design of the Trans-provincial New Energy Spot Transaction Mode and Analysis of the Mode’s Effects on New Energy Consumption
Authors: Wei Yuan , Caixia Wang , Qionghui Li , Ning Chen , Hao Fan , Liang Xu
Published: September 2021

Trans-provincial new energy transactions consist of medium- and long-term transactions and spot transactions. Trans-provincial spot transactions have been mainly executed in areas where there is some difficulty with new energy consumption. To further improve the system’s capability to accommodate new energy, this paper designs a replacement transaction mechanism for electricity delivered through the same channel according to the status quo of trans-provincial new energy spot transactions and the reality of China’s electric power market. A production simulation-based decision analysis model for trans-provincial new energy consumption is established so as to analyse quantitatively the effects of the proposed transaction mode on new energy consumption. A typical case is selected out from a certain province as the delivery end, and the testing results show that the trans-provincial spot transaction mode and the quantitative analysis model proposed in the paper can improve the new energy consumption and utilization rate of the delivery end significantly.
The Construction of Food Testing Intelligent Laboratory Based on “Internet+” and Big Data Technology
Authors: Chen Kai , Hao Miao , Tan Hong , Huang Wei , Xin Fangjian , Su Bin
Published: September 2021

Food safety testing is of great significance for building a harmonious society. With the advent of the Internet era, the number of data indicators to be considered in food safety testing has gradually increased, and traditional food testing cannot adapt to the fast pace of today’s times. In order to meet the current challenges of food testing, this paper analyses the advantages of “Internet +” in building a food testing laboratory based on the challenges of food safety testing in the Internet era, and discusses the advantages of “Internet +” in the era of food testing. The paper discusses the intelligent working mode of food testing laboratories in the “Internet +” era, and combines big data technology to build an intelligent and comprehensive laboratory management platform, so as to build a new era of food testing intelligent laboratory, which improves the efficiency of food testing managers, reduces the workload, improves the accuracy of food safety testing, and helps the healthy development of the food industry.
The digital transformation and application prospect of military procurement management
Authors: Tingting Hou , Rui Cheng , Zhiyu Sun
Published: September 2021

Throughout the military and economic development of various countries and the frontier of public resources, the development from informatization to digitalization and intellectualization has become the inevitable call of The Times. In the era of digital logistics, strengthening the digital management ability of military procurement is an inevitable outcome to meet the needs of modern war. Procurement digital management integrates big data, cloud computing, Internet of Things, process automation and other technologies to help the digital upgrading of traditional procurement links. How to apply digital technology to promote the construction and development of modern military procurement has become a subject worth in-depth discussion.
Resource Curse: Experience Study on Economic Development of Petroleum Countries
Authors: Yuan Yuan
Published: September 2021

This paper studies the causes of “resource curse” from the perspective of “national utilization of petroleum resources” and uses the samples of eight typical oil resource-rich countries to study their national economic growth status. Empirical studies show that the resource curse effect of most countries is caused by “Dutch disease". Relying too much on the development of the oil resources industry, with the unreasonable industrial structure, the excessive export of oil resources, and the “extrusion effect” of production factors are the reasons that delay the technological innovation and development of the industry and inhibit the balanced development of other industries.
The progress and current status of Tokamak: a systematic review
Authors: Song Yuxuan
Published: September 2021

Nuclear fusion energy is an ideal energy source for the future due to the clean and efficient features, first proposed by Russian scientists in the 1950s. With the successful construction and operation of a batch of tokamak devices globally, a series of major achievements have been realized in magnetic confinement fusion (MF). On this basis, the recent progress and current status of tokamak devices are systematically reviewed from academic literatures and official websites. To better demonstrate, the principle of MF and the history of a tokamak are introduced firstly. Subsequently, developments of four typical state-of-art tokamak facilities (JT60, FTFR, JET, EAST) are discussed detailly. These results offer a guideline for tokamak device construction and MCF realization.
Research on the Application of 3D New Technology Based on Digital Grid
Authors: Ren Chunguang , Li Chunhui , Xue Kai , Xue Chao , Han Yanbin
Published: September 2021

The strategic goal proposed by State Grid Corporation is to carry out the digital transformation of the power grid. Among them, the value of the digital power grid is to solve the problem of data gaps required for artificial intelligence in all aspects of the power system in the future. The article briefly introduced the current development of 3D design software in the power system and the application direction of new 3D technologies.
SWOT Analysis and Countermeasures for the Development of Wudang Mountain Martial Arts Tourism Industry
Authors: Ke Yi
Published: September 2021

Through research methods such as expert interviews and field studies, this author believes that under the policy opportunity of the country vigorously promoting the development of sports tourism industry, Wudang Mountain, as a well-known scenic spot and a famous Taoist mountain, should seize the opportunity to deeply integrate martial arts (Wushu) elements into the regional tourism industry and create a composite multi-layer Wushu tourism industry pattern to better promote the industrial development. By giving full play to its own advantages and making up for its own shortcomings, Wudang Mountain will be able to achieve the goal of transformation and upgrading of the region’s tourism industry and open up new horizons for the development of Wudang Wushu tourism industry.
How to balance eco-environmental improvement and investment shortage ----- practice from the eco-environmental public-private partnership projects in China
Authors: Fan Yu , Zhao Yunhao , Xin Lu , Lu Jing , Xu Shunqing , Xu Zhijie
Published: September 2021

Faced with the severe eco-environmental problems and economic slowdown, China started the exploration of public-private partnership mode on eco-environmental protection projects, aiming to solve the disbalance between environmental improvement and investment shortage. This study systematically analyzed the characteristics, policy and market reactions of eco-environmental protection public-private partnership projects since 2014. Till the end of 2018 in China, the number of eco-environmental protection public-private partnership projects was 2,914 and investment was 1.84 trillion RMB, accounting for 33.67% and 13.94% of the total, respectively. The peak year was in 2017, then the number of eco-environmental protection public-private partnership projects dropped significantly in 2018. It is estimated that from 2014 to 2018, the investment from eco-environmental protection public-private partnership projects in the implementation phase contributes to 3.2% of China's GDP, 0.2 % of economic growth. To some extent, it has accelerated the process of ecological and environmental governance in China, especially in the field of municipal environmental infrastructure construction and comprehensive environmental treatment. However, the expected effect of eco-environment improvement from eco-environmental protection public-private partnership projects is difficult to guarantee, with the absence of key mechanisms and policies.
Analysis of Typical “Assembly-Components” Relationship Models in the Automobile Industry Chain
Authors: Minghao Zhu , Zhibo Zhang , Xueqiao Wu
Published: September 2021

The research object of this paper is the model of correlation between automobile manufacturers and auto parts manufacturers in major automobile manufacturing countries of the world. After first analyzing the characteristics, advantages and disadvantages of typical “assembly-components” relationship models in US (Ford model), Germany (Volkswagen model), Japan (Toyota model) and China (Geely model), this paper explores the degree of correlation between companies involved in these typical models, and in the end draws conclusions and points out the deficiencies of the research.
Discussion on the logic mechanism and implementation strategy of unblocked “Dual Circulation” Development Pattern blocking point
Authors: Ling Song
Published: September 2021

The implementation of the strategy of “a new development pattern with domestic and international cycles as the main body and mutual promotion of domestic and international dual cycles” is of great strategic significance for promoting the high-quality development of my country’s economy, comprehensively deepening reforms, and promoting high-level opening up. This article starts from the unblocked double-circle block point, through the explanation of the background meaning of the construction of the new development pattern, the analysis of the scientific connotation of the new development pattern, and the study of the implementation strategy to promote the new development pattern. This is a major strategic decision to keep pace with the pulse of economic development in the new era, and has important practical significance for activating and digging into the domestic market space and responding to the complex and complex impact of globalization.
An Investigation on the Present Situation of Wild Rhododendron Resources and Its Tourism Development and Utilization in Panxi Area
Authors: Ying Yuan , Qiang Luo
Published: September 2021

Panxi region is an important origin and distribution center of wild Rhododendron spp., which has important ornamental and tourism development value. This study investigated the present situation of wild Rhododendron resources in Sichuan Province, and analyzed the species number, horizontal distribution, vertical distribution, correlation with existing scenic spots and traffic accessibility, and put forward the prospect and suggestions of making full use of the rich wild Rhododendron resources in Panxi area for tourism development and boosting rural revitalization.
Research progress in pathogenesis and treatment of neuroinflammation
Authors: Shi Yingxin , Zhang Xiangyu , Zhang Heng , Ge Linfeng , Zhao Lihui
Published: September 2021

Neuroinflammation, defined as an inflammatory response mediated by central nervous system astrocyte, Microglia and endothelial cells, disrupts homeostasis and is typical of many Neurodegeneration. The DA receptor family is mainly expressed in Microglia, and microglia-induced neuroinflammation is an important pathogenesis of Neurodegeneration, this article reviews the pathogenesis and treatment of neuroinflammation.
Lattice structures under uniaxial impact loads: An experimental study
Authors: Riot Alexandre , Panettieri Enrico , Montemurro Marco , Guerard Sandra , Girardot Jérémie , Cosculluela Antonio
Published: September 2021

Innovative additive manufacturing processes open new design opportunities, in the field of periodic cellular shock absorbers. In this work, an experimental campaign on lattice samples has been developed and carried out for intermediate velocities. The geometries of the lattice samples used in the experimental tests are the result of a sensitivity analysis conducted in a previous work. As a complement to the results provided by the numerical model used in the sensitivity analysis, the experimental tests highlighted an aspect of capital importance: the geometry maximizing energy absorption is highly dependent on the applied strain. Furthermore, local buckling effects, induced primarily at the sample’s surfaces in contact with the support of the testing machine, induce a stiffness decrease for specific geometries, thus reducing the absorbed energy. This study emphasises the importance of geometry selection, to tailor specific mechanical responses.
Development of an innovative specimen geometry for tensile split Hopkinson tests
Authors: Peroni Marco , Croteau Jean-François , Cantergiani Elisa
Published: September 2021

Specimen manufacturing is one of the critical issues to solve during a dynamic material characterization, especially by mean of the Hopkinson bar technique. In particular, concerning tensile testing, the sample is generally axisymmetric with two threaded ends to directly connect it to the Hopkinson bars. In this context, this work presents the development of an innovative sample geometry and related fixtures that can be widely adopted when conventional manufacturing procedures are problematic or when there are numerous specimens. The Tensile Hopkinson Extruded Design Sample (THEDS) geometry requires properly shaped bar ends that can be obtained by wire electrical-discharge machining. The THEDS geometry has been efficiently applied to a test campaign on electron-beam welded copper and niobium specimens. The performances of the developed geometry have first been assessed using digital image correlation (DIC) to compare the results obtained at quasi-static and intermediate velocities with a standard tensile specimen geometry. Secondly, dynamic tests at up to about 1000 s-1 have been performed with a modified Hopkinson bar system at the European Commission (JRC) using the THEDS geometry.
Feasibility Study of a Combined Tension-Torsion Hopkinson Bar
Authors: Sasso Marco , Mancini Edoardo
Published: September 2021

The increasing interest to improve the description of the plastic behavior and the fracture prediction for ductile materials under complex loading conditions conducted the researchers to overcome the J2 plasticity theory. To do this more sophisticated plasticity model base on ductile damage have been implemented. Material model parameters must be identified by means of proper testing and calibration procedures requiring different loading conditions. Different types of tests must be performed, imposing multiaxial stress paths to the specimens. Tensile tests on smooth and round notched bars, plane strain tests, torsion tests, compression and combined tension–torsion tests on hollow and solid cylindrical bars must be executed. While multiple works are present in literature for model assessment and validation in quasi-static conditions, nothing can be found at high strain rate in biaxial conditions (tension-torsion). Biaxial tests in dynamic conditions are very difficult to carry out especially if you are interested to register the entire story of stress and strain. In this work, analytical and numerical study to evaluate the feasibility to carry out dynamic tension, dynamic torsion, dynamic torsion-static tension/compression and dynamic tension–dynamic torsion tests is discussed. The tests will be performed using a properly designed Split Hopkinson Bar.
Mechanical characterization of strain-hardening cement based composites (SHCC) under impact shear load
Authors: Tawfik Ahmed , Curosu Iurie , Mechtcherine Viktor
Published: September 2021

The paper presents a testing facility, which enables the characterization of the shear behavior of cementitious composites under quasi-static and impact shear load. The device was designed by means of an extensive numerical parameter study on device geometry, materials and wave propagation, as well as specimen configurations and boundary conditions. The new shear testing device was integrated into a gravity-driven Split-Hopkinson tension bar (SHTB) for shear impact experiments and in a hydraulic testing machine for quasi-static shear experiments on strainhardening cement-based composites (SHCC). The shear response of the SHCC specimens was derived from the force obtained on the transmitter bar in the SHTB accompanied by high-speed optical measurements, which also enabled an accurate analysis of the crack-opening displacements and fracture modes by means of Digital Image Correlation (DIC).
A Study on Measuring Distribution of Temperature for Instrumented Taylor Impact Test
Authors: Gao Chong , Iwamoto Takeshi
Published: September 2021

It is a challenge to apply the infrared detector to a test at higher strain rate because lots of articles report that the detector has an extremelyhigh responsiveness. However, all the research works about the measurement of temperature is focused on 103 s-1 of the strain rate achieved by the split Hopkinson pressure bar test. To evaluate the thermo-mechanical behaviour of materials in higher strain rate range, a method for measuring the temperature in Taylor impact test is required to establish. Additionally, a use of the fiber should be considered to protect the detector from any damages by the impact of the specimen and realize the measurement in the point-like area. In this study, an optically-measuring system of temperature with the infrared detector and PIR fiber is designed. Then, the designed system is introduced into the apparatus based on the instrumented Taylor impact test proposed recently. The temperature rise at a local point on the surface of pure aluminium is measured during the test. Then, a calculation for distribution of temperature from a heat conduction equation is proposed.
A strain-rate dependent engineering approximation of the temperature rise in plastically-deforming DP steel
Authors: Li Xueyang , Roth Christian C. , Mohr Dirk
Published: September 2021

Experiments at ten strain rates ranging from 0.001/s to 4/s are carried out on uniaxial tension specimens extracted from DP800 metal sheets. Digital Image Correlation (DIC) is used to obtain surface strain fields and a high speed infrared (IR) camera is employed to measure the corresponding temperature rise due to plastic dissipation. A temperature rise of 60K is witnessed for the highest loading speed whereas minimal temperature rise (<1K) is seen for the lowest loading speed. To minimize the computational cost by treating the temperature as an internal state variable, (effectively avoiding more complex coupled thermo-mechanical analyses), a logarithm based function is proposed that models the transition from isothermal to adiabatic conditions. The proposed function exhibits a higher accuracy compared to literature formulations.
Numerical modeling of the dynamic strain aging in steels at high strain rates and high temperatures
Authors: Rubio R. A. , Hokka M.
Published: September 2021

Carbon steels can be heat treated to produce different microstructural variations and mechanical properties. At high temperatures the material plasticity and strength can be influenced by diffusional effects like the Portevin-Le Chatelier effect, leading to a commonly observed increased strength at elevated temperatures. The diffusional effects are influenced by the chemical composition, but also the heat treatment history that affects the local composition and especially the concentrations of free solute atoms. In this work, a numerical approach was implemented to reproduce the thermomechanical behaviour of two different microstructural variants of steel grade C45. The experimental data used to calibrate the model includes information of the plastic behaviour of material subjected to dynamic compression loading at a wide range of temperatures. Special emphasis was focused to describe the effects of the dynamic strain aging (DSA) on the flow stress. A strategy based on machine learning was implemented to obtain a model that reproduces the strengthening of the material due to diffusional effects. Cubic Support Vector Machine models were trained for both microstructure variants of the steel and different surfaces were obtained to describe the topology of the flow stress as function of temperature and strain rate. The model predictions were compared to the behaviour described by the Johnson-Cook model to estimate the influence of the DSA effect on the strength of the material at high strain rates and temperatures. Furthermore, the model quantifies how the microstructure affects the strength of the material and the strength of the DSA-hardening.
Effect of microstructure on dynamic compressive behavior of cellular materials
Authors: Tateyama Kohei , Watanabe Keiko
Published: September 2021

It is known that the microstructure of cellular materials has a significant impact on their compressive properties. To study these phenomena, a hierarchical Poisson disk sampling algorithm and Voronoi partitioning were used to create a 3D numerical analysis model of cellular materials. In this study, we prepared random, periodic, and ellipsoidal cell models to investigate the effects of cell shape randomness and oblateness. Numerical experiments were performed using the finite element method solver RADIOSS. In the numerical analysis, an object collided with the cellular materials at a velocity of 25 m/s. The results showed that the flow stress of the random cell model was higher than that of the periodic cell model. Further, it was found that the aspect ratio of the cell shape has a significant impact on the mechanical properties of cellular materials.
The effect of Nb on the high strain rate hydrogen embrittlement of Q&P steel
Authors: Vercruysse Florian , Claeys Lisa , Depover Tom , Verbeken Kim , Verleysen Patricia , Petrov Roumen
Published: September 2021

Quenching and Partitioning (Q&P) steels are, due to their excellent combination of strength and ductility, seen as good candidates for the third generation advanced high strength steels (AHSS). Although the TRIP effect is beneficial for the overall mechanical behaviour of these steels it potentially can have detrimental effects when strained in a hydrogenenriched environment. The solubility of hydrogen is high in austenite but low in high carbon martensite. Martensite is even in the absence of hydrogen already a possible damage initiation spot. The effect of hydrogen under static and dynamic tensile loading was evaluated in a Q&P and a Nb micro-alloyed Q&P steel. Experiments were carried out under a strain rate ranging from 0.03 s-1 till 500 s-1 and correlated with the hydrogen uptake characterised via thermal desorption spectroscopy (TDS). The presence of Nb resulted in a 25% increase in the hydrogen uptake capacity. A higher susceptibility to hydrogen was observed in the Nb steel partially due to the high hydrogen fraction, but also because of the larger fraction of low stability austenite. However, when tested under dynamic conditions the hydrogen susceptibility is minor and even improved in the micro-alloyed Q&P steel compared to the standard Q&P steel.
Influence of strain rate on the mechanical response of nanostructured coppers elaborated by SPD and SPS
Authors: Couque Hervé , Khoptiar Yuri , Bernard Frédéric , Gutman Itamar , Bussiere Florian , Naimi Foad , Boulanger Rémi , Barthélémy François
Published: September 2021

The influence of strain rate on the mechanical response of two different nanostructured pure coppers was investigated under uniaxial compression. The first nanostructured copper was elaborated by powder metallurgy using the Spark Plasma Sintering (SPS) process. The second nanostructured copper was elaborated by Severe Plastic Deformation (SPD). Conventional characterizations were conducted with quasi-static compression and tensile tests, hardness tests and, with microstructure analysis. The effect of strain rate was evaluated under uniaxial compression at strain rates varying from 10-4 to 10+4 s-1. The high strain rate data were generated with a direct Hopkinson impact technique. The increase of strength with strain rates was analysed and discussed from the Scanning Electron Microscope observations and grain size distribution. The mechanical properties are consequently dependent on the metallurgical history of these samples prepared according to two different routes.
Optimisation of ballistic protection systems based on impact test/simulation correlation
Authors: Cosquer Yohan , Longère Patrice , Pantalé Olivier , Gailhac Claude
Published: September 2021

The complexity of ballistic protections increases with their efficiency. On this basis, an exclusively empirical approach is not adapted to optimise complex protection systems and the resort to numerical simulations is preferred if not mandatory. The present study proposes a methodology aiming at optimising complex multi-layer ballistic armours based on an experimental-numerical correlation. A multi-layer system is taken as example. A numerical model is first calibrated according to impact-on-monolithic-target test results. Once the model is validated, an optimisation process considering multi-layer configurations involving a sharp-nosed threat modifies the plates’ thicknesses in order to minimise the total mass while ensuring the system’s protective capacity in terms of residual velocity. The optimisation process shows that a single layer system is more efficient than a multi-layer one in the studied case.
Modern high strength steels under high strain-rate regimes
Authors: Cadoni Ezio , Dotta Matteo , Forni Daniele
Published: September 2021

In order to properly design critical infrastructures and buildings in steel (bridges, high-rise building, off-shore, cranes, etc.), certain requirements concerning to mechanical resistance and robustness under exceptional actions have to be carefully fulfilled. An acceptable level of safety must be assured to avoid human loss, environmental pollution and material damage. These structures can be subjected to severe accidental loading such as blast or impact. In this context it is fundamental to adequately know the behaviour of structural steel under high strain rate. Modern high strength steels are quenched and selftempered steels. These steels have several layers with differentiated microstructures (martensitic in the cortical part and ferritic in the core). The behaviour of the single layer at high strain rate regimes have to be accurately studied. The paper collects and discusses the tensile results at high strain rate obtained on samples of homogeneous layers of S690QL and S960QL steels. Finally, the characterisation of the single layers has been used in order to analyse the results obtained in large specimen obtained from slabs 12mm thick.
Strain rate sensitivity of the aluminium-magnesium-scandium alloy - Scalmalloy®
Authors: Jakkula Puneeth , Ganzenmüller Georg , Gutmann Florian , Hiermaier Stefan
Published: September 2021

This work investigates the strain rate sensitivity of the aluminiummagnesium-scandium alloy Scalmalloy, which is used extensively for additive manufacturing of lightweight structures. This high strength aluminium alloy combines very good weldability, machinability and mechanical strength: it can be heat-treated to reach nominal ultimate tensile strengths in excess of 500 MPa. We report tensile tests at strain rates ranging from 10−3 /s to 103 /s at room temperature. It is well known that Al-Mg alloys exhibit a negative strain rate dependency in combination with serrated flow caused by the Portevin-Le Chatelier effect, which describes the interaction of Mg solutes with dislocation propagations. In contrast, in Al-Sc alloys, the flow stress increases with increasing strain rate and displays positive strain rate dependency. Additionally, the presence of Sc in the form of Al3-Sc provides a fine-grained microstructure which allows higher tensile and fatigue strength. This research shows how these combined effects interact in the case of Scalmalloy, which contains both Mg and Sc. Tests are performed at quasi-static, intermediate and high strain rates with a servohydraulic testing machine and a Split-Hopkinson tension bar. Local specimen strain was performed using 2D Digital Image Correlation.
Effect of welding and heat treatment on the properties of UHSS used in automotive industry
Authors: Noorsumar Gulshan , Vysochinskiy Dmitry , Englund Even , Robbersmyr Kjell G. , Rogovchenko Svitlana
Published: September 2021

This paper deals with the undesired effects of the heat treatments on the mechanical properties of (UHSS) Ultra High Strength Steel used nowadays in automotive industry to improve crashworthiness performance of vehicles. The UHSS specimens were extracted from certain parts of the car body and subjected to different heat treatments. Four types of specimens were tested: untreated, welded with metal inert gas welding, heat treated at 800 °C, and heat treated at 1250 °C. All heat-treated specimens showed dramatically reduced values of strength. The results suggest that it is important to follow the official repair manuals avoiding unnecessary welding and improper heat treatments of UHSS. The experiments provide the data necessary for constructing a constitutive model and performing a finite-element analysis of improperly repaired UHSS parts.
On the study of the dynamic response in 3D additively manufactured auxetic structures
Authors: Fjeldberg Niklas , Pernas Jesús , Varas David , Martín Jordi
Published: September 2021

The main aim of this work is to analyse the quasi-static and the dynamic response and deformation behaviour of polymeric auxetic structures manufactured with an SLA (stereolitography) additive manufacturing technique. To this end, different experimental tests were performed using a universal servo-hydraulic instron machine and a Split Hopkinson Pressure Bar (SHPB). The study focuses on the understanding of the mechanical deformation response of the metamaterial depending on the type of load, the amount and distribution of the unit cells and the strain rate applied.