bluuebunny/crossref_metadata_2025 huggingface dataset:
Simultaneous recoveries for semilinear parabolic systems
Authors: Lin Yi-Hsuan , Liu Hongyu , Liu Xu , Zhang Shen
Published: September 2022

In this paper, we study inverse boundary problems associated with semilinear parabolic systems in several scenarios where both the nonlinearities and the initial data can be unknown. We establish several simultaneous recovery results showing that the passive or active boundary Dirichlet-to-Neumann operators can uniquely recover both of the unknowns, even stably in a certain case. It turns out that the nonlinearities play a critical role in deriving these recovery results. If the nonlinear term belongs to a general C
1 class but fulfilling a certain growth condition, the recovery results are established by the control approach via Carleman estimates. If the nonlinear term belongs to an analytic class, the recovery results are established through successive linearization in combination with special complex geometrical optics solutions for the parabolic system.
Keldysh ionization theory of atoms: mathematical details
Authors: Boroumand N , Thorpe A , Parks A M , Brabec T
Published: September 2022

Keldysh ionization theory is one of the main pillars of strong field physics and attosecond science. It describes non-relativistic ionization rates of hydrogen-like atoms subjected to strong laser fields within the dipole approximation and the length gauge. According to this theory ionization can be described by two regimes: electronic tunneling through a laser-dressed atomic potential (tunnel ionization) and absorption of multiple photons at once (multi-photon ionization). There are many gaps in the mathematical steps and explanations in the original Keldysh paper. Therefore, the goal of this work is to give a detailed re-derivation of ionization rates following Keldysh’s formulation and to fill in the mathematical steps of this beautiful approach so that it is more accessible to a wider audience.
Mechanical properties of 3D-printed pentadiamond
Authors: Felix Levi C , Ambekar Rushikesh S , Woellner Cristiano F , Kushwaha Brijesh , Pal Varinder , Tiwary Chandra S , Galvao Douglas S
Published: September 2022

In this work, we combined fully atomistic molecular dynamics and finite elements simulations with mechanical testings to investigate the mechanical behavior of atomic and 3D-printed models of pentadiamond. Pentadiamond is a recently proposed new carbon allotrope, which is composed of a covalent network of pentagonal rings. Our results showed that the stress–strain (SS) behavior is almost scale-independent. The SS curves of the 3D-printed structures exhibit three characteristic regions. For low-strain values, this first region presents a non-linear behavior close to zero, followed by a well-defined linear behavior. The second regime is a quasi-plastic one and the third one is densification followed by structural failures (fracture). Young’s modulus values decrease from 520 to 486 MPa. The deformation mechanism is bending-dominated and different from the layer-by-layer deformation mechanism observed for other 3D-printed structures. They exhibit good energy absorption capabilities (3.5 MJ kg−1), with some structures even outperforming epoxy Kevlar and TRIP-steel. The structures show better absorption potential than the well-known porous architectures such as honeycomb, schwarzites, and tubulanes and occupy the same region of woven structures in the Ashby chart.
One-step measurement method of five-axis machine tools using a laser tracer
Authors: Hongdong Cong , Jun Zha , Yaolong Chen
Published: September 2022

To improve the motion accuracy of five-axis machine tools, it is important to develop a simple methodology to calibrate all geometric errors. This paper proposes a one-step measurement method to calibrate the five-axis machine tool using a laser tracer. First, a simplified geometric error definition of the five-axis machine tool is presented, which is sufficient and necessary to determine the tool error relative to the workpiece. Subsequently, a one-step measurement method using a laser tracer is proposed, and joint movements of five motion axes are adopted to simultaneously identify all geometric errors. Besides, a measurement path generating method is presented to save the trouble of manually planning the complex measurement path. Compared with the traditional two-step measurement method, the proposed method only needs four laser tracer positions and two reflector offsets, simplifying the measurement procedure and enhancing the measurement accuracy of geometric errors of rotary axes.
Assessment of multi-temperature relaxation models for carbon dioxide vibrational kinetics
Authors: Kosareva A , Kustova E , Mekhonoshina M
Published: September 2022

Several advanced models for multi-temperature vibrational energy relaxation rates are implemented to study adiabatic bath relaxation in carbon dioxide, among them a hybrid model based on state-to-state relaxation rates, the model based on the rigorous Chapman–Enskog theory, and modifications of the Landau–Teller (LT) models. Different sets of rate coefficients for vibrational energy transitions (Schwartz, Slawsky and Herzfeld (SSH) theory, forced harmonic oscillator (FHO) model) are used as well as various techniques for the relaxation time evaluation. Based on isothermal bath simulations it is found that the FHO model provides good agreement with experimentally measured relaxation times. Assessment of relaxation models shows that the three-temperature model based on the Chapman–Enskog theory yields excellent agreement with the detailed hybrid approach while being more computationally efficient; two-temperature models and modifications of the LT formulas cannot provide reliable description of intermode exchanges in polyatomic gases. The choice of the model for transition probabilities is crucial for identifying key relaxation mechanisms. When the FHO model is applied, strongly coupled relaxation in all CO2 modes is found whereas the model of SSH yields overpredicted relaxation rate in the symmetric-bending mode and almost uncoupled slow relaxation in the asymmetric mode. Possible ways for further model validation under glow discharge conditions are discussed.
Witnessing criticality in non-Hermitian systems via entopic uncertainty relation
Authors: Guo You-neng , Wang Guo-you
Published: September 2022

Non-Hermitian systems with exceptional points lead to many intriguing phenomena due to the coalescence of both eigenvalues and corresponding eigenvectors, in comparison to Hermitian systems where only eigenvalues degenerate. In this paper, we propose an alternative and accurate proposal based on the entropy uncertainty relation (EUR) to detect the exceptional points and identify different phases of the non-Hermitian systems. In particular, we reveal a general connection between the EUR and the exceptional points of non-Hermitian system. Compared to the unitary Hermitian dynamics, the behaviors of EUR in the non-Hermitian system are well defined into two different ways depending on whether the system is located in unbroken or broken phase regimes. In the unbroken phase regime where EUR undergoes an oscillatory behavior, while in the broken phase regime where the oscillation of EUR breaks down. Moreover, we identify the critical phenomena of non-Hermitian systems in terms of the EUR in the dynamical limit. It is found that the EUR can detect exactly the critical points of non-Hermitian systems beyond (anti-)PT symmetric systems. Finally, we comment on the prospective experimental situation.
Generation and verification of optical vortices with controlled phase based on coherent beam combining
Authors: Luo Hao , Yang Kaibo , Li Peng , Wen Feng , Gu Yuzong , Wu Zhenkun
Published: September 2022

Optical vortices (OVs) with controllable orbital angular momentum (OAM) distributions have potential applications in optical communication and optical manipulation. However, the source of optical vortices with segmented phase gradients generated by existing methods can be used only at a short distance because of their low power. In this study, based on coherent combining technology, we proposed a method to generate a controlled-phase optical vortex (COV). Compared with traditional OVs, the magnitude and direction of the local OAM of the COV are controllable. The transmission characteristics of the COV in free space were numerically examined using a split-step Fourier transform algorithm. We theoretically and experimentally proved the feasibility of the coherent combining technology to generate an COV and proved that it has the properties of non-diffraction and self-healing.
Learning feedback molecular network models using integer linear programming
Authors: Ozen Mustafa , Emamian Effat S , Abdi Ali
Published: September 2022

Analysis of intracellular molecular networks has many applications in understanding of the molecular bases of some complex diseases and finding effective therapeutic targets for drug development. To perform such analyses, the molecular networks need to be converted into computational models. In general, network models constructed using literature and pathway databases may not accurately predict experimental network data. This can be due to the incompleteness of literature on molecular pathways, the resources used to construct the networks, or some conflicting information in the resources. In this paper, we propose a network learning approach via an integer linear programming formulation that can systematically incorporate biological dynamics and regulatory mechanisms of molecular networks in the learning process. Moreover, we present a method to properly consider the feedback paths, while learning the network from data. Examples are also provided to show how one can apply the proposed learning approach to a network of interest. In particular, we apply the framework to the ERBB signaling network, to learn it from some experimental data. Overall, the proposed methods are useful for reducing the gap between the curated networks and experimental data, and result in calibrated networks that are more reliable for making biologically meaningful predictions.
Electrophysiological and functional signs of Guillain–Barré syndrome predicted by a multiscale neuromuscular computational model
Authors: Cardoso de Oliveira Marina , Naville Watanabe Renato , Kohn André Fabio
Published: September 2022

Objective. The diagnosis of nerve disorders in humans has relied heavily on the measurement of electrical signals from nerves or muscles in response to electrical stimuli applied at appropriate locations on the body surface. The present study investigated the demyelinating subtype of Guillain–Barré syndrome using multiscale computational model simulations to verify how demyelination of peripheral axons may affect plantar flexion torque as well as the ongoing electromyogram (EMG) during voluntary isometric or isotonic contractions. Approach. Changes in axonal conduction velocities, mimicking those found in patients with the disease at different stages, were imposed on a multiscale computational neuromusculoskeletal model to simulate subjects performing unipodal plantar flexion force and position tasks. Main results. The simulated results indicated changes in the torque signal during the early phase of the disease while performing isotonic tasks, as well as in torque variability after partial conduction block while performing both isometric and isotonic tasks. Our results also indicated changes in the root mean square values and in the power spectrum of the soleus EMG signal as well as changes in the synchronization index computed from the firing times of the active motor units. All these quantitative changes in functional indicators suggest that the adoption of such additional measurements, such as torques and ongoing EMG, could be used with advantage in the diagnosis and be relevant in providing extra information for the neurologist about the level of the disease. Significance. Our findings enrich the knowledge of the possible ways demyelination affects force generation and position control during plantarflexion. Moreover, this work extends computational neuroscience to computational neurology and shows the potential of biologically compatible neuromuscular computational models in providing relevant quantitative signs that may be useful for diagnosis in the clinic, complementing the tools traditionally used in neurological electrodiagnosis.
Nonlinear frequency chirping and radial restructure of the ion-temperature-gradient-driven turbulence
Authors: Sun Shiqiao , Wang Zihao , Wang Shaojie , Dai Zongliang
Published: September 2022

Global nonlinear gyrokinetic simulation of the ion-temperature-gradient (ITG) modes clearly demonstrates the nonlinear phase-space resonance, which can be well understood by the nonlinear frequency chirping due to the nonlinear poloidal acceleration of resonant particles by the large-scale structure of radial electric field rather than the widely discussed local shearing effects of the zonal flows. The nonlinear radial restructure of a single-n ITG mode generates multiple daughter-ballooning-modes.
Study on cryogenic deep drawing of 2219 aluminum alloy spherical shell
Authors: Fan Xiaobo , Kong Fanyu , Hong Jiqing , Huang Chuhan
Published: September 2022

In order to meet the urgent needs of aluminum alloy integral shell, a new forming process is required to solve the problem of splitting at room temperature. The plasticity of aluminum alloy is significantly improved at cryogenic temperature, and a novel cryogenic forming method was developed recently. In this paper, a cryogenic forming unit was established to study the cryogenic drawing behavior. The effects of sheet diameter on the wrinkling and deformation behaviors were analyzed by experiments and numerical simulations. The study showed that a spherical shell with a diameter of 200mm and a thickness-diameter-ratio of 1.0% could be formed at -160°C, which split at room temperature. The drawing depth was increased 74.3% at cryogenic temperature. The tendencies of wrinkling and splitting were controlled by the appropriate sheet diameter. It is concluded that cryogenic deep drawing has great potential for forming aluminum alloy integral shells.
DC Microgrid Protection System Based on Positive Channel Metal Oxide Semiconductor
Authors: Peng Yuhang , Wang Lujun
Published: September 2022

DC microgrid has received extensive attention and research because of its natural advantages of improving the consumption efficiency of distributed power sources, and in line with the development trend of clean environment and intelligent operation of power grids in the future. However, short-circuit fault protection of DC microgrid is a major challenge for the development of microgrid. Therefore, the author proposes a DC solid-state circuit breaker with a positive channel metal oxide semiconductor as the main switch, and through simulation, it is verified that this solid-state circuit breaker is feasible. The experimental results show that when the proposed solid-state circuit breaker is normally turned on, the positive channel metal oxide semiconductor is completely turned on, which has no effect on the power flow in the DC microgrid; when a short-circuit fault occurs in the DC microgrid system, the short-circuit current is used to couple the energy, the positive channel metal oxide semiconductor is reliably turned off. The stability and reliability of the system are improved, and it can be applied to the short-circuit protection of the DC microgrid, and has a good application prospect.
Experimental research on ultrasonic A-scan testing technology of composite solid propellant
Authors: Huang Liuchun , Li Jian , Li Bojun
Published: September 2022

To explore the application and development of ultrasonic non-destructive testing technology in composite solid propellant materials, the theory is combined with the principle and method of ultrasonic non-destructive testing technology and the material characteristics of composite solid propellant; Based on ultrasonic A-scan, the experimental testing of propellant grain with multiphase structure, complex properties and high attenuation was carried out using pulse reflection method and penetration method. For the testing system with probe emission frequency of 1 MHz and gain adjustable range of 60 dB, the thickness of propellant grain is recommended to be 10 ~ 50 mm for the pulse reflection method to effectively observe the first bottom echo and the second bottom echo, and the thickness of propellant grain is recommended to be less than or equal to 100 mm for the penetration method to effectively observe the transmission waveform. The coupling modes of ultrasonic testing technology are further analyzed, and the effect test is carried out. In addition, based on the pulse reflection method of direct contact coupling, the sound velocity of propellant grain is measured with probes with different frequencies. The results show that the higher the probe frequency is, the smaller the sound velocity of propellant grain is.
Enhanced blue thermally activated delayed fluorescence with rigid adamantane as non-conjugated linker for space-confined donor-acceptor charge transfer: a theoretical study
Authors: Sheng Yiqi
Published: September 2022

A lack of control over the relative orientation of donor and acceptor moieties in solid films is the main reason for poor electroluminescence efficiency found in most D-σ-A patterns. In this study, adamantane was introduced as the linker for the construction of a D-σ-A system since its rigid but non-conjugated nature. For a systematic study, the same donor (9,9-dimethyl-10-phenyl-9,10-dihydroacridine, DMTPA) and acceptor (2,4,6-triphenyl-1,3,5-triazine, TPZ) block were attached at different sites of the adamantine molecule, forming three kinds of configuration including face-to-face (FF), head-to-tail (HT), and chair (CH) style. DFT/TD-DFT simulation was carried out to investigate the electronic structures, optical characteristics, and charge transfer (ICT) properties of these three designed molecules. Attributed to a non-conjugated adamantane linker, the conjugation between donor and acceptor was disrupted for either of these molecules, resulting in high triplet energy of 2.79, 2.99, and 3.10 eV, respectively. Among them, the face-to-face style molecule presents the smallest ΔEST and greatest charge transfer excitation from donor to acceptor, suggesting an excellent potential for thermal activated delayed fluorescence (TADF). Face-to-face type molecule is a good option for a high-performance blue organic light-emitting diode (OLED) host material based on these results. Our investigation may open a door for designing new host molecule with other donor and acceptor groups to further enhance the efficiency and longevity of OLEDs.
Impact characteristics and strength evaluation of a slender body obliquely entering water at high speed
Authors: Zhu Chaobing , zhang Dahai , Fei Qingguo
Published: September 2022

Based on Coupled Eulerian-Lagrangian method, the impact characteristics and strength evaluation of high speed multi-angle oblique water entry of slender body were studied. In order to solve the complex fluid-structure coupling problem and large deformation problem, the Lagrangian grid is used to divide the slender body structure grid, and the Euler grid is used to divide the fluid grid, the effectiveness of the method is verified by comparing with the experimental results. Furthermore, by simulating the impact process of multi-angle water entry, the time-history curves of acceleration, stress and strain at the head position of the slender body were analyzed, and the strength evaluation was carried out to verify the structural safety combined with the residual strength formula. The results show that there is a positive correlation between the impact load and the water inlet angle, and the larger the water inlet angle, the greater the impact load; the residual strength factor of the slender body is positive at 15° and 20°, and the structure is safe, at 30°, the residual strength factor is -0.203, and the structure is unsafe.
Surface Quality for Cryogenic Milling Mg-1.6Ca-2.0Zn Medical Magnesium Alloy
Authors: Guo Xuan , Liu Guodong , Lin Qichao , Qiao Yang
Published: September 2022

As an absorbable and implantable biomedical material, magnesium alloy has made great progress in the application of biomaterials in recent years because of its excellent biocompatibility and biomechanics. At the same time, the disadvantages of magnesium alloy materials are more obvious. Because of the large linear expansion coefficient of magnesium alloy, the high temperature during dry cutting will lead to the degradation of machined surface quality. In addition, due to the active chemical properties of magnesium, cutting fluid is easy to cause corrosion of machined surface, and it is easy to react with water in cutting fluid to release hydrogen, causing accidents. In this paper, the effect of cryogenic milling with liquid nitrogen on the surface quality of magnesium alloy was studied by comparing the prepared magnesium alloy in different cooling environments, and the surface roughness model was established for prediction and verification. The results show that the roughness value of the surface machined by liquid nitrogen cryogenic milling is smaller than that of dry cutting, and the hardness value is larger than that of dry cutting, which is very beneficial to improve the surface quality of workpiece. This paper aims to improve the low-temperature machining process of magnesium alloy, and provide theoretical and practical guidance for the preparation, processing and application of high-performance medical magnesium alloy.
Super-wetting membrane with internalized PVA-TA gel networks for oil/water separation
Authors: Bai Zhongxiang , Liu Shuning , Liu Chenchen , Lin Guo , Jia Kun , Liu Xiaobo
Published: September 2022

In this paper, dimethyl sulfoxide (DMSO) was used as the hydrogen bond inhibitor to realize the co-dissolution of polyvinyl alcohol (PVA) and tannic acid (TA) in the casting solution. When the casting solution was placed in a water coagulation bath, the hydrogen bond cross-linking between PVA and TA is re-established, realizing the in-situ hydrogel network modification of the ultrafiltration membrane. The results show that the as-prepared membranes have underwater super-oleophobic properties and exhibit excellent anti-fouling ability during the separation of oil-in-water emulsions.
Optimization Design of FSAE Racing Car Sprocket Based on ANSYS
Authors: Zhou Jing , Lin Yu , Zhou Zhengzhi
Published: September 2022

In order to improve the dynamic performance of FSAE racing car, the finite element analysis and lightweight design of racing sprocket are studied in this paper, Firstly, the parametric modeling of the big sprocket of FSAE formula racing car was carried out, and then the finite element modeling and analysis of the initial design scheme was carried out based on ANSYS Workbench software. The lightweight design was designed on the premise of meeting the design requirements, and the reliability of the sprocket design was ensured. Finally, the strength, safety factor and life of the optimized model were simulated and verified, the sample was manufactured, and the physical experiment was carried out by assembling and integrating the model into the racing car. The results show that the optimized sprocket meets the work requirements.
Study on Microstructure Distribution of Al-Cu-Mg Alloy in Squeeze Casting Process
Authors: Li Longfei , Zheng Yuankai , Chen Yunbo , Feng Jian , Li Chunming , Chen Lin , Zuo Lingli , Zhang Yang
Published: September 2022

The squeeze casting process is an advanced technology, which is suitable for a wide range of alloys including Al-Cu-Mg alloys. The high pressure in squeeze casting process both refines the microstructure and enhances the mechanical property of the alloys. The heat transfer and solidification process are complex with the chilling mould and pressure of machine punch. This results in the inhomogeneous microstructure and property in casting alloy. This study focuses on the distribution of microstructure, chemical composition, and hardness of Al-Cu-Mg alloy along the radial direction of casting. The composition and area fraction of eutectic phases are characterized. Moreover, the relationship between the microstructure and mechanical property was also analysed to show the characteristic of microstructure in squeeze casting process.
Boron-containing carbon aerogels: excellent mechanical and thermal insulation properties
Authors: Mu Changqing , Cheng Yiling , Zhang Kai , Zhou Jiachang , Fan Jinpeng
Published: September 2022

The boron-containing carbon aerogels with excellent properties are reported: The precursor of carbon aerogels was modified by boric acid. Compared with the unmodified carbon aerogels, the compressive strength of the prepared carbon aerogels has been significantly improved, reaching 4.57MPa. The density of the carbon aerogels is between 0.253-0.287g/cm3, and the thermal conductivity is also kept at a low level of 0.057-0.062 (W⋅m-1⋅k-1). Excellent mechanical and thermal insulation properties make the prepared carbon aerogels have a good application prospect.
Degradation behavior of heat-treatment silicate adhesive under special working conditions
Authors: Zhao Yuhang , Fan Ruicheng , Cui Yongjie , Bai Jian , Li Chao
Published: September 2022

Inorganic adhesive is widely used in the sealing and connection of electronic devices. Its insulation is highly important in the performance of installation. In this paper, the insulation resistance and tensile strength of different composite silicate samples were measured by test machines. The morphology and surface composition were analyzed by electronic microscope and energy spectrum analyzer. The results show that: In a humid environment, the resistance insulation of adhesive increases with the rising of heat treatment temperature, and decreases with the increment of wet environment. When the modulus ratio of colloidal liquid is in the range of 7.2~9.1 and the heat-treatment temperature is larger than 600°C, the effect of moisture resistant is remarkable. The tensile strength of adhesive deteriorates with the increasing of humidity. Furthermore, with ascending heat treatment temperature, the tensile strength rises when the modulus ratio of adhesive is less than 7.2, and declines when it is more than 9.1.
Research of high temperature redundant thin film thermocouple
Authors: Sun Yongguo , Teng Fei , Guo Shuai , Chen Jie
Published: September 2022

Using the two-way flow-heat and one-way thermo-solid coupling simulation analysis methods, the designed thin-film thermocouple is analyzed by finite element, and the flow field, temperature field, and structural field inside the sensor are obtained. The high-temperature redundant thin-film thermocouple working simulation test shows that: The response time of the designed thin-film thermocouple is less than 2 seconds, and the stress and deformation are within the required range under the operating temperature load and wind load.
Research on multi-condition topology optimization design of stainless steel spot welding vehicle considering weight coefficient
Authors: Li Yana , Meng Di , Zhang Zeyang
Published: September 2022

A multi-condition topology optimization research method with weight coefficients is proposed to optimize the topological optimization of solder joints of stainless steel spot welding vehicle. Based on the SIMP variable density method, the compromise planning method, the orthogonal experiment design method, the gray correlation method, the entropy weight method and the analytic hierarchy process are used to introduce the weight coefficients, and objective function of the multi-objective topology optimization of the welding points of the stainless steel spot welding vehicle is established. This method realizes the topology optimization of the stainless steel spot welding vehicle model with the goal of flexibility the minimizing of multiple working conditions. It is concluded that the entropy weight method is more suitable for determining the weight coefficient analysis of objective function of multi-condition topology optimization. The average variation value of the flexibility under the three working conditions is the largest, and the number of solder joints is reduced by 17.8% after optimization. The proposed multi-condition topology optimization research method can be applied to the topology optimization design of railway vehicle structure.
Transient Temperature Field Simulation Analysis of Magnetorheological Grease Torsional Vibration Damper
Authors: Xiao Zida , Hu Hongsheng , Ouyang Qing , Shan Liyang , Su Hongbo
Published: September 2022

To reveal the transient temperature distribution pattern inside the magnetorheological grease (MRG) torsional vibration damper and explore the relationship between the current and the internal temperature of the device, the transient temperature simulation analysis of the MRG device was conducted in this paper. Firstly, a theoretical heat transfer model of MRG torsional vibration damper with dual heat source structural feature was established based on the Bingham constitutive model and the temperature-dependent viscosity characteristic of MRG. Then, the transient temperature field model of the MRG torsional vibration damper was developed by the finite element method, and the temperature field distribution and temperature-time variation characteristics of the MRG torsional vibration damper were analyzed. The simulation results show that the temperature rise of MRG in the working domain is the fastest, and the temperature rise rate slows down after the device works for 5.4s. The simulation results reveal the internal temperature distribution and temperature rise characteristics of the torsional vibration damper, which provides a theoretical basis for the structural optimization and control strategy design of MRG torsional vibration damper considering temperature factor.
Simulation analysis of titanium alloy micro-drilling based on thermo-mechanical coupling
Authors: Wu Zhenhe , Zhang Faping , Feng Kuikui
Published: September 2022

With the increasing demand for high precision micro parts in machining field, the development of micro hole drilling technology, especially the finite element simulation technology is rapidly promoted. However, there are many limitations in the simulation of micro-drilling, such as element size, computational efficiency, chip forming, etc. In the present work, a finite element software, Abaqus has been used to simulate the thermal-mechanical coupling micro-drilling process of titanium alloy material, and the key technologies, such as twist bit modeling, material constitutive model, chip separation criterion and element division, were investigated. Through simulation, it was found that with the increase of rotational speed and the decrease of feed speed, chip shape gradually fragmented, in addition, thrust force and torque diminished. Since chip shape, thrust force and torque are important factors affecting drilling quality and tool life, the work could offer important guiding significance for cutting parameter optimization.
Preparation and dynamic behavior of W-Mo-Y co infiltrated layer on the surface of 45 steel parts
Authors: Huang Change , Wang Chenglei , Tan Hong , Lu Rongwei , Yang Jijie , Xie Yingguang , Li Xin , Liu Chong
Published: September 2022

In this paper, W-Mo-Y co infiltration were carried out on the surface of 45 steel wedge components by plasma solid-state surface metallurgy technology. The phase, hardness, friction and wear properties before and after W-Mo co infiltration and W-Mo-Y co infiltration were systematically studied. The diffusion kinetics such as diffusion coefficient and diffusion activation energy were calculated by Fick's second diffusion law, and the effect of Y on the diffusion of W and Mo atoms in the infiltrated layer was obtained. It is found that the addition of rare earth Y element increases the diffusion coefficient of W and Mo atoms and reduces the diffusion activation energy, which has a certain catalytic effect. And the W-Mo-Y co infiltration significantly improves the surface hardness and wears resistance of the parts and prolongs the service life of the parts.
Design of Bi-directional Pump Servo System for Asymmetric Hydraulic Cylinder
Authors: Mao Hong-yong , Yang Xue-meng , Fan Zhuo , Lu Jing-jing , Jing Man-jun , Jiang Yong , Huang Ya-nong
Published: September 2022

In view of the shortcomings of the traditional overflow pressure regulating and throttling speed regulation system, such as large energy loss, high oil temperature and large reversing impact, a servo two-way pump control system for asymmetric hydraulic cylinder is proposed based on Siemens S120. TIA Portal And Starter software are used for the design of hardware configuration and program debugging. SimulationX is used to simulate the stroke process of the hydraulic cylinder, at the same time, experimental verification was carried out, which provides a new idea for the low energy consumption design of hydraulic cylinder servo control system, and has important practical significance.
Key Analysis of Design and Numerical Simulation for Aluminum Alloy Impeller Low-pressure Casting Mold
Authors: Wang Yingli , Wang Fengxian
Published: September 2022

It is of great practical value to complete the low-pressure casting of aluminum alloy impeller in the current development of low-pressure casting process. In the research, it is necessary to focus on factory realization and use low-pressure casting to produce aluminum alloy impellers, so that impeller castings with compact structure and meeting performance requirements can be obtained. Compared with other casting methods, low-pressure casting itself, as a precision casting method, can be cast on the metal solution with lower pressure in the application process. The castings can be filled and solidified under certain pressure, and the castings with compact structure can be obtained. In the research, Pro / Engineer is used to design the low-pressure casting mold for aluminum alloy impeller, and MAGMASOFT is used to carry out the filling and solidification process of aluminum alloy impeller. Through numerical simulation, we can accurately predict the defects of impeller castings, and optimize the mold scheme and pressure-time parameters according to the prediction results.
Improved LuGre-based friction modeling of the electric linear load simulator
Authors: Ping ZiLong , Zhang WenSen , Fu YongLing
Published: September 2022

In order to fulfill the requirement that the electric linear load simulator needs to improve the loading accuracy by the compensation method based on the friction model in the active loading situation with small load, considering the influence of load on coulomb friction and maximum static friction, an improved LuGre friction model with load is proposed. At the same time, since the friction effect is highly nonlinear and determined by numerous parameters, the differential evolution algorithm is utilized to identify the static and dynamic parameters of the model in two steps offline. Finally, under the sinusoidal signal for force command, the experimental test results verify that the improved LuGre model with identified parameters can accurately describe the friction characteristics of the electric linear load simulator.
Research of Parametric Modeling and Simulation Analysis Methods of Aero-engine’s Rear Variable Area Bypass Injector of Mapping Dispersive Dimension Based on ADAMS
Authors: Ye Shaoping , Li Jia , Xie Liyang , Song Rui , Yi Wang
Published: September 2022

Aiming at the problem of motion accuracy caused by dispersive dispersion in the design of the aero-engine rear variable area bypass injector, a multi-body dynamics model mapping dimension tolerance, part flexibility, and collision contact is established based on multi-body dynamics theory and ADAMS. The simulation results are verified with the theoretical solution, which is calculated in MATLAB to ensure the correctness of the simulation’s results. The effect of key design variables on the motion accuracy of the mechanism is analyzed by the parametric module. The reliability calculation method is studied based on the improved Latin hypercube Monte Carlo method mapping the dimension dispersion. The method provides the relevant basis for the structural design of the RVABI.
Improvement of phase inductance slope method for Without Position Sensor control of switched reluctance motor
Authors: Qiu Chunyuan , Sun Baojiang
Published: September 2022

At present, the research hotspot of switched reluctance motor is to realize the accurate control of motor without position sensor. Among many control methods, the phase inductance slope method is concerned by researchers because it does not need to add additional power supply circuit, and does not need to calculate the flux linkage and inductance curve in advance. Aiming at the defect that the phase inductance slope algorithm can not advance the opening angle and the position signal error is easy to appear near the opening angle, this paper makes an improvement and verifies the experiment.
Research on Cyclist Injury Based on Simulation Model of Real Electric Vehicle and Two Wheeled Vehicle Collision Accident
Authors: Zhao Lijun , Zhang Qian , Yang Na , Wang Jianfeng
Published: September 2022

There are more and more traffic accidents between cars and electric two wheeled vehicles. As a vulnerable participant in traffic, it is of great significance to study the head biomechanical injury of electric two wheeled vehicle cyclists. In order to study the head injury of cyclists, by optimizing the tissue material properties and material parameters of the head finite element model, a refined head finite element model is established and verified by Nahum cadaver experiment; Based on the real traffic accident of vehicle electric two wheeled vehicle collision, a multi rigid body model of vehicle electric two wheeled vehicle is established for vehicles, electric two wheeled vehicles and cyclists, and the reliability of the collision model is verified; The head finite element model is used to analyze the changes of equivalent stress. The results show that the equivalent stress of brain tissue is gradually transmitted from both sides of brain tissue to the cerebellar region at the back of brain, and finally concentrated in cerebellum.
Development of muon scattering tomography for detection of reinforcement in concrete
Authors: Dobrowolska M. , Velthuis J.J. , De Sio C. , Kopp A. , Milne R. , Pearson P.
Published: September 2022

Inspection of ageing, reinforced concrete structures is a world-wide challenge. Existing evaluation techniques in civil and structural engineering have limited penetration depth and do not allow to precisely ascertain the configuration of reinforcement within large concrete objects. The big challenge for critical infrastructure (bridges, dams, dry docks, nuclear bioshields etc.) is understanding the internal condition of the concrete and steel, not just the location of the reinforcement. Muon scattering tomography is a non-destructive and non-invasive technique which shows great promise for high-depth 3D concrete imaging. Here a method is presented to locate reinforcement meshes placed in a large-scale concrete object. A reinforcement mesh was simulated as two layers of 2 m long bars, forming a mesh. Two layers of the mesh were placed at several distances from each other inside a large concrete block. Previously, we have shown that using our autocorrelation technique for single meshes inside the concrete and using only one week worth of data taking, bars with a diameter of 7 mm and larger, could easily be detected for a 10 cm mesh spacing. The signal for 6 mm diameter bar exceeds the background and becomes very clear after two weeks of data taking. Here we show that we can detect the vertical positions of two mesh layers inside the concrete. This is a very important result for non-destructive evaluation of civil structures.
Editorial: Special issue on advances in nanomedicine
Authors: Zhang Ye , Pei Renjun
Published: September 2022

Nanomaterials are being increasingly used to develop new methods of disease diagnosis and treatment, thereby providing novel paradigms to break through the current limitations of medicine. However, there is still a long way toward the complete revolution for nanomedicine in the diagnosis and treatment of diseases. As nanoparticles are highly complex products and difficult to characterize, there are still many challenges. This special issue on Advances in Nanomedicine includes a series of topical reviews and original research articles that highlight the recent advances in diagnosis and therapy of nanomaterials.
Ferroelectricity controlled chiral spin textures and anomalous valley Hall effect in the Janus magnet-based multiferroic heterostructure
Authors: Zhu Yingmei , Cui Qirui , Liang Jinghua , Ga Yonglong , Yang Hongxin
Published: September 2022

Realizing effective manipulation and explicit identification of topological spin textures are two crucial ingredients to make them as information carrier in spintronic devices with high storage density, high data handling speed and low energy consumption. Electric-field manipulation of magnetism has been achieved as a dissipationless method compared with traditional regulations. However, the magnetization is normally insensitive to the electric field since it does not break time-reversal symmetry directly, and distribution of topological magnetic quasiparticles is difficult to maintain due to the drift arising from external fluctuation, which could result in ambiguous recognition between quasiparticles and uniform magnetic background. Here, we demonstrate that electric polarization-driven skyrmionic and uniform ferromagnetic states can be easily and explicitly distinguished by transverse voltage arising from anomalous valley Hall effect in the Janus magnet-based multiferroic heterostructure LaClBr/In2Se3. Our work provides an alternative approach for data encoding, in which data are encoded by combing topological spin textures with detectable electronic transport.
Impact of the Arctic oscillation from March on summertime sea ice
Authors: Lim Young-Kwon , Wu Dong L , Kim Kyu-Myong , Lee Jae N
Published: September 2022

Current understanding of the cold season Arctic oscillation (AO) impact on the summertime sea ice is revisited in this study by analyzing the role from each month. Earlier studies examined the prolonged AO impact using a smooth average over 1–2 seasons (e.g. December–March, December–April, March–May), ignoring large month-to-month AO variability. This study finds that the March AO is most influential on the summertime sea ice loss. First, the March AO is most highly negative-correlated with the AO in summer. Secondly, surface energy budget, sea level pressure, and low-tropospheric circulation exhibit that their time-lagged responses to the positive (negative) phase of the March AO grow with time, transitioning to the patterns associated with the negative (positive) phase of the AO that induces sea ice decrease (increase) in summer. Time evolution of the surface energy budget explains the growth of the sea ice concentration anomaly in summer, and a warming-to-cooling transition in October. The regional difference in sea ice anomaly distribution can be also explained by circulation and surface energy budget patterns. The sea ice concentration along the pan-Arctic including the Laptev, East Siberian, Chukchi, and Beaufort Sea decreases (increases) in summer in response to the positive (negative) phase of the March AO, while the sea ice to the northeast of Greenland increases (decreases). This sea ice response is better represented by the March AO than by the seasonally averaged winter AO, suggesting that the March AO can play more significant role. This study also finds that the sea ice decrease in response to the positive AO is distinctively smaller in the 20th century than in the 21st century, along with the opposite sea ice response over the Canada Basin due to circulation difference between the two periods.
The Weierstrass–Durand–Kerner root finder is not generally convergent
Authors: Reinke Bernhard , Schleicher Dierk , Stoll Michael
Published: September 2022

Finding roots of univariate polynomials is one of the fundamental tasks of numerics, and there is still a wide gap between root finders that are well understood in theory and those that perform well in practice. We investigate the root-finding method of Weierstrass, also known as the Durand–Kerner-method: this is a root finder that tries to approximate all roots of a given polynomial in parallel. This method has been introduced 130 years ago and has since then a good reputation for finding all roots in practice except in obvious cases of symmetry. Nonetheless, very little is known about its global dynamics and convergence properties.

We show that the Weierstrass method, like the well-known Newton method, is not generally convergent: there are open sets of polynomials 

p
p

of every degree

d
≥
3

d \ge 3

such that the dynamics of the Weierstrass method applied to 

p
p

exhibits attracting periodic orbits. Specifically, all polynomials sufficiently close to

Z
3

+
Z
+
175

Z^3 + Z + 175

have attracting cycles of period 

4
4

. Here, period

4
4

is minimal: we show that for cubic polynomials, there are no periodic orbits of length

2
2

or 

3
3

that attract open sets of starting points.

We also establish another convergence problem for the Weierstrass method: for almost every polynomial of degree

d
≥
3

d\ge 3

there are orbits that are defined for all iterates but converge to 

∞
\infty

; this is a problem that does not occur for Newton’s method.

Our results are obtained by first interpreting the original problem coming from numerical mathematics in terms of higher-dimensional complex dynamics, then phrasing the question in algebraic terms in such a way that we could finally answer it by applying methods from computer algebra. The main innovation here is the translation into an algebraic question, which is amenable to (exact) computational methods close to the limits of current computer algebra systems.
Analysis of divergence-free 𝐻¹ conforming FEM with IMEX-SAV scheme for the Navier-Stokes equations at high Reynolds number
Authors: Han Yongbin , Hou Yanren , Zhang Min
Published: September 2022

In this paper, we analyze the first-order implicit-explicit type scheme based on the scalar auxiliary variable (SAV) with divergence-free

H
1

H^1

conforming finite element method (FEM) in space for the evolutionary incompressible Navier-Stokes equations at high Reynolds number. The stability and a priori error estimates are given, in which the constants are independent of the Reynolds number. The velocity energy estimate is given without any condition on the time step, however, the a priori error estimates for the velocity are obtained with severe time step restrictions. In addition, a Reynolds-dependent error bound with convergence order of

k
+
1

k+1

in space is also obtained for the velocity error in the

L
2

L^2

norm with no time step restrictions. Here,

k
k

is the polynomial order of the velocity space. Some numerical experiments are carried out to verify the analytical results.
An exponential bound on the number of non-isotopic commutative semifields
Authors: Göloğlu Faruk , Kölsch Lukas
Published: September 2022

We show that the number of non-isotopic commutative semifields of odd order

p

n

p^{n}

is exponential in

n
n

when

n
=
4
t

n = 4t

and

t
t

is not a power of

2
2

. We introduce a new family of commutative semifields and a method for proving isotopy results on commutative semifields that we use to deduce the aforementioned bound. The previous best bound on the number of non-isotopic commutative semifields of odd order was quadratic in

n
n

and given by Zhou and Pott [Adv. Math. 234 (2013), pp. 43–60]. Similar bounds in the case of even order were given in Kantor [J. Algebra 270 (2003), pp. 96–114] and Kantor and Williams [Trans. Amer. Math. Soc. 356 (2004), pp. 895–938].