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Electrochemical discharge machining (ECDM), as a new type of non-traditional machining method, is widely used in the machining of insulating hard and brittle materials such as glass and ceramics. However, there are some problems such as difficulty in circulating electrolyte, resulting in poor quality machining of deep and small holes. In this paper, electrochemical discharge machining with ultrasonic vibration and tube electrode is used to improve the flow field in the machining gap and enhance the machining quality by using the injected electrolyte inside the tube electrode and ultrasonic vibration. First, the temperature distribution state of electrochemical discharge is simulated, and the influence of the coupling effect of the electrolyte injection and ultrasonic vibration on the machining gap is analyzed. And then, the influence weights of each factor were analyzed by orthogonal experiments and further analyzed to obtain the optimized combination of machining parameters, which reduced the entrance size of small holes by 19.3%, increased the machining depth by 18.5% and increased the depth-to-diameter ratio by 46.2% compared with the traditional ECDM. The effect of ultrasonic vibration was studied on the basis of the optimized machining parameters. The results show that the optimized effect of ultrasonic vibration with an amplitude of 7μm is most obvious under the conditions of low pressure and low injection rate. Finally, with the optimized machining parameters, a 5×5 array of small holes and three deep and small holes were machined, demonstrating that electrochemical discharge machining with ultrasonic vibrating tube electrode can be an efficient and high-quality method for machining small holes. [ABSTRACT FROM AUTHOR]

Main conclusion: Negatively charged carboxy-polystyrene (CPS) and positively charged amino-polystyrene (NPS) could significantly inhibit the biomass and flavonoid content of dandelion roots and leaves, and the inhibitory effect of NPS was stronger than that of CPS. The increasingly serious pollution of microplastics and heavy metals is likely to affect the efficacy of flavonoids synthesized by dandelion in natural medicine fields. Therefore, we combined hydroponic experiments with computational chemistry (Gaussian and autodock analysis) to explore the mechanism by which amino-polystyrene (NPS), carboxy-polystyrene (CPS), and lead affect the flavonoid biosynthetic pathway in dandelion (Taraxacum asiaticum Dahlst). Our results show that CPS and NPS could significantly inhibit the biomass and flavonoid content of dandelion roots and leaves, and the inhibitory effect of NPS was stronger than that of CPS. Mechanistic studies showed that CPS and NPS increased the content of O2− and H2O2 in dandelion roots and leaves, causing membrane lipid peroxidation, resulting in cell damage and decreased biomass. CPS and NPS inhibited related enzymatic activities by affecting their tertiary structures, resulting in a decrease in phenolic acid, coumaroyl-CoA, and flavonoid content. Dandelion preferred to absorb positively charged NPS compared to negatively charged CPS, but CPS inhibited the uptake of Pb by dandelion more strongly than NPS. Pb promoted CPS agglomeration and increased the surface positive charge of CPS through coordination bonds and hydrogen bonds, so more CPS entered dandelion under CPS + Pb treatment than under CPS alone. Although NPS and CPS reduced the uptake of Pb by dandelion, the biomass and flavonoid contents of dandelion were lower than those of single Pb treatment because of the higher toxicity of NPS and CPS than Pb. Pb significantly increased the effect of CPS on the root biomass of dandelion compared with CPS alone by increasing the positive charge of CPS. We suggest that microplastics with different charges and lead composite pollution inhibit dandelion flavonoid biosynthesis and provide a reference for the loss of dandelion medicinal components and economic value. [ABSTRACT FROM AUTHOR]

Spark-assisted electrochemical machining (SAEM) is an advanced machining method, which can manufacture microstructures on non-conductive hard and brittle materials such as glass. However, there are still some technological problems in the process of SAEM, among which the poor machining localization and the damage of microhole outlet are still unresolved. In order to improve the localization and quality of machining, a method of ultrasonic vibration–assisted spark-assisted electrochemical drilling (UASAED) was proposed in this paper. The application of ultrasonic vibration can reduce the gas film thickness and improve its stability in the spark-assisted electrochemical machining process, and reduce the discharge energy, so the machining localization and quality can be improved. Firstly, the formation of gas film in the drilling process was simulated and the influence of ultrasonic vibration on the gas film was analyzed. Secondly, the mechanism of material removal during drilling process was studied and simulated, and the mathematical model was established. Then, through a series of experiments, according to the established mathematical model, the relationships between the key machining parameters and the machining localization were studied, and the experimental results were consistent with the simulation. Finally, according to the machining parameters optimized by single factor experiments, 4 × 5 high-quality glass microhole array was successfully machined. The diameters of microholes were significantly reduced, with the inlet diameter decreasing by 20.59% and the outlet diameter by 14.9%, which indicated that ultrasonic vibration–assisted spark-assisted electrochemical drilling is an effective method to improve the machining localization. [ABSTRACT FROM AUTHOR]

Following the industrial change from mass production towards serial customization flexible technologies are becoming increasingly important. Therefore, the novel forming process “flexible roller beading” (FRB) is developed, which enables the continuous production of sheet metal profiles with customizable variable cross-sectional height and exploits the lightweight potential of profile-based constructions. To guarantee the quality and further processability of the profiles, component defects—primarily sheet wrinkling in the profile flange—must be avoided. The occurrence of wrinkling is affected by various geometric parameters of the targeted profile. This makes an empirical determination of the material-dependent process limits inefficient due to the expensive computational times of numerical simulations and effort of experimental test executions. Therefore, a mathematical model is developed which allows the analytical prediction of the process instabilities causing sheet wrinkling. The presented paper includes the description of the mechanical characteristics of FRB based on numerical and experimental investigations. The predictive analytical model derived from these findings determines the maximum longitudinal compressive stress in the profile flange, which is responsible for the wrinkling formation, based on the relevant geometric characteristics. By the comparison of the calculated occurring longitudinal compressive stress with the material-specific critical stress, sheet wrinkling can be predicted and failure-free profile geometries can be efficiently designed. The generality of the analytical model, independent of the profile geometry, is validated by experimental tests. [ABSTRACT FROM AUTHOR]

Based on the Cayley-Hamilton theorem and fixed-point method, we provide an elementary proof for the representation theorem of analytic isotropic tensor functions of a second-order tensor in a three-dimensional (3D) inner-product space, which avoids introducing the generating function and Taylor series expansion. The proof is also extended to any finite-dimensional inner-product space. [ABSTRACT FROM AUTHOR]

As cloud computing technology turning to mature, cloud services have become a trust-based service. Users’ distrust of the security and performance of cloud services will hinder the rapid deployment and development of cloud services. So cloud service providers (CSPs) urgently need a way to prove that the infrastructure and the behavior of cloud services they provided can be trusted. The challenge here is how to construct a novel framework that can effective verify the security conformance of cloud services, which focuses on fine-grained descriptions of cloud service behavior and security service level aggreements (SLAs). In this paper, we propose a novel approach to verify cloud service security conformance, which reduces the description gap between the CSP and users through modeling cloud service behavior and security SLA, these models enable a systematic integration of security constraints and service behavior into cloud while using UPPAAL to check the performance and security conformance. The proposed approach is validated through case study and experiments with real cloud service based on Open-Stack, which illustrates CloudSec approach effectiveness and can be applied on realistic cloud scenario. [ABSTRACT FROM AUTHOR]

For the multi-cylinder gasoline engine, the consistency among cylinders is an important index to affect the engine emission and the engine power. In this paper, an individual cylinder air-fuel ratio (A/F) control method for a fourcylinder camless engine with the electromagnetic valve train (EMVT) was proposed to reduce the imbalance of engine torque. An individual cylinder A/F estimation algorithm with a single universal exhaust gas oxygen (UEGO) sensor based on fading Kalman filtering was introduced. Four proportional-integral feedback controllers were built to regulate the individual A/F by adjusting the intake valve closing (IVC) timing of each cylinder independently based on the EMVT. The effectiveness of the proposed estimation and control approach was validated by co-simulation of GT-Power and Simulink. The results showed that the proposed estimation method could accurately estimate the individual cylinder A/F, and the maximum estimation error under steady state condition was less than 1 %. With the feedback control, both the individual A/F imbalance and the cylinderto- cylinder torque generation imbalance were decreased. [ABSTRACT FROM AUTHOR]

Lightweight and load-adapted products offer opportunities for savings in terms of material usage and environmental pollution. Additionally, the requirements of Industry 4.0 are changing industrial manufacturing from mass production to mass customization and on-demand manufacturing. These aspects are accompanied by new challenges and motivate the development of manufacturing systems with higher flexibility. Flexible processes allow the realization of several families of parts on the same system with shortened changeover time. For this purpose, the novel forming process "flexible roller beading" was developed, which enables the production of sheet metal profiles with customizable, height-variable cross-sections. The manufactured height development of the profile is not tool-constrained and can be adapted individually to the part application loads. By this level of flexibility, new design requirements can be satisfied in sheet metal profile manufacturing. Furthermore, semi-finished products can be produced, which potentially reduce the necessary expenses and expand the process limits of downstream forming processes. With the presented work being the initial introduction of "flexible roller beading", the operating principle is presented. As a key aspect, the feasibility of the novel process is shown. Therefore a flexible roller beading manufacturing system fulfilling the necessary kinematic requirements of the forming process is developed and experimental tests are carried out. Additionally, an FE model of the process is created and validated by experimental comparative tests. From the results of experimental and numerical investigations, defect types and process limits are determined, which are the bases for further process optimization towards the industrial suitability of flexible roller beading. [ABSTRACT FROM AUTHOR]

Through both analytical and numerical approaches, stability and bifurcation dynamics are studied for a nonlinear controlled system subjected to parametric excitation. The controlled system is a typical case of a two-degree-of-freedom system composed of a parametrically excited pendulum and its driving device. Three types of critical points for the modulation equations are considered near the principle resonance and internal resonance, which are characterized by a double zero and two negative eigenvalues, a double zero and a pair of purely imaginary eigenvalues, and two pairs of purely imaginary eigenvalues, respectively. With the aid of normal form theory, the stability regions for the initial equilibrium solutions and the critical bifurcation curves are obtained analytically, which exhibit some new dynamical behaviors. A time integration scheme is used to find the numerical solutions for these bifurcations cases, which confirm these analytical predictions. [ABSTRACT FROM AUTHOR]

This paper investigates the almost sure synchronization control problem for a class of stochastic delayed complex networks by using the stochastic differential equation theory and the Kronecker product technique. Different from the existing works, the considered problem is that all the nodes in the complex networks can synchronize with each other although the target node is unknown. Some sufficient conditions which guarantee the complex networks to have almost sure synchronization are derived and two kinds of controllers are designed, respectively. Finally, a numerical example is given to illustrate the effectiveness of the main results. [ABSTRACT FROM AUTHOR]

Carbon fiber reinforced phenolic based composites were prepared by laminating molding. The variation in mechanical characteristics of composites was evaluated with heating temperature and procedure. The microstructures of composites at different temperatures were observed by optical microscope and scanning electron microscope, respectively. The results showed that the main weight loss range of carbon/phenolic is from 300 to 800 °, before 700 ° the weight loss was resulted from pyrolysis and after that the weight loss was mainly by oxidation in the fiber phase; with the heat treatment temperature rising, the bonding at the interface of carbon fibers and resin matrix weakened; in the pyrolysis temperature range, the interlaminar shear strength(ILSS) of carbon/phenolic showed a rapid drop with temperature rising, and then decrease in the rate of ILSS became relatively slower; the fiber oxidation had little influence on the ILSS. [ABSTRACT FROM AUTHOR]

To date, the unpleasant trade-off between crystallization speed and thermal stability for most phase change materials is detrimental to achieve phase change memory (PCM) with both features of high-speed and good-retention. However, it is proved that Al doping in Sb2Te, served as storage media in PCM, favors both a high writing speed (6 ns) and a good retention (103 °C), as well as a low power consumption. Judging by experimental and theoretical investigations, doped Al atoms prefer to replace Sb in Sb2Te lattice, strongly bonded with 6 Te atoms, to form a homogeneous phase. While in amorphous Al doped Sb2Te (AST), Al atoms are in tetrahedral environment, firmly bonded with four Sb/Te atoms. The strong bonding in Al centered tetrahedron in amorphous AST can obstruct the collective motion of Sb atoms near the matrix boundary, leading to the improvement in thermal stability and the confinement in grain size. [ABSTRACT FROM AUTHOR]