Two kinds of average approximation accuracy

Rough set theory places great importance on approximation accuracy, which is used to gauge how well a rough set model describes a target concept. However, traditional approximation accuracy has limitations since it varies with changes in the target concept and cannot evaluate the overall descriptive ability of a rough set model. To overcome this, two types of average approximation accuracy that objectively assess a rough set model’s ability to approximate all information granules is proposed. The first is the relative average approximation accuracy, which is based on all sets in the universe and has several basic properties. The second is the absolute average approximation accuracy, which is based on undefinable sets and has yielded significant conclusions. We also explore the relationship between these two types of average approximation accuracy. Finally, the average approximation accuracy has practical applications in addressing missing attribute values in incomplete information tables

Research status of stability in dynamic process of laser-arc hybrid welding based on droplet transfer behavior : a review

With the synergistic effect of laser and arc heat sources, laser-arc hybrid welding (LAHW) technology can improve welding speed and penetration depth, and enhance gap-bridging ability. This review describes the fundamental concepts and characteristics of droplet transfer behavior in LAHW. Emphasis was placed on the physical interaction between the laser and arc and the effect of the combined laser/arc heat sources on the welding process. However, the physical understanding of these multivariable and complex interactions is still evolving. Through numerous research findings and summary, it is found that there are several critical factors, including the laser-to-arc distance, heat source leading mode, shielding gas composition, and laser power, affecting the droplet transfer characteristics. This review critically interprets the latest development in the basic understanding of LAHW. It lays great stress on the coupling effect of laser and arc in droplet transfer dynamic process of LAHW, and offers a direction for the future study and progress of LAHW. Significant fields for future research are also confirmed

Research Progress on the Gut-Brain Axis Effects of Sugars and Sweeteners and Their Evaluation Methods

Sweeteners cannot completely replace the satisfaction provided by sugars, even though they offer a similar flavor perception and much higher sweetness intensity than sugars. Clarifying the biological mechanism of this phenomenon is important to improve the functional evaluation system for sweeteners and promote sweetener innovations. Herein, we review the research progress on the difference in the behavioral preferences of animals, the activity of brain regions and the activation patterns of the gut-brain axis induced by sugars and sweeteners, and we uncover the underlying reason why the brain distinguishes sugars from sweeteners, causing differences in individual behavioral preferences. Moreover, we propose that animal behavior, neural activity in brain regions, and the capacity to activate key receptors can be used to evaluate the gut-brain axis effects of sweeteners, which will provide a reference for innovative developments in the field of sweeteners

Peculiarity of the Mechanism of Early Stages of Photo-Oxidative Degradation of Linear Low-Density Polyethylene Films in the Presence of Ferric Stearate

Ferric stearate (FeSt3) is very efficient in accelerating polyethylene (PE) degradation, but there is a lack of exploration of its role in accelerating the early stages of polyethylene photo-oxidative degradation. This study aimed to investigate the effect of FeSt3 on the photo-oxidative degradation of PE films, especially in the early stages of photo-oxidative degradation. The results show that FeSt3 not only promotes the oxidative degradation of PE but also contributes significantly to the early behavior of photo-oxidative degradation. Moreover, the results of the density functional theory (DFT) calculations proved that the C-H in the FeSt3 ligand was more easily dissociated compared with the PE matrix. The generated H radicals participate in the coupling reaction of the primary alkyl macro radicals leading to the molecular weight reduction, thus significantly increasing the initial rate of molecular weight reduction of PE. Meanwhile, the transfer reaction of the dissociation-generated C-centered radicals induced the PE matrix to produce more secondary alkyl macroradicals, which shortened the time to enter the oxidative degradation stage. This finding reveals the mechanism by which FeSt3 promotes the degradation of PE at the early stage of photo-oxidative degradation. It provides guiding significance for the in-depth study of the early degradation behavior in photo-oxidative degradation on polyolefin/FeSt3 films

Proposal of a machining test to evaluate dynamic synchronization error of rotary and linear axes with reversal of rotation direction

The five-axis machining of a free-form surface often contains the reversal of a rotary axis’ rotation direction with linear axis synchronized with it. This paper proposes a new machining test to quantitatively evaluate the influence of the reversal of rotation direction on the surface geometry and roughness. In the five-axis machining, the trajectory of tool position and orientation is firstly given in the workpiece coordinate system by the CAM (Computer-aided Manufacturing) software, and the CNC (Computerized Numerical Control) system converts it to the machine coordinate system to calculate command trajectories. This paper clarifies that the tool path smoothing in the machine coordinate system can potentially cause a large contour error because of the dynamic synchronization error of rotary and linear axes. Although some academic works in the literature presented the smoothing in the workpiece coordinate system, many commercial CNC systems still employ the smoothing in the machine coordinate system, partly because machine tool users or makers do not clearly see how significant this influence can be on the machining accuracy. The proposed machining test enables a user to quantitatively evaluate it. The machining experiment shows that the geometric error of the finished test piece was as large as 0.16 mm under the conventional smoothing in a commercial CNC system, which can be significantly larger than the influence of other typical geometric errors of a five-axis machine tool. This paper shows, by numerical simulation, that the smoothing in the workpiece coordinate system can completely eliminate this contour error

Towards fully ab initio modeling of soot formation in a nanoreactor

A neural network (NN)-based model is proposed to construct the potential energy surface of soot formation. Our NN-based model is proven to possess good scalability of O(N) and retain the ab initio accuracy, which allows the investigation of the entire evolution of soot particles with tens of nm from an atomic perspective. A series of NN-based molecular dynamics (NNMD) simulations are performed using a nanoreactor scheme to investigate critical processes in soot formation, acetylene polymerization, and inception of PAH radicals. This shows that NNMD can capture the dynamic process of acetylene polymerization into PAH precursors. The simulation of PAH radicals reveals that physical interaction enhances chemical nucleation, and such enhancement is observed for clusters of π- and σ-radicals, which is distinct from the dimer. We also observed that PAH radicals of ~ 400 Da can produce core-shell soot particles at a flame temperature, with a disordered core and outer shell of stacked PAHs, suggesting a potential physically stabilized soot inception mechanism