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This study investigates the impact of economic policy uncertainty on corporation innovation in innovative cities. The study sheds light on different results from the previous literature by testing the moderator effects of entrepreneurial risk appetite on such impact.

A static panel estimator is applied to a Chinese sample of 416 firm-year observations from 2010 to 2019. This paper uses regression model to test the impact of uncertainty on enterprise innovation in innovative cities, and to test the regulatory role of entrepreneurial risk appetite. For a series of robustness analysis conducted by the author to deal with endogeneity, the results are robust.

The author finds reliable evidence that the economic policy uncertainty can promote corporations to invest more in R&D in innovative cities. In addition, the role of the entrepreneurial initiative is significant, and there is a positive moderating effect of entrepreneurial risk appetite between policy uncertainty and corporation innovation.

From a practical point of view, this study examines the impact of economic policy uncertainty on corporation innovation in innovative cities for the first time. It emphasizes the role of entrepreneurial risk-taking in the development of corporation innovation in Shenzhen, an innovative city. This research is of great significance to the formulation of government policies and the innovative choice of entrepreneurs. In addition, the research shows that the entrepreneurial risk appetite in innovative cities can have a positive impact on enterprise innovation. Therefore, when formulating policies, the government should take the subjective factors of entrepreneurs into account and support enterprises with innovation potential. The evidence of this study also helps entrepreneurs make innovative decisions and enhance their confidence in enterprise development.

By studying the impact of economic policy uncertainty on enterprise innovation under the regulation of enterprise risk appetite, this study shows the subjective and positive role of entrepreneurs in risk grasp in innovative cities for the first time. In addition, it fills the gap of the impact of policy uncertainty on innovative urban enterprises. In fact, although it is traditionally believed that economic policy uncertainty has a negative impact on enterprise innovation, the sensitive findings of this study reveal completely different results from previous studies.

This study aims to explore the possibility of using magnetic biochar composite (MBCC) derived from Heglig tree bark (HTB) powder (agricultural solid waste) and cobalt ferrite (CoFe₂O₄, CFO) for oil spill removal from seawater surface.

One-pot co-precipitation route was used to synthesize MBCC. The prepared materials were characterized by X-ray diffraction, scanning electron microscopy-energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy. The densities of the prepared materials were also estimated. Crude, diesel engine and gasoline engine oils were used as seawater pollutant models. The gravimetric oil removal (GOR) method was used for removing oil spills from seawater using MBCC as a sorbent material.

The obtained results revealed that the prepared materials (CFO and MBCC) were able to remove the crude oil and its derivatives from the seawater surface. Besides, when the absorbent amount was 0.01 g, the highest GOR values for crude oil (31.96 ± 1.02 g/g) and diesel engine oil (14.83 ± 0.83 g/g) were obtained using MBCC as an absorbent. For gasoline engine oil, the highest GOR (27.84 ± 0.46 g/g) was attained when CFO was used as an absorbent.

Oil spill removal using MBCC derived from cobalt ferrite and HTB. Using tree bark as biomass (eco-friendly, readily available and low-cost) for magnetic biochar preparation also is a promising method for minimizing agricultural solid wastes (e.g. HTB) and obtaining value-added-products.

A three-dimensional (3D) printing error simulation approach is proposed to analyze the influence of tilted vertical beams on the 3D printing accuracy. The purpose of this study is to analyze the influence of such errors on printing accuracy and printing quality for delta-robot 3D printer.

First, the kinematic model of a delta-robot 3D printer with an ideal geometric structure is proposed by using vector analysis. Then, the normal kinematic model of a nonideal delta-robot 3D robot with tilted vertical beams is derived based on the above ideal kinematic model. Finally, a 3D printing error simulation approach is proposed to analyze the influence of tilted vertical beams on the 3D printing accuracy.

The results show that tilted vertical beams can indeed cause 3D printing errors and further influence the 3D printing quality of the final products and that the 3D printing errors of tilted vertical beams are related to the rotation angles of the tilted vertical beams. The larger the rotation angles of the tilted vertical beams are, the greater the geometric deformations of the printed structures.

Three vertical beams and six horizontal beams constitute the supporting parts of the frame of a delta-robot 3D printer. In this paper, the orientations of tilted vertical beams are shown to have a significant influence on 3D printing accuracy. However, the effect of tilted vertical beams on 3D printing accuracy is difficult to capture by instruments. To reveal the 3D printing error mechanisms under the condition of tilted vertical beams, the error generation mechanism and the quantitative influence of tilted vertical beams on 3D printing accuracy are studied by simulating the parallel motion mechanism of a delta-robot 3D printer with tilted vertical beams.

The purpose of this study is to propose an automatic leveling method for a printing platform based on a three-point coordinate feedback. The proposed method is used in fused deposition modeling additive manufacturing systems. The coordinate error of the leveled plane is constrained to within  ± 0.2 mm, which is less than the printed layer thickness.

First, the model of the forward and inverse solutions of the parallel arm is obtained based on the principles of vector algebra. Second, the automatic leveling mechanism for collecting the z-coordinate is designed. The best position of the virtual origin plane is obtained by comparing the z-coordinates of the test points. Finally, after making multiple adjustments through a closed-loop z-coordinate feedback, the parallelism of the printing plane and the virtual origin plane is limited to an effective range.

The experimental results show that after three leveling attempts, the z-coordinate of the test points can be constrained to within  ± 0.2 mm, which shows that this method can effectively achieve automatic leveling in a delta three-dimensional (3D) printer.

This study presents a novel and distinctive delta 3D printer leveling system by designing a leveling mechanism and a leveling algorithm. The method uses a closed-loop feedback mode to make the leveling process simple, convenient and efficient without requiring major changes to the printer. The error after leveling is less than the printed layer thickness, which fully guarantees the accuracy of the leveling process.