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In response to the severe lag in tracking the response of the Stewart stability platform after adding overload, as well as the impact of nonlinear factors such as load and friction on stability accuracy, a new error attenuation function and a parallel stable platform active disturbance rejection control (ADRC) strategy combining cascade extended state observer (ESO) are proposed.

First, through kinematic modeling of the Stewart platform, the relationship between the desired pose and the control quantities of the six hydraulic cylinders is obtained. Then, a linear nonlinear disturbance observer was established to observe noise and load, to enhance the system’s anti-interference ability. Finally, verification was conducted through simulation.

Finally, stability analysis was conducted on the cascaded observer. Experiments were carried out on a parallel stable platform with six degrees of freedom involving rotation and translation. In comparison to traditional PID and ADRC control methods, the proposed control strategy not only endows the stable platform with strong antiload disturbance capability but also exhibits faster response speed and higher stability accuracy.

A new error attenuation function is designed to address the lack of smoothness at d in the error attenuation function of the ADRC controller, reducing the system ripple caused by it. Finally, a combination of linear and nonlinear ESOs is introduced to enhance the system's response speed and its ability to observe noise and load disturbances. Stability analysis of the cascade observer is carried out, and experiments are conducted on a six-degree-of-freedom parallel stable platform with both rotational and translational motion.

This study aims to investigate the impact of institutional fragility on the innovation investments of enterprises by analyzing the moderating effect of government subsidies and the integration of industry and finance.

Multiple regression analysis was used on 10,838 samples of 2,356 listed companies in China for the period 2007–2017, to empirically test the influence of institutional fragility on innovation investment. Moreover, Heckman’s two-stage approach was used for the robustness of the regression results.

The results show that the relationship between institutional fragility and innovation investment is an inverted U-shaped; government subsidies negatively moderate the relationship between institutional fragility and innovation investment, while the integration of industry and finance positively moderates them. Further analysis shows that the relationship between institutional fragility and innovation investment is more significant for high-tech enterprises. Similarly, the relationship between institutional fragility and innovation output also presents an inverted U-shape, which mainly affects enterprises’ breakthrough innovation output, but has no substantial impact on the incremental innovation output.

The conclusions provide new ideas for guiding the government’s reform, promoting the integration of industry and finance and promoting enterprise innovation.

Corporate site visits increase labor investment efficiency.

Our empirical model for the baseline analysis follows those of Jung et al. (2014) and Ghaly et al. (2020).

We show that corporate site visits are associated with significantly higher labor investment efficiency; more specifically, site visits reduce both over-hiring and under-hiring of employees. The effect of site visits on labor investment efficiency is more pronounced for firms with higher labor adjustment costs, greater financial constraints, weaker corporate governance and lower financial reporting quality. We also find that site visits mitigate labor cost stickiness.

First, while the literature has suggested how the presence of institutional investors and analysts may affect labor investment decisions, we focus on institutional investors and analysts’ activities and interactions with firm executives. We provide direct evidence that institutional investors and analysts may use corporate site visits to improve labor investment efficiency. Second, our study adds to a line of recent studies on how corporate site visits reduce information asymmetry and agency conflicts. We show that corporate site visits allow institutional investors and analysts to influence labor investment efficiency. We also provide new evidence that corporate site visits reduce labor cost stickiness.

The purpose of this paper is to develop a build strategy for inclined thin-walled parts by exploiting the inherent overhanging capability of the cold metal transfer (CMT) process, which release wire-arc additive manufacturing from tedious programming work and restriction of producible size of parts.

Inclined thin-walled parts were fabricated with vertically placed welding torch free from any auxiliary equipment. The inclined features were defined and analyzed based on the geometrical model of inclined parts. A statistical prediction model was developed to describe the dependence of inclined geometrical features on process variables. Based on these models, a build strategy was proposed to plan tool path and output process parameters. After that, the flow work was illustrated by fabricating a vase part.

The formation mechanism and regulation of inclined geometrical features were revealed by conducting experimental trials. The inclined angle can be significantly increased along with the travel speed and offset distance, whereas the wall width is mainly dependent on the ratio of wire feed speed to travel speed. In contrast to other welding process, CMT has a stronger overhanging capability, which provides the possibility to fabricate parts with large overhanging features directly with high forming accuracy.

This paper describes a novel build strategy for inclined thin-walled parts free from any auxiliary equipment. With the proposed strategy, a complex structural component can be deposited directly in the rectangular coordinates additive manufacturing system, indicating infinite possibilities on the producible size of the parts. Moreover, equipment requirements and tedious program work can also be significantly reduced.

The buried pipe element method can be used to calculate the temperature of mass concrete through highly efficient computing. However, in this method, temperatures along cooling pipes and the convection coefficient of the cooling pipe boundary should be improved to achieve higher accuracy. Thus, there is a need to propose a method for improvement.

According to the principle of heat balance and the temperature gradient characteristics of concrete around cooling pipes, a method to calculate the water temperature along cooling pipes using the buried pipe element method is proposed in this study. By comparing the results of a discrete algorithm and the buried pipe element method, it was discovered that the convection coefficient of the cooling pipe boundary for the buried pipe element method is only related to the thermal conductivity of concrete; therefore, it can be calculated by inverse analysis.

The results show that the buried pipe element method can achieve the same accuracy as the discrete method and simulate the temperature field of mass concrete with cooling pipes efficiently and accurately.

This new method can improve the calculation accuracy of the embedded element method and make the calculation results more reasonable and reliable.

The purpose of this paper is to introduce an interval finite element method (IFEM) to simulate the temperature field of mass concrete under multiple influence uncertainties e.g. environmental temperature, material properties, pouring construction and pipe cooling.

Uncertainties of the significant factors such as the ambient temperature, the adiabatic temperature rise, the placing temperature and the pipe cooling are comprehensively studied and represented as the interval numbers. Then, an IFEM equation is derived and a method for obtaining interval results based on monotonicity is also presented. To verify the proposed method, a non-adiabatic temperature rise test was carried out and subsequently simulated with the method. An excellent agreement is achieved between the simulation results and the monitoring data.

An IFEM method is proposed and a non-adiabatic temperature rise test is simulated to verify the method. The interval results are discussed and compared with monitoring data. The proposed method is found to be feasible and effective.

Compared with the traditional finite element methods, the proposed method taking the uncertainty of various factors into account and it will be helpful for engineers to gain a better understanding of the real condition.

Human-induced marine environmental noise, such as commercial shipping and seismic exploration, is concentrated in the low-frequency range. Meanwhile, low-frequency sound signals can achieve long-distance propagation in water. To meet the requirements of long-distance underwater detection and communication, this paper aims to propose an micro-electro-mechanical system (MEMS) flexible conformal hydrophone for low-frequency underwater acoustic signals. The substrate of the proposed hydrophone is polyimide, with silicon as the piezoresistive unit.

This paper proposes a MEMS heterojunction integration process for preparing flexible conformal hydrophones. In addition, sensors prepared based on this process are non-contact flexible sensors that can detect weak signals or small deformations.

The experimental results indicate that making devices with this process cannot only achieve heterogeneous integration of silicon film, metal wire and polyimide, but also allow for customized positions of the silicon film as needed. The success rate of silicon film transfer printing is over 95%. When a stress of 1 Pa is applied on the x-axis or y-axis, the maximum stress on Si as a pie-zoresistive material is above, and the average stress on the Si film is around.

The flexible conformal vector hydrophone prepared by heterogeneous integration technology provides ideas for underwater acoustic communication and signal acquisition of biomimetic flexible robotic fish.

This study aims to comprehensively investigate the relationship between government subsidies and innovation performance in Chinese enterprises listed on the SSE STAR Market.

An unbalanced sample, covering 285 observations in 215 enterprises listed on the SSE STAR Market from 2019 to 2020, was used to explore the relationships between government subsidies, R&D investment, CEO shareholding and innovation performance. Counterfactual analysis is added for robustness testing.

Empirical evidence confirms that government subsidies have an inverted U-shaped relationship with R&D investment and innovation performance. Meanwhile, R&D investment is a mediating variable between government subsidies and innovation performance. Moreover, CEO shareholding plays a moderating role between government subsidies and R&D investment. The higher the CEO ownership, the steeper the inverted U-shaped relationship.

The government should introduce a dynamic mechanism to reasonably control subsidy amounts and strengthen the supervision of subsidy use. Enterprise managers should be aware of how incentives affect the firm’s innovation and implement a coordinated development of government subsidy policies and internal enterprise governance.

This study adds new empirical evidence for the relationship between government subsidies and enterprise innovation performance. The risk incentive provided by stock options is an important micro mechanism to compensate for the lack of government subsidies. The study identifies ways to promote firm innovation based on the synergistic effect of internal and external mechanisms.

The aim of this study was to develop a new generation of automatic systems based on cutting-edge design and practical welding physics to minimize downtime caused by defects and machine faults on the barges. Automatic welding has been used frequently on offshore pipeline projects.

An automated welding robot system for sub-sea pipeline installation was constructed. The system utilized the double-car double-torch welding, which is light-weight and compact, suited for offshore applications. Several state-of-the-art technologies were integrated into the control system design, including a heterogeneous network based on EtherCAT technology, network communications based on CANopen, motor synchronization, all-position welding, etc. In addition, the utilization of the CAN bus reduced the number of cable lines and increased the extensibility of the proposed welding robot system. An internal clamp with copper shoes assured a nice root weld and narrow bevel design and the welding efficiency was improved accordingly.

The trial was carried out to verify the rationality and effectiveness of the proposed automated system. The deposition rate of the backing welding could reach 17.78 kg/h; the average time for each welding was 340 s. This system was unique in that it features a dual-torch welding head that allowed for the deposition of one run with twice as much material as a single torch head. The experiment showed that the double-vehicle double-torch mode can greatly improve the welding efficiency of pipeline installation during the welding process.

The automated welding robot system will be applied to offshore pipeline projects.

This robot is the first submarine pipeline installation welding robot to use a heterogeneous network based on EtherCAT technology. Various aspects of the submarine pipeline installation welding robot’s design and performance were discussed, including mechanical body design, control system design and welding process specification.