Search results

The purpose of this paper is to present recent work designing a mechanical robotic hand for self‐adaptive grasping, human‐like appearance, which can be used in a humanoid robot. Conventional robotic devices are relatively complex, large, cumbersome and difficult to be installed in a humanoid robot arm. Under‐actuated robot hands use less motors to drive more rotating joints, thus to simplify the mechanical structure, decrease the volume and weight and finally lower the difficulty of control and the cost.

A novel under‐actuated finger mechanism is designed, which is based on a gear‐rack mechanism, spring constraint and an active sleeve middle phalanx. The principle analyses of its self‐adaptive grasp and end power grasping are given. A new multi‐fingered hand named as TH‐3R Hand is designed based on the finger.

The design finger mechanism can be used in a robotic hand to make the hand obtain more degrees of freedom (DOF) with fewer actuators, and good grasping function of shape adaptation, decrease the requirement of control system. TH‐3R Hand has five fingers, 15 DOF. All fingers are similar. TH‐3R Hand has many advantages: it is simple in structure, light in weight, easy to control and low in cost. TH‐3R Hand can passively adapt different shapes and sizes of the grasped object. Experimental studies have demonstrated the self‐adaptation in grasping of the finger.

The implication of this research is that under‐actuated robotic hands are appropriate for the missions of grasping different objects. The limitation of the research to date is that issues of sensors, control, and communication have not yet been addressed.

Key technologies of the under‐actuated finger and TH‐3R Hand, with self‐adaptive grasping, human‐like appearance and low‐cost lightweight, are feasible. These technologies have the potential to make a significant impact.

These results present a self‐adaptive under‐actuated grasp concept and a humanoid robotic hand with under‐actuated gear‐rack mechanism.

To explore the economical and reasonable semi-rigid permeable base layer ratio, solve the problems caused by rainwater washing over the pavement base layer on the slope, improve its drainage function, improve the water stability and service life of the roadbed pavement and promote the application of semi-rigid permeable base layer materials in the construction of asphalt pavement in cold regions.

In this study, three semi-rigid base course materials were designed, the mechanical strength and drainage properties were tested and the effect and correlation of air voids on their performance indexes were analyzed.

It was found that increasing the cement content increased the strength but reduced the air voids and water permeability coefficient. The permeability performance of the sandless material was superior to the dense; the performance of the two sandless materials was basically the same when the cement content was 7%. Overall, the skeleton void (sand-containing) type gradation between the sandless and dense types is more suitable as permeable semi-rigid base material; its gradation is relatively continuous, with cement content? 4.5%, strength? 1.5 MPa, water permeability coefficient? 0.8 cm/s and voids of 18–20%.

The study of permeable semi-rigid base material with large air voids could help to solve the problems of water damage and freeze-thaw damage of the base layer of asphalt pavements in cold regions and ensure the comfort and durability of asphalt pavements while having good economic and social benefits.

This study aims to address the challenge of the real-time state of charge (SOC) estimation for lithium-ion batteries in robotic systems, which is critical for monitoring remaining battery power, planning task execution, conserving energy and extending battery lifespan.

The authors introduced an optimal observer based on adaptive dynamic programming for online SOC estimation, leveraging a second-order resistor–capacitor model for the battery. The model parameters were determined by fitting an exponential function to the voltage response from pulse current discharges, and the observer's effectiveness was verified through extensive experimentation.

The proposed optimal observer demonstrated significant improvements in SOC estimation accuracy, robustness and real-time performance, outperforming traditional methods by minimizing estimation errors and eliminating the need for iterative steps in the adaptive critic and actor updates.

This study contributes a novel approach to SOC estimation using an optimal observer that optimizes the observer design by minimizing estimation errors. This method enhances the robustness of SOC estimation against observation errors and uncertainties in battery behavior, representing a significant advancement in battery management technology for robotic applications.

The purpose of the present study is to develop a new numerical framework that can predict the supersonic base flow more accurately, including the development of axisymmetrically separated shear layer and recompression shock. To this end, two aspects are improved and combined, i.e. a newly self-adaptive turbulence eddy simulation (SATES) turbulence modeling method and a high-order discretization numerical scheme. Furthermore, the performance of the new numerical framework within a general-purpose PHengLEI software is assessed in detail.

Satisfactory prediction of the supersonic separated shear layer with unsteady wake flow is quite challenging. By using a unified turbulence model called SATES combining high-order accurate discretization numerical schemes, the present study first assesses the performance of newly developed SATES for supersonic axisymmetric separation flows. A high-order finite differencing-based compressible computational fluid dynamics (CFD) code called PHengLEI is developed and several different numerical schemes are used to investigate the effects on shock-turbulence interactions, which include the monotonic upstream-centered scheme for conservation laws (MUSCL), weighted compact nonlinear scheme (WCNS) and hybrid cell-edge and cell-node dissipative compact scheme (HDCS).

Compared with the available experimental data and the numerical predictions, the results of SATES by using high-order accurate WCNS or HDCS schemes agree better with the experiments than the results by using the MUSCL scheme. The WCNS and HDCS can also significantly improve the prediction of flow physics in terms of the instability of the annular shear layer and the evolution of the turbulent wake.

The small deviations in the recirculation region can be found between the present numerical results and experimental data, which could be caused by the inaccurate incoming boundary layer condition and compressible effects. Therefore, a proper incoming boundary layer condition with turbulent fluctuations and compressibility effects need to be considered to further improve the accuracy of simulations.

The present study evaluates a high-order discretization-based SATES turbulence model for supersonic separation flows, which is quite valuable for improving the calculation accuracy of aeronautics applications, especially in supersonic conditions.

For the first time, the newly developed SATES turbulence modeling method combining the high-order accurate WCNS or HDCS numerical schemes is implemented on the PHengLEI software and successfully applied for the simulations of supersonic separation flows, and satisfactory results are obtained. The unsteady evolutions of the supersonic annular shear layer are analyzed, and the hairpin vortex structures are found in the simulation.

In order to reduce the impact of bridge construction on traffic under the bridge, the construction of bridges for some important traffic nodes usually adopts the swivel construction method. The spherical hinge is a rotating mechanism located between the bottom of the pier and the bridge cap, and is subjected to tremendous vertical pressure. According to the mechanical characteristics of the spherical hinges, this paper applies the ultra-high performance concrete (UHPC) material to the spherical hinge. The spherical hinge is subjected to a compression test to test its mechanical behavior. This paper aims to discuss this issue.

In order to test the mechanical behavior of the UHPC spherical hinge, multiple sets of 100 mm UHPC spherical hinge specimens were prefabricated. Through the universal testing machine to measure the compressive strength of specimens, draw the force-displacement curve to analyze the failure mechanism and establish the stress calculation formula of the spherical hinge at each point along the radial direction.

Through the test, the compressive strength of UHPC spherical hinge is obtained, and the influencing factors of UHPC spherical hinge strength are found: reducing water–cement ratio, increasing steel fiber content and length and changing steel fiber arrangement direction can effectively improve the compression strength of UHPC spherical hinge.

For the first time, UHPC materials were applied to the spherical hinge structure, the UHPC spherical hinge diameter is 1/3 of the diameter of the reinforced concrete spherical hinge, which is equivalent to the diameter of the steel spherical hinge. By applying the UHPC spherical hinge, the manufacturing cost is reduced, the process is simple, and the construction difficulty is reduced.

There are two opposite views about whether the Antitrust Law is conducive to the development of the economy. One view is that the Antitrust Law can restrain monopoly, maintain market competition and benefit economic growth. The other view is that the Antitrust Law inhibits innovation by monopolistic firms and fosters rent-seeking, which is bad for economic growth. To provide a possible perspective for clarifying the controversy, this paper aims to answer the following two questions: first, will the Antitrust Law inhibit corporate innovation? Second, does the antitrust enforcement agency discriminate against private enterprises?

Based on the samples of A-share listed companies from 2003 to 2013, the authors use the implementation of China’s Antitrust Law in 2008 as a policy shock, take the monopoly enterprises in each industry as the treatment group and competitive enterprises as the control group, using the difference-in-differences method to test the impact of the implementation of the Antitrust Law on corporate innovation activities.

The results show that compared with competitive enterprises, the patent output of monopolistic enterprises was significantly reduced after the implementation of the Antitrust Law, which indicates that the Antitrust Law does inhibit the innovation activities of monopolistic enterprises. Further research finds that the innovation suppression effect of the Antitrust Law is more prominent in state-owned enterprises, which means that the government does not have “selective law enforcement” against private enterprises in the process of law enforcement. Therefore, the results provide evidence for the idea that government intervention is neutral.

First, the paper enriches and expands the research on the factors affecting corporate innovation from the perspective of market structure. Second, it enriches and expands relevant research on the consequences of implementing the Antitrust Law from the perspective of corporate innovation. Third, it not only provides the relevant empirical evidence for clarifying the dispute about the Antitrust Law but also is helpful to clarify whether the Chinese Government has “selective law enforcement” against private enterprises.

This paper aims to explain the main empirical facts of housing markets, notably the trade-off between housing price and time-on-the-market, the positive correlation between housing price and the number of contracts traded during a given period (i.e. the trading volume) and the existence of price dispersion.

This theoretical paper makes use of a search and matching model. Search and matching, indeed, are two fundamental characteristics of the trading process in the housing market, and, thus, the search-and-matching models have become the new economic approach to the analysis of real estate markets.

This paper shows that a slightly modified version of the baseline search and matching model à la Mortensen-Pissarides can explain the main empirical facts of housing markets. There are two key mechanisms that allow to achieve this notable goal: a simple formalisation of the (reasonable) assumption that buyers today are potential sellers tomorrow (and vice versa); and the direct relationship between market tightness and house price, derived by the standard matching model and underestimated by the related literature.

The developed theoretical model only studies the equilibrium conditions. Indeed, it would be interesting to also study the disequilibrium in housing markets.

The explanation of the main empirical facts of housing markets is embodied in the same and relatively simple theoretical model.

In addition to the explanation of the main empirical facts of housing markets, the developed theoretical model can generate an upward sloping Beveridge curve in the housing market (the positive relation between home-seekers and vacant houses). Instead, according to a recent criticism in the related literature, a model à la Mortensen-Pissarides inherently generates a (empirically unrealistic) downward sloping Beveridge curve.

Although extant studies have investigated the antecedents of negative electronic word of mouth (eWOM), they treated it as a unidimensional concept without classification. To bridge this knowledge gap, this paper distinguishes rational negative eWOM (RNW) from emotional negative eWOM (ENW) and leverages the consumer value framework to investigate their drivers in the context of peer-to-peer accommodation platforms (PPAPs).

This study collected data through an online survey of 437 PPAP users. Partial least squares (PLS) were used to validate the proposed hypotheses. Further, the path coefficients comparison method was adopted to distinguish the different impacts of consumer values on RNW and ENW.

This research showed that self-presentation exerted a positive impact on RNW, but its relationship with ENW was insignificant. Anger and regret were, respectively, positively related to ENW and RNW. Besides, altruism exerted a positive effect on RNW, whereas it had a negative effect on ENW.

First, this paper makes a fresh attempt to categorize negative eWOM into RNW and ENW. Second, this paper draws upon the consumer value framework to dissect varied motivations for posting RNW versus ENW on PPAPs. Third, this paper empirically verifies the differential influences that consumer values exert on RNW and ENW.

Among the many influencing effects that the medium has on the CO₂ corrosion of carbon steel, flow is one of the most important because it can determine the formation of corrosion product scales and its stabilisation, thus influencing the attack morphology and corrosion rate. This paper aims to summarise some factors affecting aqueous CO₂ corrosion and the laboratory methodologies to evaluate one of the most important, the flow, with an emphasis on less costly rotating cage (RC) laboratory methodology.

Regarding the key factors affecting CO₂ corrosion, both well-established factors and some not well addressed in current corrosion prediction models are presented. The wall shear stress (WSS) values that can be obtained by laboratory flow simulation methodologies in pipelines and its effects over iron carbonate (FeCO₃) scales or inhibition films are discussed. In addition, promising applications of electrochemical techniques coupled to RC methodology under mild or harsh conditions are presented.

More studies could be addressed that also consider both the salting-out effects and the presence of oxygen in CO₂ corrosion. The RC methodology may be appropriate to simulate a WSS close to that obtained by laboratory flow loops, especially when using only water as the corrosive medium.

The WSS generated by the RC methodology might not be able to cause destruction of protective FeCO₃ scales or inhibition films. However, this may be an issue even when using methodologies that allow high-magnitude hydrodynamic stresses.