The Possibility of Changing the Wettability of Material Surface by Adjusting Gravity

The contact angle,as a vital measured parameter of wettability of material surface,has long been in dispute whether it is affected by gravity.Herein,we measured the advancing and receding contact angles on extremely low contact angle hysteresis surfaces under different gravities(1-8G)and found that both of them decrease with the increase of the gravity.The underlying mechanism is revealed to be the contact angle hysteresis and the deformation of the liquid-vapor interface away from the solid surface caused by gradient distribution of the hydrostatic pressure.The real contact angle is not affected by gravity and cannot measured by an optical method.The measured apparent contact angles are angles of inclination of the liquid-vapor interface away from the solid surface.Furthermore,a new equation is proposed based on the balance of forces acting on the three-phase contact region,which quantitatively reveals the relation of the apparent contact angle with the interfacial tensions and gravity.This finding can provide new horizons for solving the debate on whether gravity affects the contact angle and may be useful for the accurate measurement of the contact angle and the development of a new contact angle measurement system.

Accuracy analysis of omnidirectional mobile manipulator with mecanum wheels

This article is based on the omnidirectional mobile manipulator with mecanum wheels built at Shanghai University. The article aims to find and analyze the parameters of kinematic equation of the omnidirectional system which affects its motion accuracy. The method of solving the parameter errors involves three phases. The first step is equation operation to achieve the equation of relative errors. The second step is to obtain the displacement errors of the system via experiment and combine the error results with kinematic equation deduction to solve the geometric parameter errors in two methods. The third step is to verify its validity via comparing experiments. We can then revise its kinematics equation afterwards.

Two-parameter characterization of low cycle,hysteretic fatigue data

The aim of this research is to characterize the development of fatigue damage by means of stress-strain hysteresis.Experiments were conducted on 14 specimens made of cold-finished unannealed AISI 1018 steel.Results demonstrate that the mechanical hysteresis loop areas,when plotted as a function of the number of loading cycles,show significant variations and demonstrate the three principal stages concerning the progress of the fatigue failure—initial accommodation,accretion of damage and terminal failure.These three stages of fatigue are marked by the transitions at cycles N2 and N3.Experimental results show that although fatigue life Nf ranges from 2644 cycles to 108 992 cycles,the ratios of N2/Nf and N3/Nf tend to be stable:N2/Nf=10.7%,N3/Nf=91.3%.

Erratum to“The Possibility of Changing the Wettability of Material Surface by Adjusting Gravity”

In the article titled“The Possibility of Changing the Wettability of Material Surface by Adjusting Gravity”[1],there were errors in Figure 2 which occurred during production.These errors are listed below,and the corrected version is shown as Figure 1.

Navigating Chinese cities to achieve sustainable development goals by 2030

Achieving the 17 United Nations sustainable development goals(SDGs)in China largely depends on the transition of cities toward sustainable development.However,significant knowledge gaps exist in evaluating the SDG index at the city scale and in understanding how to simulate pathways to achieve the 17 SDGs for Chinese cities by 2030.This study aimed to quantify the SDG index of 285 Chinese cities and developed a forecasting model to simulate the performance of each SDG in each city until 2030 using varied scenarios.The results indicated that although the SDG index in Chinese cities increased by 33.97%during 2005–2016,Chinese cities,which continued their past paths,achieved an average of only five SDGs by 2030.To promote the joint achievement of all SDGs,we designed different paths for all SDGs of each of the 285 cities and simulated their SDG index until 2030.Under the scenarios,216 Chinese cities(75.79%)could achieve 9–13 more SDGs in 2030 and the overall SDG index can improve from 74.57 in 2030 to 97.49(target score 100)by adopting more intensive path adjustment.We lastly determined a cost-effective path for each SDG of each city to promote joint achievement of all SDGs by 2030.The proposed simulation model and cost-effective path serve as a foundation for other countries to simulate SDG progress and develop pathways for achieving SDGs in the future.