ACTA MECHANICA SINICA The Chinese Society of Theoretical and Applied Mechanics

AIMS AND SCOPEThis journal has two independent editions—one in Chinese and the other in English.The Chinese bimonthly Acta Mechanica Sinica was first published in 1957, while the Englishquarterly, Acta Mechanica Sinica (English Series), was founded in 1985. High quality originalworks on all aspects of the science of mechanics are published in either of the editions. A

Theoretical Investigation of Influence of Mechanical Stress on Magnetic Properties of Ferromagnetic/Antiferromagnetic Bilayers Deposited on Flexible Substrates

Effect of mechanical stress on magnetic properties of an exchange-biased ferromagnetic/antiferromagnetic bilayer deposited on a flexible substrate is investigated. The hysteresis loops with different magnitudes and orientations of the stress can be classified into three types. The corresponding physical conditions for each type of the loop are deduced based on the principle of minimal energy. The equation of the critical stress is derived, which can judge whether the loops show hysteresis or not. Numerical calculations suggest that except for the magnitude of the mechanical stress, the relative orientation of the stress is also an important factor to tune the exchange bias effect.

Theoretical Prediction of the Photovoltaic Properties of BFBPD-PC61 BM System as a Promising Organic Solar Cell

In this work,the photovoltaic properties of BFBPD-PC61 BM system as a promising high-performance organic solar cell（OSC） were theoretically investigated by means of quantum chemistry and molecular dynamics calculations coupled with the incoherent charge-hopping model.Moreover,the hole carrier mobility of BFBPD thin-film was also estimated with the aid of an amorphous cell including 100 BFBPD molecules.Results revealed that the BFBPD-PC61 BM system possesses a middle-sized open-circuit voltage of 0.70 V,large short-circuit current density of 17.26 mA ·cm^-2,high fill factor of 0.846,and power conversion efficiency of 10%.With the Marcus model,in the BFBPD-PC61 BM interface,the exciton-dissociation rate,kdis,was predicted to be 2.684×10^13 s^-1,which is as 3-5 orders of magnitude large as the decay（radiative and non-radiative） one（10-8-10^10s^-1）,indicating a high exciton-dissociation efficiency of 100% in the BFBPD-PC61 BM interface.Furthermore,by the molecular dynamics simulation,the hole mobility of BFBPD thin-film was predicted to be as high as 1.265 × 10^-2 cm-2·V^-1·s^-1,which can be attributed to its dense packing in solid state.

THEORETICAL STUDIES ON THE REACTION MECHANISM OF AMMONIA WITH FORMALDEHY DE

The reaction mechanism of ammonia with formaldehyde was investigated by using the intrinsic reaction coordinate(IRC)method on the ab initio RHF/STO-3G basis set. our results indicate that the reaction proceeds in two stages:the first step yields the molecular complex and the second one is the rearrangement from molecular complex to the reaction proauct.

MODELLING OF MECHANICAL MECHANISM OF CHROMATOGRAPHIC SYSTEM AND THEORETICAL EQUATIONS SHOWING DYNAMICAL CHARACTERISTICS OF CHROMATOGRAPHY

A simple model of chromatographic mechanical mechanism is present, and then a scrics of theoretical chromatographic equations and fundamental Formulae are derived. These theoretical equations and formulae not only reserve thermodynamic characteristics in the current fundamental chromatographic formulae, but also introduce one or more kinetic parameter, so it is possible to make the macroscopic-control on the effect of kinetic characteristics on chromatographic system.

Theoretical Mechanisms and Suggestions for Fostering the Economic Resilience of Chinese Cities from the Perspective of Urban Social Networks

Uncertainties are becoming more and more diverse around the world,and risks and impacts affecting the healthy development of cities are increasing.Fostering urban social resilience is not only a proactive countermeasure to growing external pressures and potential impacts,but also an important starting point for growth.This article analyzes the impact mechanisms of three important types of urban social networks-degree centrality(DC),closeness centrality(CC),and betweenness centrality(BC)-between residents,and organizations on the economic resilience of cities from the perspective of social networks.It summarizes the challenges faced in enhancing economic resilience under the social network perspective,including unbalanced resource allocation,sparse social contact networks,weak social bottom lines,lack of social trust,and insufficient innovation capabilities.On this basis,this article makes suggestions such as strengthening the construction of social networks,promoting urban economic restructuring to enhance the adaptability and innovation capabilities of cities,fostering diverse urban social networks,optimizing information dissemination mechanisms,strengthening the construction of urban social credit systems,and improving the social security system in order to fostering the resilience of through the perspective of social networks.

Analytical study of wrinkling in thin-film-on-elastomer system with finite substrate thickness

Surface wrinkling, a film bonded on a pre-strained elastomeric substrate can form periodic wrinkling patterns, is a common phenomenon in daily life. In existing theoretical models, the film is much thinner than the substrate so that the substrate can be considered to be elastomeric with infinite thickness. In this paper, the effect of finite substrate thickness is analyzed theoretically for free boundary condition cases. Based on the minimum potential energy principle, a theoretical model is established, and the wave length and amplitude of the wrinkling pattern are obtained. When the thickness of the substrate is more than 200 times larger than the thickness of the film, the results of this study agree well with the results obtained from the previous models for infinite substrate thickness. However, for thin substrates, the effect of finite substrate thickness becomes significant. The model given in this paper accurately describes the effect of finite substrate thickness, providing important design guidelines for future thin-film-on-substrate systems such as stretchable electronic devices.

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Teoretical ＆ Applied Mechanics Letters, Vol. 5, Issue 1, January 2015Investigation of a transonic separating/reattaching shear layer by means of PIV S. Scharnowski, C.J KalerThe separating/reattaching flow over an axisymmetric backward-facing step is analyzed experimentally by means of particle image velocimetry. The main pur- pose of the measurements is the investigation of the mean flow field as well as of the Reynolds stress distributions at Ma.7 and at Re33 × 10 5ed on the step height. Due to the strong progress of optical flow measurements in the last years it was possible to resolve all flow scales down to 180 μm （≈ 1% step height） with high precision. It was found for the first time that the Reynolds stress distribution features a local minimum between the first part of the shear layer and a region inside the recirculation region.

Does the transformation of energy structure promote green technological innovation?A quasi-natural experiment based on new energy demonstration city construction

New energy development is essential to achieving carbon peaks and neutrality and promoting green technological innovation.Identifying the causal relationship between new energy demonstration city construction and green technological innovation is crucial for the expansion and promotion of new energy demonstration cities.In this study,we take the construction of new energy demonstration cities as a quasi-natural experiment,study their impact on green technological innovation using difference-indifference(DID),and conduct a robustness test using DID after propensity score matching(PSM-DID).The research results indicate the following:First,energy structure optimization can significantly improve the level of urban green technological innovation(this result was shown to be valid using PSM-DID and other tests involving the effects of placebo and instrumental variables).Second,new energy demonstration city construction mainly improves the level of urban green technological innovation through technology research and development,the improvement of the industrial innovation environment,and the promotion of environmental performance.Third,the impact of energy structure optimization on green technological innovation has regional,financial,and economic development heterogeneity.Finally,new energy demonstration city policy affects the flow of capital,labor,technology,and other production factors to pilot areas according to new energy demonstration city policy,forming a“siphon effect”.The carbon reduction effect of new energy demonstration city construction is greater than its pollution reduction effect.Given the results of the study,policy recommendations to promote the expansion of new energy demonstration cities are proposed.

Theoretical analysis and experimental research on non-cavitation noise modulation mechanism of underwater counter-rotation propeller

The underwater counter-rotation propeller non-cavitation noise has an obvious mod- ulation characteristic which is due to the interaction of flow and blade. A modulation mecha- nism is presented in this paper. A sound pressure spectrum model is presented to describe its non-cavitation noise with application of generalized acoustic analogy method, the modulation mechanism is expressed with the improvement of sound pressure model. The power spectrum and modulation spectrum are presented by numerical simulation. Theoretical analysis and nu- merical simulation results are verified by the cavitation tunnel experiment. The modulation model of counter-rotation propeller is beneficial to the prediction modulation characteristics and identification of underwater high-speed vehicles.