Many-body dissipative particle dynamics with energy conservation:temperature-dependent long-term attractive interaction

Heat and mass transfer during the process of liquid droplet dynamic behaviors has attracted much attention in decades.At mesoscopic scale,numerical simulations of liquid droplets motion,such as impacting,sliding,and coalescence,have been widely studied by using the particle-based method named many-body dissipative particle dynamics(MDPD).However,the detailed information on heat transfer needs further description.This paper develops a modified MDPD with energy conservation(MDPDE)by introducing a temperature-dependent long-term attractive interaction.By fitting or deriving the expressions of the strength of the attractive force,the exponent of the weight function in the dissipative force,and the mesoscopic heat friction coefficient about temperature,we calculate the viscosity,self-diffusivity,thermal conductivity,and surface tension,and obtain the Schmidt number Sc,the Prandtl number P r,and the Ohnesorge number Oh for 273 K to 373 K.The simulation data of MDPDE coincide well with the experimental data of water,indicating that our model can be used to simulate the dynamic behaviors of liquid water.Furthermore,we compare the equilibrium contact angle of droplets wetting on solid surfaces with that calculated from three interfacial tensions by MDPDE simulations.The coincident results not only stand for the validation of Young’s equation at mesoscale,but manifest the reliability of our MDPDE model and applicability to the cases with free surfaces.Our model can be extended to study the multiphase flow withcomplex heat and mass transfer.

Coupled Dynamic Modeling of Rolls Model and Metal Model for Four High Mill Based on Strip Crown Control

The crown is a key quality index of strip and plate, the rolling mill system is a complex nonlinear system, the strip qualities are directly affected by the dynamic characteristics of the rolling mil. At present, the studies about the dynamic modeling of the rolling mill system mainly focus on the dynamic simulation for the strip thickness control system, the dynamic characteristics of the strip along the width direction and that of the rolls along axial direction are not considered. In order to study the dynamic changes of strip crown in the roiling process, the dynamic simulation model based on strip crown control is established. The work roll and backup roll are considered as elastic continuous bodies and the work roll and backup roll are joined by a Winkler elastic layer. The rolls are considered as double freely supported beams. The change rate of roll gap is taken into consideration in the metal deformation, based on the principle of dynamic conservation of material flow, the two dimensional dynamic model of metal is established. The model of metal deformation provides exciting force for the rolls dynamic model, and the roils dynamic model and metal deformation model couple together. Then, based on the two models, the dynamic model of rolling mill system based on strip crown control is established. The Newmark-13 method is used to solve the problem, and the dynamic changes of these parameters are obtained as follows： （1） The bending of work roll and backup roll changes with time; （2） The strip crown changes with time; （3） The distribution of rolling force changes with time. Take some cold tandem rolling mill as subject investigated, simulation results and the comparisons with experimental results show that the dynamic model built is rational and correct. The proposed research provides effective theory for optimization of device and technological parameters and development of new technology, plays an important role to improve the strip control precision and strip shape quality.

Cluster synchronization of community network with distributed time delays via impulsive control

Cluster synchronization is an important dynamical behavior in community networks and deserves further investigations.A community network with distributed time delays is investigated in this paper.For achieving cluster synchronization,an impulsive control scheme is introduced to design proper controllers and an adaptive strategy is adopted to make the impulsive controllers unified for different networks.Through taking advantage of the linear matrix inequality technique and constructing Lyapunov functions,some synchronization criteria with respect to the impulsive gains,instants,and system parameters without adaptive strategy are obtained and generalized to the adaptive case.Finally,numerical examples are presented to demonstrate the effectiveness of the theoretical results.

GENERALIZED NOETHER’S THEOREM OF NONHOLONOMIC NONPOTENTIAL SYSTEM IN NONINERTIAL REFERENCE FRAMES

The new Lagrangian of the relative motion of mechanical system is constructed, the varialional principles oj Jourdain's form of nonlinear nonlwlonomic nonpotential system in noninertial reference frame are established, the generalized Noether's theorem of the system above is presented and proved, and the conserved quantities of system are studied.

Responding to common questions on the conservation of agricultural heritage systems in China

Although the urgency of their conservation has been recognized, Globally Important Agricultural Heritage Systems(GIAHS) designated by the Food and Agriculture Organization(FAO) since 2002 and China Nationally Important Agricultural Heritage Systems(ChinaNIAHS) certified by the Ministry of Agriculture(MOA) of China since 2012 are faced with questions as to why to conserve them, what is to be conserved, who should conserve them, and how? This paper attempts to clarify and respond to such questions focusing on the conservation of agricultural heritage systems in China based on a review of both theoretical and practical progress. Agricultural heritage systems exhibit a multitude of values for sustainable and equitable development and therefore should be conserved for both present and future generations. Unlike most conventional heritages, the conservation of agricultural heritage systems is a complex, systematic "engineering" in which both physical and biological components and associated socio-cultural processes should be conserved in a dynamic way. Farmers and heritage sites must benefit from the continuance of traditional agricultural production under the premise of ecological functions being sustained and traditional culture being inherited. For a more effective conservation, a multi- stakeholder process should be established involving governments at different levels, multi-disciplinary scientists, communities and farmers, and business enterprises as well as social organizations. As has been demonstrated, the conservation of agricultural heritage systems aims to promote the regional sustainable development, to improve the livelihood, food security and well-being of farm people, and to provide references for the development of modern agriculture in China.

Conservation and Adaptive Management of Globally Important Agricultural Heritage Systems (GIAHS)

Worldwide specific agricultural systems and landscapes have been created, shaped and maintained by generations of farmers and herders based on diverse natural resources using locally adapted management practices. Building on local knowledge and experience these ingenious agricultural systems reflect the evolution of humankind, the diversity of its knowledge and its profound relationship with nature. These systems have resulted not only in outstanding landscapes maintenance and adaptation of globally significant agricultural biodiversity indigenous knowledge systems and resilient ecosystems, but above all, in the sustained provision of multiple goods and services, food and livelihood security and quality of life. However, many of these systems are facing severe threats from various sources including globalization. In 2002 FAO initiated an international partnership initiative： ＂conservation and adaptive management of Globally Important Agricultural Heritage Systems （GIAHS）＂. The global GIAHS initiative aims to establish the basis for the international recognition, dynamic conservation and sustainable management of such systems, agricultural biodiversity and their associated biodiversity knowledge systems, food and livelihood security, landscapes and cultures.

Conservation of Traditional Agriculture as Living Knowledge Systems,Not Cultural Relics

Agricultural heritage has potential significance far beyond its common representation as the ＂traditional＂ system of ＂traditional peoples＂.The U.N.Food and Agricultural Organization＇s Globally Important Agricultural Heritage Systems（GIAHS） program is an important designation that treats heritage agro-ecosystems as living systems,rather than cultural relics.In order for the GIAHS designation to achieve its full potential,however,the role of human knowledge within the continuous cultural and ecological evolution of GIAHS requires much closer examination and appreciation.This paper explores the limits of contemporary nature and cultural conservation,and draws on a coevolutionary theoretical framework in order to better conceptualize the dynamism of such complex agro-ecological systems.In such a view,GIAHS can be seen as evolving systems of sustainable agriculture of great potentail relevance to contemporary society-environment challenges,rather than as relics of the past.

A system dynamics urban water management model for Macao, China

Urban water resources have been facing significant pressure from population growth, urbanization, and climate change. A system dynamics urban water management model was proposed to simulate the dynamic interactions between urban water demands and society, economy, climate, and water conservation. The residents＇ water conseration willingness was incorporated in the model and water-saving effects were quantified. The simulation results for Macao showed that population size was the main driving force for urban water demand. The change of temperature and precipitation has obvious effects on the landscape water demand. The water demand output is sensitive to the change in population, per capita demand, and temperature. Increased precipitation will reduce urban water demand and increased economic growth will increase water demand. By implementing integrated water conservation measures and imoroved water conservation willinmaess, water demand could be reduced bv 17.5%.