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This paper aims to study numerically the influence of the applied laser energy density and the porosity of the powder bed on the thermal behavior of the melt and the resultant instability of the liquid track.

A three-dimensional model was proposed to predict local powder melting process. The model accounts for heat transfer, melting, solidification and evaporation in granular system at particle scale. The proposed model has been proved to be a good approach for the simulation of the laser melting process.

The results shows that the applied laser energy density has a significantly influence on the shape of the molten pool and the local thermal properties. The relative low or high input laser energy density has the main negative impact on the stability of the scan track. Decreasing the porosity of the powder bed lowers the heat dissipation in the downward direction, resulting in a shallower melt pool, whereas pushing results in improvement in liquid track quality.

The randomly packed powder bed is calculated using discrete element method. The powder particle information including particle size distribution and packing density is taken into account in placement of individual particles. The effect of volumetric shrinkage and evaporation is considered in numerical model.

In the context of China, the purpose of this paper is to empirically answer three related questions: Could circular agriculture (CA) attain economic, ecological and social benefits simultaneously? What is key to a successful CA business in emerging economies? And who plays the vital role in building and sustaining a circular business?

The paper is based on a field study and looks at a farm in China. It uses a triangulation methodology to collect information. Besides longitudinal filed work at the farm, the researchers have also interviewed multiple stakeholders and conducted field research at the local markets.

With concrete performance data, the study proves that a circular approach can help achieve ecological, economic and social goals together. It shows that economic viability is essential to succeeding in circular operation, sufficient production pathways are required to make such operation sustainable, and entrepreneurship is key to build and grow a circular business.

The findings point to the crucial role of entrepreneurship in promoting the circular model in emerging economies. These findings, however, may not be readily generalizable, given the limitations of the case study approach.

The study highlights a few areas in which government assistance can make a difference, including financial incentives, information provision, technical support and most importantly the creation of a positive environment for entrepreneurial development.

While prior research emphasizes the role of government in promoting circular economy in developing and emerging markets, the study proves that entrepreneurship is key to turning government initiatives into economically viable and sustainable circular operation.