Impact of material and energy flow variation-based iron /steel ratio on production cost

This paper establishes a model for the production cost of iron and steel enterprise.The variation rule of the production cost versus the iron/steel ratio for two cases, namely,fixed steel production and a fixed amount of molten iron,is analyzed,and the concept of a steel scrap threshold price is proposed.According to the analysis results,when the steel scrap unit price exceeds the steel scrap threshold price, an increase in the iron/steel ratio can reduce the production cost,and vice versa.When the gap between the steel scrap unit price and the steel scrap threshold price is relatively large, the impact of the iron/steel ratio on the production cost is more prominent.According to the calculation example,when steel production is fixed （284 358 t/month）and the steel scrap unit price is 263.2 yuan/t more than the steel scrap threshold price,an increase of 0.01 in the iron/steel ratio causes a monthly production cost reduction of approximately 750 000 yuan （2.63 yuan/t）.When the amount of molten iron is fixed （270 425 t/month）and the steel scrap unit price is 140.7 yuan/t more than the threshold price,an increase of 0.01 in the iron/steel ratio causes a monthly production cost reduction of approximately 430 000 yuan （1.5 yuan/t）.The results indicate that iron and steel enterprise should adjust the production strategy in time when the scrap price fluctuates, and then the production cost will be reduced.

红树林湿地模型研究进展

红树林是位于海岸潮间带的森林湿地生态系统,具有抗风削浪、保护堤岸、封存CO2缓解全球气候变化等多种功能。然而,由于地理位置及生存环境特殊,红树林湿地模型的研究相对内陆湿地滞后。为了推动红树林湿地模型的研究,本文将目前常见红树林湿地模型按功能划分为植被生长生产模型、水文模型、物流能流模型三类,以阐述相关模型研究的进展,并对目前红树林湿地模型研究提出几点看法:(1)现有红树林湿地模型在不同区域、尺度下运行的有效性有待进一步验证;(2)国内对红树林生态系统服务及植被恢复工作相关模型研究较少,今后需加强该方面的研究。