Noticing in recent years that the world is running out of mineral resources, the price of engineering materials will continually rise in the future, the percentage of the cost of manufactured part that is due to the c...Noticing in recent years that the world is running out of mineral resources, the price of engineering materials will continually rise in the future, the percentage of the cost of manufactured part that is due to the cost of materials is also rising. The amount of material must be removed away to produce the final product should be minimized, excess stock will increase not only the material cost, but also processing cost, fixture cost, tooling cost, and increases machine cycle times. This paper proposed a variant CAPP system for rotational parts based on the concept of group technology, this system accepts part features characteristics code number as an input and specify operation details for manufacturing route with the suitable primary processes required to produce the blank work piece as an output.展开更多
Six wastewater treatment plants （WWTPs） were investigated to evaluate the occurrence and removal of N-nitrosodimethylamine （NDMA）, NDMA formation potential （FP） and four specific NDMA precursors, dimethylamine ...Six wastewater treatment plants （WWTPs） were investigated to evaluate the occurrence and removal of N-nitrosodimethylamine （NDMA）, NDMA formation potential （FP） and four specific NDMA precursors, dimethylamine （DMA）, trimethylamine （TMA）, dimethyl- formamide （DMFA） and dimethylaminobenzene （DMAB）. DMA and tertiary amines with DMA functional group commonly existed in municipal wastewater. Chemically enhanced primary process （CEPP） had no effect on removal of either NDMA or NDMA FP. In WWTPs with secondary treatment processes, considerable variability was observed in the removal of NDMA （19%-85%） and NDMA FP （16%-76%）, moreover, there was no definite relationship between the removal of NDMA and NDMA FP. DMA was well removed in all the six surveyed WWTPs; its removal efficiency was greater than 97%. For the removal of tertiary amines, biologic treatment processes with nitrification and denitrification had better removal efficiency than conventional activated sludge process. The best removal efficiencies for TMA, DMFA and DMAB were 95%, 68% and 72%, respectively. CEPP could remove 73% of TMA, 23% of DMFA and 36% of DMAB. After UV disinfection, only 17% of NDMA was removed due to low dosage of UV was applied in WWTP. Although chlorination could reduce NDMA precursors, NDMA concentration was actually increased after chlorination.展开更多
文摘Noticing in recent years that the world is running out of mineral resources, the price of engineering materials will continually rise in the future, the percentage of the cost of manufactured part that is due to the cost of materials is also rising. The amount of material must be removed away to produce the final product should be minimized, excess stock will increase not only the material cost, but also processing cost, fixture cost, tooling cost, and increases machine cycle times. This paper proposed a variant CAPP system for rotational parts based on the concept of group technology, this system accepts part features characteristics code number as an input and specify operation details for manufacturing route with the suitable primary processes required to produce the blank work piece as an output.
文摘Six wastewater treatment plants （WWTPs） were investigated to evaluate the occurrence and removal of N-nitrosodimethylamine （NDMA）, NDMA formation potential （FP） and four specific NDMA precursors, dimethylamine （DMA）, trimethylamine （TMA）, dimethyl- formamide （DMFA） and dimethylaminobenzene （DMAB）. DMA and tertiary amines with DMA functional group commonly existed in municipal wastewater. Chemically enhanced primary process （CEPP） had no effect on removal of either NDMA or NDMA FP. In WWTPs with secondary treatment processes, considerable variability was observed in the removal of NDMA （19%-85%） and NDMA FP （16%-76%）, moreover, there was no definite relationship between the removal of NDMA and NDMA FP. DMA was well removed in all the six surveyed WWTPs; its removal efficiency was greater than 97%. For the removal of tertiary amines, biologic treatment processes with nitrification and denitrification had better removal efficiency than conventional activated sludge process. The best removal efficiencies for TMA, DMFA and DMAB were 95%, 68% and 72%, respectively. CEPP could remove 73% of TMA, 23% of DMFA and 36% of DMAB. After UV disinfection, only 17% of NDMA was removed due to low dosage of UV was applied in WWTP. Although chlorination could reduce NDMA precursors, NDMA concentration was actually increased after chlorination.
