Study of corrective abrasive finishing for plane surfaces using magnetic abrasive finishing processes

On the basis of ordinary plane magnetic abrasive finishing,a finishing method is proposed that can improve the flatness of a plane workpiece.In this method,the feed speed is varied during finishing according to the profile curve of the initial surface and the material removal efficiency,to control the effective finishing time in different areas and thereby improve the surface flatness.A small magnetic pole with an end face diameter of 1 mm is designed,and a ferromagnetic plate is placed under the workpiece to improve the uniformity of the magnetic field distribution near the magnetic pole.An experiment on an A5052 aluminum alloy plate workpiece shows that after 60 min of finishing using the proposed method,the extreme difference of the workpiece surface can be reduced from 14.317μm to 2.18μm,and the standard deviation can be reduced from 3.322μm to 0.417μm.At the same time,according to the measurement results,a similar flatness can be achieved at different positions on the finishing area.Thus,the proposed variable-speed finishing method leads to obvious improvements in flatness.

Influences of dietary protein sources and crude protein levels on intracellular free amino acid profile in the longissimus dorsi muscle of finishing gilts

Background： The current study was carried out to determine effects of dietary protein source and crude protein（CP）level on carcass characteristics, meat quality, and muscle amino acid（AA） profile in finishing gilts. The experiment was designed as a 2 × 2 factorial arrangement with two sources of dietary proteins（cottonseed meal, CSM vs. soybean meal, SBM） and two levels of CP（12 % vs. 14 %, as-fed basis）. Seventy-two crossbred gilts（89.5 ± 0.9 kg） were allotted to one of four dietary treatments in a randomized complete block design for a period of 28 d. All diets were formulated to be isoenergetic and similar concentrations of standardized ileal digestible essential AA covering the nutrient requirements of pigs.Results： Growth, carcass characteristics and meat quality were not affected by dietary protein source nor crude protein level（P ＆gt; 0.10） except that average daily feed intake was increased by CSM diets（P = 0.03）. Gilts offered reduced protein diets had lower muscle p H45min（P 〈 0.05）. Neither dietary protein source nor crude protein level influenced N deposition. However, reduced protein diets decreased N intake, N excretion, and serum urea nitrogen content, whilst improved N efficiency（P 〈 0.01）. CSM diets increased N intake（P = 0.04）,but did not depress N efficiency. The concentrations of phenylalanine, tryptophan, cysteine and tyrosine（P 〈 0.05） of the longissimus muscle were decreased when gilts offered CSM diets, while muscle intracellular free valine concentration was increased（P = 0.03）. The gilts offered reduced protein diets had greater intracellular concentrations of free methionine, lysine, and total AA in muscle（P 〈 0.05）.Conclusion： These results suggest that CSM could replace SBM as a primary protein source in finishing pig diets in terms of performance, N efficiency, carcass characteristics, and meat quality, but decrease the concentrations of muscle specific AA. Furthermore, the reduced protein diet played an important role in increasing muscle intracellular concentrations of specific free amino acids（FAA）, and in reducing the relative ratios of specific FAA to lysine in longissimus dorsi muscle of pig, whose biological meaning needs further studies.