In order to know the influence of the cooling temperature on chilled beef, ways of cooling processing are carried on the experiments. Results show that fast precooling treatment can reduce the body surface evaporation rate of 16.5%. After fast precooling for 2 hours, then cooling for 30 hours in acid discharge room, body temperature is 9℃or less, and the pH value is less than 5.6, the color has no big change. Aerobic bacterial count is controlled in 100 CFU/cm2.

对热缩包装牛肉冰温条件下保质期内新鲜度进行了试验研究.结果表明,2种包材BB4和NT1热缩真空包装后在-2℃条件下贮藏,在贮藏时间相同的条件下,NT1比BB4包材包装牛肉的pH值、出汁率、TVB-N值和细菌总数稍高;贮藏80 d时,牛肉pH值分别为5.85和5.83,出汁率分别为3.28％和2.91％,TVB-N值分别为9.20 mg/100 g和9.04 mg/100 g,细菌总数分别为9.70×103 CFU/g和9.20×103 CFU/g.2种包装均适合冰鲜牛肉贮藏,指标符合一级鲜肉的标准.

针对一台具有螺旋进气道的点燃式甲醇发动机,采用进气道加装螺旋隔板的方式实现了EGR和新鲜充量的分开引入.应用CFD仿真软件FIRE模拟了不同EGR通入压力和通入时间下EGR分层的效果.结果表明,EGR通入压力对EGR分层影响不大,而EGR的通入时间对EGR分层效果影响很大.当新鲜充量的通入压力为80kPa,EGR的通入压力为130 kPa且EGR在290℃A BTDC(压缩上止点前)停止通入时,可实现最佳的分层效果,此时火花塞附近的EGR浓度最低,为25％,燃烧室凹坑内的EGR浓度最高,为44％,EGR分层梯度达到19％.同时,还对比分析了EGR对甲醇发动机燃烧性能的影响,发现分层EGR较均质EGR可有效地提高缸压峰值、提前燃烧始点和缩短燃烧持续期,有利于发动机燃烧性能的改善.

Separate introduction of the recycling exhaust and fresh charge of a spark ignition methanol engine was realized by installing an EGR tube in the helical intake port .The effects of different EGR access times and different combustion chamber pit shapes on EGR stratification were simulated with the CFD FIRE software .The results show that the addition of EGR tube can realize the EGR stratification and the EGR access time and the combustion chamber pit shape have significant effect on EGR stratification .The stratification of low EGR concentration around the spark plug and higher EGR concentration far from com-bustion chamber top is formed when the combustion chamber pit shows shallow cylinder shape ,the pressures of fresh charge and EGR are 100 kPa and 160 kPa respectively and the recirculation finished at 300° BTDC .The influence of stratified EGR and homogeneous EGR on in-cylinder combustion of methanol engine is analyzed based on the same EGR ratio and fuel consump-tion .The stratified EGR can improve the peak cylinder pressure ,shorten the combustion delay period and advance the combus-tion starting point effectively and is useful to improve the in-cylinder combustion of methanol engine .

Objective To explore the feasibility and safety of repairing common bile duct with laser-welding assited with glue after placing a degradable stent in it.Methods A total of 45 local healthy hybrid dogs were chosen and treated with choledochotomy.According to the primary repairing methods,the dogs were divided into three groups averagely and randomly:single suturing group(SSG),laser-welding group(LWG) and laser-welding assisted with chemical glue group(LWACGG).Before repairing,a degradable sent PLA was inserted into the common bile duct.The anastomotic time of common bile duct was recorded,measure the intention of the bursting pressure and the diameter of the anastomotic stoma were measured,the pathologic changes of the anastomotic stoma and appearance of stents were observed under electron microscope.Results Compared with the single suturing group,the anastomotic time in laser-welding group and laser-welding assisted with chemical glue group was more shorter(P<0.05); at the 1st,4 th and 12 th week after operation,there were not any significant differences of the intention of the bursting pressure between the single suturing group and laser-welding assisted with chemical glue group(P>0.05),but it in laser-welding group was more lower than those in both groups mentioned above(P<0.05).At the 4 th,12 th week after operation,the diameters of the stoma didn't dilate obviously in the laser-welding group and laser-welding assisted with chemical glue group compared with before anastomosis,but it dilated markedly in the single suturing group.Histological observation result showed less fibrosis and less inflammation reaction in the laser-welding and laser-welding assisted with chemical glue groups,but more serious inflammation could be seen in the single suturing group.The SEM photos showed the surface of the stents turned from initially smooth into rough and the cross-sections turned from compact into porous during degradation.Conclusion It is possible and safe of repairing common bile duct with laser welding assisted with chemical glue after placing a degradable stent in it.