热泵-热风组合干燥方式对干制海参品质的改善

为了提高干制海参的品质,该文在热风干燥的基础上,利用热泵-热风组合干燥的方式干燥腌渍海参,对不同干燥方式下海参的干燥特性(干燥特性曲线,收缩系数和产品品质)进行测定,对干燥结束后海参的复水品质(复水倍数,流变学参数,感官评价)与传统的热风干燥进行分析比较,结果表明:组合干燥海参的平均收缩系数最小,为16.64,而平均复水倍数为10.18,远高于热风干燥产品;产品流变学特性及硬度,弹性,柔韧度,黏性均较热风处理后海参理想。结果表明:组合干燥可以明显提高干燥后海参的复水倍数和复水品质,产品的感官品质好。

用于牛粪液厌氧消化的推流式和完全混合式反应器性能研究

对推流式反应器（PFR）和完全混合式反应器（CSTR）用于牛粪液厌氧消化的性能进行了比较研究.在中温35℃下,对进料浓度40、80和128 g/L的3种牛粪液分别进行了试验.结果表明,CSTR比PFR具有更好的去除VS（挥发性固体）和产生物气的性能,在进料浓度为40、80和128 g/L时,CSTR中VS去除率比PFR中分别提高了17.4%～21.5%,3.9%～21.5%和0.5%～5.3%.在最优进料浓度80 g/L下,CSTR获得了最高的容积产气率和单位VS产气量,比PFR中提高了9.8%～25.9%.研究认为,CSTR中的搅拌作用加强了微生物与物料之间物质的传递,提高了降解去除有机物和产生物气的消化效果.因此,在牛粪液厌氧消化时,推荐使用CSTR反应器.

牛粪和厨余废物不同混合比例下厌氧消化的试验研究

对不同比例的牛粪和厨余废物混合厌氧消化进行了试验研究。试验结果表明,牛粪和厨余废物的混合比例对于消化效果有显著影响。根据系统的稳定性、COD去除率和甲烷产率等进行综合考虑,确定牛粪和厨余废物中VS最佳比例为1∶1。在此比例下,其甲烷产率和COD去除率比牛粪单独消化时分别提高了76%和26.4%,去除COD的产气率为0.19L.g-1,VFA/TA比值为0.35,系统稳定性很好。当牛粪和厨余废物VS比例为1∶3和1∶6时,酸化相和甲烷相反应器中有丙酸抑制现象。本试验没有发现氨氮抑制,但是随着厨余废物比例增加,系统的稳定性变差。

杂交杨木纤维中碳水化合物的稀酸催化分离

本文采用循环式反应器研究了杂交杨木纤维中聚戊糖和聚己糖在稀酸条件下的催化分离,分别得出了聚戊糖和聚己糖稀酸水解/降解的动力学模型,以预测在不同反应条件下戊糖和己糖的水解得率。反应条件为温度140～170℃,硫酸浓度0.1%～0.9%wt,液比为6∶1。研究发现,较高的酸浓和温度对提高戊糖和己糖的得率都有利,但相同条件下聚戊糖的反应活性更高。经动力学模型优化得出,在较佳条件下有91%的聚戊糖可以以单体、低聚体及其降解产物的形式从杨木纤维中分离出来,同时超过93%的聚己糖可以以固体的形式保留在纤维中。研究表明,在适宜的稀酸催化条件下杂交杨木纤维中的碳水化合物可以得到很好的分离,为下一步戊糖和聚己糖的分别单独转化打下了基础,不仅可以充分利用木材生物质资源,而且为反应提供了相对均一的条件,从而提高反应选择性和产物的纯度。

Evaluation of a heating block system for accurate temperature-time controlled pasteurization treatments on various foods

For simulating real pasteurization treatments using hot air,hot water,radio frequency and microwave heating,a unique experimental heating block system(HBS)was developed.The stability and uniformity of sample temperatures and heating rates in HBS were determined for studying the thermal resistance of food-borne pathogens.A computer simulation model was also developed to analyze the behavior of thermal process in HBS.The results showed that the required heating rates with various set-temperatures and holding times could be easily and precisely achieved in eight selected food materials.Thermocouple and thermal imaging data showed that the good sample heating uniformity in six cells of HBS was achieved.The real temperature-time histories obtained by radio frequency energy could be approximately done in HBS by setting a number of linear regression curves.The HBS can help in more precisely characterizing the heat resistance of pathogens in foods to further develop pasteurization processes.

Correlation analysis-based image segmentation approach for automatic agriculture vehicle

It is important to segment image correctly to extract guidance information for automatic agriculture vehicle. If we can make the computer know where the crops are, we can extract the guidance line easily. Images were divided into some rec-tangle small windows, then a pair of 1-D arrays was constructed in each small windows. The correlation coefficients of every small window constructed the features to segment images. The results showed that correlation analysis is a potential approach for processing complex farmland for guidance system, and more correlation analysis methods must be researched.

Effect of intermittent aeration mode on nitrogen concentration in the water column and sediment pore water of aquaculture ponds

Nitrogen in pond sediments is a major water quality concern and can impact the productivity of aquaculture.Dissolved oxygen is an important factor for improving water quality and boosting fish growth in aquaculture ponds,and plays an important role in the conversion of ammonium-nitrogen(NH4-N)to nitrite-nitrogen(NO2--N)and eventually nitrate-nitrogen(NO3--N).A central goal of the study was to identify the best aeration method and strategy for improving water quality in aquaculture ponds.We conducted an experiment with six tanks,each with a different aeration mode to simulate the behavior of aquaculture ponds.The results show that a 36 hr aeration interval(Tc=36 hr:36 hr)and no aeration resulted in high concentrations of NH4-N in the water column.Using a 12 hr interval time(Tc=12 hr:12 hr)resulted in higher NO2--N and NO3--N concentrations than any other aeration mode.Results from an 8 hr interval time(Tc=8 hr:8 hr)and 24 hr interval time(Tc=24 hr:24 hr)were comparable with those of continuous aeration,and had the benefit of being in use for only half of the time,consequently reducing energy consumption.

Developing a screw conveyor in radio frequency systems to improve heating uniformity in granular products

Radio frequency(RF)treatments have been increasingly studied due to the rapid heating,deep power penetration depth and high energy efficiency.However,the major challenges for commercial RF applications are non-uniform and run-away heating.The purpose of this study was to improve RF heating uniformity in three granular products(soybean,corn,and peanut)using a custom-made screw conveyor with sample movement and mixing.The results showed that soybean,corn and peanut samples in the screw conveyor were RF heated in a similar heating rate under the selected electrode gap and screw rotation speed,and the variations between the highest and lowest temperatures in the three samples were all clearly reduced as compared to the stationary treatments.The RF heating uniformity index was also reduced for soybean,corn,and peanut during and after the RF treatment.Therefore,the screw conveyor could improve RF heating uniformity due to stable,continuous,uninterrupted movement and mixing of samples.The small-scale screw conveyor used in RF systems would provide a solid basis for further large-scale industrial applications.