表面更新釜中粘弹性流体的脱挥特性测定

出于消化引进及自行开发聚合物系脱挥设备的需要,对粘弹性流体在双轴表面更新釜中装带刮刀的眼镜型桨及圆盘桨时脱挥性能进行了实验研究。用氧探头技术测定液侧容积传质系数k_La。结果表明,在扩散脱挥区域,粘弹性对容积传质系数无明显影响;装料量对k_La有显著的影响;带刮刀的眼镜型桨的脱挥性能优于圆盘桨。将实验结果在广泛的条件下进行了关联。

Ammonia Volatilization and Deriitrification Losses from an Irrigated Maize-Wheat Rotation Field in the North China Plain

Ammonia (NH3) volatilization, denitrification loss, and nitrous oxide (N2O) emission were investigated from an irrigated wheat-maize rotation field on the North China Plain, and the magnitude of gaseous N loss from denitrification and NH3 volatilization was assessed. The micrometeorological gradient diffusion method in conjunction with a Bowen Ratio system was utilized to measure actual NH3 fluxes over a large area, while the acetylene inhibition technique (intact soil cores) was employed for measurement of denitrification losses and N2O emissions. Ammonia volatilization loss was 26.62% of the applied fertilizer nitrogen (N) under maize, while 0.90% and 15.55% were lost from the wheat field at sowing and topdressing, respectively. The differences in NH3 volatilization between different measurement events may be due to differences between the fertilization methods, and to differences in climatic conditions such as soil temperature.Denitrification losses in the fertilized plots were 0.67%-2.87% and 0.31%-0.49% of the applied fertilizer N under maize and wheat after subtracting those of the controls, respectively. Nitrous oxide emissions in the fertilized plots were approximately 0.08%-0.41% and 0.26%-0.34% of the applied fertilizer N over the maize and wheat seasons after subtracting those of the controls, correspondingly. The fertilizer N losses due to NH3 volatilization were markedly higher than those through denitrification and nitrous oxide emissions. These results indicated that NH3 volatilization was an important N transformation in the crop-soil system and was likely to be the major cause of low efficiencies with N fertilizer in the study area. Denitrification was not a very important pathway of N fertilizer loss, but did result in important evolution of the greenhouse gas N2O and the effect of N2O emitted from agricultural fields on environment should not be overlooked.

A Mass Transfer Model for Devolatilization of Highly Viscous Media in Rotating Packed Bed

A mass transfer model for devolatilization process of highly viscous media in rotating packed bed(RPB) was developed based on penetration theory and mass conservation.Before establishing the model,some mass transfer experiments of thin film were conducted in a designed diffusion cell including vacuum and feeding system. In this study,acetone was used as the volatile organic compound(VOC) and syrup as the highly viscous media.The thickness of thin film was changed by using different liquid distributor.It was found that bubbling played an important role in the devolatilization.The correlation of diffusion coefficient of acetone in highly viscous dilute solution was proposed.The relative error between predicted and experimental data was within the range of ± 30% for diffusion coefficient of acetone in syrup.A comparison of experimental data of RPB with model indicated that the relative error was within ± 30% for efficiency of acetone removal.

Allium sativum Flavor Compounds as an Indicator for Garlic Identity and Quality Determination

The objective of the study was to research the aroma profile of volatile compounds in garlic subspecies originating from Latvia, and compare them with the aroma composition of garlic grown in the region of Midi-Pyrenees （France）. It was established that hard-neck garlic tends to contain more diallyl disulfide （DADS）, the main decomposition product of allicin. Compared to the hard-neck subspecies, the content of allyl mercaptan, one of the major compounds producing the strong odor detectable after ingestion of garlic, was significantly lower in the soft-neck garlic clones. The amount of cyclic compound 3-vinyl-1,2-dithiin differed considerably with higher contents in the soft-neck subspecies. The results also demonstrate the soft-neck garlic as a more suitable subspecies for long-term storage. In general, the results show no significant difference in the content of DADS and the total content of other flavor compounds between hard-neck and soft-neck garlic grown in the region of Midi-Pyrenees and Latvia. However, comparing garlic subspecies originating from France and Latvia by the content of allyl mercaptan, 1,2-dithiolane and 3-vinyl-1,2-dithiin, a considerable proportional difference of these volatiles was determined. Also, a significant difference was established in the content of DADS between the white garlic variety ＂Blanc de Lomagne＂ （France, region of Midi-Pyrenees） and white garlic grown in other countries. The results of this study suggest the suitability of solid phase microextraction （SPME） and gas chromatography （GC） methods for quality control of garlic originating from France.

Chemical and Biochemical Characterization of Doenjang （Korean Soy Paste） Supplemented with Glasswort （Salicornia herbacea L.） and Rice （Oryza sativa L.）

Four types of Doenjang were prepared from 100% （w/w） defatted soybean （DFS）, a mixture of 80% （w/w） defatted soybean and 20% （w/w） glasswort （DFS-G）, a mixture of 80% （w/w） defatted soybean and 20% （w/w） rice （DFS-R）, or a mixture of 60% （w/w） defatted soybean, 20% （w/w） glasswort and 20% （w/w） rice （DFS-GR）. Maturity of the DFS-G doenjang was the highest, which was proportional to total amino acid content. Antioxidative compounds and total amino acids were relatively higher in the doenjang with glasswort （DFS-G, DFS-GR） than those in the other preparations （DFS, DFS-R）. Succinic and pyroglutamic acid were relatively higher but levulinic acid was relatively lower in the doenjang with glasswort compared to those in the others. Mn, Fe, Zn, and Al were relatively higher in the doenjang with glasswort compared to those in the others. Volatile organic compounds were differently produced depending on doenjang type and influenced definitely by addition of glasswort and rice. Some bacterial communities responsible for meju fermentation were changed during ripening for doenjang whereas others were conserved.