Experimental study on drying characteristics of wheat by low-field nuclear magnetic resonance

The characteristics of transverse relaxation time (T₂) of water in wheat were studied by measuring the relaxation time of low-field nuclear magnetic resonance. Analysis of the exponential distribution of T₂ revealed that wheat contains five water components. The T₂ relaxation time and distribution significantly changed during drying. The dynamic characteristics of five water components during wheat drying were determined using the signal quantity of their characteristic peaks, which showed different features. Weakly chemically bound water (T₂₂) and water ascribed to cell wall (T₂₃) were the main source of water loss. Moreover, most T₂₃ and extracellular water (T₂₄) were removed during drying. Water migration between strongly chemically bound water (T₂₁) and the other water components was bidirectional. This process was not only affected by temperature but also by wheat moisture content and proportion of the five water components. The start time of water migration advanced and growth rate of T₂₁ at the end of drying to that before drying increased at 60, 70, and 80°C. Drying at varied temperatures should be applied according to the characteristics of five water components during the drying process. In addition, high initial temperature was found to be necessary to achieve high drying rate of T₂₃, T₂₄, and free water (T₂₅). The use of drying temperature of 80°C at the early stage and then changing to 70°C reduced the heat consumption by 4.81% and increased the drying time by 9.61%.     

25 g/L灭菌唑悬浮种衣剂在小麦及其土壤中的消解动态与残留

为评价灭菌唑在小麦上使用的安全性,建立其使用规范,于2015年开展了25 g/L灭菌唑悬浮种衣剂消解动态研究及最终残留试验。样品采用乙腈提取,固相萃取柱净化,LC/MS/MS进行检测。结果表明:灭菌唑在小麦植株和土壤中的半衰期分别为1.8~11.7 d、12.5~17.5 d。灭菌唑在小麦、植株及土壤中的最终残留量均低于0.05 mg/kg。结合日本小麦上灭菌唑最大残留限量值,拟推荐灭菌唑在我国小麦上的最大残留限量为0.05 mg/kg。     

MATHEMATICAL SIMULATION OF TEMPERATURE AND MOISTURE FIELDS WITHIN A GRAIN KERNEL DURING DRYING

ABSTRACT

Non-linear partial differential equations are presented for two dimensional heat and mass transfer within a single grain kernel during drying. In this model, the moisture evaporation inside the kernel is considered. The moisture is assumed to diffuse to the outer boundary of the kernel in liquid form and evaporate on the surface of the kernel. The influence of temperature and moisture content on grain properties is also considered in the simulation. The Non-linear partial differential equations are solved using the finite element method and simulation data is verified on a thin layer dryer for wheat kernels. The comparison shows that the simulated results have a high accuracy with average relative error of about 5%. The results of the finite element analysis can be used for grain quality evaluation, drying simulation studies and stress analysis of grain kernel.     

Adaptive Finite Element Analysis of Air Flow Inside Grain Dryers

ABSTRACT

This paper presents a simulation study of air flow inside dryers. An adaptive finite element methodology for two-dimensional problems was developed. This study is the first application of nadaptive techniques to such tupe of problems. The formultion is generic and can be easily extended to three-dimensional analysis. Several dryer configurations were studied in order to verify the efficiency and accuracy of the proposed methodology. Results agreed well with experimental data and show significant imporvements when compared to the conventional finite elements analysis.     

A STOCHASTIC APPROACH TO THE DRYING OF SOLIDS IN A MULTI-STAGE FLUIDIZED BED

The residence times of solids flowing through a fluidized bed dryer exhibit dispersion about the mean. In this paper, expressions for the probability density functions of solids moisture content in the various stages of a multi-stage dryer are derived. A simple recurrence relationship for the moments of the distribution is also presented. The analysis is applied to the drying of cereal grains, and it is shown that the degree of drying increases with the number of stages in the dryer. Probability density functions of the moisture content are presented.     

黑龙江省哈尔滨地区传统面制食品中铝含量调查分析

对2012年哈尔滨市城区各露天摊点和快餐店的面制食品进行随机采样,并采用微波消解技术-电感耦合等离子体质谱(ICP-MS)方法检测城区早餐面制食品(馒头、花卷、蒸包、油条、油饼、油炸麻团)中的铝含量。检测样品194份,合格147份,合格率为75.8%;其中油条的合格率最低为35%。哈尔滨市城区早餐市场上铝污染问题突出,望尽早推广膨松剂无铝配方的新技术。     

麦秆液化物环氧树脂的制备与表征

以苯酚为溶剂,浓硫酸为催化剂液化麦秆得到麦秆液化产物,并以其为原料与环氧氯丙烷反应制备出以麦秆液化物为基材的环氧树脂。考察了液比(苯酚与麦秆质量比)、反应温度和反应时间对液化反应的影响。采用凝胶渗透色谱(GPC)对比分析了麦秆液化物及其环氧树脂的相对分子量分布。以聚酰胺为固化剂进行固化并进行力学测试。结果表明:在液比为4∶1,反应温度为150℃,反应那个时间为60min时,麦秆液化效果最佳,此时,麦秆液化物环氧树脂固化物的剪切强度可达4.1MPa。     

防治小麦赤霉病的药剂筛选研究

为了筛选防治小麦赤霉病的高效、经济、安全的药剂,进行不同药剂防治小麦赤霉病试验。结果表明:在小麦扬花期施药,25%氰烯菌酯悬浮剂1500 g/hm2对小麦赤霉病的防治效果最佳,发病率为23.13%,病指防效达78.01%;59.7%咪锰.多菌灵可湿性粉剂450 g/hm2的防效次之,发病率为29.93%,病指防效为70.18%;而对照药剂40%多.酮可湿性粉剂1500 g/hm2的发病率高达46.71%,病指防效仅为54.27%。     

改性小麦面筋蛋白作为木材胶粘剂的粘接强度和抗水性研究

通过十二烷基硫酸钠(SDS)对小麦面筋蛋白进行化学改性,提高小麦面筋蛋白的粘接强度和抗水 性,从而达到作为木材胶粘剂的要求。