月表尘埃颗粒带电的机理及应用研究

研究月尘颗粒在电子束环境下以及紫外源辐照下的带电机理,利用数值方法模拟月尘颗粒在不同背景环境下的充电过程,以探索月表尘埃颗粒的带电机理,进而便于地面月尘环境模拟装置选择合适的月尘带电方式进行空间模拟实验.给出了尘埃在电子束环境下的充电方程,并将紫外辐射带电与具体应用相结合.通过模拟结果可知,在电子束环境下,月尘表面的电荷数随粒径尺寸增大,随电子枪辐照束斑半径减少,随电子枪流强的增加而增多;在紫外源的辐照下,月尘表面电荷数随颗粒尺寸的增大以及紫外线辐照度的增加而增多.由月尘颗粒受太阳紫外辐照带电的数值模拟结果可知,月尘需要在太阳长时间的辐照下才可以带上可观的电荷数,地面模拟该过程需增加辐照源来加速实验.通过模拟结果的分析比较并结合"空间环境模拟装置"中对月尘舱的设计要求,最终优选紫外源辐照带电方式作为月尘颗粒的带电方案.     

Resonant decay of a Langmuir wave in the presence of dust grains in a cylindrical plasma

The resonant parametric decay of a Langmuir wave into a backward propagating Langmuir wave and an ion acoustic (IA) wave is studied in a cylindrical dusty plasma. The analysis shows that the frequency of the IA mode decreases with the parameter δ_c (where δ_c is the ratio of the ion density to the electron density) for negatively charged dust grains. The growth rate of the resonance decay instability (RDI) and the threshold required for its onset also decrease with δ_c and are strongly dependent on the electron to ion temperature ratio for both positively and negatively charged dust grains. The results obtained also illustrate the dependence of the threshold of the resonance decay instability (μ_th) on the plasma cylinder radius.     

Ultrasonic scattering in polycrystals with orientation clusters of orthorhombic crystallites

Scattering-induced ultrasonic attenuation and backscattering in a polycrystalline medium with orientation clusters composed of orthotropic crystallites are studied theoretically, aiming to improve understanding of ultrasonic wave interaction with such clustered microstructures for application to the modeling of titanium alloys. Both orthorhombic crystallites and their arrangements in orientation clusters (also termed microtexture regions, MTRs) are of general ellipsoidal shape. The preferred orientation of orthotropic crystallites in the clusters is represented by a generalized Gaussian orientation distribution function with three independent texture parameters. The effective elastic properties of the clusters, which have in general orthorhombic symmetry, are determined by a volume average of elastic constants weighted by orientation distribution functions and then used to obtain the cluster-scattering-induced attenuation and backscattering in the polycrystalline medium. In the model the wave propagation direction is arbitrary relative to the ellipsoidal axes of the clusters. The contribution of crystallite-scattering-induced attenuation is estimated by the untextured attenuation coefficient factored by a texture transition function. The total attenuation and backscattering are determined by combining scattering by the clusters and crystallites. Drastic effects of clustering and the transition to unclustered polycrystals are demonstrated. Reasonable agreement is observed between the model’s prediction and measurements on two Ti-alloy samples with different crystallite clustering.     

胶束电动毛细管色谱法检测红曲米中的莫纳可林K

建立了测定红曲米中莫纳可林K含量的胶束电动毛细管色谱(MEKC)方法。考察了运行缓冲液的种类、pH及其浓度、有机添加剂、十二烷基硫酸钠(SDS)的浓度和分离电压等实验条件对电泳分离效果及检测灵敏度的影响。在优化的实验条件下,以20 mmol/L硼砂(pH 10.6,含10%(体积分数)乙醇和40 mmol/L SDS)作为缓冲溶液,莫纳可林K能在23 min内实现很好的基线分离,线性范围为5.00～100.00 mg/L,线性相关系数为0.9976,检出限(以信噪比(S/N)为3计)为0.13 mg/L,加标回收率为98.5%～99.5%。精密度和稳定性试验中,峰面积和迁移时间的相对标准偏差均小于3%,表明重复性良好。该方法简便、快速、灵敏,可用于红曲米中莫纳可林K含量的测定。     

Near-Infrared spectroscopy and hyperspectral imaging for non-destructive quality assessment of cereal grains

Hyperspectral imaging (HSI) combines spectroscopy and imaging, providing information about the chemical properties of a material and their spatial distribution. It represents an advance of traditional Near-Infrared (NIR) spectroscopy. The present work reviews the most recent applications of NIR spectroscopy for cereal grain evaluation, then focuses on the use of HSI in this field. The progress of research from ground material to whole grains and single kernels is detailed. The potential of NIR-based methods to predict protein content, sprout damage and α-amylase activity in wheat and barley is shown, in addition to assessment of quality parameters in other cereals such as rice, maize and oats, and the estimation of fungal infection. This analytical technique also offers the possibility to rapidly classify grains based on properties such as variety, geographical origin, kernel hardness, etc. Further applications of HSI are expected in the near future, for its potential for rapid single-kernel analysis.     

Generalized balanced power diagrams for 3D representations of polycrystals

Characterizing the grain structure of polycrystalline material is an important task in material science. The present paper introduces the concept of generalized balanced power diagrams as a concise alternative to voxelated mappings. Here, each grain is represented by (measured approximations of) its centre of mass position, its volume and, if available, and by its second-order moments (in the non-equiaxed case). Such parameters may be obtained from 3D X-ray diffraction. As the exact global optimum of our model results from the solution of a suitable linear programme it can be computed quite efficiently. Based on verified real-world measurements, we show that from the few parameters per grain (3, respectively, 6 in 2D and 4, respectively, 10 in 3D) we obtain excellent representations of both equiaxed and non-equiaxed structures. Hence our approach seems to capture the physical principles governing the forming of such polycrystals in the underlying process quite well.     

气相色谱-三重四极杆串联质谱法测定发酵乳中4种糠醛类物质

建立了气相色谱-三重四极杆串联质谱(GC-MS/MS)快速检测发酵乳中因热加工处理产生的羟甲基糠醛(5-HMF)、糠醛(F)、甲基糠醛(MF)、2-乙酰基呋喃(FMC)4种糠醛类物质。采用QuEChERS进行样品前处理,选择RTX-WAX色谱柱,在多反应监测模式(MRM)下对发酵乳中4种糠醛类物质进行测定,并优化了萃取试剂、盐析剂用量、净化剂用量。结果显示,在最佳条件下,4种糠醛类化合物的加标回收率为82.2%～118%,相对标准偏差(RSD)不大于10%。F、FMC、MF的线性范围为0.002～2 mg/L,5-HMF线性范围为0.02～2 mg/L,相关系数均不小于0.998,方法的定量下限(LOQs)和检出限(LODs)分别为3.0～45μg/kg和1.0～15μg/kg。该方法简便快速,灵敏度高,重现性好,满足定性定量要求。该方法对5种原味发酵乳和6种炭烧风味发酵乳的测定结果显示,炭烧风味发酵乳中4种糠醛类物质含量远高于原味发酵乳,表明炭烧工艺导致美拉德反应更加充分,间接说明过热处理会导致发酵乳中危害物增多,影响其营养价值和品质,该文为消费者提供了合理的选购建议与指导。     

Thermal self-sustainability of biochar production by pyrolysis

The pyrolysis of several agricultural and biofuel production residues (grape residues, sugarcane residues, dried distiller's grain, palm oil residues, apple pomace and forestry residue) has been carried out in a pilot bubbling fluidized bed pyrolyzer operating under a range of temperature from 300 to 600 °C and two vapor residence times (2 and 5 s), with the aim of determining their pyrolysis behavior including products yields and heat balance. The composition of the product gases was determined, from which their heating value was calculated. The liquid bio-oil was recovered with cyclonic condensers. The thermal sustainability of the pyrolysis process was estimated by considering the energy contribution of the product gases and of the liquid bio-oil in relation to the pyrolysis heat requirements. The most promising biomass feedstocks for the sustainable production of biochar were indentified. Furthermore, this study presented the char yield in relation to the excess heat that could be obtained by combusting the gas and bio-oil coproducts of biochar production, as functions of pyrolysis temperature and vapor residence time.     

Amino-Acid Composition of Protein Fractions from Fermented Feed

The possibility of preparing feed from wheat straw via fermentation by cellulolytic enzymes from the fungusTrichoderma harzianumis demonstrated. The water- and salt-soluble fractions of the fermented feed contain the largest quantity of essential amino acids (22.93%). The predominant essential amino acids are lysine, leucine, methionine, and threonine. The total essential amino acids in the water- and salt-soluble fractions represent 31.44% of the total amount of protein in the fermented feed     

高粱籽粒中多酚类物质的傅立叶变换近红外光谱分析

利用高效液相色谱(HPLC)法测定高粱籽粒中阿魏酸、原儿茶醛和花青素的含量,比色法测定总酚、总黄酮、缩合单宁的含量;运用偏最小二乘法建立NIR光谱与HPLC法和比色法分析值之间的多元校正模型,预测高粱籽粒中主要酚类物质的含量.结果表明,各成分近红外预测值与实测值之间的校正模型相关系数(R)、内部交叉验证均方差(RMSECV)、最佳主因子数分别为:总酚0.9737, 0.288, 4;总黄酮0.9660, 0.00671, 8;缩合单宁0.9558, 0.0289, 6;阿魏酸0.9818, 0.0391, 6;原儿茶醛0.9979, 0.0118, 5;花青素0.9977, 0.0523, 4;预测相对偏差(RSEP)分别为:总酚6.99%、总黄酮4.54%、 缩合单宁7.13%、阿魏酸2.68%、原儿茶醛5.46%、 花青素5.81%.结果表明,模型对样品NIR的预测值与其相应的化学值有较好的相关性,此模型可用来预测高粱籽粒中的各酚类物质的含量,在高粱优质育种和品质分析中具有广泛的应用价值.