Synthesis of ZnS nanoparticles of required size by precipitation in aerosol microdroplets

Zinc sulphide (ZnS) nanoparticles were prepared by an aerosol method from zinc acetate and sodium sulphide (Na₂S) aqueous solutions. Aqueous solution of zinc acetate was dispersed into the form of microdroplets, which were introduced by airflow to vigorously stirred aqueous solution of Na₂S, which was in excess. Microdroplets served as microreactors, so the reaction took place only in limited volume. Particle size distribution was studied by transmission electron microscopy and by dynamic light scattering measurements. In this work, the equation that allows us to predict the final size distribution of ZnS nanoparticles using exact concentration of zinc acetate was derived and ZnS nanoparticles with predicted mean particle diameter around 50 and 70?nm were successfully synthetised.     

Feasibility study to control fiber distribution for enhancement of composite properties via three-dimensional printing

The distribution of fibers in the composite (which takes into account both their locations and orientations) is one of the important factors that affect the mechanical properties of FRCs. However, this parameter depends on various factors during composite fabrication, and controlling the distribution of fibers in the produced material represents a significant challenge. In this study, the applicability of three-dimensional (3D) printing technique for controlling fiber distributions was evaluated. The fibers fabricated using a 3D printer were placed inside a mold to produce cementitious composites. Three-point bending tests were conducted and the results of the experiment were discussed.     

Comprehensive Analysis of Secure Data Aggregation Scheme for Industrial Wireless Sensor Network

As an Industrial Wireless Sensor Network (IWSN) is usually deployed in a harsh or unattended environment, the privacy security of data aggregation is facing more and more challenges. Currently, the data aggregation protocols mainly focus on improving the efficiency of data transmitting and aggregating, alternately, the aim at enhancing the security of data. The performances of the secure data aggregation protocols are the trade-off of several metrics, which involves the transmission/fusion, the energy efficiency and the security in Wireless Sensor Network (WSN). Unfortunately, there is no paper in systematic analysis about the performance of the secure data aggregation protocols whether in IWSN or in WSN. In consideration of IWSN, we firstly review the security requirements and techniques in WSN data aggregation in this paper. Then, we give a holistic overview of the classical secure data aggregation protocols, which are divided into three categories: hop-by-hop encrypted data aggregation, end-to-end encrypted data aggregation and unencrypted secure data aggregation. Along this way, combining with the characteristics of industrial applications, we analyze the pros and cons of the existing security schemes in each category qualitatively, and realize that the security and the energy efficiency are suitable for IWSN. Finally, we make the conclusion about the techniques and approach in these categories, and highlight the future research directions of privacy preserving data aggregation in IWSN.     

Tibetan Multi-Dialect Speech and Dialect Identity Recognition

Tibetan language has very limited resource for conventional automatic speech recognition so far. It lacks of enough data, sub-word unit, lexicons and word inventories for some dialects. And speech content recognition and dialect classification have been treated as two independent tasks and modeled respectively in most prior works. But the two tasks are highly correlated. In this paper, we present a multi-task WaveNet model to perform simultaneous Tibetan multi-dialect speech recognition and dialect identification. It avoids processing the pronunciation dictionary and word segmentation for new dialects, while, in the meantime, allows training speech recognition and dialect identification in a single model. The experimental results show our method can simultaneously recognize speech content for different Tibetan dialects and identify the dialect with high accuracy using a unified model. The dialect information used in output for training can improve multi-dialect speech recognition accuracy, and the low-resource dialects got higher speech content recognition rate and dialect classification accuracy by multi-dialect and multi-task recognition model than task-specific models.     

Engineering the Structure of Mesoporous Bioactive Glass Microspheres by the Surface Effect of Inverse Opal Templates and Temperature

The interactions of ions and molecules with material surface are highly dependent on the surface properties of the material. Therefore, the distribution of ions or molecules near the material surface may be affected by the surface properties. This phenomenon can be significant enough for controlling the structure of a material synthesized in the sub‐micrometer scale confinement space of a template. This work confirms that inverse opals are perfect templates for offering confinement space, while their different surface properties can strongly affect ion and block copolymer distribution in the confinement space. This surface effect principle can be used for the controlled synthesis of colloids with complex composition. As an example, four kinds of mesoporous magnetic bioactive glass colloids with ordered mesopores, core–shell structure, open surface pores, or disordered mesopores are prepared by using polystyrene and carbon inverse opal templates. This work reveals that inverse opal templates possess great advantage in controlled synthesizing colloidal structures due to their surface effect on ions and molecules and confinement space.     

高压液相色谱法检测酸性乳饮料及酸奶中对羟基苯甲酸酯类

目的 建立酸性乳饮料及酸奶中对羟基苯甲酸甲、乙、丙、丁酯含量的高压液相色谱分析方法。方法 样品去蛋白后, 用甲醇提取, 提取液用高压液相色谱仪进行检测。结果 对羟基苯甲酸甲酯、对羟基苯甲酸乙酯、对羟基苯甲酸丙酯、对羟基苯甲酸丁酯在 0～10 μg/kg 范围内, 相关系数大于 0.999, 检出限分别为 0.48、0.45、0.47、0.49 mg/kg; 在 1、2、5 mg/kg 3 个加标水平下,样品中对羟基苯甲酸甲酯、对羟基苯甲 酸乙酯、对羟基苯甲酸丙酯、对羟基苯甲酸丁酯的加标平均回收率分别为 95.59%~104.52%、93.21%~108.05%、 97.75%~107.98%、97.48%~103.67%, 相对标准偏差均小于 10%。结论 本方法适用于乳与乳制品中对羟基苯 甲酸(尼泊金)甲、乙、丙、丁酯含量的测定需要。     

超高效液相色谱-串联质谱法快速测定云南野生致命鹅膏菌中的毒伞肽和毒肽毒素

目的建立超高效液相色谱-串联质谱法(ultra performance liquid chromatography-tandem mass spectrometry,UPLC-MS/MS)快速测定野生毒菌中的5种毒伞肽和毒肽毒素的分析方法。方法将采集的云南野生致命鹅膏菌子实体低温干燥,用甲醇提取,SPE-C_(18)固相萃取小柱净化,Waters T3色谱柱(2.1 mm×100 mm,1.8μm)分离,串联质谱ESI正离子模式下进行定性定量分析。结果 5种毒肽和毒伞肽在20～1000μg/kg范围内具有良好的线性关系,相关系数均大于0.99,方法检出限均为20μg/kg。α-毒伞肽、β-毒伞肽、γ-毒伞肽、二羟基毒肽、羟基毒肽在高低2个浓度的平均回收率范围分别为89.2%～110.6%、88.5%～109.3%、90.1%～112.3%、92.6%～107.8%、91.6%～105.2%,变异系数(coefficient of variation,CV)在3.2%～5.6%之间。在云南野生致命鹅膏菌中检测出α-毒伞肽(α-amanitin)、β-毒伞肽(β-amanitin)、羟基毒肽(phallacidin),含量分别为794.84、501.23、230.96 mg/kg。结论该方法使用固相萃取小柱净化样品,减少了试剂的用量,串联质谱可同时对毒肽和毒伞肽毒素进行定性定量检测,提高了定性检测的准确性和定量检测的灵敏度。     

气体二氧化氯对樱桃番茄贮藏品质的影响

以樱桃番茄为试材,研究10、20、40 g/m~3 ClO_2处理30 min后,10℃贮藏期间的品质变化。结果表明:20 g/m~3 ClO_2处理组综合评价好,贮藏15 d,腐烂率、失重率、可溶性固形物(TSS)、可滴定酸(TA)、V_C分别为27%、5.8%、13.9%、13.3%、29 mg/g FW,呼吸强度波动小,明显优于其他处理组。说明气体Cl O_2对樱桃番茄有一定保鲜效果,且20 g/m~3 Cl O_2处理效果最好。     

Determination of strongly reducing substances in sediment

Reducing substances in sediments play an important role in regulating the chemical and biological status of the sediment. Strongly reducing substances are the most active part of them, and are difficult to measure directly. In this work, we have developed a method for their determination based on the oxidation by Fe(III). Then, the produced Fe(II) was determined by colorimetry, using 2,2'-bipyridine as the chelating agent. Prior to determination, these substances were extracted from the sediment by M acetic acid. The whole process was carried out in a closed system, so that oxidation of Fe(II) and reducing substances by atmospheric oxygen could be avoided. The calibration curve between absorbance and Fe(II)-chelate concentration in extract was linear. When ascorbic acid was added to the extract, the recovery was larger than 94.0%. The effect of surplus Fe(III) on the result was discussed. With the proposed method, the concentration of strongly reducing substances in sediment samples from Dianchi Lake of China was measured with good reproducibility.