Development and evaluation of terminally epoxidized triglycerides for coatings applications

Epoxidized 10-undecenoic acid triglyceride, an experimental seed oil derivative that has a terminal epoxy group on each of the three acyl glyceride segments, has been found to have good reactivity with amine curatives and allows room temperature cures to be obtained. Coatings based on epoxidized 10-undercenoic acid triglyceride have also shown excellent UV stability. As an example, coatings samples placed in a QUVA chamber exhibit no loss in gloss after 3000 hr of a cycled exposure to high intensity UV lamps and moisture at temperatures of 50–60°C. In comparison, coatings based on standard liquid epoxy resins (LERs) and commercially available hydrogenated LERs lose gloss due to chalking/decomposition within 200–800 hr. Presented at the 81 st Annual Meeting of the Federation of Societies for Coatings Technology, November 12–14, 2003, in Philadelphia, PA.     

Degradation of a textile azo dye by pulsed arc discharge to the surface of wastewater

The pulsed arc discharge to the surface of wastewater was applied to the degradation of a textile azo dye (Acid Red 27). A high-voltage electrode (discharging electrode) was vertically placed above the surface of the wastewater while the wastewater itself was grounded. The pulsed arc discharge occurred between the tip of the discharging electrode and the surface of the wastewater, producing various oxidative species. Oxygen was used as the working gas instead of air to prevent nitrogen oxides from forming. The effect of several parameters on the chromaticity and chemical oxygen demand (COD) removal was examined. The results obtained showed that the chromaticity of the wastewater was completely removed by this process and the COD also decreased significantly. It has been found that ozone formed in the gas phase mainly affects the removal of the dye. The contribution of other effects such as ultraviolet light emission and OH radical formation during the arc discharge to the degradation of the dye was found to be less than 15%. For the present reactor system, the optimum pH, pulse repetition rate and agitation speed were found to be 3.0, 110 Hz and 300 rpm, respectively.     

Crop residue,manure and fertilizer in dryland maize under reduced tillage in northern China: I grain yields and nutrient use efficiencies

The rapidly increasing population and associated quest for food and feed in China has led to increased soil cultivation and nitrogen (N) fertilizer use, and as a consequence to increased wind erosion and unbalanced crop nutrition. In the study presented here, we explored the long-term effects of various combinations of maize stover, cattle manure and nitrogen (N) and phosphorus (P) fertilizer applications on maize (Zea mays L.) yield and nutrient and water use efficiencies under reduced tillage practices. In a companion paper, we present the effects on nutrient balances and soil fertility characteristics. The ongoing factorial field trial was conducted at Shouyang Dryland Farming Experimental Station in northern China from 1993 onwards. The incomplete, determinant-optimal design comprised 12 treatments, including a control treatment, in duplicate. Grain yields and N, P, and potassium (K) uptakes and N, P and K use efficiencies were greatly influenced by the amount of rain during the growing season (GSR), and by soil water at sowing (SWS). There were highly significant interactions between GSR and added stover and manure, expressed in complex annual variations in grain yield and N, P and K use efficiencies. Annual mean grain yields ranged from 3,000 kg ha⁻¹ to 10,000 kg ha⁻¹ and treatment mean yields from 4,500 kg ha⁻¹ to 7,000 kg ha⁻¹. Balanced combination of stover (3,000–6,000 kg), manure (1,500–6,000 kg) and N fertilizer (105 kg) gave the highest yield. Stover and manure were important for supplying K, but the effects differed greatly between years. Overall mean N recovery efficiency (NRE) ranged from 28% to 54%, depending on N source. NRE in wet years ranged from 50% to 90%. In conclusion, balanced combinations of stover, manure and NP fertilizer gave the highest yield and NRE. Reduced tillage with adding stover and manure in autumn prior to ploughing is effective in minimizing labor requirement and wind erosion. The potentials of split applications of N fertilizer, targeted to the need of the growing crop (response farming), should be explored to further increase the N use efficiency.     

Tensile properties,morphology, and thermal behavior of PVC composites containing pine flour and bamboo flour

Composites of unplasticized poly(vinyl chloride) (PVC) blended with bamboo flour and pine flour, respectively, were prepared in a batch mixer followed by compression molding. The effects of wood flour fillers on the morphology, static mechanical properties, and thermal properties of the composites were investigated. Compared with neat PVC resin, the introduction of both bamboo flour and pine flour significantly improved the stiffness of the composites, while decreasing the tensile strength to some extent. Tensile tests showed that pine flour–filled composites exhibited better mechanical properties than those filled with bamboo flour with the same particle size at the same loading level. Scanning electron microscopic examination revealed good dispersion and alignment tendency of short pine fiber within the composites at a lower loading level. Moreover, experimental results indicated that both bamboo flour and pine flour additions showed no obviously adverse effect on the thermal stabilities of these composites. Based on the comprehensive properties, these composites meet the need of woodlike material for use as wood structures. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1804–1811, 2004     

Purification of 2-mercaptobenzothiazole by solvent extraction

−Purification of 2-mercaptobenzothiazole (91.9% purity) by solvent extraction was studied. The extraction of impurities present in crude 2-MBT (e.g. benzothiazole, sulfides and sulfur containing compounds) was carried out at temperatures between 70-180°C using various solvents and their mixtures of different polarity. The highest purity of 2-MBT, above 99% was obtained using nitrobenzene, toluene and ethanol, even at a concentration of 2-MBT above 50 wt%. Increasing temperature and decreasing concentration of the raw material have a positive influence on the purification process. A comparable efficiency of purification was observed also with mixed solvents, (toluene with ethanol, acetone and aniline) possessing the same polarities. A correlation between the polarity indexes (PI) of mixed solvents and experimentally obtained purity of 2-MBT was found. The highest purity of 2-MBT provides extraction of the raw material with mixed solvents having PI 3.8-4.4.     

Synthesis and properties of chitosan-modified poly(vinyl butyrate)

Modification of chitosan by grafting of vinyl butyrate was carried out in homogeneous phase using potassium persulfate as redox initator and 1.5% acetic acid as solvent. The percent grafting and grafting efficiency were analysed and the high grafting efficiency up to 94% was observed. The effects of reaction variables such as monomer concentration, initiator concentration, temperature and reaction time were investigated. It was observed that the solubility of chitosan was markedly reduced after grafting with vinyl butyrate. The grafted product is insoluble in common organic solvents as well in dilute organic and inorganic acids. Characterization of the graft copolymers were carried out by using Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM) technics. Characteristic signal of carbonyl group was observed at 1,731 cm⁻¹ which belongs to the poly vinyl butyrate segments in the graft copolymer. The melting transition of the chitosan main chain in the copolymer shifted to 124°C from its original value 101°C. In addition to these, we have also studied topology of the graft copolymer and the SEM micrograph showed continuous homogenous matrix which means there is no phase separation.     

融合多头自注意力的问答社区专家推荐算法

专家推荐是在线问答社区的研究热点之一,但现有的算法大多关注用户的静态兴趣和问题信息的匹配,忽视了对用户的动态兴趣表征信息的有效捕捉,从而导致推荐的准确度不足。针对上述问题,提出了融合多头自注意力的问答社区专家推荐算法。首先,构造由卷积神经网络和注意力机制组成的问题编码器,来处理目标问题和用户历史回答问题,提取对应的问题表征;其次,将用户历史回答问题序列当作时间序列,利用多头自注意力机制学习序列中所蕴涵的动态兴趣表征,结合用户的静态兴趣表征,获取用户的综合兴趣表征;最后,将目标问题表征和用户综合表征进行相似性计算产生推荐结果。利用来自知乎问答社区的真实数据进行了不同参数配置及不同算法的对比实验,实验结果表明该算法性能要明显优于目前较流行的深度学习专家推荐算法。     

支持O2O的时空众包激励技术研究

在这个流行元素日新月异的时代,消费者的口味越来越难以把控,商家的判别标准将极大决定店铺的业绩水平.文章介绍了时空众包的概念,研究在商城背景下,利用时空众包思想设计一种能持续有效执行的机制来提高O2O模式的资源利用率问题.     

新工科背景下信息安全专业建设和人才培养模式探索

针对新工科背景下信息安全专业创新型人才需求,对本校网络与信息安全专业建设和人才培养模式进行探索,从能力培养体系、课程体系、实践教学体系、教学模式、考核体系等方面进行改革,制定符合本校特色的专业培养方案,并阐述人才培养模式实践过程中教学、实践、科研方面取得的初步成效.     

智慧农业综合信息服务系统的设计与开发

针对目前市场上大多数农业信息服务平台功能单一的缺点,设计了一款集专家在线答疑、智能识别病虫害、农业知识学习、农友社交服务于一体的系统,旨在帮助农户解决生产过程中的难题,推动农业生产发展.该系统采用前后端分离开发技术,后端使用Spring、SpringMVC、MyBatis框架搭建,前端使用Vue、Ajax技术开发,并采取SIFT算法实现图像匹配.使用结果表明,该软件功能全面,操作简便,能够满足农户基本需求.