Selective elution of tea catechins and caffeine from polyvinylpolypyrrolidone

Desorption of catechins and caffeine from polyvinylpolypyrrolidone (PVPP) was comprehensively investigated. The result showed that caffeine could easily be desorbed from PVPP by the tested solvents except n‐hexane, while catechins could only be thoroughly done by dimethyl sulphoxide (DMSO) and N, N‐dimethylformamide (DMF). Excellent desorption efficiency of DMSO and DMF might be attributed to their high dipole moments and H‐bond potentials. Addition of ethanol was recommended considering the elution efficiency and fluidity, but ethanol volume should be <40% (v/v) for DMSO or 20% (v/v) for DMF. Desorption would get to equilibrium within 1 h and followed the pseudo‐second‐order model. Caffeine and catechins could be separately desorbed through two‐stage elution procedure, that is, water or 20% aqueous ethanol for desorbing caffeine and part of nongalloylated catechins and DMSO/ethanol (8/2, v/v) for eluting the remaining catechins. Highly purified catechins (~95%) with high level (~70%) galloylated catechins would be achieved when the desorption procedure was applied in column chromatograph.     

An improved initialization method of D-KSVD algorithm for bearing fault diagnosis

A novel bearing fault diagnosis method combining feature extraction based on wavelet packets quantifiers and pattern recognition method based on improved initialization method of Discriminative K-SVD (D-KSVD) algorithm is proposed. In D-KSVD algorithm, the representational power of dictionary and discriminative ability of classifier are seriously affected by their initialization values. Therefore, the improved initialization method of D-KSVD is presented and employed for bearing fault diagnosis. The improvement is that during the initialization of training stage, subdictionaries corresponding to each category are trained by K-SVD separately and then the initial dictionary is constructed by cascading the subdictionaries, which can completely represent the characteristics of all categories, and as for the initialization of linear classifier, naive Bayesian classifier is utilized. The experimental results show that under the same parameters the improved D-KSVD has better classification ability compared with traditional D-KSVD and some other classification methods.     

Distributed User Association with Resource Partitioning in Heterogeneous Cellular Networks

To fully utilize the resources of heterogeneous cellular networks (HCNs), an effective approach that offloads users to the underloaded small cells from overloaded macrocells is widely advocated. However, this operation often leads to a bad result that the offloaded users achieve lower signal-to-interference-plus-noise-ratio (SINR) than these users in macrocells. Thus, some appropriate interference avoidance techniques should be adopted to partially alleviate the SINR degradation. For this, we consider the resource (frequency) partitioning that turns off some fraction of such resources in a macrocell. Naturally, an optimal offloading strategy should be closely coupled with resource partitioning, and in turn the optimal partition decides the offloading performance. In this paper, we propose a distributed association strategy with joint offloading and resource partitioning for HCNs. We reveal that load balancing, by itself, is insufficient, and additional resource partitioning is required to improve system performance. Meanwhile, we also show that, compared with the best power association and range extension association, the proposed scheme provides better association performance.

     

Effect of contact angle on bubble formation at submerged orifices

This paper presents a theoretical model and experimental results of the generation of bubbles due to the injection of a constant flow rate of gas through an orifice submerged in liquid. The bubble formation process can be identified into three distinct stages termed (1) nucleation stage, (2) growth stage, and (3) detachment stage by analyzing the evolution of interface equilibrium and force balance conditions. Influence of contact angle on bubble formation at each stage is quantitatively elucidated. Experimental investigations in the preparation process of aluminum foams by gas injection method were conducted, and the generated bubble size was measured. The theoretical prediction of the present model suits well with the experimental results when a contact angle of 30° is introduced. The present model covers a wide range of contact angle (θ < 90°) at different gas flow rates and orifice radii in both aqueous and metallic systems.     

An improved saliency detection method based on non-uniform quantification and channel-weighted color distance

Multimedia Tools and Applications - We propose a non-uniform quantification method for RGB channels based on the visual sensitivities of human eyes to the red, green and blue colors, and give...     

Cyclic error correction based Q-learning for mobile robots navigation

International Journal of Control, Automation and Systems - Similar to control systems, reinforcement learning can capture notions of optimal behavior using natural interaction experience. In the...     

基于多克隆抗体包被磁性纳米粒子的ELISA法检测西维因

建立一种基于抗体包被氨基化Fe3O4磁性纳米粒子,建立免疫磁珠酶联免疫吸附测定(enzyme-linked immunosorbent assay,ELISA)法用于检测氨基甲酸酯农药西维因。结果表明:在最佳条件下,西维因质量浓度在1×10-3~10 mg/L范围内,建立的免疫磁珠ELISA法具有较好的线性关系(y=8.87lnx+72.77,R2=0.994),抑制率最高可达90.6%;测得的半抑制浓度(half maximal inhibitory concentration,IC50)为0.077 mg/L,检出限(IC15)为1.48×10-3 mg/L。以质量浓度1 mg/L的西维因在相同条件下重复检测3次,相对标准偏差为1.67%。以大米和卷心菜为实际样品进行西维因加标回收率实验,通过免疫磁珠ELISA法测得的回收率为70.5%~123.1%,同时采用高效液相色谱法进行相关性验证,结果表明,2种方法检测结果的相关性较好(R2=0.91)。通过一系列分析表明,所建立的抗体包被磁性纳米粒子ELISA法可用于快速检测西维因。     

Sources of Variability and Lower Values in Toughness Measurements of Weld Metals

In this paper, the sources of variability and lower values in toughness measurements of a high-strength low alloy weld metal are investigated by detailed observations of fracture surfaces and the microstructures at crack initiation. The results reveal that the variability of the notch Charpy toughness is related to the location of the cleavage initiation origins. The three factors jointly contribute to give rise to variability and lower value of toughness. That is, (1) the location that the notch is sampled at deposited weld metal or reheated weld metal, (2) the location that a large grain region is appeared on the path ahead of the notch root, (3) the distributed location of the defect or the brittle second-phase particle. When three factors were simultaneously satisfied, the lower value of the Charpy toughness is appeared. The notch is sampled at the largest grain region at deposited weld metal, and the defect or the brittle second-phase particle is close to the notch root and sampled by its high stress field, the lowest Charpy toughness is obtained.     

曝气生物滤池处理沥青烟气的研究探讨

沥青工业产生的有机污染物已经成为影响我国环境问题的重要因素。当前沥青烟气处理的主要方法存在除尘效率不高,容易产生二次污染,投资成本大等缺点。在这个背景下,广东省公路管理局开展了沥青热发臭气治理技术开发及应用课题,课题采用曝气生物滤池进行沥青热发臭气治理,大胆借鉴了接触氧化法以及生物滤池的解决方案,把生物降解和吸附过滤两种治理方法有机结合起来,对沥青烟气进行有效控制和处理,有效地实现可持续发展生产和优化生产环境。     

Investigation of immiscible Sn–Zn coatings with two-layer microstructure as anode material for Li-ion battery

The exfoliation of Sn as a result of volume expansion led to the drastic capacity decay in lithium-ion batteries. In this article, the immiscible Sn–Zn coating was successfully prepared by electrodeposition and applied as the anode material in Li-ion batteries. The physical structure and electrochemical properties were characterized by X-ray diffraction, scanning electron microscope, electron probe microanalysis and charge–discharge test, respectively. The Sn–Zn deposit displayed unique two-layer morphology composed of a Zn flat bottom layer and a Sn dendritic upper layer. The novel Sn–Zn electrodes showed noticeable improvement in cyclability compared to pure Sn film. This improvement was assigned to the characteristic of the two-layer microstructure: the Zn interlayer enhanced the binding strength between Sn dendrites and copper foil; the abundant space among these individual Sn dendrites accommodated the volume expansion during lithiation process. The two-layer Sn–Zn coatings were anticipated as potential anode materials for Li-ion batteries.