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排序方式: 共有429条查询结果,搜索用时 15 毫秒
1.
《Materials Letters》2007,61(8-9):1881-1884
Organic ultraviolet (UV) ray absorbents, cinnamic acid (CA) and p-methoxycinnamic acid (PMOCA) were intercalated into Zn2Al layered double hydroxides (Zn2Al-LDHs) by co-precipitation reaction. The organic–inorganic nanocomposites, Zn2Al-LDH/CA and Zn2Al-LDH/PMOCA were obtained. The samples showed excellent UV ray absorption ability and their catalytic activity for the air oxidation of castor oil greatly decreased when the organic UV ray absorbents were intercalated in the layers of the Zn2Al-LDHs. The studies suggested that Zn2Al-LDH/organic UV absorbent nanocomposites might be used as safe sunscreen materials. 相似文献
2.
《Applied catalysis. B, Environmental》2006,62(1-2):21-27
The effect of hexadecyltrimethylammonium bromide (HTAB) on the photocatalytic degradation of phenol (Phe), 2,5-dichlorophenol (2,5-DCP) and 2,4,5-trichlorophenol (2,4,5-TCP) in the presence of aqueous TiO2 suspensions at pH ca. 5 was investigated using a laboratory photoreactor equipped with a medium-pressure mercury lamp. Inhibition of substrate decomposition was observed for phenol, both below and above the surfactant critical micellar concentration, whereas a more complex behaviour was exhibited by chlorophenols. It was found that adsorption of these compounds onto the surfactant-modified semiconductor particles facilitates their faster decomposition, but the competitive partition of substrates between adsorbed surfactant structures and micellar aggregates tends to limit the beneficial kinetic effects at higher amphiphile concentrations. The crucial influence of surfactant adsorption was clearly evidenced in some runs performed at pH 3. Relevant inhibition of chloride release from chlorophenols, observed in the presence of HTAB, indicates a higher persistence of reaction intermediates in the reaction media, suggesting the need for a careful investigation of surfactant effects on all the degradation steps of the process. 相似文献
3.
介绍手机常用的传感器类型。讲解列举手机中传感器安装的方法,阐述手机传感器的参数及使用方法。以加速度传感器为例,讨论了手机传感器在游戏开发中的应用,详细分析了代码。对初学者有很大帮助。 相似文献
4.
5.
杨元挺 《桂林电子工业学院学报》2009,(5):393-397
网格和移动代理技术的结合,在支持任务调度、作业管理、资源管理以及智能决策等网格关键技术的问题领域有着独到的优点。通过对移动代理在网格环境下的规划问题进行研究,网格所具有的动态性、地域分布性、不确定性使得移动代理原有的静态迁移策略无法适应网格环境。结合基于D—S理论的资源信任度函数提出动态规划方案.即在移动代理进行迁移时.由移动代理与其所在的网格虚拟组织中的信任调度模块协同工作,完成移动代理的迁移任务,保护了移动代理不遭到恶意平台的攻击。 相似文献
6.
针对暗通道先验(dark channel prior, DCP)复原图像中的光晕现象、明亮区域色彩失真、环境光估计不准确等问题,提出了基于超像素暗通道和自动色阶优化的单幅图像去雾算法。首先,由改进的White Patch Retinex算法增强图像并计算精确环境光。接着,在传统暗通道去雾算法中引入超像素图像分割和引导滤波算法,使透射率估计的稳健性与精确性得以提升。然后,采用自适应容差对明亮区域的透射率进行补偿,有效抑制明亮区域色彩失真问题。最后,以自动色阶优化算法提高图像对比度。将本文去雾算法与其他算法从主观和客观两个维度进行比较,实验结果表明:采用不同算法对不同浓度的自然雾图进行对比实验,信息熵提高0.2 bit,峰值信噪比(peak signal-to-noise ratio,PSNR)提高0.8 dB,运行效率提高。该算法对不同浓度含雾图像具有良好的适应性,复原图像色彩真实、纹理清晰、细节丰富,去雾效果良好。 相似文献
7.
Ting-Ting Li An-Pang Chen Po-Wen Hwang Yi-Jun Pan Wen-Hao Hsing Ching-Wen Lou 《Materials and Manufacturing Processes》2018,33(2):149-155
This study presents the synergistic effects of graphene nanosheets (GNSs) and carbon fibers (CFs) additions on the electrical and electromagnetic shielding properties of GNS/CF/polypropylene (PP) composites. These composites were fabricated by the melt blending of different ratios of GNSs and CFs (20:0, 15:5, 10:10, 5:15 and 0:20 wt/wt%) into a PP polymer matrix using a Brabender mixer. Besides, the chemical and crystalline structures and the thermal stability of the resultant GNS/CF/PP composites were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and thermogravimetric analysis (TGA). FT-IR and XRD showed that with the addition of GNSs content, transmittances at 1373.4?cm?1 and 1454.4?cm?1 became smaller and the characteristic peak at 26.82° became stronger. TGA showed that the GNS/CF/PP composite can be used at high temperature below 456°C. Blending 10?wt% CFs and 10?wt% GNSs into the PP polymer resulted in excellent conductivity (0.397 S/cm), which indicated the occurrence of the critical percolation threshold phenomenon, and also reached the maximum electromagnetic shielding effectiveness (EMSE) of 20?dB at 1.28–2.00?GHz. Laminated with five layers of composites, its EMSE achieved 25–38?dB at 0.3–3.0?GHz, corresponding to blocking of 94.38–98.74% electromagnetic waves. 相似文献
8.
Partner selection is a major issue in the formation of a virtual enterprise. In practice, in the partner selection process, the information about the candidates and their performances are incomplete and uncertain. Vague sets theory is one of the methods used to deal with uncertain information. In this paper, a new method based on vague sets is proposed to deal with the partner selection problem in the formation of a virtual enterprise while the factors of satisfaction degree, due date, cost and the precedence of tasks are taken into account. On the basis of the agreement index of satisfaction degree, the formulated partner selection problems are interpreted so as to maximize the minimum agreement index. To solve the problem, an improved particle swarm optimization (PSO) algorithm is proposed. Finally, the simulation of a numerical example demonstrates that the method is effective. 相似文献
9.
In this study, an adaptive fuzzy time series model for forecasting Taiwan’s tourism demand is proposed to further enhance the predicted accuracy. We first transfer fuzzy time series data to the fuzzy logic group, assign weights to each period, and then use the proposed adaptive fuzzy time series model for forecasting in which an enrollment forecasting values is applied to obtain the smallest forecasting error. Finally, an illustrated example for forecasting Taiwan’s tourism demand is used to verify the effectiveness of proposed model and confirmed the potential benefits of the proposed approach with a very small forecasting error MAPE and RMSE. 相似文献
10.
覆盖粗糙集是经典粗糙集的推广,从不同的角度研究覆盖粗糙上近似,就有不同的上近似定义方法。本文将同一覆盖元中的元素理解为相关,从元素相关性角度研究覆盖粗糙集上近似,从点与集合的依赖关系入手,提出覆盖粗糙集阶的概念及覆盖粗糙集依赖上近似的概念,并对覆盖粗糙集的依赖上近似进行分析。从覆盖意义上说,相对于其它上近似,依赖上近似具有覆盖元数量较少的特点,而且具有上近似可定义的特点。 相似文献