N阶色散媒质的FDTD法与数字信号处理技术

提出了一种新的N阶色散媒质的时域分析方法,并将其表征为一组无限冲击响应滤波器,将色散媒质在FDTD中的表述问题转化为数字滤波器(IIR)的设计问题.改进FDTD能分析处理与频率有关的电磁场问题.为验证此方法的有效性和可靠性,用此方法计算了高斯平面波脉冲入射N阶色散媒质的情况,计算结果与解析值非常吻合.     

Hand gesture guided robot-assisted surgery based on a direct augmented reality interface

Radiofrequency (RF) ablation is a good alternative to hepatic resection for treatment of liver tumors. However, accurate needle insertion requires precise hand-eye coordination and is also affected by the difficulty of RF needle navigation. This paper proposes a cooperative surgical robot system, guided by hand gestures and supported by an augmented reality (AR)-based surgical field, for robot-assisted percutaneous treatment. It establishes a robot-assisted natural AR guidance mechanism that incorporates the advantages of the following three aspects: AR visual guidance information, surgeon's experiences and accuracy of robotic surgery. A projector-based AR environment is directly overlaid on a patient to display preoperative and intraoperative information, while a mobile surgical robot system implements specified RF needle insertion plans. Natural hand gestures are used as an intuitive and robust method to interact with both the AR system and surgical robot. The proposed system was evaluated on a mannequin model. Experimental results demonstrated that hand gesture guidance was able to effectively guide the surgical robot, and the robot-assisted implementation was found to improve the accuracy of needle insertion. This human–robot cooperative mechanism is a promising approach for precise transcutaneous ablation therapy.     

玉米田除草剂甲基磺草酮的生物活性及安全性

在温室条件下研究了甲基磺草酮的除草活性、对玉米的安全性以及表面活性剂、温度和降雨对甲基磺草酮除草活性的影响。结果表明，甲基磺草酮土壤处理150g／hm^2，茎叶处理100g/hm^2对杂草的防效可达到80％：在甲基磺草酮正常应用剂量下土壤处理或茎叶处理对玉米安全；表面活性剂快得7的加入可明显提高药效；温度高，有利于甲基磺草酮药效发挥；施药后1h降雨，对甲基磺草酮药效无影响。     

Handling sequential pattern decay: Developing a two-stage collaborative recommender system

This study proposes a sequential pattern based collaborative recommender system that predicts the customer’s time-variant purchase behavior in an e-commerce environment where the customer’s purchase patterns may change gradually. A new two-stage recommendation process is developed to predict customer purchase behavior for the product categories, as well as for product items. The time window weight is introduced to produce sequential patterns closer to the current time period that possess a larger impact on the prediction than patterns relatively far from the current time period. This study is the first to propose time-decaying sequential patterns within a collaborative recommender system. The experimental results show that the proposed system outperforms the traditional collaborative system using a public food mart dataset and a synthetic dataset.     

Preservation of Acidithiobacillus caldus: A moderately thermophilic bacterium and the effect on subsequent bioleaching of chalcopyrite

Four bacterial preservation methods: passage culture, sterile sand tube preservation, freezing preservation and freeze-drying preservation, were used to store Acidithiobacillus caldus strain S2, a moderately thermophilic bacterium. Among the four methods, the second is shown to be the best for short term preservation (6 months), and the fourth is the best for long term preservation (15 months). Specifically, the results show that using the second method, 32% cell viability was obtained after 6 months, and the cell survival rate reaches 17% using the fourth method after 15 months. In the bioleaching experiments, A. caldus strain S2 preserved via the second and the fourth methods, along with Leptospirillum ferriphilum strain YSK, were applied to bioleach chalcopyrite. Under the two preservation methods for A. caldus strain S2, the results show that 3.72 g/L and 1.68 g/L copper are extracted in the first 20 days and the maximum biomass delays to the 15th day and to the 18th day, respectively. When the bioleaching time was extended to the 40th day, copper extraction increased significantly to 5.02 g/L and 4.88 g/L, respectively. However, A. caldus strain S2 under no preservation, along with L. ferriphilum strain YSK, extract only 0.54 g/L Cu from the 20th day to the 40th day and finally release 5.14 g/L Cu. Therefore, the preserved culture shows almost the same total copper extraction as the unpreserved one in 40 days. As a result, sterile sand tube preservation and freeze-drying preservation greatly prolong the lag phase of cell growth without much decrease in the bioleaching ability of A. caldus strain S2.     

化合物性能数据库及智能管理系统的设计与建立

以标准生成热数据为收集依据,建立了含有无机物、一般有机物、含氮有机物、金属有机物、高分子化合物等近5000种化合物的各种重要性能的Access数据库。并以Visual Basic 6.0为语言,编制了大型程序,能对数据库进行智能化管理,查询、检索极为便利,可按一定的格式打印。形成一本内容丰富、数据齐全的化合物性能数据手册。     

Catalytic oxidation of methane over novel Ce–Ni–O mixed oxide catalysts prepared by oxalate gel-coprecipitation

A novel approach for the synthesis of a new type of binary Ce–Ni–O mixed oxide catalysts is reported. The synthesis method involves the homogeneous gel-coprecipitation of oxalate precursor in alcoholic solution followed by calcinations in air. The results show that the as-prepared samples have high specific surface area and high component dispersion, exhibiting remarkably high activity in the catalytic combustion of methane as compared to the catalysts prepared by conventional coprecipitation techniques. It is suggested that the superior catalytic performance of the oxalate gel-coprecipitated Ce–Ni–O mixed oxide catalysts could be attributed to the generation of highly dispersed NiO_x species and the creation of highly active oxygen vacancies as a consequence of an easier incorporation of Ni²⁺ ions into ceria lattice by the formation of solid solution in the mixed oxide samples.     

Predeterminate model of corrosion rate of steel in concrete

The predeterminate model of corrosion rate of steel in concrete, the influence of concrete carbonation exponent and cover thickness to steel corrosion rate, and relationships among steel diameter, cover thickness and exposure time to steel corrosion rate are mainly studied. It is shown that (1) the steel corrosion rate increases when the concrete carbonation exponent increases. (2) The steel corrosion rate decreases when a mild carbon steel with circular diameter in concrete increases. The more the concrete carbonation exponent becomes larger, the more the effect of steel diameter obviously appears. (3) The steel corrosion rate increases when the concrete cover thickness decreases. (4) The steel corrosion rate obviously increases when the exposure time decreases. The results of present studies are discussed in comparison with earlier findings.     

1021 t/h锅炉排烟温度偏高的原因分析及改进建议

本文提针对青山电厂１２号锅炉排烟温度偏高的问题,通过对现场运行情况和测试数据的分析以及各种理论计算结果的比较,初步找出了排烟温度偏高的原因,并提出了降低排烟温度的措施。     

Imaging tissue engineering scaffolds using multiphoton microscopy

In this study, we combined two-photon autofluorescence and second harmonic generation imaging to investigate the three-dimensional microstructure and nonlinear optical properties of tissue engineering scaffolds. We focused on five different types of scaffold materials commonly used in tissue engineering, including: open-cell polylactic acid, polyglycolic acid, collagen composite scaffold, collagraft bone graft matrix strip, and nylon. By the use of multiphoton microscopy and a motorized stage, we obtained high resolution, spectrally resolved structural information of the scaffolds over large areas or in three-dimensions. Our results show that the nonlinear optical properties of the scaffolds will enable us to spectrally and morphologically distinguish the different types of scaffold materials investigated. We envision multiphoton microscopy to be a useful technique in tissue engineering applications in understanding the interplay between cultured cells and the scaffold materials.