Fractal analysis of crack paths in Al_2O_3-TiC-4%Co composites

Al2O3-TiC-4%Co(volume fraction) composites(ATC) with high toughness (7.8±0.8 MPa·m1/2) and strength (782±60 MPa) were fabricated. In comparison with Al2O3-TiC composites(AT), the fracture toughness was significantly improved by 60%. The crack paths, generated by Vickers indentation on the polished surfaces of both composites, were analyzed from a fractal point of view to distinguish the possible toughening mechanisms involved. Quantitative evaluation of indentation cracks indicates that the crack deflection plays a more effective role. Cracks of the ATC composites show higher deflection angles and more deflections along the path. ATC composites present higher fractal dimension (D=1.07) than AT composites (D=1.02), which is directly related to the higher fracture toughness. A significant relationship between crack path and toughness is evident: the more irregular the geometry of the crack, the higher the fracture toughness.

Toward a fractal spectrum approach for neutron and gamma pulse shape discrimination

Accurately selecting neutron signals and discriminating γsignals from a mixed radiation field is a key research issue in neutron detection. This paper proposes a fractal spectrum discrimination approach by means of different spectral characteristics of neutrons and γ rays. Figure of merit and average discriminant error ratio are used together to evaluate the discrimination effects. Different neutron and γ signals with various noise and pulse pile-up are simulated according to real data in the literature. The proposed approach is compared with the digital charge integration and pulse gradient methods. It is found that the fractal approach exhibits the best discrimination performance, followed by the digital charge integration method and the pulse gradient method, respectively. The fractal spectrum approach is not sensitive to high frequency noise and pulse pile-up. This means that the proposed approach has superior performance for effective and efficient anti-noise and high discrimination in neutron detection.

保安湖莲群丛分布格局分形特征的初步研究

应用非线性科学中的分形几何理论，以保安湖扁担塘湖汊中的莲群丛为对象，研究该群丛小尺度水平格局的分形特征。主要应用计盒维数和信息维数公式计算群丛中莲种群和菱种群的个体分布格局的分维值，莲的计盒维数为1.92，信息维数为1.88；菱的计盒维数为1.04，信息维数为1.11。表明在采样区莲的空间占有程度远大于菱，是该时期的优势种，而菱则成为伴生种。莲在各尺度上的分布较均匀。最后讨论了莲的分维值在连续样方上的变化。

基于形态学梯度的红外图像分割算法

提出了一种新的红外图像分割方法。该方法利用形态学方法来处理红外图像。首先进行形态学滤波,对红外目标图像中的噪声和微小的干扰区域进行滤除,接着提出了一种计算红外图像梯度的多尺度算法提取图像形态学梯度,而后分析了图像分形特征估计方法与形态学梯度的关系,提出了一种新的红外图像分形特征估计算法,在此基础上对图像进行分割。实验结果表明,该算法能较好地解决红外图像的分割问题。

CFD Based Study of Heterogeneous Microclimate in a Typical Chinese Greenhouse in Central China

Indoor microclimate is important for crop production and quality in greenhouse cultivation. This paper focuses on microclimate study based on a computational fluid dynamics （CFD） model of a typical plastic greenhouse （with a sector shape vertical cross-section） popularly used in central China. A radiation model is added into the CFD model so as to simulate coupling of convective transfers and radiative exchanges at the cover and the roof, instead of using the usual coupling approach based on energy balance. In addition, a fractal permeability model is innovatively adopted in the modeling of the crop canopy. Compared the numerical results with measured experimental data, the model simulation is proved with success. This model then is used to explore the microclimate variable distributions in the greenhouse. It shows that the airflow pattern, temperature and humidity profiles are different from those in a sawtooth Mediterranean- type greenhouse. The study suggests that this deliberately developed CFD model can be served as a useful tool in macroclimate research and greenhouse design investigating.

分形理论评价纳米SiO_2对水泥早期水化的影响

根据分形几何理论评价超细粉体的活性,探讨纳米SiO2对水泥早期水化的影响。用激光粒度分布仪测试水泥试样在早期水化时的颗粒分布状况,应用分形理论分析评价了水泥试样的粒度分布特征,测试、计算了不同试样相应的分形维数。研究结果表明,随水化时间的增加,掺入纳米SiO2的水泥试样的分数维的数值变化的程度更大一些,掺入纳米SiO2的水泥试样水化更快,进而说明了由于纳米SiO2具有更高的火山灰活性而促进了熟料水化更快。

测定凝胶化的PVF缩醛度的新溶剂体系

本文论述了不溶于水－乙醇体系的凝胶化的聚乙烯醇缩甲醛（ＰＶＦ）缩醛度测定的方法．通过反复实验找到一种合适的溶剂体系，使测定方法简便、准确，并通过对比实验验证了该方法的可靠性和准确性．

Morphology characteristics of joint surface in rock mass

In order to quantify the characteristics of the surface of jointed rock mass,new equipment,the three-dimensional laser surface topography instrument,was used to accurately measure surface morphology of joints.Scan pictures and parameters were obtained to describe the rock joint surface characteristics,for example,the height frequency of surface,and mean square roughness.Using the method of fractal dimension,the values of joint roughness coefficient(JRC) were calculated based on the above parameters.It could access to the joint surface rock sample morphology of the main parameters of characteristic.The maximum peak height is 2.692 mm in the test joint plane.The maximum profile height is 4.408 mm.JRC value is 6.38 by fractal dimension computing.It belongs to the smooth joint surface.The results show that it is a kind of the effective method to quantitatively evaluate the surface topography by the three-dimensional laser surface topography instrument and the fractal dimension method.According to the results,during the process of underground large-scale mining,safe measures to prevent slip failure of the joint plane by controlling surface tension and shear mechanical response were proposed.

4-氨基丁醛缩乙二醇的合成

以四氢呋喃为原料,经氯化氢开环、PCC氧化、乙二醇缩醛化和Gabriel反应4步合成了标题化合物,总收率21.3%。