应重视三角形重心性质在解平几题中的作用

初中《几何》第二册第35页黑体字为:三角形重心与顶点的距离等于它与对边中点的距离的两倍。这就是三角形的重心性质。由于课本没有相应的例题和未发现能用这一性质解的习题,往往在教学完这一性质后,学生不能得到及时的巩固和训练,易被师生所忽视,甚至被遗忘,其实在解某些平几题中,若能应用这个性质去解,显得简便。因此,笔者认为,这个性质有必要引起师生的重视,下面给出应用三角形重心性质解题的几个方面,以说明上述观点。一、用于求边长例1 如图1,在直角三角形ABC中,∠A=90°,AB=61/2。

Psycho-Sexual Construction of the Subjects in Sudhir Kakar＇s The Ascetic of Desire

This paper is a study of Kakar＇s The Ascetic of Desire from psychoanalytic perspective. The analyses are based on the psychoanalytic theories and concepts posited by Sigmund Freud. The focus of the study is on the psycho-sexual construction of the subjects in the concerned novel, how a subject develops sexually, how sexuality affects the psychological growth of the subject, the factors that hamper a subject＇s psycho-sexual growth, and how psycho-sexual growth ultimately transforms a subject both psychologically and socially. As the novel is written by a both psychoanalyst and novelist, Sudhir Kakar, the scope of the study becomes undoubtedly rich.

Bending Strength Properties of Finger Jointed Off-Cut Yellow Meranti （Shorea spp.） Wood

This study was undertaken to determine the bending strength properties of off-cut Yellow Meranti wood by applying the finger jointed techniques. The finger orientations that were used in this study are vertical and horizontal finger orientation. Specimens were bonded with PVAc （polyvinyl acetate）. The bending strength properties were determined by the three point and four point bending test method. The results show that vertical finger orientation has the higher mean of modulus of rupture and the modulus of elasticity value of 24.49 MPa （28.91 MPa） and 8,814 MPa （11,668 MPa） respectively. However, the tested specimen properties did not meet the minimum strength of the solid （control） specimens.

Simulating the particle size distribution of rockfill materials based on its statistical regularity

The particle size distribution of rockfill is studied by using granular mechanics, mesomechanics and probability statistics to reveal the relationship of the distribution of particle size to that of the potential energy intensity before fragmentation, which finds out that the potential energy density has a linear relation to the logarithm of particle size and deduces that the distribution of the logarithm of particle size conforms to normal distribution because the distribution of the potential energy density does so. Based on this finding and by including the energy principle of rock fragmentation, the logarithm distribution model of particle size is formulated, which uncovers the natural characteristics of particle sizes on statistical distribution. Exploring the properties of the average value, the expectation, and the unbiased variance of particle size indicates that the expectation does notequal to the average value, but increases with increasing particle size and its ununiformity, and is always larger than the average value, and the unbiased variance increases as the ununiformity and geometric average value increase. A case study proves that the simulated results by the proposed logarithm distribution model accord with the actual data. It is concluded that the logarithm distribution model and Kuz-Ram model can be used to forecast the particle-size distribution of inartificial rockfill while for blasted rockfill, Kuz-Ram model is an option, and in combined application of the two models, it is necessary to do field tests to adjust some parameters of the model.

Recent progress on nanostructured conducting polymers and composites:synthesis,application and future aspects

Conducting polymers （CPs） have been widely investigated due to their extraordinary advantages over the traditional materials, including wide and tunable electrical conductivity, facile production approach, high mechanical stability, light weight, low cost and ease in material processing. Compared with bulk CPs, nanostructured CPs possess higher electrical conductivity, larger surface area, superior electro- chemical activity, which make them suitable for various ap- plications. Hybridization of CPs with other nanomaterials has obtained promising functional nanocomposites and achieved improved performance in different areas, such as energy sto- rage, sensors, energy harvesting and protection applications. In this review, recent progress on nanostructured CPs and their composites is summarized from research all over the world in more than 400 references, especially from the last three years. The relevant synthesizing experiences are outlined and abundant application examples are illustrated. The ap- proaches of production of nanostructured CPs are discussed and the efficacy and benefits of newest trends for the pre- paration of multifunctional nanomaterials/nanocomposites are presented. Mechanism of their electrical conductivity and the ways to tailor their properties are investigated. The re- maining challenges in developing better CPs based nanoma- terials are also elaborated.