直面世俗的偏见

行知中学对职校生的认知其实是社会对职校生认知的一个缩影。我们唯有直面并理性审视这种偏见,定信念、强内功、塑形象、展风采,以自己的积极作为化解这种偏见,才能赢得属于职业学校和职校生的尊严。由于众所周知的原因,职业学校基本都是＂无门槛＂或＂低门槛＂入学,如果按照义务教育的评价标准,职校生基本都是＂低成就生＂,是义务教育的＂失意者＂,也难怪社会上有人把职业学校形容为＂收容所＂＂难民营＂。这种评价标准也逐渐转化为社会的＂共识＂,

Tensile properties and hot extrusion behavior of Zn O-coated Mg_2B_2O_(5w)/6061 Al composites

The 6061 aluminum matrix composites reinforced with ZnO-coated Mg_2B_2O_5w were fabricated by squeeze casting method and followed by extruded under a technical equivalent condition. The mechanical properties and microstructures of the composites were investigated. The results showed that the elastic modulus of the as-cast composites increased straightly with increasing ZnO coating content. The ultimate tensile strength and yield strength of the as-cast composites rapidly increased initially and then declined with increasing ZnO coating content. However, the elongations of all the as-cast composites had similar values. The elongations of the composites were highly enhanced and the ultimate tensile strength of the composite without ZnO coating was the largest after extrusion. A number of whiskers in the composites with ZnO coating were fractured during the extrusion process, but the whiskers＇ breakage extent was limited with the increase of coating content.

谈钢琴音板

钢琴音板在钢琴中占有十分重要的地位。钢琴的6000多个部件中,音板是决定音色优劣、音量(响度)大小和发音持久与否的关键。钢琴弦被小槌敲击发生振动,只能激起有限的空气发生振动,不能带动足够的空气发生振动,也不能使声波持续足够长的时间。但是,当琴弦发生振动时。

Fractal analysis of fracture surfaces in aluminum borate whisker-reinforced aluminum alloy 6061 composite

The effect of interface reaction on the fractal dimensions of fracture surface in aluminum borate whisker-reinforced aluminum alloy 6061 composite was investigated. The composite was fabricated by squeeze-casting technique. The fracture surfaces created in tensile test were measured by vertical sectioning method. Fractal phenomena were found in two plots, in which the measuring units were from 3 to 15 μm and 1 to 5 μm, respectively. The relation was established between the tensile properties and fractal dimension with measuring units of 3-15 μm. The results show that the ultimate tensile strength increases while the fracture surface roughness increases with fractal dimension increasing due to the change in fracture mode depending on the degree of interface reaction status induced by heat treatment. But when the measuring units are 1-5 μm, fractal dimension does not change with heat treatment.

Microstructural aspects of in-situ TiB reinforced Ti-6Al-4V composite processed by spark plasma sintering

Titanium-matrix composites have important and wide applications in the transport and aerospace industries. The current research was focused on powder metallurgy processing of in-situ reinforced titanium-matrix composite with Ti B whiskers. The Ti-6Al-4V alloy and B4 C additive powders were used as raw materials. Two different consolidation techniques, namely press-and-sintering and spark plasma sintering, were selected. It was observed that in-situ Ti B whiskers were formed during sintering in both methods. The changes in size, aspect ratio and distribution of in-situ whiskers in different composite samples were monitored. The effect of spark plasma sintering temperature on the synthesis of in-situ whiskers was also investigated. Based on the microstructural observations（optical microscopy and scanning electron microscopy） and the energy dispersive spectroscopy analysis, it was concluded that increasing the spark plasma sintering temperature from 900 to 1100 °C would lead to the complete formation of in-situ Ti B whiskers and reduced porosity content.

Identification of a Putative Tetrasporophyte-Specific Gene in Gracilaria lemaneiformis(Gracilariales,Rhodophyte)

A putative tetrasporophyte-specific gene,designated as SSH466(GenBank accession No. DQ019223) ,was one of the genes identified in this work using suppression subtractive hybridization(SSH) method in Gracilaria lemaneiformis. The full length of the gene was obtained using SMART RACE strategy. Sequence analysis revealed that the gene had 1 019 nucleotides,including an open reading frame of 498 nucleotides encoding 166 amino acid residues,158 nucleotides of 5' untranslated region and 363 nucleotides of 3' non-coding region. Protein motif and secondary structure prediction showed that there existed a transmembrane domain with a unique β-sheet. Thus,SSH466 protein might be a cross-membrane protein. Sequence homology search in the public GenBank databases did not reveal any significant match with SSH466. Virtual Northern blot analysis confirmed that it was a tetrasporophyte-specific gene.

Microstructures and interfacial interactions of Al_(2)O_(3)whiskers and graphene nano-platelets co-reinforced copper matrix composites

The mechanical properties and microstructures of Al_(2)O_(3)whiskers and graphene nano-platelets(GNPs)co-reinforced Cu-matrix composites were studied.Cu-matrix composites with a variation of GNPs amount were fabricated by mechanical alloying followed by vacuum hot-pressing sintering and hot isostatic pressing.The Cu-matrix composite with 0.5 wt.%GNPs(GNPs-0.5)suggests a good interfacial bonding of both Cu/C and Cu/Al_(2)O_(3)interfaces.Both the hardness and compressive strength of Cu-matrix composites show a consistent tendency that firstly increases to a critical value and then decreases with increasing GNPs amount.It is suggested that the most possible strengthening mechanisms of both GNPs and Al_(2)O_(3)whisker working in the Cu-matrix composites involve energy dissipating and load transfer,as well as grain refinements for GNPs.The synergetic effect of GNPs and Al_(2)O_(3)whiskers is highlighted that the embedded GNPs would hinder the crack path generated at the Al_(2)O_(3)/Cu interface and enhance the already outstanding strengthening effect that Al_(2)O_(3)whiskers provide.

Effects of whisker surface treatment on microstructure and properties of Al_(18)B_4O_(33w)/6061Al composites

6061Al matrix composites reinforced by ZnO-coated Al18B4O33 whiskers were fabricated by a semi-solid mechanical stirring technique.The effects of ZnO coating on interfacial reaction between whiskers and matrix and the tensile properties of the composites were investigated.Tensile tests on composites were performed at room temperature,and microstructures were observed by scanning electron microscopy(SEM).The results show that the surface treatment of whiskers could reduce interfacial reaction effectively,improve the wettability between whiskers and matrix and enhance the tensile properties of the composites obviously.In addition,semi-solid stirring parameters were also under preliminary study.The stirring parameters were determined by the distribution of whiskers in the composites.The composites with homogeneously distributed whiskers were fabricated by semi-solid stirring at 610 ℃ for 30 min.

Hydrothermal synthesis of calcium sulfate whisker from flue gas desulfurization gypsum

Plenty of flue gas desulfurization(FGD) gypsum generated from coal-fired power plants for sulfur dioxide sequestration caused many environmental issues. Preparing calcium sulfate whisker(CSW) from FGD gypsum by hydrothermal synthesis is considered to be a promising approach to solve this troublesome problem and utilize calcium sulfate in a high-value-added way. The effects of particle size of FGD gypsum, slurry concentration,and additives on CSW were investigated in this work. The results indicated that fine particle size of FGD gypsum and moderately high slurry concentration were beneficial for crystal nucleation and growth. Three additives of magnesium chloride, citric acid, and sodium dodecyl benzene sulfonate(SDBS) were employed in this study. It was found that mean length and aspect ratio of CSW were both decreased by the usage of magnesium chloride,while a small quantity of citric acid or SDBS could improve the CSW morphology. When multi-additives of citric acid-SDBS were employed, the mean length and aspect ratio increased more than 20%. Moreover, surface morphology of CSW went better, and the particle size and crystal shape became more uniform.

Milling Machinability of TiC Particle and TiB Whisker Hybrid Reinforced Titanium Matrix Composites

The milling machinabilities of titanium matrix composites were comprehensively evaluated to provide a theoretical basis for cutting parameter determination. Polycrystalline diamond （PCD） tools with different grain sizes and geometries, and carbide tools with and without coatings were used in the experiments. Milling forces, milling temperatures, tool lifetimes, tool wear, and machined surface integrities were investigated. The PCD tool required a primary cutting force 15 % smaller than that of the carbide tool, while the uncoated carbide tool required a primary cutting force 10% higher than that of the TiA1N-eoated tool. A cutting force of 300 N per millimeter of the cutting edge （300 N/mm） was measured. This caused excessive tool chipping. The cutting temperature of the PCD tool was 20%-30% lower than that of the carbide tool, while that of the TiA1N-coated tool was 12% lower than that of the uncoated carbide tool. The cutting temperatures produced when using water-based cooling and minimal quantity lubrication （MQL） were reduced by 100 ~C and 200 ~C, compared with those recorded with dry cutting, respectively. In general, the PCD tool lifetimes were 2--3 times longer than the carbide tool lifetimes. The roughness Ra of the machined surface was less than 0.6μm, and the depth of the machined surface hardened layer was in the range of 0.15-0.25 mm for all of the PCD tools before a flank wear land of 0.2 mm was reached. The PCD tool with a 0.8 mm tool nose radius, 0% rake angle, 10% flank angle, and grain size of （30＋2） μm exhibited the best cutting performance. For this specific tool, a lifetime of 16 rain can be expected.

从创新源头挖掘价值——中国证券投资基金业协会会长洪磊谈私募基金行业发展

“私募基金是价值企业的发现者,价值投资的管理者,价值创造的推动者,在“新思路、新产业、新业态”环境中,迎来历史性发展机遇。”在第十届中国企业国际融资洽谈会论坛的分论坛“新思路、新产业、新业态——中国私募基金业2016论坛”上,中国证券投资基金业协会会长洪磊从行业发展的角度,谈了对私募基金行业发展的几点思考。