中国畜牧业现状与可持续发展措施的研究

畜牧业是否成长为农村经济的支柱产业,是衡量一个国家农业发达程度的主要标志。现阶段.我国畜牧业的增长方式、发展路径、动力、市场和地位都发生了重大变化,给畜牧业的可持续发展提出了许多新问题和新挑战。近年来.我国畜牧业的发展取得了举世嘱目的成就,促进了国民经济的快速发展,丰富了城乡人民物质和文化生活的需要。随着经济的发展和人们生活水平的逐步提高.对畜牧产品的需求将有较大增长,大力加强和发展畜牧业将是我国农业的最终方向。依据现有统计资料,结合我国畜牧业的实际情况,根据"十一五"规划和建设社会主义新农村的要求,文章分析了畜牧业发展的地位,探讨了畜牧业存在的问题.并提出了相应的对策和建议。

Analysis of Si/GaAs Bonding Stresses with the Finite Element Method

In conjunction with ANSYS, we use the finite element method to analyze the bonding stresses of Si/GaAs. We also apply a numerical model to investigate a contour map and the distribution of normal stress,shearing stress,and peeling stress,taking into full consideration the thermal expansion coefficient as a function of temperature. Novel bonding structures are proposed for reducing the effect of thermal stress as compared with conventional structures. Calculations show the validity of this new structure.

中国水蚀土壤抗剪强度研究

利用野外测试数据、土壤样品的室内理化分析数据和参考文献数据 ,对水蚀区范围内水土流失过程中的土壤抗剪强度进行了初步研究 ,建立了中国水土流失土壤抗剪强度的回归模型 ,总结出水蚀区范围内水蚀过程中有关土壤抗剪强度的 3条结论 :影响水土流失过程中土壤抗剪强度的主导因素是容重、粉 /黏、土壤含水量、土壤有机质含量 ;抗剪强度随土壤类型发生有规律的变化 ;抗剪强度在中国水蚀区范围内有较明显的空间分异规律 (包括水平分异规律和垂直剖面构型规律 )

Effect of shear on the crystallization behavior of glass bead filled polypropylene

Linkam CSS450 optical shearing stage, wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering(SAXS) were used to investigate the effect of shear on crystal structure and crystallization morphology of the glass bead filled polypropylene( PP). The results indicate that the glass bead worked as nucleating agent for the glass bead filled PP, compared with pure PP it restrained the formation of beta-crystal after shear treatment. When the mean size of glass bead is smaller(4 mu m) shear rate had less effect on the formation of beta-crystal of PP obviously.

First-principles investigation on the elastic, magnetic and electronic properties of MFe3N (M = Fe, Ru, Os)

The elastic, magnetic and electronic properties of MFe3N (M = Fe, Ru, Os) are investigated via first-principles calculations. The calculated results are in agreement with the experimental and other theoretical data. The high ratios of bulk modulus to shear modulus 2.7, 2.0, and 1.8 for gamma'-Fe4N, RuFe3N, and OsFe3N, respectively, indicate that they have good ductility. gamma'-Fe4N possesses the largest B/C-44 (3.41) ratio, which suggests that it is much prone to shearing. The net magnetic moment per formula unit decreases from 9.90 for gamma'-Fe4N, 7.66 for RuFe3N, to 6.80 mu(B) for OsFe3N.

Ordering-induced micro-bands in thin films of a main-chain liquid crystalline chloro-poly(aryl ether ketone)

Micro-banded textures developed from thin films of a main-chain thermotropic liquid crystalline chloro-poly(aryl ether ketone) in the melt were investigated using transmission electron microscopy (TEM). selective area electron diffraction, and atomic force microscopy techniques. The micro-banded textures were formed in the copolymer thin films after annealing at temperatures between 320 and 330degreesC, where a highly ordered smectic crystalline phase is formed without mechanical shearing. The micro-banded textures displayed a sinusoidal-like periodicity with a spacing of 150 nm and an amplitude of 2 rim. The long axis of the banded texture was parallel to the b-axis of an orthorhombic unit cell. In the convex regions, the molecular chains exhibited a homeotropic alignment, i.e. the chain direction was parallel to the film normal. In the concave re-ions, the molecular chains possessed a tilted alignment. In addition to the effects of annealing temperatures and times, the thickness of the film played a vital role in the formation of the banded texture. A possible formation mechanism of this banded texture vas also suggested and discussed. It was suggested that the micro-bands were formed during cooling.

Influence of shear on polypropylene crystallization kinetics

Isothermal crystallization kinetics under shear in the melt of iPP was investigated by optical microscopy. It appears that shearing from 200 to the crystallization temperatures enhanced the kinetics, but the shear effect was not obvious if the melt of iPP was sheared only at 200. The experiment results show that relaxation plays an important role during crystallization, and that spherulite growth rates increased with shear rates and were governed by relaxation. The effect of flow on the crystallization kinetics can be understood by considering that the increase of the degree of order due to flow results is an effective change of the melt free energy. The Laurizen-Hoffman theory and the DE-IAA model were used to describe the shear-induced crystallization kinetics of iPP excellently.

Shear induced molecular alignments of a side-chain liquid crystalline polyacetylene containing biphenyl mesogens

Mesomorphic properties of a side chain liquid crystalline polyacetylene, poly(11-{[(4'-heptyloxy-4-biphenylyl)carbonyl]oxy}-1-undecyne) (PA9EO7), are investigated using polarized optical microscope, X-ray diffraction, and transmission electron microscope. Polymer PA9EO7 forms enantiotropic smectic A and smectic B phases. It also exhibits an additional high order smectic phase, a sandwich structure consisting of different molecular packing of biphenyl mesogenic moieties from that of alkyl spacers and terminals, when it is prepared from its toluene solution. Shearing the polymer film at its smectic A phase generates banded texture with the alignment of the backbones parallel to the direction of shear force. While at its high order smectic phase, the mesogen pendants of the polymer are arranged parallel to the direction of shear. The different mesomorphic behaviors arise from different molecular alignments influenced by the fluidity.

Surface morphology evolution of thin triblock copolymer films during spin coating

The surface morphology evolution of thin poly(styrene-block-ethylene/butylenes-block-styrene) (SEBS) triblock copolymer films as a function of the copolymer concentration was investigated by means of dynamic mode atomic force microscopy. At a relatively low copolymer concentration (0.025% w/v), the periodically orientated stripes were observed. This kind of surface patterning produced in the spin-coating process has not been reported in the literature before. It has been shown by our experiment that a shearing and stretching field can cause flexible polymer coils or aggregates to orientate during the spin coatings At a copolymer concentration of 0.05% w/v, SEBS molecule aggregates form network structures in the whole film. With further increase of the copolymer concentration, a continuous film with a microphase-separated structure was visualized.

Oriented crystallization process of polypropylene fractions

Melting recrystallization processes of melt-sheared films of polypropylene (S28C) fractions have been investigated in situ by polarized optical microscope equipped with CCD camera and hot-stage. Actually, the morphological developments in the melting recrystallization are partially reappearance of oriented crystallization processes during melt-shearing the fractions, which is due to a memory effect of oriented structure of polymer. For low molecular weight fraction, only incomplete spherulites with some orientation along shear direction are observed in the melting recrystallization processes of the sheared films. For middle molecular weight fractions, extended chain fiber crystals(or bands) are formed first at higher temperatures, and the bands can act as self-nuclei (i. e., row nuclei), resulting in epitaxial growth of chain-folded lamellae(or fibril), i. e., the formation of cylindrites, with further decrease of the crystallization temperature. For high molecular weight fraction, however, it is not possible to shear the melt film because of its high melt viscosity. When the low molecular weight fraction in which no fiber crystals or cylindrites are observed, are mixed with small amount(about 1%-2%) of the high molecular weight fraction, quite large number of cylindrites are formed during the melting recrystallization process of its sheared film, which implies that the component of high molecular weight plays an important role in the formation of cylindrites during the shear process of polypropylene.

Shear-induced spiral-like morphology of a main-chain liquid crystalline poly(aryl ether ketone)

The shear-induced spiral-like morphology of a main-chain thermotropic liquid crystalline poly(aryl ether ketone) is observed and characterized by means of polarizing light microscopy, atomic force microscopy, transmission electron microscopy and electron diffraction techniques. The spiral-like texture is formed during shearing in the temperature range of liquid crystalline to isotropic transition (335-340 degreesC), and dispersed discontinuously in the mosaic matrix. Electron diffraction results indicate that the spiral exhibits orthorhombic lateral packing of the crystals and homeotropic alignment of the molecules. The spiral formation process and possible affecting factors are discussed.

The rheological and extrusion behaviour of blends based on phenolphthalein poly(ether-ether-sulfone) and thermotropic liquid crystalline polymer

A novel engineering thermoplastic, phenolphthalein poly (ether-ether-sulfone) (PES-C) was blended with a commercial thermotropic liquid crystalline polymer(TLCP), Vectra A950, up to 30 weight percent of TLCP. A rheometrics dynamic spectrometer (RDS-I) and a CEAST capillary rheometer, a rheoscope 1000 were employed to investigate the melt rheology and extrusion behaviour at both the low and high shearing rates. The morphologies of the blends under different shearing were observed with a scanning electron microscope(SEM) and correlated to the observed rheology. The principal normal stress differences measured with cone-and-plate geometry give a temperature-independent correlation for both blend and PES-C when they are plotted against shear stress. But the extrudate swell of the blends showed a strong temperature dependence at each shear stress. The concentration dependence of extrudate swell shows a contrary behaviour to that of the inorganic filled system. A reasonable hypothesis based on the relaxation and disorientation of TLCP during flowing in the capillary and exiting was given to explain it. The melt fracture was checked after extrusion from capillary and was discussed.

The synthesis and characterization of the novel poly(aryl ether ketone)s with liquid crystallinity

The novel poly(aryl ether ketone)s with liquid crystallinity were synthesized by nucleophilic substitution reactions of 4,4'-biphenol and substituted hydroquinone with 4,4'-difluorobenzophenone and their thermotropic liquid crystalline properties were characterized by DSC, PLM and WAXD, The copolymers containing 70% biphenol formed nematic phase while the copolymer containing 50% biphenol exhibited smectic texture, The banded textures were formed after shearing the sample in the nematic liquid crystalline state. The identification of the structures in each mesogenic phase has been carried out by combining WAXD with PLM and DSC.

The synthesis and thermotropic liquid crystalline behaviour of novel main chain poly(aryl ether ketone)s containing a lateral phenyl group

Novel main chain poly(aryl ether ketone)s containing a lateral phenyl group were synthesized by nucleophilic substitution reactions of 4,4'-biphenol and phenylhydroquinone with either 4,4'-difluorobenzophenone or 1,4-bis(4-fluorobenzoyl)benzene and their thermotropic liquid crystalline properties were characterized by a variety of experimental techniques. Thermotropic liquid crystalline behaviour was observed in the copolymers containing 50 and 70mol% biphenol. Melting (T-m) and isotropization (T-i) transitions both appeared on the DSC thermograms. A banded texture was formed after shearing the sample in the liquid crystalline nematic state. As expected, each of the copolymers had a relatively lower melting transition than the biphenol-based homopoly(aryl ether ketone)s because of the copolymerization effect of the crystal-disrupting monomer phenylhydroquinone.

The synthesis and thermotropic liquid crystalline behavior of the novel poly(aryl ether ketone)s containing chloro-side group

The novel poly(aryl ether ketone)s containing chloro-side group were synthesized by nucleophilic substitution reactions of 4,4'-biphenol and chlorohydroquinone with either 4,4'-difluorobenzophenone(BP/CH/DF) or 1,4-bis(p-fluorobenzoyl)benzene (BP/CH/BF) and their thermotropic liquid crystalline properties were characterized by a variety of experimental techniques. The thermotropic liquid crystalline behavior was observed in the copolymers containing 50 and 70% biphenol. Melting transition (Tm) and isotropization transition (Ti) both appeared in the DSC thermograms. A banded texture was formed after shearing the sample in the liquid crystalline state. The novel poly(aryl ether ketone)s had relatively higher glass transition temperature (Tg) in the range of 168 similar to 200 degrees C and lower melting temperature (Tm) in the range of 290 similar to 340 degrees C. The thermal stability (Td) was in the range of 430 similar to 490 degrees C.