煤矿井田区地表沉陷对植被景观的影响——以山西省晋城市东大煤矿为例

借助地表沉陷预测模型,预测了地表沉陷状况,依据地表沉陷对景观的破坏程度划分出重度影响区和轻度影响区;在遥感及地理信息系统技术的支持下,把植被景观现状与地表沉陷影响区叠加,通过沉陷前后景观格局的变化分析,对山西省晋城市东大煤矿的生态影响进行了探索性评价研究。结果表明:1)重度影响区地表会出现盆型、马鞍型和波浪型等塌陷或裂缝,土壤侵蚀的作用将导致土壤养分空间格局发生明显变化。塌陷或裂缝周围生境恶化,成为养分流失源,植被恢复困难;养分汇处土壤水、肥条件优越,植被演替迅速,适当的人为干扰可以加快区域生态环境的恢复步伐。2)地表沉陷后,植被景观破碎及隔离程度严重,原有的稳定态景观格局被打破,随着地形、土壤的空间变化,植被开始新一轮发展演替。由于原先占绝对优势的退化植被类型白羊草(Bothriochloaische-mum)_百里香(Thymusmongolicus)型优势度下降,同时,大部分次优势景观的内部生态功能受影响不大,这对景观整体的生物多样性以及次优势景观类型的演替是有益的,但是,重度影响区对斑块的隔离呈直线性,这对物种迁移的障碍是明显的。因此,重视井田区的封育与引种工作,科学规划、合理布局,在此基础上,引导植被演替沿着白羊草_百里香型—白羊草_黄背草(Themedajaponica)型—灌木丛—阔叶林的方向发展是可行的。

基于音高分析的学习者语块质量研究

本研究借鉴语调研究领域中的相关研究成果,尝试从音高分析的角度考察中国英语学习者朗读口语中的语块质量问题。研究发现:和本族语者相比,学习者语块具有音高范围较窄、音高走势"前低后高"、以及衔接缺乏连贯性的特点,这表明其内部凝结度尚需改善。本研究提醒我们关注语块的韵律性,对英语口语教学具有一定的指导意义。

Effect of configuration on magnetic field in cold crucible using for continuous melting and directional solidification

To improve the power efficiency and optimize the configuration of cold crucible using for continuous melting and directional solidification （DS）, based on experimental verification, 3D finite element （FE） models with various configuration-elements were developed to investigate the magnetic field in cold crucible. Magnetic flux density （B） was measured and calculated under different configuration parameters. These parameters include the inner diameter （D2）, the slit width （d）, the thickness of crucible wall, the section shape of the slit and the shield ring. The results show that the magnetic flux density in z direction （Bz） both at the slit and at the midpoint of segment will increase with the decrease of D2 or with the increase of the width of the slit and the section area of wedge slit or removing the shield ring. In addition, there is a worst wall thickness that can induce the minimum Bz for a cold crucible with a certain outer diameter.

Measurement and theoretical analysis of solar temperature field in steel-concrete composite girder

The solar temperature field of a large three-span continuous bridge with steel-concrete composite box girder and variable cross-section is measured to verify a calculation method for the temperature field of steel-concrete composite beams. The test results show that the temperature of an external steel web- plate is higher than that of an internal web-plate due to the difference in solar radiation. Air temperature inside the box matches the average temperature of the whole steel box. Based on actual measurements, a transient thermal analysis with multiple boundary conditions is also carried out by a software program ANSYS. Convective boundary situation and states of solar radiation on steel web plates in different situations are determined in the analysis. The feature of the temperature field is preliminarily achieved through a comparative study between the actual measurement and the finite element analysis. The computed results are in good consistence with the actual measurement results, with the maximum difference within 2 ℃. This indicates that the theoretical calculation method is reliable and it provides a foundation for further research on temperature field distribution in the steel-concrete composite box girder.

建筑施工管理过程中各专业的协作与配合

近年来,伴随着我国社会经济的发展,我国建筑领域也得到了快速的发展。然而,在建筑领域发展的过程中,做好建筑施工协调管理工作是十分重要的。在建筑施工管理中,各专业的协调管理工作是尤为重要的。有效的协调管理工作能够加强各部门、各企业之间的联系,提升各专业之间的凝结度,通过协调与配合保证建筑项目的施工质量,促使建筑项目能够在计划工期内顺利完成建设目标。由此可见,做好建筑施工过程中各专业的协作与配合是十分有必要的。

Effect of melt superheat on structural uniformity of lotus-type porous metals prepared by unidirectional solidification

Structural uniformity is an important parameter influencing physical and mechanical properties of lotus-type porous metals prepared by directional solidification of metal-gas eutectic (Gasar). The effect of superheat on structural uniformity as well as average porosity, pore morphology of porous metals was studied. The experimental results show that, when the superheat is higher than a critical value (ΔTc), the bubbling or boiling phenomenon will occur and the gas bubbles will form in the melt and float out of the melt. As a result, the final porosity will decrease. In addition, a higher superheat will simultaneously cause a non-uniform porous structure due to the pores coalescence and bubbling phenomenon. Finally, a theoretical model was developed to predict the critical superheat for the hydrogen to escape from the melt and the corresponding escapement ratio of hydrogen content. Considering the escapement of hydrogen, the predicted porosities are in good agreement with the experimental results.

商业文化智慧和美国电影

据统计数字表明,目前美国电影占世界各国公开放映总数的40%到90%.影院放映加上下游产值,美国电影产业的年产值在400亿美元以上.数字的罗列让我们反思美国电影为何能够成为独领风骚的庞大商业性艺术产业?面对这一问题,我们的探讨或许能够在入世的背景下为国产电影的萧条提供某种思维的启示.

Mechanical properties of anti-seepage grouting materials for heavy metal contaminated soil

Cement-based composite grouting materials were used to construct grouting cutoff wall for heavy metal contaminated soil in non-ferrous metal mining areas. Cement, fly ash, and slag as principal ingredients were mixed with water glass in different ways to produce three composite grouting materials. In order to investigate the effect of water glass mixing ratio, Baume degree, fly ash and slag contents on the mechanical properties of the composite grouting materials, particularly their gel time and compressive strength, the beaker-to-beaker method of gel time test and unconfined compressive strength test were conducted. In addition, the phase composition and microstructure of the composite grouting materials were analyzed by the X-ray diffraction（XRD） and scanning electron microscope（SEM） techniques. The test results show that their gel time increases when water glass mixing ratio and Baume degree increase. The gel time increases dramatically when fly ash is added, but decreases slightly if fly ash is partly replaced by slag. When the mixing ratio of water glass is below 20%, their compressive strength increases with the increases of the ratio; when the ratio is above 20%, it significantly decreases. The compressive strength also tends to increase as Baume degree increases, and improves if fly ash and slag are added.

Degradation of bond between steel bar and freeze-thaw concrete after electrochemical chloride extraction

The effect of electrochemical chloride extraction （ECE） on bond strength between steel bar and freeze-thaw concrete contaminated by chloride was experimentally investigated for beam specimens with dimensions of 100 mm × 100 mm × 400 ram. During the experiment, 3% NaC1 （vs mass of cement, mass fraction） was mixed into concrete to simulate chloride contamination, and the specimens experienced 0, 25, 50, 75 freeze-thaw cycles before ECE. In the process of ECE, different current densities and durations were adopted. It is indicated that the bond strength between reinforcement and concrete decreases with the increase of freeze-thaw cycles; the more the current and the electric quantity of ECE are, the more the loss of bond strength is; and the largest loss is up to 58.7%. So, it is important to choose proper parameters of ECE for the reinforced concrete structures contaminated by chloride and subjected to freeze-thaw cycles.

Analysis and behaviour of FRP-confined short concrete columns subjected to eccentric loading

Fibre-reinforced polymer (FRP) composites were widely utilized in civil engineering structures as the retrofit of reinforced concrete (RC) columns. To design FRP jackets safely and economically, the behaviour of such columns should be predicted first. This paper is concerned with the analysis and behaviour of FRP-confined RC circular and rectangular short col- umns subjected to eccentric loading. A simple design-oriented stress-strain model for FRP-confined concrete in a section analysis was first proposed. The accuracy was then proved by two test data. Following that, a parametric study including amount of FRP confinement, FRP strain capacity, unconfined concrete strength and shape of column section is provided. Some conclusions were obtained at the end of the paper. The work here will provide a comprehensive understanding of the behaviour of FRP-confined concrete columns. The simplicity of the model also enables a simple equivalent stress block to be developed for direct use in practical design.

The Effect of Steel Corrosion on Bond Strength in Concrete Structures

The effect of steel corrosion on the behavior of bond between steel and the surrounding concrete was investigated. Pullout tests were carried out to demonstrate bond stress-slip response for reinforcing steel bars of a series of corrosion level. Specimens either confined or unconfined were investigated for evaluation of the effect of confinement on bond strength and failure mode. Also, the tests were analyzed using nonlinear finite element analysis. It was shown that for both confined and unconfined steel bars, bond strength generally decreases as the corrosion level increases when corrosion level is relatively high. Confinement was demonstrated to provide excellent means to conteract bond loss for corroded reinforcing steel bars. It was shown that unconfined specimens generally split at a small slip with a large crack width and result in splitting failure while confined specimens contribute to a small crack width and generally cause a pullout failure. The analysis results agree reasonably well with the experiments.

Effect of condensation latent heat release on the relative vorticity tendency in extratropical cyclones:a case study

Taking an extratropical cyclone that produced extreme precipitation as the research object,this paper calculates the contribution of condensation latent heat release(LHR)to relative vorticity tendency based on the complete-form vertical vorticity tendency equation.The results show that the heating rate of convectional condensation LHR can reach up to about 40 times that of stable condensation LHR.Both the stable and convectional heating centers are higher than 700 hPa,which would cause∂Q/∂z>0 and a positive vorticity source in the lower troposphere.The vertical gradient of stable condensation LHR contributes little to the growth of relative vorticity,while the relative vorticity tendency associated with the vertical gradient of convectional condensation LHR can be an order of magnitude higher than the former.The positive vorticity source is always located right below the latent heating center,and its maximum value can always be found in the lower troposphere.Convectional LHR is the primary factor for cyclone development from the perspective of diabatic heating.The horizontal gradient of total condensation LHR can contribute about 65%of the actual vorticity growth,but the effect of the vertical gradient of convectional condensation(LHR)can reach twice as much.The adiabatic heating from LHR can cause vorticity tendency directly.However,it can also change the vertical and horizontal gradient of potential temperature,which can further induce vorticity tendency.

Effect of ultrasonic power and casting speed on solidification structure of 7050 aluminum alloy ingot in ultrasonic field

With the experiment and finite element simulation, the influences of power ultrasonic on the solidification structure of 7050 aluminum alloy ingot in semi-continuous casting were researched, and the effects of casting speed on solidification structure in ultrasonic field were also analyzed. The experiment and simulation results show that the solidification structure of the ingot is homogeneously distributed, and its grain size is obviously refined at ultrasonic power of 240 W. The average grain sizes, which can be seen from the Leica microscope, are less than 100 μm. When the casting speed is 45-50 mm/min, the best grain refinement is obtained.

Characterizing properties of magnesium oxychloride cement concrete pavement

The performance of magnesium oxychloride cement concrete(MOCC)in road engineering in the arid region in northwest China was investigated over a two-year period.Two categories of MOCC pavement,light-burnt magnesia concrete road(Road-L)and dolomite concrete road(Road-D),were prepared with light-burnt magnesia and a mixture of light-burnt magnesia and caustic dolomite(1:3 by mass),respectively.Variations in the properties of the MOCC pavement,such as compressive and flexural strength,mineralogical phase,and microstructure,after being exposed to two rainy seasons in the field were monitored.The compressive strength of the cored samples were conducted after being aged for 28 d,and the compressive and flexural strength were tested at ages of 1,2,3,28,90,180,270,360 and 720 d.The mineralogical phase and microstructure of the pavement were also analyzed by X-ray diffraction(XRD)and scanning electron microscopy(SEM).The results demonstrate that MOCC pavement obtained desirable compressive and flexural strengths after curing for 3 d for Road-L and 28 d for Road-D.Both of the compressive and flexural strength of Road-L and Road-D decreased slightly after experiencing two rainy seasons,with the major hydration products being 5Mg(OH)2 MgCl28H2O(Phase 5)and 3Mg(OH)2 MgCl28H2O(Phase 3).The decomposition of Phase 5 is mainly responsible for reducing the mechanical strength of the MOCC pavement.

Experimental research on bond strength of deformed GFRP rebars with different surface configurations

Based on the Canadian Standards Association(CSA) criterion,experiments on 30 pull-out specimens were conducted to study the bond strength of deformed GFRP rebars with 8 different surface configurations.Each rebar was embedded in a 150 mm concrete cube,and the test embedded length was four times of the rebar diameter.Relationship between the mode of failure,the average bond strength and the average bond strength-slip for each rebar was analyzed.Results show that the failure mode of all specimens is the shearing off or desquamation of ribs,no splitting cracks appear on the cube specimens.The bond stress of deformed GFRP rebars mainly depends on the mechanical interaction between the ribs of the bar and the surrounding concrete,and the bond strength of deformed GFRP rebars is improved obviously.The optimal rib spacing is less than 2.5 times of the rebar diameter,and the rib height is more than 3% of the rebar diameter.

基于舞蹈美学中的视觉多维表现研究——以胡沈员《遇见》为例

舞台美术是戏剧和其他舞台演出的一个重要组成部分,包括布景、灯光、化妆、服装、效果、道具等,它们的综合设计称为舞台设计。其任务是根据剧本的内容和演出要求,在统一的艺术构思中运用多种造型艺术手段,创造出剧中环境和角色的外部形象,渲染舞台气氛。《舞蹈风暴》作为一档近两年出现的深受大众欢迎的电视节目,以舞蹈表演为主要表现形式,以全新的、多角度的舞台媒体技术、舞台机械装置以及舞台道具等为舞美设计的主要设备,将"声、光、电、影"与舞蹈完美融合,成为舞蹈动作语汇在时间和空间上表达的延伸,增强了舞台作品张力,细化舞蹈演员情感。本文将以胡沈员在《舞蹈风暴》第一季中的作品《遇见》为例,分别从灯光、道具及360环绕投影三个方面解读并分析舞蹈语汇的二次表达与延伸,从而探究舞台设计与舞蹈形象、氛围、情感表达等方面的关系。

Behavior of concrete and concrete-filled circular steel tubular stub columns at constant high temperatures

Based on reanalyzing test results of uniaxial compressive behavior of concrete at constant high temperatures in China, with the compressive cube strength of concrete from 20 to 80 MPa, unified formulas for uniaxial compressive strength, elastic modulus, strain at peak uniaxial compression and mathematical expression for unaxial compressive stress-strain relations for the concrete at constant high temperatures were studied. Furthermore, the axial stress-axial strain relations between laterally confined concrete under axial compression and multiaxial stress-strain relations for steel at constant high temperatures were studied. Finally, based on continuum mechanics, the mechanics model for concentric cylinders of circular steel tube with concrete core of entire section loaded at constant high temperatures was established. Applying elasto-plastic analysis method, a FORTRAN program was developed, and the concrete-filled circular steel tubular （CFST） stub colunms at constant high temperatures were analyzed. The analysis results are in agreement with the experiment ones from references.

Weathering and soils formation on different parent materials in Golestan Province,Northern Iran

Geochemical, mineralogical, and micromorphologieal characteristics of soils and their relevant parent rocks including loess, ignimbrite, sandstone and limestone were investigated to identify the soil-parent material uniformity and the weathering degree of soils in Golestan Province, northern Iran. Highly developed Caleixerolls and moderately developed Haploxerepts were formed on loess and limestone, respectively. In contrast, the soils formed on ignimbrite and sandstone were non- developed Entisols. Illite was the dominant clay mineral found in ignimbrite and sandstone in both the A horizon and parent material. In loess derived soils however, smectite was dominant especially in the Bt horizon compared to its parent material indicating partly to its pedogenic formation. In limestone, illite and vermiculite were dominant both in the A and C horizons. Ti/Zr ratio proved that the studied soils were closely related to their underlying parent materials geochemically. Chemical index of alteration （CIA）, micromorphological index of soil development （MISECA）, smectite/illite＋chlorite ratio and magnetic susceptibility were applied to investigate the degree of soil development. Results showed that the most and the least developed soils were those formed on loess deposits and limestone,respectively. Application of the different geochemical and pedogenetic approaches was proved to be useful in identifying the relevance of soils to their underlying parent materials and also their degree of development.

Bond Strength of Bamboo Reinforcement in Light Weight Concrete

Bamboo reinforced concrete as a building material is expected to be an alternative to steel reinforced concrete. Due to the fact that steel is not renewable and polluting steel mills are fairly high. The bond strength is a major concern for the natural fiber used as reinforcement in structural composites. This paper reports study on the bond strength of bamboo reinforcement in concrete, to determine the adhesion reinforcement in concrete often do by the pull-out test. The research objective was bond strength of lightweight concrete and bamboo reinforcement. The test used light weight concrete with foam additives klerak. Bamboo slats were coated with paint and sprinkled with sand. The results obtained showed that the bond strength bamboo 60% of the bond strength steel.