The Performance of Steel Corrosion of Damaged Concrete Structures with Different Repair Techniques

The reinforced concrete beams which have been bending damaged are repaired by the six kinds of repair materials and its related methods. Based on the linear polarization method, the corrosion situations of the steel bars in the repaired concrete structures were studied, which were immersed in 5% magnesium sulfate. The results show that: different repair materials and its related methods, significantly affect the steel corrosion performance of patched members. The repairing method, cement-based repair mortar with zinc wire connected with the bar, can most effectively improve anti-corrosion ability of reinforced concrete. There is an exponential relationship between the polarization resistance and corrosion current density, and the relationship formula between the polarization resistance and corrosion current density was put forward.     

佳县不同品种红枣抗裂性比较研究

为筛选出适合佳县地区种植的红枣抗裂品种,利用枣果浸泡试验,分析了‘佳县长枣’、‘狗头枣’、‘赞皇枣’、‘骏枣’、‘壶瓶枣’、‘金丝小枣’、‘圆铃枣’、‘晋枣’、‘灵宝枣’、‘木枣’10个佳县本地栽植的红枣品种裂果率和吸水率的变化趋势,比较不同品种的抗裂性。试验结果表明,在浸果过程中,红枣的裂果率在24 h内基本呈直线增加,72 h后达到稳定。不同红枣品种在脆熟期浸果后一定时期内(24~48 h)的裂果率和吸水率线性相关。不同品种之间的红枣裂果率差异显著,‘骏枣’裂果率最高,为93.3%,‘圆铃枣’裂果率最低,为26.7%,其次为‘佳县长枣’和‘灵宝枣’。因此,适合佳县栽植的较好红枣抗裂品种为‘圆铃枣’、‘佳县长枣’和‘灵宝枣’。     

Influence of Polypropylene Fiber on the Performance of Thermal Insulating Mortar Made from Expanded Polystyrene Particles

The influences of the types, dosage and length of fibers on EPS thermal insulating mortar were studied. The results show that the addition of fibers have obvious reinforcing effects on EPS thermal insulating mortar. With the addition of polypropylene fib     

玉米裂纹及其检测

我国粮食部门经过较长时间才认识到玉米裂纹的重要性。玉米裂纹是指人眼能观察到的玉米表面和胚乳内部裂缝宽度为0.1 mm左右的缝隙。玉米籽粒内部生来就有许多微裂纹,构成胚乳内众多的微毛细管。借助电子显微镜可以观察到纳米级的微毛细管。目前检测玉米裂纹的仪器需进一步改进。     

Calculation of Crack Space and Crack Width of Tunnel Lining Based on Elastic Foundation Curved Beam Model

Based on the elastic foundation beam,the control differential equation of tunnel lining is worked out,according to the theory of Saint-Venant,the predominance equation about the center angle to the crack space is established, then the crack space of tunnel lining under the loads can be worked out and according to the crack space,the crack width can be calculated.     

Chloride Transport in Splitting Cracked Concrete at Marine Tidal Zone

The chloride ion transport in concretes with different size of splitting cracks at marine tidal zone is investigated. The splitting crack widths of concrete are about 003 mm, 005 mm, 010 mm, 015 mm and 030 mm. The cracked concrete and sound concrete are placed at marine tidal zone for 30 d, and the chloride ion content in crack zone and perimeter zone of concrete, chloride ion penetration depth and steel bar corrosion area are quantitatively determined. It is shown that splitting crack will be recovered when the concrete is unloaded in split test. And the splitting crack width of concrete should be characterized by the value of displacement sensor when the concrete is unloaded in split test. The chloride ion content of cracked concrete decreases with increased depth, and then gets to remain steady from 10 mm to the inner. The relationship between chloride ion content and crack width in the steady zone can be regressed as the exponential function and the linear function for the crack zone and the perimeter zone of concrete, respectively. Due to away from the crack zone, the influence of splitting crack width on accelerated chloride ion ingression in the perimeter zone is less than that in the crack zone. When the splitting crack width is more than 005 mm, the chloride ion penetration depth in crack plane and in vertical crack plane of concrete is 50 mm and 20 mm, respectively. And the steel corrosion area enlarges with the increasing crack width. And the chloride diffusion coefficient of cracked concrete is closely related to the resistance capacity to chloride penetration of concrete, crack density (matrix width, crack width), and chloride binding capacity of concrete. When the crack density of concrete is less than 70, the chloride diffusion coefficient of cracked concrete increases with decreased crack density linearly. The chloride penetration will accelerate near the crack zone. And the raised splitting crack width will lead to its influence area in concrete increased quickly.     

Microcracking and Chloride Penetration of Concrete under Uniaxial Compression

A non-destructive method of evaluation of specific crack area was used to characterise microcracking in concrete prisms during uniaxial compression loading and unloading. Chloride profiles were also measured after the same concretes were exposed to chloride environment. The relation among microcracking, stress-strength ratio and chloride penetration of concrete were analysed based on the experimental results. Under compressive load, the apparent chloride diffusion coefficient decreases until about one third of the ultimate load. Further increase of compressive load improves the chloride diffusion coefficient again. There is a close link between microcracking and stress-strength ratio. The index of specific crack area can be used to indicate the microcracking and study chloride transport behaviour into concrete under the influence of microcracking.     

Experimental Analysis of Cracking Behavior of ConcreteBeams Reinforced with High Strength Bars

Eight concrete beams reinforced with 500MPa steel bars and four reinforced with 400MPa ultra fine grain steel bars were tested under two point symmetrical concentrated static loading to observe the details of crack pattern development on these beams and investigate their cracking characteristics. It was shown that the cracking behavior of the beams with high strength bars was essentially similar to that of common RC flexural members, whereas the computed crack widths using the formula adopted in the Code for Design of Concrete Structures GB 50010 2002 exceeded that of the experiment under the normal service. Furthermore, the formulas for crack spacing and crack width specified in GB 50010 2002 were evaluated through the experimental results and previous studies of sixty seven concrete beams reinforced with high strength bars. On the basis of the calculation model in GB 50010 2002, revised formulas for crack spacing and crack width were proposed. The values calculated by revised formulas were in good agreement with the test results.     

A STUDY OF PHOTO-ELASTIC EXPERIMENT TO FRACTURE PROCESS OF LIMESTONE SPECIMEN WITH PRE-CRACKS

In this paper, the fracture process of specimen with pre-cracks is studied by using photo-elastic expe' merit.The analysis results of cracks stress field show that because the inter-effection appears between the the two cracks and the tensile fracture occured when the tensile stress concentration reaches to a certain degree, and cracks link up with each other, macroscopic failure will gradually result. Positions of cracks will have different effections to speciment's fracture.     

Analysis of Damage Localization in Crack Weakened Rock Mass

Damage localization in crack weakened rock mass is closely related to the crack growth pattern. Bifurcation of the alternative evolution of cracks occurs when the cracks grow to some extent, then some cracks keep on growing while other ceased evolving. It is found that damage localization in crack weakened rock mass is caused by bifurcation of the crack growth pattern, and the initial location is also determined by the crack growth pattern. Based on the analysis on the bifurcation of crack growth pattern, the critical length of wing crack and the critical stress of damage localization in crack weakened rock mass are obtained. Subsequently, the onset location of damage localization is determined by using the eigenvalue and eigenvector of coefficient matrix, and crack interaction is also taken into account in this model. Finally, the relationship between the interval between columns and rows, the orientation of crack, confining stress and the critical stress of damage localization is defined in the example.     

THE THERMAL CRACK IN MASONRY STRUCTURE AND ITS CONTROL DESIGNING

The horizontal, vertical or oblique thermal cracks widely present in a masonry structure are summarized in this paper. The reasons for these cracks are analyzed.On basis of these causes, different methods called" readjusting", "releasing" and "resisting" for short, can be taken respectively in structure design to eliminate the cracks.     

CFRP筋钢筋混凝土剪力墙自复位性能试验研究

通过对1片钢筋混凝土剪力墙和4片配有碳纤维增强聚合物(CFRP)筋的剪力墙的低周反复荷载试验,在分析试验中测得的裂缝宽度、裂缝的发展和分布形态、侧向变形的基础上,研究了在钢筋混凝土剪力墙的适当位置部分或全部配置CFRP筋对剪力墙的残余裂缝和残余变形等自复位性能的影响规律。研究结果表明:与普通钢筋混凝土剪力墙相比,配有CFRP筋的剪力墙的开裂荷载较低,裂缝较多,裂缝分布分布范围较广,墙体的最大裂缝宽度、残余裂缝宽度和侧向残余变形分别降低了60%、70%和90%,说明在剪力墙中合理配置CFRP筋能使剪力墙具有优异的自复位性能。     

Analysis on temperature field of pulse current discharge in metal component with double semicircle immerged crack

The application of crack prevention techniques is badly needed in various industries. There are many practical applications, such as in space flight and aviation, shipping, military affairs and machine manufacturing. The current density distribution, temperature field distribution of flow around the crack tip and the heat affected of two cracks are derived theoretically in view of the pulse discharge in metal component with double semicircle immerged crack. A three-dimensional finite element model with semicircular embedding crack is established by finite element software ANSYS to analyze the temperature filed. The distribution law of temperature field is consistent with the results of theoretical calculations and numerical results, and the maximum temperature error and relative error are 75.560 ℃ and 3.150% respectively. By pulse discharge experiments, the crack tip melts and passivated after pulse discharge.     

速冻工艺对水饺冻痕率影响的研究

通过单因素和正交试验得出对速冻水饺冻痕率的影响因素次序依次为:深冻区温度>预冻区温度>预冻区风速>深冻区风速;最佳工艺条件为:预冻区温度-20℃,预冻区风速4m/s,深冻区温度-30℃,深冻区风速4m/s。     

Design of Linux password high speed crack model on FPGA

In order to improve the crack speed of linux password, the crack core design idea based on dataflow is proposed. After analyzing core crack module MD5 of linux, three crack models are designed, and their ALMs consumption and run speed are analyzed. Under the structure of full pipeline, based on the idea of dataflow, the Linux crack core is designed to crack linux password fast. Experimental results show that while cracking linux password on FPGA of EP4CE40F29C8, the speed can reach up to 24.95 million/s. In the framework of fully pipeline, the idea based on dataflow makes all the pipeline data blocks in efficient working condition. Linux password crack speed increases greatly.     

稻谷吸湿形成裂纹的初步研究

试验采用密闭容器中不同温度下饱和盐溶液上方相对湿度不同的原理， 三种含水量为１３．００％，１０．８０％和９．０７％的稻谷处在不同温度和相对湿度状态下，环境条件对稻谷吸湿形成裂纹的影响。     

我国主要储粮害虫抗性调查研究

通过对全国范围内23个省、市和自治区的55个地区粮库中的主要储粮害虫进行取样，用FAO抗性测定方法对92个虫样进行磷化氢抗性测定，得出无抗性虫样占调查虫样总数的54．3％、低抗性虫样占9．8％、中等抗性虫样占7．6％、高抗性虫样占13．0％、极高抗性虫样占15．2％。在调查的几种主要储粮害虫中，高抗性虫样主要为锈赤扁谷盗、谷蠹和米象，其中锈赤扁谷盗的抗性普遍比较严重，谷蠹和米象通过与1995年抗性调查所取的样品进行比较，在最近的8年内米象的抗性倍数增加了10．7％、谷蠹增加了71．2％。磷化氢抗性较高的区域主要是我国西南、华中和华南地区。     

Performance analysis of StimGun technology

With further exploration and development of oil and gas wells, it is found that the unconventional oil-gas bed occupies a major proportion in gas reserves. However, it is difficult to obtain satisfactory control by using conventional perforation technology because of its characteristics of low pore, low permeability and compact lithology in the unconventional oil-gas bed. The StimGun tech (synergize compound perforation) is described as following: after the perforating gun is fired, propellant burns with high-energy gas produced. Then the high-energy gas enters the perforating hole and forms multi-path cracks around perforated hole, which connects with the natural cracks and improves the permeability of oil and gas bed. The application and advantage of StimGun are introduced. The Stimgun is successfully applied in Sichuan LG oilfield. It can control the fracture heights effectively and remove contamination formation with no water producing, and it is also a great help to increase productivity of the oil-gas bed with low permeability.     

Influence of Construction Defect on the Performance of Lining in Hydraulic Tunnels

In the construction of hydraulic tunnel, the engineering quality problem is often caused by concrete cracks and insufficient thickness of roof lining. This problem attracted great attention of the most engineers that whether the structure performance of this kind of lining can meet the design criteria or not, especially under unfavorable conditions. Based on the on site inspections of the lining defects in Baishanzui tunnels, the model and size of the defects are analyzed with FLAC program. The study shows that the defects have obvious adverse influence on the stability and safety of the tunnel lining, however, if a backfilling grouting is carried out and the cracks are repaired, the integrality of lining is restored, the behavior of lining will be improved and can meet the design criteria as well.      

Durability of resistance against fungal, bacterial and viral pathogens; present situation

In evolutionary sense no resistance lasts forever. The durability of a resistance can be seen as a quantitative trait; resistances may range from not durable at all (ephemeral, or transient) to highly durable. Ephemeral resistance occurs against fungi and bacteria with a narrow host range, specialists. It is characterised by a hypersensitive reaction (HR), major gene inheritance and many resistance genes, which often occur in multiple allelic series and/or complex loci. These resistance genes (alleles) interact in a gene-for-gene way with a virulence genes (alleles) in the pathogen to give an incompatible reaction. The pathogen neutralises the effect of the resistance gene by a loss mutation in the corresponding avirulence allele. The incompatible reaction is not elicited any more and the pathogenicity is restored. The pathogens can afford the loss of many avirulences without loss of fitness. Durable resistance against specialised fungi and bacteria is often quantitative and based upon the additive effects of some to several genes, the resulting resistance being of another nature than the hypersensitive reaction. This quantitative resistance is present to nearly all pathogens at low to fair levels in most commercial cultivars. Durable resistance of a monogenic nature occurs too and is usually of a non-HR type. Resistance against fungi and bacteria with a wide host range, generalists, is usually quantitative and durable. Resistances against viruses are often fairly durable, even if these are based on monogenic, race-specific, HR resistances. The level of specialisation does not seem to be associated with the durability of resistance. This revised version was published online in August 2006 with corrections to the Cover Date.