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。     

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.     

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。     

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。     

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.      

Analysis and Treatment of the Quality Accident of Circle Beam in a Certain Big Wineshop

In this paper,through the analysis of the engineering quality accident of the top circle beam in a certain big wineshop,a mechanical model of the reinforced concrete circle beam is proposed.By calculation and analysis,the reason of cracking in the circle beam support was found out,and the correct calculated result was made out,so that the engineering quality accident was timety treated.     

Influence of Shrinkage Cracks on Chloride Penetration and Crabonation of Concrete

The influence of shrinkage crack on chloride ion penetration and carbonation of concrete is investigated. The concrete samples with shrinkage crack of 0.07 mm,0.1 mm,0.2 mm,0.4 mm and 0.62 mm are prepared, and both an accelerated carbonation test and Qingdao sea water corrosion test are conducted on sound concrete and cracked concretes. The depths of carbonation, the content of free chloride and total chloride in crack zone and perimeter zone of concrete are analyzed. The enperimental result shows that both free chloride and total chloride content in cracked concrete increase with the rise of the shrinkage crack width, and they are related in quadratic function. The chloride penetration velocity in crack zone is higher than that in perimeter zone of concrete. However, the increased specific surface in shrinkage crack tip improves chloride binding capacity and decreases the free chloride content in this zone. When the shrinkage crack is less than 0.07mm, the carbonation depth in crack zone is same as that of sound concrete. The chloride diffusion coefficient and the carbonation depth of cracked concrete increase limited as the shrinkage crack is less than 0.1mm, and then increase significantly with the increasing of shrinkage cracked width. Moreover, the carbonation depth in crack zone is increased by 3mm in comparison with that in perimeter zone of cracked concrete.     

THE STUDY OF STRAIN FATIGUE CRACK PROPAGATION BEHAVOURS OF VANADIUM BEARING HSLA STEEL

In this paper, the strain fatigue: crack propagation rates of vanadium bearing HSLA steel with different micro-structures are measured under constant load conditions, and the relationship between the crack propagation rate and the microstructures of steel is also studied.     

Auto Mesh Algorithm of the Finite Cover System in the Numerical Manifold Method

A auto mesh algorithm of the finite cover system is presented by abstracting the finite cover system of numerical manifold method as independent data classes.The programs are made by Object Oriented Programming(OOP).The accuracy manifold element can be generated automatically when the continuous material is cut by crack.The calculation result shows that the algorithm is reliable and effective.