Abstract: According to requirements of the mechanical property, durability quality, working performance for patching materials for bridge and tunnel, the new patching material named high-performance tensile composite mortar (HTCM) has been developed. The HTCM is a product of cement-based mortar modified by polymer. The strength test, shrinkage test, chloride resistance test, carbonization resistance test and working performance test for HTCM are introduced in this paper. According to the test results, the components, characteristics, performance and operational principle of HTCM are listed in this paper. At last, the technical characteristics and advantages for HTCM are also discussed in terms of construction feasibility based on construction technology of sprayed mortar. It has been found that the HTCM can be used as an effective patching material for bridge and tunnel.
Abstract: Dynamic impact experiments of man-made rock were carried out with the Split Hopkinson Pressure Bar (SHPB) apparatus in this paper. The impact process was analyzed and the influence of rock porosity on dynamic mechanical behavior was investigated. The stress-strain curves in rock were obtained by the one-dimensional stress wave theory. The curve lays foundation for numeric simulation of rock fracture under impact loading. The damage profiles of rock specimen under the impact loading show that the man-made rock exhibits obvious shear damage under the impact loading because it is a typical porous medium containing large quantities of defects such as pores, cracks and grain boundaries at the microscale. The experimental results also indicated that rock porosity plays an important role in dynamic mechanical behavior.
Abstract: The resources are divided into curable and non-curable morphologies to improve the efficiency of virtual computing systems, and we determine the quantities of such two morphologies based on resources required and resources that system owes. In the environment of tasks presenting random distribution, we describe the trend of resources required and compute the range interval of curable morphology by theoretical analysis. It is concluded that the amounts of tasks have great effect on resources required and the experiments show that the trend of decision variables in our numerical example is consistent with the theory discussed. The decision making methodology presented in this paper has some significance to the management of resources in virtual computing systems.
Abstract: In this paper, KBE and some key technologies, such as knowledge representation, knowledge reasoning and knowledge base design, are studied for solving the exiting design problems of modular machine tool fixtures. The methods of hybrid knowledge representation based on ontology and rule-based and case-based hybrid reasoning are introduced to intelligent design of modular machine tool fixtures. By researching the design flow of modular machine tool fixtures, a modular machine tool fixtures intelligent design system (MMTFIDS) is developed based on secondary development technology of UG/NX in the VS.NET integrated development environment. The system realizes the reuse of design knowledge and rapid design for modular machine tool fixture.
Abstract: As a naturally occurring fibrous mineral abundant in China, it is not common to use the brucite fiber as the reinforcement in asphalt concrete to improve its anti-cracking property in low temperature until now. Laboratory experiments are made on the brucite fiber asphalt binder and the brucite fiber asphalt concrete in this paper. Effects of the dosage of the brucite fiber on anti-crack properties of asphalt binder and brucite fiber asphalt concrete in low temperature are also studied. The contrast test is made between brucite fiber, lignin fiber and basalt fiber. Test results show that the value of the ductility, the compliance in extension and the yield strain energy of asphalt binder decreases with the increasement of the dosage of brucite fiber. However, the temperature sensitivity property of asphalt binder in low temperature can be improved. The anti-crack properties especially the maximum bending stress and the maximum bending strain are improved by adding the proper quantity of brucite fiber in asphalt concrete. According to the test results, the optimum quantity of brucite fiber was about 0.4 wt.% of asphalt. Based on the contrast test, the brucite fiber is better than the lignin fiber on improving the anti-crack properties of the asphalt concrete, but which is similar to the basalt fiber.
Abstract: Crystalline WO3 nanorods of less than 100 nm in diameter have been successfully synthesized at 240 °C for 72.0 h with pH=1.5 in the system of strong acid with sodium tungstate and potassium sulphate by the hydrothernal method. The morphologies and structures of WO3 rods have been characterized and analyzed by XRD, SEM, TEM and SAED. SEM confirmed that the slenderness ratio of WO3 rods was enlarged with the increase of t the pH value and the reaction time. SAED analysis showed that the crystal morphology of the synthesiezed WO3 nanorods was crystallin. UV-VIS results showed that the absorbent power of UV light for WO3 nanorods enhanced with the increase of their slenderness ratio.
Abstract: The pyrolysates of NiC2O4. 2H2O in the air were investigated by TG-DSC, SEM and TEM. The results showed that there are two stages in the process of the pyrolytic decomposition of NiC2O4. 2H2O in the air. The crystal water in NiC2O4. 2H2O was lost from 175 °C to 275 °C. NiC2O4 was pyrolysized into NiO from 325 °C to 400 °C. In the process of the pyrolytic decomposition of NiC2O4. 2H2O, the influence on the pattern of the decomposition was more from 246.5 °C to 357.8 °C. The influence on the pattern of the decomposition was less from 357.8 °C to 400.0 °C. Therefore, the pyrolytic condition of NiC2O4. 2H2O in the air was controlled if the effective pattern of NiO powder was obtained. At the same time, spherical NiO of about 5 nm is obtianed through the pyrolytic decomposition of NiC2O4. 2H2O at 400 °C for 10 min at the rate of 10 °C / min.
Abstract: The examination of outer cylinder of pipes in steam generators is difficult to fulfill due to confined space. A robotic system has been developed to do the job. The robot contains a base, four rotary balls, a slide guide, two steppers, a DC motor, a positioning mechanism, a synchromesh belt mechanism, a longitudinal mobile platform, an extending and retracting mechanism, a rotary platform and a micro vehicle. The positioning mechanism can locate and fix the robot efficiently. The motion of the robot consists of longitudinal motion and transverse motion. The extending and retracting mechanism can push and pull the micro vehicle carrying a micro CMOS camera. The pose of the camera mounted on the movable platform of a micro 3-CSR parallel mechanism can be adjusted by 3 bias-two-way SMA actuators. The control system consists of two levels of computers. The user interface was developed with VB. Fuzzy control method is utilized to control the motion of the longitudinal mobile platform. Grey evaluation method is applied to evaluate the status of checked areas according to obtained images. Experiment results indicate that the robot has met the needs of examination.
Abstract: The phase-field model coupled with a flow field was used to simulate the dendrite growth in the undercooled pure metal melt. The effects of flow velocity, supercooling and anisotropy on the dendritic growth were studied. Results indicate that melt flow can enhance the emergence of side-branches, the morphology of the dendrite was composed of the principal branches and side-branches. With an increase in flow velocity and supercooling, the velocity of upstream dendritic tip increases, but the tip radius decreases first and then increases. With an increase in anisotropy values, the velocity of upstream dendritic tip increases and the tip radius decreases. The results of calculation agreed with LMK theory in the case of low flow velocity and anisotropy.