BRE’s Microscopy unit have been extensively involved in the identification of new and unusual occurrences of the thaumasite form of sulfate attack (TSA) and thaumasite formation (TF). Using both optical and scanning electron microscopy a substantial database of information describing the location, form, composition and characteristics of TSA and TF in a series of different examples both within the UK and abroad has been developed. This paper describes the form taken by the TSA/TF within these various localities, and compares it with the characteristic taken by naturally occurring thaumasite.
Earlier work on the M5 concrete bridges in Gloucestershire, UK defined a four-stage degradation process, resulting in the formation of at least three microscopically distinct forms of thaumasite. This paper takes these basic stages and assesses their presence and makes some revisions to the characteristics of the TSA reaction, and its evolution within lower quality cement-derived materials, such as mortars and masonry. Finally the observed strong association of TSA and TF, with the “Popcorn” calcite form of deposition within more depleted areas of affected cement paste from degraded concrete-based material is also discussed along with a proposed mechanism of deterioration. 相似文献
Integrating engineering software is meaningful but challenging for a system code of a fusion device.This issue is seldom considered by system codes currently.Therefore,to discuss the issue,the Integrated Design System of TF Coil(IDS-TFC) has been worked out,which consists of physical calculation,CAD,and Finite Element Analysis(FEA).Furthermore,an Integrated and Automatically Optimized Method(IAOM) has been created to address the integration and interfaces.The method utilizes a geometry parameter to connect each design submodule and achieve automatic optimization.Double-objectives optimization has been realized,confirming it is feasible to integrate and optimize engineering design and physical calculation.Moreover,IDSTFC can also serve as a useful reference of integrated design processing for subsequent fusion design. 相似文献
The radial stainless steel plates (RPs) used for Toroidal field (TF) coils in the International Thermonuclear Experimental Reactor (ITER) are 13 m long, 9 m wide and 10 cm thick, which are quite large. Even though they are very large structures, high manufacturing tolerances and high mechanical strength at 4 K are required. It is also required that each RP should be fabricated every three weeks. Therefore, the authors intend to develop efficient manufacturing methods for an ITER TF coil RP. Laser welding is then selected as a welding method for RP. Especially, the development of high technology laser welding is necessary to prevent hot cracking in the material used for the RP; namely, fully austenitic stainless steel with high nitrogen content. The authors carried out trial laser welding experiments aiming at its application to RP. As a result, it was effective to make the angle of back inclination of the weld head at a uniform welding speed. It also seemed that the sensitivity of hot cracking could be reduced by optimizing the chemical compositions of material used for RP. The base material and the welded joints satisfied mechanical properties in 4 K. The application of the laser welding technology to the fully austenitic stainless steel was therefore demonstrated. 相似文献
Based on the optimal control theory, a 3-dimensionnal direct generation algorithm is proposed for antiground low altitude penetration tasks under complex terrain. By optimizing the terrain following(TF) objective function, terrain coordinate system, missile dynamic model and control vector, the TF issue is turning into the improved optimal control problem whose mathmatical model is simple and need not solve the second order terraind erivative. Simulation results prove that this method is reasonable and feasible. The TF precision is in the scope from 0.3 m to 3.0 m, and the planning time is less than 30 min. This method have the strongpionts such as rapidness, precision and has great application value. 相似文献
In contrast to the earlier experiments conducted in other machines,here,in SST-1 the error field measurement experiment is performed with a filled gas pressure ~8×10~(-4) mbar which helped to create a luminescent toroidal beam of electron path originated due to impact excitation and guided by the toroidal magnetic field.Beam path deviations are observed and recorded from radial and top ports using visible range cameras.Such creation and detection of the electron beam path differs from the earlier works where the gun emitted electron beam deviation in ultrahigh vacuum was detected on a collector-grid/fluorescent screen.In the present experiment,large beam deviations were observed.Later investigation of the experimental set-up reveals existence of a possible source of radial electric field in between the source and the vacuum vessel which are separately grounded.Thus,to understand the observed phenomena,experiments are numerically modeled with deviated TF coil set,PF coil set and the electron source location.A particle tracing code is used to follow the electron path in the magnetic field generated by the coil set of interest.Simulation results suggest that the large deviation corresponds to the E×B drifts and not due to the large field errors.Toroidally averaged field errors of the SST-1 TF coils at toroidal field of B_0=15 kG are negligibly small~B_0×10~(-6) or less,which should not adversely affect the plasma performance. 相似文献