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Hold down spring(HDS), clamped between the upper support plate flange and the core barrel flange inside a pressurized reactor vessel, is used to provide a downward force to keep the core barrel stable and from being lifted off from the vessel ledge during reactor normal operation. Spring designer used to think under certain extreme operating conditions, the spring could be lifted off from the ledge because the spring is not stiff enough to prevent the “lift-off”. Therefore, the spring was designed as stiff as it practically can be. However, finite element study indicated that the magnitude of preload is a strong function of friction coefficient. To find the magnitude of the friction coefficient, a series of tests were conducted on 1/10 scale hold down spring samples of three different spring designs. From the test results, it was found that the friction coefficient increases rapidly as the number of loading cycles increases. This implies that the spring preload would increase rapidly during plant operation. Therefore, it is concluded that, because of the strong frictional effect, not only the current design is more than adequate, but also should be made even softer.

This paper puts forward the concept of incentive utility, which converts the value of each attribute in multi-attribute decision-making into a unified index for measurement, thus simplifying multi-attribute decision-making. In this paper, a comprehensive evaluation model based on the TOPSIS of incentive utility is established. Through the establishment of incentive index, the utility of incentive and the calculation of ideal point of utility, the disadvantage of "ideal point is not ideal" in the TOPSIS is overcome. It can better synthesize the sub-attribute value and realize the subjective multi-attribute decision-making. The example shows that the model can apply subjective factors to decision-making scientifically, and the result is more reasonable and effective.

With the development of society, and the sharp increase in car sales, traffic accidents have become increasingly frequent and serious .At the same time, with the rapid development of science and technology, automotive technology has also been rapidly improved, automotive safety technology gradually involved in all aspects of the car. This paper introduces the main automotive safety technology at present, proposes a kind of airbag system, and describes its specific working methods.

With urban high buildings increasing in China, the demand for efficiency of wall insulation is getting more and more serious, especially in northeast and northwest China. However, thermal insulation wall in domestic is quite easy to produce cracks under external conditions, which greatly reduces life time. In this paper, we expand the discarded glass and mix aggregate and polypropylene fiber to improve the compressive strength of concrete to achieve green multifunctional concrete.Through the performance test of the expansive glass, we conclude that performances of expansive glass become best at the sinter point of 660°;Moreover, TiO2 added to the exterior wall coating can catalyze the degradation of nitrogen oxides and formaldehyde to purify the air. Non-toxic and harmless, the wall, with strong thermal insulation efficiency, is expected to replace the current building materials in order to produce and utilize massively.