The influence of the thermal condition steel on transformation temperatures two chromium hot-work tool steels was investigated. studied were in different states: soft -annealed state and hardened-and-tempered state. soft-annealed condition, i.e., fully annealed is a which matrix ferritic, carbon chemically bonded spherical carbides. other hand, means martensitic with uniformly distributed (prim...

due to the high price of virgin vegetable oils and the drawbacks of the homogeneous catalytic transesterification, in this work an economically profitable alternative process was proposed for biodiesel synthesis in which transesterification of the low-cost waste cooking oil (wco) with methanol in a heterogeneous system was done. alumina impregnated with sodium hydroxide was utilized as a solid ...

introduction: psychological and social health is the main problems of workers population, which can increase productivity at work and physical and mental health and provide or decline in these aspects. materials and methods: this study was descriptive and crosses - sectional and has been performed on 388 iranian central iron ore company workers. the tool of study was standard ghq-28 question ar...

the silica boron sulfuric acid nanoparticles (sbsans) as an efficient heterogeneous solid acid catalyst with both brønsted and lewis acidic sites catalyzed the preparation of bis-4-hydroxycoumarin derivatives using reaction of aldehydes and 4-hydroxycoumarin under mild and solvent-free condition at room temperature. this new and efficient methodology has advantages in comparison with currently ...