Amidation of amino acids using dichloro(methyl)(3,3,3-trifluoropropyl)silane (MTFPSCl2) and imidazole is described. MTFPSCl2 activates the carboxy group and protects the α-amino group of amino acids. The amidation proceeded with 19 amino acids and 19 amines, including α-branched amines and anilines; the corresponding amino acid amides were synthesized in good-to-high yields (up to 96%) with low-to-no racemization.
In this study, a three-dimensional electromagnetic thermal fluid simulation program was developed to simulate arc movement numerically while considering metal vapor generated from a molten metal bridge along with an electrode opening under external magnetic field application. The change in the physical properties of the arc and the increment rate of the arc voltage per unit length under different electrode opening velocities were analyzed by applying an external magnetic field with different intensities. It was found that the current path of the arc became dispersed when the electrode opening velocity was high because the metal vapor generated from the molten metal bridge remained dominant and highly concentrated. Before the completion of the electrode opening process, the difference in the increment rate of the arc voltage per unit length at different electrode opening velocities became more significant when an external magnetic field was applied. This was because under high and low electrode opening velocities, the cross-sectional area of the arc became narrow and broad, respectively.
As the mileage of the electric railway increases, the unevenness of the contact wire may separate the contact wire and the contact strip. Simultaneously, a disconnection arc discharge is generated by the molten metal bridge. This causes the contact wire to melt and evaporate causing it to break. A few studies have conducted experiments to prevent the contact wire from disconnecting. Based on the results thus obtained, they presented their hypotheses considering conditions sch as the current and time required for melting and evaporation of molten metal bridge and arc generation. In this study, a calculation method for the melting and disconnection phenomenon of the contact wire. Its mass increased when the currents from both sides of the contact wire were taken into consideration. Therefore, we obtained that the convection and radiation play an improtant role for calculation of the melting amount mass of contact wire.
Numerical simulations are commonly used to elucidate the arc phenomenon in electrical railways and analyze its physical property variations. However, the initial conditions of the molten metal bridge must be set to accurately mimic the arc phenomenon. Therefore, the radius and length of the molten metal bridge are experimentally measured immediately before arc generation for four different contact strip materials as the cathode and copper contact wire as the anode. It found that the radius and length of molten metal bridge both proportional to the current regardless of the contact strip material.
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