Research on Force and Thermal Phenomena of Short Circuited Melted Mark in Electrical Fire
This paper mainly does a research on force and thermal phenomena of short circuited melted mark in electrical fire. The primary short circuited melted mark and secondary short circuited melted mark were prepared by the experiment, and were characterized by metallographic microscope, powder X-ray diffraction, scanning electron microscope and energy dispersive spectroscopy, the role of forces and heat in short circuited melted mark in electrical fire were demonstrated and investigated. It is found that they show a similar shape that the melted ball close to one side for anode melted marks, and their particles show the specific and uniform direction and the most particle size of anode melted marks are larger than the particle size of cathode melted marks, both below the copper wire grain size 64.2nm, similarly, it can be clearly seen that the ratio of O: Cu in deposit layer of all melted marks are below 0.5. Finally, these above special phenomena gave short circuited melted mark the primary statement from the theoretical point of view.
Quantitative analysis of metallographic structure parameters of the melting trace caused by the first short circuit
The authentication and judgment of fire first short circuited melted mark in electrical is vital for fire reasons and accident analysis,and the metallographic analysis method is currently in experience or semi-empirical level,without quantitative analysis method.The short-circuit simulation experiments of copper wires in different current conditions(from 100A to 300A,interval of about 20A) were conducted in this paper,and the metallographic pictures of short circuited melted mark were made in the experiments.The microstructure characteristic parameters of the metallographic patterns were introduced and discussed through digital image processing techniques based on Image-Pro plus software,and the microstructure characteristic parameters of the metallographic patterns contained grain size and hole dimensions of the metallographic structure.At last,the data contrast of the relationship between metallographic microstructure characteristic parameters and the current was realized,the quantitative analysis criterion and changing law of the metallographic organization in primary short circuited melted mark were explored.
The Vascular Theory of Migraine‐Resuscitated or More Moribund?
Your decision to publish an important paper on cerebral blood flow (CBF) in migraine1 as the first in Headache for 1989 is to be applauded. But does it clarify or cloud the issue? After 20 years of CBF studies in migraine the results show 1) a reduction of at least 25 30% in classical migraine1, 2) an average increase of 31% in common and classical migraine2, 3) or no change in common migraine3. Now we learn that the measurements need modifying by 40% to allow for scattering of radiation the Compton scatter effect which has led to "an unbalanced interpretation of the data"1 So the results are as contradictory as they can be, the measurements require adjustment, and the interpretation is therefore doubly doubtful. From the clinical point of view the neurological aura, the enlarging scotoma, the scintillations, the migration of the paraesthesiae up the arm or visual disturbances across the visual field, have not been seen in cerebrovascular disease.4 The headache is throbbing in only 47% of 750 patients questioned during a migraine5; but even when the pain is pulsatlie, it throbs for only a portion of the time at the maximum of the headache (Blau unpublished observations). The evidence for a neurological aetiology has been examined6: the most potent argument against a vascular cause is that the common triggers stress, light and hunger go direct to the nervous system, not via blood vessels. No one denies that vascular changes occur in migraine but are they primary or secondary to a neurological disturbance? Sokoloff7 concluded that the stimulated rat and monkey cortex showed increased glucose uptake, and that the increased local blood flow occurred "in response (my italics) to changes in local functional activity". The evidence, therefore, points to an underlying neurological basis with secondary vascular responses. The vascular theory may need resuscitation but who is going to give it the kiss of life?