We introduce a compact atomic clock based on laser-cooled atoms trapped inside a loop-gap microwave cavity. The cavity occupies a volume eight times smaller than conventional cylindrical cavities while maintaining a high quality factor in the presence of the ten apertures required for optical manipulation of cold atoms. The measured linewidth of the Ramsey spectrum, which is limited by the free fall distance of the atomic cloud in the cavity, was 19.6 Hz. The corresponding frequency instability was σy(τ) = 2.5 × 10−12 τ−1/2, which could be further improved by reducing the local oscillator noise. This work paves a way toward high-performance portable atomic clocks.
In November 2013, a case of sustained combustion of a female body was encountered in a Korean farming village. The body was almost completely incinerated from the neck to the knees, and other parts of the body, such as the head, arms, lower legs, and feet, were slightly damaged. The most likely external ignition source was the flame from a matchstick. The elderly woman was found incinerated on the floor of the living room, while other objects in the house were largely undamaged except for having a brown oily or greasy coating. Flammable substances were not detected from the woman’s intact pieces of clothing and socks, and her muscular tissues did not contain toxic chemicals. The concentration of carboxyhemoglobin in her peripheral blood was 11% and that of ethyl alcohol in her aqueous humor was below 0.010%. An autopsy failed to determine the exact cause of death because of excessive charring.
In this study , short -circuit processes were analyzed via simulations and experiments by applying a principle that can interpret the short-circuit marks, which are the most basic inspection criteria in fire-scene investigation. According to Fleming's left-hand rule, a Lorentz force is generated when current and magnetic fields are applied. Railgun, one of the typical applications, utilizes the same basic principle for generating trajectories. Using the same concept, it was interpreted that the molten copper balls generated during a short-circuit process scatter in the load direction similar to a ballistic launch. The simulation and experimental results also confirmed that the copper balls were scattered in the load direction owing to the Lorentz force. Although it is impossible to examine the source and load during a fire-scene investigation process, the study findings will aid in predicting the load by observing the portion where the copper bulbs are relatively frequent. Thus, based on an estimation of the cause of fire, it will be possible to infer reliable results through fire-scene investigation.
We found metallic migration phenomena at the fire scene in Printed circuit board (PCB) of LED light equipment which are commonly used. Accordingly we did this study. In order to generate rapidly metallic migration, we experiment the water drop test under low voltage (3.0 V) and a small amount of water condition. As a results of our experiment, we saw the growth of metallic migration of Copper and checked directly short of the PCB between isolated two poles by Cu migration. Finally we saw the shape of dendrite pattern by Cu migration using Scanning electron microscope (SEM) and analyzed that components via Energy dispersive Spectrometer (EDS).
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