14 research outputs found
The three dimensional distribution of chromium and nickel alloy welding fumes.
In the present study, the fumes generated from manual metal arc (MMA) and submerged metal arc (SMA) welding of low temperature service steel, and the chromium and nickel percentages in these fumes, were measured at various horizontal distances and vertical heights from the arc in order to obtain a three dimensional distribution. The MMA welding fume concentrations were significantly higher than the SMA welding fume concentrations. The highest fume concentration on the horizontal was shown in the fumes collected directly above the arc. The fume concentration vertically was highest at 50 cm height and reduced by half at 150 cm height. The fume concentration at 250 cm height was scarcely different from that at 150 cm height. The distribution of the chromium concentration vertically was analogous to the fume concentration, and a statistically significant difference in the chromium percentages was not found at the different heights. The nickel concentrations were not statistically significant within the welding processes, but the nickel percentages in the SMA welding fumes were statistically higher than in the MMA welding fumes. The highest nickel concentration on the horizontal was found in the fumes collected directly above the arc. The highest nickel concentration vertically showed in the fume samples collected at 50 cm height, but the greater the height the larger the nickel percentage in the fumes.</p
Experimental transmission of quantum digital signatures over 90-km of installed optical fiber using a differential phase shift quantum key distribution system
Quantum digital signatures apply quantum mechanics to the problem of
guaranteeing message integrity and non-repudiation with information-theoretical
security, which are complementary to the confidentiality realized by quantum
key distribution. Previous experimental demonstrations have been limited to
transmission distances of less than 5-km of optical fiber in a laboratory
setting. Here we report the first demonstration of quantum digital signatures
over installed optical fiber as well as the longest transmission link reported
to date. This demonstration used a 90-km long differential phase shift quantum
key distribution system to achieve approximately one signed bit per second - an
increase in the signature generation rate of several orders of magnitude over
previous optical fiber demonstrations
Experimental demonstration of quantum digital signatures over 43 dB channel loss using differential phase shift quantum key distribution
AbstractEnsuring the integrity and transferability of digital messages is an important challenge in modern communications. Although purely mathematical approaches exist, they usually rely on the computational complexity of certain functions, in which case there is no guarantee of long-term security. Alternatively, quantum digital signatures offer security guaranteed by the physical laws of quantum mechanics. Prior experimental demonstrations of quantum digital signatures in optical fiber have typically been limited to operation over short distances and/or operated in a laboratory environment. Here we report the experimental transmission of quantum digital signatures over channel losses of up to 42.8 ± 1.2 dB in a link comprised of 90 km of installed fiber with additional optical attenuation introduced to simulate longer distances. The channel loss of 42.8 ± 1.2 dB corresponds to an equivalent distance of 134.2 ± 3.8 km and this represents the longest effective distance and highest channel loss that quantum digital signatures have been shown to operate over to date. Our theoretical model indicates that this represents close to the maximum possible channel attenuation for this quantum digital signature protocol, defined as the loss for which the signal rate is comparable to the dark count rate of the detectors.</jats:p
Dataset for Experimental transmission of quantum digital signatures over 90-km of installed optical fiber using a differential phase shift quantum key distribution system
This dataset is a CSV file the allows Figure 3 of the aper to be recreate