• Earthquakes and Structures
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• v.17 no.6
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• pp.591-598
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• 2019

The most recent shaking experiences have demonstrated that the predictions of the seismic models are not always in agreement with the registered responses, especially in the face of extreme earthquakes. Records collected from 1960 to 2011 at a rock-like site are used to develop a neural network that permits to estimate peak ground accelerations via the magnitude, the focal depth, the site-source distance and a seismogenic zone. The neural model is applied to the 8th and 19th September 2017 events that hit Mexican territory and the obtained results show that the network is flexible enough to work appropriately to various conditions of intensity and sites-sources with remarkably predictive capacity. The neural-attenuation curves are compared with those obtained from Ground Motion Prediction Equations and their performance is assessed for events, in addition to the devastating Mexican events, from Japan, Taiwan, Chile and USA.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4B
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• pp.422-428
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• 2011

In this paper, we introduce system and channel modeling for an underwater ad hoc acoustic network with n regularly located nodes， and then analyze capacity scaling laws based on the model. A narrow-band model is assumed where the carrier frequency is allowed to scale as a function of n. In the network, we characterize in attenuation parameter that depends on the frequency scaling as well as the transmission distance. A cut-set upper bound on the throughput scaling is then derived in extended networks having unit node density. Our result indicates that the upper bound is inversely proportional to the attenuation parameter, thus resulting in a power-limited network. Furthermore, we describe an achievable scheme based on the simple nearest-neighbor multi-hop (MH) transmission. It is shown under extended networks that the MH scheme is order-optimal for all the operating regimes expressed as functions of the attenuation parameter.

• Journal of Korean Society of Forest Science
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• v.90 no.1
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• pp.113-123
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• 2001

The main purpose of this study was to provide information on attenuation effects in forest tree belt of pine stand and oak stand. The relationships between DBH, tree height, clear length, crown area and number of trees and also between distance from noise origin, landslope etc. were analysed by correlation and multiple regression. The results obtained were as follows : 1. There was no difference between pine stand and oak stand in effecting noise attenuation. 2. The noise pressure was highly correlated with all of seven elements tested and both DBH and distance from noise origin have higher r-values than the others. For the pine stand, it was 0.9133 in DBH and 0.9630 in the distance and for the oak stand, 0.9296 in DBH and 0.9565 in the distance. 3. The optimum regression equation for pine stand and oak stand were made by combination of two variables (DBH and distance). The table of noise attenuation was made by optimum regression equation. In the case of pine stand, the attenuation ratio was 29% at 5m, 31.6~32.6% at 10m, 38.3~39.8% at 20m and 45.2~46.6% at 30m. And case of oak stand, the attenuation ratio was 29% at 5m, 31.6~34.2% at 10m, 38.6~41.4% at 20m and 45~47.2% at 30m. 4. As the noise pressure limit at the Urban housing area according to environmental laws is under 55dB, it is suggested by the table of noise attenuation that the distance, and DBH for the pine and oak stand are over 20m, 400cm and 30-35 trees, respectively.

• Journal of Korean Society of Water and Wastewater
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• v.26 no.2
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• pp.257-264
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• 2012

The concept of a non-contact type of UV disinfection system was introduced in this study. UV lamps and their quartz sleeves hang over the water surface and there is no interface between the sleeve and water. Obviously, there is no fouling. Based on optical laws and other UV distribution models, a detail mathematical model for a non-contact type UV disinfection system was developed in this study. Pathway length of UV light in a non-contact type photoreactor is longer than that in a submerged type photoreactor because the light is more refractive while passing through 3 interfaces of medium. But the pathway length passing through the water media is not significantly longer than that in a submerged type photoreactor so, the absorption of UV light by water is not significantly different from the other system. Due to the reflection effect, UV intensity is rapidly decreased as the horizontal distance from the light source is increased. The reflective attenuation in a non-contact type photoreactor is higher than that in a submerged type photoreactor. These mean that the short photoreactor is advantageous than the narrow-long photoreactor for the non-contact type photoreactor in an optical point of view.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.7 s.250
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• pp.612-621
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• 2006

Drawing is a mechanical operation attenuating material thickness to an appropriate level for the next processing or end usage. When the input material has a form of bundle or bundles made of very thin and long shaped wires or fibers, this attenuation operation is called 'bundle drawing' or 'drafting'. Bundle drawing is being used widely in manufacturing micro sized wires or staple yarns. However, the bundle processed by this operation has more or less defects in the evenness of linear density. Such irregularities cause many problems not only for the product quality but also for the efficiency of the next successive processes. In this research a mathematical model for the dynamic behavior of the bundle fluid is to be set up on the basis of general physical laws containing physical variables, i.e. linear density and velocity as the dynamic state variables of the bundle fluid. The governing equations resulting from the modeling show that they appear in a slightly different form from what they do in a continuum fluid. Then, the governing equations system is simplified in a steady state and the bundle dynamics is simulated, showing that the shape of the velocity profiles depends on two model parameters. Experiments confirm that the model parameters are to be well adjusted to show a coincidence with the theoretical analysis. The higher the drawing ratio and drawing speed we, the more sensitive becomes the bundle flow to exogenous disturbances.