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41.
Bok Kyoung Choi Suk Wang Yoon 《Oceanic Engineering, IEEE Journal of》2001,26(1):125-130
Sound attenuation has been solely used to estimate bubble size distributions of bubbly water in the conventional acoustic bubble sizing methods. These conventional methods are useful for the void fraction around 10-6 or lower. However, the change of compressibility in the bubbly water also should be considered in bubble sizing for the void fraction around 10-5 or higher. Recently the sound speed as well as sound attenuation was considered for acoustic bubble size estimation in bubbly water. In this paper, the sound speed estimated from sound attenuation in bubbly water by an iterative method is used for a bubble counting. This new iterative inverse bubble sizing technique is numerically tested for bubble distributions of single-size Gaussian, and power-law functions. The numerical simulation results are in agreement with the given bubble distributions even for the high void fractions of 10-4-10-3. It suggests that the iterative inverse technique can be a very powerful tool for practical use in acoustic bubble counting in the ocean 相似文献
42.
Natural Hazards - Future storm-induced inundation risks were assessed by performing storm surge modeling based on Typhoon Maemi (2003) under the generic climate change scenarios proposed by IPCC... 相似文献
43.
This study presents the correlations between quantified shape parameters and geotechnical properties for nine sand specimens. Four shape parameters, sphericity, convexity, elongation and slenderness, were quantified with two-dimensional microscopic images with the aid of image processing techniques. An instrumented oedometer cell is used to measure compressibility, thermal conductivity and shear wave velocity during loading, unloading and reloading stages. As the particle shape inherently determines the initial loose packing condition, initial void ratio and shape parameters are well correlated with compressibility. The applied stress in soils increases the interparticle contact area and contact quality; round particles tend to achieve higher thermal conductivity and shear wave velocity during stress-induced volume change. Multiple linear regression is implemented to capture the relative contributions of involved variables, revealing that the thermal evolution is governed by the initial packing density and particle shape. The experimental observations underscore the predominant effect that particle shape has on the geomechanical and physical properties upon stress-induced soil behavior. 相似文献
44.
Amir Hossein Hakimhashemi Jeoung Seok Yoon Oliver Heidbach Arno Zang Gottfried Grünthal 《Journal of Seismology》2014,18(3):671-680
The M w 3.2-induced seismic event in 2006 due to fluid injection at the Basel geothermal site in Switzerland was the starting point for an ongoing discussion in Europe on the potential risk of hydraulic stimulation in general. In particular, further development of mitigation strategies of induced seismic events of economic concern became a hot topic in geosciences and geoengineering. Here, we present a workflow to assess the hazard of induced seismicity in terms of occurrence rate of induced seismic events. The workflow is called Forward Induced Seismic Hazard Assessment (FISHA) as it combines the results of forward hydromechanical-numerical models with methods of time-dependent probabilistic seismic hazard assessment. To exemplify FISHA, we use simulations of four different fluid injection types with various injection parameters, i.e. injection rate, duration and style of injection. The hydromechanical-numerical model applied in this study represents a geothermal reservoir with preexisting fractures where a routine of viscous fluid flow in porous media is implemented from which flow and pressure driven failures of rock matrix and preexisting fractures are simulated, and corresponding seismic moment magnitudes are computed. The resulting synthetic catalogues of induced seismicity, including event location, occurrence time and magnitude, are used to calibrate the magnitude completeness M c and the parameters a and b of the frequency-magnitude relation. These are used to estimate the time-dependent occurrence rate of induced seismic events for each fluid injection scenario. In contrast to other mitigation strategies that rely on real-time data or already obtained catalogues, we can perform various synthetic experiments with the same initial conditions. Thus, the advantage of FISHA is that it can quantify hazard from numerical experiments and recommend a priori a stimulation type that lowers the occurrence rate of induced seismic events. The FISHA workflow is rather general and not limited to the hydromechanical-numerical model used in this study and can therefore be applied to other fluid injection models. 相似文献
45.
Stability Study of a Tide Embankment Subjected to Sea Level Variations Using Centrifugal Model Tests
Chung-Won Lee Yong-Sun Yoon Dong-Su Chang Yun Wook Choo Min-Chul Jung 《Marine Georesources & Geotechnology》2013,31(5):376-390
To investigate the behavior of dredged-sea-sand fill compacted inside tide embankments with a damaged geosynthetic mat, centrifugal model tests and numerical simulation were conducted, both considering variations in sea level. The results from the three centrifugal model tests demonstrate that the subsidence of the dredged-sea-sand fill inside tide embankments with a damaged geosynthetic mat was strongly affected by the loss of dredged-sea-sand into the filter layers with large particles and a decrease in the bearing capacity of the filter layers with small particles. In addition, a comparison of the test and simulation results confirms that the loss of sand into the filter layer and the subsidence of the dredged-sea-sand fill were well reproduced by the numerical simulation. 相似文献
46.
Astrid Lampert Johan Ström Christoph Ritter Roland Neuber Young Jun Yoon Nam Yi Chae Masataka Shiobara 《Acta Geophysica》2012,60(5):1287-1307
An inclined lidar with vertical resolution of 0.4 m was used for detailed boundary layer studies and to link observations at Zeppelin Mountain (474 m) and Ny-Ålesund, Svalbard. We report on the observation of aerosol layers directly above the Kongsfjord. On 29 April 2007, a layer of enhanced backscatter was observed in the lowest 25 m above the open water surface. The low depolarization ratio indicated spherical particles. In the afternoon, this layer disappeared. The ultrafine particle concentration at Zeppelin and Corbel station (close to the Kongsfjord) was low. On 1 May 2007, a drying process in the boundary layer was observed. In the morning, the atmosphere up to Zeppelin Mountain showed enhanced values of the backscatter coefficient. Around noon, the top of the highly reflecting boundary layer decreased from 350 to 250 m. The top of the boundary layer observed by lidar was confirmed by radiosonde data. 相似文献
47.
We examined the respiration rate of Aurelia aurita medusae at 20 °C and 28 °C to evaluate minimum metabolic demands of medusae population in Sihwa Lake, Korea during summer. While weight specific respiration rates of medusae were constant and irrespective to the wet weight (8?C220 g), they significantly varied in respect to temperatures (p<0.001, 0.11±0.03 mg C g?1 of medusa d?1 at 20°C and 0.28±0.11 mg C g?1 of medusa d?1 at 28 °C in average, where Q 10 value was 2.62). The respiration rate of medusae was defined as a function of temperature (T, °C) and body weight (W, g) according to the equation, R=0.13×2.62(T-20)/10 W 0.93. Population minimum food requirement (PMFR) was estimated from the respiration rate as 15.06 and 4.86 mg C m?3 d?1 in June and July, respectively. During this period, increase in bell diameter and wet weight was not significant (p=1 in the both), suggesting that the estimated PMFR closely represented the actual food consumption in the field. From July to August, medusae grew significantly at 0.052 d-1, thus the amount of food ingested by medusae population in situ was likely to exceed the PMFR (1.27 mg C m?3 d?1) during the period. In conclusion, the medusae population of higher density during June and July had limited amount of food, while those of lower in July and August ingested enough food for growth. 相似文献
48.
Hyeon Ho Shin Koichiro Mizushima Jong Sick Park Mitsunori Iwataki Yang Ho Yoon 《Marine pollution bulletin》2010,60(8):1243-1258
Dinoflagellate cysts acquired from sediment cores were analyzed in order to reconstruct historical nutrient levels in Gamak Bay, Korea and Ariake Bay, Japan. Dinoflagellate cyst assemblages in Gamak Bay were characterized by high proportions of heterotrophic cysts such as Brigantedinium spp., Protoperidinium americanum and Polykrikos cysts, which suggested that nutrients levels may have already been high before 1970s, and then increased further to the hypertrophic conditions of the 1990s. In contrast, dinoflagellate cyst assemblages in Ariake Bay were characterized by high relative abundances of Lingulodinium machaerophorum and Spiniferites spp., which suggested that nutrient levels in Ariake Bay had increased gradually since the mid 1960s, and may have been significantly enhanced by the mid 1980s. Dinoflagellate cyst assemblages reflecting environmental changes in the two bays are contrasting, perhaps due to different nutrient enrichment mechanisms. This suggests that the indicators of nutrient levels encoded in dinoflagellate cyst assemblages may exhibit site-specific information. 相似文献
49.
Rural heritage that involves agricultural heritage could be critical to enhancing community identity through a conservational approach. The purpose of this research is to develop conservational methods for rural heritage that include agricultural heritage areas through the use of ecomuseums. To conduct the research, we first reviewed the concepts of ecomuseum and rural heritage. Secondly, we defined the concept of the Korean rural ecomuseum by taking into consideration the concept defined by Riviere, Globally Important Agricultural Heritage Systems (GIAHS), the rural heritage policy of Europe, and the agricultural heritage systems of Korea. Thirdly, we also describe methods that are applicable to Korean rural ecomuseums, which include type classification and components. Finally, we applied the ecomuseum concept to two pilot models in the Cheongsando and Gurae areas, both Korea Important Agricultural Heritage System (KIAHS) sites. We conclude that it is desirable to expand the range of targets for conservation from agricultural heritage to rural heritage areas. From this point of view, the rural ecomuseum can be a highly valuable tool that can help preserve agricultural heritage sites and neighboring areas. Furthermore, the ecomuseum can enhance community identities, and strengthen local economies. 相似文献
50.
Hyunsun Do Michael Brady Demetri P. Telionis Pavlos P. Vlachos Roe-Hoan Yoon 《International Journal of Mineral Processing》2011,98(1-2):66-73
Numerical and experimental results of drying and wetting foam are presented. Foam can be wetted by wash water delivered on its top boundary, or drained by allowing the liquid to move downward in response to gravity. These processes are governed by nonlinear equations that in special cases accept exact solutions. Here we develop a numerical model that satisfies realistic boundary conditions. Numerical results are presented in conjunction with experiments conducted with coarsening foam. In addition, calculations were carried out modeling the wetting and draining of coarsened foam. From the simulations and experiments, coarsening bubbles were found responsible for accelerating drainage, or vice versa. 相似文献