The interference of a semi-submerged obstacle on the porous breakwater     

H. T. Ou Yang  L. H. Huang  W. S. Hwang 《Applied Ocean Research》1997,19(5-6):263-273

The interaction of a linear water wave in a channel of constant depth impinging on a vertical thin porous breakwater with a semi-submerged and fixed rectangular obstacle in front of it is investigated. The water follows conventional assumptions as an irrotational, incompressible, and inviscid fluid flow. The solid skeleton of the porous breakwater is assumed to be rigid and thin. We get the general solution by applying the eigenfunction expansion method and solve it with a numerical matrix solver. In order to verify the correctness of the general solution, wave flume experiments are conducted. Two asymptotic solutions for long and short incoming waves are also obtained. Both experiments and asymptotic solutions show good agreement with the general solution at proper limits. Finally, the effect of the fixed obstacle on the porous breakwater is discussed, and a general guide of how to obtain better energy trapping is delivered.  相似文献   

Behaviour of Cyclopoid, Harpacticoid, and Calanoid Copepods from Coastal Waters of Taiwan   总被引：1，自引：0，他引：1  

Jiang-Shiou  Hwang Jefferson T.  Turner 《Marine Ecology》1995,16(3):207-216

Abstract. Cinematographic techniques were used to compare behaviour patterns of three cyclopoid, one harpacticoid, and two calanoid species of copepods from coastal waters of Taiwan. Behaviour was quantified in terms of allocation of time to swimming versus non-swimming behaviour, and behavioural transitions/minute. The different species of copepods exhibited different patterns of behaviour. Oithona nana and O. similis had long periods of inactivity punctuated by comparatively few transitions to intermittent leaps of motion. Oncaea venusta had a more jerky pattern of numerous small hops with frequent transitions between motion and rest. Macrosetella gracilis spent more time swimming than did the cyclopoids, but with fewer behavioural transitions than O. venusta , more like the Oithona species. Temora turbinala swam virtually continuously and transitions to non-swimming were rare. Undinula vulgaris var. taiwanicus frequently alternated between upward motion and sinking at rest, making a feeding current about a fourth of the time. There was considerable intraspecific variability between individual animals, but for reasons of experimental design, it was impossible to statistically test the significance of this variation. Differences in behaviour patterns between the different species are discussed within the context of what is known about the feeding ecology of these species from previous investigations.  相似文献   

Recognition of design symbols from midship drawings     

Ho-Jin Hwang  Soonhung Han  Yong-Dae Kim 《Ocean Engineering》2005,32(16):1968-1981

Despite the availability of 3D CAD systems, the designers in shipyards still use 2D CAD systems because of the need to produce drawings rapidly and a shortage of labor. The shipyard spends much time and labor analyzing the design information contained in 2D drawings and creating 3D model for the downstream processes. The design information is represented by symbols that are well known among designers in shipyard. Symbols are expressed by meaningless geometric shapes. These shapes are recognized to have meanings by analysis of experienced and knowledgeable designers.We propose a method for automatic recognition of 2D symbols and the extraction of design information from the midship drawings. The shape and rationale of 2D symbols used in ship design have been analyzed, and symbols have been classified according to the analysis. Based on the classified symbols, the developed system recognizes the symbols expressed in 2D drawings. The extracted design information is assorted by design rationales. The meaningless geometric shape is translated into the design information including designer's intents. The extracted design data can be applied to the design process in shipyards, and the 3D ship model can be automatically created.  相似文献   

Quality assessment of FORMOSAT-3/COSMIC and GRACE GPS observables: analysis of multipath, ionospheric delay and phase residual in orbit determination   总被引：2，自引：2，他引：0  

Cheinway Hwang  Tzu-Pang Tseng  Ting-Jung Lin  Dražen Švehla  Urs Hugentobler  Benjamin Fong Chao 《GPS Solutions》2010,14(1):121-131

The precise orbit determination antennas of F3/C and GRACE-A satellites are from the same manufacturer, but are installed in different configurations. The current orbit accuracy of F3/C is 3 cm at arcs with good GPS data, compared to 1 cm of GRACE, which has a larger ratio of usable GPS data. This paper compares the qualities of GPS observables from F3/C and GRACE. Using selected satellites and time spans, the following average values for the satellite F3/C and satellite A of GRACE are obtained: multipath effect on the pseudorange P1, 0.78 and 0.38 m; multipath effect on the pseudorange P2, 1.03 and 0.69 m; occurrence frequency of cycle slip, 1/29 and 1/84; standard error of unit weight, 4 and 1 cm; dynamic–kinematic orbit difference, 10 and 2 cm. For gravity determination using F3/C GPS data, a careful selection of GPS data is critical. With six satellites in orbit, F3/C’s large amount of GPS data will make up the deficiency in data quality.  相似文献   

Mitigation of micro vibration by viscous dampers   总被引：1，自引：1，他引：0  

Tzu-Kang Lin  Chu-Chieh Jay Lin  Jenn-Shin Hwang 《地震工程与工程振动(英文版)》2009,8(4):569-582

This study proposes a micro vibration mitigation system using viscous dampers to solve the problem of vibration in a high-tech building.Due to the operating frequency of the air conditioners and fundamental mode of the floors,a resonant phenomenon is occasionally experienced at the upper levels of the structure.Several strategies were considered,and viscous dampers combined with a suspension system were chosen to mitigate this annoying situation.A theoretical analysis was f irst executed to determine the op...  相似文献   

Solar-wind–magnetosphere coupling,including relativistic electron energization,during high-speed streams     

L.R. Lyons  D.-Y. Lee  H.-J. Kim  J.A. Hwang  R.M. Thorne  R.B. Horne  A.J. Smith 《Journal of Atmospheric and Solar》2009,71(10-11):1059-1072

High geomagnetic activity occurs continuously during high-speed solar wind streams, and fluxes of relativistic electrons observed at geosynchronous orbit enhance significantly. High-speed streams are preceded by solar wind compression regions, during which time there are large losses of relativistic electrons from geosynchronous orbit. Weak to moderate geomagnetic storms often occur during the passage of these compression regions; however, we find that the phenomena that occur during the ensuing high-speed streams do not depend on whether or not a preceding storm develops. Large-amplitude Alfvén waves occur within the high-speed solar wind streams, which are expected to lead to intermittent intervals of significantly enhanced magnetospheric convection and to thus also lead to repetitive substorms due to repetitively occurring reductions in the strength of convection. We find that such repetitive substorms are clearly discernible in the LANL geosynchronous energetic particle data during high-speed stream intervals. Global auroral images are found to show unambiguously that these events are indeed classical substorms, leading us to conclude that substorms are an important contributor to the enhanced geomagnetic activity during high-speed streams. We used the onsets of these substorms as indicators of preceding periods of enhanced convection and of reductions in convection, and we have used ground-based chorus observations from the VELOX instrument at Halley station as an indicator of magnetospheric chorus intensities. These data show evidence that it is the periods of enhanced convection that precede substorm expansions, and not the expansions themselves, that lead to the enhanced dawn-side chorus wave intensity that has been postulated to cause the energization of relativistic electrons. If this inference is correct, and if it is chorus that energizes the relativistic electrons, then high-speed solar wind streams lead to relativistic electron flux enhancements because the embedded large-amplitude Alfvén waves give multi-day periods of intermittent significantly enhanced convection.  相似文献   

Groundwater Impacts from the M5.8 Earthquake in Korea as Determined by Integrated Monitoring Systems     

Soo-Hyoung Lee  Jae Min Lee  Heesung Yoon  Yongcheol Kim  Seho Hwang  Kyoochul Ha  Yongje Kim 《Ground water》2020,58(6):951-961

This paper describes the impacts of the M5.8(5.1) Gyeongju earthquakes on groundwater levels using data obtained from a unique coastal monitoring well. The monitoring strategy integrates conventional water level monitoring with periodic, continuous measurements of temperature and electrical conductivity (EC) within the water column of the well. Another important component of the monitoring system is a new instrument, the InterfacEGG, which is capable of dynamically tracking the freshwater-saltwater interface. Although the system was set up to monitor seawater intrusion related to over-pumping, as well as rainfall and tidal effects, it recorded impacts associated with a large earthquake and aftershocks approximately 241 km away. Seismic energies associated with the M5.8(5.1) Gyeongju earthquakes induced groundwater flows to the monitoring well through fractures and joints in the crystalline basement rocks. Temperature and EC logging data showed that the EC vertical profile declined from an average of approximately 5300 to 4800 μS/cm following the earthquakes. The temperature profile showed a trend toward lower temperatures as the depth increased, a feature not commonly observed in previous studies. Data from the InterfacEGG suggested that the rise in EC was not due to the saltwater intrusion, but from the tendency for brackish water entering the borehole to induce convective mixing at deeper depths as the seismic waves travel through the well-aquifer system. The increase in groundwater levels was caused by pulse of colder, less brackish water flowing into the well because of the earthquake. This behavior reflects an enhancement in rock permeability by removing precipitates and colloidal particles from clogged fractures, which improve the hydraulic connection with a nearby unit with a higher hydraulic head. This study suggests there is value added with a more aggressive monitoring strategy.  相似文献   

Natural Stimuli Calibration with Fining Direction Regularization in an Integrated Hydrologic Model     

Steven J. Berg  Nancy R. Grosso  Michael P. Sherrier  Kevin Mudrick  Matthias Ohr  Hyoun-Tae Hwang  Young-Jin Park  Michael V. Callaghan  Steven K. Frey  Edward A. Sudicky 《Ground water》2019,57(1):21-35

The interaction between surface water and groundwater during flood events is a complex process that has traditionally been described using simplified analytical solutions, or abstracted numerical models. To make the problem tractable, it is common to idealize the flood event, simplify river channel geometry, and ignore bank soil heterogeneity, often resulting in a model that only loosely represents the site, thus limiting its applicability to any specific river cross-section. In this study, we calibrate a site-specific fully-integrated surface and subsurface HydroGeoSphere model using flood events for a cross-section along the South River near Waynesboro, VA. The calibration approach presented in this study demonstrates the incorporation of fining direction regularization with a highly parameterized inversion driven by natural stimuli, to develop several realistic realizations of hydraulic conductivity fields that reflect the depositional history of the system. Specifically, we calibrate a model with 365 unique material zones to multiple flood events recorded in a dense well network while incorporating possible fining sequences consistent with the depositional history of the riverbank. Over 25,000 individual simulations were completed using calibration software and a cloud platform specifically designed for highly parallelized computing environments. The results of this study demonstrate the use of fining direction regularization during model calibration to generate multiple calibrated model realizations that account for the depositional environment of the system.  相似文献   

Erratum to: Relationship of ground level enhancements with?solar, interplanetary and geophysical parameters     

K. A. Firoz  J. Hwang  I. Dorotovi?  T. Pintér  Subhash C. Kaushik 《Astrophysics and Space Science》2011,332(1):219

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Biomagnification of persistent chlorinated and brominated contaminants in food web components of the Yellow Sea     

Gyo-Hyuk Byun  Hyo-Bang Moon  Jung-Hwa Choi  Jeomshik Hwang  Chang-Keun Kang 《Marine pollution bulletin》2013

Concentrations of polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), and polybrominated diphenyl ethers (PBDEs) were measured in 32 species inhabiting the Yellow Sea to assess their bioaccumulation potentials. The concentrations in these samples were lower than those reported for other countries or locations. Relatively high levels of BDE 209 in biota suggest an ongoing source of deca-BDE technical mixing within the Yellow Sea. The accumulation profiles of PCBs were uniform between species, but the concentrations of OCPs and PBDEs varied widely. Pelagic and benthic food-chain components were separated by their δ¹³C values. Significant positive correlations between δ¹⁵N and PCB 153, PCB 138, p,p′-DDE, oxy-chlordane, and trans-nonachlordane were found only for pelagic consumers, indicating that the pelagic food chain is an important bioaccumulation pathway for selected PCB and OCP compounds. The other compounds did not show any biomagnification through benthic and pelagic food chains, suggesting the lower bioaccumulation potentials of these contaminants.  相似文献