This study considers the coupling effects of ship motion and sloshing. The linear ship motion is solved using an impulse-response-function (IRF) method, while the nonlinear sloshing flow is simulated using a finite-difference method. The IRF method requires the frequency-domain solution prior to conversion to time domain, but the computational effort is much less than that of direct time-domain approaches. The developed scheme is verified by comparing the motion RAOs between the frequency-domain solution and the solution obtained by the IRF method. Furthermore, a soft-spring concept and linear roll damping are implemented to predict more realistic motions of surge, sway, yaw, and roll. For the simulation of sloshing flow in liquid tanks, a physics-based numerical approach adopted by Kim [2001. Numerical simulation of sloshing flows with impact load. Applied Ocean Research 23, 53–62] and Kim et al. [2004. Numerical study on slosh-induced impact pressures on three-dimensional prismatic tanks. Applied Ocean Research 26, 213–226] is applied. In particular, the present method focuses on the simulation of the global motion of sloshing flow, ignoring some local phenomena. The sloshing-induced forces and moments are added to wave-excitation forces and moments, and then the corresponding body motion is obtained. The developed schemes are applied for two problems: the sway motion of a box-type barge with rectangular tanks and the roll motion of a modified S175 hull with rectangular anti-rolling tank. Motion RAOs are compared with existing results, showing fair agreement. It is found that the nonlinearity of sloshing flow is very important in coupling analysis. Due to the nonlinearity of sloshing flow, ship motion shows a strong sensitivity to wave slope. 相似文献
Long-term, continuous, and real-time ocean monitoring has been undertaken in order to evaluate various oceanographic phenomena
and processes in the East/Japan Sea. Recent technical advances combined with our concerted efforts have allowed us to establish
a real-time monitoring system and to accumulate considerable knowledge on what has been taking place in water properties,
current systems, and circulation in the East Sea. We have obtained information on volume transport across the Korea Strait
through cable voltage measurements and continuous temperature and salinity profile data from ARGO floats placed throughout
entire East Sea since 1997. These ARGO float data have been utilized to estimate deep current, inertial kinetic energy, and
changes in water mass, especially in the northern East Sea. We have also developed the East Sea Real-time Ocean Buoy (ESROB)
in coastal regions and made continual improvements till it has evolved into the most up-to-date and effective monitoring system
as a result of remarkable technical progress in data communication systems. Atmospheric and oceanic measurements by ESROB
have contributed to the recognition of coastal wind variability, current fluctuations, and internal waves near and off the
eastern coast of Korea. Long-term current meter moorings have been in operation since 1996 between Ulleungdo and Dokdo to
monitor the interbasin deep water exchanges between the Japanese and Ulleung Basins. In addition, remotely sensed satellite
data could facilitate the investigation of atmospheric and oceanic surface conditions such as sea surface temperature (SST),
sea surface height, near-surface winds, oceanic color, surface roughness, and so on. These satellite data revealed surface
frontal structures with a fairly good spatial resolution, seasonal cycle of SST, atmospheric wind forcing, geostrophic current
anomalies, and biogeochemical processes associated with physical forcing and processes. Since the East Sea has been recognized
as a natural laboratory for global oceanic changes and a clue to abrupt climate change, we aim at constructing a 4-D continuous
real-time monitoring system, over a decade at least, using the most advanced techniques to understand a variety of oceanic
processes in the East Sea. 相似文献
The spatial and temporal distribution of redox zones in an aquifer is important when designing groundwater supply systems. Redox zonation can have direct or indirect control of the biological and chemical reactions and mobility of pollutants. In this study, redox conditions are characterized by interpreting the hydrogeological conditions and water chemistry in groundwater during bank infiltration at a site in Shenyang, northeast China. The relevant redox processes and zonal differences in a shallow flow path and deeper flow path at the field scale were revealed by monitoring the redox parameters and chemistry of groundwater near the Liao River. The results show obvious horizontal and vertical components of redox zones during bank filtration. Variations in the horizontal extent of the redox zone were controlled by the different permeabilities of the riverbed sediments and aquifer with depth. Horizontally, the redox zone was situated within 17 m of the riverbank for the shallow flow path and within 200 m for the deep flow path. The vertical extent of the redox zone was affected by precipitation and seasonal river floods and extended to 10 m below the surface. During bank filtration, iron and manganese oxides or hydroxides were reductively dissolved, and arsenic that was adsorbed onto the medium surface or coprecipitated is released into the groundwater. This leads to increased arsenic content in groundwater, which poses a serious threat to water supply security. 相似文献
Landslides - Deep into the night of 9 June 2021, a high-intensity and short-duration rainstorm, the largest rainfall ever recorded in Zhuji, struck the entire city. The abrupt rainfall triggered... 相似文献
Acta Geotechnica - One of the latest developments in biocementation is the use of one-phase-low-pH MICP or EICP method as a more effective and efficient alternative to the traditional two-phase... 相似文献
In sedimentology, stratigraphic sequences and cycles are ordered by time spans and physical scales, such as thickness, and bounded by discontinuities, including unconformities or flooding surfaces. Spectral analysis based on wavelet transform (WT) maxima is proposed and used as a quantitative tool to identify multi-order stratigraphic boundaries and cycles in well log data. The proposed spectral analysis is based on quantitative analysis on the center frequencies and resolutions of Gaussian wavelets in time and frequency, and uses a combination of the WT maxima based on both the first order Gaussian wavelet having a high time resolution and the seventh order Gaussian wavelet having a high frequency resolution. WT maxima spectra, which can characterize the evolution of WT maxima across scales and periods along WT maxima lines concerned with sequence boundaries, are used to detect dominant spectral peaks corresponding to the time-period domain WT maxima and to determine WT maxima spectral slopes. The WT maxima spectral slopes are helpful for discriminating sequence boundaries from intrasequence cyclic variations in well log data, and the time-period domain WT maxima are used to relate the detected boundaries to relevant cycles. The interval WT maxima spectra and the stationary index, related to the WT maxima spectra, are introduced as indicators that can be used for the hierarchical ordering of the boundaries and cycles. Application of the proposed method to well log data shows that the suggested method is efficient in identifying multi-order sequences that relate well to the Milankovitch cycles.
The likely effects on two tree species of a range of scenarios of climatic and atmospheric change expected by the year 2050 are investigated using a climatic mapping program, a simple simulation model and a process-based simulation model. Styrax tonkinensis is a native species for which relatively little information is available. Acacia mangium is an introduced species, which is important for pulp production in several other countries, and for which there is considerable information for growth and utilization. A climatic mapping program is used to show areas which may be suitable for these species under present and predicted conditions. Two simulation models are used to investigate likely effects on productivity of the two species for a range of climatic change scenarios for Hanoi and Ho Chi Minh City. The estimated changes in production are predicted to be relatively small, though uncertainities associated with the simulations are quite high. However, the models highlight areas where more data are needed and also suggest some key regions in Vietnam which would be worth monitoring to detect early signs of the effects of climatic and atmospheric change. 相似文献
The historical Golden Horn Estuary (GHE), near the confluence of the Istanbul Strait (Bosphorus) and the Sea of Marmara in
the European part of Istanbul, has been used as a natural harbor since 330 a.d. The sedimentary infill of the GHE is 15–46 m thick, deposited unconformably above the turbiditic sandstones of the Carboniferous
Trakya Formation. Chronostratigraphic and paleontological analyses of the infill sequence indicate that the GHE was a fluvial
channel prior to 13,500 cal. a (calibrated to calendar years) B.P. It subsequently became gradually influenced by marine waters,
and was a brackish-water environment until 9,500 cal. a B.P. Normal marine salinities prevailed at ca. 9,500−5,600 cal. a
B.P., with suboxic/dysoxic bottom-water conditions. The increase in salinity at 9,500 cal. a B.P. was most likely caused by
Mediterranean water outflow into the Black Sea through the Istanbul Strait. The estuary was influenced by large fluvial inputs
between 5,600 and 1,000 cal. a B.P., possibly during a distinct pluvial period, as shown by coarse siliciclastic sediments
deposited on the flanks. It has become a highly polluted environment with marked anthropogenic inputs during the last millennium.
The finding that the sediment infill sequence above the Carboniferous basement is not older than about 20 ka strongly suggests
that the Golden Horn Estuary acquired its present-day morphology during the late glacial–Holocene period. 相似文献