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111.
Kangseok Hwang Eun-A Yoon Sukyung Kang Hyungkee Cha Kyounghoon Lee 《Ocean Science Journal》2017,52(4):563-571
The present study focuses on the influence of target strength (TS) changes in the swimming angle of the hairtail (Trichiurus lepturus). We measured in-situ TS at 38 and 120 kHz with luring lamps at a fishing ground for jigging boats near the coastal waters of Jeju-do in Korea. Swimming angle and size of hairtails were measured using an acoustic camera. Results showed that mean preanal length was estimated to be 13.5 cm (SD = 2.7 cm) and mean swimming tilt angle was estimated to be 43.9° (SD = 17.6°). The mean TS values were ?35.7 and ?41.2 dB at 38 and 120 kHz, respectively. The results will assist in understanding the influence of swimming angle on the TS of hairtails and, thus, improve the accuracy of biomass estimates. 相似文献
112.
A new orthometric correction (OC) formula is presented and tested with various mean gravity reduction methods using leveling, gravity, elevation, and density data. For mean gravity computations, the Helmert method, a modified Helmert method with variable density and gravity anomaly gradient, and a modified Mader method were used. An improved method of terrain correction computation based on Gaussian quadrature is used in the modified Mader method. These methods produce different results and yield OCs that are greater than 10 cm between adjacent benchmarks (separated by 2 km) at elevations over 3000 m. Applying OC reduces misclosures at closed leveling circuits and improves the results of leveling network adjustments. Variable density yields variation of OC at millimeter level everywhere, while gravity anomaly gradient introduces variation of OC of greater than 10 cm at higher elevations, suggesting that these quantities must be considered in OC. The modified Mader method is recommended for computing OC.Acknowledgments.This study is supported by the Ministry of the Interior (MOI), Taiwan, under the project `Measuring gravity on first-order benchmarks'. The authors are grateful to F.S. Ning and his colleagues at BSB (Base Survey Battalion) for their precision work in collecting gravity data, and to R. Forsberg for the terrain correction program. They also thank the Institute of Agricultural and Forestry Aerial Survey for elevation data and MOI for leveling data. Dr. Will Featherstone and three anonymous reviewers are thanked for their constructive comments. 相似文献
113.
114.
In this paper, known simplified methods for the assessment of soil liquefaction are summarized. Their discrepancies are examined. Using the Chi-Chi earthquake data as well as other reported data, a set of three critical cyclic strength curves were obtained by finding the minimum of misclassified points. The functional forms of these three curves are an exponential function, a hyperbola, and a cubic polynomial. A lower bound critical cyclic strength curve is then established. This curve may have important applications in practice for liquefaction-related designs. Through this case study, it was found that a minimum cyclic strength CSRlim may exist at a very low value of (N1)60. An upper limit (N1)60upp also exists beyond which liquefaction may not occur. Furthermore, current simplified methods seem suitable only for a limited range of N values and fines content, and may fail for general applications. The lower bound curve proposed in this paper may provide an alternative approach for improvement. Since the explicit functional form and the statistical indices are available, the statistically regressed curves seem to have a benefit in that it may be used directly to conduct hazard analysis, and evaluate the uncertainty within the critical cyclic strength curves. 相似文献
115.
Global mean sea surface heights (SSHs) and gravity anomalies on a 2′×2′ grid were determined from Seasat, Geosat (Exact Repeat Mission and Geodetic Mission), ERS-1 (1.5-year mean of 35-day, and
GM), TOPEX/POSEIDON (T/P) (5.6-year mean) and ERS-2 (2-year mean) altimeter data over the region 0∘–360∘ longitude and –80∘–80∘ latitude. To reduce ocean variabilities and data noises, SSHs from non-repeat missions were filtered by Gaussian filters
of various wavelengths. A Levitus oceanic dynamic topography was subtracted from the altimeter-derived SSHs, and the resulting
heights were used to compute along-track deflection of the vertical (DOV). Geoidal heights and gravity anomalies were then
computed from DOV using the deflection-geoid and inverse Vening Meinesz formulae. The Levitus oceanic dynamic topography was
added back to the geoidal heights to obtain a preliminary sea surface grid. The difference between the T/P mean sea surface
and the preliminary sea surface was computed on a grid by a minimum curvature method and then was added to the preliminary
grid. The comparison of the NCTU01 mean sea surface height (MSSH) with the T/P and the ERS-1 MSSH result in overall root-mean-square
(RMS) differences of 5.0 and 3.1 cm in SSH, respectively, and 7.1 and 3.2 μrad in SSH gradient, respectively. The RMS differences
between the predicted and shipborne gravity anomalies range from 3.0 to 13.4 mGal in 12 areas of the world's oceans.
Received: 26 September 2001 / Accepted: 3 April 2002
Correspondence to: C. Hwang
Acknowledgements. This research is partly supported by the National Science Council of ROC, under grants NSC89-2611-M-009-003-OP2 and NSC89-2211-E-009-095.
This is a contribution to the IAG Special Study Group 3.186. The Geosat and ERS1/2 data are from NOAA and CERSAT/France, respectively.
The T/P data were provided by AVISO. The CLS and GSFC00 MSS models were kindly provided by NASA/GSFC and CLS, respectively.
Drs. Levitus, Monterey, and Boyer are thanked for providing the SST model. Dr. T. Gruber and two anonymous reviewers provided
very detailed reviews that improved the quality of this paper. 相似文献
116.
Assessment of groundwater chemistry in a coastal region (Kunsan, Korea) having complex contaminant sources: a stoichiometric approach 总被引:1,自引:0,他引:1
Kangjoo Kim Natarajan Rajmohan Hyun Jung Kim Gab-Soo Hwang Min Joe Cho 《Environmental Geology》2004,46(6-7):763-774
Groundwater chemistry in a coastal region (Kunsan, Korea) having complex contaminant sources was investigated. Water analysis data for 197 groundwater samples collected from the uniformly distributed sixty-six wells were used. Chemical analysis results indicate that groundwaters show wide concentration ranges in major inorganic ions, reflecting complex hydrochemical processes. Due to the complexity of groundwater chemistry, the samples were classified into four groups based on Cl and NO3 concentrations and the processes controlling water chemistry were evaluated based on the reaction stoichiometry. The results explained the importance of mineral weathering, anthropogenic activities (nitrification and oxidation of organic matters), and Cl-salt inputs (seawater, deicer, NaCl, etc.) on groundwater chemistry. It was revealed that mineral dissolution is the major process controlling the water chemistry of the low Cl and NO3 group (Group 1). Groundwaters high in NO3 (Groups 2 and 4) are acidic in nature, and their chemistry is largely influenced by nitrification, oxidation of organic matters and mineral dissolution. In the case of chloride rich waters (Group 3), groundwater chemistry is highly influenced by mineral weathering and seawater intrusion associated with cation-exchange reactions. 相似文献
117.
Yongen Cai Chi-yuen Wang Win-tsuang Hwang Guy R. Cochrane 《Pure and Applied Geophysics》1995,145(3-4):637-646
Fluid venting in accretionary prisms, which feeds chemosynthetic biological communities, occurs mostly on the marginal thrust ridge. New seismic data for the marginal ridge of the Cascadia prism show significantly lower velocity than that in the adjacent oceanic basin and place important constraints on the interpretations of why fluid venting occurs mostly on the marginal ridge. We employed a finite-element method to analyze a typical fault-bend folding model to explain the phenomenon. The fault in the model is simulated by contact elements. The elements are characterized not only by finite sliding along a slide line, but also by elastoplastic deformation.We present the results of a stress analysis which show that the marginal ridge is under subhorizontal extension and the frontal thrust is under compression. This state of stress favors the growth of tensile cracks in the marginal ridge, facilitates fluid flow and reduces seismic velocities therein; on the other hand, it may close fluid pathways along the frontal thrust and divert fluid flow to the marginal ridge.On leave from Peking University, Beijing, 100871, China 相似文献
118.
A large quantity of by-product lime wastes with high water content produced from chemicals manufacturing processes has been stacked in an open area in Incheon, Korea. Highly alkaline leachate and fine dust emanating from the stacked lime wastes caused an environmental concern in the city. So evaporative drying and stabilization of the fine-grained wastes and use of the on site marine clay as a natural geomembrane liner using drying hardening were considered as a part of a landfill construction plan. Treatment of the lime wastes and marine clay was focused on maximizing the evaporative drying and the density. Evaporation experiments were conducted in field condition to understand evaporation characteristics and to evaluate actual evaporation rate of the lime wastes and marine clay. Local Class A pan evaporation data from a nearby weather station for last 30 years indicated that mean annual and monthly evaporations were 1,178.5 and 98.2 mm, respectively. Relative evaporations of the sludge lime, cake lime, and marine clay compared with the pan evaporation were 114.9, 61.9, and 119.0%, respectively. Estimates of annual evaporations from storage surfaces in the field based on the relative evaporation data were 1,353.6, 729.1, and 1,402.2 mm for the sludge lime, cake lime, and the marine clay, respectively. And annual net evaporations considering rainfall effect were estimated as between 879.9 and 1,082.9 mm for the lime sludge, between 473.9 and 583.3 mm for the lime cake, and between 981.5 and 1,191.9 mm for the marine clay. It was expected that the actual field evaporation rate would be varied with the moisture contents of the lime and the clay. Results of these experiments will provide useful implications for the drying behavior of the by-product lime and the marine clay and landfill or management plan of the storages. 相似文献
119.
Electrostatic waves excited by a field-aligned electron current sheet of finite thickness are investigated. The finite width of the current sheet gives rise to boundary conditions to be satisfied at the sheet edge. This results in a restriction to the number of modes which may be driven unstable. Ducted and evanescent mode solutions are obtained. It is shown that the finite thickness of the current sheet partially stabilizes the system and contributes to the coherence of the excited waves. 相似文献
120.
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