GPS Height and Gravity Variations Due to Ocean Tidal Loading Around Taiwan     

Ta-Kang Yeh  Cheinway Hwang  Guochang Xu 《Surveys in Geophysics》2009,30(1):51-51

  相似文献   

Gravity recovery using COSMIC GPS data: application of orbital perturbation theory   总被引：14，自引：0，他引：14  

C. Hwang 《Journal of Geodesy》2001,75(2-3):117-136

 COSMIC is a joint Taiwan–US mission to study the atmosphere using the Global Positioning System (GPS) occultation technique. Improved formulas are developed for the radial, along-track, and cross-track perturbations, which are more accurate than the commonly used order-zero formulas. The formulas are used to simulate gravity recovery using the geodetic GPS data of COSMIC in the operational phase. Results show that the EGM96 model can be improved up to degree 26 using 1 year of COSMIC data. TOPEX/POSEIDON altimeter data are used to derive a temporal gravity variation. COSMIC cannot reproduce this gravity variation perfectly because of data noise and orbital configuration, but the recovered field clearly shows the gravity signature due to mass movement in an El Ni?o. Received: 3 March 2000 / Accepted: 10 November 2000  相似文献   

Evaluation of the liquid hydrocarbon potential of coal by artificial maturation techniques     

S.C. Teerman  R.J. Hwang 《Organic Geochemistry》1991,17(6)

In certain areas, relatively large accumulations of liquid hydrocarbons have been attributed to coals. Evaluating the source rock potential of coal requires definition of both the generative potential (quantity and composition of generated hydrocarbons), and expulsion efficiency. Hydrous pyrolysis experiments were completed using Tertiary lignites (R_o < 0.35%) from North Dakota and the Far East to evaluate the source rock potential of coal. The North Dakota lignite is vitrinite-rich (93%) and liptinite-poor (3%); the Far East lignite is liptinite-rich (32% of total maceral content). These lignites have Hydrogen Index values of 123 and 483 mg HC/g OC, respectively. Differences in oil-pyrolysate yield, composition, and temperature of maximum pyrolysate yield from hydrous pyrolysis experiments for these two lignites are related to the type and amount of liptinite and vitrinite macerals. A maximum of 48 and 158 mg oil-pyrolysate/g OC is generated and expelled from the North Dakota and Far East lignites, respectively. Although these lignites consist predominantly of gas-prone vitrinitic components, their organic-rich nature can compensate for their poor convertibility to liquid hydrocarbons. The composition of these artificially generated oil-pyrolysates are similar to some non-marine oils, suggesting that this type of organic matter can be a significant contributor to many oils. Although the overall composition of the generated products from the two lignites is similar, the distribution of these products is significantly different. Homologous series of methyl ketones and alkyl benzenes have been identified in both oil-pyrolysates. Their presence and characteristic distribution suggest that microbial degradation occurred during the formation of these lignites. Although many coals generate significate amounts of liquid hydrocarbons that are similar to naturally occurring oils, poor explusion efficiency limits their source rock potential. Significant amounts of liquid products are assimilated by the vitrinitic matrix of most coals prior to expulsion, severely limiting the amount of petroleum available for migration and reservoir accumulation. However, adequate expulsion may occur in certain liptinite-rich coals or coals occurring in unique depositional settings.  相似文献   

Metagenomic characterization of viral communities in Goseong Bay,Korea     

Jinik Hwang  So Yun Park  Mirye Park  Sukchan Lee  Yeonhwa Jo  Won Kyong Cho  Taek-Kyun Lee 《Ocean Science Journal》2016,51(4):599-612

In this study, seawater samples were collected from Goseong Bay, Korea in March 2014 and viral populations were examined by metagenomics assembly. Enrichment of marine viral particles using FeCl₃ followed by next-generation sequencing produced numerous sequences. De novo assembly and BLAST search showed that most of the obtained contigs were unknown sequences and only 0.74% of sequences were associated with known viruses. As a result, 138 viruses, including bacteriophages (87%), viruses infecting algae and others (13%) were identified. The identified 138 viruses were divided into 11 orders, 14 families, 34 genera, and 133 species. The dominant viruses were Pelagibacter phage HTVC010P and Roseobacter phage SIO1. The viruses infecting algae, including the Ostreococcus species, accounted for 9.4% of total identified viruses. In addition, we identified pathogenic herpes viruses infecting fishes and giant viruses infecting parasitic acanthamoeba species. This is a comprehensive study to reveal the viral populations in the Goseong Bay using metagenomics. The information associated with the marine viral community in Goseong Bay, Korea will be useful for comparative analysis in other marine viral communities.  相似文献   

Long-lead station-scale prediction of hydrological droughts in South Korea based on bivariate pattern-based downscaling     

Soo-Jin Sohn  Chi-Yung Tam 《Climate Dynamics》2016,46(9-10):3305-3321

  相似文献   

Comparison of Ocean Surface Wind Stress Computed with Different Parameterization Functions of the Drag Coefficient     

Paul A. Hwang 《Journal of Oceanography》2005,61(1):91-107

Depending on the choice of reference wind speed, the quantitative and qualitative properties of the drag coefficient may vary. On the ocean surface, surface waves are the physical roughness at the air-sea interface, and they play an important role in controlling the air-sea exchange processes. The degree of dynamic influence of surface waves scales with wavelength. Drag coefficient computed with the reference wind speed at an elevation proportional to the wavelength (for example, U _λ/2) is fundamentally different from the drag coefficient computed with the wind speed at fixed 10 m elevation (U ₁₀). A comparison has been carried out to quantify the difference in wind stress computation using several different parameterization functions of the drag coefficient. The result indicates that the wind stress computed from U ₁₀ input using a drag coefficient referenced to U _λ/2 is more accurate than that computed with drag coefficient functions referenced to U ₁₀.  相似文献   

Wave transmission by overtopping due to random waves     

Ching-Her Hwang 《Ocean Engineering》1988,15(3)

Experimental studies of wave transmission by overtopping for a smooth impermeable breakwater with 1:1.5 slope under both regular and random waves were conducted. A resulting relationship between the transmission coefficient (determined by wave height and wave period) and a breakwater height above mean water level normalized with the height of wave run-up measured directly by capacity wave meter is reported. Meanwhile, their discrepancies in both regular and random waves are also discussed in this study. The authors find also that the transmitted significant wave period by overtopping of random waves may be much longer than those of the incoming wave. This characteristic is especially prominent and probably creates the oscillation phenomenon in the wave basin at the back of breakwater when the breakwater height (above mean water level) to water depth ratio is greater than 0.23 and the incoming wave period is longer than 8 sec.  相似文献   

Influence of wavelength on the parameterization of drag coefficient and surface roughness     

Paul A. Hwang 《Journal of Oceanography》2004,60(5):835-841

Surface waves are the roughness element of the ocean surface, the air-sea interaction processes are influenced by the wave conditions. The dynamic influence of surface waves decays exponentially with distance from the air-water interface. The relevant length scale characterizing the decay rate is the wavelength. The parameterization of drag coefficient and surface roughness can be significantly improved by using wavelength as the reference length scale of atmospheric measurements. The wavelength scaling of drag coefficient and dynamic roughness also receives support from theoretical studies of wind and wave coupling.  相似文献   

Incorporation of aged dissolved organic carbon (DOC) by oceanic particulate organic carbon (POC): An experimental approach using natural carbon isotopes   总被引：2，自引：2，他引：2  

Jeomshik Hwang  Ellen R.M. Druffel  James E. Bauer 《Marine Chemistry》2006,98(2-4):315-322

Incorporation of ¹⁴C-depleted (old) dissolved organic carbon (DOC) on/into particulate organic carbon (POC) has been suggested as a possible mechanism to explain the low Δ¹⁴C-POC values observed in the deep ocean [Druffel, E.R.M., Williams, P.M., 1990. Identification of a deep marine source of particulate organic carbon using bomb ¹⁴C. Nature, 347, 172–174.]. A shipboard incubation experiment was performed in the Sargasso Sea to test this hypothesis. Finely ground dried plankton was incubated in seawater samples from the deep Sargasso Sea, both with and without a biological poison (HgCl₂). Changes in parameters such as biochemical composition and carbon isotopic signatures of bulk POC and its organic compound classes were examined to study the roles of sorptive processes and biotic activity on POC character. Following a 13-day incubation, the relative abundance of the acid-insoluble organic fraction increased. Abundances of extractable lipids and total hydrolyzable amino acids decreased for both treatments, but by a greater extent in the non-poisoned treatment. The Δ¹⁴C values of POC recovered from the non-poisoned treatment were significantly lower than the value of the unaltered plankton material used for the incubation, indicating incorporation of ¹⁴C-depleted carbon, most likely DOC. The old carbon was present only in the lipid and acid-insoluble fractions. These results are consistent with previous findings of old carbon dominating the same organic fractions of sinking POC from the deep Northeast Pacific [Hwang, J., Druffel, E.R.M., 2003. Lipid-like material as the source of the uncharacterized organic carbon in the ocean? Science, 299, 881–884.]. However, the Δ¹⁴C values of POC recovered from the poisoned treatment did not change as much as those from the non-poisoned treatment suggesting that biological processes were involved in the incorporation of DOC on/into POC.  相似文献   

Effect of phenol on embryo development and expression of metallothionein in the sea urchin Hemicentrotus pulcherrimus     

Un-Ki Hwang  Ju-Wook Lee  Hyang-Mi Ryu  Ju-Chan Kang  Han Seung Kang 《Ocean Science Journal》2015,50(4):701-708

In this study, we identified and cloned the sea urchin Hemicentrotus pulcherrimus MT (Hp-MT) mRNA. We examined the gameto- and embryo-toxic effects and the expression of Hp-MT mRNA at various concentrations of phenol in H. pulcherrimus. We found that the normal embryogenesis rate was significantly inhibited when H. pulcherrimus was exposed to phenol (EC₅₀ = 1565.86 ppb, 95% Cl = 1183.47-2037.84 ppb). The no observed effective concentration (NOEC) and the lowest observed effective concentration (LOEC) of the normal embryogenesis rate were < 10 ppb and 100 ppb, respectively. Hp-MT cDNA is 651 bp in length and encodes a protein of 64 amino acids. We found that the expression of Hp-MT mRNA was significantly increased with phenol treatment in a concentrationdependent manner. These results suggest that phenol at greater than 100 ppb has a toxic effect during the early embryonic stages of H. pulcherrimus, and MT mRNA may be used as a biomarker for risk assessment of phenol contamination.  相似文献