Two dimensional responses of fixed offshore platform in waves     

Toru Sawaragi  Masao Nochino 《Applied Ocean Research》1985,7(3):140-151

Responses of a four-legged offshore platform to wave forces are analysed by taking account of one torsional motion around the vertical axis which passes the centre of gravity of the structure, and two translational motions in the horizontal plane. Applying the spring-mass system with one degree-of-freedom to each mode of motion, a calculation method for predicting resultant dynamic displacements of the topdeck is developed. Both the inline force and the transverse force are considered as external forces. The calculated results are found to agree with experiments. Furthermore, the influence of seven important factors on the dynamic response is examined by the calculations. It is shown that the combination pattern of the direction factor of the transverse force is of importance in dynamic analysis.  相似文献   

Observation of the Kyucho in the Bungo Channel by HF radar     

Hidetaka Takeoka  Yoshio Tanaka  Yuichi Ohno  Yukiharu Hisaki  Akitsugu Nadai  Hiroshi Kuroiwa 《Journal of Oceanography》1995,51(6):699-711

Observations of sea surface currents by HF radar were carried out in the Bungo Channel in summer 1992. The current ellipses of M₂ constituent obtained by the observational results agree quite well with those obtained by the ADCP observations, showing that the accuracy of the HF radar measurements is of the same level as ADCP. The results revealed the current structures and their change with the Kyucho in detail. The Kyucho is influenced by the complicated coastal geometry and does not propagate straightly into the Bungo Channel. It propagates further inward after charging the coastal bays with warm water. The current directions change largely, since the currents turn around the stagnant region in the bay filled with the warm water. The northward intrusion begins to be weakened in the southern part of the channel, while it still persists in the northern part. The northward current speeds of the observed Kyucho are about 50 cm/s and sometimes attain 60 to 70 cm/s.  相似文献   

Geostrophy in the Intermediate and Deep Layers of the Kuroshio and Its Recirculation Regions South of Japan     

Motohiko Kashima  Shiro Imawaki  Shin-Ichiro Umatani  Hiroshi Uchida  Yuji Hashibe  Hiroshi Ichikawa  Masao Fukasawa 《Journal of Oceanography》2003,59(3):291-301

Theoretically, the geostrophic approximation holds for the low-frequency flow field, but no detailed examination has been done on how well the estimated geostrophic velocity corresponds with the observed velocity. Intensive surveys were carried out during 1993–1995 in the Kuroshio and its recirculation regions south of Shikoku, Japan, including repeated hydrographic surveys and direct current measurements at nominal depths of 700, 1500 and 3000 m. For these depth intervals, vertical differences of estimated geostrophic velocity are compared with those of observed velocity. For the intermediate layer (between 700 and 1500 m depths), the slope of the regression line is 0.99, correlation coefficient is 0.98, and the root-mean-square of difference from geostrophic balance is 2.8 cm/s which is close to the estimated error of 2.1 cm/s. For the deep layer (between 1500 and 3000 m depths), the corresponding values are 0.82, 0.93, 1.2 cm/s and 2.0 cm/s, respectively. The results indicate that the estimated geostrophic velocity compares well with the observed velocity in these regions. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Set-up of deep circulation in multi-level numerical models     

Nobuo Suginohara  Masao Fukasawa 《Journal of Oceanography》1988,44(6):315-336

The present study investigates the way an ocean filled with homogeneous warm water is cooled by prescribing cold water formation inside the ocean in the southern part of the southern hemisphere using multi-level numerical models. Cooling of the whole ocean starts with introduction of the cold water from the formation region into the deepest part of the ocean in the equatorial and eastern boundary regions by Kelvin wave-type density currents. The cold water along the eastern boundary extends westward as a Rossby wave-type density current setting up an interior poleward flow, and hits the western boundary to form a northward flowing boundary current in the northern hemisphere. Only then does the western boundary current cross the equator. Cooling of the rest of the ocean basin is accomplished by upwellings in the interior and also along the coasts. During this introduction the cold water is mixed with surrounding warm waters, and the thermocline, rather than forming just below the top level where heating is imposed, tends to spread down to deeper depths. Consequently the circulation at a steady state has a significant vertical structure such that the maximum upwelling in the interior occurs in the mid-depths, and only the deeper part of the deep ocean yields the Stommel and Arons circulation pattern. In the equatorial region higher vertical mode motions dominate, and a set of alternating zonal jets forms along the equator.  相似文献   

辽东地区沉积变质硼矿床及硼同位素研究   总被引：2，自引：2，他引：2  

肖荣阁  大井隆夫  费红彩  野村雅夫 《现代地质》2003,17(2):137-142

辽东地区元古界硼矿床属于沉积变质硼矿。根据现代盐湖沉积 ,认为硼矿物沉积通常为硼砂 ,然后在区域变质作用过程中 ,硼砂矿物转变为硼镁矿物或硼铁矿等硼酸盐矿物 ,但辽东硼矿床中不同硼矿物的硼同位素有一定差别。电气石富10 B ,δ11B值较低或呈负值 ;而硼镁石与硼镁铁矿类矿物明显富集11B ,δ11B值较高 ,为 +2 3‰～ +17 4‰。根据水岩作用过程中硼同位素分馏特征的研究 ,11B与10 B比较有下列 4个特征 :( 1) 11B属于极不相容元素 ,优先进入水相 ,因此在变质残余矿物相中形成低的δ11B值 ;( 2 )在蚀变和交代变质反应中硅优先替代11B进入矿物晶格 ,因此在硅化交代中可以降低δ11B值 ,而脱硅反应中可以提高δ11B值 ;水化作用中 ,OH-带入11B ,使富水矿物具有较高的δ11B值 ;( 3)热水沉积及热液交代成因电气石均具有较低的δ11B值或者为负值 ;( 4)通过最近的研究表明 ,在热蒸馏过程中 ,硼同位素会发生明显的分馏 ,11B倾向于进入蒸汽相 ,而使残余相或后蒸馏相亏损11B ,形成较低的δ11B值。因此可以认为辽东地区元古界硼矿床属于热水沉积电气石岩在后期区域变质或热变质过程中分解出硼酸气水溶液交代镁碳酸盐形成硼镁石或硼镁铁矿矿物 ,而非蒸发沉积变质矿床。  相似文献   

Characteristics of alkenones synthesized by a bloom of emiliania huxleyi in the Bering Sea     

Naomi Harada  Kyung Hoon Shin  Masao Uchida 《Geochimica et cosmochimica acta》2003,67(8):1507-1519

We investigated the characteristics of the alkenones produced by a bloom of Emiliania huxleyi in the eastern Bering Sea in 2000. Alkenones were detected in surface waters between 57°N and 63°N, where phosphate concentrations were low and the ammonium/nitrate ratio was high. The total alkenone content (C_37:2, C_37:3, and C_37:4) ranged from 22.0 to 349 μg g⁻¹ in suspended particles and from 0.109 to 1.42 μg g⁻¹ in surface sediments. This suggests that a large proportion of the particulate alkenones synthesized in the surface water rapidly degraded within the water column and/or at the water-sediment interface of the Bering Shelf. The change in the stable carbon isotopic composition (δ¹³C) of C_37:3 alkenone could not be explained only by variation in [CO₂(aq)] in the surface water but also depended on the growth rate of E. huxleyi. The alkenone unsaturation index (U^K′₃₇) was converted into an alkenone “temperature” with three equations [Prahl et al 1988], [Sikes et al 1997] and [Müller et al 1998]; Sikes et al.’s (1997) equation gave the best correlation with the observed sea surface temperature (SST) in the eastern Bering Sea. However, some temperatures estimated by Sikes et al.’s (1997) equation from the U^K′₃₇ varied from the observed SST, possibly because of the rapidly changing rate of alkenone synthesis in the logarithmic growth stage or the low rate of alkenone synthesis when nutrients were limiting. Temperatures estimated from U^K′₃₇ in the surface sediments (6.8-8.2°C) matched the observed SST in September (7-8°C) but differed from the annual average SST of 4 to 5°C, suggesting that most of the alkenone in the eastern Bering Sea was synthesized during limited periods, for instance, in September. The relative amounts of C_37:4 alkenone as proportions of the total alkenones (referred to as C_37:4%) were high, ranging from 18.3 to 41.4%. Low-salinity water (<32 psu) within the study area would have contributed to the high C_37:4% because a negative linear relationship between C_37:4% and salinity was found in this study.  相似文献   

Perturbations of the Earth's rotation and their implications for the present-day mass balance of both polar ice caps     

Masao Nakada  Jun'ichi Okuno 《Geophysical Journal International》2003,152(1):124-138

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Trace elements in skin of Dall's porpoises (Phocoenoides dalli) from the northern waters of Japan: an evaluation for utilization as non-lethal tracers     

Jian Yang  Takashi Kunito  Shinsuke Tanabe  Masao Amano  Nobuyuki Miyazaki 《Marine pollution bulletin》2002,45(1-12)

Concentrations of Fe, Zn, Cu, Se, Mn, Mo, Hg, Cd, Cr, Ag, Pb, Sr and V were determined in skins of Dall's porpoises (Phocoenoides dalli) of the Pacific coast truei-type population (PT population) (N=45), and the Sea of Japan-Okhotsk dalli-type population (JD population) (N=31) from the northern waters of Japan. Cutaneous Hg concentrations in both PT and JD populations were significantly correlated with age, indicating a possible alternative method of age estimation. A significant correlation was also noted between Hg concentrations in skin and liver, suggesting that biopsy samples of skin can provide a non-lethal surrogate for monitoring Hg contamination in this species. Trace element accumulation patterns differed strongly between PT and JD populations, when analyzed by principal component analysis, suggesting these patterns could be utilized as non-lethal tracers of population identification.  相似文献   

Boron isotopic composition of fumarolic condensates and sassolites from Satsuma Iwo-jima,Japan   总被引：1，自引：0，他引：1  

Tadao Kanzaki  Minoru Yoshida  Masao Nomura  Hidetake Kakihana  Takejiro Ozawa 《Geochimica et cosmochimica acta》1979,43(11):1859-1863

¹¹B/¹⁰B ratios of the high temperature fumarolic gases (>465°C) of this island were found to be constant within the limits of experimental error (¹¹B/¹⁰B = 4.066). This value may represent the ¹¹B/¹⁰B ratio of boron in the andesite magma. ¹¹B/¹⁰B ratios of the low temperature fumarolic gases (<235°C) were found to vary from 4.053 to 4.077. ¹¹B/¹⁰B ratios of some sassolites were approximately equal to that of the fumarolic condensates and the other ones were slightly enriched in ¹⁰B compared to the fumarolic condensates.  相似文献   

Distribution of titanium atoms in oxy-kaersutite     

Masao Kitamura  Masayasu Tokonami  Nobuo Morimoto 《Contributions to Mineralogy and Petrology》1975,51(3):167-172

The distribution of Ti atoms in oxy-kaersutite has been studied by the neutron diffraction method. The cation distribution over the three octahedral sites determined by the x-ray method (Kitamura and Tokonami, 1971) is as follows; M1∶0.40MG+0.60 FE, M2∶0.75 MG+0.25 FE, M3∶0.50 MG+0.50 FE, where MG and FE represent (Mg+Al) and (Fe+Ti), respectively. The neutron diffraction study indicates that Ti atoms are enriched in the M1 site more than M2 and M3 sites as follows; M1∶0.40 MG+0.33 Fe+0.27 Ti, M2∶ 0.75 MG+0.23 Fe+0.02 Ti, M3∶0.50 MG+0.46 Fe+0.04 Ti. This distribution agrees with the result based on the Madelung energy of oxy-kaersutite by Whittaker (1972).  相似文献