V-2 Study on the system simulation for an O.W.C. type wave energy absorber     

Takeshi Kinoshita  Koichi Masuda  Shogo Miyajima  Wataru Kato 《Ocean Engineering》1985,12(6):580-581

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Mechanisms of rapid cooling in underwater welding     

Chon-Liang Tsai  Koichi Masubuchi 《Applied Ocean Research》1979,1(2):99-110

Two inherent problems, rapid cooling and hydrogen embrittlement, associated with underwater ‘wet’ welding remain unsolved at the present time. Weld defects induced by rapid cooling usually appear in underwater welds. An understanding of the basic mechanisms is probably important and necessary in order to establish solutions to the problems of rapid cooling. Three types of weld defects related to rapid cooling during underwater welding are presented. A discussion on the thermal behaviour of underwater welding is then introduced. This discussion covers some important thermal-physical areas which control the cooling rate during underwater welding. It includes underwater bubble dynamics, underwater arc-heat distribution, Joule heating, heat input mechanism and boundary heat loss mechanism. Several important new concepts of reducing the effect of rapid cooling during underwater welding are finally recommended.  相似文献   

Intrusion of less saline shelf water into the Kuroshio subsurface layer in the East China Sea   总被引：7，自引：0，他引：7  

Atsuhiko?IsobeEmail author  Eiji?Fujiwara  Pil-Hun?Chang  Koichi?Sugimatsu  Manabu?Shimizu  Takeshi?Matsuno  Atsuyoshi?Manda 《Journal of Oceanography》2004,60(5):853-863

The possible origin and cause of the less saline shelf water detected in the Kuroshio subsurface layer around the shelf edge of the East China Sea are investigated using observational results obtained in May 1998–2001 in conjunction with a dataset archived by Japan Oceanographic Data Center and a numerical model. The observations show that subsurface intrusions of less saline water are always detected in May in layers above 24.5σθ isopycnal surface, and that salinity inversions (i.e., areas in which the less saline water lies beneath the saline water) are detected around the trough of the Kuroshio frontal eddy (or wave). Analyses of the archived dataset reveal that the isopycnal surface of 24.5σθ is the deepest layer of the Kuroshio pycnocline outcropping to the sea surface on the shallow shelf in early spring. Outcropping isopycnals above 24.5σθ encounter a less saline water plume originating from the Changjiang, especially in the western East China Sea. Thereafter, the less saline water moves along isopycnal layers and reaches the Kuroshio front around the shelf edge. Numerical models demonstrate that, when the frontal wave captures the less saline water, the shelf water takes the form of a salinity inversion in the trough because isohalines in the frontal wave have a phase lag between the upper and lower layers in consequence of the baroclinic instability.  相似文献   

Terrestrial heat flow in the Celebes and Sulu Seas     

Koichi Nagasaka  Jean Francheteau  Toshio Kishii 《Marine Geophysical Researches》1970,1(1):99-103

Five heat flow measurements were made in the Asiatic Mediterranean Sea; two in the Celebes Sea and three in the Sulu Sea. The mean of all five values of 2.0 cal/cm² sec is significantly greater than the over-all mean heat flow value for the oceans and is close to the mean value for marginal seas. The measurement indicate that there may be a difference in the flow of heat through the two seas.Contribution of the Scripps Institution of Oceanography, new series.  相似文献   

Deposition rates of polysilicic acid with up to 10 M calcium ions     

Taiji Chida  Yuichi Niibori  Osamu Tochiyama  Hitoshi Mimura  Koichi Tanaka 《Applied Geochemistry》2007,22(12):2810-2816

Cementitious materials used for radioactive waste repository construction complicate the performance assessment of radioactive waste systems because the use of cement may greatly alter the pH (8–13) of groundwater and release constituents such as calcium ions. Under such conditions, it is important to clarify also the dynamic behavior of silica (silicic acid), in order to evaluate the alteration in the chemical and physical properties of the fractured layer or the host rock surrounding the repository. Since silica undergoes polymerization, precipitation or dissolution depending on the pH and/or temperature, the behavior of silica would be greatly complicated in the presence of other ions. This study is focused on the deposition rates of polysilicic acid and soluble silicic acid with up to 10⁻³ M Ca ions. In the experiment, Na₂SiO₃ solution (250 mL, pH > 10, 298 K) was poured into a polyethylene vessel containing amorphous silica powder (0.5 g), and a buffer solution, HNO₃, and CaNO₃ as Ca ions were sequentially added into the vessel. The pH of the solution was set to 8. The silica, initially in a soluble form at pH > 10 (1.4 × 10⁻² M), became supersaturated and either deposited on the solid surface or changed into the polymeric form. Then the concentrations of both poly- and soluble silicic acid were monitored over a 40-day period. The decrease of polysilicic acid became slow with an increase in the concentration of Ca ions in the range of up to 10⁻³ M. In general, the addition of electrolytes to a supersaturated solution accelerates the aggregation and precipitation of polymeric species. However, the experimental result showed that polysilicic acid in the presence of Ca ions is apparently stable in solution, compared with that under a Ca-free condition. On the other hand, the concentration of soluble silicic acid in the presence of Ca ions immediately became metastable, that is, slightly higher than the solubility of soluble silicic acid. Its dynamic behavior was similar to that in the Ca-free condition.  相似文献   

Effect of depositional processes on the origin and composition of organic matter: Examples from the Pleistocene sediments in the Choshi core, Boso Peninsula     

Akiko  Omura  Koichi  Hoyanagi  Satoko  Ishikawa 《Island Arc》2006,15(3):355-365

Abstract   Both marine and terrigenous organic matter are deposited in shelf and continental slope environments. In the present study, the relationship between environmental changes in the Choshi area and the sedimentation of organic matter was examined. The sediments of the Choshi core were deposited on a shelf environment and their lithology and ichnofacies, as well as the composition of the contained kerogen (insoluble organic matter) indicate a shallowing upward succession. The organic matter preserved in the sediments is of both marine and terrigenous origin, on the basis of C/N ratios (5.90–9.45), δ¹³C values (−21.6‰−24.6‰) and kerogen microscopy. The total organic carbon (TOC) content (0.39–1.08%) of the sediments shows a positive correlation with the increase of terrigenous organic matter before 500 ka, but decreases (0.26–0.61%) after 500 ka as the shelf environment becomes shallower because of dilution, caused by the input of terrigenous inorganic clasts, and oxidation. The variation in TOC contents was thus influenced by the increasing sedimentation rate of terrigenous materials, including both organic and inorganic particles as the basin filled.  相似文献   

Analysis of temporal and spatial heterogeneity of magnitude frequency distribution inferred from earthquake catalogues   总被引：11，自引：0，他引：11  

Yosihiko Ogata  Koichi Katsura 《Geophysical Journal International》1993,113(3):727-738

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Hg, Zn and Cu levels in the muscle and liver of tiger sharks (Galeocerdo cuvier) from the coast of Ishigaki Island, Japan: relationship between metal concentrations and body length     

Endo T  Hisamichi Y  Haraguchi K  Kato Y  Ohta C  Koga N 《Marine pollution bulletin》2008,56(10):1774-1780

We analyzed Hg, Zn and Cu concentrations in the liver and muscle of tiger sharks (Galeocerdo cuvier) from the coast of Ishigaki Island, Japan. The Hg concentration in the muscle increased proportionally with body length in the tiger sharks, whereas that in the liver increased rapidly after maturity (defined by a length of over 2.7 m). Muscle Hg levels were higher than liver concentrations in immature sharks, with the inverse trend observed in mature sharks. Notably, the Zn and Cu concentrations in the liver tended to decrease with increasing body length. This rapid increase in hepatic Hg concentration concurrent with the onset of maturity in sharks may result from the continuous intake of Hg via food and the slower growth of mature sharks. The high concentrations of the essential metals Zn and Cu in immature sharks may be explained by the physiological demands related to rapid growth.  相似文献   

拉萨上空大气气溶胶光学特性的 激光雷达探测   总被引：24，自引：4，他引：20  

白宇波  石广玉  田村耕一  岩坂泰信 《大气科学》2000,24(4):559-567

叙述了大气气溶胶激光雷达探测方程的求解方法,以及1998年夏季在拉萨使用激光雷达观测的一些结果,并与日本名古屋市上空的探测资料进行了对比分析,得到了拉萨上空气溶胶光学性质的一般特征,并对其成因进行了讨论。  相似文献   

Spatial periodicity of galaxy number counts, CMB anisotropy, and SNIa Hubble diagram based on the universe accompanied by a non-minimally coupled scalar field     

Koichi Hirano  Kiyoshi Kawabata  Zen Komiya 《Astrophysics and Space Science》2008,315(1-4):53-72

We have succeeded in establishing a cosmological model with a non-minimally coupled scalar field φ that can account not only for the spatial periodicity or the picket-fence structure exhibited by the galaxy N-z relation of the 2dF survey but also for the spatial power spectrum of the cosmic microwave background radiation (CMB) temperature anisotropy observed by the WMAP satellite. The Hubble diagram of our model also compares well with the observation of Type Ia supernovae. The scalar field of our model universe starts from an extremely small value at around the nucleosynthesis epoch, remains in that state for sufficiently long periods, allowing sufficient time for the CMB temperature anisotropy to form, and then starts to grow in magnitude at the redshift z of ～1, followed by a damping oscillation which is required to reproduce the observed picket-fence structure of the N-z relation. To realize such behavior of the scalar field, we have found it necessary to introduce a new form of potential V(φ)∝ φ ²exp?(?q φ ²), with q being a constant. Through this parameter q, we can control the epoch at which the scalar field starts growing.  相似文献