Experimental Study Assessing the Role of Sedimentary Organic Materials to Control the Redox State of Ground Materials to Control the Redox State of Groundwater: Consumption of Dissolved Oxygen by Humic Acid     

Ken-ichiro Haysahi    Hideyuki Shibata    Mikazu Yui  Hiroshi Ohmoto 《Resource Geology》2001,51(1):45-54

Abstract: A total of 189 runs were completed to determine the rate of dissolved oxygen consumption in water by the reaction humic acid at 25°, 45°, and 65°C. Glass vial bottles were used as reaction vessels, and humic aicd and pure water of different intitial O₂ concentration was loaded with humic acid/water weight of 0.008 and 0.009. Vials were opened periodically to measure O₂ concentrations. The pH of the solution fluctuated in the early stages of the experiments and gradually decreased to a constant value. Dissolved oxygen concentration decreased, for example, from initial value of 12 mg/l to 9 mg/l at 25°C, to 5 mg/l at 45°C, and to 2 mg/l at 65°C after the reaction of 500 hours. Analyses of rates suggest that the reaction is first order, and rate constants are 8.42 × 10^-9 at 25°C, 2.22 × 10^-8 at 45°C, and 1.28 × 10^-7 moles m^-2 s^-1 at 65°C.  相似文献   

Comparison of hydroelastic computer codes based on the ISSC VLFS benchmark     

H.R. Riggs  Hideyuki Suzuki  Jang Whan Kim 《Ocean Engineering》2008,35(7):589-597

There has been substantial development in computer codes for linear hydroelasticity in recent years, driven in part by the motivation to investigate the wave-induced response of very large floating structures (VLFSs). A recent International Ship and Offshore Structures Congress (ISSC) state-of-the-art report on VLFS design and analysis [ISSC, 2006. Report of Specialist Task Committee VI.2, very large floating structures. In: Frieze, P.A., Shenoi, R.A. (eds.), Proceedings of the 16th International Ship and Offshore Structures Congress, Elsevier, Southampton, UK, pp. 397-451] included a brief comparative study of the simulation results from different computer codes for a pontoon (mat-like) VLFS. The codes covered a mix of both fluid models (potential and linear Green-Naghdi) and structural models (3-D grillage, 2-D plate, 3-D shell). A more detailed comparison of the results from a select group of models from that study is provided and discussed herein. The similarities in the results increase the confidence level of the state-of-the-art in predicting the hydroelastic response of such structures, and the differences, including in computational efficiency, lead to an understanding of the significance of specific modeling assumptions and their impact on the predicted response.  相似文献   

Formation rate of water masses in the Japan sea     

Hideyuki Kawamura  Jong-Hwan Yoon  Toshimichi Ito 《Journal of Oceanography》2007,63(2):243-253

Water masses in the subsurface and the intermediate layer are actively formed due to strong winter convection in the Japan Sea. It is probable that some fraction of pollution is carried into the layer below the sea surface together with these water masses, so it is important to estimate the formation rate and turnover time of water masses to study the fate of pollutants. The present study estimates the annual formation rate and the turnover time of water masses using a three-dimensional ocean circulation model and a particle chasing method. The total annual formation rate of water masses below the sea surface amounted to about 3.53 ± 0.55 Sv in the Japan Sea. Regarding representative intermediate water masses, the annual formation rate of the Upper portion of the Japan Sea Proper Water (UJSPW) and the Japan Sea Intermediate Water (JSIW) were estimated to be about 0.38 ± 0.11 and 1.43 ± 0.16 Sv, respectively, although there was little evidence of the formation of deeper water masses below a depth of about 1500 m in a numerical experiment. An estimate of turnover time shows that the UJSPW and the JSIW circulate in the intermediate layer of the Japan Sea with timescales of about 22.1 and 2.2 years, respectively.  相似文献   

Development of an operational coastal model of the Seto Inland Sea,Japan     

Kei Sakamoto  Goro Yamanaka  Hiroyuki Tsujino  Hideyuki Nakano  Shogo Urakawa  Norihisa Usui  Mikitoshi Hirabara  Koji Ogawa 《Ocean Dynamics》2016,66(1):77-97

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On the semiconvective zone in the core-helium-burning stars     

Hideyuki Saio 《Astrophysics and Space Science》1974,29(1):41-49

The validity of current ideas to set up the semiconvective zone of the stellar models in corehelium-burning phase has been considered mainly from the view point of times-cales related to the mechanism. The time-scale of outward motion of convective shell has been estimated as being longer than that of evolution. From this point of view, it might be said that the models constructed with semiconvective zone are not appropriate for the core-helium-burning stars.  相似文献   

Lithium depletion in G and K dwarfs     

Minoru Umezu  Hideyuki Saio 《Monthly notices of the Royal Astronomical Society》2000,316(2):307-314

We present deep wide-field (16.4×16.4 arcmin²) Washington CT ₁ CCD surface photometry of the giant elliptical galaxy NGC 4472, the brightest member of the Virgo cluster. Our data cover a wider and deeper field than any previous CCD photometry. A single King model does not give a good fit to the surface brightness profiles of NGC 4472, but they can be fitted approximately using two King models: with the separate models representing the inner and outer regions . Surface brightness profiles for the outer region can also be fitted approximately by a de Vaucouleurs law. There is clearly a negative colour gradient within 3 arcmin of NGC 4472, in the sense that the colour gets bluer with increasing radius. The slope of the colour gradient for this region is derived to be Δ μ ( C − T ₁)=−0.08 mag arcsec⁻² for Δ log  r =1, which corresponds to a metallicity gradient of Δ[Fe/H]=−0.2 dex. However, the surface colour becomes gradually redder with increasing radius beyond 3 arcmin. A comparison of the structural parameters of NGC 4472 in C and T ₁ images has shown that there is little difference in the shapes of ellipses observed using isochromes or isophotes. In addition, photometric and structural parameters of NGC 4472 have been determined.  相似文献   

The evolution of a rapidly accreting helium white dwarf to become a low-luminosity helium star     

Hideyuki Saio  C. Simon Jeffery 《Monthly notices of the Royal Astronomical Society》2000,313(4):671-677

We have examined the evolution of merged low-mass double white dwarfs which become low-luminosity (or high-gravity) extreme helium stars. We have approximated the merging process by the rapid accretion of matter, consisting mostly of helium, on to a helium white dwarf. After a certain mass is accumulated, a helium shell flash occurs, the radius and luminosity increase and the star becomes a yellow giant. Mass accretion is stopped artificially when the total mass reaches a pre-determined value. As the helium-burning shell moves inwards with repeating shell flashes, the effective temperature gradually increases as the star evolves towards the helium main sequence. When the mass interior to the helium‐burning shell is approximately 0.25 M_⊙, the star enters a regime where it is pulsationally unstable. We have obtained radial pulsation periods for these models.
These models have properties very similar to those of the pulsating helium star V652 Her. We have compared the rate of period change of the theoretical models with that observed in V652 Her, as well as with its position on the Hertzsprung–Russell diagram. We conclude that the merger between two helium white dwarfs can produce a star with properties remarkably similar to those observed in at least one extreme helium star, and is a viable model for their evolutionary origin. Such helium stars will evolve to become hot subdwarfs close to the helium main sequence. We also discuss the number of low-luminosity helium stars in the Galaxy expected for our evolution scenario.  相似文献   

Development of a new operational system for monitoring and forecasting coastal and open-ocean states around Japan     

Hirose  Nariaki  Usui  Norihisa  Sakamoto  Kei  Tsujino  Hiroyuki  Yamanaka  Goro  Nakano  Hideyuki  Urakawa  Shogo  Toyoda  Takahiro  Fujii  Yosuke  Kohno  Nadao 《Ocean Dynamics》2019,69(11):1333-1357

We developed a new system to monitor and forecast coastal and open-ocean states around Japan for operational use by the Japan Meteorological Agency. The system consists of an eddy-resolving analysis model based on four-dimensional variational assimilation and a high (2-km) resolution forecast model covering Japanese coastal areas that incorporates an initialization scheme with temporal and spatial filtering. Assimilation and forecast experiments were performed for 2008 to 2017, and the results were validated against various observation datasets. The assimilation results captured well the observed variability in sea surface temperature, coastal sea level, volume transport, and sea ice. Furthermore, the volume budget for the Japan Sea was significantly improved by the use of the 2-km resolution forecast model compared with the 10-km resolution analysis model. The forecast results indicate that this system has a predictive limit longer than 1 month in many areas, including in the Kuroshio current area south of Japan and the southern Japan Sea. In the forecast results of case studies, the 2017 Kuroshio large meander was well predicted, and warm water intrusions accompanying Kuroshio path variations south of Japan were also successfully reproduced. Sea ice forecasts for the Sea of Okhotsk largely captured the evolution of sea ice in late winter, but sea ice in early winter included relatively large errors. This system has high potential to meet operational requirements for monitoring and forecasting ocean phenomena at both meso- and coastal scales.

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Age gap between the intrusion of gneissose granitoids and regional high‐temperature metamorphism in the Ryoke belt (Mikawa area), central Japan          下载免费PDF全文

Kota Takatsuka  Tetsuo Kawakami  Etienne Skrzypek  Shuhei Sakata  Hideyuki Obayashi  Takafumi Hirata 《Island Arc》2018,27(1)

The relationships between the intrusion of gneissose granitoids and the attainment of regional high‐T conditions recorded in metamorphic rocks from the Ryoke belt of the Mikawa area, central Japan, are explored. Seven gneissose granitoid samples (tonalite, granodiorite, granite) were collected from three distinct plutonic bodies that are mapped as the so‐called “Older Ryoke granitoids.” Based on bulk‐rock compositions and U–Pb zircon ages obtained by laser ablation inductively coupled plasma mass spectrometry, the analyzed granitoids can be separated into two groups. Gneissose granitoids from the northern part of the area give weighted mean ²⁰⁶Pb/²³⁸U ages of 99 ±1 Ma (two samples) and 95 ±1 Ma (one sample), whereas those from the southern part yield 81 ±1 Ma (two samples) and 78–77 ±1 Ma (two samples). Regional comparisons allow correlation of the northern granitoids (99–95 Ma) with the Kiyosaki granodiorite, and mostly with the Kamihara tonalite found to the east. The southern granitoids are tentatively renamed as “78–75 Ma (Hbl)?Bt granite” and “81–75 Ma Hbl?Bt tonalite” (Hbl, hornblende; Bt, biotite). and seem to be broadly coeval members of the same magmatic suite. With respect to available age data, no gneissose granitoid from the Mikawa area shows a U–Pb zircon age which matches that of high‐T metamorphism (ca 87 Ma). The southern gneissose granitoids (81–75 Ma), although they occur in the highest‐grade metamorphic zone, do not seem to represent the heat source which produced the metamorphic field gradient with a low dP/dT slope.  相似文献