An estimation of the average lifetime of the latest model of APEX floats     

Taiyo Kobayashi  Brian A. King  Nobuyuki Shikama 《Journal of Oceanography》2009,65(1):81-89

Estimating the average lifetime of floats is very important for Argo, because the total cost of maintaining the monitoring network largely depends on float lifetime. However, the actual lifetime of floats used in Argo is currently unknown. An estimate can be made by examining past float survival, but this is complicated by floats still operating at sea and continuous improvements in float hardware. Because APEX (Autonomous Profiling Explorer) floats are the most widely deployed type of float in the world oceans, in this study we estimate the lifetime of the latest model of APEX powered by alkaline batteries. The expected lifetime is estimated with a statistical method that allows for floats that are still active and that failed because of a known and now fixed hardware fault that should not cause failure in the latest model of floats. As an example, we analyzed the APEX fleets managed by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), because we have access to a JAMSTEC database in which the causes of float failure have been carefully correlated to known hardware problems. Analysis of the JAMSTEC fleet (n = 571, as of 7 May 2008) indicated that the expected lifetime of the latest model of APEX is 134.6 (127.6–141.5, considering standard errors) cycles, equivalent to 3.7 years of 10-day cycles. We conclude that the annual deployment of 813 (773–859) APEX floats is needed to maintain the Argo observational network of 3000 floats. Floats with different hardware configurations (e.g., lithium batteries) or different mission programs (e.g., shallower profiling, deeper profiling every several cycles) may be expected to have an even longer lifetime.  相似文献   

Long-term variability of shelf water intrusion and its influence on hydrographic and biogeochemical properties of the Seto Inland Sea, Japan   总被引：1，自引：0，他引：1  

Shiho Kobayashi  Tateki Fujiwara 《Journal of Oceanography》2008,64(4):595-603

The variability of the pathway of the Kuroshio is known to control that of the intensity of upwelling of the cold and nutrient-rich deep shelf water at the shelf-break point. This study has investigated the influences of the long-term variability of the hydrographical and biogeochemical conditions at the shelf-break point on those in the inner Seto Inland Sea. Results from observations conducted since 1972 by prefectural fisheries observatories showed a temporary decrease of temperature in the lower layer of the entrance of Kii Channel in summertime in the specific years when the Kuroshio pathway favored deep shelf water intrusion. A corresponding change in temperature was also found in the inner shelf sea, such as western Osaka Bay and Harima-Nada. The model developed in this study covers a 30-year period and well reproduces the temporal change in temperature. It also shows sufficient reproducibility in both seasonal behavior of hydrographical and biogeochemical properties and the inter-annual variability of hydrographical properties throughout the eastern Seto Inland Sea. It was found that the inter-annual variations of annual total flux through the section at the entrance to Kii Channel affect the inter-annual variation of the observed concentration of Dissolved Inorganic Nitrogen (DIN) in Harima Nada, but the effect was smaller than those of river input and other parameters.  相似文献   

Processes influencing iron distribution in the coastal waters of the Tsugaru Strait,Japan     

Yukiyo Saitoh  Kenshi Kuma  Yutaka Isoda  Hiroshi Kuroda  Hiromi Matsuura  Taku Wagawa  Hyoe Takata  Naoto Kobayashi  Seiya Nagao  Takeshi Nakatsuka 《Journal of Oceanography》2008,64(6):815-830

We report measurements of iron, nutrients, dissolved oxygen, humic-type fluorescence intensity and chlorophyll a concentrations in the coastal waters at the inflow (western) and outflow (eastern) ends of Tsugaru Strait (Japan) in June 2003 and 2004. Two different water masses (intensive eastward flow “subtropical Tsugaru Warm Current Water (TWCw)” and weak westward flow “subarctic Oyashio Water (OW)”) were observed at the eastern end of the strait. TWCw at the southern part of the eastern strait was vertically homogeneous with a uniform concentrations of iron (0.7–1.1 nM for labile dissolved Fe and 14–20 nM for total dissolvable Fe in 2003) as well as other chemical, biological and physical components throughout the water column of 200 m due to strong vertical mixing in the strait. The degree of mixing in the Tsugaru Warm Current (TWC) is predominantly affected by diurnal tidal current, which is strong during the period of tropical tides and weak during the period of equinoctial ones. The especially strong vertical water mixing in 2003 is caused by large dissipation energy input due to the bottom friction of passage-flow through the strait and tidal current. At the northern part of the eastern strait, the fresh surface layer overlying the OW and the deep-bottom waters in 2003 contained large concentrations of dissolved iron, resulting from iron supplied from river runoff and shelf sediments, respectively. These results suggest that the most important mechanism for transporting iron in the strait is the strong vertical water mixing due to the tidal current, and that the iron sources in the coastal waters are the organic-associated, iron-rich freshwater input into the surface water.  相似文献   

空间乳胶室探测器的研制     

胡一鸣  常进  宫一忠  张仁健  王楠森  唐和森  Torii S.  Nishimura J.  Kobayashi T.  Shimizu Y.  Makino F. 《天文学报》2008,49(2):233-242

"实践八号"乳胶室探测器是我国首次用于空间观测高能电子及伽玛射线的乳胶 室探测器.介绍"实践八号"乳胶室探测器的设计原理、数据分析方法、设计过程和初步 观测结果等."实践八号"乳胶室探测器空间观测时间为15天,可探测的粒子能量范围为 100GeV～5TeV.  相似文献   

An experimental study on impact-induced alterations of planetary organic simulants          下载免费PDF全文

Yasuhito Sekine  Kenya Kodama  Takamichi Kobayashi  Seiji Obata  Yu Chang  Nanako O. Ogawa  Yoshinori Takano  Naohiko Ohkouchi  Koichiro Saiki  Toshimori Sekine 《Meteoritics & planetary science》2018,53(6):1267-1282

The present study systematically investigates shock-induced alteration of organic simulants of planetary bodies (OSPBs) as a function of peak shock pressure and temperature by impact experiments. Our results show that the composition and structure of OSPBs are unchanged upon impacts at peak pressures ≤~5 GPa and temperatures ≤~350 °C. On the other hand, these are dramatically changed upon impacts at >7–8 GPa and > ~400 °C, through loss of hydrogen-related bonds and concurrent carbonization, regardless of the initial compositions of OSPBs. Compared with previous results on static heating of organic matter, we suggest that shock-induced alteration cannot be distinguished from static heating only by Raman and infrared spectroscopy. Our experimental results would provide a proxy indicator for assessing degree of shock-induced alteration of organic matter contained in carbonaceous chondrites. We suggest that a remote-sensing signature of the 3.3–3.6 μm absorption due to hydrogen-related bonds on the surface of small bodies would be a promising indicator for the presence of less-thermally-altered (i.e., <350 °C) organic matter there, which will be a target for landing to collect primordial samples in sample-return spacecraft missions, such as Hayabusa2 and OSIRIS-REx.  相似文献   

Shock-capturing Boussinesq-type model for nearshore wave processes     

Volker Roeber  Kwok Fai Cheung  Marcelo H. Kobayashi 《Coastal Engineering》2010

This paper describes the formulation and validation of a nearshore wave model for tropical coastal environment. The governing Boussinesq-type equations include the conservative form of the nonlinear shallow-water equations for shock capturing. A Riemann solver supplies the inter-cell flux and bathymetry source term, while a Godunov-type scheme integrates the evolution variables in time. The model handles wave breaking through momentum conservation with energy dissipation based on an eddy viscosity concept. The computed results show very good agreement with laboratory data for wave propagation over a submerged bar, wave breaking and runup on plane beaches as well as wave transformation over fringing reefs. The model accurately describes transition between supercritical and subcritical flows as well as development of dispersive waves in the processes.  相似文献   

A field experiment of walkaway distributed acoustic sensing vertical seismic profile in a deep and deviated onshore well in Japan using a fibre optic cable deployed inside coiled tubing     

Yuki Kobayashi  Yuto Uematsu  Shimpei Mochiji  Ziqiu Xue 《Geophysical Prospecting》2020,68(2):501-520

A two-dimensional walkaway vertical seismic profiling survey using distributed acoustic sensing was conducted at an onshore site in Japan. The maximum depth and the deviation of the observation well were more than 4,000 m and 81 degrees, respectively. Among the several methods for installing fibre optic cables, we adopted the inside coiled tubing method, in which coiled tubing containing a fibre optic cable is deployed. The signal-to-noise ratio of the raw shot gather was low, possibly due to poor coupling between the fibre optic cable and the subsurface formation resulting from the fibre optic cable deployment method and the existence of considerable tubewave noise. Nevertheless, direct P-wave arrivals, P–P reflections and P–S converted waves exhibited acceptable signal-to-noise ratios after careful optimization of gauge length for distributed acoustic sensing optical processing and the application of carefully parameterized tubewave noise suppression. One of the challenges in current distributed acoustic sensing vertical seismic profile data processing is the separation of P- and S-waves using only one-component measurements. Hence, we applied moveout correction using two-dimensional ray tracing. This process effectively highlights only reflected P-waves, which are used in subsequent subsurface imaging. Comparison with synthetic well seismograms and two-dimensional surface seismic data confirms that the final imaging result has a sufficiently high quality for subsurface monitoring. We acquired distributed acoustic sensing vertical seismic profile data under both flowing conditions and closed conditions, in which the well was shut off and no fluid flow was allowed. The two imaging results are comparable and suggest the possibility of subsurface imaging and time-lapse monitoring using data acquired under flowing conditions. The results of this study suggest that, by adopting the inside coiled tubing method without drilling a new observation well, more affordable distributed acoustic sensing vertical seismic profile monitoring can be achieved in fields such as CO₂ capture and storage and unconventional shale projects, where monitoring costs have to be minimized.  相似文献   

VSOP monitoring of the Quasar 1928+738     

D. W. Murphy  S. J. Tingay  R. A. Preston  D. L. Meier  D. L. Jones  J. C. Guirado  A. Polatidis  J. E. Conway  H. Hirabayashi  H. Kobayashi  Y. Murata 《New Astronomy Reviews》1999,43(8-10)

We present the results from a campaign to monitor the relatively low redshift (z=0.3) circumpolar superluminal quasar 1928+738 with VSOP during the first Announcement of Opportunity period. The four epochs of data show that there have been substantial structural changes in this source near the core on the time-scale of a few months.  相似文献   

Evaluating metrics derived from Landsat 8 OLI imagery to map crop cover     

Rei Sonobe  Yuki Yamaya  Hiroshi Tani  Xiufeng Wang  Nobuyuki Kobayashi  Kan-ichiro Mochizuki 《国际地球制图》2019,34(8):839-855

Developing techniques are required to generate agricultural land cover maps to monitor agricultural fields. Landsat 8 Operational Land Imager (OLI) offers reflectance data over the visible to shortwave-infrared range. OLI offers several advantages, such as adequate spatial and spectral resolution, and 16 day repeat coverage, furthermore, spectral indices derived from Landsat 8 OLI possess great potential for evaluating the status of vegetation. Additionally, classification algorithms are essential for generating accurate maps. Recently, multi-Grained Cascade Forest, which is also called deep forest, was proposed, and it was shown to give highly competitive performance for classification. However, the ability of this algorithm to generate crop maps with satellite data had not yet been evaluated. In this study, the reflectance at 7 bands and 57 spectral indices calculated from Landsat 8 OLI data were evaluated for its potential for crop type identification.  相似文献   

Seasonal variations of shelf circulation in Hidaka Bay,Hokkaido, Japan,with an interpretation of the migration route of juvenile walleye pollock     

Ana Luisa Rosa  Yutaka Isoda  Naoto Kobayashi 《Journal of Oceanography》2009,65(5):615-626

The outer shelf of Funka Bay, located at the bay head of Hidaka Bay, is a recognised main winter spawning ground for walleye pollock (Theragra chalcogramma), whose newly hatched juveniles migrate eastward along the Hidaka shelf to the nursery ground located in the Doto area. To examine the seasonal change of the coastal current along this migration route, four current moorings were deployed along the shelf in Hidaka Bay from April, 2004 to June, 2006. Since these mooring sites were close to the coast, the circulation was estimated after removal of the wind-driven component. It was found that the winter coastal flow, forced by a north-westerly monsoon wind, is clockwise along the Hidaka shelf. However, this flow is weak due to the superimposition of the opposite Coastal Oyashio flow trapped on the shelf. In summer, a bifurcation of the coastal current occurs along the north-eastern Hidaka shelf with a south-eastward flow, associated with the Tsugaru Gyre, and a north-westward flow, consisting of a branch from this gyre. Our results provide a new understanding of the migration of juvenile walleye pollock: (1) very slow transport of juveniles along the Hidaka shelf from winter to spring, and (2) selection of earlier spawning survivors due to the bifurcated flow in early summer.  相似文献