Mountain ordering: A method for classifying mountains based on their morphometry     

Shuji Yamada 《地球表面变化过程与地形》1999,24(7):653-660

A new method for classifying mountain morphology, ‘mountain ordering,’ is proposed, and quantitative expressions for various morphological parameters of two ordered mountains in northern Japan were obtained using this method. Mountain order was defined in terms of the closed contour lines on a topographic map. A set of closed, concentric contour lines defines a first-order mountain. Higher-order mountains can be defined as a set of closed contour lines that contain lower-order mountains and that have only one closed contour line for each elevation; they are identified as m + 1th-order mountains, where m represents the order of the enclosed, lower-order mountains. The geomorphometry for a mountain ordered according to this definition permits the identification of systematic relationships between various morphological parameters. The relationships between mountain order and these morphological parameters follow a form similar to that of Horton's laws, and permit the calculation of the ratios of number, area and height; these parameters are sufficient to express the magnitude of a mountain's dissection. The size–frequency distribution for area and height shows self-similarity for ordered mountains, and determines their fractal dimensions. Furthermore, the relationship between area and height, which has the form of a power function, describes the relief structure of ordered mountains. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

On the importance of accurately ray-traced troposphere corrections for Interferometric SAR data     

Thomas Hobiger  Youhei Kinoshita  Shingo Shimizu  Ryuichi Ichikawa  Masato Furuya  Tetsuro Kondo  Yasuhiro Koyama 《Journal of Geodesy》2010,84(9):537-546

Numerical weather models offer the possibility to compute corrections for a variety of space geodetic applications, including remote sensing techniques like interferometric SAR. Due to the computational complexity, exact ray-tracing is avoided in many cases and mapping approaches are applied to transform vertically integrated delay corrections into slant direction. Such an approach works well as long as lateral atmospheric gradients are small enough to be neglected. But since such an approximation holds only for very rare cases it is investigated how horizontal gradients of different atmospheric constituents can evoke errors caused by the mapping strategy. Moreover, it is discussed how sudden changes of wet refractivity can easily lead to millimeter order biases when simplified methods are applied instead of ray-tracing. By an example, based on real InSAR data, the differences of the various troposphere correction schemes are evaluated and it is shown how the interpretation of the geophysical signals can be affected. In addition, it is studied to which extend troposphere noise can be reduced by applying the exact ray-tracing solution.  相似文献   

Hydrothermal Formation of Lath-Shaped Trioctahedral Smectite with High Crystallinity     

Hirohisa YAMADA Kenji TAMURA Shingo YOKOYAMA Yujiro WATANABE 《《地质学报》英文版》2006,80(2):290-295

Lath-shaped and highly crystalline trioctahedral smectites were synthesized under hydrothermal conditions. The quenched glasses with stoichiometrically dehydrated Na-smectite compositions were treated at （a） 500℃ and 100 MPa for 1 and 11 days; and （b） 300℃ and 100 MPa for 7 days. The crystallinity and particle size of products were dependent on the chemical composition of the starting glass, synthetic temperature and duration of hydrothermal treatment. The high structural ordering and large dimensions of the products were confirmed from the sharpness of XRD peaks; and hydration behavior under controlled relative humidity. Transmission electron microscopy was also performed for the characterization of the particle size of product. Particle sizes vary from ca. 10 nm to a few pm by changing the chemical compositions of the starting materials. The product with the highest structural ordering and largest dimension was obtained from Nao.33（Mg1.83Al0.67）Si4O11 glass treated at 500℃ and 100 MPa for 1 day. The obtained results also confirmed the metastability and compositional dependency in the formation of highly crystalline trioctahedral smectite at hydrothermal conditions.  相似文献   

Meander of the Kuroshio front and current variability in the East China Sea     

Takashige Sugimoto  Shingo Kimura  Kuniaki Miyaji 《Journal of Oceanography》1988,44(3):125-135

To investigate the fluctuation of the Kuroshio front, moored current meters were deployed near the shelf break and on the continental slope in the East China Sea, northwest of Okinawa Island, during a period from 25 June to 22 July 1984. Two mooring arrays were deployed on the slope of about 800 m water depth (under the Kuroshio), about 30 km apart along the path of the Kuroshio. Another two arrays were set near the shelf break of about 300 m water depth. The fluctuation of current on the slope is found to have a predominant period of 11–14 days and a were length of 300–350 km, propagating toward the downstream direction of the Kuroshio with a phase velocity of about 30 cm sec^?1. When the Kuroshio front approaches the shelf break and the crest of the meander covers the mooring site, the current direction moves toward the downstream direction of the Kuroshio and the water temperature increases. On the other hand, when the trough of the meander covers the mooring site, the current direction changes off-shoreward across the Kuroshio or in the upstream direction of the Kuroshio, and the water temperature decreases. Three-dimensional distributions of water temperature and salinity around the mooring site were observed with a CTD twice at 5.5 days intervals, which indicate the meanders of the front is about 180° out of phase. This coincides with a period of 11–14 days obtained with the moored current meters. Wave lengths of the dominant meander of the front in the satellite thermal images were about 350 km and 100–200 km, which also coincides with results obtained with the moored current meters.  相似文献   

Permeability and pore-connectivity variation of pumices from a single pyroclastic flow eruption: Implications for partial fragmentation     

Michihiko Nakamura  Keiichi Otaki  Shingo Takeuchi 《Journal of Volcanology and Geothermal Research》2008

The relationship between permeability and vesicularity in volcanic rocks has been used to infer the degassing behavior of hydrous magma. Recent data on natural samples from various eruptions show a wide variation, fitting a power–law relationship of the percolation models with low (< 30%) critical vesicularity (Ф_C). In this study, we present data on permeability and pore-connectivity of juvenile rhyolitic pumice clasts in a pyroclastic flow around Onikobe volcano, NE Japan, and investigate their relationship with vesicularity developed in a single eruption event. The permeability of the pumices having a relatively low abundance of microlites and microphenocrysts shows a trend increasing by 4 orders of magnitude (from 10^− 13.8 to 10^− 10.1 m²) in a high and narrow vesicularity range (from 72 to 80%). This trend intersects at a high angle with the fit to the permeability–vesicularity data in the previous studies that has a low Ф_C, and is located on the extension of the trend for the products of isotropic decompression experiments. The two-dimensional (2D) connectivities of pores for the pumices were also measured from thin sections. From the point of view of percolation theory, connectivity provides information about the probability of percolation. They showed a steep increase from ca. 0 to 0.7 in an almost similar vesicularity range, as compared to their permeabilities. We attribute the increase in 2D connectivity to the increasing amount of ruptured bubble walls, which might have provided less-tortuous paths through larger apertures for gas flow. This, in turn, would cause an effective increase in the permeability. Aggregates of bubble-wall-shaped glass shards were found in the pumices, and their amount and degree of welding are higher in the pumices that have a higher abundance of microlites and microphenocrysts. These pumices have relatively high permeability and 2D connectivity at low vesicularity, which is accounted for by the existence of large irregularly shaped pores. These textural characteristics suggest that a series of partial fragmentation processes, including local rupturing of bubble walls and subsequent foam-collapse with permeable gas flow, might have occurred before the ultimate bulk fragmentation, thus resulting in the increase in permeability. We suggest that the 2D connectivity of pores is a useful parameter to quantify the degree of fragmentation of bubble walls and has the potential for use to assess their permeability.  相似文献   

Distribution of sea cucumbers in relation to sediment characteristics in coral reef lagoons and adjacent waters around Ishigaki Island,southern Japan     

Iwao Tanita  Hideaki Yamada 《Marine Ecology》2019,40(5)

To elucidate which environmental factors affect lagoonal‐scale sea cucumber distributions in Ishigaki Island, Okinawa, Japan, intertidal and subtidal areas of three coral reef lagoons were classified into several ground divisions by bottom characteristics, and sea cucumber densities therein were compared with the composition of sediment cover, grain size and organic content, and coverage of macroalgae, seagrass, and massive corals. Holothuria atra, Holothuria leucospilota, Stichopus chloronotus, and Synapta maculata had highest densities in the nearshore areas but were rare in reef flats, probably because of wave disturbance and low areal cover of sand sediment as potential feeding environments. No relationship was observed between sea cucumber densities and sediment organic content or grain size. Thus, even if these sea cucumbers have selectivity for habitats with a high sediment organic content, the effect of such selectivity on the distribution seems to be limited to relatively small areas. The sea cucumber distributions can be classified by bottom sediment/biota composition into bedrock (H. leucospilota), sand (H. atra), and lagoonal types (St. chloronotus and Sy. maculata). These habitat selections were possibly related to various aspects of sea cucumber ecology such as refuge from predators or turbulence, or settlement and nursery place, which have implications for importance of the complexity of lagoonal‐scale topography and sediment/biota conditions for the coexistence of various holothurian species.  相似文献   

长江三角洲经济与社会可持续发展若干问题咨询综合报告   总被引：14，自引：1，他引：13  

中国科学院学部长江三角洲经济与社会可持续发展咨询组 《地球科学进展》1999,14(1):4-10

长江三角洲是我国最大的经济核心区,特别是邓小平同志多次视察上海并决定浦东开发开放以来,这一地区的经济建设取得了举世瞩目的发展。该地区虽仅占有全国１％的土地、６％的人口,但１９９６年所创产值却占国内生产总值的１５１％,相当于全国财政收入的１８７％。同时,该地区也已成为继珠江三角洲之后我国与世界各国经济往来最频繁的地区和海内外投资的新的热点。但是,长江三角洲在经济增长方式、产业结构与布局、农业持续发展、长江口整治与建设上海国际航运中心、环境保护等方面也存在不少亟待研究和解决的问题。受国家计委委托,中国科学院学部从１９９６年开始组织江、浙、沪地区的有关院士和专家,对长江三角洲地区的经济与社会可持续发展的几个重大问题进行了长达两年的调查研究,提出了《长江三角洲经济与社会可持续发展若干问题咨询综合报告》及４个专题报告。本刊摘要转发该综合报告,供国内地学界科技人员从事有关研究时参考。《报告》认为,长江三角洲应在我国率先实现现代化并带动长江沿江经济带和长江流域的发展。在现有经济支柱的基础上,进一步确立长江三角洲在长江流域乃至全国的经济主导地位,建设成为三大基地,发挥四大功能,提供五方面服务,即：成为我国进入世界市场、  相似文献   

H I observations of galaxies behind the Milky Way in the Puppis region     

Pierre Chamaraux  Jean-Louis Masnou  Ilya Kazés  Mamoru Sait&#;  Tadafumi Takata  Toru Yamada 《Monthly notices of the Royal Astronomical Society》1999,307(2):236-252

We report 21-cm H  i line observations of 161 galaxies located behind the Milky Way, in the Puppis region. The observations have been carried out with the Nançay radio telescope, resulting in 101 detections. Most of the galaxies observed appear in the ESO catalogue, and present apparent diameters larger than 1.6 arcmin. We show that the detection rate is strongly related to the apparent diameter; it is as high as 76 per cent for diameters larger than 1.6 arcmin. Half of the non-detections result, in fact, from an insufficient velocity coverage. Global parameters of the detected galaxies are computed, after a careful discussion of the correction for Galactic absorption. Our H  I data are then compared with those obtained by Kraan-Korteweg & Huchtmeier with the Effelsberg radio telescope for 20 galaxies observed in common: the agreement is excellent, implying respective uncertainties on recession velocities and on H  I fluxes lower than 10 km s⁻¹ and 2 Jy km s⁻¹ on average. Finally, we find that the detected galaxies follow well the correlation between the optical linear diameter and the H  I mass found by Haynes & Giovanelli. This result shows that our diameter corrections for Galactic absorption A_B are quite good, except for eight objects which are heavily obscured ( A_B 2.3), or have a very small diameter, lower than 0.5 arcmin.  相似文献   

Effects of Benthic Flux on Short Term Variations of Nutrients in Aburatsubo Bay   总被引：1，自引：0，他引：1  

Kazufumi Takayanagi  Hisashi Yamada 《Journal of Oceanography》1999,55(3):463-469

In order to investigate effects of benthic flux on the short-term variations in the distribution of nutrients in coastal waters, the concentrations of nutrients (PO₄ ^3-, NH₄ ⁺ NO₃ ^-, NO₂ ^- and H₄SiO₄) and other oceanographic parameters were measured every three hours over a 24-hour period at four fixed stations in the water column of Aburatsubo Bay, a shallow semi-enclosed inlet. Sediment cores were also taken from a fixed station once in each season over one year to quantitatively determine their benthic flux. Consistent linear negative correlations were found between their concentrations and salinity in the surface layers. This result suggests that fresh water was the main source of these nutrients and a physical mixing was the major process controlling their distribution. Monthly variations of PO₄ ^3- and NH₄ ⁺ monitored for 18 months in the bay also indicate that the high surf concentration of these nutrients was associated with the appearance of low salinity waters. On the other hand, in the bottom layers, a linear correlation between the concentration of the nutrients and salinity became weak, especially for NH₄ ⁺ and PO₄ ^3-. Their concentrations were higher than the predicted value from the conservative mixing between the fresh water and seawater, indicating the possibility of another source in the bottom layers. Benthic flux is suggested as a possible source. Pore water profiles of NH₄ ⁺ and PO₄ ^3- indicate their flux towards the overlying seawater, which is quantitatively consistent with their water column distributions.  相似文献   

International Geomagnetic Reference Field 2000   总被引：6，自引：0，他引：6  

International Association of Geomagnetism  Aeronomy Division V  Working Group 《Geophysical Journal International》2000,141(1):259-262

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