Analysis of the appearance and disappearance of point objects over time     

Yukio Sadahiro 《International journal of geographical information science》2019,33(2):215-239

The appearance and disappearance of immovable points are important spatiotemporal events in geographical information science. They represent phenomena such as the birth and death of trees in forests, construction and destruction of buildings in cities and openings and closures of shops and restaurants. This paper proposes a new method for analyzing the appearance and disappearance of points. The method helps analysts capture the overall picture and regional variation of event pattern and detecting significant local patterns. Four measures are defined that indicate the intensity of spatial and temporal patterns of events. The measures are visualized as grid maps. A statistical test is used to evaluate the significance of the measures to extract the regions of significant patterns. The proposed method is applied in an analysis of shops and restaurants in Shibuya, Tokyo. Technical soundness of the method is discussed along with empirical findings.  相似文献   

Statistical methods for analyzing the distribution of spatial objects in relation to a surface     

Yukio Sadahiro 《Journal of Geographical Systems》1999,1(2):107-136

This paper develops statistical methods for analyzing the distribution of spatial objects—points, convex polygons, and line segments—in relation to a surface. We propose statistics for measuring the relationship between the distribution of these objects and a surface and derive their expectations and variances under the null hypothesis that the objects are independently and randomly distributed. The statistics are approximately distributed according to the normal distribution under the null hypothesis, which enables us to test the significance of the spatial relationships statistically. Using the proposed methods, we empirically analyze the distribution of convenience stores in relation to the distribution of population in a suburb of Osaka, Japan. Some empirical findings are shown.  相似文献   

Ore Mineralogy and Mineral Chemistry of the Ashanti Gold Deposit at Obuasi, Ghana     

Shiloh OSAE  Katsuo KASE  Masahiro YAMAMOTO 《Resource Geology》1999,49(1):1-11

Abstract: The gold deposit at Ashanti occurs in the Proterozoic Birimian formation of Ghana. Two main ore types mined from the deposit are gold-bearing quartz veins, and gold-sulfide disseminations in metasediments and metavolcanics. The main sulfide minerals in the gold-sulfide disseminated ores are arsenopyrite, pyrite and pyrrhotite, and to a very minor extent, sphalerite and tetrahedrite. Carbonate alteration and sericitization are prominent in the metavolcanics and the metasediments, respectively. In the quartz veins, pyrite and arsenopyrite commonly occur in small amounts, but gold mostly occurs in contact with tetrahedrite, chalcopyrite, galena, aurostibite, and sphalerite. Pyrrhotite is absent in the quartz veins.
Microprobe studies indicate that As content of homogeneous arsenopyrite grains ranges from 27. 0 to 31. 7 atm%, and gives mineralization temperatures from 170 to 430°C, although mostly from 300 to 400°C. Chlorite geothermometry using temperature dependence of substitution of Al for Si in the tetrahedral site gives formation temeratures of 330 to 400°C, comparable to the arsenopyrite temperatures. Applying sphalerite–pyrite–pyrrhotite geobarometry to sphalerite with FeS contents from 13. 6 to 12. 5 mol%, the pressure was estimated to be in a range from 5. 9 to 7. 0 kb at the stage of elevated temperatures.
Mineralogical observations, especially absence of pyrrhotite in the quartz veins, together with microprobe data for gold and associated minerals suggest that the fluids having ascended through fissures in the Ashanti deposit were reduced by the reaction with carbonaceous materials in the metasediments during the declining stage of the regional metamorphism.  相似文献   

High-Reflectivity Coatings for a Vacuum Ultraviolet Spectropolarimeter     

Noriyuki Narukage  Masahito Kubo  Ryohko Ishikawa  Shin-nosuke Ishikawa  Yukio Katsukawa  Toshihiko Kobiki  Gabriel Giono  Ryouhei Kano  Takamasa Bando  Saku Tsuneta  Frédéric Auchère  Ken Kobayashi  Amy Winebarger  Jim McCandless  Jianrong Chen  Joanne Choi 《Solar physics》2017,292(3):40

Precise polarization measurements in the vacuum ultraviolet (VUV) region are expected to be a new tool for inferring the magnetic fields in the upper atmosphere of the Sun. High-reflectivity coatings are key elements to achieving high-throughput optics for precise polarization measurements. We fabricated three types of high-reflectivity coatings for a solar spectropolarimeter in the hydrogen Lyman-\(\upalpha \) (Ly\(\upalpha \); 121.567 nm) region and evaluated their performance. The first high-reflectivity mirror coating offers a reflectivity of more than 80 % in Ly\(\upalpha \) optics. The second is a reflective narrow-band filter coating that has a peak reflectivity of 57 % in Ly\(\upalpha \), whereas its reflectivity in the visible light range is lower than 1/10 of the peak reflectivity (\(\sim 5~\%\) on average). This coating can be used to easily realize a visible light rejection system, which is indispensable for a solar telescope, while maintaining high throughput in the Ly\(\upalpha \) line. The third is a high-efficiency reflective polarizing coating that almost exclusively reflects an s-polarized beam at its Brewster angle of 68° with a reflectivity of 55 %. This coating achieves both high polarizing power and high throughput. These coatings contributed to the high-throughput solar VUV spectropolarimeter called the Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP), which was launched on 3 September, 2015.  相似文献   

High‐pressure polymorphs of magnesian orthopyroxene from a shock vein in the Yamato‐000047 lherzolitic shergottite     

Naoya IMAE  Yukio IKEDA 《Meteoritics & planetary science》2010,45(1):43-54

Abstract– We found a simple thin shock vein, less than or equal to about 60 μm in width and 1.8 mm in length, in the poikilitic area in the Yamato (Y‐) 000047 lherzolitic shergottite. The shock vein occurs only in magnesian Ca‐poor clinopyroxene, which may have transformed from orthopyroxene during the pressure increase at the shock event. The shock vein consists of (Mg_0.8,Fe_0.2)SiO₃ pyroxene polymorphs, such as columnar akimotoite, two kinds of pyroxene glasses, dendritic akimotoite, and framboidal pyroxene glass, in the order from the periphery to the center. The compositions and textures suggest that columnar akimotoite in the periphery of the shock vein crystallized from solid‐state phase transition of clinopyoroxene during the cooling of the vein, and the remains in the shock vein solidified from shock‐produced melt. The glass includes two kinds of massive glass in the vein and framboidal glass in the vein center. The framboidal glass is the most magnesian and may have been vitrified from perovskite crystallized from high‐pressure melt produced at high temperature ≥3000 °C and high‐pressure 23–40 GPa. Dendritic akimotoites in the vein center metastably crystallized from residual shock melt. The formation sequences of the constituent phases in the shock vein happen in the following order: columnar akimotoites, rim glass, center glass, framboidal glass, and dendritic akimotoites. The increase of the Raman intensity of 660–670 cm^?1 in the order of rim glass, center glass, and framboidal glass suggests that the formation of the pyroxene chain proceeds faster in the vein center than in the vein rim due to its slower cooling. The finding of the shock vein consisting merely of high‐pressure polymorphs of pyroxene, akimotoite, and framboidal glass (vitrified perovskite) is the first reported among all Martian meteorites.  相似文献   

Corrigendum to “New insight into a subduction-related orogen: A reappraisal of the geotectonic framework and evolution of the Japanese Islands” [Gondwana Research 18 (2010) 82–105]     

Yukio Isozaki  Kazumasa Aoki  Takaaki Nakama  Shuichi Yanai 《Gondwana Research》2010,18(4):365

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The Indian Ocean subtropical dipole mode simulated in the CMIP3 models     

Takahito Kataoka  Tomoki Tozuka  Yukio Masumoto  Toshio Yamagata 《Climate Dynamics》2012,39(6):1385-1399

Using observation data and outputs from the “twentieth-century climate in coupled models” (20c3m) control runs of coupled general circulation models submitted to the Coupled Model Intercomparison Project, phase 3 (CMIP3), the ability of CMIP3 models to simulate the Indian Ocean subtropical dipole (IOSD) and its influence on the rainfall anomaly over the southern African region is investigated. Many models simulate the IOSD, but the location and shape of the sea surface temperature anomaly vary among models. This model bias is closely linked to the bias in simulating the anomalous strengthening and southward shift of the subtropical high. Almost all models fail to simulate the rainfall anomaly associated with the IOSD owing to the inaccurate simulation of the location of sea surface temperature and sea level pressure anomalies.  相似文献   

Provenance diversification within an arc‐trench system induced by batholith development: the Cretaceous Japan case     

Kazumasa Aoki  Yukio Isozaki  Daisuke Kofukuda  Tomohiko Sato  Atsushi Yamamoto  Kenshi Maki  Shuhei Sakata  Takafumi Hirata 《地学学报》2014,26(2):139-149

By comparing detrital zircon U–Pb age spectra of coeval fore‐arc and back‐/intra‐arc basin sandstones, we identified the overall distributary pattern of terrigenous clastic material within the Cretaceous arc system of SW Japan. Abundant Proterozoic (c. 1500–2500 Ma) detrital grains from the interior of East Asia are present in the Cretaceous intra‐arc basin. However, after a barrier mountain range formed during batholith emplacement, Proterozoic clastics were rarely transported into the fore‐arc domain. Episodic batholith formation in Pacific‐type orogens likely played a major role in controlling terrigenous supply routes between coeval back‐arc and fore‐arc domains. The Cretaceous orogen in Japan thus provides a good template for analysing the tectono‐sedimentary development of other arc‐related basins.  相似文献   

Effects of air�Csea coupling on the boreal summer intraseasonal oscillations over the tropical Indian Ocean     

Ailan Lin  Tim Li  Xiouhua Fu  Jing-Jia Luo  Yukio Masumoto 《Climate Dynamics》2011,37(11-12):2303-2322

The effects of air?Csea coupling over the tropical Indian Ocean (TIO) on the eastward- and northward-propagating boreal summer intraseasonal oscillation (BSISO) are investigated by comparing a fully coupled (CTL) and a partially decoupled Indian Ocean (pdIO) experiment using SINTEX-F coupled GCM. Air?Csea coupling over the TIO significantly enhances the intensity of both the eastward and northward propagations of the BSISO. The maximum spectrum differences of the northward- (eastward-) propagating BSISO between the CTL and pdIO reach 30% (25%) of their respective climatological values. The enhanced eastward (northward) propagation is related to the zonal (meridional) asymmetry of sea surface temperature anomaly (SSTA). A positive SSTA appears to the east (north) of the BSISO convection, which may positively feed back to the BSISO convection. In addition, air?Csea coupling may enhance the northward propagation through the changes of the mean vertical wind shear and low-level specific humidity. The interannual variations of the TIO regulate the air?Csea interaction effect. Air?Csea coupling enhances (reduces) the eastward-propagating spectrum during the negative Indian Ocean dipole (IOD) mode, positive Indian Ocean basin (IOB) mode and normal years (during positive IOD and negative IOB years). Such phase dependence is attributed to the role of the background mean westerly in affecting the wind-evaporation-SST feedback. A climatological weak westerly in the equatorial Indian Ocean can be readily reversed by anomalous zonal SST gradients during the positive IOD and negative IOB events. Although the SSTA is always positive to the northeast of the BSISO convection for all interannual modes, air?Csea coupling reduces the zonal asymmetry of the low-level specific humidity and thus the eastward propagation spectrum during the positive IOD and negative IOB modes, while strengthening them during the other modes. Air?Csea coupling enhances the northward propagation under all interannual modes due to the persistent westerly monsoon flow over the northern Indian Ocean.  相似文献   

Timing of collision of the Kohistan–Ladakh Arc with India and Asia: Debate     

HAFIZ UR REHMAN  TETSUZO SENO  HIROSHI YAMAMOTO  TAHSEENULLAH KHAN 《Island Arc》2011,20(3):308-328

The Kohistan–Ladakh Arc in the Himalaya–Karakoram region represents a complete section of an oceanic arc where the rocks from mantle to upper crustal levels are exposed. Generally this arc was regarded as of Jurassic–Cretaceous age and was welded to Asia and India by Northern and Southern Sutures respectively. Formation of this arc, timings of its collisions with Asia and India, and position of collision boundaries have always been controversial. Most authors consider that the arc collided with Asia first during 102–75 Ma and then with India during 55–50 Ma, whereas others suggest that the arc collided with India first at or before 61 Ma, and then the India–arc block collided with Asia ca 50 Ma. Recently published models of the later group leave several geological difficulties such as an extremely rapid drifting rate of the Indian Plate (30 ± 5 cm/year) northwards between 61–50 Ma, absence of a large ophiolite sequence and accretionary wedge along the Northern Suture, obduction of ophiolites and blueschists along the Southern Suture, and the occurrence of a marine depositional environment older than 52 Ma in the Indian Plate rocks south of the Southern Suture. We present a review based on geochemical, stratigraphic, structural, and paleomagnetic data to show that collision of the arc with Asia happened first and with India later.  相似文献