排序方式： 共有43条查询结果，搜索用时 515 毫秒
31.
The aculeate and isopteran fauna was surveyed in 1982 on the Krakatau islands, all the biota of which had been exterminated by the great eruption in 1883.The pattern of colonization of these insects (wasps, bees and termites) and the present state of their faunas are discussed based upon our 1982 survey and those made earlier. Species numbers varied only slightly between the four islands in spite of their differing sizes. This may be because the islands are situated close to each other and most of the aculeates prefer open sites rather than forests.The species/time curve for the Aculeata as a whole was still rising in 1982. However, in some groups flattening of the curve had occurred, and a comparison of species number in social wasps and bees, for example, between Java, Krakatau and Sumatra suggested the occurrence of supersaturation. Cumulative species numbers was distinctly larger than actual number in the three most recent surveys showing that several species must have become extinct in each intersurvey period. Species turnover associated with habitat changes may have occurred for the whole island group and on particular islands.Analysis of the colour pattern of the Krakatau populations of certain species with different geographical races on Java and Sumatra showed that the Javan elements have a slight preponderance over the Sumatran ones on the Krakataus.Some examples of faunal disharmony were found; the most remarkable was the almost complete lack of species of swarm-founding social wasps and bees, and of ground-nesting termites probably reflecting their poor dispersal ability across the sea barrier. 相似文献
32.
Junichi Takeuchi Naoto Honda Yoshitaka Morikawa Takashi Koike Yutaka Nagata 《Journal of Oceanography》1998,54(1):45-52
Along the southwest coast of the Kii Peninsula, a bifurcation current is regularly observed. By using ADCP data taken on board
the R/V Wakayama of the Wakayama Prefectural Fisheries Experimental Station, characteristics of this bifurcation current are
analyzed. The occurrence frequency of the bifurcation current reaches about 70% in the period from 1988 to 1996. The bifurcation
point appears to be changeable and occurs almost evenly between Cape Ichie and Cape Shionomisaki. The current divergence in
the alongshore direction was also investigated. Positive divergence values dominated in the whole analyzed area, and an onshore
current appears to be dominant along the southwest coast of the Kii Peninsula, except in 1990 when the Kuroshio flowed in
a large meandering path. 相似文献
33.
We present an original implementation of the free-surface boundary condition in a mesh-free finite-difference method for simulating elastic wave propagation in the frequency domain. For elastic wave modelling in the frequency domain, the treatment of free surfaces is a key issue which requires special consideration. In the present study, the free-surface boundary condition is directly implemented at node positions located on the free-surface. Flexible nature of the mesh-free method for nodal distribution enables us to introduce topography into numerical models in an efficient manner. We investigate the accuracy of the proposed implementation by comparing numerical results with an analytical solution. The results show that the proposed method can calculate surface wave propagation even for an inclined free surface with substantial accuracy. Next, we calculate surface wave propagation in a model with a topographic surface using our method, and compare the numerical result with that using the finite-element method. The comparison shows the excellent agreement with each other. Finally, we apply our method to the SEG foothill model to investigate the effectiveness of the proposed method. Since the mesh-free method has high flexibility of nodal distribution, the proposed implementation would deal with models of topographic surface with sufficient accuracy and efficiency. 相似文献
34.
35.
In this study, we develop a new integrated assessment model called the BET model (Basic Energy systems, Economy, Environment, and End-use Technology Model). It is a multi-regional, global model based on Ramsey’s optimal growth theory and includes not only traditional end-use technologies but also advanced end-use technologies such as heat-pump water heaters and electric vehicles. Using the BET model, we conduct simulations and obtain the following results. (1) Advanced end-use technologies have an important role in containing carbon prices as well as GDP losses when GHG (greenhouse gas) constraints are stringent. (2) Electrification based on energy services progresses rapidly in scenarios with stringent GHG constraints. This is because electricity can be supplied by various methods of non-fossil power generation, and advanced end-use technologies can drastically improve energy-to-service efficiencies. The BET’s results indicate the importance of analyses that systematically combine environmental constraints, end-use technologies, supply energy technologies, and economic development. 相似文献
36.
Jeremie Vaubaillon Pavel Koten Anastasios Margonis Juraj Toth Regina Rudawska Maria Gritsevich Joe Zender Jonathan McAuliffe Pierre-Dominique Pautet Peter Jenniskens Detlef Koschny Francois Colas Sylvain Bouley Lucie Maquet Arnaud Leroy Jean Lecacheux Jiri Borovicka Junichi Watanabe Jürgen Oberst 《Earth, Moon, and Planets》2015,114(3-4):137-157
37.
Junichi Tsutsui Yoshikatsu Yoshida Dong-Hoon Kim Hideyuki Kitabata Keiichi Nishizawa Norikazu Nakashiki Koki Maruyama 《Climate Dynamics》2007,28(2-3):199-214
From multi-ensembles of climate simulations using the Community Climate System Model version 3, global climate changes have been investigated focusing on long-term responses to stabilized anthropogenic forcings. In addition to the standard forcing scenarios for the current international assessment, an overshoot scenario, where radiative forcings are decreased from one stabilized level to another, is also considered. The globally-averaged annual surface air temperature increases during the twenty-first century by 2.58 and 1.56°C for increased forcings under two future scenarios denoted by A1B and B1, respectively. These changes continue but at much slower rates in later centuries under forcings stabilized at year 2100. The overshoot scenario provides a different pathway to the lower B1 level by way of the greater A1B level. This scenario results in a surface climate similar to that in the B1 scenario within 100 years after the forcing reaches the B1 level. Contrasting to the surface changes, responses in the ocean are significantly delayed. It is estimated from the linear response theory that temperature changes under stabilized forcings to a final equilibrium state in the A1B (B1) scenario are factors of 0.3–0.4, 0.9, and 17 (0.3, 0.6, and 11) to changes during the twenty-first century, respectively, for three ocean layers of the surface to 100, 100–500, and 500 m to the bottom. Although responses in the lower ocean layers imply a nonlinear behavior, the ocean temperatures in the overshoot and B1 scenarios are likely to converge in their final equilibrium states. 相似文献
38.
We estimated three-dimensional P- (Vp) and S-wave velocity (Vs) and Vp/Vs structures in and around the Onikobe volcanic area, northeastern Japan, by local travel time tomography. We used travel time data from source and receiver pairs located within and outside the study area, which plays an important role in obtaining the optimum ray coverage and in elucidating the deeper structure more accurately. Detailed information on deeper structures is essential for imaging the complete volcanic system from the magmatic source zone through areas of shallow hydrothermal circulation. More than 50 000 travel time data for the P-waves and 35 000 for the S-waves were used to image the velocity structure. Our results show the following dominant features: (1) two conduits in the upper crust with low Vp and low Vs indicative of H2O-rich fluid pathways: one lying beneath Naruko volcano, the other beneath the focal area of the 1962 Northern Miyagi earthquake (M6.5); (2) an underlying broad region in the lower crust with low Vp, low Vs and high Vp/Vs, suggestive of a zone of partial melt, from which the fluids in (1) are derived; and (3) low Vp/Vs areas near the surface of the Sanzugawa and Onikobe calderas, suggesting a diffuse vapor-saturated cap. 相似文献
39.
Yoshiaki Toba Junichi Kimura Hiroshi Murakami Myoungsun Kim Yasushi Yoshikawa Koji Shimada 《Journal of Oceanography》2001,57(2):141-154
In the previous paper (Toba and Murakami, 1998) we reported on an unusual path of the Kuroshio Current System, which occurred in April 1997 (April 1997 event), using the Ocean Color and Temperature Scanner (OCTS) data of the Advanced Earth Observing Satellite (ADEOS). The April 1997 event was characterized by the flow of the Kuroshio along the western slope (northward) and the eastern slope (southward) of the Izu-Ogasawara Ridge, a very southerly turning point at about 32°N, followed by a straight northward path up to 37°N of the Kuroshio Extension along the eastern flank of the Izu-Ogasawara and the Japan Trenches. Overlaying of depth contours on ADEOS-OCTS chlorophyll-a images at the April 1997 event demonstrates the bottom topography effects on the current paths. A new finding based on TOPEX/Poseidon altimeter data is that the sea-surface gradient across the Kuroshio/Kuroshio Extension diminished greatly in the sea area southeast of the central Japan, as a very temporary phenomenon prior to this event. This temporary diminishing of the upper-ocean current velocity might have caused a stronger bottom effect along the Izu-Ogasawara Ridge, and over the Izu-Ogasawara Trench disclosed a weak background, barotropic trench-flank current pattern, which existed otherwise independently of the Kuroshio Extension. The very southerly path of the Kuroshio Extension from winter 1996 to autumn 1998 corresponded, with a time lag of about 1.5 years, to the previous La Niña tendency with weaker North Equatorial Current. The April 1997 event occurred in accordance with its extreme condition. 相似文献
40.
Seasonal variations in coastal debris on Awaji Island, Japan 总被引：1，自引：1，他引：0
Shimizu T Nakai J Nakajima K Kozai N Takahashi G Matsumoto M Kikui J 《Marine pollution bulletin》2008,57(1-5):182-186
The subject of our study was Awaji Island, an island located in the west of Japan that is surrounded by sea and that has serious problems relating to coastal debris. We conducted a long-term investigation focusing on three beaches and evaluated the results. The study was designed to develop an understanding of the actual situation, to inform local citizens, and raise their concerns about the problem of debris with a view to taking action against it. We obtained the following results: the amount, type, and ratio of debris changed according to weather and ocean conditions; debris also differs according to geographical conditions; social and economic activities of the surrounding area influence the type of debris encountered. Following this study, we have continued our investigation, and are continuing to gather data. At the same time, it is important to spread our ideas and enlighten people so as to encourage them not to dump debris. We hope that these actions manage to raise the level of consciousness among local citizens and to expand their anti-debris activities. 相似文献