Biaxial effects in modelling earthquake response of R/C structures     

Haruo Takizawa  Hiroyuki Aoyama 《地震工程与结构动力学》1976,4(6):523-552

Recent studies reveal that R/C structural members subjected to biaxial flexure due to two-dimensional earthquake excitation can deform much more than would be predicted by conventional one-dimensional response analysis. The biaxial flexure may therefore have a significant effect on the dynamic collapse process of structures subjected to intense ground motions. The present paper is intended to develop a new formulation of the two-dimensional restoring force model of R/C columns acted upon by biaxial bending moments, and to discuss the dynamic response properties of R/C structures. The model considered is a two-dimensional extension of various non-linear models for one-dimensional response analysis, including the degrading trilinear stiffness model which is one of the simpler idealizations of the restoring force characteristics of flexural-failure-type R/C structures. The modelling validity is then examined by comparison with experimental data on the biaxial bending behaviour of R/C columns. Calculations are made to study the role of different system properties on the influence of inelastic biaxial bending on the dynamic structural response. It is shown that the inelastic biaxial effect is generally significant and, in some cases, critical in the case of R/C structures with stiffness-degrading properties, while the effect is not so important for the non-degrading inelastic cases.  相似文献   

New radioisotope-free method for measuring bacterial production using [15N5]-2′-deoxyadenosine and liquid chromatography mass spectrometry (LC–MS) in aquatic environments     

Kenji Tsuchiya  Tomoharu Sano  Nobuyuki Kawasaki  Hideki Fukuda  Noriko Tomioka  Koji Hamasaki  Yuya Tada  Shinji Shimode  Tatsuki Toda  Akio Imai 《Journal of Oceanography》2015,71(6):675-683

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Stoichiometry among bioactive trace metals in seawater on the Bering Sea shelf   总被引：2，自引：1，他引：1  

Abigail Parcasio Cid  Syouhei Urushihara  Tomoharu Minami  Kazuhiro Norisuye  Yoshiki Sohrin 《Journal of Oceanography》2011,67(6):747-764

The distribution of Al, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb in seawater was investigated on the Bering Sea shelf (56–64°N, 165–169°W) in September 2000. The unfiltered and filtered seawater samples were used for determination of total dissolvable (TD) and dissolved (D) metals (M), respectively. The TD-M concentrations were generally higher than in the Pacific Ocean. TD-Cd was highest in deep water of the outer shelf domain and dominated by dissolved species. The other TD-M were highest at stations close to the Yukon River delta and had higher fractions of labile particulate (LP) species that were obtained as the difference between TD-M and D-M. Dissolved Al, Ni, and Cu were characterized by input from the Yukon River. Dissolved Mn and Co showed maximums on the bottom of the coastal domain, suggesting influence of sedimentary Mn reduction. The correlations of D-Zn, D-Cd, and macronutrients indicated their distributions were largely controlled through uptake by microorganisms and remineralization from settling particles. All these three processes (river input, sedimentary reduction, and biogeochemical cycle) had an influence on the distribution of D-Fe. D-Pb was fairly uniformly distributed in the study area. The stoichiometry of D-M in the Bering Sea shelf showed enrichment of Co and Pb and depletion of Ni, Cu, Zn, and Cd compared with that in the North Pacific. The LP-M/LP-Al ratio revealed significant enrichment of the other eight metals relative to their crustal abundance, suggesting importance of formation of Fe–Mn oxides and adsorption of trace metals on the oxides.  相似文献   

Has the upper portion of the Japan Sea Proper Water formation really been enhancing?     

Yanlin Cui  Tomoharu Senjyu 《Journal of Oceanography》2012,68(4):593-598

Weakening of the upper portion of the Japan Sea Proper Water formation was detected based on the dissolved oxygen concentration and potential temperature from 1970 to 2004, unlike the suggestion of previous studies that it has been enhanced since the 1970s. The revealed warming and decreasing trends in DO concentration throughout the water column indicate that the conveyor belt system in the Japan Sea is still slowing down even in the intermediate layers, though a relatively active dissolved oxygen supply into the intermediate layers is suggested. This fact leads us to modify the previous concept about the water mass formation; though a relatively active formation of the intermediate water mass occurs, the deep water formation is not counterbalanced by the intermediate water formation, and the overall Japan Sea Proper Water formation has been stagnating since the 1970s.  相似文献   

Interdecadal oscillations in the Japan Sea proper water related to the arctic oscillation     

Yanlin Cui  Tomoharu Senjyu 《Journal of Oceanography》2010,66(3):337-348

The time series of dissolved oxygen (DO) concentration in the Japan Sea Proper Water (JSPW) shows clear interdecadal oscillation with about 20-year periodicity since the 1970s. This interdecadal variation in the DO concentration is positively correlated with the Arctic Oscillation (AO) index; the DO concentration tends to be high during a positive AO phase when the East Asian winter monsoon (EAWM) is relatively weak, which is considered to be an unfavorable condition for the JSPW formation. To clarify the discrepancy, the cause of the interdecadal oscillation was investigated using the wind at Wajima and sea surface temperature (SST) in the JSPW formation area. The cold-air outbreaks determined from the wind at Wajima are synchronized with the interdecadal oscillation of the AO; during a positive AO phase the cold-air outbreaks over the Japan Sea are more active, as reported by Isobe and Beardsley (2007). Since the SST in the JSPW formation area is negatively correlated with cold-air outbreaks, the activity of cold-air outbreaks is more important to the JSPW formation than the EAWM, at least on an interdecadal timescale. Significant correlations of the indicator of low pressure migration with the AO and cold-air outbreaks confirm that atmospheric disturbances move frequently into the Japan Sea from the East China Sea in a positive AO phase. A detailed examination of cold-air outbreaks revealed that the passing of atmospheric low pressures temporarily enhances the east-west pressure gradient over the Japan Sea and effectively brings cold air into the JSPW formation area.  相似文献   

Determination of plastic regions around underground openings by a coupled boundary-element-characteristics method     

Yuzo Obara  Tomoharu Nakayama  Katsuhiko Sugawara  Toshiro Aoki  Hyun Kuk Jang 《国际地质力学数值与分析法杂志》1992,16(10):701-716

A two-dimensional hybrid method for solving elastoplastic problems in engineering is presented by coupling two existing methods, namely, the boundary element method and the characteristics method. The formulation of this method is presented, as well as an excellent procedure for the determination of the boundary between elastic and plastic regions. It is shown not only that this method is a powerful and accurate method for evaluating the shape and extent of the plastic region around rock caverns, which is of prime importance for the construction of rock caverns, but also applicable to a given range of the initial stress field ratio where only compressive failure occurs. Then, some typical examples are solved in order to check the accuracy of the solution by this method. Furthermore, its successful applications are presented and discussed to determine the shape and the extent of the plastic regions around parallel, circular and rectangular openings.  相似文献   

Gamma-Ray Bursts and magnetar-forming Supernovae     

Ken’ichi Nomoto  Keiichi Maeda  Masaomi Tanaka  Tomoharu Suzuki 《Astrophysics and Space Science》2011,336(1):129-137

The connection between long Gamma Ray Bursts (GRBs) and Supernovae (SNe) have been established through the well observed cases. These events can be explained as the prompt collapse to a black hole (BH) of the core of a massive star (M≳40M _⊙). The energies of these GRB-SNe were much larger than those of typical SNe, thus these SNe are called Hypernovae (HNe). The case of SN 2006aj/GRB060218 appears different: the GRB was weak and soft, being called an X-Ray Flash (XRF); the SN is dimmer and has very weak oxygen lines. The explosion energy of SN 2006aj was smaller, as was the ejected mass. In our model, the progenitor star had a smaller mass than other GRB-SNe (M∼20M _⊙), suggesting that a neutron star (NS) rather than a BH was formed. If the nascent NS was strongly magnetized as a magnetar and rapidly spinning, it may launch a weak GRB or an XRF. The peculiar light curve of Type Ib SN 2005bf may also be powered by a magnetar. The blue-shifted nebular emission lines of 2005bf indicate the unipolar explosion possibly related to standing accretion shock instability (SASI) associated with a newly born NS.  相似文献   

Deep current structure in the Toyama Deep-Sea Channel in the Japan Sea     

Senjyu  Tomoharu 《Journal of Oceanography》2022,78(1):25-34

Journal of Oceanography - The flow field in the Toyama Deep-Sea Channel (TDSC) in the Japan Sea was investigated based on mooring observations. An asymmetric current system accompanying offshore...  相似文献   

Field measurements of absolute gravity in East Antarctica     

Koichiro Doi  Hideaki Hayakawa  Takahito Kazama  Toshihiro Higashi  Shingo Osono  Yoichi Fukuda  Jun Nishijima  Yuichi Aoyama  Junichi Ueda 《极地研究(英文版)》2013,(4):339-343

Abstract This paper reports the results of field-based absolute gravity measurements aimed at detecting gravity change and crustal displacement caused by glacial isostatic adjustment. The project was initiated within the framework of the 53rd Japanese Antarctic Research Expedition （JARE53）. Absolute gravity measurements, together with GPS measurements, were planned at several outcrops along the Prince Olav Coast and S6ya Coast of East Antarctica, including at Syowa Station. Since the icebreaker Shirase （AGB 5003） was unable to moor alongside Syowa Station, operations were somewhat restricted during JARE53. However, despite this setback, we were able to complete measurements at two sites： Syowa Station and Langhovde. The absolute gravity value at the Syowa Station IAGBN （A） site, observed using an FG-5 absolute gravimeter （serial number 210; FG-5 #210）, was 982 524 322.7＋0.1 ktGal, and the gravity change rate at the beginning of 2012 was -0.26 gGal.a-1. An absolute gravity value of 982 535 584.2~0.7 ktGal was obtained using a portable A-10 absolute gravimeter （serial number 017; A-10 #017） at the newly located site AGS01 in Langhovde.  相似文献   

Sudden strong current generated by an eddy in the eastern part of Wakasa Bay,Japan     

Atsushi Kaneda  Kouta Ayukawa  Naoki Hirose  Jun Tsuzuki  Yutaka Kumaki  Tomoharu Senjyu  Yosuke Igeta  Tatsuro Watanabe 《Journal of Oceanography》2017,73(2):181-192

A sudden strong coastal current called a “kyucho” occurred in August 2013 in the eastern coastal waters of Wakasa Bay, Japan. This study examined its characteristics based on both observational data collected by intensive field investigations and the simulation results of a numerical model. The field investigations comprised moored buoy observations near the coast and voyages by a research vessels and fishing boats. The mooring observations indicated that a current speed exceeding 50 cm s^?1 occurred abruptly near the eastern coast of the bay, in association with a synchronous change in the current direction. Data collected by acoustic Doppler current profilers (ACDPs) mounted on the vessels showed that a clockwise eddy existed in the bay and that the current on the east side of the eddy generated the kyucho near the coast. Based on the results of the numerical model and the analysis of the ADCP data, it was considered that the clockwise eddy was generated by a strong current at the tip of the Tango Peninsula, in the western part of the bay. As the eddy propagated from west to east across the bay, it induced the kyucho in the coastal waters in the east of the bay.  相似文献