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61.
Abbas?Majdi Hamed?Ajamzadeh Siavash?NadimiEmail author 《Arabian Journal of Geosciences》2016,9(7):512
This paper presents the results of a numerical study that has been performed to investigate the different joint types that affect the moment-rotation relation and ultimate bending moment capacity of a joint. A 3D finite element method was adapted to establish elaborate numerical models of segments. To evaluate the possible differences in moment-rotation behavior between different joint types, 10 different joint types were simulated. Additionally, the effect of different joint types on behavior of a lining ring was investigated. The validity of the peridynamic simulation was tested by comparing results obtained in this paper against the results obtained in a study performed by Hordijk and Gijsbers. Observations of the results demonstrate that in a flat joint, the expanding of joint height increased the rotation stiffness of the joint in the linear branch, and accordingly, the ultimate bending moment of the joint increased. In the ring model, it was observed that the expanding of joint height led to the decreased of ring displacement and stress concentration in the joint. Whenever there were full surface contacts (contact two segment in total cross section) in the joints, the rotation stiffness of the joints in the linear branch became equal, and, as a result, the displacement in the ring model was the same in all joint types. In addition, it was observed that using a convex joint in the ring model increases the displacement of the ring. The ultimate bending moment of bolted joints was higher than that of joints without bolts, especially in the case of a negative moment. 相似文献
62.
Tertiary reservoir represented by Jeribe, Anah, Azkand, and Azkand/Ibrahim formations has been studied from reservoir characterization point of view in Khabbaz Oil Field/Northern Iraq. Examined thin sections prepared from core rock samples which are selected from the wells Kz-8 and Kz-9 revealed the existence of different microfacies in which are varies types of porosity such as interparticle, intraparticle, moldic, vuggy, and fractures have been noticed. In addition to these different types of diagenetic features are represented mainly by cementation, dolomitization, recrystallization, and dissolution. The available log data for the wells Kz-11, Kz-14, and Kz-16 have been used in characterizing the reservoir properties of the studied formations. The detected lithologies from porosity logs showed domination of limestone, dolomitic limestone, and dolomites in addition to few thin beds of anhydrites in Jeribe Formation and thin beds of sand dominated lithologies in Azkand Formation. Clay content has been calculated from gamma ray log along the studied sections and appeared to be mostly of dispersed clay type as shown from density-neutron porosity crossplot of Thomas-Stieber. Correction from the effect of clay content has been done for all the measured sonic, density, and neutron porosities. The available porosity and permeability values which are measured from core tests in the well Kz-9 for the formations of Jeribe, Anah, and Azkand have been adapted to formalize the best equation for calculating permeability in the other studied wells which have no core test measurements but only log data (Kz-11, Kz-14, and Kz-16 wells). Depending on porosity, permeability, and shale content, the studied sections have been subdivided into seven reservoir units in the wells Kz-11 and Kz-16, and for eight reservoir units in the well Kz-14. 相似文献
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A general pattern for turbulent mixing in the upper layer of the South China Sea (SCS) is presented based on TurboMAP measurements in April and May 2010. The turbulence level decreased significantly overall from north to south, and weakened from east to west in the northern SCS. The average dissipation rate north of 18°N reaches 1.69 × 10?8 W/kg, approximately six times larger than that south of 18°N. The mean mixing efficiency in the SCS is 0.2, with a maximum of 0.31 near the Luzon Strait. At one repeatedly occupied station located in the central deep basin, the dissipation rate varies diurnally in the mixed layer and pycnocline due to diurnal heating and cooling by solar radiation and local barotropic tide, respectively. 相似文献
66.
Anatoly?AleksaninEmail author Vladimir?Kim Vasily?Kachur 《Journal of Oceanography》2016,72(5):801-810
Microwave satellite images used for retrieving sea surface temperatures often have such distortions as noise and blurring of the thermal fronts. An image processing approach based on the Mumford-Shah model of optimal image approximation is considered for the solution to this problem. We divide images into flat areas and frontal zones, and then process these areas separately. Image fragmentation is based on automatic detection of the thermal front lines. SST enhancement in frontal zones is achieved by using image deconvolution methods. It has been shown that SST errors in high gradient areas reach 1–3 °C. The proposed approach can decrease this discrepancy. 相似文献
67.
Yoshihisa?MinoEmail author Chiho?Sukigara Makio?C.?Honda Hajime?Kawakami Kazuhiko?Matsumoto Masahide?Wakita Minoru?Kitamura Tetsuichi?Fujiki Kosei?Sasaoka Osamu?Abe Jan?Kaiser Toshiro?Saino 《Journal of Oceanography》2016,72(6):819-836
Intensive observations using hydrographical cruises and moored sediment trap deployments during 2010 and 2012 at station K2 in the North Pacific Western Subarctic Gyre (WSG) revealed seasonal changes in δ 15N of both suspended and settling particles. Suspended particles (SUS) were collected from depths between the surface and 200 m; settling particles by drifting sediment traps (DST; 100–200 m) and moored sediment traps (MST; 200 and 500 m). All particles showed higher δ 15N values in winter and lower in summer, contrary to the expected by isotopic fractionation during phytoplankton nitrate consumption. We suggest that these observed isotopic patterns are due to ammonium consumption via light-controlled nitrification, which could induce variations in δ 15N(SUS) of 0.4–3.1 ‰ in the euphotic zone (EZ). The δ 15N(SUS) signature was reflected by δ 15N(DST) despite modifications during biogenic transformation from suspended particles in the EZ. δ 15N enrichment (average: 3.6 ‰) and the increase in C:N ratio (by 1.6) in settling particles suggests year-round contributions of metabolites from herbivorous zooplankton as well as TEPs produced by diatoms. Accordingly, seasonal δ 15N(DST) variations of 2.4–7.0 ‰ showed a significant correlation with primary productivity (PP) at K2. By applying the observed δ 15N(DST) vs. PP regression to δ 15N(MST) of 1.9–8.0 ‰, we constructed the first annual time-series of PP changes in the WSG. This new approach to estimate productivity can be a powerful tool for further understanding of the biological pump in the WSG, even though its validity needs to be examined carefully. 相似文献
68.
Zhao-Jun?LiuEmail authorView authors OrcID profile Shoshiro?Minobe Yoshi?N.?Sasaki Mio?Terada 《Journal of Oceanography》2016,72(6):905-922
The future regional sea level (RSL) rise in the western North Pacific is investigated by dynamical downscaling with the Regional Ocean Modeling System (ROMS) with an eddy-permitting resolution based on three global climate models—MIROC-ESM, CSIRO-Mk3.6.0, and GFDL-CM3—under the highest greenhouse-gas emission scenario. The historical run is forced by the air-sea fluxes calculated from Coordinated Ocean Reference Experiment version 2 (COREv2) data. Three future runs—ROMS-MIROC, ROMS-CSIRO, and ROMS-GFDL—are forced with an atmospheric field constructed by adding the difference between the climate model parameters for the twenty-first and twentieth century to fields in the historical run. In all downscaling, the RSL rise along the eastern coast of Japan is generally half or less of the RSL rise maxima off the eastern coast. The projected regional (total) sea level rises along the Honshu coast during 2081–2100 relative to 1981–2000 are 19–25 (98–104), 6–15 (71–80), and 8–14 (80–86) cm in ROMS-MIROC, ROMS-CSIRO, and ROMS-GFDL, respectively. The discrepancies of the RSL rise along the Honshu coast between the climate models and downscaling are less than 10 cm. The RSL changes in the Kuroshio Extension (KE) region in all downscaling simulations are related to the changes of KE (northward shift or intensification) with climate change. 相似文献
69.
In the southwestern United States, precipitation in the high mountains is a primary source of groundwater recharge. Precipitation patterns, soil properties and vegetation largely control the rate and timing of groundwater recharge. The interactions between climate, soil and mountain vegetation thus have important implications for the groundwater supply. This study took place in the Sacramento Mountains, which is the recharge area for multiple regional aquifers in southern New Mexico. The stable isotopes of oxygen and hydrogen were used to determine whether infiltration of precipitation is homogeneously distributed in the soil or whether it is partitioned among soil-water ‘compartments’, from which trees extract water for transpiration as a function of the season. The results indicate that “immobile” or “slow” soil water, which is derived primarily from snowmelt, infiltrates soils in a relatively uniform fashion, filling small pores in the shallow soils. “Mobile” or “fast” soil water, which is mostly associated with summer thunderstorms, infiltrates very quickly through macropores and along preferential flow paths, evading evaporative loss. It was found that throughout the entire year, trees principally use immobile water derived from snowmelt mixed to differing degrees with seasonally available mobile-water sources. The replenishment of these different water pools in soils appears to depend on initial soil-water content, the manner in which the water was introduced to the soil (snowmelt versus intense thunderstorms), and the seasonal variability of the precipitation and evapotranspiration. These results have important implications for the effect of climate change on recharge mechanisms in the Sacramento Mountains. 相似文献
70.
Pascale?A.?L.?GoertlerEmail author Charles?A.?Simenstad Daniel?L.?Bottom Susan?Hinton Lia?Stamatiou 《Estuaries and Coasts》2016,39(2):542-559
Estuarine rearing has been shown to enhance within watershed biocomplexity and support growth and survival for juvenile salmon (Oncorhynchus sp.). However, less is known about how growth varies across different types of wetland habitats and what explains this variability in growth. We focused on the estuarine habitat use of Columbia River Chinook salmon (Oncorhynchus tshawytscha), which are listed under the Endangered Species Act. We employed a generalized linear model (GLM) to test three hypotheses: (1) juvenile Chinook growth was best explained by temporal factors, (2) habitat, or (3) demographic characteristics, such as stock of origin. This study examined estuarine growth rate, incorporating otolith microstructure, individual assignment to stock of origin, GIS habitat mapping, and diet composition along ~130 km of the upper Columbia River estuary. Juvenile Chinook grew on average 0.23 mm/day in the freshwater tidal estuary. When compared to other studies in the basin our growth estimates from the freshwater tidal estuary were similar to estimates in the brackish estuary, but ~4 times slower than those in the plume and upstream reservoirs. However, previous survival studies elucidated a possible tradeoff between growth and survival in the Columbia River basin. Our GLM analysis found that variation in growth was best explained by habitat and an interaction between fork length and month of capture. Juvenile Chinook salmon captured in backwater channel habitats and later in the summer (mid-summer and late summer/fall subyearlings) grew faster than salmon from other habitats and time periods. These findings present a unique example of the complexity of understanding the influences of the many processes that generate variation in growth rate for juvenile anadromous fish inhabiting estuaries. 相似文献