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Planform evolution of deltas with graded alluvial topsets: Insights from three‐dimensional tank experiments,geometric considerations and field applications 
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下载免费PDF全文 Tetsuji Muto Ryuji Furubayashi Arti Tomer Tomoyuki Sato Wonsuck Kim Hajime Naruse Gary Parker 《Sedimentology》2016,63(7):2158-2189
The profile of a river that conveys sediment without net deposition and net erosion is referred to as ‘graded’ with respect to vertical aggradation of the river segment. Three experimental series, designed in terms of the autostratigraphic view of alluvial grade, were conducted to clarify the diagnostic spatial behaviour of graded alluvial–deltaic rivers: an ‘R series’, which utilized a moving boundary setting with a stationary base level; an ‘F series’ in a fixed boundary setting with a stationary base level to produce ‘forced grade’; and an ‘M series’ in a moving boundary setting with constant base‐level fall to produce ‘autogenic grade.’ The results of the three experimental series, combined with geometrical modelling of the effects of basin water depth and other experimental data, suggest the following: (i) in a graded alluvial–deltaic system, lateral shifting and avulsing of active distributary channels are suppressed regardless of whether the downstream boundary of the deltaic system is fixed; (ii) in a delta with a downstream‐fixed boundary, the graded streams are stabilized within a valley that is incised in the axial part of the delta plain, whereby the alluvial plain outside the valley is abandoned and terraced; (iii) in moving boundary settings, the graded river simply extends basinward as a linearly elongated channel and lobe system without cutting a valley; and (iv) a modern forced‐graded alluvial river is most likely to be found in a valley incised into a fan delta in front of very deep water, and the stratigraphic signal of fossil autogenic‐graded rivers will be found in deltaic successions that accumulated in the outer to marginal areas of deltaic continental shelves during sea‐level falls. This renewed autostratigraphic view of alluvial grade suggests a thorough reconsideration of the conventional understanding that an alluvial river feeding a progradational delta is graded with a stationary base level. 相似文献
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Sohan Lal A. Joshi Sandeep Monu Tomer Parveen Kumar Chun-Hsiang Kuo Che-Min Lin Kuo-Liang Wen M. L. Sharma 《Acta Geophysica》2018,66(4):461-477
On 25th April, 2015 a hazardous earthquake of moment magnitude 7.9 occurred in Nepal. Accelerographs were used to record the Nepal earthquake which is installed in the Kumaon region in the Himalayan state of Uttrakhand. The distance of the recorded stations in the Kumaon region from the epicenter of the earthquake is about 420–515 km. Modified semi-empirical technique of modeling finite faults has been used in this paper to simulate strong earthquake at these stations. Source parameters of the Nepal aftershock have been also calculated using the Brune model in the present study which are used in the modeling of the Nepal main shock. The obtained value of the seismic moment and stress drop is 8.26 × 1025 dyn cm and 10.48 bar, respectively, for the aftershock from the Brune model .The simulated earthquake time series were compared with the observed records of the earthquake. The comparison of full waveform and its response spectra has been made to finalize the rupture parameters and its location. The rupture of the earthquake was propagated in the NE–SW direction from the hypocenter with the rupture velocity 3.0 km/s from a distance of 80 km from Kathmandu in NW direction at a depth of 12 km as per compared results. 相似文献
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Tomer Duman Gabriel G. Katul Mario B. Siqueira Massimo Cassiani 《Boundary-Layer Meteorology》2014,152(1):1-18
An extended Lagrangian stochastic dispersion model that includes time variations of the turbulent kinetic energy dissipation rate is proposed. The instantaneous dissipation rate is described by a log-normal distribution to account for rare and intense bursts of dissipation occurring over short durations. This behaviour of the instantaneous dissipation rate is consistent with field measurements inside a pine forest and with published dissipation rate measurements in the atmospheric surface layer. The extended model is also shown to satisfy the well-mixed condition even for the highly inhomogeneous case of canopy flow. Application of this model to atmospheric boundary-layer and canopy flows reveals two types of motion that cannot be predicted by conventional dispersion models: a strong sweeping motion of particles towards the ground, and strong intermittent ejections of particles from the surface or canopy layer, which allows these particles to escape low-velocity regions to a high-velocity zone in the free air above. This ejective phenomenon increases the probability of marked fluid particles to reach far regions, creating a heavy tail in the mean concentration far from the scalar source. 相似文献
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Tomer Goodovitch 《GeoJournal》1994,34(4):499-505
This article analyzes the basic structure of aviation in the Middle East and the development possibilities as a result of Israeli-Palestinian cooperation consequent to the peace process. This paper is a first attempt at estimating the advantages and disadvantages of such cooperation to the Israeli and Palestinian economies. In addition, the research leads to an initial formulation of how to maximize the benefits for both parties.Israeli-Palestinian cooperation offers more than objective economic advantages; such cooperation can also form a functional base for a political-policy framework. In economic terms, both sides can benefit from economies of scale and more efficient utilization of the existing facilities, thus avoiding the waste of valuable resources in establishing two sets of aviation facilities. However these economic criteria are not the only advantage of cooperation. In fact, critical operational and security requirements exist as well, both in terms of passenger security and safety, where air traffic control requiring coordination in a limited airways system. Furthermore, trends in the air travel market point to future bilateral agreements on the basis of blocs of nations and not individual countries. Therefore, Isreali-Palestinian cooperation would enable Israel to maintain the existing framework of favorable bilateral agreement with Europa and the United States.Cooperation of this kind is viable both economically and politically, as it avoids political conflicts by providing infrastructure on an equal basis to the Palestinians, either by lease or purchase of Israeli facilities. The primary advantage of joint ownership is that the Palestinians will save the development and construction costs of new infrastructure, while Israel can both develop the existing infrastructure and free funds for economic development. At the same it is possible to take advantage of economies of scale in order to reap the economic benefits of this process. 相似文献
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J. N. Pattan G. Parthiban V. K. Banakar A. Tomer M. Kulkarni 《Journal of Earth System Science》2008,117(2):113-119
Three sediment cores in a north-south transect (3°N to 13°S) from different sediment types of the Central Indian Ocean Basin
(CIOB) are studied to understand the possible relationship between magnetic susceptibility (χ) and Al, Fe, Ti and Mn concentrations.
The calcareous ooze core exhibit lowest χ (12.32 × 10−7 m3 kg−1), Al (2.84%), Fe (1.63%) and Ti (0.14%), terrigenous clay core with moderate χ (29.93 × 10−7 m3 kg−1) but highest Al (6.84%), Fe (5.20%) and Ti (0.44%), and siliceous ooze core with highest χ (38.06 × 10−7 m3 kg−1) but moderate Al (4.49%), Fe (2.80%) and Ti (0.19%) contents. The distribution of χ and detrital proxy elements (Al, Fe,
and Ti) are identical in both calcareous and siliceous ooze. Interestingly, in terrigenous core, the behaviour of χ is identical
to only Ti content but not with Al and Fe suggesting possibility of Al and Fe having a non-detrital source.
The occurrence of phillipsite in terrigenous clay is evident by the Al-K scatter plot where trend line intersects K axis at
more than 50% of total K suggesting excess K in the form of phillipsite. Therefore, the presence of phillipsite might be responsible
for negative correlation between χ and Al (r = −0.52). In siliceous ooze the strong positive correlations among χ, Alexc and Feexc suggest the presence of authigenic Fe-rich smectite. High Mn content (0.5%) probably in the form of manganese micronodules
is also contributing to χ in both calcareous and siliceous ooze but not in the terrigenous core where mean Mn content (0.1%)
is similar to crustal abundance. Thus, χ systematically records the terrigenous variation in both the biogenic sediments but
in terrigenous clay it indirectly suggests the presence of authigenic minerals. 相似文献
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Jacob Garty Tal Levin Haya Lehr Sharon Tomer Ayala Hochman 《Journal of Atmospheric Chemistry》2004,49(1-3):267-289
To assess the impact of ultraviolet B (UV-B) radiation under laboratory conditions on lichens from different biomonitoring sites, thalli of the lichen Ramalina lacera were transplanted from a clean air site to nine different polluted sites in Israel. Our objective was to determine the probability of synergistic/antagonistic effects on physiological parameters by considering two stressors: chemical contamination and UV-B. Exposure to both airborne pollutants in the field and subsequent UV-B radiation in the laboratory which led to a severe disintegration of cell membranes, followed by electrolyte leakage, indicate the probability of a synergistic effect. The impairment of the potential quantum yield of electron transfer through photosystem II (PSII) of photosynthesis indicated by a significant decrease of the ratio Fv/Fm, further demonstrated the synergistic effect of both chemical contamination and UV-B radiation. Besides enlarged amounts of stress-ethylene in lichens at contaminated sites, the reduced levels of ethylene production upon UV-B radiation in the present study suggest the likelihood of an antagonistic effect of xenobiotic elements and UV-B radiation as a result of an impaired ethylene-producing system. 相似文献
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Global and regional satellite navigation systems are constellations orbiting the Earth and transmitting radio signals for determining position and velocity of users around the globe. The state-of-the-art navigation satellite systems are located in medium Earth orbits and geosynchronous Earth orbits and are characterized by high launching, building and maintenance costs. For applications that require only regional coverage, the continuous and global coverage that existing systems provide may be unnecessary. Thus, a nano-satellites-based regional navigation satellite system in Low Earth Orbit (LEO), with significantly reduced launching, building and maintenance costs, can be considered. Thus, this paper is aimed at developing a LEO constellation optimization and design method, using genetic algorithms and gradient-based optimization. The preliminary results of this study include 268 LEO constellations, aimed at regional navigation in an approximately 1000 km \(\times \) 1000 km area centered at the geographic coordinates [30, 30] degrees. The constellations performance is examined using simulations, and the figures of merit include total coverage time, revisit time, and geometric dilution of precision (GDOP) percentiles. The GDOP is a quantity that determines the positioning solution accuracy and solely depends on the spatial geometry of the satellites. Whereas the optimization method takes into account only the Earth’s second zonal harmonic coefficient, the simulations include the Earth’s gravitational field with zonal and tesseral harmonics up to degree 10 and order 10, Solar radiation pressure, drag, and the lunisolar gravitational perturbation. 相似文献
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