Effect of thickness of planar nozzles on erosion depth of levee soils subjected to plunging water     

Chung Rak Song  Jinwon Kim  James Tyler Kidd  Alexander Cheng  David Admiraal 《国际泥沙研究》2018,33(3):243-249

In this study, the effect of the thickness of a planar jet on the erosion depth when the jet impinges on a surface composed of cohesive soil was analytically and numerically evaluated. The results showed that the erosion depth was practically independent of the nozzle thickness for erosion depths shallower than the potential core length (i.e. the region of the jet in which the central flow velocity is the same as the nozzle velocity). The relation between nozzle thickness and erosion depth was non-linear with continuously variable slope for erosion depths deeper than the potential core length. Finally, the relation was approximately linear when the erosion depth converged to the equilibrium erosion depth. The findings of this study indicate that direct and fast prediction of the erosion depth in the field is possible using the data from a small scale soil erosion test with similar flow velocities.  相似文献   

SHRIMP U–Pb ages of detrital zircons from the Early Cretaceous Nakdong Formation,South East Korea: Timing of initiation of the Gyeongsang Basin and its provenance          下载免费PDF全文

Tae‐Ho Lee  Kye‐Hun Park  Keewook Yi 《Island Arc》2018,27(5)

To constrain the depositional age of the lowermost Nakdong Formation in the Early Cretaceous Gyeongsang Basin, SHRIMP U–Pb age determination was carried out on zircon separates. The U–Pb compositions of detrital zircons from the Nakdong Formation yield a wide range of ages from the Archean to the Cretaceous but show a marked contrast in age distribution according to the geographical locations within the basin. The provenance of the southern Nakdong Formation is dominantly the surrounding Yeongnam Massif, which is composed of Paleoproterozoic metamorphic rocks and Triassic to Jurassic plutonic rocks, whereas the central to northern Nakdong Formation records significant sediment derivation from the Okcheon Metamorphic Belt, which is distributed to the northwest, in addition to the contribution from the Yeongnam Massif. It is suggested that the maximum depositional age of the Nakdong Formation is ca 127 Ma, based on its youngest detrital zircon age population. The onset of its deposition at 127 Ma coincided with the tectonic inversion in East Asia from a compressional to an extensional geodynamic setting, probably due to the contemporaneous change in the drift direction of the Izanagi Plate and its subsequent oblique subduction.  相似文献   

A stochastic multivariate framework for modeling movement of discrete sediment particles in open channel flows   总被引：1，自引：1，他引：0  

Jungsun?Oh  Christina?W.?TsaiEmail author 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(2):385-399

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Comparison between cyclic and dynamic rocking behavior for embedded shallow foundation using centrifuge tests     

Kil-Wan Ko  Jeong-Gon Ha  Heon-Joon Park  Dong-Soo Kim 《Bulletin of Earthquake Engineering》2018,16(11):5171-5193

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Optimal seismic retrofit model for steel moment resisting frames with brittle connections     

Hyo Seon Park  Se Woon Choi  Byung Kwan Oh 《地震工程与工程振动(英文版)》2018,17(4):835-847

Based on performance-based seismic engineering, this paper proposes an optimal seismic retrofit model for steel moment resisting frames (SMRFs) to generate a retrofit scheme at minimal cost. To satisfy the acceptance criteria for the Basic Safety Objective (BSO) specified in FEMA 356, the minimum number of upgraded connections and their locations in an SMRF with brittle connections are determined by evolutionary computation. The performance of the proposed optimal retrofitting model is evaluated on the basis of the energy dissipation capacities, peak roof drift ratios, and maximum interstory drift ratios of structures before and after retrofitting. In addition, a retrofit efficiency index, which is defined as the ratio of the increment in seismic performance to the required retrofitting cost, is proposed to examine the efficiencies of the retrofit schemes derived from the model. The optimal seismic retrofit model is applied to the SAC benchmark examples for threestory and nine-story SMRFs with brittle connections. Using the retrofit efficiency index proposed in this study, the optimal retrofit schemes obtained from the model are found to be efficient for both examples in terms of energy dissipation capacity, roof drift ratio, and maximum inter-story drift ratio.  相似文献   

A nearly analytic symplectic partitioned Runge–Kutta method based on a locally one-dimensional technique for solving two-dimensional acoustic wave equations     

Chol Sim  Chunyou Sun  Nam Yun 《Geophysical Prospecting》2020,68(4):1253-1269

In this paper, we develop a new nearly analytic symplectic partitioned Runge–Kutta method based on locally one-dimensional technique for numerically solving two-dimensional acoustic wave equations. We first split two-dimensional acoustic wave equation into the local one-dimensional equations and transform each of the split equations into a Hamiltonian system. Then, we use both a nearly analytic discrete operator and a central difference operator to approximate the high-order spatial differential operators, which implies the symmetry of the discretized spatial differential operators, and we employ the partitioned second-order symplectic Runge–Kutta method to numerically solve the resulted semi-discrete Hamiltonian ordinary differential equations, which results in fully discretized scheme is symplectic unlike conventional nearly analytic symplectic partitioned Runge–Kutta methods. Theoretical analyses show that the nearly analytic symplectic partitioned Runge–Kutta method based on locally one-dimensional technique exhibits great higher stability limits and less numerical dispersion than the nearly analytic symplectic partitioned Runge–Kutta method. Numerical experiments are conducted to verify advantages of the nearly analytic symplectic partitioned Runge–Kutta method based on locally one-dimensional technique, such as their computational efficiency, stability, numerical dispersion and long-term calculation capability.  相似文献   

Field investigation of siltation at a tidal harbor: North Port of Incheon,Korea     

Lee  Guan-hong  Shin  Hyun-Jung  Kim  Young Taeg  Dellapenna  Timothy M.  Kim  Kuk Jin  Williams  Joshua  Kim  Seok-Yun  Figueroa  Steven Miguel 《Ocean Dynamics》2019,69(9):1101-1120

Ocean Dynamics - To understand siltation processes within the North Port of Incheon, Korea, this study estimated the sedimentation rate and then determined the dominant mechanisms for the...  相似文献   

Stripe-based fragility analysis of multispan concrete bridge classes using machine learning techniques     

Sujith Mangalathu  Jong-Su Jeon 《地震工程与结构动力学》2019,48(11):1238-1255

A framework for the generation of bridge-specific fragility curves utilizing the capabilities of machine learning and stripe-based approach is presented in this paper. The proposed methodology using random forests helps to generate or update fragility curves for a new set of input parameters with less computational effort and expensive resimulation. The methodology does not place any assumptions on the demand model of various components and helps to identify the relative importance of each uncertain variable in their seismic demand model. The methodology is demonstrated through the case study of a multispan concrete bridge class in California. Geometric, material, and structural uncertainties are accounted for in the generation of bridge numerical models and their fragility curves. It is also noted that the traditional lognormality assumption on the demand model leads to unrealistic fragility estimates. Fragility results obtained by the proposed methodology can be deployed in a risk assessment platform such as HAZUS for regional loss estimation.  相似文献   

Gibbs free energies of formation of RuO 2, IrO 2, and OsO 2: A high-temperature electrochemical and calorimetric study     

《Geochimica et cosmochimica acta》1997,61(24):5279-5293

The Gibbs free energies of formation of RuO ₂, OsO ₂ and IrO ₂ have been determined by measuring the chemical potentials of oxygen (μO ₂) defined by the reactions M +O ₂ = MO ₂,whereM =Ru, Os. or Ir, using an electrochemical method with calcia-stabilized zirconia (CSZ) solid electrolytes. Measurements were attempted in the temperature ranges from ∼870 K to 1620, 1270, and 1415 K for the Ru, Os, and Ir equilibria, respectively, but inspection of the results reveals that equilibrium could not be established below ∼930 K for all three reactions. For Ru + RuO ₂, the highest temperature data (above 1520 K) may be systematically affected by the onset of significant electronic conduction in the CSZ electrolyte, while the attempted measurements of the Os + OsO ₂ equilibrium above 1190 K are obscured by the disproportionation of OsO ₂ to gaseous Os oxides.The high temperature heat capacities at constant pressure (C_p) of RuO ₂ and IrO ₂ were determined from 370 to 1070 K by differential scanning calorimetry. These data were combined with heat content measurements and low-temperature heat capacities from the literature, and fitted to an extended Maier-Kelley equation. The calorimetric data for RuO ₂ and IrO ₂, together with assessed data for Ru, Os, and Ir metals and estimated data for OsO ₂, were used in a third law analysis of the electrochemical measurements.The values of μO ₂ of the three equilibria were smoothed and filtered by the third-law analysis to yield the following equations which can be extrapolated to lower and higher temperatures as indicated: μO ₂ (Ru + RuO ₂) = −324563 + 344.151 T−22.1155 TlnT (700 ⩽ T ⩽ 1800) μO ₂ (Os + OsO ₂) = −300399 + 307.639 T−17.4819 TlnT (700 ⩽ T ⩽ 1500) μO ₂ (Ir + IrO ₂) = −256518 + 295.854 T−15.2368 TlnT (700 ⩽ T ⩽ 1500) where μO ₂ is in J mol ⁻¹, T is in K, the reference pressure for O ₂ is 1 bar (10 ⁵ Pa), and estimated accuracies are approximately 200 to 400 J mol ⁻¹. For Ru + RuO ₂, the drift in the measurements relative to the calorimetric data deduced from the third-law evaluation is 0.7 J K ⁻¹ mol ⁻¹, and for Ir + IrO ₂ is 1.6 J K ⁻¹ mol ⁻¹. The analogous third-law evaluation of the Os + OsO ₂ data gives S° _298K = 54.8 ± 0.7J K ⁻¹mol ⁻¹ and Δ _/tfH° _298K = −291.8 ± 0.6 kJ mol ⁻¹ for OsO ₂.  相似文献   

A general equation of state for supercritical fluid mixtures and molecular dynamics simulation of mixture PVTX properties     

《Geochimica et cosmochimica acta》1996,60(7):1209-1216

A general Equation of State (EOS), which we previously developed for pure nonpolar systems, is extended to polar systems such as water and to mixtures in this study. This EOS contains only two parameters for each pure component and two additional parameters for each binary mixture (no higher order parameters are needed for more complicated mixture systems). The two mixing parameters can be eliminated for nonaqueous mixtures with a slight loss of accuracy in both total mole volume and in excess volume (or nonideal mixing). Comparison with a large amount of experimental PVTX data in pure systems (including H₂O) and in the mixtures, H₂O-CO₂, CO₂-N₂, CH₄-CO₂, and N₂-CO₂-CH₄ results in an average error of 1.6% in density. Comparison with commonly used EOS for supercritical fluids shows that the EOS of this study covers far more T-P-X space with higher accuracy. We believe that it is accurate from supercritical temperature to 2000 K and from 0 to 25,000 bar or higher with an average error in density of less than 2% for both pure members and mixtures in the system H₂O-CO₂-CH₄-N₂-CO-H₂-O₂-H₂S-Ar and possibly with additional gases. Comparison with the published simulated data suggests that this EOS is approximately correct up to 300,000 bar and 2800 K.We also simulated the PVTX properties of a number of supercritical fluid mixtures using molecular dynamics (MD) simulation. These results and those of other authors are well predicted by the EOS of this study.  相似文献