Numerical simulation of sediment transport and bed evolution has become an important technique in the sediment research. In this article, a numerical model of suspended sediment transport was proposed, which was estab...Numerical simulation of sediment transport and bed evolution has become an important technique in the sediment research. In this article, a numerical model of suspended sediment transport was proposed, which was established in the vertical σ coordinate for fitting the free surface and bottom. In the research of the sediment transport, the predominant factors were found to be the eddy diffusion, the settling velocity, the bed condition and so on. By the aid of the model in the article, the contribution of the Rouse parameter to the vertical profile of sediment concentration was clarified, which was identical to the theoretical results. In the comparison of the numerical results with laboratory data, the agreement between experimental data and numerical results was reached except for some data. And the possible reasons for the disagreement were discussed.展开更多
In this research,aging treatments at temperatures of 800 and 900°C for different aging time of 5-60 min were conducted on solution treated as well as hot worked samples of 2205 dual phase stainless steel.The effe...In this research,aging treatments at temperatures of 800 and 900°C for different aging time of 5-60 min were conducted on solution treated as well as hot worked samples of 2205 dual phase stainless steel.The effect of aging treatment on precipitation of intermetallic phases was investigated in undeformed specimens and those subjected to hot deformation with different strain rates of 0.001-1 s-1.It was found that σ precipitation increased by hot working.It was also concluded that the volume fraction of phase increased with deformation temperature and decreased with strain rate.The precipitation of intermetallic phases（i.e.σ and χ） was analyzed by an Avrami-type kinetics equation of %（σ＋χ）=A（1-exp（-ktn）） and the values of n and ln k were estimated for different thermomechanical regimes.The values of n were assessed to increase from 0.4 to 1 with strain rate in the studied range.Otherwise,It was also understood that ln k decreased with strain rate.Microstructural observations by means of optical microscopy and scanning electron microscopy showed that σ particles mostly nucleated at the ferrite-austenite interfaces.But no sign of χ-phase could be seen.This fortified the idea of certain literature that χ-phase always forms at early stages of aging and consumes through the precipitation of σ.展开更多
A three dimensional numerical model in the σ coordinate system is developed to study the problem of waves. Turbulence effects are modeled by a subgrid scale (SGS) model with the concept of large eddy simulatio...A three dimensional numerical model in the σ coordinate system is developed to study the problem of waves. Turbulence effects are modeled by a subgrid scale (SGS) model with the concept of large eddy simulation (LES). The σ coordinate transformation is introduced to map the irregular physical domain of the wavy free surface and uneven bottom onto the regular computational domain of the shape of rectangular prism. The operator splitting method, which splits the solution procedure into the advection, diffusion, and propagation steps, is used to solve the modified Navier Stokes Equation. The model is used to simulate the propagation of solitary wave and wave passing over a submerged breakwater. Numerical results are compared with available analytical solutions and experimental data in terms of velocity profiles, free surface displacement, and energy conservation. Good agreement is obtained. The method is proved to be of high accuracy and efficiency in simulating surface wave propagation and wave structure interaction. It is suitable for the large and irregular physical domain, and requiring the non uniform grid system. The present work provides a foundation for further studies of random waves, wave structure interaction, wave discharge interaction, etc.展开更多
The precipitation kinetics of σ phase in commercial HR3C heat-resistant steel during aging at 650–800 °C was studied in the paper. Through morphology, composition and structural analyzing on the second phase in...The precipitation kinetics of σ phase in commercial HR3C heat-resistant steel during aging at 650–800 °C was studied in the paper. Through morphology, composition and structural analyzing on the second phase in the HR3C steel, it was confi rmed that the precipitations after aging were mainly NbCrN, M23C6 and FeCr type σ phase. The time-dependent mass change of the three precipitated phases showed that the linearly increased σ phase after aging at 750 °C–2000 h was transformed from NbCrN phase or M23C6 phase. According to the calculation on the volume fraction of electrolytically dyed σ phase, the time–temperature transformation(TTT) curve for σ phase at 1 vol% in two kinds of commercial HR3C steel(different in grain size) was obtained and analyzed. The nose of the TTT curve was located at around 750 °C for the two kinds of HR3C steel, and the larger grain size HR3C steel displayed a inhibit effect on the precipitation of σ phase. The impact energy of the HR3C steel after aging at 700 °C decreased obviously with the fracture mechanism changing from ductile fracture to intergranular brittle fracture, which was considered to be related to the density of σ-brittle phase after aging.展开更多
This paper shows the design of a second-order multi-bit△Σmodulator with hybrid structure for ADSL applications.A modified two phase non-overlapping clock generator is designed to let PH2 borrow 12%of the time from P...This paper shows the design of a second-order multi-bit△Σmodulator with hybrid structure for ADSL applications.A modified two phase non-overlapping clock generator is designed to let PH2 borrow 12%of the time from PH1,which relaxes the speed of OTAs,comparators and the DEM block.The clock feed through problem of the passive adder is solved by revising the timing of the comparators and the adder.The chip is designed and fabricated in UMC 0.18μm CMOS technology.Measurement results show that with an oversampling ratio of 32 and a clock rate of 80 MHz,the modulator can achieve 79 dB dynamic range,71.3 dB SNDR,11 mW power consumption from a 1.8 V power supply.The FOM is 1.47 pJ/step.展开更多
The characteristics of three-dimensional （3-D） tidal current in the Oujiang Estuary are investigated according to in situ observations. The Oujiang Estuary has features of irregular coastline, complex topography, ma...The characteristics of three-dimensional （3-D） tidal current in the Oujiang Estuary are investigated according to in situ observations. The Oujiang Estuary has features of irregular coastline, complex topography, many islands, moveable boundary, and submerged dyke, therefore, σ 3-D numerical model oil an unstructured triangular grid has been degeloped. The σ coordinate transforination, the moveable boundary and submerged dyke treatment techniques were employed in the model so it is suitable for the tidal simulations in the Oujing Estuary with submerged dyke and moveable boundary problems. The model is evaluated with the in situ data, and the results show that the calculated water elevations at 19 stations and currents at 19 profiler stations are in good agreement with measured data both in magnitude and phase. This numerical model is applied to the 3-D tidal circulation simulations of experiments in stopping flow transport through the South Branch of the Oujiang Estuary, and the feasibility to cutoff the flow in the South Branch of the Oujiang Estuary is demonstrated by numerical simulation experiments. The developed numerical model simulated the 3-D tidal current circulations in complicated coastal and estuarine waters very well.展开更多
The Co-Cr-W ternary system was critically assessed using the CALPHAD technique.The solution phases including the liquid,γ-Co,ε-Co and α-Cr were described by a substitutional solution model.The σ,μ and R phases we...The Co-Cr-W ternary system was critically assessed using the CALPHAD technique.The solution phases including the liquid,γ-Co,ε-Co and α-Cr were described by a substitutional solution model.The σ,μ and R phases were described by three-sublattice models of（Co,W）8（Cr,W）4（Co,Cr,W）18,（Co,Cr,W）7W2（Co,Cr,W）4 and（Co,W）27（Cr,W）14（Co,Cr,W）12,respectively,in order to reproduce their homogeneity ranges.A self-consistent set of thermodynamic parameters for each phase was derived.The calculated isothermal sections at 1 000,1 200 and 1 350 ℃ are in good agreement with the experimental data.A eutectoid reaction of R μ＋γ-Co＋σ in this ternary system was predicted to occur at 1 022 ℃.展开更多
A novel ^(99m)Tc labeled complex,[N-[2-((2-oxo-2-(4-(3-phenylpropyl)piperazin-1-yl)ethyl)(2-mercaptoethyl)amino)acetyl]-2-aminoethanethiolato]Technetium(Ⅴ) oxide (PPPE-MAMA''-^(99m)TcO)([^(99m)Tc]-2) has been...A novel ^(99m)Tc labeled complex,[N-[2-((2-oxo-2-(4-(3-phenylpropyl)piperazin-1-yl)ethyl)(2-mercaptoethyl)amino)acetyl]-2-aminoethanethiolato]Technetium(Ⅴ) oxide (PPPE-MAMA''-^(99m)TcO)([^(99m)Tc]-2) has been designed and prepared based on the integrated approach. The correspondingrhenium complex (PPPE-MAMA''-ReO)(Re-2) has been prepared and characterized. In vitro competitionbinding assays show moderate affinity of Re-2 towards σ_1 and σ_2 receptors with K_i values of8.67 ± 0.07 and 5.71 ± 1.88 μmol, respectively. Planar images obtained at 0.5 h, 4 h, 20 h afteri.v. injection indicate the accumulation of [^(99m)Tc]-2 in MCF-7 human breast tumor bearing mice at20 h. Furthermore, the accumulation of [^(99m)Tc]-2 has been inhibited at 20 h after co-injectionof [^(99m)Tc]-2 plus haloperidol (1 mg/kg). Biodistribution studies of [^(99m)Tc]-2 display an invivo tumor uptake of 0.14% ± 0.01% ID/g at 24 h post i.v. injection with a tumor/muscle ratio of6.02 ± 0.87. The above results suggest that [^(99m)Tc]-2, derived from a previously published leadcompound, retains certain tumor uptake and affinity for σ receptors. [^(99m)Tc]-2 may be used as abasis for further structural modifications to develop tumor imaging agents with high affinity for σreceptors.展开更多
文摘Numerical simulation of sediment transport and bed evolution has become an important technique in the sediment research. In this article, a numerical model of suspended sediment transport was proposed, which was established in the vertical σ coordinate for fitting the free surface and bottom. In the research of the sediment transport, the predominant factors were found to be the eddy diffusion, the settling velocity, the bed condition and so on. By the aid of the model in the article, the contribution of the Rouse parameter to the vertical profile of sediment concentration was clarified, which was identical to the theoretical results. In the comparison of the numerical results with laboratory data, the agreement between experimental data and numerical results was reached except for some data. And the possible reasons for the disagreement were discussed.
文摘In this research,aging treatments at temperatures of 800 and 900°C for different aging time of 5-60 min were conducted on solution treated as well as hot worked samples of 2205 dual phase stainless steel.The effect of aging treatment on precipitation of intermetallic phases was investigated in undeformed specimens and those subjected to hot deformation with different strain rates of 0.001-1 s-1.It was found that σ precipitation increased by hot working.It was also concluded that the volume fraction of phase increased with deformation temperature and decreased with strain rate.The precipitation of intermetallic phases（i.e.σ and χ） was analyzed by an Avrami-type kinetics equation of %（σ＋χ）=A（1-exp（-ktn）） and the values of n and ln k were estimated for different thermomechanical regimes.The values of n were assessed to increase from 0.4 to 1 with strain rate in the studied range.Otherwise,It was also understood that ln k decreased with strain rate.Microstructural observations by means of optical microscopy and scanning electron microscopy showed that σ particles mostly nucleated at the ferrite-austenite interfaces.But no sign of χ-phase could be seen.This fortified the idea of certain literature that χ-phase always forms at early stages of aging and consumes through the precipitation of σ.
文摘A three dimensional numerical model in the σ coordinate system is developed to study the problem of waves. Turbulence effects are modeled by a subgrid scale (SGS) model with the concept of large eddy simulation (LES). The σ coordinate transformation is introduced to map the irregular physical domain of the wavy free surface and uneven bottom onto the regular computational domain of the shape of rectangular prism. The operator splitting method, which splits the solution procedure into the advection, diffusion, and propagation steps, is used to solve the modified Navier Stokes Equation. The model is used to simulate the propagation of solitary wave and wave passing over a submerged breakwater. Numerical results are compared with available analytical solutions and experimental data in terms of velocity profiles, free surface displacement, and energy conservation. Good agreement is obtained. The method is proved to be of high accuracy and efficiency in simulating surface wave propagation and wave structure interaction. It is suitable for the large and irregular physical domain, and requiring the non uniform grid system. The present work provides a foundation for further studies of random waves, wave structure interaction, wave discharge interaction, etc.
基金financials support by National Natural Science Foundation of China (No. U1610256)the National High Technology Research and Development Program of China (The 863 Program) (No. 2015AA034402)the Dalian University of Technology Fundamental Research Fund (No. DUT17RC(3)010)
文摘The precipitation kinetics of σ phase in commercial HR3C heat-resistant steel during aging at 650–800 °C was studied in the paper. Through morphology, composition and structural analyzing on the second phase in the HR3C steel, it was confi rmed that the precipitations after aging were mainly NbCrN, M23C6 and FeCr type σ phase. The time-dependent mass change of the three precipitated phases showed that the linearly increased σ phase after aging at 750 °C–2000 h was transformed from NbCrN phase or M23C6 phase. According to the calculation on the volume fraction of electrolytically dyed σ phase, the time–temperature transformation(TTT) curve for σ phase at 1 vol% in two kinds of commercial HR3C steel(different in grain size) was obtained and analyzed. The nose of the TTT curve was located at around 750 °C for the two kinds of HR3C steel, and the larger grain size HR3C steel displayed a inhibit effect on the precipitation of σ phase. The impact energy of the HR3C steel after aging at 700 °C decreased obviously with the fracture mechanism changing from ductile fracture to intergranular brittle fracture, which was considered to be related to the density of σ-brittle phase after aging.
基金supported by the National High Technology Research and Development Program of China(No.2008AA010700)
文摘This paper shows the design of a second-order multi-bit△Σmodulator with hybrid structure for ADSL applications.A modified two phase non-overlapping clock generator is designed to let PH2 borrow 12%of the time from PH1,which relaxes the speed of OTAs,comparators and the DEM block.The clock feed through problem of the passive adder is solved by revising the timing of the comparators and the adder.The chip is designed and fabricated in UMC 0.18μm CMOS technology.Measurement results show that with an oversampling ratio of 32 and a clock rate of 80 MHz,the modulator can achieve 79 dB dynamic range,71.3 dB SNDR,11 mW power consumption from a 1.8 V power supply.The FOM is 1.47 pJ/step.
基金The Natural Science Foundation of Tianjin, China under contract No.08JCZDZT00200
文摘The characteristics of three-dimensional （3-D） tidal current in the Oujiang Estuary are investigated according to in situ observations. The Oujiang Estuary has features of irregular coastline, complex topography, many islands, moveable boundary, and submerged dyke, therefore, σ 3-D numerical model oil an unstructured triangular grid has been degeloped. The σ coordinate transforination, the moveable boundary and submerged dyke treatment techniques were employed in the model so it is suitable for the tidal simulations in the Oujing Estuary with submerged dyke and moveable boundary problems. The model is evaluated with the in situ data, and the results show that the calculated water elevations at 19 stations and currents at 19 profiler stations are in good agreement with measured data both in magnitude and phase. This numerical model is applied to the 3-D tidal circulation simulations of experiments in stopping flow transport through the South Branch of the Oujiang Estuary, and the feasibility to cutoff the flow in the South Branch of the Oujiang Estuary is demonstrated by numerical simulation experiments. The developed numerical model simulated the 3-D tidal current circulations in complicated coastal and estuarine waters very well.
基金Project(50771027)supported by the National Basic Research Program of ChinaProject(50771027)supported by the National Natural Science Foundation of China
文摘The Co-Cr-W ternary system was critically assessed using the CALPHAD technique.The solution phases including the liquid,γ-Co,ε-Co and α-Cr were described by a substitutional solution model.The σ,μ and R phases were described by three-sublattice models of（Co,W）8（Cr,W）4（Co,Cr,W）18,（Co,Cr,W）7W2（Co,Cr,W）4 and（Co,W）27（Cr,W）14（Co,Cr,W）12,respectively,in order to reproduce their homogeneity ranges.A self-consistent set of thermodynamic parameters for each phase was derived.The calculated isothermal sections at 1 000,1 200 and 1 350 ℃ are in good agreement with the experimental data.A eutectoid reaction of R μ＋γ-Co＋σ in this ternary system was predicted to occur at 1 022 ℃.
基金This work was supported by the National Natural Science Foundation of China (Grant Nos. 20471011 and 20501004).
文摘A novel ^(99m)Tc labeled complex,[N-[2-((2-oxo-2-(4-(3-phenylpropyl)piperazin-1-yl)ethyl)(2-mercaptoethyl)amino)acetyl]-2-aminoethanethiolato]Technetium(Ⅴ) oxide (PPPE-MAMA''-^(99m)TcO)([^(99m)Tc]-2) has been designed and prepared based on the integrated approach. The correspondingrhenium complex (PPPE-MAMA''-ReO)(Re-2) has been prepared and characterized. In vitro competitionbinding assays show moderate affinity of Re-2 towards σ_1 and σ_2 receptors with K_i values of8.67 ± 0.07 and 5.71 ± 1.88 μmol, respectively. Planar images obtained at 0.5 h, 4 h, 20 h afteri.v. injection indicate the accumulation of [^(99m)Tc]-2 in MCF-7 human breast tumor bearing mice at20 h. Furthermore, the accumulation of [^(99m)Tc]-2 has been inhibited at 20 h after co-injectionof [^(99m)Tc]-2 plus haloperidol (1 mg/kg). Biodistribution studies of [^(99m)Tc]-2 display an invivo tumor uptake of 0.14% ± 0.01% ID/g at 24 h post i.v. injection with a tumor/muscle ratio of6.02 ± 0.87. The above results suggest that [^(99m)Tc]-2, derived from a previously published leadcompound, retains certain tumor uptake and affinity for σ receptors. [^(99m)Tc]-2 may be used as abasis for further structural modifications to develop tumor imaging agents with high affinity for σreceptors.
