成都平原地区城市湖泊生态需水计算方法研究——以锦城湖为例

成都市城市湖泊多形成于低洼滞洪区,湖泊水质安全受到外界干扰的影响较大。河湖生态补水是保障成都市河湖生态水质重要的措施。本次以锦城湖为例,对清水型和换水型两种湖泊需水类型计算了其不同时期的生态需水过程,解决了受人为因素影响较多的湖泊生态需水量计算的问题。通过本方法可实现城市湖泊建设近期与后期运营补水的相互协调,实现城市湖泊全生命周期的经济合理管控。

Study on inhomogeneous cooling behavior of extruded profile with unequal and large thicknesses during quenching using thermo-mechanical coupling model

The interfacial heat transfer coefficient between hot profile surface and cooling water was determined by using inverse heat conduction model combined with end quenching experiment. Then, a Deform-3 D thermo-mechanical coupling model for simulating the on-line water quenching of extruded profile with unequal and large thicknesses was developed. The temperature field, residual stress field and distortion of profile during quenching were investigated systematically. The results show that heat transfer coefficient increases as water flow rate increases. The peak heat transfer coefficient with higher water flow rates appears at lower interface temperatures. The temperature distribution across the cross-section of profile during quenching is severe nonuniform and the maximum temperature difference is 300 ℃ at quenching time of 3.49 s. The temperature difference through the thickness of different parts of profile first increases sharply to a maximum value, and then gradually decreases. The temperature gradient increases obviously with the increase of thickness of parts. After quenching, there exist large residual stresses on the inner side of joints of profile and the two ends of part with thickness of 10 mm. The profile presents a twisting-type distortion across the cross-section under non-uniform cooling and the maximum twisting angle during quenching is 2.78°.

Analysis of interaction between surface and sewer pipe system based on computational fluid dynamics

To verify the accuracy of weir and orifice formula and analyze the hydraulic characteristics of exchange flow in a manhole,a three-dimensional numerical model was proposed to assess the exchange flow rate between the surface and sewer pipe systems based on the real-world scale model.The hydrodynamic model is based on the three-dimensional Navier-Stokes equations including the standard k-εmodel for turbulence processes,and the volume of fluid(VOF)method for capturing the free surface.The results of the computational fluid dynamics(CFD)simulation are compared with the conventional overflow equations,showing that the weir and orifice formula is appropriate to determine the exchange flow rate between two systems in this specific study case.Streamlines and velocity contours at the center profile under both the inflow and surcharge conditions show that the exchange flow is directly related to the water level on the surface and the junction area between the manhole and right pipe.The results demonstrate the potential application of CFD in analyzing the interaction of urban flood flows,which can provide much clearer details of the interaction process.

Simulation of the Internal Transport Phenomena for PEM Fuel Cells with Different Modes of Flow

A numerical model for proton exchange membrane (PEM) fuel cell is developed, which can simulate such basic transport phenomena as gas-liquid two-phase flow in a working fuel cell. Boundary conditions for both the conventional and the interdigitated modes of flow are presented on a three-dimensional basis. Numerical techniques for this model are discussed in detail. Validation shows good agreement between simulating results and experimental data. Furthermore, internal transport phenomena are discussed and compared for PEM fuel cells with conventional and interdigitated flows. It is found that the dead-ended structure of an interdigitated flow does increase the oxygen mass fraction and decrease the liquid water saturation in the gas diffusion layer as compared to the conventional mode of flow. However, the cathode humidification is important for an interdigitated flow to acquire better performance than a conventional flow fuel cell.

A Typical Mode of Seasonal Circulation Transition: A Climatic View of the Abrupt Transition from Drought to Flood over the Middle and Lower Reaches of the Yangtze River Valley in the Late Spring and Early Summer of 2011

In this study, the seasonal transition of precipitation over the middle and lower reaches of the Yang-tze River Valley (YRV) from late spring to early summer is investigated. The results show that the seasonal transition of precipitation exhibits multi-modes. One of these modes is characterized by an abrupt transition from drought to flood (ATDF) over the middle and lower reaches of the YRV in the seasonal transition of precipitation. It is shown that the ATDF event from May to June 2011 is simply one prominent case of the ATDF mode. The ATDF mode exhibits an obvious decadal variability. The mode has occurred more frequently since 1979, and its amplitude has apparently strengthened since 1994. From the climatic view, the ATDF mode configures a typical seasonal circulation transition from winter to summer, for which the winter circulations are prolonged, and the summer circulations with the rainy season are built up early over the YRV.

Numerical Analysis of the Nonlinear Parameterization of Waves in Currents over a Submerged Sill with a Non-Hydrostatic Model

An investigation of the effects of a uniform current strength direction(following or opposing wave propagation) on the nonlinear transformation of irregular waves over a submerged trapezoidal sill is carried out using SWASH,a non-hydrostatic numerical wave model.The nonlinear parameters(i.e.,asymmetry,skewness,and kurtosis) are calculated,and the empirical formulas for these parameters are presented as a function of the local Ursell number based on the present numerical data measured.In the shoaling area of the submerged sill,the nonlinear characteristics of waves are more obvious when waves propagate in the same direction as the currents than when waves propagate in the opposite direction.Whereas nonlinear parameters grow with the strengthening of the following currents over the crest,they tend to decrease as the adverse current velocity increases over the crest area of the submerged sill.

Adsorption and Desorption of Praseodymium (Ⅲ) from Aqueous Solution Using D72 Resin

In this work, the feasibility of using a macroporous strong acid ion exchange resin (D72) as an adsorbent for praseodymium (Ⅲ) was examined. The adsorption behavior and mechanism were investigated with various chemical methods and IR spectrometry. The results showed that the loading of Pr (III) ions was strongly dependent on pH of the medium and the optimal adsorption condition is in HAc-NaAc medium with pH value of 3.0. Adsorption kinetics of Pr (III) ions onto D72 resin could be best described by pseudo-second-order model. The maximum adsorption capacity of D72 for Pr (Ⅲ) was evaluated to be 294 mg·g 1 for the Langmuir model at 298K. The apparent activation energy, E a , was 14.71 kJ·mol 1 . The calculated data of thermodynamic parameters, ΔSΘ value of 100 J·mol 1 ·K 1 and ΔHΘ value of 8.89 kJ·mol 1 , indicate the endothermic nature of the adsorption process, while a decrease of ΔGΘ with increasing temperature indicates the spontaneous nature of the adsorption process. Finally, Pr (Ⅲ) can be eluted by using 1.00 mol·L 1 HCl-0.50 mol·L 1 NaCl solution and the D72 resin can be regenerated and reused. Thomas model was successfully applied to experimental data to predict the breakthrough curves and to determine the characteristic parameters of the column useful for process design. The characterization before and after adsorption of Pr (Ⅲ) ions on D72 resin was conformed by IR.

B-SPLINE-BASED SVM MODEL AND ITS APPLICATIONS TO OIL WATER-FLOODED STATUS IDENTIFICATION

A method of B-spline transform for signal feature extraction is developed. With the B-spline, the log-signal space is mapped into the vector space. An efficient algorithm based on Support Vector Machine (SVM ) to automatically identify the water-flooded status of oil-saturated stratum is described. The experiments show that this algorithm can improve the performances for the identification and the generalization in the case of a limited set of samples.

A 10bit 100MS/s Pipelined ADC with an Improved 1.5bit/Stage Architecture

This paper presents a 10bit 100MS/s CMOS pipelined analog-to-digital converter （ADC） based on an improved 1.5bit/stage architecture. The ADC achieves a peak signal-to-noise-and-distortion ratio （SNDR） of 57dB and maintains 51dB up to 57MHz, the Nyquist frequency for a clock rate of 100Msample/s. The differential non-linearity （DNL） and integral non-linearity （INL） are typically measured as 0.3LSB and 1.0LSB, respectively. The ADC is implemented in a 0.18μm mixed-signal CMOS technology and occupies 0.76mm^2.

Delayed cementless total hip arthroplasty for neglected dislocation of hip combined with complex acetabular fracture and deficient bone stock

Total hip arthroplasty （THA） for an un- treated acetabular fracture is technically challenging and the long-term result is not so favorable. A 45-year-old fe- male patient with untreated column and comminuted poste- rior wall fracture of the acetabulum was treated in our insti- tution by reconstruction of the posterior wall using iliac strut autograft and plate stabilization of the posterior col- umn with cancellous grafting and cementless THA in a single stage. At 3 years＇ follow-up, the patient was independently mobile without limb length discrepancy. Radiological evalu-ation showed well integrated components and bone grafts. No evidence of aseptic loosening or osteolysis was found. This report aims to emphasize that bony acetabular recon- struction allows the use of primary hip components, which improves prosthesis longevity and preserves bone stock for a future revision.