摘要：In this paper,the CFD simulation and new flow unsteadiness analysis for a single-blade centrifugal pump with whole flow passage were carried *** periodic flow unsteadiness has been quantitatively investigated in detail by defining unsteady intensity and turbulence intensity in both rotor and volute domains under design condition Q=33 L s *** results show that the distributions of flow unsteadiness are the functions of impeller rotating angle and have complex unsteady *** obvious T u fluctuations can be also observed for different impeller *** addition,time-averaged unsteady intensity and time-averaged turbulence intensity were calculated by averaging the results of each mesh node for entire impeller revolution period to evaluate the strength distributions of flow unsteadiness directly and *** accumulative results of an impeller revolution can directly show the positions and strength of the flow unsteadiness and turbulence intensity in both rotor and stator domains which can be an important aspect to be considered in the single-blade pump optimum design procedure for obtaining more stable inner flow of the pump and decreasing flow-induced vibration and *** flow unsteadiness in the side chamber cannot be neglected for an accurate prediction of the inner flow of the pump,and the optimizing design procedure for a single-blade pump impeller will not be accurate using CFD tool if the unsteady flow phenomenon in the side chamber is not considered.

摘要：An OOK-NRZ visible light communication (VLC) system is designed by using a single white LED and a 550 nm visible photodetector. The emitting model of the single LED is established, and the general expression of the detector's output signals under OOK modulation is deduced. With the selected LED, detector and other related parameters, the designed communication system is optimized and its performance is analyzed. The optimized communication distance between the LED and the detector is 0.54 m at the communication bit rate of 1 Mbit/s. With the best communication distance, when the signal-to-noise ratio (SNR) is larger than 6.5 dB, the bit error rate (BER) can drop to 10-4. The analytical model and theory presented in this paper can be of certain practical meanings in the design of similar communication systems.

摘要：A new fabrication technology for three-dimensionally buried silica on silicon optical waveguide based on deep etching and thermal oxidation is presented. Using this method, a silicon layer is left at the side of waveguide. The stress distribution and effective refractive index are calculated by using finite element method and finite different beam propagation method, respectively. The results indicate that the stress of silica on silicon optical waveguide fabricated by this method can be matched in parallel and vertical directions and stress birefringence can be effectively reduced due to the side-silicon layer.

摘要：The design of counter-rotating turbine is one of new techniques to improve the thrust-weight ratio of jet propulsion *** analysis of a low pressure（LP）counter-rotating turbine rotor blade is presented by using ANSYS/CFX *** of aerodynamics and solid mechanics coupling in the computation is *** some rating of turbine,stress distribution and vibration characteristics of low pressure turbine（LPT）blade are *** wake aerodynamic forces and LPT blade vibration are transformed in frequency domain using fast Fourier transform（FFT）*** results show that under wake aerodynamic force excitation,the first order modal vibration is more easily aroused and the higher order response cannot be ***,with different temperature fields,the vibration responses of blade are also different.

摘要：In order to improve the performances of an 11 cm-diameter turbine engine,this article suggests to substitute a new-style micro diffuser redesigned based on a new concept for the traditional diffuser having poor performances. The new diffuser comprises integral blades and splitters,which are taken for a series of ducts in designing. This article investigates the effects of the cross-section area distribution along the flow path on the redesigned diffuser＇s performances. Having furnished with the new diffuser in place of the original vaned one,the 11 cm-diameter prototype engine is tested on the rig for its performances. CFD and experiments have shown that the improved diffuser with the unchanged original size has gained excellent performance parameters of pressure coefficient over 0.65 and total pressure recovery coefficient over 0.9. Equipped with the redesigned micro diffuser,the engine increases the thrust by 11% and decreases the specific fuel consumption by 9%.

摘要：In a centrifugal compressor, the leakage flow through the tip clearance generates the tip leakage vortex by the in- teraction with the main flow, and consequently makes the flow in the impeller passage more complex by the inte- raction with the passage vortex. In addition, the tip leakage vortex interacts with the shock wave on the suction surface near the blade tip in the transonic centrifugal compressor impeller. Therefore, the detailed examination for the influence of the tip leakage vortex becomes seriously important to improve the aerodynamic performance cs- pccia｜ly for the transonic centrifugal compressor. In this study, the flows in the transonic centrifugal compressor with and without the tip clearance at the design condition were analyzed numerically by using the commercial CFD code. The computed results revealed that the tip leakage vortex induced by the high loading at the blade tip around the leading edge affected the loss generation by the reduction or the suppression of the shock wave on the suction surface of the blade.

摘要：The buffeting performance of kilometer-level high-speed railway suspension bridges has a great impact on the smooth operation of high-speed *** investigate the buffeting performance of the structure significantly different from traditional suspension bridges,the first long-span high-speed railway suspension bridge,Wufengshan Yangtze River Bridge(WYRB),is taken as a numerical example to demonstrate the effects of structural parameters and wind field parameters on the buffeting *** on the design information,the spatial finite element model(FEM)of WYRB is established before testing its *** fluctuating wind fields are simulated via both classical and stochastic wave based spectral representation method(SRM).Finite element method is further taken to analyze the parametric sensitivity on wind induced buffeting responses in time *** results show that the vertical displacement is more sensitive to the changing dead load than the lateral and torsional *** larger stiffness of the main girder and the lower sag-to-span ratio are both helpful to reduce the buffeting *** spectrum and coherence function are key influencing factors to the responses so setting proper wind field parameters are essential in the wind-resistant design *** analytical results can provide references for wind resistance analysis and selection of structural and fluctuating wind field parameters for similar long-span high-speed railway suspension bridges.

摘要：This paper summarizes the experience that was gained during the construction of the 15.4 km long Ceneri Base Tunnel （CBT）, which is the southern part of the fiat railway line crossing the Swiss Alps from north to south. The project consisted of a twin tube with a diameter of 9 m interconnected by cross- passages, each 325 m long. In the middle of the alignment and at its southern end, large caverns were excavated for logistical and operational requirements. The total excavation length amounted to approx- imately 40 km. The tunnel crossed Alpine rock formations comprising a variety of rock typologies and several fault zones. The maximum overburden amounted to 850 m. The excavation of the main tunnels and of the cross-passages was executed by means of drill-and-blast （D＆B） excavation. The support con- sisted of bolts, meshes, fiber-reinforced shotcrete and, when required, steel ribs. A gripper tunnel boring machine （TBM） was used in order to excavate the access tunnel. The high overburden caused squeezing rock conditions, which are characterized by large anisotropic convergences when crossing weaker rock formations. The latter required the installation of a deformable support. At the north portal, the tunnel （with an enlarged cross-section） passed underneath the A2 Swiss highway （the major road axis connect- ing the north and south of Switzerland） at a small overburden and through soft ground. Vertical and sub- horizontal jet grouting in combination with partial-face excavation was successfully implemented in order to limit the surface settlements. The south portal was located in a dense urban area. The excavation from the south portal included an approximately 220 m long cut-and-cover tunnel, followed by about 300 m of D＆B excavation in a bad rock formation. The very low overburden, poor rock quality, and demanding crossing with an existing road tunnel （at a vertical distance of only 4 m） required special excavation methods through reduced sectors and special blastin

摘要：An alluvium with a sandy aquifer at the bottom,but lacking an effective impermeable layer between the sandy aquifer and bedrock is referred to as a special alluvial *** by the drainage of the aquifer due to mining activities,a shaft wall in this special alluvial stratum will be subject to a downward load by an additional vertical force which must be taken into consideration in the design of the shaft *** complexity of interaction between shaft wall and the surrounding walls makes it extremely difficult to determine this additional vertical *** a particular shaft wall in an extra-thick alluvium and assuming that the friction coefficient between shaft wall and stratum does not change with depth,an analysis of a numerical simulation of the stress within the shaft wall has been carried *** and size of the additional vertical stress have been obtained,based on specific values of the friction coefficient,the modulus of elasticity of the drainage layer and the thickness of the drainage ***, the safety of shaft walls with different structural types was studied and a more suitable structural design,providing an important basis for the design of shaft walls,is promoted.

摘要：Unexpected, serious deformation failures have occurred during construction of a main shaft. A study of construction parameters of the main shaft is required. First, the stability of the shaft and wall-rock is investigated by numerical methods. The modeling results are as follows： The convergence of shaft liner is greater than 60 mm at a depth of 650 m; the maximum principal stress in the liner approaches 190 MPa, which exceeds the strength of the liner, so it is inevitable that the liner deform locally. Second, stability analysis of shafts with different liner thicknesses has been completed. The results have the following features： If the depth where the liner thickness is increases from 400 mm to 500 mm is 650 meters, the convergence deformation of the liner is reduced by 3.4 mm while the maximum principal stress is reduced by 5 MPa. At a depth of 250 m if the liner thickness is increased from 400 mm to 500 mm the convergence of the liner is reduced by 1.5 mm while the maximum principal stress is reduced by 10 MPa. Therefore, increasing the liner thickness has little effect on liner convergence but can reduce the maximum principal stress in the liner. The thickness of the liner can be increased to reduce the maximum principal stress and increase the capacity for shear deformation. Finally, construction techniques employing releasing-displacements have been numerically simulated. The conclusions are that as the releasing displacement is increased the convergence of the surrounding rock increases linearly while the convergence of the lining decreases linearly. The plastic zone in the surrounding rock mass at first increases linearly but then, at a release-displacement of 95 ram, expands rapidly. These conclusions show that use of suitable releasing displacement can increase the self-supporting capacity of the surrounding rock. But when the releasing displacement exceeds 95 nun the plastic zone rapidly enlarges and stability rapidly decreases. The maximum principal st