大学英语教材建设的原则

布鲁纳的知识结构理论和“螺旋”式的教材组织形式以及加涅的“层级”式原则对大学英语教材建设具有重要的指导作用,其作用主要表现在课文题材的编写自觉或不自觉地遵循了认知规律和螺旋型及层级式的组织形式并进行有系统的排列。在教材编写过程中,除了循序渐进、趣味性、多样性、现代性、实用性原则外,还要遵循系统、交际、认知、文化和情感等原则。

Numerical simulation of heat transfer enhancement by strip-coil-baffles in tube-bundle for a tube-shell heat exchanger

A novel strip-coil-baffle structure used to enhance heat transfer and support the tube bundle for a tube-shell heat exchanger is proposed. The new structure can sleeve the tubes in bundle alternatively to create a vortex flow in a heat exchanger. The numerical simulation on the flow and heat transfer characteristics for this new structure heat exchanger is conducted. The computational domain consists of two strip-coil sleeved tubes and two bare tubes oppositely placed at each comer of a square. The velocity and temperature fields in such strip-coil-baffled channel are simulated using FLUENT software. The effects of the strip-coil-baffles on heat transfer enhancement and flow resistance in relation to the Reynolds number are analyzed. The results show that this new structure bundle can enhance the heat transfer coefficient up to a range of 40% to 55% in comparison with a bare tube bundle; meanwhile, higher flow resistance is also accompanied. It is believe that the strip-coil- baffled heat exchanger should have promising applications in many industry fields.

Numerical Simulation and Experimental Study on the Performance of Gas/liquid Spiral Separator

The gas/liquid spiral separator, a key component in the compressed air system, was used to remove liquid and oil from gas stream by centrifugal and gravitational forces. To optimize the design of the separator,the relationship between the performance and structural parameters of separators is studied. Computational fluid dynamics (CFD) method is employed to simulate the flow fields and calculate the pressure drop and separation efficiency of air-liquid spiral separators with different structural parameters. The RSM (Reynolds stress model)turbulence model is used to analyze the highly swirling flow fields while the stochastic trajectory model is used to simulate the traces of liquid droplets in the flow field. A simplified calculation formula of pressure drop in spiral structures is obtained by modifying Darcy's equation and verified by experiment.

Experimental Research on Gas-Liquid Two-Phase Spiral Flow in Horizontal Pipe

In view of the importance of gas-liquid two-phase spiral flow and the few research reports at home and abroad,the gas-liquid two-phase spiral flow patterns have been researched in a horizontal pipe with different parameters investigated by means of observation and a high-speed camera.Since the appearance of spiral flow makes the distribution of twophase flow more complicated,the flow patterns appearing in the experiments were divided into the Spiral Wavy Stratified Flow(SWS),the Spiral Bubble Flow(SB),the Spiral Slug Flow(SS),the Spiral Linear Flow(SL),the Spiral Axial Flow(SA),and the Spiral Dispersed Flow(SD) by the observations and with reference to the predecessors' research achievements.A flow pattern map has been drawn up.The influence of velocity,vane angle and vane area on flow pattern conversion boundary and pressure drop has been studied,with a solid foundation laid for the future research work.

Dyestuff wastewater treatment by combined SDS-CuO/TiO_2 photocatalysis and sequencing batch reactor

Combined technology of SDS-CuO/TiO2 photocatalysis and sequencing batch reactor （SBR） were applied to treating dyestuff wastewater. Photocatalysis was carried out in a spiral up-flow type reactor as pre-treatment. SDS-CuO/TiO2 photocatalyst was prepared by modification of nano-TiO2 using CuO and sodium dodecyl sulfate （SDS）. Results show that the SDS-CuO/TiO2 photocatalyst contains two kinds of crystals, including TiO2 and CuO. The band gap of this photocatalyst is 1.56 eV, indicating that it can be excited by visible light （2〈794.87 nm）. And characterization also shows that there are alkyl groups on its surface. It takes 40 rain to improve the biodegradability of dyestuff wastewater. Five-day biochemical oxygen demand （BODs） and dehydrogenase activity （DHA） of wastewater reach the maximum value when dissolved oxygen is higher than 2.97 mg/L. SBR reactor was used to treat this biodegradability improved wastewater. Chemical oxygen demand （COD） and colority decline to 72 mg/L and 20 times, respectively, when the sludge loading is 0.179 kg（COD）/[kg（MLSS）＇d], dissolved oxygen is 4.09 mg/L and aeration time is 10 h.

Performance Analysis of Slowed Rotor Compound Helicopter

The performance of slowed-rotor compound aircraft,particularly at high-speed flight condition,is examined.The forward flight performance calculation model of the composite helicopter is established,and the appropriate wing and propeller parameters are determined.The predicted performance of isolated propeller,wing and rotor combination is examined.Three kinds of tip speed and a range of load share setting are investigated.Propeller bearing 80%of the thrust with wing sharing lift is found to be the best condition to have better performance and the maximum L/D for maximum forward speed.Detailed rotor,propeller,and wing performance are examined for sea level,1000 m,and 2000 m cruise altitude.Rotor,propeller,and wing power are found to be largely from profile drag,except at low speed where the wing is near stall.Increased elevation offloads lift from the rotor to the wing,dropping the total power required and increasing the maximum speed limit over 400 km/h.

Multi-mode Spiral Wave in a Coupled Oscillatory Medium

Multi-mode spiral wave and its breakup in 1-d and 2-d coupled oscillatory media is studied here by theoretic analysis and numerical simulations. The analysis in 1-d system shows that the dispersion relation curve could be nonmonotonic depending on the coupling strength. It may also lead to the coexistence of different wave numbers within one system. Direct numerical observations in 1-d and 2-d systems conform to the prediction of dispersion relation analysis. Our findings indicate that the wave grouping can also be observed in oscillatory media without tip meandering and waves with negative group velocity can occur without inhomogeneity.

Regulation Conditions Influence on the Thermic and Exergic Efficiency Factors Size with the Heat Exchanger of a Coiled Type

The thermal engineering research has been executed for the threecircuit heat exchanger of a coiled type, that provides the thermal loads regulation for the heating and hot water supply systems. A processing curve of the warmth supply regulation at a combined heating and hot water supply load, was used at that. It is important to know the processes running inside the apparatus for the technical characteristics improvement of the threecircuit heat exchanger of a coiled type. The task solution will allow save the materials consumption for the threecircuit heat exchangers of a coiled type manufacturing in the future.

Exploration and determination of the principles of rotary-percussive underground slimhole drilling

A possibility of the efficient use of rotary percussive drilling to provide drilling smaller diameter holes(40–70 mm) both in mining and prospecting is disclosed herein. A new construction designed for the nipple thread connection is described. The relative amplitude variation, change of power pulse time and energy in their propagation throughout the drilling tool are determined. A possibility of the efficient power pulse transfer along the drill string to the rock destruction tools with new nipple connections which allow automating the make-up and breakout system of drill pipe was supported by experiments.

Application of imaging postprocessing of spiral CT in the staging of lung cancer

Objective： To evaluate the role of spiral CT imaging postprocessing techniques in preoperative TNM staging of lung cancer. Methods： 106 patients with pathologically confirmed lung cancer received spiral CT examinations with a new revised TNM staging method of lung cancer which was taken as criterion of diagnosis. The images were reconstructed by using different postprocessing techniques such as MPR, MIP, SSD, VR, and their TNM staging capabilities were assessed by using postprocessing imaging and the results with axial CT images were compared. Results： In T staging, the accurate rates of axial CT images in T1-T4 staging were 77.3%, 60.6%, 60.7%, and 60.3% respectively; for postprocessing images, the accurate rates were 86.4%, 90.9%, 89.3%, and 87.0% respectively, In N staging, the accurate rates of axial CT images were 84.6%, 68.1%, 63.6%, and 64.2% in N0-N3 staging, respectively; but they were 92.3%, 90.9%, 90.9%, and 85.7% in postprocessing images, respectively. The postprocessing images were superior to axial CT images in T1-T3 and N1-N3 staging of lung cancer but there were no significant differences in T1 and NO staging. For metastasis, the postprocessing images may be helpful for the TNM staging of lung cancer. Conclusion： The postprocessing techniques of the spiral CT could improve the accurate rates of TNM staging of lung cancer, and represent a useful complement to the axial CT.

Helicity Amplitude Analysis of η_c Decays into Hyperon-Antihyperon Pairs

The helicity amplitudes for the processes of e^＋e^- →J/ψ→γηc→γYY（Y： hyperon） are presented, together with the joint angular distributions for ηc decays into ∧∧,∑^0 ∑^0, and [1]-[1]＋. The sensitivities to measure the hyperon decay parameters in these decays are evaluated based on the helicity amplitudes. The prospects to test the Bell inequality in experiment using the decay of ηc→∧∧ are discussed.

Computational Simulation of Complex Structure Fancy Yarns

A study is reported for mathematical model and simulative of complex structure fancy yams. The investigated complex structure fancy yams have a multithread structure composed of three components core, effect, and binder yams. In current research the precondition was accepted that the cross-sections of the both two yams of the effect intermediate product in the complex structure fancy yam remain the circles shaped, and this shape does not change during manufacturing of the fancy yam. Mathematical model of complex structure fancy yarn is established based on parameter equation of space helix line and computer simulative is further carried out using the computational mathematical tool Matlab 6.5. Theoretical structure of fancy yam is compared with an experimental sample. The simulative system would help for further the set of informative in designing of new assortment of the complex structure fancy yarns and prediction of visual effects of fancy yams in end-use fabrics.

Low frequency wide bandwidth MEMS energy harvester based on spiral-shaped PVDF cantilever

In this paper,a piezoelectric energy harvester based on spiral-shaped polyvinylidene fluoride(PVDF)cantilever is designed and fabricated for harvesting low frequency vibration energy in the environment.In this design,the spiral-shaped PVDF cantilever is major for lowering the resonant frequency by increasing the length of the cantilever;Copper and silicon proof masses on both sides are working on further decreasing the resonant frequency and widen its bandwidth.Due to the high flexibility of the PVDF cantilever,this device is extremely sensitive to vibration and can harvest weak vibration energy.Both simulation and experimental results have approved that this device can operate at very low frequency which is about 20 Hz and can effectively harvest energy from 15–50 Hz.The peak of the output voltage can reach 1.8 V with the acceleration of 0.2 g.This is a promising harvester for powering the wireless sensors in the future.

Study on the Rotor Design Method for a Small Propeller-Type Wind Turbine

Small propeller-type wind turbines have a low Reynolds number,limiting the number of usable airfoil materials.Thus,their design method is not sufBciently established,and their performance is often low.The ultimate goal of this research is to establish high-performance design guidelines and design methods for small propeller-type wind turbines.To that end,we designed two rotors:Rotor A,based on the rotor optimum design method from the blade element momentum theory,and Rotor B,in which the chord length of the tip is extended and the chord length distribution is linearized.We examined performance characteristics and flow fields of the two rotors through wind tunnel experiments and numerical analysis.Our results revealed that the maximum output tip speed ratio of Rotor B shifted lower than that of Rotor A,but the maximum output coefficient increased by approximately 38.7%.Rotors A and B experienced a large-scale separation on the hub side,which extended to the mean in Rotor A.This difference in separation had an impact on the significant decrease in Rotor A's output compared to the design value and the increase in Rotor B's output compared to Rotor A.

Unsteady Flow at Low Flow-rate Region in a Semi-open Propeller Fan (Velocity Fluctuation outside of Blade Tip)

In order to clarify the unsteady flow fields at low flow-rate region with positive gradient on pressure-flow-rate curve,the experimental investigation was carried out at rotor inlet and outside of rotor blade tip without casing in a semi-opened propeller fan using a hot-wire anemometer.A single I-type hot-wire probe was used,and the data obtained were processed by the use of phase-locked averaging,ensemble averaging and FFT analyzing.The flow fields at rotor inlet and outside of rotor blade tip were discussed mainly using the results from distributions of velocity fluctuations and power spectrum density.It was found from these results that there are the two types of different periodical fluctuations and both of those frequencies were not the same of rotor rotating frequency(RRF;15Hz).One was observed at relatively high flow-rate region at relatively downstream area in measurement and its frequency was approximately 7Hz(47% of RRF).The other was observed at relatively low flow-rate region at relatively upstream area in measurement and its frequency was approximately 10Hz(67% of RRF)".As the velocity fluctuations with the flow fields are rapidly increased by the former fluctuation,it is thought that its fluctuation is the trigger of blade stall.