聚苯胺-邻甲基苯胺的热电性能研究

针对聚苯胺Seebeck系数较小的缺点提出通过在聚苯胺链段上引入邻位取代基的方法来提高其Seebeck系数。实验采用在酸性介质中氧化共聚的方法,通过改变单体苯胺和邻甲基苯胺的共聚比例,制备了一系列不同邻位甲基取代量的聚苯胺-邻甲基苯胺。用元素分析法测定共聚物的C、H、N质量分数,并计算出共聚物链段中取代甲基的平均含量;测定它们的电导率、Seebeck系数,并计算相应的ZT值,讨论了甲基取代对其热电性能的影响,结果表明,随着甲基取代量的增加,共聚物的电导率有小幅度的下降,但Seebeck系数有明显的增加,因此材料的热电性能随甲基取代有所增加。

Side force formation mechanism and change law of TBM center cutter

The center cutter of a hard rock tunnel boring machine(TBM) is installed on the cutterhead at a small radius and thus bears complex side force.Given this fact,the formation mechanism and change law of the side force suffered by the center cutter were studied.Based on the rock shear failure criterion in combination with the lateral rolling width,a model for predicting the average side force was set up.Besides,a numerical analysis model of the rock fragmentation of the center cutter was established,and the instantaneous load changing features were investigated.Results shows that the inner side of the center cutter can form lateral rolling annulus in rock during the rotary cutting process.The smaller the installation radius is,the greater the cutter side force will be.In a working condition,the side force of the innermost center cutter is 11.66 k N,while it decreases sharply when installation radius increases.Variation tends to be gentle when installation radius is larger than 500 mm,and the side force of the outermost center cutter is reduced to 0.74 k N.

SCISSORS DIFFERENCE AND ITS IMPACTS ON ECONOMIC VALUE OF CULTIVATED LAND IN CHINA

The problem of price scissors difference between industrial products and agricultural products is one of the important problems in China. It impacts not only the living standard improvement of farmers but also the economic value of cultivated land, furthermore results in the direct and indirect loss of cultivated land resources. China＇s cultivated land area has decreased dramatically in recent years. An important reason for the decrease is the relatively low cost of cultivated land occupancy, which results from the distortion of economic value of cultivated land due to the existence of scissors difference. This study firstly analyzed the dynamic change of scissors difference and calculated the absolute and relative magnitude of scissors difference from 1997 to 2002, then computed the economic value of cultivated land before and after scissors difference adjustment in 2002, and finally discussed the inverted scissors difference. Results suggest that the scissors difference has a remarkable impact on the economic value of cultivated land, and the adjustment of scissors difference even inverted scissors difference to the economic value of cultivated land is indisoensable.

A comparative analysis of 3D flow fields between straight and bowed blades in a steam turbine

A commercial Navier-Stokes flow solver has been employed for simulating steady subsonic flow characteristics and analyzing the comparative features of flow fields between straight and bowed blades applied to the stator of a high pressure steam turbine. For comparison, we have studied the effects of bowed blades on the wakes of stator trailing edge and horse shoe vortex in the rotor. It was found that the position of wakes for bowed blades is shifted toward the blade suction side. Also, we have discussed and compared the entropy generation and energy loss caused by dissipation mechanism within the boundary layers on the hub and shroud; and temperature gradient in meridional plane.

Rock Cutting Analysis Employing Finite and Discrete Element Methods

The petroleum industry has shown great interest in the study of drilling optimization on pre-salt formations given the low rates of penetration observed so far. Rate of penetration is the key to economically drill the pre-salt carbonate rock. This work presents the results of numerical modeling through finite element method and discrete element method for single cutter drilling in carbonate samples. The work is relevant to understand the mechanics of drill bit-rock interaction while drilling deep wells and the results were validated with experimental data raised under simulated downhole conditions. The numerical models were carried out under different geometrical configurations, varying the cutter chamfer size and back-rake angles. The forces generated on the cutter are translated into mechanical specific energy as this parameter is often used to measure drilling efficiency. Results indicate that the chamfer size does not change significantly the mechanical specific energy values, characteristic. Results also show there is a significant increase although the cutter aggressiveness is influenced by this geometrical in drilling resistance for larger values of back-rake angle.

Study on Chinese painting freehand brushwork

In art of the canvas, the brush stroke in Chinese painting and calligraphy is one of the important behavior means of the canvas, have independent aesthetic value at the same time, contemporary, one that is with pluralism, varied painting idea and painting skill and technique of art is great and abundant, traditional in the canvas works ＂ The brush stroke in Chinese painting and calligraphy ＂ Already not merely can be spoken to the limit by the simple scribbling and wiping of pen, and Chinese comfortable brush stroke in Chinese painting and calligraphy, technique of writing incorporate visual language and spiritual intension created that can enrich the picture greatly in the canvas is created. This text attempts to canvass the canvas and create the feasibility that incorporated into comfortable brush stroke in Chinese painting and calligraphy and expansionary from two respect factors of cultural idea and skill and technique and tool material.

Thermal Product of Type-E Fast Response Temperature Sensors

This paper provides practical data for thermal product values of different scratched temperature sensors that can be used for accurate transient heat transfer measurements under hypersonic flow conditions.The effect of using different scratch techniques(abrasive papers and scalpel blades)to form the sensor's junction is investigated.It was observed that the thermal product of a particular sensor depends on the Mach number,junction scratch technique, junction location and enthalpy conditions.It was demonstrated that using different scratched technique would produce different thermal product values.

Numerical analysis and experimental investigation of wind turbine blades with innovative features:Structural response and characteristics

Innovative features of wind turbine blades with flatback at inboard region,thick airfoils at inboard as well as mid-span region and transversely stepped thickness in spar caps have been proposed by Institute of Engineering Thermophysics,Chinese Academy of Sciences(IET-Wind)in order to improve both aerodynamic and structural efficiency of rotor blades.To verify the proposed design concepts,this study first presented numerical analysis using finite element method to clarify the effect of flatback on local buckling strength of the inboard region.Blade models with various loading cases,inboard configurations,and core materials were comparatively studied.Furthermore,a prototype blade incorporated with innovative features was manufactured and tested under static bending loads to investigate its structural response and characteristics.It was found that rotor blades with flatback exhibited favorable local buckling strength at the inboard region compared with those with conventional sharp trailing edge when low-density PVC foam was used.The prototype blade showed linear behavior under extreme loads in spar caps,aft panels,shear web and flatback near the maximum chord which is usually susceptible to buckling in the blades according to traditional designs.The inboard region of the blade showed exceptional load-carrying capacity as it survived420%extreme loads in the experiment.Through this study,potential structural advantages by applying proposed structural features to large composite blades of multi-megawatt wind turbines were addressed.

Real-time Bezier interpolation satisfying chord error constraint for CNC tool path

G01 code generated by a computer-aided manufacture （CAM） system is the most common form of tool trajeclory in computer numerical control （CNC） machining. A tool path composed of short line segments has discontinuous tangenc t and curvature, generating large fluctuations of feedrate and acceleration, which in turn produces vibration in a machine tool. To obtain a smooth tool path, many methods on tool-path smoothing have been developed. However, the shortcomings i：1 these methods exist when they are employed in a CNC system. It is difficult to simultaneously to guarantee the following requirements of CNC machining： （1） chord error should be rigidly constrained; （2） G01 points should be interpolated; （3） cur,,ature should be continuous （G2）; （4） machining should be applicable to spatial cases; （5） real-time performance of computaEion is required.Based on these various requirements, this study proposes an interpolation scheme using CUDlC t^ezler curves anu mciuucb illl adjustment strategy to eliminate deficiencies in the tool path. The tool path generated is G2, chord-elror-constrained, G01-point-interpolated, loop-free, and optimized for both stretch and jerk energy. The method is applicable ：o 3D cases and involves only simple algebraic computations. Thus, the algorithm can be applied to real-time CNC machining. A simulation is conducted to validate the efficiency of the algorithm. In addition, an experiment reveals its advantage over Hermite interpola- tion in surface quality and machining efficiency.