氟表面活性剂的铺展性能研究

研究环保型 AFFF 的核心成分四碳链表面活性剂(FC-4)溶液在环己烷、正庚烷、航空煤油、溶剂油、0#柴油上的一维铺展性能。用一定量 FC-4 表面活性剂与 1-己烷磺酸钠以物质的量比 1∶1 复配,根据该复配体系的 CMC 值配制浓度为 20 mmol/L 的 FC-4 溶液。得到 25 ℃时液膜铺展长度和时间的关 系,并利用幂指数函数 L=mtn 对实验数据进行拟合,得出表面活性剂溶液在不同油面的铺展长度与时间之间的关系式。经计算,实验值与理论计算值的均方根偏差（RMSD）小于 1.43,表明实验值与理论值吻合较好,可以用幂指数函数预测表面活性剂溶液液膜在燃油上的铺展过程。     

Effects of boronizing on mechanical and dry-sliding wear properties of CoCrMo alloy

In this study, CoCrMo alloy was boronized at 950 °C for 2, 4, 6 and 8 h, respectively. The boronized samples were characterized by scanning electron microscopy, X-ray diffraction, microhardness tester and ring-on-block wear tester. X-ray diffraction studies showed the boride layer formed at 950 °C for 2–8 h consisted of the phases Co₂B and CrB. A large number of pores formed in diffusion zone were probably attributed to the Kirkendall effect. Depending on boronizing time, the thickness of boride layer ranged from 4 to 11 μm. The excellent wear resistance of the boronized CoCrMo alloy was attributed to the high surface hardness of the Co₂B and CrB under dry-sliding conditions when compared to the as-received state.     

Microstructure analysis of boronized pure nickel using boronizing powders with SiC as diluent

In this study, boronizing of 99.9% pure nickel was performed by means of a powder-pack method using Commercial LSB-II powders (that contained SiC) at 850, 900 and 950 °C for 2, 4, 6 and 8 h, respectively. The coated samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and hardness tests. The presence of boride (Ni₂B) and silicide (Ni₅Si₂, Ni₂Si) phases, formed on the surface of boronized pure nickel, were confirmed by X-ray diffraction analysis. The Ni₃Si phase was found when pure nickel was boronized at 850 °C for 2 h. Depending on boronizing time and temperature, the thickness of coating layer ranged from 36 to 237 μm. The hardness values were 832 HV_0.01 for the silicide layer, 984 HV_0.01 for boride layer, and 139 HV_0.01 for the Ni substrate.     

Ultrasonic testing of plasma sprayed coatings

A study examining the application of ultrasonic testing to plasma sprayed coatings is presented. It is shown that bonding defects in aluminium and molybdenum coated samples can be found using sound in the frequency range 5–10 MHz. Though the transmission method is shown to be effective, the backwall reflection method is shown to be the more sensitive to these defects. It is also shown that the attenuation of 5–10 MHz ultrasound in aluminium coatings is related to porosity.     

Experimental Study of the Vibration Phenomenon of Compressor Rotor Blade Induced by Inlet Probe Support

An experimental investigation was conducted in order to understand the installation effects of inlet measurement probes on the vibration characteristics of the ...     

基于Flash CS3的B737飞机起落架刹车系统模拟仿真

起落架刹车系统能在飞机着陆时配合扰流板与反推装置增大飞机的阻力,使之迅速减速,减小滑跑所需距离.运用Flash CS3软件对B737飞机液压动力刹车系统工作原理进行模拟仿真,用逐帧动画和补间动画两种方法将液压的流动方向以动画形式直观展现出来.详细分析了在人工刹车的工作方式下正常刹车、备用刹车和蓄压器刹车三种形式的工作过...     

Application of a new combined intuitionistic fuzzy MCDM approach based on axiomatic design methodology for the supplier selection problem

Evaluating and selecting a suitable supplier is a complex problem which involves a number of different criteria. In literature, there are various multi-criteria decision making (MCDM) methods available with their own characteristic features. The focus of this study is intuitionistic fuzzy (IF) MCDM methods which have attracted much attention from academics and practitioners in recent years. IF sets are widely used to tackle imprecise and uncertain decision information in decision making due to their capability of accommodating the hesitation in human decision processes. This study proposes a new integrated methodology that is used for the first time in the literature. This approach consists of intuitionistic fuzzy analytic hierarchy process (IFAHP), an MCDM technique, for determining the weights of supplier evaluation criteria, and the concept of intuitionistic fuzzy axiomatic design (IFAD) principles for ranking competing supplier alternatives with respect to their overall performance. Decision makers’ assessments and opinions are extended to the IF environment in this approach and furthermore, the group decision making (GDM) approach is utilized in order to overcome uncertainties and vagueness, minimize the partiality of decision process and to avoid bias. This study contributes to supplier selection and IF sets literature by providing a combined framework based on IFAHP and IFAD methodology for the first time. To assess the validity of the proposed integrated IF MCDM approach, a case study from Turkey is provided. This study can be useful to researchers in better understanding the supplier selection problem theoretically, as well as to organizations in designing better satisfying supplier evaluation systems.     

A new fuzzy dempster MCDM method and its application in supplier selection

Supplier selection is a multi-criterion decision making problem under uncertain environments. Hence, it is reasonable to hand the problem in fuzzy sets theory (FST) and Dempster Shafer theory of evidence (DST). In this paper, a new MCDM methodology, using FST and DST, based on the main idea of the technique for order preference by similarity to an ideal solution (TOPSIS), is developed to deal with supplier selection problem. The basic probability assignments (BPA) can be determined by the distance to the ideal solution and the distance to the negative ideal solution. Dempster combination rule is used to combine all the criterion data to get the final scores of the alternatives in the systems. The final decision results can be drawn through the pignistic probability transformation. In traditional fuzzy TOPSIS method, the quantitative performance of criterion, such as crisp numbers, should be transformed into fuzzy numbers. The proposed method is more flexible due to the reason that the BPA can be determined without the transformation step in traditional fuzzy TOPSIS method. The performance of criterion can be represented as crisp number or fuzzy number according to the real situation in our proposed method. The numerical example about supplier selection is used to illustrate the efficiency of the proposed method.     

高高原环境下锂离子电池热失控烟气特性

为探究高高原机场低压低氧环境对锂离子电池热失控行为中喷射火焰温度、热释放速率及烟气组分等参数的影响，构建锂离子电池低压试验平台，以4节单体18650型锂离子电池构成电池组，分别模拟高高原机场（50 kPa）、平原机场环境（90 kPa）下锂离子电池热失控试验。结果表明：在50 kPa工况下，池体破损程度、热释放速率及喷射火焰温度均有所下降，喷射火焰峰值温度降低约241.3 ℃。50 kPa工况下产生的热解烟气中C_xH_y、CO等易燃气体浓度更高，最高体积分数分别可达3 134.50×10^-6和0.860%，并且随热释放速率的增加热增加；在90 kPa工况下呈现相反趋势，C_xH_y、CO气体浓度均有所下降，且随热释放速率的增加热降低。90 kPa工况下电池燃爆更为剧烈，作为物质完全燃烧的证明，CO₂气体浓度高于50 kPa工况下试验值，最高体积分数可达1.510 7%。     

Characterization of cyclic loading/unloading damage behavior in fiber-reinforced ceramic-matrix composites using inverse tangent modulus

Under cyclic loading/unloading, the mechanical hysteresis appears in fiber-reinforced ceramic-matrix composites (CMCs) due to multiple micro damage mechanisms. In this paper, the cyclic loading/unloading damage evolution in different CMCs is analyzed using the inverse tangent modulus (ITMs). Experimental micro damage mechanisms are observed using the X-ray computed tomography (XCT) and scanning electron microscopy (SEM). Based on the damage mechanisms’ analysis, a damage-based micromechanical constitutive model is developed to predict the cyclic loading/unloading curves and related damage parameters. Effects of composite’s constitutive properties, peak stress, damage state and interface properties on the cyclic loading/unloading damage evolution are discussed. For the 1D and 2D SiC/SiC, and 3D C/SiC composites, the evolution curves of ITMs can be divided into two regions. In region I, the increasing rate of the ITMs is constant and depends on the composite’s constitutive properties; and in region II, the increasing rate of the ITMs decreases as the interface slip range approaches the interface debonding tip.