SBA-15固载磷钨酸催化剂的制备及催化合成叔丁基苯酚

以不同硅烷偶联剂改性的介孔分子筛SBA-15为载体、PW_(12)为催化剂,通过对SBA-15表面共价及非共价修饰制备磷钨酸@介孔分子筛/硅烷偶联剂复合催化剂PW_(12)@SBA-15/YSiX_3(YSiX_3=Apts、Atapts、Papts);并利用FT-IR、XRD、TEM、N_2吸附-脱附对其组成、结构及形貌进行表征。以改性SBA-15分子筛固载磷钨酸催化剂催化合成叔丁基苯酚为研究对象,考察不同硅烷偶联剂、反应温度、苯酚与叔丁醇物质的量比对催化合成叔丁基苯酚的影响,并获得合成叔丁基苯酚的最佳工艺条件,即反应温度145℃、n(苯酚)∶n(叔丁醇)=1∶2.5、重时空速2.2 h~(-1),该最佳反应条件下,PW_(12)@SBA-15/Apts催化剂催化合成叔丁基苯酚的催化活性最高,苯酚转化率为98.3%,2,4-二叔丁基苯酚选择性为57.3%.     

硅烷偶联剂改性玻璃纤维增强硅气凝胶的研究

为了达到增强硅气凝胶力学性能的目的,采用硅烷偶联剂KH550与KH560二步改性接枝玻璃纤维,进而制备纤维增强硅气凝胶。利用扫描电子显微镜、红外光谱仪、比表面及孔径分布仪、热重-差热分析仪、导热系数仪、电子动静态疲劳试验机等对其表征。实验结果表明：硅烷偶联剂改性玻璃纤维与硅气凝胶复合后网络结构更加均匀、骨架强度更加稳定、孔径多在30 nm以下、具有良好的热稳定性;同时,改性玻璃纤维的最佳添加量为20%（质量分数）,此时其密度为0.167 g/cm³,导热系数为0.018 5 W/（m·K）,接触角为127°,抗弯强度为1.042 MPa,抗压强度为0.669 MPa,达到预期实验目的。     

Fundamental Evaluation of Power Supply and Rectifiers for Wireless Power Transfer Using Magnetic Resonant Coupling

This paper provides a fundamental analysis of a power supply and rectifiers for wireless power transfer using magnetic resonant coupling (MRC). MRC enables efficient wireless power transfer over middle‐range transfer distances. MRC for wireless power transfer should operate at a high frequency in the industry science medical band, such as 13.56 MHz, because the size of the transfer device decreases at higher transfer frequencies. Therefore, the output frequency of the power supply on the transmitting side should be 13.56 MHz. In addition, the rectifier on the receiving side is operated at a high frequency. This paper focuses on the reflected power in the power supply and rectifiers. Thus, the parametric design method is clarified for the power supply, including a low‐pass filter to match the output, the impedance of the power supply with the characteristic impedance of the transmission line. In addition, the effects on the rectifiers of silicon carbide and gallium nitride diodes are confirmed by performing an experiment and a loss analysis.     

A high efficiency input/output magnetically coupled interleaved buck–boost converter with low internal oscillation for fuel-cell applications: Small signal modeling and dynamic analysis

Dynamic behavior of DC–DC converters plays a crucial role in stability of renewable energy exploitation systems. This paper presents small signal modeling of an input/output magnetically coupled interleaved buck–boost converter for fuel-cell applications to help the designers with the better understanding of converter dynamics. Aiming to have a continuous converter transfer function for a smooth transition between the operation modes and an improved inner dynamics, a damping network and an input/output coupling have been added to the interleaved structure of well-known cascaded buck–boost converter. Having the same step-up/step-down voltage transfer ratio, smooth transition and improved inner dynamics make this converter quite suitable for renewable energy applications. The paper presents a small signal ac equivalent circuit model of the proposed converter based on state space averaging (SSA) method. Simulation results show remarkable improvements in converter dynamic behavior in both time and frequency domains. Prototype setup of 360 W and 36 V output voltage for a fuel cell with a brand of “FCgen 1020ACS” Ballard Power Systems, Inc. was implemented. Experimental results are presented to verify the theoretical model and its expected merits.     

Reduction of Ripple Current Loss by Electromagnetic Coupling of Air‐Core Reactors

To reduce the loss due to ripple current in a multiphase current‐reversible chopper, we investigated electromagnetic coupling of an air‐core reactor. We derived the relationship between the amplitude of the ripple current, the duty factor, and the electromagnetic coupling coefficient, and used the results to estimate the effects of electromagnetic coupling in the design of a train energy storage system. We built reactors with electromagnetic coupling coefficients of 0.93 and 0.60. These reactors employed a new winding structure that provides an optimal electromagnetic coupling coefficient. The mass of the former type of reactor was increased by 4.4% over the conventional design, and that of the latter type of reactor was decreased by 17%. Finally, we tested the new reactors. When the chopper employs the former type of reactor and operates with equal‐phase switching and cumulative coupling, the loss due to ripple current is decreased by 11%. When the chopper employs the latter type of reactor and operates with shift‐phase switching and differential coupling, the loss is decreased to 31%. The test showed that the calculated relationships agreed with the measured values.     

On‐surface polymerization – a versatile synthetic route to two‐dimensional polymers

Two‐dimensional (2D) polymers are novel covalent sheet materials with promising properties, but also great synthetic challenges. The inadequacy of traditional wet chemical synthesis calls for new synthetic paradigms. In this respect, employing surfaces as inherently 2D reaction venues appears an adequate choice and has recently already yielded encouraging results. Polymerization at air ? liquid and liquid ? liquid interfaces has been reported from time to time over the last decades, whereas recent efforts on solid surfaces are less traditional. In either case, both movement and coupling of monomers are already confined in two dimensions at interfaces or on surfaces. Accordingly, this approach naturally affords low‐dimensional reaction products. To achieve 2D reticulation, monomers are functionalized with multiple reactive groups of the same or a different kind, whereby their number and stereochemical arrangement predefines the ideal structure of the resulting 2D polymer. This perspective article exemplifies different approaches, i.e. types of surfaces, coupling chemistry and activation schemes, to employ surfaces for novel synthetic routes for the bottom‐up synthesis of 2D polymers. © 2015 Society of Chemical Industry     

采煤机平滑靴平动固-热-力耦合特性分析

针对采煤机滑靴在推进过程中,平滑靴与刮板输送机中部槽间瞬态温度高导致接触面磨损甚至失效的问题,构建了煤粉界面层影响下动摩擦因数的平滑靴固-热-力耦合数学模型,再以试验获取的滑靴载荷作为输入,利用Comsol Multiphysics分别对干煤粉和含水煤粉界面影响下,采煤机前、后平滑靴与刮板输送机中部槽间的固-热-力耦合特性进行分析。结果表明:接触面间温度与滑靴受力、煤粉的状态有关,干煤粉界面下前后平滑靴的最高温度为460.04 K和433.73 K,最高温度位置在作用关节中心;含水煤粉界面下前后平滑靴的最高温度为438.31 K和418.62 K,最高温度位置同样位于作用关节中心。     

斜轧穿孔法制备Ti80合金无缝管工艺分析

运用有限元技术模拟了两辊斜轧穿孔法制备Ti80合金无缝管坯的三维热力耦合过程。仿真结果能动态显示坯料从咬入到稳定穿孔再到穿出3个阶段复杂的塑性成形过程,并能辅助分析中心孔腔的形成机理以及坯料在穿孔阶段各物理场量的分布。结果表明:坯料刚接触顶头时,中心金属存在明显塑性变形,结合轧制中心线上不同方向的正应力状态为(+,-,+),判断中心孔腔的形成为拉应力作用下的塑性开裂。在穿孔过程中,坯料的应变分布沿轴向呈U1+W+2U2形态,沿径向为片层状,最终穿制毛管等效应变可达5～11;坯料的外表面与导盘接触区应变速率为0.71～3.6s~(-1),而与轧辊接触区高达4.6～26s~(-1),大的应变速率有助于毛管的塑性成形过程;顶头前坯料的温度最高,与穿孔工具接触的区域温度略有降低,但绝大部分变形区温度都处于单相区。模拟所得全流程顶头轴向力与轧制力的变化呈现典型的3阶段分布,其中稳定穿孔阶段力能参数的均值接近试验所得,从而验证了模型的准确性。基于有限元模拟的工艺条件,在实验轧机上一火次顺利穿制出Ti80合金无缝管坯,其显微组织展现为单一的魏氏组织形态,且由于变形剧烈,从外表面到中间层再到内表面均为等轴细小的β动态再结晶晶粒;力学性能测试表明该组织状态下的毛管的强度和塑性均满足指标要求。     

全地域机动车驾驶室声学特性分析

以某全地域机动车驾驶室为研究对象,建立驾驶室的有限元模型,验证了有限元模型的有效性。以此有限元模型为基础构建驾驶室谐响应模型,进行谐响应分析,发现驾驶室后壁板的振动是引起驾驶室内部噪声的主要原因。研究驾驶室内部噪声特性,分别进行了声学空腔模态分析和声固耦合模态分析,发现声固耦合系统声压分布比较均匀,大部分呈现局部模态,主要原因可能是驾驶室后壁板的振动。通过驾驶员耳旁声压分析发现增加驾驶室后壁板的厚度,可以在一定程度内降低驾驶室内部噪声对驾驶员的影响,为同类驾驶室通过依靠结构改进来改善声场环境提供了案例依据。     

采场覆岩两带与采空区自燃三带相关关系研究

为研究采煤工作面覆岩两带（冒落带、裂隙带）与自燃三带（散热带、窒息带、氧化带）的关系，通过建立覆岩运移模型，应用CDEM软件模拟分析了试验工作面采动空间上覆岩层两带的扩展过程，分析垂向方向覆岩两带分布对水平方向上垮落煤岩堆积状态的影响情况。通过现场埋管实测的手段以及氧体积分数法进行了采空区煤自燃三带的划分。研究表明，冒落带高度稳定情况下，采煤推进距离（48 m）与采空区散热带和氧化带的分界线（进风侧采空区以里50 m左右，回风侧采空区以里40 m左右）有较好的吻合关系。裂隙带高度稳定情况（顶板150 m处的岩层最大下沉值趋于基本稳定）下，采煤推进距离（126 m）与采空区氧化带和窒息带的分界线有较好的对应关系。