翼缘扩大型节点与传统节点的受力性能对比分析

为了研究翼缘扩大型节点的力学性能,对比分析其与塞板焊接节点及传统钢结构梁柱连接节点的受力性能差异,设计了一种翼缘扩大型梁柱连接节点.采用ABAQUS分析软件对三种节点在单调荷载下的受力性能进行分析,研究翼缘扩大型节点在实际结构中应用的可行性,并对比分析三种节点的性能差异.结果表明,翼缘扩大型节点能够有效改善节点的受力状态,改善节点区域应力分布问题,使节点梁端的塑性铰出现区域向跨中转移;与塞板焊接节点以及传统节点相比,翼缘扩大型节点承载力较高,且节点域柱与梁端应力分布较为均匀.     

Photocatalytic activity of porous magnesium oxychloride cement combined with AC/TiO<Subscript>2</Subscript> composites

As a decorative material, magnesium oxychloride cement was used as a photocatalyst supporter to purify the pollutants indoors. Due to excellent adsorption properties of activated carbon (AC), the photocatalytic composties, TiO₂/AC, were prepared and introduced into the porous magnesium oxychloride cement (PMOC) substrate to composite a sort of photocatalytic cementitious material (PCM). The optimal composite processes were assessed by gas chromatograph, using toluene as the target. By comparing the perspective of toluene purification and thorough decomposition, it can be found that the optimal mass ratio for TiO₂/AC composites is 4/25, and the heat treatment to TiO₂/AC sample at 350 °C can play the optimal synergetic role of adsorbents in photocatalytic process. The synergistic effect of TiO₂, AC and magnesium oxychloride cement (MOC) was also evaluated by gas chromatograph. One-take molding process was adopted to introduce the TiO₂/AC into PMOC substrate, and its optimal mass fraction was 4 wt%, while the appropriate density of substrate was 0.35 g/cm3. Toluene degradation showed that the prepared PCM can degrade pollutants efficiently. The appropriate treatment process of TiO₂/AC, mass of TiO₂/AC, substrate density, and stable pore structure should be coordinated to maximize the adsorption-photodegradation performance. The combination of photocatalytic materials, adsorbents, and building materials provided a new idea for the application of photocatalysis.     

Influence of Structural Parameters of Turbocharger Floating Bearing on Its Dynamic Characteristic Coefficients

The structure parameters in an actual industrial production have a great influence on the coefficient of supercharger floating bearing dynamic characteristics,but there has been little systematic study so far. In this paper, the influence of structural parameters of the turbocharger floating bearing on its dynamic characteristic coefficientsis systematically investigated based on the theories of hydrodynamic lubrication and tribology. The influence of clearance ratio on eccentricity and the influence of internal to external radius ratios, and Sommerfeld number were analyzed.A new formula of responding characteristics of the oil film force caused by the displacement or velocity disturbance was deduced near an equilibrium in the steady state. Applying the newly developed formula, the dynamic characteristic was studied for floating bearings. Regularity for change of oil film stiffness and damping was analyzed with the structural parameters of floating bearing such as radius ratios and eccentricity.It has been found that the clearance ratio increases with eccentricity when the radius ratio is unchanged.The eccentricity decreases with the internal to external radius ratio of floating rings when the clearance ratio is constant.The absolute value of total principal stiffness and total main damping decrease with the clearance ratio and radius ratio of floating rings when the total cross damping is stable. The results and findings in this paper can contribute to nonlinear dynamics designs of turbocharger rotor-bearing systems.     

Mathematical Advancement of General Chlorine Bulk Decay Model

An accurate chlorine bulk decay model is needed to ensure that potable water meets the microbial and the chemical safeties at the treatment plant and throughout the distribution. Among the mathematical models available,the general second-order chlorine bulk decay model( GBDM) is the most fundamentally sound.Application of the GBDM,however,has been hindered by its numerous fictive parameters and lack of an analytical solution. This theoretical work removes the two obstacles. The GBDM is solved through transformation and integration. The analytical solution provides deep insights into the GBDM and facilitates the parameterization and sensitivity analysis. The background natural organic matter( NOM) is characterized with the probabilistic distribution of functional groups. It reveals that the mean of the function group distribution is correlated with the initial chlorine decay rate coefficient( κ_0). A simple formula is developed to determine κ_0 directly from the initial chlorine decay. The theoretical treatment reduces the fictive parameters to a minimum. For the common lognormal distribution,the GBDM needs only three parameters,well defined as initial chlorine demand X_0,median rate coefficient km,and heterogeneity index σ. For more complicated scenarios,composite distributions are constructed through superposition of individual distributions. A highlighted example is to predict chlorine decay in blends of different waters. With the theoretical and mathematical advancement here,the GBDM can be applied effectively to any reactive background matter in any reaction systems.     

黄河流域三门峡水文测区泥沙密度试验分析

黄河流域三门峡水文测区地处黄河中下游,测区所辖水文站分布在晋、陕、甘、豫区间,是黄河流域多沙、粗沙区,也是治理黄河泥沙的重点区域。多年来,测区各水文站大多采用置换法推求泥沙水样的沙重,泥沙密度值均取经验值2.70 g/cm~3。为了验证这一数值的准确性,在1990~1995年试验的基础上,于2007年和2013年,在本测区黄河干流和重要支流的12个水文站和库区取样,进行密度试验。通过统计分析,求出本测区黄河干流各站的泥沙密度值为2.71g/cm~3、支流各站的泥沙密度为2.73g/cm~3。     

基于职业技能大赛背景的高职英语课程教学改革与实践

文章通过英语口语技能大赛对高职英语课程设置、教学模式与方法、师资队伍建设的导向作用,提出教学内容具有职业性、拓宽第二课堂教学途径、培养英语听说核心技能等教学改革启示,并对当前高职英语教学实践存在的问题进行分析与思考,从而有效推动高职英语改革与课程建设。     

基于单片机的运动者生理数据实时监控系统设计

长跑是大学生体质测试项目,对运动者的心血管机能有较大挑战,对于长期不参与耐力锻炼的人可能存在一定危险性,所以对长跑运动的生理数据实时监测是十分重要的.设计一套基于Arduino单片机的穿戴式设备,采用心率、加速度等模块采集运动者的实时生理参数,单片机对采集到的这些参数进行数据融合并显示,然后对其身体状况进行实时评估,一旦出现特殊情况会及时提醒运动者,同时把结果无线传输到指导教师的终端上,以便教师及时处置.     

短肢剪力墙结构扭转效应有限元分析

利用ANSYS有限元分析软件,建立三层短肢剪力墙空间结构有限元模型,通过改变控制参数和受力条件,研究轴压比、荷载偏心距和节点区箍筋配筋率对短肢剪力墙结构抗扭承载能力的影响,并将计算结果与一个结构模型试验结果进行对比。计算结果表明:当轴压比小于等于0.5时,短肢剪力墙结构抗扭承载能力随轴压比增加而增大,当轴压比超过0.5以后,结构抗扭承载能力随轴压比增加而降低;荷载偏心距增大,扭转效应加强,结构承载能力降低,扭矩增加加速了连梁端部受拉破坏,外边缘结构的连梁端部受到弯剪扭复合作用,是结构抗震的薄弱位置,建议加强配筋;适当增加节点区水平箍筋配筋率能有效提高结构抗扭承载能力。     

Design and implementation of path planning algorithm for vehicle parking

Parking is an important and indispensable skill for drivers. With rapid urban development, the automatic parking assistant system is one of the key components in future automobiles. Path planning is always essential for solving parking problems. In this paper, a path planning method is proposed for parking using straight lines and circular curves of different radius without collisions with obstacles. The parking process is divided into two steps in which the vehicle reaches the goal state through the intermediate state from the initial state. The intermediate state will be selected from the intermediate state set with a certain criterion in order to avoid obstacles. Similarly, an appropriate goal state will be selected based on the size of the parking lot. In addition, an automatic parking system is built, which effectively achieves the parking lot perception, path planning and performs parking processes in the environment with obstacles. The result of simulations and experiments demonstrates the feasibility and practicality of the proposed method and the automatic parking system.     

波浪循环荷载作用下滨海软土水平向动力特性试验研究

为研究海上风电桩基在波浪荷载作用下,产生水平向循环荷载对桩基周围土体动力特性的影响,以唐山地区滨海软土为研究对象,通过室内动三轴试验,研究不同围压、动应力幅值和振动次数条件下对软土水平向动力特性的影响。结果表明:软土水平向动强度随围压增加而增加,随振动次数增加而减小;动应力幅值增大,破坏振次减小;水平向动应变ε_d随振动次数增加变大,且动应力幅值越大,增速越明显,变化规律遵循Monismith模型;动应力幅值改变时,软土水平向动模量变化明显,当围压减小,动弹性模量减小;曹妃甸软土水平向间具有明显的结构性,不同围压条件下,随动应力幅值增加动阻尼比均表现增大趋势。