固体酸催化剂上线性烷基苯生成反应动力学研究

在确定线性烷基苯反应生成动力学方程基础上 ,在消除外扩散影响前提下 ,用苯烯摩尔比为 1 0∶1的反应原料 ,在中孔分子筛负载杂多酸催化剂上进行苯与长链烯烃烷基化反应 ,采用气相色谱法分析反应组成 ,获得了不同反应温度、质量空速、催化剂粒度的烷基化反应试验数据。对模型进行参数估值 ,确定了线性烷基苯生成反应速率常数、扩散系数 ,以及反应活化能和扩散活化能参数 ,建立了考虑内扩散影响的线性烷基苯生成反应动力学模型 ,并开展模型评价、模型预测和反应规律研究。研究结果表明 ,线性烷基苯收率试验值和计算值的相关指数为 0 .9892 ,说明该模型具有较强的拟合试验数据能力 ,可信度较高。模型预测结果表明 ,线性烷基苯收率随着反应温度提高和原料与催化剂接触时间延长而不断提高 ,随催化剂粒径增大而降低。     

佩戴防尘口罩对吸入气溶胶粒度影响的实验研究

本文介绍了应用级联撞击器和佩戴口罩的人头模型在天然铀燃料元件加工现场测定吸入气溶胶粒度的方法。结果表明,佩戴口罩使得吸入气溶胶的活度中值空气动力学直径(AMAD)变小,并且吸入气溶胶的 AMAD 值与场所气溶胶的 AMAD 值有一定关系,粒径分布类型也发生改变。文中还报告了口罩的漏过率有随微尘粒径减小而增大的趋势。实验结果对内照射剂量估算以及评价口罩的防尘能力有一定的参考价值。     

无动力快速浮选在山东某黄金矿山的应用

山东某黄金矿山选矿厂由于浮选工艺流程中旋流器与取样机之间高差较大,以致溢流矿浆流速快、动能大,易造成对管路、弯头及取样机缓冲箱的冲击磨损。鉴于此,在旋流器溢流进入浮选粗选前增加快速浮选槽,以充分利用矿浆的动能,将原浮选工艺流程前增设无动力快速浮选工艺,并对改造后工艺流程结构进行了优化,将原三次扫选改为二次扫选。无动力快速浮选工艺的应用,不但节约了能耗,而且提高了金回收率,其由改造前的91.69%提高到93.06%,生产指标较好。     

Orientationability analyses of a special class of the Stewart–Gough parallel manipulators using the unit quaternion representation

This paper addresses the orientation-singularity and orientationability analyses of a special class of the Stewart–Gough parallel manipulators whose moving and base platforms are two similar semi-symmetrical hexagons. Employing a unit quaternion to represent the orientation of the moving platform, an analytical expression representing the singularity locus of this class of parallel manipulators in a six-dimensional Cartesian space is obtained. It shows that for a given orientation, the position-singularity locus is a cubic polynomial expression in the moving platform position parameters, and for a given position, the orientation-singularity locus is an analytical expression but not a polynomial directly with respect to the mobile platform orientation parameters. Further inspection shows that for the special class of parallel manipulators, there must exist a nonsingular orientation void in the orientation space around the orientation origin for each position in the position-workspace. Therefore, a new performance index referred to as orientationability is introduced to describe the orientation capability of the special class of manipulators at a given position. A discretization algorithm is proposed for the computation of the orientationability of the special class of manipulators. Moreover, effects of the design parameters and position parameters on the orientationability are investigated in details. Based on the orientationability performance index, another novel performance index referred to as practical orientationability is presented which represents the practical orientation capability of the manipulator at a given position. The practical orientationability not only can satisfy all the kinematic demands and constraints of such class of manipulators, but also can guarantee that the manipulator is nonsingular.     

Broadband MIMO Antenna System for 5G Operations in Mobile Phones

A broadband 8‐antenna multiple‐input and multiple‐output (MIMO) system working for 5G new radio N77 (3.3‐4.2 GHz) in mobile terminals is proposed. In particular, each antenna element/unit consists of a monopole‐type meandered branch and an inverted U‐shaped self‐isolated antenna branch; and the antenna unit is fed by the meandered branch. The antenna unit has two resonances generated separately by each branch of the antenna unit. Since the monopole couples strongly with the self‐isolated antenna element that has the inherent self‐isolation characteristics, quite good isolation for the broadband 8‐antenna MIMO system can be obtained. The results such as antenna efficiency, radiation patterns, envelope correlation coefficient, and channel capacity are also presented.     

Rapid growth of angle-confined large-domain graphene bicrystals

In the chemical vapor deposition growth of large-area graphene polycrystalline thin films,the coalescence of randomly oriented graphene domains results in a high density of uncertain grain boundaries (GBs).The structures and properties of various GBs are highly dependent on the misorientation angles between the graphene domains,which can significantly affect the performance of the graphene films and impede their industrial applications.Graphene bicrystals with a specific type of GB can be synthesized via the controllable growth of graphene domains with a predefined lattice orientation.Although the bicrystal has been widely investigated for traditional bulk materials,no successful synthesis strategy has been presented for growing two-dimensional graphene bicrystals.In this study, we demonstrate a simple approach for growing well-aligned large-domain graphene bicrystals with a confined tilt angle of 30° on a facilely recrystallized single-crystal Cu (100) substrate.Control of the density of the GBs with a misorientation angle of 30° was realized via the controllable rapid growth of subcentimeter graphene domains with the assistance of a cooperative catalytic surface-passivation treatment.The large-area production of graphene bicrystals consisting of the sole specific GBs with a tunable density provides a new material platform for fundamental studies and practical applications.     

A novel de-rusting method with molten salt precleaning and laser cleaning for the recycling of steel parts

Clean Technologies and Environmental Policy - Steel parts are a kind of high recovery value product for which de-rusting is the primary step in the recycling process. Laser cleaning is a popular...     

Nanoindentation measurement of core–skin interphase viscoelastic properties in a sandwich glass composite

Mechanics of Time-Dependent Materials - Debonding at the core–skin interphase region is one of the primary failure modes in core sandwich composites under shear loads. As a result, the...     

IE理论在营业厅固网业务流程优化中的应用

针对营业厅固网业务服务流程繁琐、服务不及时、客户长时间排队等待的现状,基于工业工程(IE)理论,重新定义IE理论图表技术符号,应用“5W1H”提问技术分析现状,确定需要优化的项目;应用“ECRS”4大原则优化固网业务流程。以某市营业厅固网业务流程为例,优化后客户平均移动距离由69 m缩短至34 m、高峰期平均停留时间由58 min缩短至29 min,说明使用该方法优化固网业务流程效果明显。这对于提高客户满意度、提升服务质量和效率以及企业竞争实力具有指导作用。