磨料有序排布电镀砂轮的制备及其把持力研究

为解决电镀砂轮磨削加工中容屑空间不足的问题，采用点胶微粘接的方法制备了磨料有序排布的电镀砂轮，分析了磨料粘接效果和镀层力学性能。通过SEM分析了磨料/镀层/导电胶的结合界面，并进行了干磨削试验。研究结果表明，直径约为磨料粒径40%的胶点可粘接住磨料，单个胶点上粘接多颗磨料的占比小于6%；双脉冲电镀工艺制备的镀层显微硬度大于500HV，表层残余应力小于100MPa，磨料/镀层/导电胶之间的界面贴合紧密，无明显缺陷；砂轮在磨削时没有出现磨料脱落现象。     

Crowding as an Agronomic Factor Determining the Development of Plants and the Productivity of Linseed (Linum usitatissimum L.)

ABSTRACT

Nine sowing densities of linseed were compared in a two-year experiment. Self-regulation of the density of a linseed stand resulted in a differentiated branching of the plants. The number of capsules on a linseed shoot, as well as seeds in the capsule, and the number of seeds from the shoot were highly varied from year to year, and there is even a stronger differentiation in the weight of 1000 seeds. Linear relationships were noted between the mass of seeds from the linseed plant and the number of capsules. The yield of linseed was affected by both factors. An increasing sowing rate reduced the seed yield from the shoot and the plant. At lower seeding rates, the lateral shoots contributed in the seeds yield of the plant to a higher degree compared to the main ones.     

工业园区混合能源优化配置方法应用与实践

为了充分挖掘多能源之间的互补潜力,使工业园区混合能源系统的配置方式由传统粗放式转变为精确优化配置并降低系统配置方案的保守性,基于粒子群联合CPLEX求解算法对工业园区的系统配置和运行调度方案进行分析优化,并以某生物园区为例进行了实例分析,得到了目标函数下的最优设计方案和运行策略。仿真分析结果表明,优化配置方法的应用能够协调冷热电多种能源的混合利用,提升系统的综合经济性。同时,为工业园区能源供应项目的规划、设计提供参考性支撑,丰富设计手段。     

Uncertainties in the determination of pyrrolizidine alkaloid levels in naturally contaminated honeys and comparison of results obtained by different analytical approaches

The contamination of honey with hepatotoxic pyrrolizidine alkaloids (PAs) is a well-known hazard for food safety. While management strategies and controls of the honey industry aim to reduce the PA levels, uncertainties remain with regard to the safety of regionally produced and marketed honey. In addition, a previous study showed large differences of results obtained after various periods of storage and apparent differences between the analytical results of different laboratories. Therefore, this study aimed at examining these uncertainties by monitoring the impact of storage on the PA and PA N-oxide (PANO) content of two freshly harvested honeys and on possible demixing effects caused by pollen settling. Additionally, three analytical approaches – target analysis with matrix-matched calibration or standard addition and a sum parameter method – were applied for a comparative analysis of 20 honeys harvested in summer 2016. All samples originated from Schleswig-Holstein in Northern Germany where the PA plant Jacobaea vulgaris is currently observed on a massive scale. The results of the time series analyses showed that PANO levels markedly decreased within a few weeks and practically reached the LOD 16 weeks after harvest. Tertiary PAs, by contrast, remained stable and did not increase as a consequence of PANO decrease. The experiments on a putative demixing, which may result in a heterogeneous distribution of PAs/PANOs, revealed that there was no such effect during storage of up to 12 weeks. A comparison of the PA/PANO levels obtained by different analytical approaches showed that in some cases the sum parameter method yielded much higher levels than the target approaches, whereas in other cases, the target analysis with standard addition found higher levels than the other two methods. In summary, the results of this study highlight uncertainties regarding the validity and comparability of analytical results and consequently regarding health risk assessment.     

Ergonomics interventions to reduce musculoskeletal risk factors in a truck manufacturing plant

Ergonomic interventions may potentially reduce MSDs, but the context of industries (barriers, ever-changing situations, dialogue processes) might play a significant role in the success of interventions. This study evaluates the effectiveness of ergonomic interventions including engineering/technical and organizational interventions, and the involvement of the stakeholders in reducing musculoskeletal risk factors/symptoms. A pre-post-test experimental study in non-randomized groups was performed over three years in a sector of a truck assembly plant. The mean age of the operators in the sector for the initial and second assessment time was 42.0 (±7.6) years and 39.0 (±8.7), respectively. The mean length of work experience in the current job was 15.2 (±7.2) years and 13.9 (±7.3) for the initial and second assessment times, respectively. Five engineering ergonomic solutions and organizational interventions were implemented after a comprehensive ergonomic analysis. The organizational interventions consisted mostly of transferring and redistributing the tasks, i.e., ergonomically balancing and redesigning of the workstations. Before performing the interventions, the findings of the ergonomic study were presented at several meetings to encourage the involvement of the stakeholders (including managers, engineers, and operators) in the interventions. This study showed that a combination of ergonomic measures—engineering and organizational interventions—could reduce physical workloads. Musculoskeletal symptoms decreased after interventions although the difference was not significant.     

Ultrasonic tomographic velocimeter for visualization of axial flow fields in pipes

An ultrasonic tomographic velocimeter to provide quantitative images of axial flow fields in pipes is developed and presented in this work. To detect the flow in various directions and positions, a novel transducer configuration strategy is proposed. All-in-one transducers are mounted in two sectional planes of the pipe. In each plane, N transducers are equally spaced along the circumference. Overlapped propagation paths are introduced by the configuration strategy, and the influence of the vortex flow can be eliminated theoretically by averaging the line velocities of the overlapped paths. To achieve a fast detection speed, the projection data is collected via an electrical scan in a fan-beam mode. After rearrangement and interpolation of the projection data, the parallel beam filtered back projection (FBP) algorithm is implemented to reconstruct the axial flow field. Numerical simulations with the theoretical velocity profiles were performed. The compensation method for the vortex flow is proved to be effective and necessary, and the number of transducers required for reconstruction of common flow profiles was estimated. Accordingly, an ultrasonic tomographic velocimeter consisting of 2×12 transducers was fabricated. Experiments were conducted in the straight pipe and downstream of a single bend pipe and compared with the computational fluid dynamics (CFD) simulation results. As demonstrated, the ultrasonic tomographic velocimeter was capable of visualizing both symmetric and asymmetric axial flow fields with high reliability.     

植物基人造肉的营养特性与食用安全性

植物肉的出现为动物肉类食品供应短缺和养殖业环境污染问题带来希望。食品加工技术的快速发展弥补了植物基肉制品外观和口感的不足, 但其营养价值和安全性也应引起重视。本文综述了以植物蛋白为主要原料所制肉类替代品的营养价值, 包括植物肉中碳水化合物、蛋白质、脂肪、水分、维生素和矿物质的相对含量和营养性质。分析了植物肉在生产及食用过程中可能出现的物理、化学、生物因素在内的安全问题, 并探讨目前植物肉发展所存在的局限性与挑战, 以期为我国植物蛋白肉制品的研发与推广提供理论参考。     

基于设备改造的选煤厂介质消耗控制研究

同忻选煤厂采用重介质选煤技术,磁性介质的消耗较大,为此,相关技术人员针对介质回收系统设备进行了改造设计。改造后,设备运行稳定,介质消耗降低,提高了原煤的分选效率,创造了较好的安全经济效益。