PMS钢在精密复杂塑料模具中的应用及热处理

简要分析了精密复杂模具热处理变形及硬度问题,介绍了PMS钢的性能及特点,该钢固溶后硬度低便于机械加工,成形后时效,模具硬度提高,减少了模具热处理变形,是精密复杂塑料模具最佳模具材料,并介绍了PMS钢的热处理工艺及应用。     

The structure and properties of chromium nitride coatings deposited using dc, pulsed dc and modulated pulse power magnetron sputtering

The time averaged ion energy distributions and ion fluxes of continuous dc magnetron sputtering (dcMS), middle frequency pulsed dc magnetron sputtering (PMS), and modulated pulse power (MPP) magnetron sputtering plasmas were compared during sputtering of a Cr target in an Ar/N₂ atmosphere in a closed field unbalanced magnetron sputtering system. The results showed that the dcMS plasma exhibited a low ion energy and ion flux; the PMS plasma generated a moderate ion flux of multiple high ion energy regions; while the MPP plasma exhibited a significantly increased number of target Cr⁺ and gas ions with a low ion energy as compared to the dcMS and PMS plasmas. Cubic CrN coatings were deposited using these three techniques with a floating substrate bias. The structure and properties of the coatings were characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nanoindentation, microscratch and ball-on-disk wear tests. It was found that the deposition rate of the MPP CrN depositions was slightly lower than those of the dcMS depositions, but higher than in the PMS depositions at similar average target powers. The coatings deposited in the dcMS and PMS conditions without the aid of the substrate bias exhibited large columnar grains with clear grain boundaries. On the other hand, the interruption of the large columnar grain growth accompanied with the renucleation and growth of the grains was revealed in the MPP CrN coatings. The MPP CrN coatings exhibited a dense microstructure, fine grain size and smooth surface with high hardness (24.5 and 26 GPa), improved wear resistance (COF = 0.33 and 0.36) and adhesion, which are the results of the low ion energy and high ion flux bombardment from the MPP plasma.     

GO/CoFe2O4催化过硫酸盐降解邻苯二甲酸二丁酯效能

为高效地去除水中环境激素类污染物,采用共沉淀法合成了氧化石墨烯负载钴尖晶石铁氧体(GO/CoFe_2O_4)催化剂,催化过硫酸盐(PMS)去除水中邻苯二甲酸二丁酯(DBP).采用SEM、TEM、XPS、XRD对催化剂进行表征,研究不同条件下催化PMS去除水中DBP的效果,提出催化PMS反应机理.结果表明,GO/CoFe_2O_4为颗粒状尖晶石结构,室温下,DBP初始浓度为2μmol/L、催化剂投量为0.1 g/L、PMS浓度为20μmol/L、pH为7时,GO/CoFe_2O_4催化PMS体系对DBP的去除率可达89%,使用5次后催化效果仅降低5%.该新型复合催化剂高效、具有磁性、方便回收,具有良好的工程应用前景.     

NiOx激活PMS降解染料废水的研究（研究生论坛）

随着水处理行业的不断发展,对于传统的高级氧化技术（AOPs）也提出了更多新的要求,也开发了很多新的高性能催化剂用于高级氧化领域。为了探究NiOx在超声强化的条件下对单过硫酸盐（PMS）的催化性能,同时探究NiOx/PMS/US高级氧化体系对染料废水降解的优势,采用溶胶-凝胶法制备NiOx催化剂,酸性橙7（AO7）作为降解底物。探究发现：相比于NiOx/H2O2/US、NiOx/过硫酸盐（PDS）/US体系,NiOx/PMS/US体系具有更高的降解效率,且催化剂的煅烧温度、[氧化剂]:[氧化底物]、催化剂投量、超声功率都会对NiOx/PMS/US体系产生影响。结果表明：煅烧温度由200℃升至700℃后,AO7的降解率由95%降低至20%。[氧化剂]:[氧化底物]由20:1升至70:1,其降解率由77%提至95%,继续提高比例则会抑制降解。催化剂投量由120mg/L升至280mg/L,降解率提升不明显,在15分钟内都能达到95%的降解,但降解速率有所提升,继续提高催化剂投量其降解速率则没有明显的提高。超声功率由0W提至400W也会提高降解速率,但过高的超声功率对降解速率提高却不明显。此外,对催化剂复用以及对甲基橙（HIn）和活性艳蓝（KN-R）的降解证明NiOx/PMS/US体系具有一定的稳定性和普适性。NiOx的XRD图谱说明最佳煅烧温度下催化剂主要有NiO、Ni及无定型碳组成。NiOx是一种高效的催化剂,其良好的催化活性,稳定性和普适性,在高级氧化技术中可以发挥重要作用。当然其制备成本高和难以规模化生产成为了制约NiOx实现经济效益的主要因素,所以接下来的研究方向应为降低催化剂的制备成本并使其量产,最终让其进入应用领域。     

Field performance evaluation of stone interlayer pavement in Louisiana

In this study, field performance of a stone interlayer pavement test section and cement-stabilised base test control section on LA-97 in Acadia Parish, Louisiana, was monitored during 20 years of service. In addition, the performance of other nine stone interlayer pavement sections in Louisiana constructed from 1999 to 2008 was monitored and evaluated. Field evaluations in this study included distress surveys on all 11 pavement sections, and non-destructive evaluation of pavement structure by the falling weight deflectometer and the dynamic deflection determination system test on nine of these sections. The field evaluation results indicated that the stone interlayer test section on LA-97 had a superior pavement performance to control section over the 20 years of service, and other nine stone interlayer pavement sections were in good pavement condition after 2.5–12 years of service.     

A risk-based optimisation methodology for pavement management system of county roads

A pavement management system (PMS) is a strategic and systematic process to maintain and upgrade the road network. When funding is limited, it is very important to identify the best mix of road preservation projects that provides the maximum benefits to society in terms of overall life cycle cost of the road network. The most common factors that play an important role for identifying projects are the following: budget, traffic volume, Present Serviceability Index (PSI) and risk associated with selecting treatment types. This research develops an optimisation methodology for county paved roads that identify the best mix of preservation projects within budget, maximising traffic (passengers and trucks traffic) on treated roads, maximising the weighted average PSI, and minimising the risk. This methodology will facilitate a statewide implementation of PMS for counties in the state of Wyoming.     

Designing a performance measurement system to support materials management in engineer-to-order:a case study

There are many different production situations that can be employed to meet demand.In the engineer-toorder(ETO)production situation,products are manufactured to meet specific customer needs by unique engineering or significant customization.In such an environment,failing to supply the required materials in the right quantities and at the right time increases the risk of breaching due date agreements and thereby losing customer satisfaction.As such,materials management is one of the most important and critical processes within production planning and control in ETO.To bring attention and improvement to this area,ETO companies may benefit from a performance measurement system(PMS)that systematically monitors how well materials management is carded out.The design of a company's PMS varies with its production situation.Within the large body of literature on performance management and measurement,limited literature specifically addressing performance measurement in ETO has been identified.After being approached by a Norwegian ETO company requesting a PMS for materials management,the authors therefore set out to design the PMS from scratch,using literature on ETO,materials management and performance management and measurement as a starting point.The paper presents the proposed PMS.It provides a basis for further studies on the topic,and could be used by managers in ETO companies to assess and improve their materials management practice.     

过渡金属氧化物非均相催化过硫酸氢盐(PMS)活化及氧化降解水中污染物的研究进展

近年来,水体中富集的难降解污染物导致了诸多环境问题,传统水处理工艺并不能对其进行有效处理。高级氧化技术是目前处理难降解污染物的最有效方法。过渡金属氧化物非均相催化过硫酸氢盐(PMS)活化生成硫酸根自由基(SO_4~-·)处理水体中难降解污染物是近些年新兴的高级氧化技术,与以生成羟基自由基(·OH)为基础的传统高级氧化技术相比,该技术具有对pH适应范围更宽、中性条件下氧化性更强、自由基半衰期更长的优势,同时也克服了均相催化体系中金属离子的二次污染、难以重复利用的问题,受到环境领域学者的广泛关注,为去除水体中抗生素、激素等难降解污染物提供了新的思路和方法。然而,由于活性点位的减少,相较于均相催化,非均相催化的催化效率更低,同时也存在催化稳定性差、难以回收等不足。针对上述问题,近几年除了探寻对PMS的活化具有催化活性的新型过渡金属氧化物外,研究者主要从催化材料的负载、改性以及复合三方面进行尝试,并取得了丰富的研究成果,在发挥非均相催化经济、环保优势的同时,大幅提高了催化剂的催化效率及可回收性,为其步入实际应用做出了巨大的贡献。在众多过渡金属元素中,钴、铁、锰的氧化物已被证明对PMS的活化具有催化活性并得到了广泛的研究。其中,由于钴离子对PMS表现出最强的活化能力,因此对钴系氧化物研究得最早。随后,铁及锰的氧化物因环境友好、廉价易得的优势逐渐成为钴氧化物的替代品。近五年的研究工作将纳米碳、介孔材料以及金属-有机框架等引入催化剂的制备合成中,对过渡金属氧化物进行负载和改性,加强了催化材料的电子传递速度和化学稳定性,为解决催化剂的催化效率低与催化稳定性差等问题提供了有效方法。此外,以两种过渡金属元素为催化核心的二元复合材料,在降低催化剂制作成本的同时,还可以实现催化剂效能和稳定性的双重提高。文章介绍了钴系氧化物、锰系氧化物、铁系氧化物等三种能够催化PMS活化的一元非均相催化剂的研究进展,并阐述了二元复合催化剂的研究现状,总结了现阶段研究的不足并对未来的发展方向做出了展望,以期为制备经济高效的过渡金属氧化物催化剂提供参考。     

Strongly Coupled g‐C3N4 Nanosheets‐Co3O4 Quantum Dots as 2D/0D Heterostructure Composite for Peroxymonosulfate Activation

The development of effective approaches for the preparation of 0D quantum dots (QDs)/2D nanosheets (NSs) heterostructures, which have been proven to be favorable for heterogeneous catalysis, is highly desirable but remains a great challenge. Herein, 0D metal oxide nanocrystals–2D ultrathin g‐C₃N₄ nanosheets (Co₃O₄/CNNS) heterostructures are synthesized via a facile chemical reaction, followed by annealing in air. Ultrafine Co₃O₄ QDs (≈2.2–3.2 nm) are uniformly and tightly attached on the surface of g‐C₃N₄ nanosheets. Detailed characterization reveals that the specially designed unique 0D/2D structure is critical to the high photocatalytic performance for the degradation of tetracycline (TC) via peroxymonosulfate (PMS) activation. The optimal catalyst, namely, Co₃O₄/CNNS‐1100, exhibits excellent performance and ≈98.7% TC can be degraded under visible light irradiation. Moreover, TC degradation is almost completely insusceptible to several real water samples. Meanwhile, other dye pollutants can also be efficiently degraded by the Co₃O₄/CNNS‐1100/PMS/vis system. The quenching tests display that that the h⁺, ?OH, O₂^??, and SO₄^?? are responsible for TC removal. The improved photocatalytic performance can be attributed to the synergistic effect of the photocatalytic‐ and chemical‐processes in the PMS activation. This work gives an insight into the development of multifunctional 0D/2D nanocomposites for further potential applications which are not limited to environmental purification.     

基于切向角特征的统计步态识别

提出一种基于切向角特征的统计步态识别算法。首先利用Procrustes统计形状分析将步态序列中人体侧影轮廓的连续姿态变化表示成一个紧致的Procrustes均值形状(Procrustes Mean Shape, PMS),作为原始步态特征。然后计算PMS上各采样点处的切矢量所对应的切向角。切向角反映轮廓形状在该点处的走向和趋势,提供一种局部的可鉴别的步态特征,称为切向角特征(Tangent Angle Feature, TAF)。最后,利用切向角度差距离来计算任意两个TAF之间的相似性,并用最简单的标准分类器实现步态识别。在CASIA数据库和SOTON数据库上的实验结果表明,该算法简单有效,得到的正确识别率优于其他现有算法。