Characterization of odorous contaminants in post‐consumer plastic packaging waste using multidimensional gas chromatographic separation coupled with olfactometric resolution

The increasing world population with their growing consumption of goods escalates the issue of sustainability concepts with increasing demands in recycling technologies. Recovery of post‐consumer packaging waste is a major topic in this respect. However, contamination with odorous constituents currently curtails the production of recycling products that meet the high expectations of both consumers and industry. To guarantee odor‐free recyclates, the main prerequisite is to characterize the molecular composition of the causative odorants in post‐consumer plastic packaging waste. However, targeted characterization of odorous trace contaminants among an abundance of volatiles is a major challenge and requires specialized and high‐resolution analytical approaches. For this aim, post‐consumer packaging waste was characterized by sensory analysis and two‐dimensional high resolution gas chromatography coupled with mass spectrometry and olfactometry. The 33 identified odorants represent various structural classes as well as a great diversity of smell impressions with some of the compounds being identified in plastics for the first time. Substances unraveled within this study provide insights into sources of odorous contamination that will require specific attention in the future in terms of screening and prevention in recycling products.     

一类具有资源约束和优先加工顺序约束极小化加权总完工时间调度优化问题研究

本文针对工件间具有链状优先约束和relocation资源约束的极小化加权总完工时间调度优化问题展开研究.针对这一NP难问题,利用relocation约束的性质和贪婪算法的思想,设计了一个多项式近似算法,并证明了当链不可中断,每个链具有相同工件数和工件间具有相同加工时间时,2为该算法的紧界.     

Resource constraint scheduling with a fractional shared resource

We consider a scheduling problem motivated by mining in remote off-grid areas. In this model, mines have pre-assigned mineral processing jobs and their own machine for executing these jobs. Each job also needs a certain amount of electricity in order to get completed. The electricity, on the other hand, is of limited supply and must be shared between the mines. We present a mathematical formulation of the problem and a Lagrangian relaxation based heuristic. Computational results which compares our heuristic with genetic algorithm and simulated annealing are also presented.     

地震期间应急资源调度方案的优化选取

应急资源的调度是地震救援工作的重点,为解决这个难题,本文构建了以时效性、伤亡性和经济性为三大分量的多目标函数,然后经过无量纲和Delphi加权处理,将其转化为单目标函数,并将其中的决策效用函数看成运筹学中指派问题的效率函数,最后运用匈牙利法计算出最大的目标函数值,从而得出最优的资源调度方案.与其他多目标的应急资源调度方法相比,本文构建的这种算法具有简易、实用的优点,可以说为地震期间应急资源调度方案的优化选取工作提供了一种切实、可行的途径.     

北京城市水资源供需系统研究

在研究北京市水资源供需现状的基础上,采用系统动力学方法构建了城市水资源供需模型.利用系统思考中学习型组织的信息反馈回路模式,引入基于可持续发展系统生存回路的水资源供需平衡指标,采用反映供需关系紧张的水供需一次、二次平衡作为衡量地区水危机的变量.按照人口增长与人均综合用水定额不同组合下的城市水需求总量,得到未来北京市水资源供需平衡变化的四种情境,通过动态模拟,分析不同情况下满足水需求的供应方案.结果显示,北京市现有的水资源条件与城市发展需水要求还有较大距离,应在挖掘本地水资源的基础上,依靠南水北调工程等境外调水,解决地区缺水的矛盾.     

制度变革的经济绩效—兼论优化配置与创新驱动的作用

改革开放以来,中国取得了举世瞩目的经济成就。这一成就的取得与改革开放所释放的制度性红利密切相关。但近年来,改革进入深水区,开放遭遇瓶颈期,制度对经济增长的绩效需要进行再检验。基于2003−2016年省际面板数据,实证结果表明：2003年以来,中国制度质量与经济增长仍然显著正相关,但制度的“门槛”效应已经显现;制度变革既通过优化资源配置,也通过激励技术创新提升经济绩效。在优化配置路径中,劳动力转移对经济增长的贡献度明显高于资本,约是资本贡献度的两倍;在创新驱动路径中,制度的创新激励效能非常明显,制度变革经技术创新中介传导对经济增长的贡献度约为50%。分区域看,东部地区是资源优化配置的主要受益者,但“门槛”效应已十分显著;中西部地区制度质量的边际改进对经济增长的贡献度大于东部地区,技术创新中介效应主要源于创新投入,但存在创新要素错配问题。由此得出的结论对中国进一步推进要素市场制度建设和完善创新驱动发展机制具有一定的政策启示作用。     

Chiral Chromium Salen@rGO as Multipurpose and Recyclable Heterogeneous Catalyst

The first immobilization of a pyrene-tagged chromium salen complex through π-π noncovalent interactions on reduced graphene oxide (rGO) is described. A very robust supported catalytic system is obtained to promote asymmetric catalysis in repeated cycles, without loss of activity or enantioselectivity. This specific behavior was demonstrated in two different catalytic reactions (up to ten reuses) promoted by chromium salen complexes, the cyclohexene oxide ring-opening reaction and the hetero-Diels-Alder cycloaddition between various aldehydes and Danishefsky's diene. Furthermore, the chiral chromium salen@rGO has been found to be compatible with a multi-substrate type use, in which the structure of the substrate involved is modified each time the catalyst is reused.     

Terephthalic Acid Copolyesters Containing Tetramethylcyclobutanediol for High-Performance Plastics

There is a need for high-performance applications for terephthalic acid (TPA) polyesters with high heat resistance, impact toughness, and optical clarity. Bisphenol A (BPA) based polycarbonates and polyarylates have such properties, but BPA is an endocrine disruptor. Therefore, new TPA polyesters that are less hazardous to health and the environment are becoming popular. Tetramethylcyclobutanediol (TMCD) is a difunctional monomer that can be polymerized with TPA and other diols to yield copolyesters with superior properties to conventional TPA polyesters. It has a cyclobutyl ring that makes it more rigid than cyclohexanedimethanol (CHDM) and EG. Thus, TMCD containing TPA copolyesters can have high heat resistance and impact strength. TPA can be made from abundantly available upcycled polyethylene terephthalate (PET). Therefore, this review discusses the synthesis of monomers and copolyesters, the impact of diol composition on material properties, molecular weight, effects of photodegradation, health safety, and substitution of cyclobutane diols for future polyesters.     

Dynamic Ring-chain Equilibrium of Nucleophilic Thiol-yne “Click” Polyaddition for Recyclable Poly(dithioacetal)s

We report a dynamic polymerization system based on the reversible nucleophilic Michael polyaddition of activated alkynes and dithiols. Four poly(dithioacetal)s(P1-P4) were prepared via the base-catalyzed thiol-yne "click" polyaddition of two dithiols(1,4-butanedithiol(4 S) and 1,5-pentanedithiol(5 S)) and two alkynones(3-butyn-2-one(Y1) and 1-phenyl-2-propyn-1-one(Y2)) at high concentrations. We systematically investigated the base-catalyzed polymerization of 4 S and Y1(for polymer P1) under dif...