A time-dependent multiple criteria single-machine scheduling problem

We introduce a nonpreemptive single-machine scheduling model with time-dependent multiple criteria. We formulate the problem as a knapsack problem and propose a dynamic programming (DP)-based algorithm to finding all efficient schedules. An illustrative example is enclosed.     

Regio- and stereoselective synthesis of 3- and 5-(C-glycosyl)-4-nitroisoxazolidines by nitrone–nitroalkene [3+2] cycloaddition reactions

Cycloaddition reactions of nitrones, including sugar nitrones, with nitroalkenes, including sugar nitroolefins, led with complete regioselectivity and stereospecificity to 4,5-trans-4-nitroisoxazolidines in 51–78% global yields. The endo/exo stereoselectivity depends on the type of sugar derivative used. As expected, the best π-diastereofacial selectivity was observed when both partners were sugar derivatives. Isomerisation of the first formed diastereomers by the action of silica gel was observed in some cases. Absolute configurations for two crystalline products were assigned by X-ray diffraction methods.     

Packing of linearly arranged benzene molecules inside single walled carbon nanotubes: The high pressure study

The high pressure behaviors and electronic properties of (C₆H₆)_n@SWCNT peapod structure with the different encapsulation densities are studied by the DFT calculation. The weak van der Waals interaction and electronic orbital hybridization interaction between the host and guest molecules are exhibited in the pressure lower and higher than 3 GPa, respectively. The encapsulation density of C₆H₆ molecules plays an important role in the structural deformation, the bonding behaviors, and the electronic orbital hybridization interaction of the considered four hybrid systems under the pressures.     

电炉渣超微粉改性生物质废弃物制备生态活性炭的光谱学分析

利用木材、竹子、等其他生物资源制备具有发达多孔结构与丰富比表面积的活性炭,存在生产成本较高、不利于生态环境的可持续发展、使用寿命短和失效后容易造成室内环境二次污染的问题。冶金固体废弃物与生物质废弃物是工业生产与农业生产主要的副产品,因利用难度大、附加值低且成本高,导致大量堆放和填埋,不仅造成生态环境的污染,而且极大的浪费潜在资源。面对上述问题,利用冶金固体废弃物与生物质废弃物开发一种价格低廉且性能优越的生态活性炭,既是冶金固体废弃物与生物质废弃物的高附加值利用与资源可持续发展的重要途径之一,也是大幅降低改性活性炭生产成本与提高经济效益的重要途径之一。以核桃壳与电炉渣为研究对象,利用电炉渣中含有的金属氧化物对生物质废弃物进行改性处理制备用于甲醛降解的生态活性炭,依据《室内装饰装修材料人造板及其制品中甲醛释放限量》(GB18580-2017)对生态活性炭性能进行测试。利用X-射线光电子能谱(XPS)对元素含量进行测试与分析,X-射线荧光光谱仪(XRF)对化学成分进行测试与分析,傅里叶变换红外光谱仪(FTIR)对结构组成进行测试与分析,X-射线衍射仪(XRD)对矿物组成进行测试与分析,扫描电子显微镜(SEM)对微观结构进行测试与分析,激光粒度仪(LPSA)对粒度分布进行测试与分析和比表面积及孔径测定仪(BET)对孔结构进行测试与分析,以揭示核桃壳与电炉渣制备生态活性炭的机理,以及生态活性炭对甲醛的降解机理。结果表明:核桃壳超微粉与电炉渣超微粉进行复合制备具有良好降解甲醛性能的生态活性炭,不仅实现了冶金固体废弃物与生物质废弃物的高附加值的利用,而且提出了"以废治危"的新室内空气甲醛治理理念。电炉渣超微粉较好的被包裹于生态活性炭层状结构中,提高生态活性炭的粉化率,形成粒径较小的颗粒,有利于提高生态活性炭与甲醛的降解作用面积。电炉渣超微粉中含有Fe元素、Mn元素与Ti元素,Fe元素具有磁性促使大量甲醛在生物质活性炭孔结构表面形成富集,Mn元素与Ti元素对已经富集的甲醛进行催化降解,实现吸附降解与催化降解的协同作用。     

"一锅法"合成N-乙基咔唑乙酰化衍生物

以N-乙基咔唑为原料,通过“一锅法”合成了未见文献报道的单乙酰化衍生物3-乙酰基-9-乙基咔唑和双乙酰化衍生物3,6-二乙酰基-9-乙基咔唑,其结构经1H NMR,IR,MS和元素分析表征。     

毛细管电泳在农药残留检测上的应用

对近20年来毛细管电泳分析方法在农药残留分析中的应用进行了论述.按照农药的用途分类,分别评述了应用毛细管电泳分析检测杀虫剂和杀菌剂以及除草剂残留的研究进展,并对毛细管电泳在农药残留分析中的应用进行了展望.     

Emission and electron/ion analysis of the ablated plume from LiYF4 crystals doped with Tm3+ or Nd3+ ions

We performed temporal as well as frequency-resolved emission spectroscopy of the plasma plume generated in vacuum by 355 nm pulsed laser ablation of a LiYF₄:Tm³⁺ crystal (1% Tm³⁺ concentration) and a LiYF₄:Nd³⁺ crystal (1.5% Nd³⁺ concentration). The plume emission spectrum is very rich in features and shows the elemental lines belonging to all the components of the host lattice, either neutral or ionized. The time-resolved analysis of some emission features is discussed and some stream velocities are derived. A possible model for the time evolution of the plume components is reported. The electronic detection technique was used to detect the onset of the plasma plume and to measure the ablation laser fluence threshold.     

非金属掺杂改性TiO2光催化剂的机理

为了扩展TiO2光催化剂对可见光的利用,以非金属元素对其进行掺杂和改性是近年来很活跃的研究内容,文献报道主要有氮、碳、硫、氟等非金属元素的改性结果.各种不同的改性方法如高温气氛还原、脉冲激光沉积、离子溅射、机械化学、溶液湿法等都可以得到非金属元素改性.本文重点探讨了氮改性TiO2光催化剂的结果,氮改性TiO2的方法和改性机理,讨论了氮改性TiO2的结构及其对可见光的利用机理等,对碳、硫、氟等元素掺杂改性也作了简要介绍.     

Deformation process of a shocked drop-in-liquid

正A mixed flow of two immiscible liquids may form drops of one liquid in the other.Deformation and breakup of drops occur when there is sufficient hydrodynamic or surface forces from the ambient liquid;such deformation and breakup of drops is a common phenomenon in various engineering applications,such as oil-water flow in the petroleum recovery industry[1,2],stirred dispersions in the chemical industry[3,4],and melted metal and cooling liquid interactions in the     

Laminar burning velocities of 2-methyltetrahydrofuran at elevated pressures

The laminar burning velocities (LBVs) and cellular instability of 2-methyltetrahydrofuran (2-MTHF) were investigated at the unburned temperature of 423 K and pressures from 1 to 10 atm in a cylindrical constant-volume vessel. The LBVs of 2-MTHF/air flame exhibit a notably dropping with increasing pressure. The cellular instability analysis indicates that the critical flame radius of 2-MTHF/air mixture monotonically increases with increasing pressure and the flame surface suffers more badly cellularity under higher pressures. The critical flame radius exhibits non-monotonic variation versus ? and the most unstable flames appear at ? ≈ 1.3. It is observed that the measured Markstein length of 2-MTHF/air mixture decreases with increasing ? and P_u, leading to an earlier formation of wrinkling and cracks with respect to preferential-diffusional instability. Further investigation found that by using a mixture of 14.2% oxygen with 85.8% helium in place of air as bath gas at 10 atm can effectively suppress the cellular instability. Two recently developed models were used to simulate the experimental results and explore the chemical kinetic effects on LBV. Reaction path analysis reveals that the most consumption of 2-MTHF/air at stoichiometric conditions is through the abstraction of H-atom to form radical C₅H₉O-5. While the competitiveness of decomposition by CC scission yielding CH₃ and tetrahydrofuran radical is relatively weak. Sensitivity analysis illustrates that small-species reactions show a controlling effect on LBV. The increasing pressure leads to an evident increase in the sensitivity coefficient of the recombination reaction H + O₂ (+M)=HO₂ (+M). The reduction of H atom concentration will cause competition to the initiation reaction H + O₂ = O+OH. This could lower the overall oxidation rate and reduce the burning velocity.