Molecular weight distribution of polyethylene catalyzed by Ziegler–Natta catalyst supported on MgCl2 doped with AlCl3

Ti‐based Ziegler–Natta catalysts supported on MgCl₂ doped with AlCl₃ were prepared by the reaction of MgCl₂/AlCl₃–ethanol adduct with TiCl₄. No AlCl₃ crystallites were found in the AlCl₃‐doped catalysts by WAXD analysis, suggesting that AlCl₃/MgCl₂ solid solution was formed. The effect of doping on the catalyst performance in ethylene polymerization was investigated. The results showed that the catalysts based on AlCl₃‐doped MgCl₂ support exhibited a slightly higher activity than did the MgCl₂‐supported catalyst and the molecular weight distribution (MWD) of polyethylene (PE) markedly increased (from 10.8 to 47.9) with the increase of AlCl₃ content in catalysts. The changes in catalyst's active center distribution were studied based on nonlinear fitting of the polymer GPC curves by multiple Flory functions. It was found that increase of types of active centers by introducing AlCl₃ into the support should be responsible for the broadening of MWD of PE. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1768–1772, 2006     

焙烧硫酸铁铵催化合成季戊四醇双缩苯甲醛

以硫酸铁铵经600℃高温焙烧制得一类新型固体酸催化剂，该催化剂在合成季戊四醇双缩苯甲醛中具有较高的催化活性，其优化条件是：苯甲醛与季戊四醇物质的量比为2．0：1，催化剂用量为5％(以醇的质量为准)，回流温度83℃，反应时间2．5h，在此优化条件下，反应产率为87％。且催化剂容易制备，可连续使用。     

离子色谱法测定配煤、焦炭和焦油中的氯含量

研究了用带电导检测器的离子色谱对配煤、焦炭和焦油中的Cl- 进行测定的方法。在YSA型8126A-4# 阴离子分离柱上用3.5mmol/LNa2CO3、5.3mmol/LNaHCO3做淋洗液对Cl-进行测定,方法简便快速。Cl-的检出限为2×10-6。该法也适用于F-、NO2-、NO3-、SO42-等的测定。     

纯聚酯户外消光粉末涂料的制备

以高黏度、低酸值的含羧基饱和聚酯树脂为基料,以含有缩水甘油基的丙烯酸树脂为消光固化剂制备纯聚酯户外消光粉末涂料。介绍了该涂料的制备工艺,并讨论了原材料和生产条件对产品性能的影响。     

生化腐植酸对土壤微生物多样性及番茄青枯病的影响

在温室盆栽番茄条件下研究施用BHA对番茄生长和防病的影响，应用BIOLOG方法研究了BHA对土壤微生物群落的调节作用。结果表明，提前施入BHA能明显提高番茄的株高、生物量；在番茄生长前期AWCD值和土壤微生物的各项多样性指数已较高．改善了土壤微生物群落功能结构．并能在较长时间内（前中期）保持稳定，防效明显。     

State space approximation for general fractional order dynamic systems

Approximations for general fractional order dynamic systems are of much theoretical and practical interest. In this paper, a new approximate method for fractional order integrator is proposed. The poles of the approximate model are unrelated to the order of integrator. This feature shows benefits on extending the algorithm to the systems containing various fractional orders. Then a unified approximate method is derived for general fractional order linear or nonlinear dynamic systems via combining the proposed new method with the distributed frequency model approach. Numerical examples are given to show the wide applicability of our method and to illustrate the acceptable accuracy for approximations as well.     

Making sky lanterns from polygonal meshes

Releasing sky lanterns is a popular way of celebrating festivals and ceremonies in the Asian countries. This paper presents a computer-aided approach to help novice users to design flyable sky lantern with desired shape. Given a closed up-right 3D model with a user-specified cutting on the bottom, our system optimizes the shape by regularizing the boundary, smoothing the geometry and improving the volume-to-area ratio to make it feasible for flying. The optimized shape is then approximated by a set of developable patches. Next, through a physical analysis step that tests the flying condition and determines the optimal size, the approximated shape is flattened into 2D patches, which can be printed out and glued together to form the airbag. Finally, the user can attach the airbag to a bamboo frame and assemble the fuel cell. We successfully apply our prototype system to design and construct real sky lanterns.     

Synthesis of poly(1-methyl-1-phenyl-1-silapentane) by chemical reduction of poly)1-methyl-1-phenyl-1-sila-cis-pent-3-ene with diimide

Summary Poly(1-methyl-1-phenyl-1-silapentane) (I) has been prepared by the chemical reduction of the carbon-carbon double bonds of poly(1-methyl-1-phenyl-1-sila-cis-pent-3-ene (cis-II) with diimide, which was generatedin-situ by the thermal decomposition ofp-toluenesulfonhydrazide in refluxing toluene. At lower temperature (100°C),cis-II is isomerized byp-toluenesulfinic acid to lower molecular weight poly(1-methyl-1-phenyl-1-sila-cis andtrans-pent-3-ene) (cis/trans-II). Protodesilation of I with trifluoromethanesulfonic acid yields poly(1-methyl-1-trifluoromethanesulfonyl-1-silapentane) (III). The structures of I andcis/trans-II have been characterized by¹H,¹³C and²⁹Si NMR, GPC, TGA and elemental analysis. The structure of I has been characterized spectroscopically by¹H,¹³C,¹⁹F and²⁹Si NMR.     

巴豆酸乙烯酯的提取及聚合应用

巴豆酸乙烯酯存在于醋酸乙烯酯生产的工业废液中,在一定条件下聚合会形成环状结构。用于改性以聚醋酸乙烯酯为基础的乳胶漆无须引发剂和加热,只是简单混和即可使耐洗刷次数增加几倍,还可与其它乙烯基酯、氯乙烯、苯乙烯、马来酸酐等多种单体交联共聚。     

Minimizing conditional-value-at-risk for stochastic scheduling problems

This paper introduces the use of conditional-value-at-risk (CVaR) as a criterion for stochastic scheduling problems. This criterion has the tendency of simultaneously reducing both the expectation and variance of a performance measure, while retaining linearity whenever the expectation can be represented by a linear expression. In this regard, it offers an added advantage over traditional nonlinear expectation-variance-based approaches. We begin by formulating a scenario-based mixed-integer program formulation for minimizing CVaR for general scheduling problems. We then demonstrate its application for the single machine total weighted tardiness problem, for which we present both a specialized l-shaped algorithm and a dynamic programming-based heuristic procedure. Our numerical experimental results reveal the benefits and effectiveness of using the CVaR criterion. Likewise, we also exhibit the use and effectiveness of minimizing CVaR in the context of the parallel machine total weighted tardiness problem. We believe that minimizing CVaR is an effective approach and holds great promise for achieving risk-averse solutions for stochastic scheduling problems that arise in diverse practical applications.