Removal of Cr (VI) from aqueous solution using magnetic biochar synthesized by a single step method

Magnetic biochar, as an adsorbent, was synthesized by a single step method, where iron salt was directly mixed with pinewood sawdust by chemical co-precipitation and subsequently pyrolyzed at 700°C for Cr (VI) removal from aqueous solution. The effects of some important parameters including adsorbent dosage (0.4–2.8?g/L), pH (1–10) of the solution, contact time (0–1440 minutes), initial concentration (30–120?mg/L), and temperature (20–40°C) were investigated in batch experiments. Both pre- and post-adsorbents were characterized by SEM-EDX and XPS to investigate the adsorption mechanism. The maximum adsorption capacity of the tested magnetic biochar under the certain experimental conditions determined as optimal was 42.7?mg/g for Cr (VI). The adsorption data were proved to be suitable for the pseudo-second order model for kinetics and the Langmuir model for isotherms with correlation R²?=?0.9996 andR²?>?0.9980, respectively, after fitting with four kinetic models (pseudo-first order, pseudo-second order, W-M model, and Elovich) and three isotherm models (Langmuir, Freundlich, and Temkin). The characteristic analyses further verified that the efficient particle was a mixture of iron oxides in essence, and it had a strong effect on the spontaneous and endothermic adsorption process.     

一种基于特征值反求的复合材料层合板波动特性的近似修改方法

采用一种特征值反求形式的方法用来近似层状复合板的波动特性修改。通过敏感度分析,确定层合板中能最显著地改变结构波动特性的结构参数为设计变量。采用二阶泰勒展式近似特征值和特征频率相对于设计变量的改变率。计算了不同结构变化时的色散特性,并与精确计算结果进行了比较。结果证明本方法对于层状复合板波动特性修改的近似是可行并且有效的。     

KF—Al2O3催化丙烯酸—β—羟乙酯合成

ＫＦ－Ａｌ２Ｏ３催化丙烯酸－β－羟乙酯合成高大彬伍伟夫（大连大学化学化工系大连１１６６２２）关键词丙烯酸－β－羟乙酯ＫＦ－Ａｌ２Ｏ３催化中图分类号Ｏ６２３．６１２丙烯酸－β－羟乙酯（ＨＥＡ）是一种用途广泛的有机单体，可用于纤维加工、涂料、粘接剂、橡胶...     

Binary linear codes with few weights from Boolean functions

Boolean functions have very nice applications in coding theory and cryptography. In coding theory, Boolean functions have been used to construct linear codes in different ways. The objective of this paper is to construct binary linear codes with few weights using the defining-set approach. The defining sets of the codes presented in this paper are defined by some special Boolean functions and some additional restrictions. First, two families of binary linear codes with at most three or four weights from Boolean functions with at most three Walsh transform values are constructed and the parameters of their duals are also determined. Then several classes of binary linear codes with explicit weight enumerators are produced. Some of the binary linear codes are optimal or almost optimal according to the tables of best codes known maintained at http://www.codetables.de, and the duals of some of them are distance-optimal with respect to the sphere packing bound.

     

A Lower Bound for Congruence Representations

G. Grätzer, H. Lakser, and E. T. Schmidt proved that every finite distributive lattice D with n join-irreducible elements can be represented as the congruence lattice of a lattice L with O(n2) elements. G. Grätzer, I. Rival, and N. Zaguia gave kn, < 2, as a lower bound for the size of such a lattice L; a sharper form, 1/64(n/log2n)2, of this result was given by Y. Zhang.In this note, we apply a recent result of R. Freese, to obtain 1/16 n2/log2n as a lower bound. We also give a direct proof of Freese's result.     

Synthesis of 4H-cyclopenta[c]furans via cooperative PdCl2-FeCl2 catalyzed cascade cyclization reaction involving a novel acyl rearrangement process

We have discovered a novel PdCl(2)-FeCl(2) catalyzed cascade cyclization reaction, which involves a novel acyl rearrangement process. This reaction affords a diverse set of poly-substituted 4H-cyclopenta[c]furan products. The reaction scope of this cascade process is quite broad and various internal acetylenes can be employed.