一类新的能够渐进达到Gilbert-Varshamov界的Alternant子类码

本文基于Maximum Distance Separable(MDS)码的Hamming重量分布提出一类新的二元Alternant子类码.分析表明这类新的子类码包含整个BCH码类,并且可以渐进达到Gilbert-Varshamov(GV)界.     

基于可分组设计的部分重复码研究

针对最小带宽再生情形下的有效修复问题,提出了一种新型部分重复(FR,fractional repetition)码设计。该设计由外部最大距离可分(MDS,maximum distance separable)码和内部重复码组成,称为GDDBFR(group divisible design based FR)码,可以达到随机访问模式下的系统存储容量,并且能够在很大范围内选择构造参数。理论分析指出,尽管GDDBFR码采用基于表格的修复方式,但通常具有大量的节点修复选择方案。此外,实验结果表明,与传统的RS(Reed-Solomon)码和再生码相比,GDDBFR码可以显著地减少失效修复时间。     

加拿大针叶木纸浆的打浆特性及其电声性能

本文对各种加拿大进口针叶木纸浆的纤维特性做了分析。研究了各种加拿大进口纸浆的打浆特性及其电声性能。结果表明：在加拿大进口纸浆中,电子级乔治王子未漂白硫酸盐木浆FUKP和北木漂白硫酸盐木浆NBKP比较适合做为生产扬声器纸盆的主要材料。在扬声器纸盆的研发过程中,可以根据扬声器的具体用途及对音质的不同要求采用适当比例的FUKP和NBKP混合抄纸来达到相应的目标。     

基于变量节点可靠度的洗牌置信传播算法

提出了一种新的低密度奇偶校验(Low-Density Parity-Check,LDPC)码串行译码策略.该方法基于原有的LDPC码串行译码策略,根据来自信道的初始消息的可靠度对变量节点或校验节点进行均匀分组.对所提方法的误码率与平均迭代次数进行了分析.仿真结果表明:该策略的性能比原来的LDPC码串行译码策略有很大提高.     

Alkane isomers: presence in petroleum ether and complexity

The presence and absence of alkane isomers in petroleum and petroleum derivatives depend on the complexity of these structures. It was assumed that the more complex the structure is the less probable it is that that the molecule can be detected in any petroleum derivative. Complexity is a vague concept, which has not been defined in quantitative terms yet, and therefore there is no experimental method, which could be used to determine ‘complexity’. Mass spectrometry and infrared spectroscopy in combination with gas chromatography were used to identify the various structural isomers of alkanes in petroleum ether. The isomers were categorised in quantitative terms by using topological indices and linear discriminant analysis. It was found that alkanes possessing a more complex, highly branched structure are less probable to be detected in petroleum ether than isomers with a simpler backbone structure. It was proposed that the experimental ‘measure’ of the complexity of isomer_i should be proportional to 1/C_i , where C_i , denotes the concentration of isomer_i in a (primary) petroleum derivative.     

Flexible Polyester Cellulose Paper Supercapacitor with a Gel Electrolyte

A low-cost polyester cellulose paper has been used as a substrate for a flexible supercapacitor device that contains aqueous carbon nanotube ink as the electrodes and a polyvinyl alcohol (PVA)-based gel as the electrolyte. Gel electrolytes have attracted much interest due to their solvent-holding capacity and good film-forming capability. The electrodes are characterized for their conductivity and morphology. Because of its high conductivity, the conductive paper is studied in supercapacitor applications as active electrodes and as separators after coating with polyvinylidene fluoride. Carbon nanotubes deposited on porous paper are more accessible to ions in the electrolyte than those on flat substrates, which results in higher power density. A simple fabrication process is achieved and paper supercapacitors are tested for their performance in both aqueous and PVA gel electrolytes by using galvanostatic and cyclic voltammetry methods. A high specific capacitance of 270 F g⁻¹ and an energy density value of 37 W h kg⁻¹ are achieved for devices with PVA gel electrolytes. Furthermore, this device can maintain excellent specific capacitance even under high currents. This is also confirmed by another counter experiment with aqueous sulfuric acid as the electrolyte. The cycle life, one of the most critical parameters in supercapacitor operations, is found to be excellent (6000 cycles) and less than 0.5 % capacitance loss is observed. Moreover, the supercapacitor device is flexible and even after twisting does not show any cracks or evidence of breakage, and shows almost the same specific capacitance of 267 F g⁻¹and energy density of 37 W h kg⁻¹. This work suggests that a paper substrate can be a highly scalable and low-cost solution for high-performance supercapacitors.     

Pine Needles (Pinus Sylvestris) as a Bioindicator of Sulphur and Heavy Metal Deposition in the Area Around a Pulp and Paper Mill Complex at Kemi,Northern Finland

Abstract

The determination of sulphur and heavy metals in plants is an integral part of many environmental studies. Pine needles (Pinus Sylvestris) have proved to be suitable air quality indicators for pollutants, especially for sulphur. This study was carried out in the vicinity of Kemi, a town situated on the Gulf of Bothnia in northern Finland. An industrial complex comprising two pulp and paper mills is located in the centre of the area. Scots pine (Pinus Sylvestris) needles were collected from 29 sampling sites. The samples were dried, homogenized and digested with nitric acid. The concentrations of the elements S, Fe, Zn, Ca, V, and Pb were determined by ICP-AES. According to our results pine needles (Pinus sylvestris) appear to be an ideal bioindicator and sampling material for identifying and assessing atmospheric sulphur pollution derived from pulp and paper mills and can complement the information provided by plant mapping studies around pulp and paper mills.     

Graphene oxide reinforced polyamide nanocomposite coated on paper as a novel layered sorbent for microextraction by packed sorbent

ABSTRACT

In this work, a novel layered sorbent for microextraction by packed sorbent (MEPS) was introduced, which has been prepared by coating graphene oxide/polyamide (GO/PA) nanocomposite (NC) onto cellulose paper through solvent exchange method. Scanning electron microscopy (SEM) was applied to investigate the surface characteristic and morphology of PA and GO/PA NC coated on cellulose paper. The prepared MEPS device was used for extraction of organophosphorous pesticides (OPPs) including chlorpyrifos, fenthion, fenithrothion, ethion, edifenphos and phosalone in environmental aqueous samples followed by detection using gas chromatography-flame ionisation detector (GC-FID). Important parameters affecting the MEPS method including pH of sample solution, extraction draw-discard cycles, sorbent layers, desorption solvent volume and desorption draw-eject number were studied and optimised using central composite design (CCD). Based on the method validation, limits of detection (LODs) were in the range of 0.2–1 µg L^?1. The calibration graphs for chlorpyrifos, fenthion and edifenphos are linear in the concentration range of 1 to 500 µg L^?1; for ethion and phosalone are linear in the range of 1–1000 µg L^?1 and for fenithrothion is linear in the range of 3–1000 µg L^?1. The method precision (RSD %) with six replicates determinations was in the range of 3 to 9.4 % and 3.9 to 11.9% for distilled water and spiked river water sample, respectively, at the concentration level of 300 µg L^?1 . The developed method was applied successfully to determine OPP compounds in river, dam and tap water samples; accordingly, the relative recoveries (RR%) were obtained in the range of 77.8 to 113.3%.     

Weight distributions of a class of cyclic codes with arbitrary number of nonzeros in quadratic case

Cyclic codes are an important class of linear codes, whose weight distribution have been extensively studied. So far, most of previous results obtained were for cyclic codes with no more than three nonzeros. Recently, the authors of [37] constructed a class of cyclic codes with arbitrary number of nonzeros, and computed the weight distribution for several cases. In this paper, we determine the weight distribution for a new family of such codes. This is achieved by introducing certain new methods, such as the theory of Jacobi sums over finite fields and subtle treatment of some complicated combinatorial identities.