JFNK方法在S N输运计算中的应用

JFNK(Jacobian-free Newton-Krylov)方法是一种求解非线性方程的高效迭代算法。传统输运计算中的负通量修正与k-特征值迭代使得原本线性的输运计算转变为非线性问题数值求解。为提高非线性输运问题的计算效率,将这两类非线性问题离散成残差形式的非线性方程组,并采用JFNK方法对其进行迭代求解。分析不同约束条件对JFNK方法性能的影响,并将其与NK(Newton-Krylov)方法进行对比。针对JFNK方法的内迭代过程,分析两类子空间方法(GMRES(m)与LGMRES)对整体计算效率的影响。数值结果表明：①相比于传统的幂迭代方法,JFNK方法具有更高的计算效率;②Jacobian矩阵向量积的差分近似对结果没有影响,且基于物理的约束条件比标准的数学约束更加高效;③LGMRES可以充分利用子空间的信息,从而使得JFNK方法整体表现更加高效。     

Oligonucleotides and pesticide regulated peroxidase catalytic activity of hemin for colorimetric detection of isocarbophos in vegetables by naked eyes

A novel colorimetric sensing platform based on the peroxidase activity of hemin regulated by oligonucleotide and pesticide was reported for the ultrasensitive and selective detection of isocarbophos. Oligonucleotides can accumulate on the surface of hemin in acid condition and temporarily inhibit its catalytic activity, which results in the loss of one electron of TMB molecule and produce the blue products. With the addition of isocarbophos, the pesticide molecules can interact with oligonucleotides to form some complexes, which relieve the inhibition of ssDNA to hemin and further enhance its catalytic activity. Thus, the TMB molecules are further oxidized to lose another electron and produce the yellow product in a few minutes, which has the characteristic absorption peak at 450 nm. The color change of the sensing system is related to the amount of isocarbophos, so this method can quickly discriminate whether the target pesticide exceeds the maximal residue limit just by naked eyes. To improve the performance of sensing platform, some important parameters like buffer condition and ssDNA have been investigated, and the peroxidase activity of hemin was further studied to verify the catalytic mechanism. The proposed sensing platform has a detection limit as low as 0.6 μg/L and displays good selectivity against other competitive pesticides. Moreover, the developed sensing platform also exhibits favorable accuracy and stability, indicating that it has potential applications in the detection of pesticide residues in agricultural products.

A novel colorimetric sensing platform based on oligonucleotides and pesticide regulation; the peroxidase catalytic activity of hemin was firstly reported for the ultrasensitive and selective detection of isocarbophos pesticide.

     

Polymeric zinc ferrocenyl sulfonate as a molecular aspirator for the removal of toxic metal ions

A porous bilayered open coordination polymer [Zn(4,4'-bpy)(2)(FcphSO(3))(2)](n) (1; FcphSO(3)Na=m-ferrocenyl benzenesulfonate), has been assembled from Zn(NO(3))(2), m-ferrocenyl benzenesulfonate, and the bridging ligand 4,4'-bipyridine (4,4'-bpy). Ion-exchange induced products [Cd(0.6)Zn(0.4)(4,4'-bpy)(2)(FcphSO(3))(2)](n) (2), [Zn(0.75)Pb(0.25)(4,4'-bpy)(2)(FcphSO(3))(2)](n) (3), and [Cu(0.5)Zn(0.5)(4,4'-bpy)(2)(FcphSO(3))(2)](n) (4) could be obtained directly by suspending a big single crystal of 1 into concentrated solutions of Cd(NO(3))(2), Pb(NO(3))(2), and Cu(NO(3))(2), respectively. Most importantly, the big single crystal of 1 could be partly regenerated after immersion into concentrated aqueous solutions of Zn(NO(3))(2). On the other hand, powdered 1 could also be used as a metal ion adsorbent because of the well-defined pore size and pore shape. Ion exchange takes place along with the process of ion sorption. The big single crystal of 1 removes harmful metal ions by means of ion exchange, whereas powdered 1 removes toxic metal ions mainly through ion sorption. Also, compound 1 could be employed as a multi-ion analysis fluorescent probe to detect dangerous metal ions, such as Pb(2+), Cd(2+), Ag(+), and Cu(2+). The compounds described in this study may have potential applications in the design of new molecular devices.     

高分散加氢脱硫催化剂制备及其对二苯并噻吩的催化性能

近年来,柴油发动机产生的废气污染已成为一个严重问题,环境法规对燃油中的硫含量限制越来越严格.因此,开发高效的深度加氢脱硫催化剂成为当今的热门课题之一.在柴油馏分中,由于存在空间位阻作用,二苯并噻吩(DBT)及其烷基取代的衍生物是最难脱除的.传统的加氢脱硫(HDS)催化剂通常是将活性金属担载在γ-Al2O3上.近年来,介孔材料如MCM-41,SBA-15,HMS,KIT-1和KIT-6等也被用作加氢脱硫催化剂载体,其大的比表面积有利于活性组分分散,大的规则孔径有利于反应物和产物扩散.其中,KIT-1介孔分子筛具有三维短蠕虫状介孔结构和大的比表面积,其酸性和水热稳定性都高于MCM-41.然而,由于无定形的孔壁使得介孔分子筛的酸性和水热稳定性较差,限制了其在石油化工领域的应用.而介微孔复合分子筛兼具了微孔分子筛酸性强、水热稳定性好和介孔分子筛的孔道优势,因此一经出现就引起了研究者广泛关注.有研究认为,增加载体酸性有利于加氢及促进C-S键氢解反应.载体中的微孔可高效吸附氢分子,降低HDS过程所需的温度和压力,实现温和条件下燃油超深度脱硫.目前,已有研究者将Y-MCM-41,介孔ZSM-5及Beta-KIT-6等多级孔分子筛用作催化剂载体,并进行了加氢脱硫性能研究,取得了良好效果.我们曾利用双模板剂一步晶化法水热合成了介微孔复合分子筛ZK-1.该分子筛既具有与KIT-1相似的短蠕虫状三维介孔孔道,又具有ZSM-5的微孔结构.其介孔孔径为2.7 nm,微孔孔径为0.6nm.该分子筛具有良好的水热稳定性和较高的酸性.本文在上述研究基础上,以不同硅铝比的ZK-1为载体通过过量浸渍法担载Co,Mo活性组分制备了CoMo/ZK-1 (Si/Al=30)和CoMo/ZK-1 (Si/Al=40)催化剂,并以相同方法制备了CoMo/γ-Al2O3,CoMo/AlKIT-1,CoMo/ZSM-5和CoMo/Mix(等量的ZSM-5和AlKIT-1混合物)催化剂作为对比.催化剂的N2吸附和NH3程序升温脱附表征结果表明,CoMo/ZK-1具有高于其他催化剂的比表面积(约700 m2/g)和介微孔结构,介孔孔径和微孔孔径分别为2.3 nm和0.6-1 nm.CoMo/ZK-1的酸量大于相同硅铝比的CoMo/AlKIT-1,这是由于ZK-1的介孔孔壁上含有沸石结构单元.通过H2程序升温还原表征可知,CoMo/ZK-1的高温氢耗峰面积较CoMo/γ-Al2O3和CoMo/ZSM-5相比明显减小,表明在CoMo/ZK-1上难还原的组分数量减少,载体与金属之间的相互作用减弱,这有利于金属组分的还原和硫化.紫外-可见漫反射光谱表征结果表明,在ZSM-5表面形成了大量的聚合态氧化钼物种,这是由于载体表面积小,金属组分分散不均匀.Co2AlO4或Co2SiO4相的出现是由于载体与金属间存在较强的相互作用.以ZK-1和AlKIT-1为载体的催化剂则避免了该情况的发生.从高分辨透射电镜照片可知,MoS2在ZK-1表面分散很均匀,其堆垛层数(2.5-2.7层)和片晶长度(3.9-4.0 nm)都达到较理想的数值,有利于形成更多的Co-Mo-S(Ⅱ)活性相.以二苯并噻吩为模型化合物,采用固定床反应器考察了上述6种催化剂的加氢脱硫活性.催化剂的脱硫率从高到低依次为:CoMo/ZK-1 (40)＞ CoMo/ZK-1 (30)＞ CoMo/γ-Al2O3＞ CoMo/ZSM-5＞ CoMo/Mix＞ CoMo/AlKIT-1.在较温和的反应条件(320℃,3MPa,WHSV=5h-1)下,CoMo/ZK-1对DBT的脱硫率达到93％以上.其原因主要是:(1)ZK-1的大比表面积使Co,Mo活性组分高度分散在载体表面;(2)载体与金属之间较适中的相互作用有利于活性组分的还原与硫化;(3)ZK-1含有的沸石结构单元使其比AlKIT-1具有更多的酸中心,有利于提高HDS反应活性.     

Preparation of polypyrrole-coated CuFe2O4 and their improved electrochemical performance as lithium-ion anodes

CuFe_2O_4 network,prepared via the electrostatic spray deposition technique,with high reversible capacity and long cycle lifetime for lithium ion battery anode material has been reported.The reversible capacity can be further enhanced by coating high electronic conductive polypyrrole(PPy).At the current density of 100mA·g~(-1).Li/CuFe_2O_4 electrode delivers a reversible capacity of 842.9 mAh·g~(-1) while the reversible capacity of Li/PPy-coated CuFe_2O_4 electrode increases up to 1106.7 mAh-g~'.A high capacity of 640.7 mAhg"1 for the Li/PPy-coated CuFe_2O_4electrode is maintained in contrast of 398.9 mAh·g~(-1) for CuFe_2O_4 electrode after 60 cycles,which demonstrates good electrochemical performance of the composite due to the increase of electronic conductivity.The electrochemical impedance spectroscopy(EIS) further reveals that the Li/PPy-coated CuFe_2O_4 electrode has a lower charge transfer resistance than the Li/CuFe2C4 electrode.     

氢化物发生-原子荧光光谱法测定钢铁中的痕量铋

采用氢化物发生-原子荧光光谱法测定钢铁中的痕量铋。考察了观察高度、负高压、灯电流、载气流速、屏蔽气流速、介质酸度、载流酸度和硼氢化钾浓度等因素对测定结果的的影响,并优化了测定条件,研究了钢铁材料中常见元素对铋测定的影响。结果表明,用硫脲和抗坏血酸作抑制剂可以消除大量元素的干扰。铋浓度在0～100ng/mL与荧光强度呈良好的线性关系,方法的检出限为0.187ng/g。对20ng/mL的铋标准溶液平行测定10次,相对标准偏差为2.5%。用该方法对国家标准钢样品进行了测定,测定结果与标准值相符合。     

Pressure–volume–temperature equations of state of Au and Pt up to 300 GPa and 3000 K: internally consistent pressure scales

By using a Mie–Grüneisen-type analysis method, the pressure–volume–temperature equations of state (P–V–T EOSs) of Au and Pt have been determined up to 300?GPa and 3000?K based on the experimental shock Hugoniot and thermodynamic data. The calculated results of Au and Pt show an excellent agreement with available experimental volume compression data over a wide range of pressures and temperatures. A comparison of our results with previous theoretical investigations has also been done. In addition, we have further examined the consistency of our results and the P–V–T EOS of MgO [K. Jin, X.Z. Li, Q. Wu, H.Y. Geng, L.C. Cai, X.M. Zhou, and F.Q. Jing, The pressure–volume–temperature equation of state of MgO derived from shock Hugoniot data and its application as a pressure scale, J. Appl. Phys. 107 (2010), pp. 113518] using simultaneous volume measurements of Au, Pt, and MgO at various temperatures. The good agreement among the P–V–T EOSs of Au, Pt, and MgO implies that these EOSs can be used as the reliable pressure scales in high pressure–temperature diamond anvil cell experiments.     

微波消解-氢化物发生原子荧光光谱法测定头发样品中的微量汞

对微波消解-氢化物发生原子荧光光谱法测定头发样品中微量汞的方法进行了研究。采用HNO3和H2O2作消解剂,在最佳微波消解条件和测定条件下,线性回归线方程为Y=259．7c 155.4,相关系数r=0.9996,检出限为0．01ng／mL,线性范围为0-20ng／mL。测定结果的相对标准偏差为0,4％～2．8％,回收率为94,0％-102．0％。     

(α,n)反应中子产额与能谱计算方法

发展了（α,n）反应中子产额与能谱蒙特卡罗直接模拟方法,该方法采用通用的连续碰撞方法与SRIM程序计算的阻止本领模拟α粒子慢化过程,采用基于JENDL/AN-2005加工后ACE格式数据库计算（α,n）反应中子产额与能谱。基于NPTS程序研制了（α,n）反应模拟功能,轻核（α,n）反应产额与实验结果符合较好,B、F、O靶出射中子能谱与实验结果符合较好,而C、Al、Si与实验结果有一定差异。