The effect of the surface tension on non-propagating solitary waves

In this paper, the effect of the surface tension is considered carefully in the study of non-propagating solitary waves. The parameter plane of the surface tension and the fluid depth is divided into three regions; in two of them a breather soliton can be produced. In literature the parameters of breather solitons are all in one of the parameter regions. The new region reported here has been confirmed by our experiments. In the third region, the theoretical solution is a kink soliton, but a kind of the non-propagating solitary wave similar to the breather soliton was found in our experiments besides the kink soliton.

氢/空气火焰在半开口有障碍管道中的传播特性

针对氢/空气混合物，通过实验研究了其预混火焰在半开口管道中的火焰传播加速现象。结果表明，火焰传播状态随着氢气当量比的变化而发生改变。当氢/空气混合物被点燃后，由于障碍物的扰动，火焰在管道中不断加速传播，并最终到一准稳态传播。在氢气当量比0.34附近时，火焰速度发生跃变。当氢气当量比足够大时，火焰传播由爆燃态转变为爆轰态。在本实验条件下，爆燃转准爆轰的临界条件是d/λ ≥ 2.6（d是圆环形障碍物内径，λ是爆轰格胞尺度）。障碍物阻塞比的变化对最大火焰速度和压力提升的影响不明显。

Computation of flow over a rotating body on unstructured Chimera mesh

Flow around moving boundary is ubiquitous in engineering applications. To increse the efficienly of the algorithm to handle moving boundaries is still a major challenge in Computational Fluid Dynamics (CFD). The Chimera grid method is one type of method to handle moving boundaries. A concept of domain de-composition has been proposed in this paper. In this method, sub-domains are meshed independently and governing equations are also solved separately on them. The Chimera grid method was originally used only on structured (curvilinear) meshes. However, in a problem which involves both moving boundary and complex geometry, the number of sub-domains required in a traditional (structured) Chimera method becomes fairly large. Thus the time required in the interior boundary locating, link-building and data exchanging also increases. The use of unstructured Chimera grid can reduce the time consumption significantly by the reduction of domain(block) number. Generally speaking, unstructured Chimera grid method has not been developed. In this paper, a well-known pressure correction scheme - SIMPLEC is modified and implemented on unstructured Chimera mesh. A new interpolation scheme regarding the pressure correction is proposed to prevent the possible decoupling of pressure. A moving-mesh finite volume approach is implemented in an inertial reference frame. This approach is then used to compute incompressible flow around a rotating circular and elliptic cylinder. These numerical examples demonstrate the capability of the proposed scheme in handling moving boundaries. The numerical results are in good agreement with other experimental and computational data in literature. The method proposed in this paper can be efficiently applied to more challenge cases such as free-falling objects or heavy particles in fluid.

Cloning of cDNAs encoding C-type lectins from Elapidae snakes Bungarus fasciatus and Bungarus multicinctus

A number of C-type lectins with various biological activities have been purified and characterized from Viperidae snake venoms. In contrast, only a few reports could be found in literature concerning the C-type lectins in Elapidae snake venoms. Based on t

Effect of beta-irradiation on photoluminescence of MOCVD grown GaN

The effect of beta particles interaction on the optical properties of MOCVD grown GaN is reported. A significant change in luminescence properties of GaN is observed after exposing the material with 0.6 MeV beta particles with low dose of 10(12) cm(-2). The results obtained from photoluminescence measurements of irradiated GaN samples in low dose are found contradictory to those reported in literature for samples irradiated with heavy dose (> 10(15) cm(-2)) of electron. An increase in intensity of yellow luminescence has been observed with increasing dose of beta particles which is in disagreement to the already reported results in literature for heavily irradiated samples. A model has been proposed to sort out this inconsistency. The increase in YL intensity at low dose is attributed to the increase in concentration of VGaON complex whereas production of non-radiative VGaON clusters is assumed to justify the decrease in YL intensity at high dose.

Solving MIN UR problem by triangle evolution algorithm with archiving and niche techniques

In this paper, as an extension of minimum unsatisfied linear relations problem (MIN ULR), the minimum unsatisfied relations (MIN UR) problem is investigated. A triangle evolution algorithm with archiving and niche techniques is proposed for MIN UR problem. Different with algorithms in literature, it solves MIN problem directly, rather than transforming it into many sub-problems. The proposed algorithm is also applicable for the special case of MIN UR, in which it involves some mandatory relations. Numerical results show that the algorithm is effective for MIN UR problem and it outperforms Sadegh's algorithm in sense of the resulted minimum inconsistency number, even though the test problems are linear.

Preparation and Characterization of Melt Grafting 2-acrylamido-2-methyl-1-propanesulfonic Acid onto Pre-Irradiated Linear Low Density Polyethylene

Linear low density polyethylene (LLDPE) was functionalized with 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) by using -ray pre-irradiation in air in a twin-screw extruder. Fourier-transformed infrared spectroscopy (FT-IR) and electron spectroscopy for chemical analysis (ESCA) were used to characterize the formation of LLDPE-g-AMPS copolymers. The content of AMPS in LLDPE-g-AMPS was determined by using element analysis instrument. The effects of concentrations of monomer, reaction temperature and pre-irradiation dose on degree of grafting were investigated. The critical surface tension of LLDPE-g-AMPS was measured by using contact angle method. The influences of the degree of grafting on crystallization properties were studied by using DSC. Compared with neat LLDPE, the crystallization temperature increased about 4C, and crystallinity decreased with increasing degree of grafting. Crystallization rates of grafted LLDPE were faster than that of plain LLDPE at the same crystallization temperature.

Preparation and properties of a reactive type nonionic surfactant grafted linear low density polyethylene

A reactive type nonionic surfactant, monostearic acid monomaleic acid glycerol diester (MMGD) was synthesized in our laboratory. Grafting-copolymerization of linear low density polyethylene ( LLDPE) with MMGD was carried out by using beta ray irradiation in air in a twin-screw extruder. Evidence of the grafting of MMGD as well as its extent was determined by Fourier-transformed infrared (FT-IR) spectroscopy. The effects of monomer concentration, reaction temperature and screw run speed on degree of grafting were studied systematically. The thermal behavior of LLDPE-g-MMGD was investigated by using differential scanning calorimety ( DSC). Compared with neat LLDPE, the crystallization temperature ( Tc) of LLDPE-g-MMGD increased about 3 degrees C, and the melting enthalpy (Delta H-m) decreased with increase of MMGD content. It showed that the grafted MMGD monomer onto LLDPE acted as a nucleating agent. The tensile properties and light transmission of blown films were determined. Comparing with neat LLDPE film, no obvious changes could be found for the tensile strength, elongation at break and right angle tearing strength of LLDPE-g-MMGD film. The wettability is expressed by the water contact angle. With an increasing percentage of MMGD, the contact angles of water on film surface of LLDPE- g-MMGD decrease monotonically.

The effect of chain flexibility and chain mobility on radiation crosslinking of polymers

Radiation crosslinking of polymers mainly depends on the structure of polymer chain. The flexibility and mobility of chain directly influence the possibility of the reactive radicals recombination. Flexible chain is easier to crosslink than rigid-chain polymer. The latter must be crosslinked at high temperature, as most polymers can only crosslink above their melting point. Structural effect also influences the mechanism of radiation crosslinking of polymers. We find from the results in literature and in our laboratory that, the flexibility chain polymer mainly crosslinked with H type, but the rigid chain polymer mainly crosslinked with Y type. (C) 2001 Published by Elsevier Science Ltd.

C-13 NMR study on the aqueous structure of lanthanide citrate complexes

The aqueous complexation of lanthanide complexes of citrate in pH 7.4 solutions has been studied by using lanthanide-induced shift and relaxation times measurement methods. These results indicate that citrate coordinate via 3-hydroxyl and 3-carboxylate groups with lanthanide ions and form 1:2 (Ln/cit) isostructural complexes through lanthanide series. We suggest a new coordination geometry which is different from that described in literature.

贡嘎山地区大气中不同形态汞的分布规律及影响因素

汞是一种有毒的人体非必需重金属元素，是一种全球性污染物。大气在全球汞生物地球化学循环中占极其重要的地位，20世纪80年代末和90年代初，在没有人为和自然汞污染源的北欧和北美偏远地区的大片湖泊中发现的鱼体高甲基汞负荷就是由人为排放的汞通过大气长距离迁移后的沉降造成的。我国被认为是全球汞排放最多的国家，大量的汞排放到大气中势必会造成不同形态大气汞浓度以及大气汞沉降通量的升高，然而就目前而言，国内关于长时间分辨率的大气汞分布规律及汞沉降通量的系统研究还比较缺乏。 2005年5月到2007年5月，采用高时间分辨率大气自动测汞仪、镀KCl石英扩散管和颗粒汞微型捕汞管对贡嘎山地区大气中的气态总汞（TGM）、活性气态汞（RGM）和颗粒汞（TPM）进行了为期2年的系统监测；同时，系统的采集分析了贡嘎山地区的大气降水、植物叶片和河流水体样品，对大气汞的干、湿沉降进行了研究，并初步探讨了贡嘎山地区汞的输入和输出。主要得到以下结论： （1） 贡嘎山大气本底站两年的大气气态总汞的几何平均浓度为3.94±1.16 ng m-3，显著高于欧洲和北美同类型地区的大气气态总汞浓度，但和亚洲一些同类型地区的监测结果较为一致；和国内城市等受人为污染区域的大气气态总汞浓度相比，贡嘎山的浓度明显偏低，但略高于长白山大气本底站的气态总汞年均浓度。以上说明，贡嘎山地区的监测结果基本上反映了亚洲特别是我国西南偏远地区的大气汞的含量水平，说明我国人为活动的汞排放，已经造成了一定程度的大气汞污染。 （2） 活性气态汞和颗粒汞表现出和气态总汞不一致的分布特征，贡嘎山地区的活性气态汞平均浓度为6.2±3.9 pg m-3，颗粒汞的平均浓度为30.7±32.1 pg m-3，分别占到大气总汞的0.2%和0.8%，和国外偏远地区的研究结果一致。而活性气态汞和颗粒汞较高的沉降速率和较短的大气迁移距离是导致活性气态汞和颗粒汞偏低的主要原因。 （3） 贡嘎山不同功能区（特别是取暖季节）的大气气态总汞浓度明显高于全球背景区的平均浓度，且具有显著的空间分布特征：城区（8.63~22.5 ng m-3）>乡镇（4.74 ng m-3）>村落（2.55~8.83 ng m-3）>区域参照点（1.65~3.57 ng m-3）。 （4） 西南地区较高的汞释放背景是贡嘎山地区大气气态总汞偏高的一个重要原因；另外，石棉地区的金属冶炼活动、城市等人口集中地区的汞释放是造成该地区大气气态总汞浓度升高的区域性污染源。 （5） 气态总汞和颗粒汞表现出冬季>秋季>春季>夏季的季节性分布规律，而活性气态汞的季节性分布规律为春季>秋季>夏季>冬季。影响气态总汞和颗粒汞季节性变化的因素有释放源强度、气象条件（特别是风向）、光化学反应和干沉降速率的季节性变化；而活性气态汞的季节性变化则可能与大气光化学反应速率以及湿沉降的季节性变化有关。 （6） 贡嘎山地区海拔1600米和3000米空旷处的大气降水的湿沉降通量分别为9.1和26.1 μg m-2 yr-1，而森林地区的湿沉降通量可达57.0 μg m-2 yr-1；贡嘎山地区大气汞的干沉降通量51.9 μg m-2 yr-1，其中约15.9 μg m-2 yr-1(31 %)来自于植物落叶的沉降。 （7） 贡嘎山地区是大气汞的汇，仅泸定县的年均大气汞净沉降量就达142 kg yr-1，且绝大部分（>95%）进入了森林生态系统，而非森林地区的大气汞输入和输出则基本平衡。