X-ray measurements of bubble hold-up in fluidized beds with and without vertical internals

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Experimental investigation and simulation of flow boiling of nanofluids in different flow directions

In this work, the flow boiling of TiO₂/water and Al₂O₃/water nanofluids was investigated experimentally and simulated with two phases. Experimental results were obtained in two directions and compared together. The volume fraction and heat transfer coefficient obtained from the vertical tube were compared with those obtained from the horizontal tube. The results showed that the contours of vapor volume fraction in horizontal tube are completely different from the vertical tube, which is due to the buoyancy effect. Moreover, the effect of nanoparticles on both flow directions was almost the same, while heat transfer coefficient was not the same in these flow directions. Based on the experimental result, presence of nanoparticles in the base fluid cannot increase the heat transfer coefficient.     

表面富含羧基的单分散交联聚合物微球的快速自组装制备胶体晶的研究

在20～70℃范围内,用垂直沉积的方法可使表面富含羧基的单分散交联聚合物微球在不同的基底上快速自组装成三维有序的胶体晶.不同粒径的微球形成的胶体晶其光禁带峰位不同,因此可调控不同波长的光在胶体晶中的传播.利用紫外-可见光谱研究了胶体晶的光禁带峰位与组成其微球粒径之间的关系.结果表明,随着构成胶体晶微球粒径的增大,胶体晶光禁带峰位发生了红移,而随着入射光角度的增大,胶体晶的光禁带峰位发生了蓝移.利用原子力显微镜和扫描电子显微镜研究了其它条件对聚合物微球有序排列的影响,发现聚合物微球在pH值为3.0～13.0范围内可以形成三维有序自组装胶体晶.这是由于在不同的pH值下,聚合物微球表面发生羧基化及去羧基化反应,导致在自组装过程中微球之间和微球与介质之间作用力的变化     

1,2,3-三氮杂苯-水复合物氢键相互作用

Density functional theory B3LYP method with 6-31++G** basis was used to optimize the geometries of the ground states for 1,2,3-triazine-(H2O)n (n=1,2,3) complexes. All calculations indicate that the 1,2,3-triazine-water complexes in the ground states have strong hydrogen-bonding interaction, and the complex having a N…H-O hydrogen bond and a chain of water molecules which is terminated by a O…H-C hydrogen bond is the most stable. The H-O stretching modes of complexes are red-shifted relative to that of the monomer. In addition, the Natural bond orbit (NBO) analysis indicates that the intermolecular charge transfer between 1,2,3-triazine and water is 0.0222e, 0.0261e and 0.0273e for the most stable 1:1, 1:2 and 1:3 complexes, respectively. The first singlet (n, π*) vertical excitation energy of the monomer 1,2,3-triazine and the hydrogen-bonding complexes of 1,2,3-triazine-(H2O)n were investigated by time-dependent density functional theory.     

用正问题代码求逆问题的尝试

本文介绍了一种用正问题代码通过某种逆过程来求解逆问题的数值目的。我们使用这种目的在平衡代码SWEQU^[1]的基础上开发了一个名为SWSTAB的计算非圆截面托卡马克等离子体竖直不稳定性的程序。利用该程序我们计算了成型线圈条件下,上下不对称等离子体的竖直不稳定性,研究了等离子体形状因子(椭圆半轴比,三角形变)及等离子体与成型线圈之间距离对稳定性的影响,方便地得到了用其它目的不易得到的物理结果。     

Frost formation in vertical channels under natural convection

Processes involving heat transfer from a humid air stream to a cold plate, with simultaneous deposition of frost, are of great importance in a variety of refrigeration equipment. In this paper, frost growth on a cold, vertical plate in free convection has been experimentally investigated. The cold plate (0.095 m high, 0.282 m wide) was placed in vertical channels open at the top and bottom in order to permit the natural circulation of ambient air. The channels, rectangular in shape, were 2.395 m high and 0.36 m wide, with the depth set equal either to 20 mm, or 10 mm, or 6 mm in order to infer the influence of channel flow area on the natural convection and frost formation. The cold plate temperature and the air relative humidity were varied in the −40 to −4 °C and 31–85% range, respectively, with the air temperature held fixed at 27 °C (±1 °C). Several quantities (thickness, temperature and mass of frost, heat flux at the cold plate), were measured during the time-evolution of the process (7.5 h from the frost growth inception), and are presented as functions of the input parameters (relative humidity and cold plate temperature); in particular, the role exerted by the plate confinement on the frost growth is discussed. Data are recast in order to identify compact parameters able to correlate frost mass, thickness and density data.     

运用PLS算法由小麦冠层反射光谱反演氮素垂直分布

文章提出了利用遥感光谱数据反演小麦冠层氮素垂直分布的化学计量学方法,运用偏最小二乘算法(PLS),穷尽测定的小麦田间冠层可见光和近红外光谱不同波长处的冠层光谱反射率及其组合与小麦不同层次的叶绿素、叶片全氮含量之间的关系。通过2001～2002年的建模和2003～2004年的验证试验,求得了用PLS算法对叶片全氮上层、中层、下层垂直分布估算结果的相关性。表明PLS算法能够用于反演作物冠层生物化学参数的垂直分布。运用PLS的小麦氮素垂直分布的估算方法,较以往单一冠层估算方法精度明显提高,对于生产上迫切需求对作物中、下层叶片氮素状况的监测来指导适时和适量施肥具有指导意义。     

多轴差分吸收光谱技术对冬季大气HONO垂直分布特征研究

HONO作为大气OH自由基的前体物和重要贡献源，影响着大气中污染物的氧化降解，控制着对流层大气的自净能力，对灰霾和光化学烟雾形成起到重要作用，同时受污染排放特征、垂直传输和混合、非均相反应和大气光氧化等影响，HONO具有明显的垂直分布特征，因此探究大气中HONO的垂直分布特征对于了解大气灰霾和光化学污染的形成和控制都十分重要。MAX-DOAS作为一种被动遥感技术，能够快速有效地获取大气中污染物的立体分布特征。采用MAX-DOAS仪器对合肥市科学岛2017年12月冬季大气HONO和NO₂进行了立体探测，通过基于最优估算的气溶胶和痕量气体廓线反演算法PriAM获取了两种气体的垂直分布特征。研究结果表明，在观测期间NO₂在近地面10 m内体积混合比（VMR）和垂直柱浓度(VCD)的范围分别在0.51×1011～20.5×1011 molecules·cm-3和6.0×1015～5.5×1016 molecules·cm-2，在垂直方向上其浓度主要集中在1 km内，且在近地面浓度混合均匀。HONO的VMR和VCD分别在0.03×1010～5.1×1010 molecules·cm-3和3.5×1014～7.0×1015 molecules·cm-2之间，浓度高值出现在100 m内，浓度随高度的升高而明显下降。通过对HONO和NO₂的对比发现，HONO/NO₂比值在0.17%～16.0%（VMR）和1.0%～25.0%(VCD)之间，表明研究期间HONO主要来自于NO₂的转化。对冬季一次典型污染过程（2017.12.26—2017.12.31）分析，HONO/NO₂的比值大于5%，且HONO的浓度值升高（大于0.26×1011 molecules·cm-3），表明污染条件下NO₂向HONO的转化作用变强。结合风场信息研究发现，污染期间研究区域的NO₂和HONO浓度受到合肥市城区、安徽北部和西北部地区传输的影响。     

Qualitative behavior of solutions of Liénard-type systems with state-dependent impulses

State-dependent impulsive differential equations can be used to describe phenomena in which the velocity of an object suddenly changes when the object enters a predetermined state. This study examines the effect of state-dependent impulses on the rotation of all orbits of the Liénard system, which plays an important role in many research areas, including electrical circuits, diverse engineering fields, economics, ecology, and physiology. Determining whether all orbits of the Liénard system other than the origin, which is the only fixed point, rotate around the origin, is the basis of other properties of the orbit and has become a significant research subject; however, very few studies have examined the effects of state-dependent impulses on this behavior, and the main theorem presented in this paper addresses this. This rotation problem is reduced to establishing whether all orbits intersect the vertical isocline, which is discussed in detail. To facilitate the understanding of the proof of the main theorem, an overview is presented before providing the actual proof. The main theorem and some lemmas are proved using phase plane analysis. The application of the main theorem to Euler’s equations is also described.     

Electronic spectra of the linear magnesium-containing carbon chains MgC2nH (n = 1–5): A CASPT2 study

Complete active space self-consistent-field (CASSCF) approach has been used for the geometry optimization of the X²Σ⁺ and A²Π electronic states for the linear magnesium-containing carbon chains MgC_2nH (n = 1–5). Multireference second-order perturbation theory (CASPT2) has been used to calculate the vertical excitation energies from the ground to selected seven excited states, as well as the potential energy curves of two ²Σ⁺ and two ²Π electronic states. The studies indicate that the vertical excitation energies of the A²Π ← X²Σ⁺ transition for MgC_2nH (n = 1–5) are 2.837, 2.793, 2.767, 2.714, and 2.669 eV, respectively, showing remarkable linear size dependence. Compared with the previous TD-DFT and RCCSD(T) results, our estimates for MgC_2nH (n = 1–3) are in the best agreement with the available observed data of 2.83, 2.78, and 2.74 eV, respectively. In addition, the dissociation energies in MgC_2nH (n = 1–5) are also been evaluated.