Simultaneous determination of cation exchange capacity and surface area of acid activated bentonite powders by methylene blue sorption

To distinguish the ion exchanged and physically adsorbed methylene blue cations (MB⁺) on ionic surfaces, acid activated bentonite samples were used as porous adsorbents. A natural calcium bentonite (CaB) sample from Enez/Edirne, Turkey, was acid activated at 90 °C for 16 h with various HCl/CaB ratios. The irreversible exchange and physical adsorption of MB⁺ cations on the ionic solids have simultaneously occurred. The ion exchanged (m_ex) and physically adsorbed (m_ad) MB⁺ contents were obtained as the values of sorption capacity at c = 0 and the increase to a plateaus of adsorption isotherms, respectively. The m_ad value was taken to be monolayer adsorption capacity. Cation exchange capacity (CEC) and specific surface area (S_MB) for each sample were calculated from the m_ex and m_ad values, respectively. Also, the BET specific surface areas (S_BET) and pore size distribution were determined from low temperature nitrogen adsorption/desorption data. A linear correlation between the S_MB and S_BET values was found.     

用微扰理论推算超临界流体比定容热容

本文利用统计热力学中的BH微扰理论建立数学模型,推算了Ar超临界区域比定容热容,与文献值比较平均偏差为9.54%。引入了修正函数,重新对比热容公式进行推导,再次对Ar超临界区域部分比定容热容进行计算,计算平均偏差0.39%。对CO、CO₂、CH₄等其余11种简单气体的超临界比定容热容进行计算,平均偏差在1%左右。最后给出了计算中各物质势能参数值。     

带环状翅片管式相变储热器的数值模拟

相变材料的低导热性是相变储热器传热过程的主要障碍。在相变材料侧进行强化,是目前提升相变储热器蓄热速率的主要方法。本文采用有限容积法对带有环状翅片的管式相变储热器的蓄热过程进行了数值模拟,得到了温度场、相界面随时间的变化。在此基础上,本文对翅片导热系数、翅片厚度和翅片间距等影响储热速率的因素进行了计算和分析。为相变储热器的优化设计提供了一定的参考。     

Review of recent advances in the preparation of organic polymer monoliths for liquid chromatography of large molecules

In recent years the use of monolithic polymers in separation science has greatly increased due to the advantages these materials present over particle-based stationary phases, such as their relative ease of preparation and good permeability. For these reasons, these materials present high potential as stationary phases for the separation and purification of large molecules such as proteins, peptides, nucleic acids and cells. An example of this is the wide range of commercial available polymer-based monolithic columns now present in the market.     

MIMO信道容量的研究与仿真

MIMO技术可以在不增加带宽和发射功率的情况下提高信道容量和频谱利用率。本文使用MATLAB建立SISO、SIMO、MISO、MIMO等无线信道,进行综合仿真并分析。通过仿真,我们得知,MIMO不但能有效地提高信道的容量,同时可以改善信道的平均信道容量和中断信道容量。     

Investment in electricity networks with transmission switching

We consider the application of Dantzig-Wolfe decomposition to stochastic integer programming problems arising in the capacity planning of electricity transmission networks that have some switchable transmission elements. The decomposition enables a column-generation algorithm to be applied, which allows the solution of large problem instances. The methodology is illustrated by its application to a problem of determining the optimal investment in switching equipment and transmission capacity for an existing network. Computational tests on IEEE test networks with 73 nodes and 118 nodes confirm the efficiency of the approach.     

单位圆内代数体函数的充满圆及Borel半径

研究了单位圆内具有有限个分支点的代数体函数,并用覆盖曲面的几何方定义了他们的级和Borel半径,得到了在单位圆内大于1的有穷级代数体函数必存在充满圆及Borel半径.     

Atomic decomposition and boundedness criterion of operators on multi-parameter hardy spaces of homogeneous type

The main purpose of this paper is to derive a new ( p, q)-atomic decomposition on the multi-parameter Hardy space Hp (X1 × X2 ) for 0 p0 p ≤ 1 for some p0 and all 1 q ∞, where X1 × X2 is the product of two spaces of homogeneous type in the sense of Coifman and Weiss. This decomposition converges in both Lq (X1 × X2 ) (for 1 q ∞) and Hardy space Hp (X1 × X2 ) (for 0 p ≤ 1). As an application, we prove that an operator T1, which is bounded on Lq (X1 × X2 ) for some 1 q ∞, is bounded from Hp (X1 × X2 ) to Lp (X1 × X2 ) if and only if T is bounded uniformly on all (p, q)-product atoms in Lp (X1 × X2 ). The similar boundedness criterion from Hp (X1 × X2 ) to Hp (X1 × X2 ) is also obtained.     

Crystal structure and thermochemical properties of bis（1-octylammonium） tetrachlorochromate phase change materials

A new crystalline complex(C8 H17 NH3) 2 CdCl 4(s)(abbreviated as C8Cd(s)) is synthesized by liquid phase reaction.The crystal structure and composition of the complex are determined by single crystal X-ray diffraction,chemical analysis,and elementary analysis.It is triclinic,the space group is P-1 and Z = 2.The lattice potential energy of the title complex is calculated to be U POT(C 8 Cd(s))=978.83 kJ·mol-1 from crystallographic data.Low-temperature heat capacities of the complex are measured by using a precision automatic adiabatic calorimeter over a temperature range from 78 K to 384 K.The temperature,molar enthalpy,and entropy of the phase transition for the complex are determined to be 307.3±0.15 K,10.15±0.23 kJ·mol-1,and 33.05±0.78 J·K-1 ·mol-1 respectively for the endothermic peak.Two polynomial equations of the heat capacities each as a function of temperature are fitted by using the leastsquare method.Smoothed heat capacity and thermodynamic functions of the complex are calculated based on the fitted polynomials.