Preparation of TiO2 nano-particle photocatalysts by a multi-gelation method: the effect of pH change

TiO₂ photocatalysts were prepared by a multi-gelation method and the effect of the changes in the pH during the pH swing times, i.e., by a controlled pH swing, on the morphology of the TiO₂ particles was investigated. The photocatalytic properties of the TiO₂ catalysts prepared by controlled pH swing were compared with TiO₂ particles prepared without adjusting the pH during the swing times. The photocatalytic degradation reaction of these TiO₂ catalysts was investigated by comparing their effectiveness in 2-propanol oxidation. The experimental results showed that the TiO₂ photocatalysts prepared without adjusting the pH performed better in controlling the important parameters of the catalysts such as particle size, surface area, anatase/rutile phase ratio and pore size, as well as pore volume than the TiO₂ photocatalysts prepared by a controlled pH swing method. Deceased.     

Exercising flexible load contracts: Two simple strategies

A flexible load contract is a type of swing option where the holder has the right to receive a given quantity of electricity within a specified period, at a fixed maximum effect (delivery rate). The contract is flexible, in the sense that delivery (the take hours) is called one day in advance. We investigate two simple strategies for exercising flexible load contracts, where both use price information from the forward market. For 10 contracts traded in the period 1997–2001, we calculate the performance of the two strategies and compare with the reported performance of one complex dynamic programming approach as well as the actual results obtained by three anonymous market participants. The comparison indicates that our simple computer‐efficient strategies perform better on average and produce more stable results. Copyright © 2007 John Wiley & Sons, Ltd.     

Adsorptive separation in the enhancement of butene dehydrogenation

Fixed-bed columns containing solid catalysts and adsorbents were employed for simultaneous reaction and separation. The models developed for butene dehydrogenation reaction were validated with experimental data. The model was then employed for variable bed configurations with and without the effect of pressure and vacuum swing reaction (PSR and VSR). The models for the mass and momentum transfer in the catalyst bed and adsorber were solved using orthogonal collocation within the method of lines. The reactor/separator performances were tested for beds with varying numbers of layers of catalysts and adsorbents arranged sequentially. The reaction columns behaved as reactor/separators in series. As the number of layers increased, a homogeneous distribution of the catalyst and adsorbent was approached in the limit. These configurations with variable catalyst/adsorbent distributions were investigated in terms of product purity, selectivity, conversion, recovery and yield. Improved reactor performance was observed with pressure and vacuum swing separation systems and in particular with close to well-mixed reactor/separator configurations.     

Graphical approach for complex PSA cycle scheduling

A simple graphical approach for complex pressure swing adsorption (PSA) cycle scheduling has been developed. This new methodology involves a priori specifying the cycle steps, their sequence, and the number of beds, and then following a systematic procedure that requires filling in a 2-D grid based on a few simple rules, some heuristics and some experience. The outcome or solution is a grid comprised of columns that represent the total cycle time, rows that represent the total number of beds, and cells that represent the duration of each cycle step, i.e., the complete cycle schedule. This new approach has been tested successfully against several cycle schedules taken from the literature, including a two-bed four-step Skarstrom cycle, a four-bed nine-step process with two equalization steps, a nine-bed eleven-step process with three pressure equalization steps, and a six-bed thirteen-step process with four pressure equalization steps and four idle steps. This approach also revealed the existence of numerous cycle schedules for each bed and cycle step combination examined. Although it cannot identify the total number of permutations or which one is better, it does provide a very straightforward way to determine some of the possible cycle schedules of virtually any PSA process that can be conceived.     

腔QED技术实现最优非对称经济型1到3的相位协变克隆方案

本文提出一个在腔QED中实现最优非对称经济型1到3相位协变克隆的可行性方案,这种克隆不需要辅助粒子.在这个方案中,三个原子中的两个同时与腔场发生作用,并且受经典场的作用.此方案不受腔场的态和腔衰变的影响,因此,在实验上是可能实现的.     

摇摆状态下捷联惯导系统初始对准技术的研究

研究了摇摆状态下捷联惯导系统的初始对准技术,提出了一种新的对准方案:将初始对准作为一种工作状态嵌入到导航解算中,利用姿态解算构建的“数学平台”来隔离基座的摇摆运动,同时采用二阶调平、方位误差估算方法完成初始对准。通过计算机仿真和三轴转台摇摆实验证明该方案可以有效实现摇摆状态下的对准。     

Direct Phosphorylation of Benzothiazoles and 4-Methyltthiazole

Simple procedures for preparation of 2-(4-methylthiazolyl) dichlorophosphine and wide variety of 2-phosphorylated benzothiazoles are reported. Efficient promoters and catalysts were found for the key transformation, direct phosphorylation of the heterocyclic compounds by PCl₃ (PB_r3 as a promoter) or by P(V) acid chlorides (HgCl₂ as a catalyst).     

Economical cascadic multigrid method (ECMG)

In this paper,an economical cascadic multigrid method is proposed.Compared with the usual cascadic multigrid method developed by Bornemann and Deuflhard,the new one requires less iterations on each level,especially on the coarser grids.Many operations can be saved in the new cascadic multigrid algorithms.The main ingredient is the control of the iteration numbers on the each level to preserve the accuracy without over iterations.The theoretical justification is based on the observations that the error reduction rate of an iteration scheme in terms of the smoothing property is no longer accurate while the iteration number is big enough.A new formulae of the error reduction rate is employed in our new algorithm.Numerical experiments are reported to support our theory.     

Oxygen Selectivity on Na-A Type Zeolite at Low Temperature

Na-A type zeolite (Na-A) shows favorable selectivity for nitrogen in an oxygen-nitrogen bi-component system at room temperature and also it is known that oxygen selectivity is dominated by differences in adsorption rates. In this study, the oxygen adsorption behavior of Na-A pellets at low temperature was evaluated. When temperature decreased, oxygen selectivity was enhanced as a result of the difference in adsorption rates. It was also strongly suggested that the oxygen equilibrium adsorbed amount of Na-A pellets was larger than that of nitrogen below 213 K. Na-A pellets are expected to be a good oxygen adsorbent for oxygen-nitrogen separation from air by pressure swing adsorption (PSA).     

以低温热为热源的再沸器(火用)经济优化与传热强化

精馏塔再沸器是炼油、化工、轻工等行业中非常重要的换热设备,这种再沸器的优化和传热强化对热能的优化利用具有重要意义.本文运用经济学方法和传热强化技术,对以低温热为热源的再沸器进行优化设计,建立了同时考虑传热损、流动损和传热强化的再沸器经济优化目标函数和约束条件.并给出了应用实例.