Characterization of the Residence Time Distribution in Spray Dryers

In this work it is presented a study on the residence time distribution (RTD) of particles in a co-current pilot-plant spray dryer operated with a rotary atomization system. A nuclear technique is applied to investigate the RTD responses of spray dryers. The methodology is based on the injection of a radioisotope tracer in the feed stream followed by the monitoring of its concentration at the outlet stream. The experiments were performed during the drying of aqueous suspensions of gadolinium oxide. The RTD responses obtained experimentally presented good reproducibility, indicating that the technique applied is well suited to investigating fluid-dynamics of spray dryers. In addition to the experimental investigation, a mathematical model was used to describe the RTD experimental curves.     

利用黄河泥沙加固下游大堤

黄河是一条举世闻名的多泥沙河流，善淤、善决、善徒给沿河人民带来对过深重灾难，防洪问题一直是国家的心腹之患。泥沙问题是黄河防洪问题的症结所在。在总结固大堤经验的基础，进行挖河疏浚，淤筑“相对地下河”，已作为黄河治理的一项重大决策付诸实施。     

中国古典园林三维造型研究

论述了采用层次结构化及参数化三维造型方法，建立一个以造型函数库为核心，从而构造各类、各级园林景观构件表面模型的方法和过程。对于某些非建筑类的园林配景构件，采用了Ｆｒａｃｔａｌ方法进行造型。     

A study of CaCO3 fouling with a microscopic imaging technique

The present study introduces a new experimental method to visualize the fouling process of CaCO₃. A mini-channel heat exchanger system with a microscopic imaging technique was developed for real-time visualization of the fouling process. The present study discussed how scale started initially, how scale formed thick layers, and how a small crystal grew into a large one, touching the adjacent one. Detail microscopic images of scale crystals and corresponding fouling resistances were obtained over the entire fouling process. The microscopic observation indicated that the fouling process could be divided into three stages: an induction period, a period of uniform generation of nuclei, and a period of uniform growth of scale. Sudden appearance of numerous small nuclei indicated the end of the induction period, a key event before the rapid increase in the fouling resistance. The present experimental method using microscopic images of the wet fouling process provides a valuable insight on the fouling mechanism.     

Clarification of a wheat straw‐derived medium with ion‐exchange resins for xylitol crystallization

BACKGROUND: Xylitol bioproduction from lignocellulosic residues comprises hydrolysis of the hemicellulose, detoxification of the hydrolysate, bioconversion of the xylose, and recovery of xylitol from the fermented hydrolysate. There are relatively few reports on xylitol recovery from fermented media. In the present study, ion‐exchange resins were used to clarify a fermented wheat straw hemicellulosic hydrolysate, which was then vacuum‐concentrated and submitted to cooling in the presence of ethanol for xylitol crystallization. RESULTS: Sequential adsorption into two anion‐exchange resins (A‐860S and A‐500PS) promoted considerable reductions in the content of soluble by‐products (up to 97.5%) and in medium coloration (99.5%). Vacuum concentration led to a dark‐colored viscous solution that inhibited xylitol crystallization. This inhibition could be overcome by mixing the concentrated medium with a commercial xylitol solution. Such a strategy led to xylitol crystals with up to 95.9% purity. The crystallization yield (43.5%) was close to that observed when using commercial xylitol solution (51.4%). CONCLUSION: The experimental data demonstrate the feasibility of using ion‐exchange resins followed by cooling in the presence of ethanol as a strategy to promote the fast recovery and purification of xylitol from hemicellulose‐derived fermentation media. Copyright © 2008 Society of Chemical Industry     

Preparation, sintering, and microstructures of strontium barium bismuth tantalate layered perovskite ceramics

The solid solutions of Ba-doped SrBi₂Ta₂O₉ layered perovskite ceramic powders have been successfully prepared via a two-step process using BiTaO₄ as a precursor. The lattice constants of the solid solutions monotonically increase with increasing barium-ion content. The sinterability of (Sr_1–xBa_x)Bi₂Ta₂O₉ powders is significantly improved by increasing the barium-ion content. When the specimens with high barium-ion contents are sintered at 1100°C, they thermally decompose to form rod-like grains and the matrix expands, leading to a lower density. The addition of barium ions to SrBi₂Ta₂O₉ also results in significant variation in the morphology of the sintered specimens and the occurrence of c-axis preferred orientation which is ascribed to the anisotropic growth of plate-like grains. The precise control of the barium-ion content as well as the sintering conditions is critical for obtaining densified barium-ion doped SrBi₂Ta₂O₉ ceramics with a pure, layered perovskite structure.     

上海外环隧道水下最终接头的施工技术

沉管隧道采用水下最终接头,可以大大缩短工期和减少成本,但施工难度较大,而且有一定风险。文章以上海外环隧道工程为例,对沉管隧道水下最终接头的施工工艺中管段轴线精度控制、安装保护罩、间隙间的安全排水和混凝土施工等四大难点进行探讨,并介绍了水密性施工和管内结构施工的具体工艺和步骤。指出其成果对今后类似工程具有较大的参考价值。     

Fluorescence and IR characterization of epoxy cured with aliphatic amines

Cure reactions of the stoichiometric mixtures of diglycidyl ether of bisphenol A (DGEBA) and two very low molecular weight aliphatic polyether diamines (PED) were studied by using fluorescence and mid- and near-IR spectroscopic techniques. As the cure proceeded, the primary amine groups in PED are converted to the secondary and the tertiary amines. Near-IR spectral analysis was used to calculate the concentration of the three amine groups as a function of cure time. The decrease in the fluorescence intensity of DGEBA at about 307 nm was observed due to more effective quenching of the tertiary amine groups in PED, in comparison to the primary and the secondary amine groups. A large decrease in fluorescence intensity at 75 and 95 °C cure was observed. The amount of all the amine species was estimated from NIR spectra to shed light on the cure kinetics of PPO (polypropylene oxide) in comparison with PEO (polyethylene oxide) epoxy, as well as to explain their fluorescence behavior.The fluorescence intensity changes were correlated to the extent of epoxy reaction obtained by mid- and near-IR spectroscopy.     

Stochastic molecular descriptors for polymers. 4. Study of complex mixtures with topological indices of mass spectra spiral and star networks: The blood proteome case

The Quantitative Structure-Property Relationships (QSPRs) based on Graph or Network Theory are important for predicting the properties of polymeric systems. In the three previous papers of this series (Polymer 45 (2004) 3845-3853; Polymer 46 (2005) 2791-2798; and Polymer 46 (2005) 6461-6473) we focused on the uses of molecular graph parameters called topological indices (TIs) to link the structure of polymers with their biological properties. However, there has been little effort to extend these TIs to the study of complex mixtures of artificial polymers or biopolymers such as nucleic acids and proteins. In this sense, Blood Proteome (BP) is one of the most important and complex mixtures containing protein polymers. For instance, outcomes obtained by Mass Spectrometry (MS) analysis of BP are very useful for the early detection of diseases and drug-induced toxicities. Here, we use two Spiral and Star Network representations of the MS outcomes and defined a new type of TIs. The new TIs introduced here are the spectral moments (π_k) of the stochastic matrix associated to the Spiral graph and describe non-linear relationships between the different regions of the MS characteristic of BP. We used the MARCH-INSIDE approach to calculate the π_k(SN) of different BP samples and S2SNet to determine several Star graph TIs. In the second step, we develop the corresponding Quantitative Proteome-Property Relationship (QPPR) models using the Linear Discriminant Analysis (LDA). QPPRs are the analogues of QSPRs in the case of complex biopolymer mixtures. Specifically, the new QPPRs derived here may be used to detect drug-induced cardiac toxicities from BP samples. Different Machine Learning classification algorithms were used to fit the QPPRs based on π_k(SN), showing J48 decision tree classifier to have the best performance. These results suggest that the present approach captures important features of the complex biopolymers mixtures and opens new opportunities to the application of the idea supporting classic QSPRs in polymer sciences.