Profile monitoring of reflow process using approximations of mixture second‐order polynomials

Lately, profile monitoring has received considerable attention in the statistical process control research field. This paper proposes a novel monitoring framework for the reflow process data, which uses two goodness‐of‐fit criteria to select the change points in the mixture polynomial model. Among change points, the mixture second‐order polynomials are utilized to piecewisely approximate the nonlinear profile data of the reflow process. The well‐known Hotelling T² and proposed EWMA₄ control charts are then employed to monitor the parameter estimates. The experimental results demonstrate that the proposed monitoring framework presents better performances in detecting outlying profiles than the conventional methods in phase I. In phase II, the performance of the proposed framework is assessed in terms of the out‐of‐control average run length. Copyright © 2014 John Wiley & Sons, Ltd.     

Characterization of sugar juice heat exchanger tube deposit

Fouling of heat exchanger surfaces during sugar manufacture reduces productivity and increases energy demand. This study characterizes a deposit (including its internal structure) formed in a sugar factory's evaporator unit using a variety of X‐ray diffraction and scanning electron microscopy techniques (including X‐ray powder diffraction, X‐ray fluorescence, elemental mapping with energy dispersive spectroscopy and backscattered electron imaging). Calcium sulfate dihydrate, calcium oxalate mono‐ and dihydrate, hydroxyapatite, amorphous silica and organic matter are present in the deposit. The composition of the deposit (which contains three layers) varies along the height of the tube. There are noticeable differences in the composition and porosity among the layers in the deposit. A porous structure consisting of a mixture of amorphous silica, calcium oxalate dihydrate and organic matter is attached to the surface of the deposit in contact with sugar juice, while a denser morphology of amorphous silica and hydroxyapatite is attached to the tube wall. Elemental mapping identifies an association between Si, Al, Mg, Fe and O, suggesting the presence of a silicate compound as a minor component in the deposit. An attempt is made to rationalize the formation of the observed phases. Copyright © 2010 John Wiley & Sons, Ltd.     

Agglomerated carbon based phases for anion exchange chromatography

Carbon-clad zirconia particles have been converted into ion exchange media through addition of charged latexes after covalent modification of the carbon surface. A variety of methodologies were investigated to introduce a negative charge to the carbon surface in the form of either sulfonate or oxygen containing functionalities (e.g. hydroxyl or carboxylate). Short analytical sized columns (35 mm × 4 mm I.D.) were packed with modified 2 μm nonporous carbon clad zirconia. Addition of the latex particles after the initial packing produced almost double the efficiency for the system compared to adding the latexes before packing. The optimized system could separate mixtures of common inorganic anions with efficiencies greater than of 41,000 plates/m and retention reproducibility of <2% RSD.     

Synthesis and NHE1 inhibitory activity of ligustrazine derivatives

A series of novel derivatives of ligustrazine linked with substituted benzoyl guanidine were synthesized. These compounds have not been reported in literature, and their chemical structures were confirmed by IR, 1H NMR and MS. The results of NHE1 inhibitory activity test showed that compounds I2, I3, I4, I6, and I7 possess more potent NHE1 inhibitory activity than cariporide.     

绵杆纤维的改性(Ⅱ)──氮杂冠醚化纤维素的制备及其对金属离子的吸附性能

经环氧活化的棉杆纤维素醚分别与3-羟基-1，5-二氯杂环庚烷和3-羟基-1，5-二氮杂环辛烷反应，制备了二种氮杂冠醚化棉杆纤维衍生物，测定了它们对金属离子的吸附性能及溶液pH值的影响。结果表明二者对Hg2 ，Cd2 有较好的吸附性能，对Cu2 的吸附-解吸-再吸附实验表明，二种氮杂冠醚化棉杆纤维衍生物具有重复使用的性能。     

Solid‐particle erosion in the tube end of the tube sheet of a shell‐and‐tube heat exchanger

Erosion is one of the major problems in many industrial processes, and in particular, in heat exchangers. The effects of flow velocity and sand particle size on the rate of erosion in a typical shell‐and‐tube heat exchanger were investigated numerically using the Lagrangian particle‐tracking method. Erosion and penetration rates were obtained for sand particles of diameters ranging from 10 to 500 µm and for inlet flow velocities ranging from 0.197 to 2.95 m/s. A flow visualization experiment was conducted with the objective of verifying the accuracy of the continuous phase calculation procedure. Comparison with available experimental data of penetration rates was also conducted. These comparisons resulted in a good agreement. The results show that the location and number of eroded tubes depend mainly on the particle size and velocity magnitude at the header inlet. The rate of erosion depends exponentially on the velocity. The particle size shows negligible effect on the erosion rate at high velocity values and the large‐size particles show less erosion rates compared to the small‐size particles at low values of inlet flow velocities. The results indicated that the erosion and penetration rates are insignificant at the lower end of the velocity range. However, these rates were found to increase continuously with the increase of the inlet flow velocity for all particle sizes. The particle size creating the highest erosion rate was found to depend on the flow velocity range. Copyright © 2005 John Wiley & Sons, Ltd.     

Experimental and computational study of the developed flow field in a flat plate integrated collector storage (ICS) solar device with recirculation

The flow structure in a flat plate integrated collector storage device, with recirculation of the storage water, is studied experimentally and theoretically. To facilitate flow visualization, an experimental device was constructed by transparent material (Plexiglas). Flow velocities and fluctuations are measured, using a LDV system. A three-dimensional CFD-model was developed using the FLUENT code. The standard k–ω model is selected as the most appropriate. The model is validated, with good agreement, against experimental measurements. Furthermore, copper tubes, in the form of embedded heat exchanger, are placed inside the device and another similar 3D model was developed. The model was used to examine the behavior of the system, when the service water enters the heat exchanger, thus being indirectly heated by the stored hot water. It is shown that the outlet temperature of the service water is enough higher, when recirculation occurs.     

S1240交换机的音信号分配与录音通知

作者对Ｓ１２４０数字程控交换中音信号分配原理和分配网络作了阐述，然乒对音信号中录音通知音的应用进行了分析，比较、最后举了设置一个音乐台的实例说明。     

煤油冷却器的BSFD优化设计

管壳式换热器是各种工程领域中最普遍应用的热交换装置，其优化设计可实现满足热交换任务的结构设计、经济性评估等多目标。借助转轴直接搜索可行方向法(DSFD)的思想，计算了油一水换热器的优化设计模型，通过比较并加以分析优化结果与常规设计结果，证明了煤油冷却器的设计既达到了结构合理，经济性好的目的，也具有根据不同需要得到其最优方案的灵活性。     

一起简易换热容器事故分析

由于生活需要将一台原用于储气的立式储气罐改造为一台卧式换热器，因操作不当，导致筒体焊口撕裂。针对这一事故进行分析研究，并对换热器筒壁撕裂处进行了强度校核，指出了压力容器在改造过程中，只有遵守国家有关标准要求，才能保证使用中避免事故的发生。