基于Google Earth的建筑物三维建模

利用Google Earth可以进行三维地形浏览,但对于建筑物大部分地区只能看到顶视图,虽然在国外某些地区可看到三维建筑模型,但只建立了"火柴盒"式的简单模型;建筑草图大师Sketch Up为我们提供了一款构建三维建筑模型的软件,通过上传三维模型到Google服务器,就可以弥补Google Earth在三维表达方面的缺陷,使Google Earth软件功能更加完善.     

Preparation of solid acid catalyst packing AAO/SBA-15-SO3H and application for dehydration of xylose to furfural

The solid acid catalyst packing AAO/SBA-15-SO₃H was prepared by the co-condensation and grafting method with porous anodic aluminum oxide (AAO) as support. FT-IR, SEM and TEM were applied to characterize the prepared samples. Results showed that catalysts prepared by two methods both contained active centers, and SBA-15 nanorod arrays grow inside a porous alumina membrane AAO and are perpendicular to the substrate. Their catalytic performances were tested for dehydration of xylose to furfural. The conversion of xylose and selectivity of furfural were 90% and 74% on the AAO/SBA-15-SO₃H(C) catalyst prepared by the co-condensation method, respectively. The deactivation and regeneration of the AAO/SBA-15-SO₃H(C) catalyst for the dehydration of xylose were also investigated, the activity of catalyst treated by 30 wt.% H₂O₂ almost was recovered.     

Particle dynamics analysis in bend in a horizontal-vertical pneumatic conveying system with oscillatory flow

The pneumatic system is frequently operated in the high air velocity region, which aggravates the power consumption and erosion of bend, and the intensive study of the particles motion characteristic on a horizontal-vertical pneumatic conveying in various curved 90° bends is necessary. This experimental study focuses on the particles motion characteristic of bend on the horizontal-vertical pneumatic conveying with oscillatory flow (generated by installing the oscillator) in terms of on pressure drop, powder consumption, the evolution of particle velocity and particle fluctuating intensity during flowing through bends. The results indicate that powder consumption can be reduced by using oscillatory flow, which is more obvious with a larger radius ratios bend. Meanwhile, the pressure drop proportion of bend is higher than average pressure drop of the system within the same distance. Otherwise, the total reduction particles velocity through bend is less while using oscillatory flow, which is more obvious using larger radius ratios bend. The particle velocity using oscillatory flow is higher than that of the conventional pneumatic conveying for the cases of larger radius ratios bend, and this effect is less evident while through a smaller radius bend.     

Reaction Characteristics of Polysaccharide-Iodine Complexes: A Mini-review

The potential reactions between natural polysaccharides and iodine and their products have been explored for a long time. Due to the complex factors that can influence these reactions, a clear-cut mechanism has not yet been developed. Starch-iodine complexes, especially the amylose-iodine complex, are the most investigated of the polysaccharide-iodine reactions, and the study of this reaction can be used as a basis for the investigation of other polysaccharide-iodine reactions. In this paper, significant aspects of the reaction were introduced, including the influence of the polysaccharide structure on the properties of the resulting complexes, the relationship between the concentration of CaCl_2 and formation of the final products, as well as the form of the polyiodides in these complexes. The interior structure and the surface morphology of the complexes were discussed, along with the progress in research related to this reaction.     

Experimental study of a micro-scale solar organic Rankine cycle system based on compound cylindrical Fresnel lens solar concentrator

In the present study, a micro-scale solar organic Rankine cycle power generation system was developed. The system comprises of a solar collection system based on compound cylindrical Fresnel lens concentrator and an organic Rankine cycle power generation system integrated with a scroll expander. YD320 and R245 fa were used as the heat transfer fluid and the working fluid, respectively. The effects of the evaporation pressure, the degree of superheat, and the mass flow rate of the working fluid were analyzed to evaluate the solar collection efficiency, the electric power output, the thermal efficiency and exergy efficiency of the system. The results illustrate that both the increasing evaporation pressure and decreasing superheat degree have positive impacts on solar collection efficiency. The electric power increases as the evaporation pressure increases, while the thermal efficiency and the exergy efficiency decrease. However, the system overall efficiency decreases slowly due to the increase of solar collection efficiency. The electric power increases with the increment of the working fluid mass flow rate. The increasing mass flow rate has no visible impact on the thermal and exergy efficiencies of organic Rankine cycle subsystem, whereas a slightly increase of the thermal and exergy efficiencies of the integrated system. The electric power decreases with the increase of the superheat degree, whereas the thermal and the exergy efficiencies of the system increase. The system works more suitably with a higher degree of superheat for the small mass flow rate condition.     

Conditional median run length performance of the synthetic X¯ chart with unknown process parameters

Synthetic-type charts are efficient tools for process monitoring. They are easy to design and implement in practice. The properties of these charts are usually evaluated under the assumption of known process parameters. This assumption is sometimes violated in practice, and process parameters have to be estimated from different phase I data sets collected by different practitioners. This fact causes the between-practitioners variability among the properties of the synthetic-type charts designed for each practitioner. In fact, the shape of the run length distribution of the synthetic-type charts changes with the mean shift size. As a good alternative, the median run length $(MRL)$ metric is argued to evaluate the properties of different control charts. In this paper, the $MRL$ is used as a measure of the synthetic $\overline{X}$ chart's performance, and the conditional $MRL$ properties of the synthetic $\overline{X}$ chart with unknown process parameters are investigated. Both the average $MRL$ ( $AMRL$) and the standard deviation of $MRL$ ( $\text{◂⋅▸}SDMRL$) are used together to investigate the chart's properties when the process parameters are unknown. If the available number of phase I samples is not large enough to reduce the variability of the in-control $MRL$ values to an acceptable level, a bootstrap-type approach is suggested to adjust the control limits of the synthetic $\overline{X}$ chart and to further prevent many unwanted lower in-control $MRL$ values.     

Dynamic analysis of particles in vertical curved 90° bends of a horizontal-vertical pneumatic conveying system based on POD and wavelet transform

The pneumatic system is frequently operated in the high air velocity region, which aggravates the power consumption and erosion of bend, and the dynamic analysis of particles in bends with different radius of curvature in a horizontal-vertical pneumatic conveying system is necessary. This experimental study focuses on the particle motion characteristic of bend on the horizontal-vertical pneumatic conveying in terms of on pressure drop, particle velocity, power spectral characteristics of particle fluctuation velocity, the energy distribution of the proper orthogonal decomposition (POD) modes, time coefficients of POD, and spatial mode of POD mode during flowing through bends. The results indicate that the particle rope is the large-scale motion of particles containing high energy, which dominates the motion of particles in the bend, and the suppression of small-scale motion leads to the low pressure drop in a large radius ratio of the bend.     

Flow characteristics of tangential leakage in a scroll compressor for automobile heat pump with CO2

Tangential leakage loss reduction has great significance on improving the performance of scroll compressors. In this study, the flow field of a scroll compressor working with CO_2 was numerically investigated. The development characteristics of the tangential leakage flow in different working chambers were carried out, which was obtained by analyzing the field quantities distributions. The impacts of the radial clearances and sidewall roughness on the tangential leakage were also taken into consideration, in order to explore the feasible method of the flow control for the tangential leakage in scroll compressors. Results showed that the tangential leakage flow had various characteristics in the suction and compression chambers due to the different interactions between the tangential leakage flow and mainstream. Owing to little reverse pressure gradient, the tangential leakage flow maintained the typical jet form in the suction chambers. By contrast, the mixing of the tangential leakage flow and mainstream induced the passage vortex and secondary flows in the compression chamber. The secondary flow was the primary factor that results in the occurrence of localized high temperature region rather than the tangential leakage. With the increase of the radial clearance, the volumetric efficiency declined and the discharge temperature increased rapidly. In terms of flow control of the tangential leakage, the increase of sidewall roughness by 2 μm could achieve the same effect as the decrease of the radial clearance by 4 μm, while the volumetric efficiency increased by almost 5% and average discharge temperature decreased by 5K.     

基坑开挖反压土截面特性对基坑性状影响的有限元分析

根据反压土和支护结构的相互作用机理,采用有限元计算分析了反压土宽度、高度、坡度、放坡级数、面积等截面特征对支护结构位移和内力的影响规律。计算表明,随着反压土宽度、高度、坡度的增长,围护结构内力和位移也随之减小,但当这些截面特性发展到一定值时,其内力和位移减小趋势也逐渐趋于稳定。反压土面积是决定围护结构受力和位移的决定因素,当反压土面积相同时,开挖完成后的围护结构内力和位移基本相同,但随着工后时间的增长,宽高比决定围护结构位移和弯矩变化率的发展趋势。通过对具体的工程实例的分析结果表明,当反压土面积相同时,放坡级数不会影响反压土的受力和位移,合理的放坡级数应根据现场施工难易程度选择。