Precipitation of barium sulfate nanoparticles via impinging streams

The impinging streams technology (abbreviated as IS) has good micromixing in the precipitation processes. The experiments were loaded with two reactants, BaCl₂ and Na₂SO₄, to prepare BaSO₄ in the impinging streams reactor, comparing with those in the direct precipitation (DP) reactor. XRD and TEM were used to analyze the crystal type, the morphology and size of particles through the photographs. The results indicate the size of the particles from IS is about 30 nm and of narrower distribution and finer dispersibility than that from DP.     

The effect of the scale of horizontal subsurface flow constructed wetlands on flow and transport parameters.

Horizontal subsurface flow constructed wetlands have proven their efficiency in treating wastewater and removing the pollutants of concern. Treatment efficiency depends on the wastewater residence time, which is a function of the hydraulic loading and the physical conditions of the constructed filter system, which can be described with effective parameters such as: hydraulic conductivity, porosity, dispersivity etc. Because spatial variability is often scale dependent, these effective parameters may be affected by the scale of the system being studied. In this paper the results of tracer experiments in constructed filters using saturated horizontal flow at three scales (small and medium lab scales and full-scale system) using the same filter media is reported. Light-weight aggregate (filter media termed Filtralite-P) was used at all scales. Increasing the scale was associated with increasing dispersivity, meanwhile hydraulic conductivity experienced dramatic reduction and variation by increasing the examined scale. Observed changes in the hydraulic parameters indicate that heterogeneity at different scales should be taken into account when the performance of LWA filters are evaluated from small-scale experiments.     

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豫西地区中、下二叠统太原组、山西组、上石盒子组及下石盒子组煤成气资源丰富，但成煤环境纵向发育与横向变化较大，规律难于把握。因此，开展煤成气源岩沉积环境研究有利于该区煤成气资源的勘探与开发及合理的利用。通过露头、钻井、地震资料及分析、测试资料的综合研究认为：本区中、下二叠统主要沉积了一套浅海碳酸盐岩，海湾-泻湖、潮坪、沼泽、障壁岛(砂质滩、坝)及三角洲相陆源碎屑岩和煤层。从总的沉积特征来看，下二叠统太原组、山西组基本上发育滨、浅海相碳酸盐岩、陆源碎屑岩和煤的混合沉积。上二叠统上、下石盒子组则以海陆交互相陆源碎屑沉积为主，三角洲及三角洲平原沼泽十分发育；沉积环境具有自下而上，自南东向北西方向由海相逐步过渡为陆相的基本特点。其煤成气源岩沉积环境以早二叠世山西期潮坪、泻湖过渡带之滨岸沼泽环境为最佳，其次为中二叠世下石盒子期三角洲平原沉积之平原沼泽环境。     

文本索引词项相对权重计算方法与应用

文本索引词权重计算方法决定了文本分类的准确率。该文提出一种文本索引词项相对权重计算方法,即文本索引词项权重根据索引词项在该文本中的出现频率与在整个文本空间出现的平均频率之间的相对值进行计算。该方法能有效地提高索引词对文本内容识别的准确性。     

Solution-chemistry analysis of ammonium bicarbonate consumption in rare-earth-element precipitation

A solution-chemistry analysis is applied to estimating the consumption of ammonium bicarbonate in the recovery of rare-earth (RE) elements from leachates of weathered clays. The theoretical analysis shows that a two-step process is needed for recovering RE from the leachates of the weathered clays by precipitation using ammonium bicarbonate. The first step is a precipitation at solution pH 5 to remove impurities such as Fe and Al. The second step is to precipitate RE by adjusting the solution pH above 8. The consumption of ammonium bicarbonate was found to depend on the concentration of RE elements and impurities in the leachates. The total amount of ammonium bicarbonate consumption for the entire process was determined experimentally, and the results showed an excellent agreement with that calculated based on solution-chemistry analysis. The decomposition of H₂CO₃ was identified as one of the main causes of ammonium bicarbonate overdose, accounting for up to 41 pct in comparison to 20 pct consumption for the removal of impurities. The amount of ammonium bicarbonate required in terms of the NH₄HCO₃: RE₂O₃ (RE oxides) molar ratio was found to be 4:1 for maximal RE recovery. An overall RE recovery around 90 pct was achieved with a product purity being about 90 pct.     

Signals in science - On the importance of signaling in gaining attention in science

Which signals are important in gaining attention in science? For a group of 1,371 scientific articles published in 17 demography journals in the years 1990-1992 we track their influence and discern which signals are important in receiving citations. Three types of signals are examined: the author's reputation (as producer of the idea), the journal (as the broker of the idea), and the state of uncitedness (as an indication of the assessment by the scientific community of an idea). The empirical analysis points out that, first, the reputation of journals plays an overriding role in gaining attention in science. Second, in contrast to common wisdom, the state of uncitedness does not affect the future probability of being cited. And third, the reputation of a journal may help to get late recognition (so-called sleeping beauties) as well as generate 'flash-in-the-pans': immediately noted articles but apparently not very influential in the long run.     

OMA协议下的TS节目DRM解决方案

数字版权保护技术已经成为网络电视中除了视频编码技术以外的又一项核心技术。它用于保护内容所有人的版权,控制客户对于内容的使用。文章在阐述OMADRM标准的基础上,提出了一种适应国内广电系统实际播控环境的TS制式节目的DRM解决方案,并根据自行开发的演示系统,就其加密效率加以论证。     

基于LabWindows/CVI的多线程测控软件设计技术

多线程技术是W in32操作系统的一项重要软件技术。CVI 6.0及其以后版本提供了线程池和异步定时器两种多线程运行机制,为测控软件的设计开发带来了一次技术飞跃。文中结合测控软件设计实例,详细介绍了在CVI平台下多线程编程技术的应用方法。     

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川东北飞仙关组高含硫气藏气井在完井测试过程中，压力测点位置与产层中部的距离较大，需将压力数据用气柱压力计算公式折算后再进行试井分析解释。文章以质量、动量和能量三大守恒方程和状态方程为基础，考虑了流动气柱的动能损失以及井筒和地层中复杂的传热机理，推导出计算单相气流在井筒不同部位压力和温度的方法。以坡2井为例，应用目前最新的模块化动态地层测试器MDT地层测试技术，对折算的压力进行了验证和对比分析。结果表明，应用文中的压力计算方法，完全可以满足解释的压力数据精度。另外，在没有进行完井测试前利用MDT测压资料确定地层压力等储层参数是较为直接和可靠的方法。同时此法对川东北飞仙关组高含硫气藏的开发动态监测以控制元素硫在井底和井筒的沉积具有十分重要的指导意义。