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相关概念视频

Mixtures of Acids03:27

Mixtures of Acids

The pH of a solution containing an acid can be determined using its acid dissociation constant and its initial concentration. If a solution contains two different acids, then its pH can be determined using one of several methods depending upon the relative strength of the acids and their dissociation constants.
A Mixture of a Strong Acid and a Weak Acid
In a mixture of a strong acid and a weak acid, the strong acid dissociates completely and becomes a source of almost all the hydronium ions...
¹³C NMR: ¹H–¹³C Decoupling01:04

¹³C NMR: ¹H–¹³C Decoupling

The probability of having two carbon-13 atoms next to each other is negligible because of the low natural abundance of carbon-13. Consequently, peak splitting due to carbon-carbon spin-spin coupling is not observed in spectra. However, protons up to three sigma bonds away split the carbon signal according to the n+1 rule, resulting in complicated spectra.
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
Precipitation Processes01:12

Precipitation Processes

The experimental conditions in a gravimetric analysis should be optimized to maximize the particle size and purity of the obtained precipitate. Ideally, the concentration of the precipitating reagent should be low with effective stirring to maintain low relative supersaturation for the growth of large crystals. In homogeneous precipitation, the precipitant is slowly generated by a chemical reaction in the solution to avoid local reagent excesses. For example, urea decomposes gradually to...
Colloidal precipitates01:09

Colloidal precipitates

The high insolubility of some precipitates can result in an unfavorable relative supersaturation. This can lead to colloidal particles with a large surface-to-mass ratio, where adsorption is promoted. For instance, in the precipitation of silver chloride, silver ions are adsorbed on the surface of the colloidal particles, forming a primary layer. This layer attracts ions of opposite charge (such as nitrate ions), forming a diffuse secondary layer of adsorbed ions. This electric double layer...
Heterogeneous Catalysis01:22

Heterogeneous Catalysis

Heterogeneous catalysis involves a catalyst in a different phase from the reactants. It is a process where the catalyst and the reactants are in distinct phases, typically solid and gas or liquid.Most heterogeneous catalysts are metals, metal oxides, or acids. The list includes transition metals like iron (Fe), cobalt (Co), nickel (Ni), palladium (Pd), platinum (Pt), chromium (Cr), manganese (Mn), tungsten (W), silver (Ag), and copper (Cu). These metals possess partially vacant d orbitals that...
Superplasticizers01:30

Superplasticizers

Superplasticizers are advanced admixtures that enhance the workability of concrete by lowering the water content without compromising the strength of the material. These substances are highly effective water reducers, improving concrete flow, making it easier to work with, and enabling concrete to reach inaccessible areas or densely reinforced sections without mechanical vibration. The key components in superplasticizers are either sulfonated melamine or naphthalene formaldehyde condensates,...

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相关实验视频

Updated: Jun 19, 2026

Synthesis of Immunotargeted Magneto-plasmonic Nanoclusters
09:43

Synthesis of Immunotargeted Magneto-plasmonic Nanoclusters

Published on: August 22, 2014

使用聚合物添加剂在低雷诺斯数下进行高效混合.

A Groisman1, V Steinberg

  • 1Department of Physics of Complex Systems, The Weizmann Institute of Science, 76100 Rehovot, Israel.

Nature
|April 20, 2001
PubMed
概括

这项研究表明,将微量聚合物添加到粘性液体中,可以在非常低的雷诺兹数下有效地混合它们. 这一发现为各种应用中混合流体提供了一种新方法.

科学领域:

  • 流体力学 流体力学 流体力学
  • 类风病学 类风病学 类风病学
  • 聚合物物理 聚合物物理

背景情况:

  • 高效的液体混合对于工业和环境过程至关重要.
  • 在没有专门的设备的情况下,低雷诺兹数 (层层流) 的混合通常是低效的.
  • 混合的分析解决方案存在于特定的随机流动模式,如Batchelor模式.

研究的目的:

  • 实验性地研究在低雷诺兹数下高效混合粘性液体.
  • 探索高分子量聚合物在增强流体混合中的作用.
  • 为了验证Batchelor混合模式中的理论预测.

主要方法:

  • 使用简单的曲线通道流量设置.
  • 采用非常粘性液体,其中分子重量高的高分子聚合物的度最低 (0.001%).
  • 对流体混合和流动模式进行详细的实验观测.

主要成果:

  • 在非常低的雷诺兹数下证明了粘性液体的高效混合.
  • 观察到由聚合物添加引起的弹性不稳定性和不规则的流量.
  • 测量速度光谱与巴切洛尔政权预测一致.
  • 证实了关于度概率分布 (指数尾) 和衰变速率 (指数时刻,对数空间相关性) 的理论预测.

更多相关视频

Flash NanoPrecipitation for the Encapsulation of Hydrophobic and Hydrophilic Compounds in Polymeric Nanoparticles
10:12

Flash NanoPrecipitation for the Encapsulation of Hydrophobic and Hydrophilic Compounds in Polymeric Nanoparticles

Published on: January 7, 2019

Application of a Coupling Agent to Improve the Dielectric Properties of Polymer-Based Nanocomposites
06:34

Application of a Coupling Agent to Improve the Dielectric Properties of Polymer-Based Nanocomposites

Published on: September 19, 2020

相关实验视频

Last Updated: Jun 19, 2026

Synthesis of Immunotargeted Magneto-plasmonic Nanoclusters
09:43

Synthesis of Immunotargeted Magneto-plasmonic Nanoclusters

Published on: August 22, 2014

Flash NanoPrecipitation for the Encapsulation of Hydrophobic and Hydrophilic Compounds in Polymeric Nanoparticles
10:12

Flash NanoPrecipitation for the Encapsulation of Hydrophobic and Hydrophilic Compounds in Polymeric Nanoparticles

Published on: January 7, 2019

Application of a Coupling Agent to Improve the Dielectric Properties of Polymer-Based Nanocomposites
06:34

Application of a Coupling Agent to Improve the Dielectric Properties of Polymer-Based Nanocomposites

Published on: September 19, 2020

结论:

  • 高分子量聚合物可以诱导弹性不稳定性,促进在低雷诺兹数的简单流中高效混合.
  • 观察到的混合动力与Batchelor制度的理论模型保持一致.
  • 这提供了一种有效的低度方法,用于在特定场景中增强液体混合.