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相关概念视频

¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)01:20

¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)

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When proton-coupled carbon-13 spectra are simplified by a broadband proton decoupling technique, structural information about the coupled protons is lost. Distortionless enhancement by polarization transfer (DEPT) is a technique that provides information on the number of hydrogens attached to each carbon in a molecule. While the DEPT experiment utilizes complex pulse sequences, the pulse delay and flip angle are specifically manipulated. The resulting signals have different phases depending on...
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Discrete-Time Fourier Series01:20

Discrete-Time Fourier Series

241
The Discrete-Time Fourier Series (DTFS) is a fundamental concept in signal processing, serving as the discrete-time counterpart to the continuous-time Fourier series. It allows for the representation and analysis of discrete-time periodic signals in terms of their frequency components. Unlike its continuous counterpart, which utilizes integrals, the calculation of DTFS expansion coefficients involves summations due to the discrete nature of the signal.
For a discrete-time periodic signal x[n]...
241
Discrete Fourier Transform01:15

Discrete Fourier Transform

239
The Discrete Fourier Transform (DFT) is a fundamental tool in signal processing, extending the discrete-time Fourier transform by evaluating discrete signals at uniformly spaced frequency intervals. This transformation converts a finite sequence of time-domain samples into frequency components, each representing complex sinusoids ordered by frequency. The DFT translates these sequences into the frequency domain, effectively indicating the magnitude and phase of each frequency component present...
239
Properties of DTFT I01:24

Properties of DTFT I

383
In signal processing, Discrete-Time Fourier Transforms (DTFTs) play a critical role in analyzing discrete-time signals in the frequency domain. Various properties of the DTFTs such as linearity, time-shifting, frequency-shifting, time reversal, conjugation, and time scaling help understand and manipulate these signals for different applications.
The linearity property of DTFTs is fundamental. If two discrete-time signals are multiplied by constants a and b respectively, and then combined to...
383
Properties of DTFT II01:24

Properties of DTFT II

188
In the study of discrete-time signal processing, understanding the properties of the Discrete-Time Fourier Transform (DTFT) is crucial for analyzing and manipulating signals in the frequency domain. Several properties, including frequency differentiation, convolution, accumulation, and Parseval's relation, offer powerful tools for signal analysis.
The frequency differentiation property is illustrated by considering a DTFT pair and differentiating both sides with respect to ω.
188
¹H NMR: Interpreting Distorted and Overlapping Signals01:02

¹H NMR: Interpreting Distorted and Overlapping Signals

1.0K
Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are...
1.0K

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相关实验视频

Updated: Jun 17, 2025

In Situ Monitoring of Diffusion of Guest Molecules in Porous Media Using Electron Paramagnetic Resonance Imaging
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In Situ Monitoring of Diffusion of Guest Molecules in Porous Media Using Electron Paramagnetic Resonance Imaging

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通过密度校正的DFT纠正分散校正.

Minhyeok Lee1, Byeongjae Kim1, Mingyu Sim1

  • 1Department of Chemistry, Yonsei University, 50 Yonsei-ro Seodaemun-gu, Seoul 03722, Korea.

Journal of chemical theory and computation
|August 9, 2024
PubMed
概括
此摘要是机器生成的。

密度和分散校正的DFT (D2C-DFT) 通过排除密度敏感反应来改善分散校正. 这种双校准方法减少了密度函数理论计算中的错误和变化.

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Controlled Synthesis and Fluorescence Tracking of Highly Uniform PolyN-isopropylacrylamide Microgels
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科学领域:

  • 计算化学是一种计算化学.
  • 量子化学是一种量子化学.
  • 材料科学是一种材料科学.

背景情况:

  • 在DFT中分散校正的经验参数化经常混合功能和密度驱动的错误.
  • 现有的方法仅依赖于能量误差,限制了准确性.

研究的目的:

  • 引入一个双校准方法,密度和分散校正的DFT (D2C-DFT).
  • 通过计算密度移位错误来改善分散相互作用的参数化.

主要方法:

  • 从训练数据集中排除密度敏感反应.
  • 使用与Hartree-Fock密度相适应的分散校正.

主要成果:

  • 实现了错误和变异的显著减少.
  • 在几个半局部功能和全球混合体中表现出更好的性能.
  • 验证了D2C-DFT方法的有效性.

结论:

  • D2C-DFT为DFT中分散校正提供了一个更强大的方法.
  • 考虑到密度迁移错误,可以获得更准确,更可靠的结果.
  • 这种方法增强了DFT对各种化学系统的预测能力.