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相关概念视频

Adiabatic Processes for an Ideal Gas01:18

Adiabatic Processes for an Ideal Gas

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When an ideal gas is compressed adiabatically, that is, without adding heat, work is done on it, and its temperature increases. In an adiabatic expansion, the gas does work, and its temperature drops. Adiabatic compressions actually occur in the cylinders of a car, where the compressions of the gas-air mixture take place so quickly that there is no time for the mixture to exchange heat with its environment. Nevertheless, because work is done on the mixture during the compression, its...
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Pressure and Volume in an Adiabatic Process01:27

Pressure and Volume in an Adiabatic Process

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Free expansion of a gas is an adiabatic process. However, there are few differences between free expansion and adiabatic expansion. During free expansion, no work is done, and there is no change in internal energy. But, for an adiabatic expansion, work is done, and there is a change in internal energy. During an adiabatic process, the relation between the pressure and volume is obtained from the condition for the adiabatic process, that is, 
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Work Done in an Adiabatic Process01:20

Work Done in an Adiabatic Process

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Consider the adiabatic compression of an ideal gas in the cylinder of an automobile diesel engine. The gasoline vapor is injected into the cylinder of an automobile engine when the piston is in its expanded position. The temperature, pressure, and volume of the resulting gas-air mixture are 20 °C, 1.00 x 105 N/m2, and 240 cm3 , respectively. The mixture is then compressed adiabatically to a volume of 40 cm3. Note that, in the actual operation of an automobile engine, the compression is not...
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Bernoulli's Equation: Problem Solving01:16

Bernoulli's Equation: Problem Solving

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A Venturi meter is essential for measuring fluid flow rates in pipelines. It utilizes the relationship between fluid velocity and pressure described by Bernoulli's equation. When installed in a sewage system, the Venturi meter accurately determines the wastewater flow rate by measuring pressure differences.
The first step is to compute the cross-sectional areas of the pipe and the Venturi throat to analyze the pressure difference indicated by the pressure gauge. Next, the continuity...
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Atomic Nuclei: Types of Nuclear Relaxation01:28

Atomic Nuclei: Types of Nuclear Relaxation

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Nuclear relaxation restores the equilibrium population imbalance and can occur via spin–lattice or spin–spin mechanisms, which are first-order exponential decay processes.
In spin–lattice or longitudinal relaxation, the excited spins exchange energy with the surrounding lattice as they return to the lower energy level. Among several mechanisms that contribute to spin–lattice relaxation, magnetic dipolar interactions are significant. Here, the excited nucleus transfers...
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Frames: Problem Solving I01:24

Frames: Problem Solving I

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Consider a jib crane with an external load suspended from the pulley. The dimensions of the crane members are shown in the figure. A systematic analysis of the frame structure is required to determine the reaction forces at the pin joints, assuming that the pulleys are frictionless.
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相关实验视频

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Author Spotlight: Exploring Intrinsically Disordered Protein Dynamics Through NMR Relaxation Experiments
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完整的解决方案,用于旋转框架放松功能在adiabatic脉冲期间.

Shalom Michaeli1

  • 1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, USA.

Journal of magnetic resonance (San Diego, Calif. : 1997)
|December 7, 2024
PubMed
概括

这项研究引入了一种新的框架,即倾斜三次旋转框架 (TTRF),以准确地描述在亚波动射频脉冲期间的放松. 这解释了虚构的磁场,提高了高分辨率NMR实验的准确性.

科学领域:

  • * 磁共振光谱学 磁共振光谱学
  • * 量子控制和一致性

背景情况:

  • * 常规描述的亚底波射频 (RF) 脉冲使用倾斜双旋转框架 (TDRF) 或第二旋转框架 (SRF).
  • *当磁化与有效磁场完全对齐或在垂直平面上演变时,这些模型是充足的.
  • * 它们忽略了因有效磁场的时间演变而产生的虚构磁场,当不严格满足电条件时,这可能是显著的.

研究的目的:

  • * 开发一个一般的治疗放松功能在adiabatic射频脉冲期间,考虑到不可忽视的虚构磁场.
  • * 为了在倾斜三次旋转框架 (TTRF) 中获得放松函数的解决方案.
  • * 分析在高压分离 (HSn) 脉冲 (HS1和HS4) 期间的放松.

主要方法:

  • * 在倾斜三次旋转框架 (TTRF) 中导出放松函数解决方案.
  • * TTRF框架应用于高压分离 (HSn) 脉冲,特别是HS1和HS4.
  • *分析脉冲调节功能和参数对放松贡献的影响.

主要成果:

  • * 在HSn脉冲的TTRF中获得了放松函数的一般解决方案.
  • * 证明虚拟场对放松的贡献取决于脉冲调制和参数.
  • *为放松描述提供了纠正,以考虑虚构场.
关键词:
艾迪亚巴特脉冲的使用双极放松是一种双极放松.虚构的领域虚构的领域.旋转的框架 旋转的框架() 的意思是T (2ρ) 的意思是

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结论:

  • * TTRF提供了一个更准确的描述,在虚拟场是显著的时,在亚底波射频脉冲期间的放松.
  • * 导出的校正与特定的实验设置有关,特别是在高分辨率的NMR中.
  • * 这项工作在高级射频脉冲序列中提供了放松现象的概括治疗.