艺术留学热门专业推荐
近年来，随着设计、艺术行业的发展，人们的审美和艺术需求日益增加，艺术设计领域已经摆脱了小众的标签，越来越多人进入这个专业领域，除了对艺术始终保持兴趣的艺术生，很多在综合类学校的非艺术生也中途选择了...
CIE A Level Physics复习笔记24.2.2 Annihilation in PET Scanning
The Process of Annihilation When a positron is emitted from a tracer in the body, it travels less than a millimetre before it collides with an electron The positron and the electron will annihilate...
CIE A Level Physics复习笔记24.2.1 Radioactive Tracers
Radioactive Tracers A radioactive tracer is defined as: A radioactive substance that can be absorbed by tissue in order to study the structure and function of organs in the body Radioactive isotope...
CIE A Level Physics复习笔记24.1.8 Computed Tomography Scanning
Computed Tomography Scanning A simple X-ray image can provide useful, but limited, information about internal structures in a 2D image When a more comprehensive image is needed, a computerised axia...
CIE A Level Physics复习笔记24.1.7 Attenuation of X-rays in Matter
Attenuation of X-rays in Matter Bones absorb X-ray radiation This is why they appear white on the X-ray photograph When the collimated beam of X-rays passes through the patient’s body, they are abs...
CIE A Level Physics复习笔记24.1.6 Production & Use of X-rays
Production of X-rays X-rays are short wavelength, high-frequency part of the electromagnetic spectrum They have wavelengths in the range 10−8 to 10−13 m X-rays are produced when fast-moving electro...
CIE A Level Physics复习笔记24.1.5 Attenuation of Ultrasound in Matter
Attenuation of Ultrasound in Matter Attenuation of ultrasound is defined as: The reduction of energy due to the absorption of ultrasound as it travels through a material The attenuation coefficient...
CIE A Level Physics复习笔记24.1.4 Intensity Reflection Coefficient
Intensity Reflection Coefficient The intensity reflection coefficient α is defined as: The ratio of the intensity of the reflected wave relative to the incident (transmitted) wave This can be calcu...
CIE A Level Physics复习笔记24.1.3 Specific Acoustic Impedance
Specific Acoustic Impedance The acoustic impedance, Z, of a medium is defined as: The product of the speed of the ultrasound in the medium and the density of the medium This quantity describes how ...
CIE A Level Physics复习笔记24.1.2 Generating & Using Ultrasound
Generating Ultrasound An ultrasound is defined as: A high frequency sound above the range of human hearing This is above 20 kHz, although in medical applications the frequencies can be up to the MH...
CIE A Level Physics复习笔记24.1.1 The Piezoelectric Transducer
The Piezoelectric Transducer The piezoelectric effect is defined as: The ability of particular materials to generate a potential difference (p.d.) by transferring mechanical energy to electrical en...
CIE A Level Physics复习笔记23.2.3 Half-Life
Half-Life Definition Half life is defined as: The time taken for the initial number of nuclei to reduce by half This means when a time equal to the half-life has passed, the activity of the sample ...
