The scattering of light by particles is used to calculate the particle size distribution of the measured particles based on the distribution of scattered light energy. According to the actual working principle of various particle size measuring instruments, the "particle size" may be defined as follows: When the measured particle's physical properties or physical behavior is closest to a diameter of a homogeneous sphere (or a combination thereof), The diameter (or combination thereof) of the sphere is taken as the equivalent particle size (or particle size distribution) of the test particle.
The particle size measurement is essentially obtained by comparing the measured particle with a sphere made of the same material. Instruments with different principles choose different physical characteristics or physical behaviors as reference for comparison. For example, the sedimentation speed is selected by the sedimentation instrument, the scattered light energy distribution is selected by the laser particle size analyzer, and whether the particles can pass through the sieves, etc.
When comparing the physical properties or physical behavior of the test particle with that of a homogeneous sphere, sometimes one (or a group) of spheres with exactly the same characteristics (such as a Coulter counter) can be found. Only find the closest sphere. Since "the same" can be used as a special case of "similar" in theory, the word "near" is used in the definition to make the definition more general; some kind of physical property or physical behavior of the particle to be measured is to be made with a homogenous sphere. In comparison, it is sometimes possible to find a ball with a certain diameter corresponding to it, and sometimes it is necessary to use a combination of balls of different sizes to match each other.
One of the limiting factors of remotely controlled unmanned submersibles is that in order for their operators to see what their camera photographs, the vessel must be connected to the surface support vessel by a long tether. Scientists are trying to change this situation through a two-way system that uses lasers to wirelessly transmit ultra high-definition video underwater. The receiver in turn uses a 450 nm blue laser to form an uplink channel that passes data back to the underwater platform. Included in this data is feedback on the signal quality of the received video. Based on this feedback, the underwater platform will adjust the power and modulation of its video signal to compensate for the deficiencies caused by the clarity of the water. This means that if the water is quite clear, more video data packets can be transmitted at a faster rate, but if it is turbid, the video quality is maintained by slowing the video transmission rate.
The traditional cleaning industry has a variety of cleaning methods, mostly using chemical agents and mechanical methods for cleaning. Under the increasingly stringent environmental protection regulations in China, and people’s growing awareness of environmental protection and safety, the types of chemicals that can be used in industrial production and cleaning will become less and less. How to find a cleaner, non-invasive cleaning method is a problem we have to consider. Laser cleaning is characterized by non-abrasive, non-contact, non-thermal effects and objects suitable for various materials, and is considered to be the most reliable and most effective solution. At the same time, laser cleaning can solve problems that cannot be solved using traditional cleaning methods.
Laser cleaning technology is widely used in weapon maintenance. The use of laser cleaning system can remove rust and pollutants efficiently and quickly, and can select cleaning sites to achieve automatic cleaning. The use of laser cleaning not only has a higher degree of cleanliness than the chemical cleaning process, but also has little damage to the surface of the object. By setting different parameters, a dense oxide protective film or metal melting layer can also be formed on the surface of the metal object to improve surface strength and corrosion resistance. The laser-eliminated waste does not substantially pollute the environment and can also be operated remotely, effectively reducing health damage to operators.
The plasma is generated only when the energy density is above the threshold, which depends on the contaminant layer or oxide layer removed. This threshold effect is very important for the effective cleaning of the base material. There is a second threshold for the appearance of plasma. If the energy density exceeds this threshold, the base material will be destroyed. In order to ensure effective cleaning of the substrate material, the laser parameters must be adjusted according to the conditions so that the energy density of the light pulse is strictly between two thresholds.
Each laser pulse removes a certain thickness of the contamination layer. If the contamination layer is thick, multiple pulses are required for cleaning. The number of pulses needed to clean the surface depends on the degree of surface contamination. An important result produced by the two thresholds is the self-control of cleaning. Light pulses with an energy density above a first threshold will always remove contaminants until the substrate material is reached. However, because its energy density is lower than the damage threshold of the base material, the base is not damaged.