What does the concept of physical quantity refer to? Determination of a physical quantity. What is a verification scheme
A physical quantity is a concept of at least two sciences: physics and metrology. By definition, a physical quantity is a certain property of an object or process, common to a number of objects in terms of qualitative parameters, but differing, however, in quantitative terms (individual for each object). A classic example of illustrating this definition is the fact that, having their own mass and temperature, all bodies have individual numerical values of these parameters. Accordingly, the size of a physical quantity is considered to be its quantitative content, content, and in turn, the value of a physical quantity is a numerical estimate of its size. In this regard, there is the concept of a homogeneous physical quantity when it is the bearer of a similar property in qualitatively. Thus, obtaining information about the values of a physical quantity as a certain number of units accepted for it is the main task measurements. And, accordingly, a physical quantity, which by definition is assigned a conditional value, equal to one, is a unit of physical quantity. In general, all values of physical quantities are traditionally divided into: true and real. The first are values that ideally reflect in qualitative and quantitative terms the corresponding properties of the object, and the second are values found experimentally and so close to the truth that they can be accepted instead. However, the classification of physical quantities does not end there. There are a number of classifications created according to various criteria. The main ones are divided into:
Introduced general concepts quantities and units. The advantages of the International System of Units are mentioned, as well as references to the implementation of units for individual quantities in standards laboratories. Quantities and units of measurement of ionizing radiation are then discussed in detail, with particular emphasis on those developed for general use. References are made to quantities defined for use in radioactivity measurement, dosimetry and protection.
Basics: Quantity and Units of Measurement
It is important to distinguish quantity from unit. In everyday language, word count means quantity, but in the field of measurement it means to characterize physical phenomenon in terms suitable for numerical expression. A physical quantity is a phenomenon that can be expressed as the product of a number and a unit.
1) active and passive physical quantities - when divided in relation to measurement information signals. Moreover, the first (active) in this case are quantities that, without the use of auxiliary energy sources, have the probability of being converted into a measurement information signal. And the second (passive) are quantities for which it is necessary to use auxiliary energy sources that create a signal of measurement information;
What is a physical quantity? Classification of PVs according to their belonging to different groups of physical processes
The unit represents the selected quantity reference sample. The Secretary General of the conference and the measures established by the Meter Convention are responsible for the International System of Units. The International Commission on Radiological Protection recommends the use of protection level levels.
There are seven basic units: kilogram, meter, second, ampere, Kelvin, mole and candela. Combining basic units forms derived units. Derived units may have special names. However, some of the special names are limited to certain quantities, e.g. Hz is a unit of frequency, but Becquerel is a unit of activity.
2) additive (or extensive) and non-additive (or intensive) physical quantities - when dividing on the basis of additivity. It is believed that the first (additive) quantities are measured in parts; in addition, they can be accurately reproduced using a multivalued measure based on the summation of the sizes of individual measures. But the second (non-additive) quantities are not directly measured, since they are converted into a direct measurement of a quantity or a measurement by indirect measurements.
Arguments of differential relations are always non-stochastic quantities. The special name for the unit of activity is becquerel. The main activity step is the 4-beta-gamma match counter. For more information please refer to the links.
Half-life is the average time it takes for radionuclides to decay to half their original number. Figure 1: Illustration of fluence. The use of a sphere expresses the fact that the area perpendicular to the direction of each particle is being considered. Note. Energy is often expressed in units of electron volts.
In 1791 G. The French National Assembly adopted the first ever system of units of physical quantities. It was a metric system of measures. It included: units of length, area, volume, capacity and weight. And they were based on two now well-known units: the meter and the kilogram. A number of researchers believe that, strictly speaking, this first system is not a system of units in the modern sense. And only in 1832, the German mathematician K. Gauss developed and published the latest methodology for constructing a system of units, which in this context is a certain set of basic and derived units.
Energy density differential, Φ
The fluence differential in energy Φ or the energy distribution of fluence. Full description radiation field requires fluence distribution depending on: 1 type of particles, for example. electrons, photons, neutrons 2 spatial position, 3 directions, 4 energies and 5 times.
Velocity values, for example. fluence have their own symbols. The only scalar quantities described so far allow the definition and use of vector quantities, e.g. The medium must always be specified. For an overview of them, please refer to the links. Special name Kerma units - gray.
The scientist based his methodology on three main independent quantities: mass, length, time. And the mathematician took the milligram, millimeter and second as the main units of measurement for these quantities, since all other units of measurement can be easily calculated using the minimum ones. K. Gauss considered his system of units to be an absolute system. With the development of civilization and scientific and technological progress, a number of systems of units of physical quantities arose, the basis for which is the principle of the Gaussian system. All of these systems are constructed as metric systems, but they are distinguished by different base units. Thus, at the present stage of development, the following main systems of units of physical quantities are distinguished:
What is a standard unit of physical quantity? What types of standards do you know?
Kerma is usually expressed in terms of the energy distribution Ф of the fluence of an uncharged particle. The energy transferred is the energy lost minus the energy leaving the mass and minus the energy released by nuclear transformations. The special name for the unit of absorbed dose is grey.
When charged particles are in equilibrium
For an overview of calorimeters, please refer to the links. Figure 4: Stochastic and stochastic quantities. As the sample's overall mass decreases, the energy per unit mass will become more random. Where is the tabulated mass stopping power of the material. A weighting factor is introduced to weigh the absorbed dose for the biological effectiveness of the particles. The special name for the equivalent dose unit is sievert.
1) GHS system(1881) or the CGS System of Units of Physical Quantities, the basic units of which are the following: centimeter (cm) - represented as a unit of length, gram (g) - as a unit of mass, and second (s) - as a unit of time ;
2) MKGSS system(end of the 19th century), initially using the kilogram as a unit of weight, and subsequently as a unit of force, which led to the creation of a system of units of physical quantities, the main units of which were three physical units s: meter as a unit of length, kilogram-force as a unit of force and second as a unit of time;
Protection: operational values
The technical name for the unit of effective dose equivalent is the sievert. For measurement purposes, operational quantities are defined: dose equivalent, targeted dose equivalent and individual dose equivalent. Where doses are estimated from area monitoring, the relevant operational quantities are equivalent dose equivalent and directed dose equivalent.
Analogue of the directed dose, N'
The directional dose analogue is particularly useful when estimating dose to the skin or ocular lens. Unit conversion: short drive. Let's assume that you travel 0 km from your university to your home in 0 minutes. Calculate the average speed in kilometers per hour and meters per second.
3) MKSA system(1901), the foundations of which were created by the Italian scientist G. Giorgi, who proposed the meter, kilogram, second and ampere as units of the MCSA system.
Today in world science there are an innumerable number of various systems of units of physical quantities, as well as many so-called non-systemic units. This, of course, leads to certain inconveniences in calculations, forcing one to resort to recalculation when converting physical quantities from one system of units to another. A situation has arisen in which there is a serious need to unify units of measurement. It was necessary to create a system of units of physical quantities that would be suitable for most different branches of the measurement field. Moreover, the main emphasis should have been the principle of coherence, implying that the unit of the proportionality coefficient is equal in the equations of the relationship between physical quantities. A similar project was created in 1954 by a commission to develop a unified International System of Units. It was called the "Draft International System of Units" and was eventually approved by the General Conference on Weights and Measures. Thus, the system based on seven basic units came to be called the International System of Units, or SI for short, which comes from the French abbreviation “Systeme International” (SI). International system units, or SI for short, contains seven basic, two additional, as well as several non-systemic, logarithmic units of measurement, which can be seen in Table 1.
We first calculate the average speed using the given units. We can then get the average speed into the desired units by choosing the correct conversion factor and multiplying by it. The correct conversion factor is the one that cancels the unwanted unit and leaves the desired unit in its place.
Average speed is the distance traveled during the trip. In equation form. Replace the specified distance and time values. To check your answer, consider the following. Make sure you've cleared the units correctly in the module. If you wrote the unit block factor upside down, the units will not cancel properly in the equation. If you accidentally flip the odds up, the units will not be reversed; rather, they will give you the wrong units as follows.
A system of physical quantities is a set of interrelated physical quantities, formed in accordance with selected principles, when some quantities are taken as independent (basic), while others are functions (derivatives) of independent quantities.
Basic physical quantities do not depend either on each other or on other quantities of this system.
Make sure that the units of the final answer are the desired units. Check for significant figures. Since each of the values given in the problem has three significant figures, the answer must also contain three significant figures. Note that the significant numbers in the conversion factor are not relevant because an hour is defined as 60 minutes, so the accuracy of the conversion factor is perfect.
Then check if your answer is correct. Let's look at some information from the problem - if you travel 10 km in a third of an hour, you will be traveling three times in an hour. The answer seems reasonable. There are several ways to convert average speed to meters per second.
Independent quantities that do not have governing equations are called “fundamental physical quantities.” (As an example of basic physical quantities, let us name quantities such as distance and time.) And quantities that are determined using governing equations are called “derived physical quantities.”
specific value is a value divided by mass (for example, specific volume);
Two conversion factors are needed - one to convert hours to seconds and another to convert kilometers to meters. By multiplying these harvests. You may have noticed that the answers in the processed example we just looked at were in three digits. When do you need to worry about the number of digits in what you're calculating? Why not write down all the numbers your calculator produces? The module's accuracy, precision, and meaningful numbers will help you answer these questions.
Significant advances in radiation therapy over the past century have been driven in large part by our ability to more effectively focus and deliver radiation to tumor volumes. Physical discoveries and technological inventions were an important driving force behind this progress. However, there is still plenty of room for future improvements from physics, such as image control and 4D motion control and particle therapy, as well as improved efficiency from smaller, cheaper technologies.
A molar quantity is a quantity divided by the amount of a substance (for example, molar volume).
4. What is a physical quantity? Classification of fw by types of phenomena.
According to the types of phenomena, physical quantities are divided into the following groups:
Material, that is, describing the physical and physico-chemical properties of substances, materials and products made from them. This group includes mass, density, electrical resistance, capacitance, inductance, etc. Sometimes these physical quantities are called passive. To measure them, it is necessary to use an auxiliary energy source, with the help of which a measurement information signal is generated. In this case, passive physical quantities are converted into active ones, which are measured;
What is measurement?
Great challenges lie ahead for radiation therapy physicists beyond dose localization, such as in the identification of biological targets, improved modeling of normal tissues and tumors, improved multi-objective and robust optimization, and the continued adoption of advanced technologies such as molecular imaging. The success of physics in radiation therapy was based on continuing to fuel the field with new discoveries and inventions from physics research. The key to success was the application of a rigorous scientific method.
Energy, that is, quantities that describe the energy characteristics of the processes of transformation, transmission and use of energy. These include current, voltage, power, energy. These quantities are called active. They can be converted into signals.
5. What is a physical quantity? Classification of PVs according to their belonging to different groups of physical processes.
Physical quantity is a physical property of a material object, physical phenomenon, process that can be characterized quantitatively.
Despite the importance of physics research for radiotherapy, too few physicists are currently involved in cutting-edge research. Increasing emphasis on more “professionalism” in medical physics further balances the situation. To prevent this from happening, we argue that medical physics needs more research positions as well as better academic programs. Only with greater emphasis on medical physics research will the future of radiation therapy and other physics-related medical specialties look as bright as the past, and medical physics will retain its status as one of the most exciting areas of applied physics.
According to affiliation various groups physical processes, physical quantities are divided into spatiotemporal, mechanical, thermal, electrical and magnetic, acoustic, light, physicochemical, ionizing
radiation, atomic and nuclear physics.
6. What is a standard unit of physical quantity? What types of standards do you know?
A standard of a unit of physical quantity is a measuring instrument (or a set of measuring instruments) intended for reproducing and (or) storing a unit and transferring its size to subordinate measuring instruments in the verification scheme and approved as a standard in the prescribed manner.
Radiation therapy would not exist without physics. This obvious but sometimes forgotten fact is the guiding principle of this review article. Although radiation therapy lives at the interface between many disciplines, its dependence on physics is perhaps its strongest. By this we mean not only dependence on clinical physics support to ensure safe and accurate radiation delivery, but primarily dependence on the research side of physics in general and medical physics in particular.
We tend to think of medical physics as the physics of medicine to emphasize the importance of physics. One question we will try to answer is what is the recipe for success of physics in medicine? In Part 1, we will first define the traditional contributions of physics to radiation therapy, largely focused on the physics of precise radiation “dose localization.” In this article, we define dose localization as the ability to deliver a dose precisely and precisely to the area of interest. This of course includes not only advances in delivery technology, but also treatment planning, especially in the area of imaging.
Primary standard is a standard that reproduces a unit of physical quantity with the highest accuracy possible in a given field of measurement at the current level of scientific and technical achievements. The primary standard can be national (state) and international.
Secondary standard - a standard that receives the size of a unit directly from the primary standard of a given unit.
We will then look at the contributions of physics beyond dose localization and even beyond radiation therapy. In part two, we will discuss the role of physicists in radiotherapy and the challenges we currently face, especially in focusing special attention the role of research. Finally, we will present some suggestions on how to address these issues in the future to provide a sustainable environment for long-term, high-impact physics in medicine.
Part 1: Dose Localization and Beyond
The history of physics in radiation therapy begins with the discovery x-rays Wilhelm Conrad Roentgen. Of the many “gifts” that physics has made to medicine, the discovery of X-rays is probably the greatest. The enormous potential of X-rays not only for diagnosis, but also for the treatment of diseases was recognized soon after its discovery. The first treatment of patients using X-rays occurred 1 year after discovery. Thus, physical discovery launched the field of radiation therapy.
Standard of comparison - a standard used for comparisons of standards that, for one reason or another, cannot be directly compared with each other.
Original standard - a standard that has the highest metrological properties (in a given laboratory, organization, enterprise), from which the unit size is transmitted to subordinate standards and available measuring instruments.
Working standard - a standard designed to convey the size of a unit to working measuring instruments.
State primary standard - the primary standard, recognized by the decision of the authorized state body as the initial standard on the territory of the state.
National standard - a standard recognized by an official decision to serve as a reference for a country.
International standard - a standard adopted by international agreement as an international basis for harmonizing with it the sizes of units reproduced and stored by national standards.