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In many cases, the manipulated variable output by the PID controller is a dimensionless fraction between 0 and 100% of some maximum possible value, and the translation into real units (such as pumping rate or watts of heater power) is outside the PID controller. The process variable, however, is in dimensioned units such as temperature.
In some APIs, PID 0 is also used as a special value that always refers to the calling thread, process, or process group. [3] [4] Process ID 1 is usually the init process primarily responsible for starting and shutting down the system. Originally, process ID 1 was not specifically reserved for init by any technical measures: it simply had this ...
Each of the programs listed in PAT has an associated value of PID for its PMT. The value 0x0000 for program_number is reserved to specify the PID where to look for network information table. If such a program is not present in PAT the default PID value (0x0010) shall be used for NIT. TS packets containing PAT information always have PID 0x0000.
Its name comes from the information path in the system: process inputs (e.g., voltage applied to an electric motor) have an effect on the process outputs (e.g., speed or torque of the motor), which is measured with sensors and processed by the controller; the result (the control signal) is "fed back" as input to the process, closing the loop. [4]
P&IDs are originally drawn up at the design stage from a combination of process flow sheet data, the mechanical process equipment design, and the instrumentation engineering design. During the design stage, the diagram also provides the basis for the development of system control schemes, allowing for further safety and operational ...
A process control block (PCB), also sometimes called a process descriptor, is a data structure used by a computer operating system to store all the information about a process. When a process is created (initialized or installed), the operating system creates a corresponding process control block, which specifies and tracks the process state (i ...
Instead, the system simply redefines the "parent PID" field in the child process's data to be the process that is the "ancestor" of every other process in the system, whose PID generally has the value of 1 (one), and whose name is traditionally "init" (except in the Linux kernel 3.4 and above [more info below]).
In particular, the integers are a PID, so one can always calculate the Smith normal form of an integer matrix. The Smith normal form is very useful for working with finitely generated modules over a PID, and in particular for deducing the structure of a quotient of a free module. It is named after the Irish mathematician Henry John Stephen Smith.