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Power box (English name: power box), also known as top-mounted power box or rack power box, is an electrical energy control device that provides operating power for vacuum circuit breakers and other high-voltage switches. The input voltage ranges from 220V to 380V, and some scenarios support 660V and 1140V input. It is mainly used in communication cabinets, construction sites, and mining applications, etc. [4-6]. Its core functions include power access distribution, circuit status monitoring, load protection, and adjustable output of DC voltage in multiple levels. It achieves single opening and single closing operations through thyristor voltage regulation and rectification technology, and integrates switchgear, measuring instruments, and protection devices in a metal enclosed structure. The protection level is adjusted according to the usage scenarios [1-2] [10].
This equipment type includes fixed panel type, protective type, drawer type, and power and lighting control box. The drawer-type switch cabinet is suitable for high-reliability power distribution scenarios due to its modular design [2-3]. The intelligent power box launched in October 2022 uses military-grade materials to reduce the weight of the box by 62%, integrates temperature sensing alarm, smoke alarm, and positioning functions, supports remote management, and enables status monitoring through a WeChat mini-program [5]. Some models comply with the ORV3 HPR standard and support power supply for the entire cabinet and multi-level power management. The system peak efficiency is greater than 97.5% [8-9]. Safety regulations require that combustible materials are prohibited within 1.2 meters of the power box and that insulation protection equipment and fire extinguishing devices be configured [7] [10].

In the field of computers, a buffer refers to a buffer register, which comes in two types: input buffer and output buffer. The former is used to temporarily store the data sent by the peripheral device so that the processor can retrieve it; the latter is used to temporarily store the data sent by the processor to the peripheral device. With the use of numerical control buffers, it is possible to coordinate and buffer the high-speed operation of the CPU with the slow operation of the peripheral device, achieving synchronous data transmission. Since the buffer is connected to the data bus, it must have a tri-state output function.
In other fields, there are also elevator buffers and car spring buffers, whose purpose is to slow down the speed, improve safety and comfort.

A device for restoring the original modulated signal from the oscillations or waves generated by modulation. Application field: Communication Science (first-level discipline); Communication Principles and Basic Technologies (second-level discipline).
A demodulator is a device that, through digital signal processing technology, restores the low-frequency digital signal modulated in a high-frequency digital signal. Demodulators are widely used in the transmission and restoration of information such as broadcasting (audio signals) and television (video signals). Demodulators are generally used in pairs with modulators. The modulator is used to process digital signals into high-frequency signals for transmission, while the demodulator restores the digital signals to the original signals.

In a data communication network, the telecommunication facilities that connect two or more data stations according to the technical requirements of a certain link protocol are called data links, or simply data links. Besides the physical lines, a data link must also have communication protocols to control the transmission of these data. If the hardware and software that implement these protocols are added to the link, it constitutes a data link.

Logical Link Control (LLC) is the upper part of the data link layer in a local area network. The LLC protocol is defined in IEEE 802.2. The data link services of users provide a unified interface for the network layer through the LLC sub-layer. Below the LLC sub-layer is the MAC (Media Access Control sub-layer). In the IEEE standard, this sub-layer was added. This sub-layer ensures transmission across different network types by adding an 8-bit destination address and an 8-bit source address to the IP packet to serve as access points for the destination and source. Additionally, there is an 8-bit or 16-bit control field used for auxiliary functions such as flow control.

The data link layer is the second layer in the OSI reference model, located between the physical layer and the network layer. It is responsible for establishing, maintaining, and releasing data link connections between network nodes, and achieves reliable data transmission between adjacent nodes through frame transmission. Its core functions include framing (using byte counting method, character padding, bit padding, and illegal encoding method to achieve frame delimitation) [2] [6], error control (CRC verification) [1] [4], flow control (sliding window protocol) [4] [6], and link management [5].
The protocol system of this layer is divided into two sub-layers: Logical Link Control (LLC) and Media Access Control (MAC) [1] [5]. The former uses the stop-and-wait ARQ protocol to achieve error control [1], while the latter solves the problem of channel competition and performs MAC addressing [5-6]. The main protocols include High-Level Data Link Control Protocol (HDLC) and Point-to-Point Protocol (PPP). Among them, the HDLC frame structure consists of a flag field, an address field, a control field, an information field, and a check field, supporting three operation modes: normal response, asynchronous response, and asynchronous balance [2-4]. The Ethernet protocol uses the CSMA/CD mechanism to achieve media access control, and addresses physical devices through MAC addresses [5-6].
The data link layer realizes the encapsulation and decapsulation of network layer data through transparent transmission technology, and the frame check sequence field can verify the integrity of the frame content [2] [4]. The MAC layer subsystem includes time slot processing and time synchronization modules, ensuring the effective allocation of channel resources [3].

The Ethernet controller, also known as the Ethernet adapter, is what we commonly refer to as the “network card”. Its installation method is to insert it into the PCI expansion slot on the motherboard of the machine. It is usually white, and then by installing the driver disc included in the purchased network card, it can be installed. The Ethernet controller uses a specific physical layer and data link layer standard, such as Ethernet or Token Ring, to implement the circuit system required for communication. This provides a foundation for a complete network protocol stack, enabling small computer groups in the same local area network and wide area networks connected through routing protocols, such as IP, to communicate. An Ethernet controller usually comes with a twisted pair cable, optical fiber, BNC, AUI, and HomePNA interface. Among them, the latter three are less common nowadays, and optical fiber is mostly used for servers.

The discrete input module typically has high electrical isolation performance, such as being able to achieve an electrical isolation of up to 2500V, effectively preventing external electrical interference from affecting the internal circuits of the system and ensuring the stability of signal transmission.
This module can support various input signal types, such as switch signals and TTL level signals, and is applicable over a wide range, meeting the needs of different industrial scenarios. The discrete input module has a fast response time and can respond to input signals within 10ms, ensuring that the system can promptly capture changes in external signals. Its input channel count usually has different specifications such as 8 channels or 16 channels, and users can flexibly choose the appropriate channel count based on the number of signals in the actual application scenario. The discrete input module has strong anti-interference capabilities, by adopting filtering circuits and shielding measures, it can effectively suppress industrial frequency interference of 50Hz and above.
The working temperature range of the module is typically between -20°C and 70°C, capable of adapting to the temperature variations in harsh industrial environments, ensuring the reliability of the operation. From the perspective of power consumption, the discrete input module has low power consumption, with the typical power consumption of a single channel possibly as low as a few milliwatts, which helps to reduce the energy consumption of the entire system. The input interface of this module mostly adopts optocouplers, this isolation method can achieve signal transmission while electrically isolating the input circuit from the internal circuit, enhancing safety. The discrete input module supports communication with various control systems, for example, it can be seamlessly connected with PLC control systems to achieve rapid data interaction.

I. Basic Working Principle of Gas Turbines
A gas turbine is an efficient and clean energy conversion device. Its core working principle is to utilize the energy released during continuous combustion to drive the turbine to rotate, thereby generating mechanical energy. This process involves the coordinated action of multiple key components, including compressors, combustion chambers, and turbines, etc. Through the ingenious combination and efficient operation of these components, the gas turbine can achieve efficient conversion and utilization of energy.
◇ Inhaling and Compressing
During the operation of a gas turbine, air is first drawn in from the outside through the intake duct. This air then enters the compressor, which is composed of multiple stages of blades. As the air flows through the compressor, each stage of the blades exerts a force on the air, causing its pressure and temperature to gradually increase. For example, in an aviation gas turbine, the compressor can increase the air pressure to several dozen atmospheres. Although this process is similar to the compression stroke in a piston engine, it is continuous and highly efficient.
◇ Combustion
The high-temperature and high-pressure air that has been continuously pressurized by the compressor will then enter the combustion chamber. Here, fuels such as natural gas and aviation kerosene will be injected and mixed thoroughly with the air. Once ignited, this process will release a tremendous amount of heat energy, causing the gas temperature in the combustion chamber to rise rapidly. Typically, the gas temperature at the outlet of the combustion chamber can reach 1000 to 1500 degrees Celsius. This high-temperature gas is the core energy source that enables the gas turbine to generate power.
◇ Expansion Work
The hot and high-pressure gas flowing out of the combustion chamber will then enter the turbine section. The turbine is also composed of multiple stages of blades. The high-temperature gas undergoes expansion in the turbine, thereby driving the rotation of the turbine blades. Since the turbine is closely connected to the compressor and external loads (such as generators, aircraft propellers, etc.), the rotational motion of the turbine not only keeps the compressor working continuously but also outputs mechanical work externally. For example, in a gas turbine used for power generation, the rotation of the turbine drives the generator to produce electricity; while in an aircraft gas turbine, the turbine directly drives the aircraft’s propeller to rotate or generates jet propulsion force.
◇ Exhaust
After undergoing expansion work in the turbine, the gas still retains considerable energy despite a decrease in temperature and pressure. This gas is then discharged from the exhaust duct and expelled from the gas turbine. In some combined cycle systems of gas turbines, these discharged gases are ingeniously utilized, for instance, to heat steam, which in turn drives the steam turbine for further work, thereby enhancing the overall power generation efficiency of the system.
II. Key Components of Gas Turbines and Their Working Principles
The gas turbine is mainly composed of key components such as the compressor, combustion chamber and turbine. Its working principle is as follows: The compressor compresses the air and then sends it to the combustion chamber, where it mixes with fuel and burns, generating high-temperature and high-pressure gas that drives the turbine to rotate and do work, thereby driving the generator to generate electricity. During this process, the exhaust gas still has a relatively high energy level and can be further utilized for heating steam or other applications, thereby improving the overall power generation efficiency of the system.
◇ Compressor
The compressor is one of the core components of a gas turbine. Its working principle mainly relies on the compression effect of the blades on the airflow. The blades of the compressor have two basic types: axial type and centrifugal type. In an axial compressor, the blades are arranged along the axial direction, and the air flows axially. Through the continuous compression of multiple stages of blades, the pressure gradually increases. While in a centrifugal compressor, the air is spun towards the edge of the impeller by the rotation of the impeller, thereby achieving the pressure increase of the air. Modern large gas turbines usually adopt multi-stage axial compressors to achieve a higher compression ratio.
The performance of the compressor is of vital importance to the overall efficiency of the gas turbine. The higher the compression ratio, the greater the pressure of the air entering the combustion chamber, which enables more energy to be generated when burning the same amount of fuel. However, an excessively high compression ratio may also cause some problems, such as compressor surge, which is caused by the unstable flow of the airflow within the compressor. To avoid this phenomenon, a complex control system is required for monitoring and regulation.
◇ Combustion Chamber
The core function of the combustion chamber is to facilitate the stable and efficient combustion of fuel. Its internal structure needs to be meticulously designed to ensure that fuel and air can fully mix and burn completely. The forms of combustion chambers vary, including ring-tube combustion chambers and annular combustion chambers. During this process, fuel is precisely sprayed in through the fuel injector, and the key to its design lies in ensuring a good atomization effect, thereby promoting the uniform mixture of fuel and air.
In addition, the combustion chamber also faces several challenges, such as maintaining combustion stability, controlling the speed of flame propagation, and managing the combustion temperature. To prevent high temperatures from damaging turbine blades and ensure the stability of the combustion process, advanced technologies such as film cooling and convective cooling are employed in the combustion chamber. In the context of increasing environmental awareness, when designing, it is also necessary to fully consider how to reduce pollutant emissions (such as nitrogen oxides).
◇ Turbine
The core working principle of a turbine is that the expansion of high-temperature gas drives its blades to rotate. To enhance the efficiency of the gas doing work on the blades, the shape and design of the turbine blades have been meticulously optimized. Since the turbine blades need to withstand the scouring of high-temperature gas and significant mechanical stress, they are usually manufactured using materials that are resistant to high temperatures.
The efficiency of the turbine is influenced by various factors, including the aerodynamic performance of the blades and the number of turbine stages. Multi-stage turbines can more effectively utilize the gas energy, but they also increase the structural complexity and manufacturing cost. During the operation of the gas turbine, there is a power matching relationship between the turbine and the compressor. The control system needs to ensure the coordinated operation of the two to maintain the stable operation of the gas turbine.

The turbojet engine is a type of turbine engine. Its characteristic is that it completely relies on the gas flow to generate thrust. It is usually used as the power source for high-speed aircraft, but its fuel consumption is higher than that of the turbofan engine. Turbojet engines are divided into centrifugal and axial-flow types. The centrifugal type was invented by Sir Frank Whittle, an Englishman, in 1930. However, it was not until 1941 that aircraft equipped with this engine made its first flight, and it did not participate in World War II. The axial-flow type originated in Germany and was used as the power source for the first practical jet fighter, Me-262, in the summer of 1944 on the battlefield. Compared to the centrifugal turbojet engine, the axial-flow type has the advantages of a smaller cross-section and a higher compression ratio. Most of the current turbojet engines are of the axial-flow type.