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    What is network diagnostics?

    Network Diagnostics As part of its system functionality, the Network Manager collects WirelessHART network performance and diagnostic information.
    During network operation, the acquired information makes it possible to observe and analyze WirelessHART network behavior.
    If a problem is found, reconfiguration of the WirelessHART network will be performed while the network is running. Diagnostic information for WirelessHART networks can be obtained through HART commands.

    Which logical value states are frequently used by Verilog HDL to represent the value of the logic signal on the electrical connection line?

    1. 0: indicates low level, logic 0 or logic “not”;
    2. 1: indicates high level, logic 1 or logic “true”;
    3. X or X: indeterminate or unknown logic state ;
    4. Z or z: high impedance state; X and Z above are not case sensitive.

    What are the main features of modern electronic system design methods?

    1. Using FPGA/CPLD, the circuit design is more reasonable, open and standardized;
    2. Early simulation of system design is adopted;
    3. The main design files are source programs written in hardware description language HDL (Hardware Description Language).

    What are the characteristics of the TTP/C protocol?

    1. The information transmission delay is small, and the time jitter (the uncertainty of time) is small.
    2. The application system is less affected by the network structure, the software system can be developed independently, and then integrated with the hardware in the final stage. The application system has good portability and convenient performance testing.
    3. In a cluster using the same bus, all fault-free nodes can obtain mutual consistency information and time information.
    4. The distributed fault-tolerant synchronization algorithm is used to provide clock synchronization services without adding additional data transmission.
    5. In order to realize the fault-tolerant function, it has a distributed network management redundancy mechanism to support the redundancy of information channels and control modules.
    6. The protocol has greater flexibility, and can ensure high data transmission rate in the case of using twisted pairs and optical fibers.
    7. Use TDMA (Time Division Multiple Access) bus access mechanism.
    8. The time characteristics of the system can be known in advance in the design.
    9. The time characteristics of the system can be known in advance in the design.
    10. Support multiple working modes.
    11. Since bit arbitration is not required, the network transmission medium used has no special electrical restrictions.
    12. There is less control data in the information format, and the data transmission efficiency is high.

    At present, what are the positioning technologies developed by some research institutions?

    1. Using interesting environmental characteristics to achieve node localization. This technique uses information such as temperature, humidity, ambient noise, spectral energy, received signal strength, etc. to identify the location of nodes (Chen et al., 2007).
    2. Make full use of connectivity information. Because connectivity includes two cases: connected (positive) and non-connected (negative), it can divide space into two parts. Using these constraints, the region where the node is located can be determined (Guha et al., 2005).
    3. The positioning of the mobile node. There are several modes of movement, we can use the sequential Monte Carlo (se. quential Monte Cado) positioning method. The mobility of nodes to be located can improve the accuracy of positioning and reduce the cost of positioning (Hu et al., 2004).
    4. An iterative method used to minimize the location of the least squared difference. Iterative algorithms are more popular in localization. Because some statistical models do not have analytical results, an iterative procedure is the only way to solve these models. However, iterative algorithms are more complex than linear programming algorithms. Therefore, iterative algorithms may not be suitable for sensors with limited capabilities (uu et al., 2006).
    5. An iterative algorithm is used to realize the network deployment of nodes. Because such a problem is NP. For hard problems, we can use approximate methods: weak deployment and strong deployment. Both deployments provide upper and lower bounds on node localization uncertainty (Basu et al., 2006).
    6. Use the mobile node as a beacon node. The receiver does not need to be time-synchronized with the sender (beacon node). Nodes can be accurately located by using TDOA technology (Lu0 et al., 2006).
    7. Use the early position information of a set of sensors and a statistical model to estimate the position of the node. Sometimes, the location of the sensor can be obtained before its placement. However, a sensor may not be deployed at the expected location, but it can contact its neighbor nodes and estimate its own location in a probabilistic way (Fan9 et al., 2005).

    Embedded system hardware initialization is divided into several links?What is it?

    The system initialization process can be divided into 3 main links, in order from bottom to top, from hardware to software: chip-level initialization, board-level initialization and system-level initialization.

    What is the threshold shift phenomenon caused by Joule heat?

    When the current passing through the conductive filament is large and the generated Joule heat is too much, the conductive filament may spontaneously fuse, and the device exhibits a monostable threshold transition phenomenon. In the Pt/NiO/Pt device, Chang et al. found that by adjusting the ambient temperature, the resistance transition behavior of the device can be transformed between bistable resistance transition and monostable threshold transition. When the ambient temperature is 118K, the Pt/NiO/Pt device has stable unipolar transition characteristics after forming (10mA current limiting). When the ambient temperature was raised to 300K, the device exhibited a monostable threshold transition characteristic. When the ambient temperature was lowered to 80K, the device returned to stable unipolar transition characteristics. When the ambient temperature rises to 300K again, the device changes from the bistable unipolar transition characteristic to the monostable threshold transition characteristic. This experiment confirms that Joule heating plays a dominant role in the resistance transition process. In the device of ECM mechanism, there is also the problem of the instability of conductive filaments caused by Joule heating, which also causes the phenomenon that the low resistance state of the device cannot be maintained.

    What are the problems with the central air conditioning system?

    1. Excessive water flow reduces the temperature difference of the circulating water system, deteriorates the working conditions of the main engine, causes the heat exchange efficiency of the main engine to drop, and causes additional power loss.
    2. Since the flow rate of the pump is too large, the flow of cooling water and chilled water is usually adjusted by adjusting the valve opening on the pipeline, so there is a large energy loss on the valve.
    3. The pump motor usually adopts star-delta starting, but the starting current is still large, which will bring a certain impact to the power supply system.
    4. The traditional pump start and stop control cannot realize soft start and soft stop. When the water pump starts and stops, there will be a water hammer phenomenon, which will cause a greater impact on the pipe network and increase the phenomenon of bubbling and dripping of the pipe network valve. Due to the low operating efficiency and high energy consumption of the central air-conditioning circulating water system, there are many drawbacks, and it is a long-term operation. Therefore, it is absolutely necessary to carry out energy-saving technical transformation on the circulating water system.
    Air Conditioning System

    What are the logical operators in VHDL?

    In VHDL, there are six logical operators, namely: NOT – inversion; AND – and; OR – or; NAND – NAND; NOR – or not; XOR – XOR.

    The characteristics and parameters of the thermistor

    The physical properties of the thermistor are represented by the following parameters: resistance value, B value, dissipation coefficient, the thermal time constant, and temperature coefficient of resistance. Resistance value: R[Ω]. The approximate value of the resistance value is expressed as R2=R1exp[1/T2-1/T1] where: R2: the resistance when the absolute temperature is T2[K] [Ω] R1: the absolute temperature is T1[ Resistance at K] [Ω] B: B value [K] B value: B [k]. The B value is a function of the resistance change between two temperatures, and the expression is B=InR1-InR2=2.3026(1ogR1- 1ogR2)1/T1-1/T21/T1-1/T2 Among them: B: B value [K] R1: Resistance when the absolute temperature is T1 [K] [Ω] R2: When the absolute temperature is T2 [K] Resistance [Ω] Dissipation coefficient: δ[mW/℃] Dissipation coefficient is the ratio of the electrical power consumed by the object to the corresponding temperature rise δ=W/T-Ta=I^2; R/T-Ta where: δ: Dissipation coefficient δ[mW/°C] W: Electric power consumed by the thermistor [mW] T: Temperature value after reaching thermal equilibrium [°C] Ta: Room temperature [°C] I: On the heating thermistor at temperature T The current value of [mA] R: the current value of the heating thermistor at the temperature T [KΩ] When measuring the temperature, care should be taken to prevent the thermistor from heating up due to heating. Thermal time constant: τ[sec.] Thermistor’s temperature changes due to the step effect under zero energy conditions. When the temperature changes by 63.2% between the initial and final values, the time required is the Thermal time coefficient τ. Temperature coefficient of resistance: α[%/℃]α is a coefficient representing the degree of change in the resistance value of the thermistor when the temperature of the thermistor changes by 1ºC [namely, the rate of change], expressed by α=1/R·dR/DT, and the calculation formula is: α=1/R·dR/dT×100=-B/T²×100 Among them: α: Resistance temperature coefficient [%/℃] R: Resistance value at absolute temperature T[K] [Ω] B: B value [K]


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