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    What is a computer network?

    Computer network is a new technical field produced by the combination of computer technology and communication technology. A number of computers are connected together with communication channels, and they can exchange information and share resources with each other, forming a computer network.

    What characteristics should medical sensors have?

    • Medical sensors should have the following characteristics:
      1. Sensitivity high enough to detect weak biological signals.
      2. Signal-to-noise ratio as high as possible in order to extract useful information in the background of interference and noise.
      3. Good accuracy to ensure that the detected information is accurate and reliable.
      4. The response speed is fast enough to follow the change of the amount of biological information.
      5. Good stability, long-term detection drift is small, and the output is stable.
      6. Good interchangeability, convenient debugging and maintenance.

    What is the development trend of the next generation EDA software design method?

    EDA software design technology continues to develop, and the general trend can be summarized as follows:
    Supports continuously updated device families, more and more humanized design; better and better design optimization effects; faster and faster simulation speed and higher simulation accuracy of simulation software; more and more comprehensive optimization effects of comprehensive software Good; more and more complete analysis and verification methods; the efficiency and optimization effect of layout and routing software are constantly improving.

    What are the problems with DLC films?

    • The binding force between membrane and substrate is poor.
    • The thickness of the diamond-like carbon film has a direct impact on the absorption coefficient.

    What parts of the sensor are made up of?

    The sensor is composed of several parts such as power supply, sensing components, embedded processor, memory, communication components and software.

    Briefly describe the MSDMA features?

    MSDMA supports storage data scaling, especially picture-in-picture (Picture-in-Picture, PIP) operation requires two different image data.
    The first image is stored by a residual video codec (such as H. 264, MPEG-4, etc.); the second image is saved by the MSDMA path.
    The MSDMA path outputs YCbCr/RGB format through the scaler/DMA channel; both images are displayed and controlled by the LCD controller.
    If the MSDMA channel reads data and requires the preview/codec path, the special function register SEL_DMA_CAM_P signal must be set to ‘1’. This input path is called the memory scaling DMA path.

    What is the use of low-power Bluetooth?

    The SM architecture adopted by Bluetooth Low Energy is designed to minimize the resource requirements of slave devices. The main computing work is placed on the main device with strong computing power.

    What are the main features of the bundle layer structure?

    1. Region and gateway: A region is a specific network with specific protocols and communication requirements. Area B includes a bus carrying a DTN gateway, which travels between DTN gateway 3 and DTN gateway 5 . Region D includes a regularly connected satellite link. A gateway is essentially an access point used to connect two areas with different network architectures and protocol stacks. It consists of two logical parts that sit on top of the corresponding transport layer protocols of two adjacent areas. Two nodes are said to be in the same area if they can communicate without going through a DTN gateway. Area boundaries are used to represent interconnection points between different network protocol stacks. When it is necessary to ensure reliable delivery of messages, DTN gateways are responsible for storing messages in persistent storage. In addition, the DTN gateway also needs to assume the responsibility of mapping between different transmission protocols.
    2. Name tuple: In order to carry out message routing, DTN adopts the form of name tuple to identify the target node or target node group. A name tuple consists of two variable-length parts of the form {region-name, entity-name. The region name is globally unique and has strict topological meaning through hierarchical construction. The entity name is the name of the node in a specific area, which is unique within the area but not unique outside the area, and can be of any structure.
    3. Postal-style delivery service: All kinds of network resources in DTN are strictly limited, so it is very necessary to use a priority-based resource allocation and message transmission mechanism. Similar to postal services, the DTN architecture adopts three priorities: Bulk, Normal and Expedited. Conceptually correspond to low, medium, and high priority, respectively.
    4. Routing: In the routing and forwarding framework provided by the DTN architecture, DTN is defined as a multigraph, that is, there may be multiple connection edges between nodes. Based on network characteristics, the contact between nodes is classified as Persistent, On. There are five types of demand, Scheduled, Predicted, and Opportunistic, of which the latter three are the most common in DTN. To provide maximum flexibility in area design, the DTN architecture itself does not specify any particular type of routing mechanism.
    5. Reliability and custody transfer: Custody transfer is a concept proposed to maintain the end-to-end connection state and deal with high packet loss rate and resource shortage. Its core means that the message jumps from one DTN node to the next DTN node and realizes reliable delivery. According to the storage capacity of the nodes, the DTN architecture divides the nodes into two types: persistent and non-persistent. The former has sufficient storage resources, while the latter has relatively insufficient storage resources. DTN is faced with a high message packet loss rate, and it is necessary to ensure that those nodes that do not have sufficient resources do not have to undertake and maintain the task of end-to-end reliable transmission. Therefore, once a custodial bundle is delivered to a Persistent node, the source node does not have to keep maintaining a copy of the bundle.
    6. Convergence layer: The functions provided by the bottom layer of the DTN architecture may have significant changes, such as reliable transmission, flow control, and congestion control. Assuming that the underlying layer can achieve reliable transmission, it is necessary to add a protocol stack containing a specific aggregation layer to ensure the realization of these underlying functions. For example, when reliable delivery is provided by the underlying transport, the corresponding aggregation layer only needs to provide corresponding link state management.
    7. Time synchronization (time synchronization): DTN architecture requires time synchronization between communication nodes. This requirement originates from the fact that many distributed applications in challenging environments need time synchronization, such as message bundle identification, routing scheduling, message lifetime calculation, etc., which are usually completed through an external non-DTN protocol.
    8. Flow control (flow contr01) and congestion control (congestion contr01): Flow control in the DTN architecture refers to limiting the sending rate of DTN nodes to match the receiving rate of the next hop node. Flow control decisions must be made within the binding layer, although it may require support from the underlying transport layer. Congestion control refers to dealing with competition for persistent storage resources (persistent storage) in the DTN gateway. The RFC standard does not specify a specific congestion control mechanism, so the congestion control mechanism is an open research problem.
    9. Security: The security of the DTN architecture requires limited access to available scarce resources. Its main goals are to prevent unauthorized applications from exploiting network resources, and to prevent authorized applications from accessing higher-level services than themselves. Therefore, it becomes necessary to identify and discard damaged message bundles and detect damaged nodes. A popular security mechanism is hop-by-hop and end-to-end authentication and integrity mechanisms. Its purpose is to use the data integrity of the application layer to implement access control for data forwarding and storage respectively.

    At the network layer of ZigBee, the ZigBee protocol specification defines three types of devices, what are they?

    At the ZigBee network layer, the ZigBee protocol specification defines 3 types of devices:
    ZigBee Coordinator (ZC), ZigBee Router (ZR) and ZigBee End Device (ZED).

    What functions does the reader have?

    To provide energy to the tag, realize communication with the electronic tag, realize communication with the computer, realize multiple electronic tag identification, and realize moving target identification, the reader must have the function of data recording.


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