Flash memory has been widely adopted in various consumer products for information storage, especially for embedded systems. With strong demands on product designs for overhead control and performance requirements, vendors must have an effective design for the mapping of logical block addresses (LBAs) and physical addresses of data over flash memory. This paper targets such an essential issue by proposing a configurable mapping method that could trade the main-memory overhead with the system performance under the best needs of vendors. A series of experiments is conducted to provide insights on different configurations and the proposed method, compared to existing implementations.
Online (Web-based) examination is an effective solution for mass education evaluation. However, due to the incomplete of network security, students can communicate with each other, and we can't prevent the cheating. Therefore, keeping the security of a online examination has become an important issue. This paper focuses on how to implement a secure environment for online-examination in the general academic network environment without the need of special network topologies and hardware devices. It not only reduces the system administrator's load, but also enhances the system flexibility to fit every teacher's needs. We use (1) the distributed firewall techniques to control the network packets of all machines, and (2) the centralized security policy management to control the security policies for all machines. Beside the above mentioned , we also design some mechanisms to prevent the possible network attacks and cheating, which enhance the security of the online examination environment.
In the office environment the USB devices attached to different hosts can be shared among hosts through the local area network. With USB transaction relay technique, all the frequently used USB devices can be grouped together as some sort of virtual USB server. The USB devices in this virtual server can be accessed by any office member using the USB client. A virtual USB host driver under Windows OS is implemented to enumerate the virtual USB devices from the client side. The enumerated virtual device will mimic the real counterpart and the original device driver can be applied without any modification. Theoretically almost all the USB devices without strict timing requirements can be shared with this USB device sharing system. To release the inconvenience of exclusive access properties caused by the nature of the USB protocol, certain management functions are introduced.
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