基于桥臂电路的能量有源回馈吸收单元研究

提出一种基于桥臂电路的能量有源回馈吸收单元(EARS),不仅能够实现桥臂电路的软开关,还能解决能量回馈过程中的环流问题。EARS由无源软开关吸收回路和能量有源回馈支路构成,无源软开关吸收回路能够实现主电路开关管的零电流开通和零电压关断;而储存于缓冲电容的能量则能通过能量有源回馈支路返回至电源侧,并解决了无源回馈支路中的环流问题。能量有源回馈支路中辅助开关管的控制策略简单并且与主开关管相互独立,有利于系统模块化,提高了系统的可靠性。最后,通过搭建1 k W的能量有源回馈吸收单元实验平台,对上述电路拓扑的有效性和优越性进行验证。     

负载限流控制全桥软开关变换器的研制

本文介绍了负载限流控制全桥软开关变换器,包括全桥软开关变换器电路结构和过载限流的工作原理,并阐述了如何实现副边整流桥的尖峰电压抑制。在理论分析的基础上,介绍了电路设计,研制了1台样机,并进行实验验证。     

White and narrow band image compressor based on a new color space for capsule endoscopy

In this paper, we present the design of a low power and hardware efficient image compressor integrated circuit for wireless capsule endoscopy application. The proposed compression algorithm supports dual-band imaging, that is, works on both white-band imaging (WBI) and narrow-band imaging (NBI). The scheme uses a novel color-space and simple predictive coding for optimized performance. Based on the nature of the narrow- and white-band endoscopic images and video sequences, several sub-sampling schemes are introduced. The proposed dual-band compressor is designed in such as way that it can easily be interfaced with any commercial low power image sensor that outputs RGB image pixels in a raster scan fashion, eliminating the need of large buffer memory and temporary storage. Both NBI and WBI reconstructed images have been verified by medical doctors for acceptability. Compared to other designs targeted to video capsule endoscopy, the proposed algorithm performs strongly with a compression ratio of 80.4% (for WBI) and 79.2% (for NBI), and a high reconstruction peak-signal-to-noise-ratio (over 43.7 dB for both bands). The results of the fabricated chip are also presented.     

基于感知器的快速彩色图像无损压缩算法

针对彩色图像像素和颜色分量之间存在的相关性，将神经网络中的感知器技术引入彩色图像的无损压缩算法中，提出了一种新的预测模型。应用感知器的自学习和自适应能力，对预测值进行自适应调整，使算法在运行过程中具有很小的预测残差并具有较小的动态范围。同时应用颜色空间变换来减小颜色分量间的相关性。相对于新的国际标准JPEG—LS，这种预测模型具有较低的计算复杂性。对比实验结果说明，这种算法的性能明显优于传统算法，在压缩比损失很小的前提下，其执行速度高于JPEG—LS。     

预测与可变长编码在图像压缩中的应用

图像压缩成为了多媒体技术的关键和瓶颈.预测编码(DPCM)和可变长编码(VLC)是两种最重要的无损压缩算法.介绍预测编码的原理,证明了对DPCM数据进行可变长编码的可行性,并对标准测试图像进行测试得到了测试结果,最后对结果进行了分析.     

FPGA-based architecture for hardware compression/decompression of wide format images

In this article, we present a popular lossless compression/decompression algorithm, GZIP, and the study to implement it on an FPGA-based architecture, the ADM-XRC board from ALPHA DATA parallel system ltd. The algorithm is lossless, and applied to “bi-level” images of large size (A0 format). It ensures a minimum compression rate for the images we are considering. It aims to decrease storage requirements and transfer times, which are critical for wide format printing systems. In a wide format document industry, raster data are most of time processed in an uncompressed format, in order to apply processing (P) before printing (p). An example of a copy chain is composed of scanner, set of processing operations, storage, link and printer. We propose to use a compressed format as the new data-flow representation to improve the performances of the printing system. For example, the compression (C) is applied as soon as the data are produced by the scanner, and decompression (D) is performed at the last stage, before printing. The set of processing is applied to compressed images. The proposed architecture for the compressor is based on a hash table and the decompressor is based on a parallel decoder of the Huffman codes. We implemented the proposed architecture for compression and decompression algorithms on FPGA Xilinx Virtex XCV 400.     

A module-based LSB substitution method with lossless secret data compression

All the various data hiding methods can be simply divided into two types: (1) the extracted important data are lossy, (2) the extracted important data are lossless. The proposed method belongs to the second type. In this paper, a module-based substitution method with lossless secret data compression function is used for concealing smoother area of secret image by modifying fewer pixels in the generated stego-image. Compared with the previous data hiding methods that extract lossless data, the generated stego-image by the proposed method is always with better quality, unless the hidden image is with very strong randomness.     

无损吸收网络在开关电源中的应用

分析了几种典型的无损吸收网络原理,给出了设计方法以及无损吸收网络在典型开关变换器中应用的例子。最后提出了在实践中的应注意的问题。