G.723.1双速率语音编解码算法在TMS320VC5402上的实现

本文先简单介绍了G.723.1双速率编解码算法标准，然后根据TI公司的DSP芯片TMS320VC5402的性能特征，在深入分析G.723.1标准的C源代码后，对算法进行了一系列优化。文中详述了这些优化方法。最后介绍了一个实际的硬件实现。     

16V240ZC型柴油机电子液压式调速器故障浅析

723Plus＋UG电子液压式调速器在16V240ZC型船用柴油机上获得了广泛的应用并取得了良好的控制效果。针对该型号的调速器在实际使用过程中遇到的一些典型问题及解决过程进行了阐述。     

FATIGUE LIFE OF AN AUTOFRETTAGED THICK-WALLED PRESSURE VESSEL WITH AN EXTERNAL GROOVE

Abstract— Fatigue tests that simulate an autofrettaged thick-walled pressure vessel with an external groove under pulsating internal pressure loading conditions were performed using specimens taken from an autofrettaged thick-walled pressure vessel. Load-controlled simulation fatigue tests using rectangular, elliptic, and shot peened elliptic grooved specimens were performed for three different autofrettage levels of 50, 75, and 100% overstrains. In order to estimate the fatigue life of the thick-walled pressure vessel subjected to pulsating internal pressure, the local strain approach was considered to assess the crack formation life. A cyclic stress-strain relation and fatigue damage models determined from strain-controlled low cycle fatigue tests were employed to estimate the fatigue life of the autofrettaged thick-walled pressure vessel. Larger local stresses and strains were obtained from the Neuber's rule compared to the linear rule and these led to conservative fatigue life estimations. Estimated fatigue lives were obtained within factors of 2 to 4, compared to the experimental fatigue lives determined from the simulation fatigue tests.     

煤矿井下Android可视语音通信终端设计

提出了一种基于低功耗ARM Cortex-A8内核的煤矿井下可视语音通信终端设计方案,详细讨论了可视语音通信终端的功能、硬件组成和软件模块。该方案在Android嵌入式操作系统平台上,结合SIP协议和语音视频编解码器实现井下终端的可视语音通信功能。测试结果表明,可视语音通信终端整机功耗可控制在20W以内,能够实现本质安全设计;终端进行语音对讲时CPU负荷很轻,处理视频压缩和显示时,CPU平均使用率能够保持在50%以下,性能满足可视对讲需求。     

GPRS设备IP语音传输可行性研究

通过对多种语音编解码算法的分析，提出了采用G.723.1编解码算法并进行优化的方案。实验结果证实：在GPRS网络窄带宽下进行实时语音传输是可行的，该方案可以广泛应用到如长途物流管理、野外勘探等领域。     

新型语音压缩芯片CT8022

介绍了DSPG公司生产的语音压缩专用芯片CT8022的引脚功能和主机与存储器的接口，给出了CT8022的工作原理，工作模式，工作流程和使用方法，最后给出了CT8022与主机组成的语音压缩应用电路的连接方法。     

基于LM723的煤矿工作面本安电源的设计及实现

工作面自动化是煤矿综合自动化系统发展的一个重要方向。为能驱动工作面自动化系统中相关的大功率电气设备,要求本安电源应具有较大的的输出电流。文章设计了一种基于LM723的矿用大电流输出本安电源,输出电压12V,最大限流1.4A,满足了工作面自动化系统相应的电气设备的供电要求。     

Distinct squares in run-length encoded strings

Squares are strings of the form ww where w is any nonempty string. Two squares ww and w^′w^′ are of different types if and only if w≠w^′. Fraenkel and Simpson [Avieri S. Fraenkel, Jamie Simpson, How many squares can a string contain? Journal of Combinatorial Theory, Series A 82 (1998) 112-120] proved that the number of square types contained in a string of length n is bounded by O(n). The set of all different square types contained in a string is called the vocabulary of the string. If a square can be obtained by a series of successive right-rotations from another square, then we say the latter covers the former. A square is called a c-square if no square with a smaller index can cover it and it is not a trivial square. The set containing all c-squares is called the covering set. Note that every string has a unique covering set. Furthermore, the vocabulary of the covering set are called c-vocabulary. In this paper, we prove that the cardinality of c-vocabulary in a string is less than , where N is the number of runs in this string.     

Multi-degree reduction of Bézier curves using reparameterization

L₂-norms are often used in the multi-degree reduction problem of Bézier curves or surfaces. Conventional methods on curve cases are to minimize , where and are the given curve and the approximation curve, respectively. A much better solution is to minimize , where is the closest point to point , that produces a similar effect as that of the Hausdorff distance. This paper uses a piecewise linear function L(t) instead of t to approximate the function φ(t) for a constrained multi-degree reduction of Bézier curves. Numerical examples show that this new reparameterization-based method has a much better approximation effect under Hausdorff distance than those of previous methods.     

G.723.1语音编码器算法的聚类优化策略及其应用

在实现G.723.1编码器算法的基础上,提出了一种针对码本搜索的聚类优化策略,利用聚类分析的结果,对原始码本进行了分组及重构等处理,从而实现了快速搜索。测试及系统的实际运行情况表明,在使算法复杂度下降约1.46MIPS的条件下,优化结果仍能保证解码端的音质无明显下降。