一种应用于MPEG-2AAC格型自适应滤波器的FPGA实现

本文给出了格型自适应滤波器在AAC中的应用，提出了一种AAC解码器中预测模块的FPGA实现方案，该方案根据时序图进行VHDL语言的描述，并采用流水线结构和运算单元分时复用，可以有效地提高运算速度，满足实时性的要求。     

Analysis of AAC walls subjected to vertical load

The paper describes the results of testing six autoclaved aerated concrete (AAC) walls on a natural scale. The walls were made of 18 cm wide blocks and thin layer joints. Reinforced and non‐reinforced walls were tested. Basalt grids and typical steel reinforcement (truss type) were used as reinforcements. The load was applied by a reinforced concrete rim beam. In the first part of the tests, the impact of the opening (window) on stress distribution and the load capacity of the wall was analysed. In the second part of the tests, the unequally loaded connection zone of perpendicular walls was analysed. The results were used to draw practical conclusions on rules of additional reinforcement of zones surrounding openings and connection zones of perpendicular walls.     

加气混凝土自保温节能体系的研究与实践

本文以福州大学建筑节能示范公寓为对象,根据加气混凝土砌块的特性,总结了自保温节能体系的施工技术措施,在实测基础上采用建筑热环境模拟工具DeST进行全年能耗模拟计算,分析了加气混凝土自保温节能体系的节能效果。     

低成本SoC平台MPEG-4 AAC解码器优化策略

提出了在低成本SoC平台的软件优化策略,包括基于统计分析的浮点到定点转换策略和面向性能优化的片上存储器容量定制策略,在此基础上针对计算密集性应用提出了完整的优化方法。通过实现MPEG-4 AAC实时解码,表明该优化策略在性能和成本方面的有效性。这一策略与方法也适合其他DSP应用。     

AAC砌块墙体抗震抗剪强度计算方法

在试验数据与结果分析的基础上,得出高宽比与竖向压应力对AAC砌块墙体抗震抗剪强度影响较显著,同时比较已有的几种砌体抗剪强度计算公式,提出以主拉力理论为基础,考虑高宽比影响的无筋AAC砌块墙体抗震抗剪强度计算公式,该公式与试验结果吻合较好。通过分析表明:当高宽比对墙体的抗剪强度影响较大时,该公式具有较普遍使用意义。     

基于PLI算法的AAC反量化和PNS解码模块设计

针对AAC(Advanced Audio Coding)解码器中具有复杂运算因而难以硬件实现的反量化模块和知觉噪音替代(Perceptual Noise Substitution,PNS)模块,提出用分段线性插值(Partition and Linear Interpolation,PLI)进行近似计算的方法.其基本原理是将复杂的曲线分割成多个区间,在每个区间内用线性插值的方法进行近似.利用该方法设计的反量化模块和PNS解码模块获得了较高的运算精度,最大运算误差率分别为2e-4和5e-3,全部运算可分解为简单的查表、乘法、加法和移位运算,易于硬件实现.FPGA验证结果表明,反量化模块仅耗用了45个逻辑单元和2 304ROM bits,PNS解码模块仅耗用了21个逻辑单元和144ROM bits,且解码音质良好,没有产生可感知的噪音.     

AAC窗型判定和量化模块的改进算法

由于先进音频编码(AAC, Advanced Audio Coding)标准中使用了较为复杂的心理声学模型和两层嵌套循环量化模块,使得其编码复杂度明显增加,从而影响了实时编码,所以,对于有实时编码要求的系统,必须对标准使用的心理声学模型和量化模块进行改进。本文针对AAC心理声学模型中的窗型判定子模块,提出了基于时域方差变化率的窗型判定算法;并且通过对AAC量化噪声评估模型的推导,设定量化因子初值,在可变比特率条件下无需循环就可实现量化编码,在固定比特率条件下可单循环实现量化编码且在96kbps码率条件下量化循环次数为1-2次。改进后的AAC编码器在TMS320C6727B实验平台上窗型判定模块运算量为1.79每秒百万时钟周期(MCPS, Million Cycles Per Second),量化模块为14.67 MCPS,并且经测试证明音质并无明显失真。      

改进的AAC多模式实时匹配算法

AAC算法（Advanced AC）是使用最为广泛的多模式串匹配算法,匹配性能高,匹配时间稳定。针对AAC算法为判定转移目标状态是否为终结状态,在匹配时每读入一个字符都要访问output表,代价较高的问题,通过两种方法改进了AAC算法。第一种方法为拷贝自动机中的终结状态,将其附加在AAC自动机后,并将原自动机中指向终结状态的转移目标修改为附加状态,直接根据转移目标位置判断当前状态是否是终结状态,从而提出Advanced AC with Additive state（AACA）算法。第二种改进方法为将自动机中指向终结状态的状态转移值置为负数,根据转移目标的值直接判断目标状态是否为终结状态,从而提出Advanced AC with Negative state（AACN）算法。以上两种改进算法只有在发现模式匹配时才需进行output表的访问。实验数据表明：AACA和AACN算法性能均高于AAC算法,特别在中小规模匹配上,性能提升更为明显。     

Determination of amylopectin structure and physicochemical properties in rice endosperm starch of mutant lines derived from Malaysian rice cultivar MR219

BACKGROUND: Characterization of starch properties and functionality can apply breeding program selection for desirable traits such as eating, cooking and processing qualities to meet consumer preference. Low amylose content is generally preferred in Malaysia because of cohesive, tender and glossy cooked rice. Rice high in short‐chain amylopectin has a lower transition temperature of starch gelatinization. In the continuing search for improved starch quality in rice cultivars a study was carried out with new mutant lines MR219‐4 and MR219‐9, derived from MR219. RESULTS: MR219 and its mutant lines contain L‐type amylopectin, being high in amylopectin of intermediate chain length with degree of polymerization 12‐21. The apparent amylose content (AAC) in MR219‐4 had lower AAC value (19.2%) compared to other lines. A strongly negative correlation was found between chain‐length fraction of amylopectin and transition temperatures—onset temperature peak temperature, and conclusion temperature (0.992, 0.958, 0.950; P < 0.01)—with fraction b1 (fb1), respectively. CONCLUSION: The Malaysian lines studied contain L‐type amylopectin and offer a better understanding of grain quality improvement in terms of starch properties and functionality. This information will be directly applicable to select for desirable traits in future breeding programs. Copyright © 2012 Society of Chemical Industry     

加气混凝土断裂能测定的尺寸效应

在加气混凝土断裂参数的研究及实际工程应用中，尺寸效应是很受关注的。在本研究过程中，采用了ＲＩＬＥＭ推荐的试件，研究了试件尺寸（厚度及断裂韧带高度）对加气混凝土断裂能测定的影响。研究表明，对于试验中采用的加气混凝土而言，当试件厚度大于２００ｍｍ及韧带高度大于１３０ｍｍ时，尺寸效应可基本忽略不计。该尺寸在实验室中是可以满足的。