渐进、精细的可伸缩性视频编码

精细的可伸缩性的视频编码FGS（Fine Granular Scalable)是MPEG-4标准的视频流化框架中的关键性编码技术,由于在FGS编码方案中运动补偿是参考一个最低质量的重构层,因而编码效率较低。在这篇文章中,我们首先提出了一个渐进的精细可伸缩性的视频编码框架,简称为PFGS（Progressive Fine Granular Scalable),与MEPG-4中的FGS相比,PFGS编码框架试图在增强层的编码过程中采用多个高质量的参考来提高编码效率,这是因为高质量的参考可使运动预测更准确。但是,高质量的参考也会带来一些问题,首先,增加多个参考会使得PFGS编码需要更多的内存,同时也会增加其计算复杂性,因而在这篇文章中,首先将PFGS编码框架简化为只需采用一个额外的缓存来存储参考图像,而得到的编码效率几乎和原来多个参考一样,其次,在编码过程中,由于转换参考图像会造成增强层间编码系数的振荡,从而部分地抵消了采取高质量参考的优势。文中同时提出了一个有效的消除振荡的方法,即采用高质量的参考对所有增强层进行编码而用低质量的参考来重构以解决误差传播问题。实验结果表明,我们所提出的PFGS编码框架的编码效率能比MPGE-4中的FGS提高1dB以上,同时保留了FGS所有的优点,比如精细可调性,自适应网络带宽变化和差错恢复能力等。     

Guest Editors' Introduction

Journal of Signal Processing Systems -     

Optimal stream replication for video simulcasting

Video simulcasting enables a sender to generate replicated streams of different rates, serving receivers of diverse access bandwidths. As replication introduces noticeable redundancy, balancing bandwidth consumption with user satisfaction becomes a critical concern in simulcasting. This paper investigates the above issue; more explicitly, we seek answers to the following two questions: what is the number of streams that should be generated, and what is the bandwidth that should be allocated to each stream? We derive optimal and efficient solutions, and evaluate their performance under a variety of configurations. The results demonstrate that an optimal and adaptive bandwidth allocation significantly improves user satisfaction under stringent resource constraints, and an optimal choice of the stream number yields further improvements.     

Transporting real-time video over the Internet: challenges andapproaches

Delivering real-time video over the Internet is an important component of many Internet multimedia applications. Transmission of real-time video has bandwidth, delay, and loss requirements. However the current Internet does not offer any quality of service (QoS) guarantees to video transmission over the Internet. In addition, the heterogeneity of the networks and end systems makes it difficult to multicast Internet video in an efficient and flexible way. Thus, designing protocols and mechanisms for Internet video transmission poses many challenges. In this paper, we take a holistic approach to these challenges and present solutions from both transport and compression perspectives. With the holistic approach, we design a framework for transporting real-time Internet video, which includes two components, namely, congestion control and error control. Specifically congestion control consists of rate control, rate-adaptive encoding, and rate shaping; error control consists of forward error correction (FEC), retransmission error resilience, and error concealment. For the design of each component in the framework, we classify approaches and summarize representative research work. We point out there exists a design space which can be explored by video application designers and suggest that the synergy of both transport and compression could provide good solutions     

煤焦油馏分微波萃取神府煤热解液体产物的研究

为提高煤在萃取过程中的转化率,考察微波辅助萃取煤的工业化可行性。在微波辅助下,以神府低温煤焦油馏分为溶剂,在最优操作条件下萃取神府煤,将萃取混合液在510℃条件下热解,分析了热解液体产物的性质及组成,得到了加工方案。结果表明:液体产物主要由酚类化合物、芳烃化合物及烷烃组成,酚类含量较高,其在萃取热解液体产物中的比例均达到50%以上,主要由苯酚、C1～C4苯酚组成,大于C4苯酚的含量很小,其中由苯酚、C1-苯酚、C2-苯酚组成的低级酚含量占总酚含量的70%以上,因此对液体产物进行加工时,需要将低级酚类化合物从液体产物中先分离出来。     

Investigation on thermal, electrical, and electrochemical properties of scandium-doped Pr0.6Sr0.4(Co0.2Fe0.8)(1−x)ScxO3−δ as cathode for IT-SOFC

A systematic study and evaluation were performed on the effect of scandium doping at the B site of Pr_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ (PSCF) on key material properties as cathode for intermediate temperature solid oxide fuel cells (IT-SOFC). The doped products Pr_0.6Sr_0.4(Co_0.2Fe_0.8)_(1−x)Sc_xO_3−δ (PSCFS_x, x=0.0-0.2) retained perovskite structure confirmed by X-ray diffraction, and their particles were smaller than the non-doped materials as evidenced by TEM. The electrical conductivity (EC) of PSCFS_x decreased with increasing Sc³⁺ content, but EC values were still larger than 100 S cm⁻¹ in temperature range of 300-800 °C as x ≤ 0.1. The thermal expansion coefficients (TEC) of PSCFS_x were observed to generally decrease with increasing x especially at lower temperature range of 50-600 °C. In addition, the AC impedance revealed better electrochemical performance of PSCFS_x cathode as x ≤ 0.1 than that of the undoped sample PSCF. Therefore, PSCFS_x (x ≤ 0.1) shows some potential as cathode electrode for IT-SOFC. The function of Sc³⁺ dopant was tentatively elucidated and discussed.     

肉制品中药物残留风险因子概述

肉品中药物残留问题严重影响着人体健康,近几年来肉品中兽药残留引起的食品安全问题层出不穷。随着对肉品中各种兽药残留监控的力度越来越严格和规范,研究人员发现了更多的药物残留风险因子,并开始对相关风险因子进行饮食安全性评估。本文综述了目前肉品中可能存在的抗生素、抗寄生虫、激素和抗菌化学药等4大类风险因子的具体物质类别、对人体的危害性以及国内外限量标准的比较。本文明确了肉品安全质量监控的着手点和监控的具体项目指标,并按照风险因子的危害程度和必要性来确定需要监控的风险因子。通过有效地监控和风险评估,为肉品质量安全检测和研究工作提供参考。     

蜂蜜中17种水解氨基酸的测定

目的采用酸水解法和全自动氨基酸分析仪同时测定蜂蜜中17种氨基酸的含量。方法 8种不同蜜源的蜂蜜经酸水解后,采用全自动氨基酸分析仪进行定量检测;检测器为荧光检测器,脯氨酸在波长440 nm处测定,其余16种氨基酸在570 nm波长下测定。结果 17种氨基酸的线性回归系数均达到0.99以上;方法检出限为5~10 nmoL/L,样品平均回收率为92.1%~99.3%,相对标准偏差RSD小于8.5%。经检测实际样品发现,蜂蜜中不含胱氨酸,氨基酸总量在32.214~78.439 mg/100 g范围。结论该方法快速、准确,可适用于蜂蜜中水解氨基酸含量的测定。     

A new aluminum(III)-selective potentiometric sensor based on N,N′-propanediamide bis(2-salicylideneimine) as a neutral carrier

This work describes the fabrication of a selective polymeric membrane potentiometric sensor for Al³⁺ ion based on N,N′-propanediamide bis(2-salicylideneimine) (NPBS) as a neutral carrier. The proposed sensor, with optimum membrane composition, exhibited an excellent near-Nernstian response for Al³⁺ ion ranging from 7.9 × 10^? 7 to 1.0 × 10^? 1 mol/L with a detection limit of 4.6 × 10^? 7 mol/L and a slope of 19.4 ± 0.3 mV/dec in pH 3.0 nitrate solution at 25 °C. It showed a relatively fast response time (8 s), suitable reproducibility and stability, and good selectivity towards Al³⁺ ion. The operational pH range of the proposed sensor was 2.5–4.0. The response mechanism was discussed in view of UV–visible spectroscopy and the alternating current (AC) impedance technique. In addition, the proposed sensor was successfully used as an indicator electrode in potentiometric titration of Al³⁺ ion and in the direct determination of Al³⁺ ion in real samples.     

Jitter smoothing and traffic modeling for MPEG-2 video transport over ATM networks

In this article, we study how to deal with jitter when a variable-bit-rate (VBR) MPEG-2 video is delivered through asynchronous transfer mode (ATM) networks. First, the MPEG-2 system and its timing model are reviewed and difficulties introduced by ATM cell delay jitter are elucidated. Second, approaches to smoothing network jitter for both constant-bit-rate and VBR traffic are reviewed. A novel approach to modeling the end-to-end MPEG-2 packet generation and arrival process in the presence of network jitter is next presented. Based on this model, the buffer behavior of the MPEG-2 transport stream system target decoder is simulated. Simulation results show that jitter significantly affects the required decoder buffer size and packet loss ratio. © 1998 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 9, 332–339, 1998