An Algorithm to Enhance the Performance of Data Service Over CATV Broadband Networks

Emerging CATV networks are evolution to Hybrid Fiber/Coax plants. It is widely believed that the HFC network will play an important role in providing broadband accessing service to subscribers due to it's large excess bandwidth and high penetration to the home. Asymmetry broadband data service is the main service provided in the HFC broadband access networks now. It's performance will determine whether the subscribers be satisfied or not and affect the growth of HFC broadband access networks. The authors outline the mechanism of transmitting data in the upstream channel of the HFC network, and analyze how it affecting the performance of data service. The performance of data service and TCP protocol in HFC network is examined. An optimal scheme of bandwidth allocating algorithm for the upstream channel is proposed to enhance the performance of the data service over these networks.     

Cell Loss Analysis Based ATM Networks of On-Off Traffic Source

Cell loss, which occurs when buffers overflow in ATM switches, is a key measure for the performance of an ATM network .An ATM network must be designed for very low and predictable cell loss probabilities to provide adequate quality of service for all users. Many methods have been proposed for allocating bandwidth and determining buffer size requirements to provide quality of service guarantees. These methods are subject to overly optimistic allocations or overly pessimistic allocations. The authors present an exact analysis of cell for on off traffic source which can be used in concert with probabilistic methods to ensure that buffer and bandwidth allocation are mode between the best case and worst case requirements.     

MAC of IEEE802.11 b

IEEE802.11b LAN use wireless media to transmit information. Since the wireless media is more complex than wired media, the MAC layer access controling mechanism of IEEE802.11b is more complex. The thesis describes the MAC layer access controling mechanism of IEEE802.11b--CSMA/CA(carrier sense multiple access/collision avoid) and two implementation modes,which are DCF(distributed coordination function) controling mode and PCF(point coordination function) controling mode. At the same time, the thesis simply introduces the error controling problem.     

马铃薯/玉米2:1行比套作不同模式对马铃薯产量及光合性能的影响

为探索马铃薯/玉米2:1行比套作下,马铃薯高产的最佳空间配置模式,在带宽、行距、间距、窝距等空间因子不同配置的4种马铃薯/玉米2:1行比套作模式下,研究不同模式下马铃薯的产量及其光合性能指标变化。结果表明,带宽为120 cm模式的鲜薯产量和商品薯率、叶面积指数(LAI)、叶绿素含量(SPAD)及光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)均极显著或显著高于其他模式,表明2:1行比下以间距、马铃薯小行距、窝距均为40 cm的中等距离空间配置更有利于光合作用,效果最佳,宜在生产中推广应用。     

Using Agent Server to Enhance the Performance of Remote Data Service Based on HFC Network

The bi-directional Hybrid Fiber/Coaxial (HFC), which has almost 1GHz frequency bandwidth to transmit information, is the best access mode except Fiber to the Home (FTTH). Initial experiences indicate that real-world HFC networks are susceptible to a variety of radio-frequency impairments that significantly reduce the benefits of using high-speed cable modems. In this paper, the performance of data services in the TCP sub-layer of a HFC network is discussed and an agent server is used to enhance the performance of remote data transmission.[WT5HZ]     

Allocation patterns and phenology in wild and selected accessions of annual and perennial Physaria (Lesquerella, Brassicaceae)

Two processes that determine a good performance of plants in arid environments are phenology and resource allocation patterns. With a longer growing season and larger allocation to root, perennials achieve better access to resources and are more resilient to stresses than annuals. In traditional agricultural systems selection for optimal soil nutrient uptake has been a secondary breeding objective, because crops receive subsidies of water and fertilizers. However in arid lands, caution is required during domestication, to avoid changes in structural traits which may be the basis for sustainable production. Due to inherent differences in hierarchy among annual and perennial species, we propose that the changes in phenology and allocation brought about by selection will depend on the life cycle. We performed field studies comparing wild and selected accessions of annual and perennial species of Physaria. Life cycle determined the functional basis of seed yield. In annuals, selection resulted in early anthesis (1 week earlier), a lower allocation to roots and leaves (twofold lower), and an increase in harvest index (an increase of 62%). Selected perennials had higher biomass at maturity (45% higher), linked to a longer reproductive period (3 weeks longer) than their wild relatives. The vegetative allocation found in wild perennials remained unchanged after selection. While annuals selected for seed yield could compromise the capacity for acquisition of resources, selection in perennials did not modify the allocation strategy responsible for their positive adjustment to low resource environments. We found a trade off between seed yield potential and yield stability that resulted in lower performance of selected accessions in low quality environments in relation to their wild relatives.     

Performance analysis and comparison of IEEE 802.11 distributed coordination function and improved schemes

To improve the media access control mechanism and enhance the performance of large scale wireless LANs, the distributed coordination function of IEEE802.11 standard and two typical improved schemes are studied extensively. Compared with the distributed coordination function, the fast collision resolution mechanism greatly enhances the throughput, but deteriorates the delay jitter and fairness of wireless LANs. The new self adaptive distributed coordination function markedly improves the delay jitter and fairness performance, while enhancing the throughput of wireless LANs to a certain degree. Hence, with further improvement, the new self adaptive distributed coordination function is more suitable for large scale wireless LANs for multimedia information transmission.     

棉花微管结合蛋白基因GhMAP1-LC3的克隆与表达分析

应用RT-PCR从陆地棉(Gossypium hirsutum L.)石远321开花当天胚珠中分离到一个553 bp的片段,含有一个360 bp的开放读码框,推导的氨基酸序列（119个氨基酸）与水稻、拟南芥的MAP1-LC3 (Microtubule-associated Protein 1-Light Chain3)分别具有94%与90%的同源性,由此推测该基因为编码棉花微管结合蛋白基因家族的一     

Hysteretic Behavior of Composite Deep Beam Infilled Steel Frame

The Quasi static tests of one steel frame and two the composite deep beams infilled steel frames were carried out. The effects of the deep beams on the load capacity, ductility, hysteretic property and energy dissipation of pure steel structure were analyzed. It is found that the hysteresis curve is a straight line with the constant of the stiffness at the beginning and without residual deformation. And the hysteresis curve of specimen was full after yielding, and the skeleton curves had a clear plastic flow phase with triple linear. The lateral drifts of the beam specimens at failure were 1/25 and 1/22. The composite deep beams enhance the initial stiffness, yield load and maximum load bearing capacity of steel frame. Therefore, seismic performance of the composite deep beams is better.     

Changing rules of the game: local responses to decollectivisation in Thai Nguyen,Vietnam

This paper documents the uneven experiences of decollectivisation, using Thai Nguyen province as a setting for an exploration of divergent outcomes of, and local responses to, land allocation. Ethnicity, blood relations and settlement history are identified as emerging axes of differentiation in new patterns of vulnerability regarding access to land. This trend is evidenced by the phenomenon of farmers who migrated to the region during the collectivisation period and were subsequently left landless as longer term residents from other ethnic groups reclaimed their ancestral lands.     

Constructing organization network for community-oriented collaborative product design

Community-oriented collaborative design is an emergent form of collaborative product development, in which the range of collaborative partners extends to wide area community members. It is difficult to construct the organization network because the accurate features of the wide area community members are hard to access. Aiming at this problem, an organization network constructing method based on bidding mechanism is proposed. First, the bidding process based on contract net with confirmation protocol (CNCP) is presented. Then, considering the false profit declared by the bidders, a multiple rounds bidding process combined with genetic algorithm (GA) is used to get the best sub-projects allocation scheme, in which the total payment of sub-projects is minimal and the project due time is satisfied. A case analysis shows that the method can eliminate the false profit declared by the bidders and provides an operable way to construct network organization for community-oriented collaborative design.     

多旋翼授粉无人机的作业航迹规划

目前果园存在劳动人口老龄化、人工辅助授粉劳动效率低和缺乏数字化精准管理的现状。为了缓解这一现状,本研究首先阐述了多旋翼授粉无人机的前期关键技术准备,包括授粉父本花药的优化组合、花药的商业化存储等。然后,针对单机多旋翼授粉无人机存在的花粉喷洒均匀性差的问题,给出了花粉精准喷洒作业的多旋翼授粉无人机的集群实施策略;在无人机集群编队目标位置分配、回避碰撞和集群队列区域路径规划等核心技术的基础上,设计了多旋翼授粉无人机的自动作业航迹规划技术。最后,在Matlab环境下,实现3单元多旋翼授粉无人机集群授粉的虚拟仿真。多旋翼授粉无人机将为构建智慧农业生态无人农场的精准化种植,提供超前一步的理论探索和可行性应用方案。     

Low complexity rate control scheme for real-time video coding

Considering the deficiency of H.264 rate control scheme and the coding efficiency requirements for real-time encoding,a low complexity rate control algorithm in MB-layer is proposed..MAD is predicted by combining motion vector and the temporal and spatial correlation to reduce the complexity of G012-MAD prediction algorithm from linear regression to the complexity of the weighted average. For the rate-distortion model,the linear model with low computational complexity instead of the quadratic fitting algorithm in G012 is used,while the possibility of is discussed combining with SSIM. For the fluctuation of the PSNR of the coded image with large movement,the determination of QP in GOP layer and the bit allocation of P frame are improved,and the current quantization parameter is adjusted by making full use of the information of coded MBto control the rateeffectively. The experimental results show that the algorithm is more effective in resisting the fluctuation of PSNR for smoothly output sequence,and can decrease computational complexity.     

1-MCP结合自发气调包装对‘空心李’果实软化和细胞壁代谢的影响

探讨果实软化与细胞壁代谢之间的关系及1-甲基环丙烯(1-MCP)结合自发气调包装(MAP)对果实软化的调控机制,为生产中李果实软化问题提供理论依据和技术参考。笔者以贵州省特色果品‘空心李’为试材,通过测定果实的硬度、细胞壁代谢成分和细胞壁代谢酶活性的变化,研究1-MCP、MAP及两者结合(1-MCP+MAP)对(20±1)℃下果实软化的抑制效应。结果表明：（1）与对照（直接放于纸箱内）相比,1-MCP、MAP及1-MCP+MAP处理抑制了果实硬度下降,原果胶和纤维素降解,抑制了多聚半乳糖醛酸酶(PG)、果胶甲脂酶(PME)和纤维素酶(Cx)活性增加,抑制效果为1-MCP+MAP>1-MCP>MAP。（2）果实硬度的下降与原果胶和纤维素含量呈显著正相关,与可溶性果胶含量关系表现不一,1-MCP和1-MCP+MAP处理与可溶性果胶含量呈显著负相关,而对照和MAP处理与可溶性果胶含量没有表现出明显的相关性。1-MCP、MAP、1-MCP+MAP处理和对照果实硬度的下降与PG和PME活性存在显著负相关,对照和MAP处理的果实硬度与Cx活性表现显著负相关,1-MCP和1-MCP+MAP处理果实硬度与Cx活性没有表现相关性。1-MCP结合MAP对沿河‘空心李’果实硬度下降、细胞壁物质降解及其相关酶活性有显著抑制作用,能够抑制‘空心李’果实软化,延长保鲜时间,减少采后损失。     

A Subchannel Allocation Policy of Multicarrier CDMA

To attain high rate data and high quality of service in wireless communication, a subchannel allocation policy combined with subcarriers and power allocation is proposed. In the proposed system, instead of identical power over the subcarriers in parallel, each user's DS waveform is transmitted over the subchannels that have large fading amplitude among all the subchannels. The powers of the subcarriers with small fading amplitude are allocated to the subcarriers with large ones. It can effectively suppress multiple-access interference while obtaining diversity gains. The allocation policy based on fading amplitudes has the advantages of low computation and good convergence compared with the policy proposed in other papers. Thus, it is suitable for engineering.     

地方农业高校产-学-研合作的动力机制构建

产-学-研合作是基于技术创新的上、中、下游的对接与耦合。地方农业高校作为高等教育系统的重要组成部分,是致力于区域经济社会发展的生力军,地方农业高校产-学-研合作的动力因素主要涉及经济、社会利益获取的内动力与市场需求以及政府支持的外动力。构建地方农业高校产-学-研合作的动力机制,促进生产要素与劳动要素的有效配置,促成科技成果的高效转化是提升区域产-学-研合作水平,加速区域创新体系建设的有效途径与必然选择。     

碰撞对玉米籽粒结构损伤的实验研究

对不同品种的玉米籽粒进行下落碰撞实验,测定玉米籽粒破碎率与下落高度的关系。对下落碰撞后未破碎的完整籽粒进行静态压缩实验,测定玉米籽粒经过碰撞后压缩特性的变化规律。结果表明:玉米籽粒破碎率随下落高度的增大而增大;下落碰撞后未破碎的完整籽粒的最大破坏力、最大破坏能随下落高度的增大而减小,即下落碰撞后未破碎的完整籽粒的结构损伤随下落高度的增大而增大。     

叶类蔬菜气调包装保鲜技术及其机理的研究进展

笔者简述了叶类蔬菜（简称叶菜）的保鲜现状,通过归纳国内外气调包装保鲜技术在叶菜上的应用研究,分析了气调包装技术在叶菜保鲜中低能耗、操作方便和安全可控的优点,指出了目前缺乏叶菜保鲜技术体系和针对性强、保鲜效果好的包装材料,在此基础上通过总结气调包装下自由基理论在水果和根茎类、瓜果类蔬菜上的应用,提出了基于自由基中心效应的叶菜气调包装保鲜机理,对转录组学和蛋白组学在揭示保鲜机理的应用进行了展望。     

An overview on long-term agro-ecosystem experiments: Present situation and future potential

Modern Long Term Agricultural experiments (LTAE) have a long history initiated when modern agricultural science was just at its beginning. After about 180 years from the start of the first of the classical Rothamsted experiments in 1843, these experiments still maintains a consistent appeal for researchers and the interest on LTAEs is growing, as shown by the increasing number of papers dealing with long-term effect of agricultural practices, frequently considering topics, such as sustainability, environmental quality, species-adaptation impacts, that were never envisioned by the founders of classical LTAEs. However, these experiments have numerous constraints and weakness that have to be clearly understood and evaluated when using the data, especially for up-scaling or modelling purposes.Nevertheless, in our vision, the strengths and the opportunities of LTAEs are still overwhelming, particularly if connected in networks allowing a standardisation of procedures and facilitating the access to data and to the experiments of researchers external to the institution hosting the LTAE.     

Allocation Rule in Life-cycle Assessment Inventory of MSW''sIncineration System

The allocation MSW disposal measure, which would occupy large quantity of land, cannot meet the need of the development of the urban area and economics and the great yielding of MSW. The author gets the conclusion that the nost suitable disposal measure for MSW is incineration. The allocation and the life cycle evaluation are both focused on.The principles and influencing factors of the allocation in relation to these systems are discussed in detail. A conclusion is that the factors of economic and envronment policy are more important than technique.