二维公差带的位置精度分析

本文通过二维公差带图形的分析,提出位置度偏移系数和公差带面积利用率两个概念,从而得出方形公差带的位置精度最为理想的结论。

时移非正交频分复用及其与正交频分复用的比较

通过将时移参数引入多载波调制，形成了一种具有全新思想的时移非正交频分复用（TS-NFDM）调制技术，并通过理论分析和仿真实验将该技术的性能与当前在无线通信中扮演重要角色的正交频分复用（OFDM）技术进行了比较。比较结果表明，TS-NFDM技术具有明显的优势，其时移特性使其表现出许多优良的性能，其中最突出的是频带利用率高，约为OFDM的4．29倍，另外，信号功率的峰值均值比也明显低于OFDM。

Performance Comparison of Space-Time Trellis Codes and Space-Time Transmit Diversity under the Same Bandwidth Efficiency

Space time coding can provide high data rate and performance gain for wireless communication system. Performance comparison of space time trellis codes and space time transmit diversity is carried out under the same bandwidth efficiency in this paper. We also propose some optimum low rate space time trellis codes in quasi static Rayleigh fading chan￣nel. Performance analysis and simulation show that the low rate space time trellis codes outperform space time transmit diversity at the same bandwidth efficiency, and are more suitable for the power limited wireless communication system which has no strict requirement on bandwidth efficiency.

Tree-Structured Parallel Regeneration for Multiple Data Losses in Distributed Storage Systems Based on Erasure Codes

To reduce the time required to complete the regeneration process of erasure codes, we propose a Tree-structured Parallel Regeneration (TPR) scheme for multiple data losses in distributed storage systems. Under the scheme, two algorithms are proposed for the construction of multiple regeneration trees, namely the edge-disjoint algorithm and edge-sharing algorithm. The edge-disjoint algorithm constructs multiple independent trees, and is simple and appropriate for environments where newcomers and their providers are distributed over a large area and have few intersections. The edge-sharing algorithm constructs multiple trees that compete to utilize the bandwidth, and make a better utilization of the bandwidth, although it needs to measure the available band-width and deal with the bandwidth changes; it is therefore difficult to implement in practical systems. The parallel regeneration for multiple data losses of TPR primarily includes two optimizations: firstly, transferring the data through the bandwidth optimized-paths in a pipe-line manner; secondly, executing data regeneration over multiple trees in parallel. To evaluate the proposal, we implement an event-based simulator and make a detailed comparison with some popular regeneration methods. The quantitative comparison results show that the use of TPR employing either the edge-disjoint algorithm or edge-sharing algorithm reduces the regeneration time significantly.

A Novel Optical Burst Mesh Network with Optical Time Slot Interchange at Source Nodes

In this paper, we propose an optical burst network architecture supporting the ge- netic mesh topology. The intermediate node architecture of the mesh network can be the same with current wavelength switching Wave- length Division Multiplexing （WDM） net- works, and thus can reuse existing deployed infrastructure. We employ a novel Optical Time Slot Interchange （OTSI） at the source nodes for the first time to mitigate the burst conten- tion and to increase the bandwidth utilization. Time- and wavelength-domain reuse in the OTSI significantly saves optical components and red- uces blocking probability.

Survivable Traffic Cognition Algorithm with Joint Failure Probability in Flexible Bandwidth Optical Networks

This paper addresses the problem of survivable traffic assignment with failure probability requirement in flexible bandwidth optical networks. We describe a Survivable Traffic Cognition (STC) algorithm with joint failure probability. Survivable Traffic Assignment (STA) algorithm and Conventional Traffic Assignment (CTA) algorithm are added to illustrate the effectiveness of our proposed STC. We investigate the effect of joint failure probability on blocking probability, spectral utilization ratio, average joint failure probability, and the average hops. Simulation results show that our proposed STC not only achieves better performance in terms of blocking probability and spectral utilization ratio than CTA and STA, but also does not cause higher average joint failure probability or larger average hops compared with STA. As a result, STC makes the best use of spectral resources and does not cause large average joint failure probability.

Fair Data Collection Scheme in Wireless Sensor Networks

To solve the slow congestion detection and rate convergence problems in the existing rate control based fair data collection schemes, a new fair data collection scheme is proposed, which is named the improved scheme with fairness or ISWF for short. In ISWF, a quick congestion detection method, which combines the queue length with traffic changes of a node, is used to solve the slow congestion detection problem, and a new solution, which adjusts the rate of sending data of a node by monitoring the channel utilization rate, is used to solve the slow convergence problem. At the same time, the probability selection method is used in ISWF to achieve the fairness of channel bandwidth utilization. Experiment and simulation results show that ISWF can effectively reduce the reaction time in detecting congestion and shorten the rate convergence process. Compared with the existing tree-based fair data collection schemes, ISWF can achieve better fairness in data collection and reduce the transmission delay effectively, and at the same time, it can increase the average network throughput by 9.1% or more.

A Dynamic Bandwidth Allocation Solution Based on User Behavior and Software Defined EPS

For telecommunication operators, how to improve the utilization of bandwidth resources is always a problem which worthy of study, nowadays, this issue has become more and more important, since the traffic load bursting in the mobile Internet. So the key to solving this problem is that we need to find a kind of traffic model to predict the traffic load that users need. According to the predicted traffic load to allocate bandwidth to each base station dynamically.But the traffic consumption behavior of a single base station is random, it is difficult to predict[ 1 ]. For this reason, we based on reality that, when the user moves, it may get traffic load from different base stations, therefore, there will have some kind of relationship between those base stations.We use this relationship to establish a kind of Spatial Collaborative Network.consequently, we make use of stability algorithm to divided those base station cluster into different communities, According to the traffic load usage rules which these communities indicated to us, we get a traffic model.At the same time, we studied bow to use this traffic model in the future networks to dynamically allocate bandwidth resources, then we propose a new kind of EPS architecture based on SDN, on this platform, we can deploy our strategy through it＇s programmable interface.Finally, we designed an experiment to test the performance of our dynamic strategy, and the result shows that our method enables bandwidth utilization has been greatly improved.

Green Multicast Grooming Based on Cross-Shared Protection in Optical WDM Networks

Currently,multicast survivability in optical network obtains more attention.This paper focuses on the field of multicast grooming shared protection in green optical network and designs a novel auxiliary graph and a shared matrix to address the survivable multicast resource consumption.This paper also proposes a new heuristic called Green Multicast Grooming algorithm based on spanning path Cross-Shared protection(GMGCSP),in which network reliability,energy efficiency and resource utilization are jointly considered.Simulation results testify that,compared to other algorithms,the proposed GMG-CSP not only has lower blocking probability and higher bandwidth utilization ratio,but also saves more energy.

Supplemental Effects of Zinc Oxide on the Utilization of Cassava Plant Meal by Growing Pigs in the Humid Tropics

The objective of this study was to evaluate the effects of zinc oxide （ZnO） as an additive on cassava plant meal through the growth, serum metabolites and heamatological indices of growing pigs for eight weeks. Four experimental diets were formulated in this study. All the four diets contained 60% cassava plant meal. Diet 1 contained 0 ppm of ZnO, while diets 2, 3 and 4 contained 125, 250 and 300 ppm of ZnO, respectively. The cassava plant meal contained unpeeled tuber plus leaves and tender stems. The unpeeled cassava tuber was mixed with leaves and tender stem at ratio 2.5：1, while the ratio of the leaves and tender stem was 5：1. A total of 16 growing pigs （Large White x Hampshire） with initial mean weight of 24.92 - 0.37 kg were used in this study. They were randomly distributed into the four experimental diets formulated. There were four animals per diet and each animal served as a replicate. The diets were formulated to contain about 19% crude protein and 2.5 kcal/g metabolizable energy. This experiment was completely randomized designed. The results of this study showed that weight gain, feed intake and feed conversion ratio were not significantly （P 〉 0.05） affected by the inclusion of ZnO, although numerically 250 ppm gave the better values. The serum metabolites, such as the total protein, albumin, urea and cholesterol, were not significantly （P 〉 0.05） affected by the inclusion of ZnO. However, the serum creatinine and glucose were significantly （P 〈 0.05） affected. Moreover, haematological indices, such as the packed cell volume （PCV）, haemoglobin （FIB） and red blood cell （RBC）, were not significantly （P 〉 0.05） affected by the inclusion of ZnO; while the white blood cell （WBC） was significantly （P 〈 0.05） affected. It can be concluded from this study that ZnO could be used as an additive to improve the utilization of cassava plant meal by growing pigs.

Positive adaptation of Salix eriostachya to warming in the treeline ecotone,East Tibetan Plateau

Understanding of treeline ecotone ecophysiological adaptation to climate warming is still very limited. Furthermore, it is difficult to predict which plant species could dominate in the future. For this reason, a study was conducted in the treeline ecotone, East Tibetan Plateau to detect the adaptation of the dwarf willow(Salix eriostachya) to experimental warming. Compared to ambient conditions, the experimental warming advanced the bud break by 12 days, delayed the leaf abscission by20 days, and prolonged the growing period by 28 days.It also increased photosynthesis(47%), number of leaves(333%), leaf area(310%), and carbon sequestration of the dwarf willow. Experimental warming did not affect carbon use efficiency, but decreased water use efficiency significantly.Experimental warming enhanced the clonal ramets of Salix eriostachya(+ 3.7 shrubs m-2). The frequent air temperature fluctuations had minor effect on Salix eriostachya. Based on these findings, we highlighted that Salix eriostachya could dominate in the community treeline ecotone of east Tibetan Plateau in the future climate warming scenario.

静态波带交换中的一种波带粒度取值算法

波带交换可以有效地减少波长交换的交换端口数量,本文研究节点间业务量已知时静态波带交换中的波带粒度取值算法,提出了基于k均值聚类的波带粒度取值算法。算法将业务量相近的业务分为一组,一组内的业务用相同粒度的波带装载,以提高波带的利用率。研究表明,在没有业务疏导的环境下,与其他方法相比,算法使用的波带数量和波带内的空闲波长数量都比较少。本文还研究了静态疏导环境下不同波带粒度取值算法的性能,提出了多波带粒度下的业务装载策略。对于大粒度的波带,使用向下装载,而对于小粒度的波带,使用向上装载,意在减少波带的使用数量的同时提高波带利用率。仿真结果表明,使用静态业务疏导后,本文算法与其他方法相比,依然可以有效地减少波带数量,提高波带利用率。与基于组播路由的静态波带疏导算法相结合,使波带利用率可以达到98%以上。

Effects of Different Biochars on Pinus elliottii Growth,N Use Efficiency,Soil N_2O and CH_4 Emissions and C Storage in a Subtropical Area of China

Intensive management of planted forests may result in soil degradation and decline in timber yield with successive rotations. Biochars may be beneficial for plant production, nutrient uptake and greenhouse gas mitigation. Biochar properties vary widely and are known to be highly dependent on feedstocks, but their effects on planted forest ecosystem are elusive. This study investigated the effects of chicken manure biochar, sawdust biochar and their feedstocks on 2-year-old Pinus elliottii growth, fertilizer N use efficiency （NUE）, soil N20 and CH4 emissions, and C storage in an acidic forest soil in a subtropical area of China for one year. The soil was mixed with materials in a total of 8 treatments： non-amended control （CK）; sawdust at 2.16 kg m^-2 （SD）; chicken manure at 1.26 kg m^-2 （CM）; sawdust biochar at 2.4 kg m^-2 （SDB）; chicken manure biochar at 2.4 kg m^-2 （CMB）; 15N-fertilizer alone （10.23 atom% 15N） （NF）; sawdust biochar at 2.4 kg m^-2 plus lSN-fertilizer （SDBN） and chicken manure biochar at 2.4 kg m^-2 plus 15N-fertilizer （CMBN）. Results showed that the CMB treatment increased P. elliottii net primary production （aboveground biomass plus litterfall） and annual net C fixation （ANCF） by about 180% and 157%, respectively, while the the SDB treatment had little effect on P. eUiottii growth. The 15N stable isotope labelling technique revealed that fertilizer NUE was 22.7% in CK, 25.5% in the NF treatment, and 37.0% in the CMB treatment. Chicken manure biochar significantly increased soil pH, total N, total P, total K, available P and available K. Only 2% of the N in chicken manure biochar was available to the tree. The soil N20 emission and CH4 uptake showed no significant differences among the treatments. The apparent C losses from the SD and CM treatments were 35% and 61%, respectively; while those from the CMB and SDB treatments were negligible. These demonstrated that it is crucial to consider biochar properties while evaluating their effects on plant growth and C sequestration.

Experimental evidence for weakened tree nutrient use and resorption efficiencies under severe drought in a subtropical monsoon forest

Aims The functions of global forests are threatened by the increasing frequency of severe drought.Due to drought inducing reductions in soil nutrient availability,efficiencies of nutrient use and resorption of trees become crucial for forest functions and biogeochemical cycles.However,understanding the dynamics of responses of foliar nutrient use and resorption efficiencies to drought,especially in tropical or subtropical forests,is still limited.Our goal was to detect whether and how the importance of leaf nutrient use and resorption changes across different species in the hot and wet forests when suffering drought stress in different months.Methods Based on a 70%throughfall exclusion experiment in a subtropical forest,we collected green and senesced leaves of Schima superba and Lithocarpus glaber in different months from October 2016 to May 2019,to estimate the effects of drought on leaf nitrogen(N)and phosphorus(P)use and resorption efficiencies(i.e.NUE and PUE,NRE and PRE).Important Findings The effects of drought on nutrient use and resorption efficiencies varied between species and months.Based on a 2-year observation,drought had no effect on S.superba,but significantly decreased NUE,NRE and PRE of L.glaber by 3.4%,20.2%and 7.1%,respectively.Furthermore,the negative drought effects were aggravated by the natural summer drying in 2017.As a result,NUE and PUE of L.glaber were significantly depressed by 17.2%and 58.1%,while NRE and PRE were significantly reduced by 56.5%and 53.8%in August 2017.Moreover,the responses of NRE,PRE and NUE to drought were related with soil moisture(SM)for L.glaber,and when SM decreased to a threshold near 9 v/v%,drought effects were shifted from unresponsive to negative.Our results highlight a species-specific threshold response of nutrient use under drought in a subtropical forest.

Remote Sensing Indices to Measure the Seasonal Dynamics of Photosynthesis in a Southern China Subtropical Evergreen Forest

The accurate measurement of the dynamics of photosynthesis in China’s subtropical evergreen forest ecosystems is an important contribution to carbon(C) sink estimates in global terrestrial ecosystems and their responses to climate change. Eddy covariance has historically been the only direct method to assess C flux of whole ecosystems with high temporal resolution, but it suffers from limited spatial resolution. During the last decade, continuous global monitoring of plant primary productivity from spectroradiometer sensors on flux towers and satellites has extended the temporal and spatial coverage of C flux observations. In this study, we evaluated the performance of two physiological remote sensing indices, fluorescence reflectance index(FRI) and photochemical reflectance index(PRI), to measure the seasonal variations of photosynthesis in a subtropical evergreen forest ecosystem using continuous canopy spectral and flux measurements in the Dinghushan Nature Reserve in southern China.The more commonly used NDVI has been shown to be saturated and mainly affected by illumination(R^2=0.88, p <0.001), but FRI and PRI could better track the seasonal dynamics of plant photosynthetic functioning by comparison and are less affected by illumination(R^2=0.13 and R^2=0.51, respectively) at the seasonal scale. FRI correlated better with daily gross primary production(GPP) in the morning hours than in the afternoon hours, in contrast to PRI which correlated better with light-use efficiency(LUE) in the afternoon hours. Both FRI and PRI could show greater correlations with GPP and LUE respectively in the senescence season than in the recovery-growth season. When incident PAR was taken into account, the relationship between GPP and FRI was improved and the correlation coefficient increased from 0.22 to 0.69(p < 0.001). The strength of the correlation increased significantly in the senescence season(R^2=0.79, p < 0.001). Our results demonstrate the application of FRI and PRI as physiological indices for the accurate measurement of the seasonal dynamics of plant community photosynthesis in a subtropical evergreen forest, and suggest these indices may be applied to carbon cycle models to improve the estimation of regional carbon budgets.

FUZZY-BASED NETWORK BANDWIDTH DESIGN UNDER DEMAND UNCERTAINTY

In communication networks （CNs）, the uncertainty is caused by the dynamic nature of the traffic demands. Therefore there is a need to incorporate the uncertainty into the network bandwidth capacity design. For this purpose, this paper developed a fuzzy methodology for network bandwidth design under demand uncertainty. This methodology is usually used for offiine traffic engineering optimization, which takes a centralized view of bandwidth design, resource utilization, and performance evaluation. In this proposed methodology, uncertain traffic demands are first handled into a fuzzy number via a fuzzification method. Then a fuzzy optimization model for the network bandwidth allocation problem is formulated with the consideration of the trade-off between resource utilization and network performance. Accordingly, the optimal network bandwidth capacity can be obtained by maximizing network revenue in CNs. Finally, an illustrative numerical example is presented for the purpose of verification.