Study of high performance Re-timing using a 40 Gb/s hybrid-integrated mach-zehnder all-optical regenerator

We experimentally show that a hybrid-integrated Mach-Zehnder switch with a high performance gate profile allows retiming of optical signals with an accuracy of 500-700fs even if the input timing jitter is increased to 3ps. © 2004 Optical Society of America.

40 Gb/s carrierless amplitude and phase modulation for low-cost optical datacommunication links

4 bps/Hz 40 Gb/s carrierless amplitude and phase (CAP) modulation is investigated for next-generation datacommunication links. The 40 Gb/s link achieves double the length of a conventional NRZ scheme, despite using a low-bandwidth source. © 2011 Optical Society of America.

Surface roughness noise prediction for silent aircraft experimental design SAX-40

Surface roughness noise is a potentially important contributor to airframe noise. In this paper, noise assessment due to surface roughness is performed for a conceptual Silent Aircraft design SAX-40 by means of a prediction model developed in previous theoretical work and validated experimentally. Estimates of three idealized test cases show that surface roughness could produce a significant noise level above that due to the trailing edge at high frequencies. Roughness height and roughness density are the two most significant parameters influencing surface roughness noise, with roughness height having the dominant effect. The ratio of roughness height to boundary-layer thickness is the relevant non-dimensional parameter and this decreases in the streamwise direction. The candidate surface roughness is selected for SAX-40 to meet an aggressive noise target and keep surface roughness noise at a negligible level. Copyright © 2008 by Yu Liu and Ann P. Dowling.

Nutrient Enhanced Coastal Ocean Productivity (NECOP). Data report: CTD and hydrographic data, R/V Pelican cruise, April 3-11, 1993

The Nutrient Enhanced Coastal Ocean Productivity (NECOP) Program is a component of NOAA's Coastal Ocean Program. The central hypothesis of this research is: Anthropogenic nutrient inputs have enhanced coastal ocean productivity with subsequent impacts on coastal ocean water quality, living resource yields, and the global marine carbon cycle. The initial study area for this program is the Mississippi/Atchafalaya River Outflow and adjacent Louisiana shelf region.

长白山自然保护区北坡森林结构、植物多样性与碳储量40余年的变化

长白山自然保护区始建于1960年，位于北坡的红松针阔叶混交林森林生态系统是我国东北地区典型温带地带性森林植被之一，面临着全球气候变化和人类干扰的双重影响。 本研究以间隔43年的野外调查数据为基础，对1963年和2006年的长白山自然保护区北坡海拔800~1700m的森林植物群落进行对比分析，得到该区域的森林结构、植物多样性与碳储量的变化特点，讨论森林动态变化与人类活动、气候变化的关系，评价长白山自然保护区的保护效果： 对长白山北坡森林沿海拔梯度的森林结构和植物多样性的分析表明：群落的整体空间格局保存完好，植物种类变化不大，乔木层的建群种的种类基本不变，植物多样性与海拔高度呈负相关关系;林下层植物多样性受小环境影响，与海拔高度无明显相关。 以红松（Pinus koraiensis）针阔混交林、红松针叶混交林和云冷杉暗针叶林三种类型为单元分别研究各森林类型的多样性变化：α多样测度选择物种丰富度、Shannon-Wiener和Pielou均匀度指数，较好体现了样地内发生的多样性变化，灌木层和草本层多样性明显下降，一些稀有种和药用物种消失，红松等原优势物种有衰退趋势，阔叶树比例增大;β多样性测度选取Cody指数，体现出海拔梯度上的植被空间格局细节变化，演替层特别是阔叶树的物种更替变化有向高海拔移动的趋势。 对森林生态系统各层次碳储量进行估算：乔木层和灌木层采用维量法，对灌木层自建生长回归方程;草本层、枯枝落叶层采取收获法;植物细根采取根钻法;土壤采取土壤深度加权法。碳密度估算结果都与前人研究结果相似。各类型植被碳库总碳密度都达到170 t/hm2，远远高于国内平均森林植被碳库密度值44.9 t/hm2。 乔木层43年来的碳储量变化都无显著性差异，但仍表现出：阔叶树种碳储量上升，特别在高海拔类型这种变化更加明显;针叶树种碳储量在暗针叶林内大幅下降;树干的碳库分配比例都有所减少，表明植被碳库正存在向不稳定性方向发展的趋势。针阔混交林和暗针叶林的土壤碳储量，与植被碳库出现相反的变化趋势，整体碳库保持在一个相对平衡的状态。 推测造成这种变化的原因是：禁止砍伐等保护措施的实施，基本保存了乔木层垂直分布格局，而气候变暖使阔叶树种比例大幅增加，采集松籽等人类生产及旅游活动对林下层植被影响破坏较大。提议加强保护区内管理力度和规划，以减缓长白山北坡森林群落的不稳定变化趋势。

40 Gbit/s optical communication system

The University of Bristol is studying the feasibility of deploying 40 Gbit/s optical time division multiplexed (OTDM) transmission networks to support new telecommunication services such the Internet and video-on-demand systems. Among the functional blocks being considered in the project are the optical pulse sources, signal multiplexers and demultiplexers, clock recovery subsystems, signal detection and dispersion accommodation methods.