Gliricidia sepium Carbon Inputs and Soil Carbon Pools in a Costa Rican Alley Cropping System

Alternative land management practices, including agroforestry, help to maintain levels of soil organic matter (SOM) and can facilitate soil carbon (C) sequestration for mitigating atmospheric CO₂ emissions. This study quantified C inputs and determined the changes of the soil C pool in a 19-year-old Gliricidia sepium alley cropping system, studied at two fertiliser levels (tree prunings only [? N], and tree prunings plus chicken manure [+ N]), and was compared to a sole crop system. Carbon input from tree prunings ranged from 455 to 457 g C m^{? 2} y^{? 1}, whereas C inputs from crop residues were similar between alley- and sole crops ranging from 121 to 159 g C m^{? 2}y^{? 1}. The soil organic C (SOC) pool in the alley crop was 16–23% higher than the sole crop. In the 19th year of alley farming, SOC was significantly higher (p < 0.05) in the alley crop (3.2%) compared to the sole crop (2.4%), and was also greater compared to that at the time of establishment of the agroforestry system (2.8%). Gross SOC turnover to a 20-cm depth ranged from 12 to 14 years in the + N and ?N alley crops compared to 49 and 50 years in the + N and ?N treatments for the sole crops. Residue stabilisation efficiency in the alley crops was 39% and 55% in + N and ?N treatments respectively.     

Is external research assessment associated with convergence or divergence of research quality across universities and disciplines? Evidence from the PBRF process in New Zealand

ABSTRACT

Performance-based research evaluations have been adopted in several countries both to measure research quality in higher education institutions and as a basis for the allocation of funding across institutions. Much attention has been given to evaluating whether such schemes have increased the quality and quantity of research. This paper examines whether the introduction of the New Zealand Performance-Based Research Fund process produced convergence or divergence in measured research quality across universities and disciplines between the 2003 and 2012 assessments. Two convergence measures are obtained. One, referred to as β-convergence, relates to the relationship between changes in average quality and the initial quality level. The second concept, referred to as σ-convergence, relates to the changes in the dispersion in average research quality over time. Average quality scores by discipline and university were obtained from individual researcher data, revealing substantial β- and σ-convergence in research quality over the period. The hypothesis of uniform rates of convergence across almost all universities and disciplines is supported. The results provide insights into the incentives created by performance-based funding schemes.     

Overcoming the barriers to successful implementation of information technology in the U.K. hotel industry

This article examines the organisational barriers to successful implementation of information technology in the hotel industry. These are barriers of will, ability, and finance which block the routes to integration of internal systems.     

基于周期的低轨预警系统任务动态重规划策略

根据预警系统资源的特点和导弹跟踪任务的实时性和不确定性,天基低轨预警系统 任务规划具有动态性的特点。为解决低轨系统动态任务规划问题,提出了低轨预警系统动态 任务规划模式,分析了周期重规划调度策略,探讨了系统动态重规划中重规划周期的确 定方法,并对其中的弹道预测误差椭球和双星定位精度两个关键问题进行了建模,为动态问 题建模求解提供基础。     

双星时差频差无源定位系统定位算法工程指标分析

通过计算时差、频差测量精度,以及卫星运动引起的时差、频差变化率,提出双星时差频 差无源定位系统的信号最佳采样时间为10～100 ms。进一步推导了工程可实现的定位精 度,仿真结果表明双星系统工程可实现的定位精度约为1～3 km。研究和结论对双 星定位系统定位精度指标的论证与分解具有借鉴意义。     

PCMA自适应自干扰对消算法与仿真

讨论了成对载波多址（PCMA）自适应自干扰对消原理,分析了参数估计误差对自干扰 对消的影响。在频偏误差的影响下对消误差为非平稳过程,传统自适应对消滤波器无法收敛 。为了克服频偏误差的影响,提出了一种自适应可变遗忘因子（VFF） RLS算法,同时,给 出了具有高精度低运算量的模糊函数参数估计算法。仿真证明了VFF-RLS对消算法具有良好 的对消性能和稳健性,且需要的额外功率较低,能满足PCMA系统要求。     

直升机卫星通信系统信道模拟与通信实现

针对直升机卫星通信系统中直升机旋翼对通信信道造成的周期性衰落问题,采用射频收发器AD9361模拟了信道周期性衰落模型,基于此模型在现场可编程门阵列(Field Programmable Gate Array,FPGA)上优化并实现了缝隙检测算法。根据信道衰落模型和缝隙检测算法及数据链路速率和带宽的要求,提出了一套直升机卫星通信系统可靠通信方案,即前向链路采用重发和分集接收及短码LDPC编码技术,返向链路根据前向链路缝隙检测的结果在无遮挡缝隙采用突发通信和长码低密度奇偶校验(Low Density Parity Check,LDPC)编码技术,实现可靠通信。系统测试结果表明,该方案不受直升机机型限制,系统可在40%遮挡率下实现前向链路25.6 kb/s和返向链路4 Mb/s速率下的可靠通信。     

“双碳”目标背景下全域土地综合整治减排增汇的 机理与路径研究

研究目的：剖析“双碳”目标与全域土地综合整治的互馈关系,解析全域土地综合整治减排增汇的内涵特征、机理和路径,为“双碳”目标背景下全域土地综合整治规划和实施方案的优化提供科技支撑。研究方法：文献资料法和归纳演绎法。研究结果：（1）“双碳”目标赋予了全域土地综合整治减排增汇的新时代生态要义,而全域土地综合整治可以赋能“双碳”目标的实现,二者具有相辅相成的互馈关系。（2）全域土地综合整治系统内涵体现为通过培育多元主体低碳理念,在低碳化整治工程的基础上,优化国土空间碳源/碳汇格局,推动产业活动低碳转型。（3）全域土地综合整治减排增汇过程形成了多要素综合作用的“外缘—内核式”复杂系统,“社会—经济—生态”外缘系统发挥支撑和约束作用,内核系统实现“人—地—业”的协同发展,外缘内核之间双轮耦合,系统推进。（4）最后通过强化“双碳”目标在“社会—经济—生态”外缘系统中的约束作用,构建 “人—地—业”内核系统的减排增汇实施路径。研究结论：全域土地综合整治的减排增汇路径探索是响应“双碳”目标的时代所趋,需要结合内外部环境统筹推进,破解乡村系统实现“双碳”目标的现实压力,助推美丽乡村和生态文明建设。     

论发展中国家复杂产品技术能力发展阶段的划分

在对已有的技术能力发展阶段理论评述的基础上,提出以自主知识产权的产品开发平台作为复杂产品技术能力发展阶段划分的标志,将复杂产品技术能力的发展过程分为"起步-自立追赶-领先"三个阶段,并阐明了这种阶段划分的实践意义。     

公共财政框架下的农村养老保险制度建设研究

农村养老保险规定和完善着公共财政的职能范围;公共财政是农村养老保险的制度依托和物质基础,财政主体的权力结构、制度的包容性、法制化决定着养老保险制度的可持续性发展。我国要实现公共财政与农村养老保险之间的制度性耦合,需要根据农村养老保险的产品属性清晰界定公共财政的职责权限,规范公共财政各主体之间的权力资源配置,吸纳多元主体,共同参与农村养老保险事业的建设。