一种嵌入式软件无线电频谱监测系统

为了降低研发成本，提高频谱系统的灵活性和缩短研制周期，提出了一种基于软件无线电的嵌入式频谱监测系统。首先研究了系统硬件平台组成和特点，在此基础上设计了一种灵活的软件定义系统架构；然后考虑到硬件平台自身性能的限制，重点研究了频率偏移校正、频谱扫描策略等关键技术，分别提出了基于GSM信号和温度传感器的频偏校正方法和基于相关性的扫频策略；最后通过具体实验，对系统性能进行验证与评估，结果表明所提出的频偏校正方法能够将绝对平均频偏控制在1.749×10-6以内，所设计的基于相关性的扫频策略对时变信号的频谱监测效果最好。     

基于图论的认知无线网络频谱动态分配

在认知无线电网络中，图论与量子遗传算法相结合的频谱分配策略能够提高频谱利用率，但存在早熟和收敛精度不够等缺点。为了解决该问题而实现算法的优化，对图着色理论的频谱分配模型进行数学建模，并针对该模型提出了改进的量子遗传算法。首先，通过使用小生境技术初始化种群，使种群分布更加广泛、算法的收敛度更高；其次，根据进化代数对量子旋转角进行实时动态调整，对染色体进行阈值变异，防止个体陷入早熟，跳出局部解；然后，对干扰约束条件进行重新设计，有效地避免盲目性，提高了网络的公平性和网络效益。仿真结果表明，所提算法有效地提高了频谱利用率，极大地增强了网络系统的性能。     

高管过度自信、研发投入跳跃与企业绩效——来自中国上市公司的经验证据

基于间断平衡理论和高阶梯队理论，以2007-2017年中国沪深两市902家制造企业为样本，实证分析研发投入跳跃对企业绩效的影响以及高管过度自信的调节作用。结果显示：研发投入正向跳跃和负向跳跃均有助于提升企业绩效，高管过度自信正向调节研发投入跳跃与企业绩效间的关系。引入高管过度自信这一重要高管特征作为调节变量，有助于重新认识管理者心理偏差对企业创新行为和绩效的影响，较好地弥补了研发投入跳跃对企业绩效影响机制的研究空缺，丰富了创新间断平衡理论研究。研究表明，企业应重视高管心理特征的影响并结合自身实际情况，合理选择研发投入策略以改善企业绩效。     

不同模式农地整治前后农户收入流动性研究*——以江汉平原和鄂西南山区部分县市为例

[目的]考察农地整治前后农户的收入流动性,并分析不同模式的农地整治对农户收入流动性的影响差异。[方法]运用双重差分模型探讨不同农地整治模式下农户收入流动性差异。[结果](1)农地整治对农户收入流动性具有显著正向影响,在实施农地整治后农户收入有明显的"上升"流动趋势;(2)新型农业经营主体主导的农地整治模式对农户收入流动性具有显著正向影响;(3)农户家庭劳动力规模、农地经营面积和非农收入占比对农户收入提升具有显著的正向影响,农户收入初始位置对收入流动性具有显著的负向影响。[结论]农地整治可增加农户收入,促进农户收入向上流动;相对于政府主导模式的农地整治而言,新型农业经营主体主导模式对农户收入的提升作用更大。因此,应进一步推进农地整治,深化改革政府主导模式的农地整治项目管理体制,大力创新农地整治模式,鼓励新型农业经营主体参与农地整治,为稳步提升农户收入创造条件。     

高效液相色谱法同时测定食用油中7种抗氧化剂的方法研究

本研究利用高效液相色谱同时测定食用油中没食子酸丙酯(PG)、没食子酸月桂酯(DG)、没食子酸辛酯(OG)、叔丁基对苯二酚(TBHQ)、叔丁基对羟基茴香醚(BHA)、2,6-二叔丁基对甲基苯酚(BHT)、2,6-二叔丁基-4-羟甲基苯酚(Ionox-100)7种抗氧化剂的测定方法,样品中的抗氧化剂经正己烷溶解、乙腈萃取后,经C18柱分离,乙腈-1.5%乙酸溶液体系为流动相进行梯度洗脱,紫外检测器检测,外标法定量。选择线性范围在1~100mg/L,结果表明7种抗氧化剂呈良好的线性关系,相关系数r大于0.999,方法的测定低限为0.8~2.0mg/kg,回收率在89.3%~110.1%,变异系数在1.5%~4.9%。该方法准确、快速、重现性好,可用于大批量食用油检测中7种抗氧化剂的定量分析。     

农户生态耕种行为及其影响因素研究——以江西省为例

[目的]为清晰识别影响农户生态耕种行为的主要因素,以期为加强耕地生态保护、保障农作物质量安全、提升农户耕种收益、实现农业现代化目标提供参考。[方法]基于江西省11市47县(区)1488份农户微观调查数据,在分析农户生态耕种特征基础上,运用二元Logistic和Probit模型对农户生态耕种行为影响因素开展实证研究。[结果]农户生态耕种10种具体行为的采纳情况差异明显,其中施用有机肥采纳程度最高,生态农业模式采纳程度最低。农户采纳生态耕种整体水平不高,但仍具备进一步推广的潜力。家庭劳动力比重、生态耕种成本认知、新型农业经营主体、法律法规认知、生态耕种收益认知、生计分化和生态环境认知等解释变量是影响农户生态耕种行为的主要内部因素,政府补贴、农田基础设施、生产交流程度、耕地质量变化和生态耕种信息获取难度等则是主要的外部影响因素。[结论]政府及基层管理部门应在推动农户非农就业生计、大力培育新型农业经营主体、加强生态耕种宣传与推广、完善政策扶持与管控机制等方面制定针对性的政策措施。     

汇水系统绿地雨洪调蓄研究——以武汉港西汇水系统为例

绿地有一定的雨洪调蓄功能，雨洪状况下，如何在汇水系统尺度利用和保护绿地亟待研究。选取95处位于武汉港西汇水系统的地块，调研地块性质，利用ArcGIS提取不透水比例及平均坡度，并进行SWMM水文模型演算。通过实验性模拟结果的对比，得出汇水系统的绿地雨洪调蓄效率(λ＝0.13m3/m2)、汇水系统(g＝36%)和各类用地(g＝18%～47%)基于雨水调蓄理念下的最低绿地率，使汇水系统水文状况达到海绵城市建设标准。讨论了不同重现期下汇水系统的绿地雨洪调蓄效能，旨在完善绿地雨洪调蓄的研究方法、指标体系及利用与保护策略，为相关研究与实践提供借鉴。     

Is the Best Interest of the Child Best for Children? Educational Attainment and Child Custody Assignment

Between the 1970s and 1990s, state custody laws moved from maternal preference to the “best interests of the child” doctrine, which gives fathers and mothers equal treatment in child custody assignment. We exploit exogenous variation across states in the timing of this custody law change to estimate the long-term implications of exposure to a gender-neutral custody law regime. We find that childhood exposure to gender neutral custody laws has a negative effect on educational attainment. A child exposed to gender neutral custody law is less likely to graduate from high school by 1.5 to 2.0 percentage points.     

The effect of corporate real estate ownership on R&D innovation: credit relief vs. resource replacement in China

Against the background of supply-side structural reform and the real estate financialisation in China, this study investigates the impact of real estate holdings on R&D investment using data of enterprises listed on the Shanghai and Shenzhen stock exchanges. Our empirical results yield five main findings. First, enterprises holding more real estate assets face more serious financial constraints, thus restraining corporate innovation efficiency. Second, when the profit margin gap between entity enterprises and the real estate industry is larger, enterprises are more inclined to transfer industrial capital into the real estate industry, thus reducing R&D investment. Third, when the degree of marketisation is high, intensified market competition, the optimal allocation of factor and product markets, and stronger patent protection will weaken the restraining effect of corporate real estate holdings on R&D investment. Fourth, monopoly enterprises obtain potential profits more than undertaking risks from the real estate industry, they are more willing to hold real estate, thus strengthening the restraining effect of real estate holdings on innovation. Finally, investors' regional preference intensifies the restraining effect of corporate real estate holdings on R&D investment. Our empirical evidence can guide entity enterprises on how to effectively balance short-term (non-productive) and long-term (productive) capital investment.     

The impact of dual network structure on firm performance: the moderating effect of innovation strategy

ABSTRACT

Firm innovation is embedded in a collaboration network among researchers and a knowledge network composed of knowledge elements; the two networks are decoupled. Guided by social network theory, this study puts forward the definition and the classification of firm dual network structure, probes into the influence of dual network structure on firm performance, and explores the alignment between innovation strategy and firm dual network structure. We conduct an empirical study of 183 listed companies in China from 2004 to 2018. It is found that the four types of dual network structure all have positive impacts on firm performance, and the impact of a collaboration network is slightly higher than that of a knowledge network. Besides, innovation strategy plays a positive moderating role in the relationship between dual network structure and firm performance. Our findings provide new ideas for firms to identify and optimise knowledge and collaboration network structures and match them with innovation strategy to improve performance.