海外社交平台中国媒体国际传播能力建构——基于推特账号@ChinaDaily“一带一路”报道网络议程设置效果分析

对中国日报推特账号@ChinaDaily“一带一路”报道(2019~2021年)进行网络议程设置效果分析以寻求国际传播能力构建启示。研究发现,相关报道议题网络中的政治、经济和文化议题与其他议题类型共现频次最高,政治与经济、政治与文化、文化与艺术三组议题表现出强关联性;个人用户推文议题网络中,经济、政治和文化议题与其他类议题关联频次居前三,各类议题组合更加灵活自由;三年中@ChinaDaily“一带一路”报道议题网络对公众议题网络总体影响较明显,呈现下降后回升趋势。中国媒体在重大主题传播中应树立议题关联意识,利用议题竞合关系,高峰传播与常态传播相结合,追求以公众认同为目标的议题传播效能。

Self-calibrating microring synapse with dual-wavelength synchronization

As a resonator-based optical hardware in analog optical computing, a microring synapse can be straightforwardly configured to simulate the connection weights between neurons, but it faces challenges in precision and stability due to cross talk and environmental perturbations. Here, we propose and demonstrate a self-calibration scheme with dual-wavelength synchronization to monitor and calibrate the synaptic weights without interrupting the computation tasks. We design and fabricate an integrated 4 × 4 microring synapse and deploy our self-calibration scheme to validate its effectiveness. The precision and robustness are evaluated in the experiments with favorable performance, achieving 2-bit precision improvement and excellent robustness to environmental temperature fluctuations(the weights can be corrected within 1 s after temperature changes 0.5°C). Moreover, we demonstrate matrix inversion tasks based on Newton iterations beyond 7-bit precision using this microring synapse. Our scheme provides an accurate and real-time weight calibration independently parallel from computations and opens up new perspectives for precision boost solutions to large-scale analog optical computing.

后香农时代ICT领域的十大挑战问题

本文以未来万物互联的智能社会的愿景为出发点,从信息产生、传输和处理的角度,深入剖析信息通信(information and communications technologies,ICT)行业在信息论、运筹学、控制论、计算理论和人工智能方面未来发展中面临的技术挑战,并提出十个重要挑战问题.文章首先详细阐述这些技术挑战问题的背景、问题定义以及学术界和工业界当前的研究进展.其次针对这些问题给出潜在的解决思路和未来的研究方向.最后提出要解决十大挑战难题所面临的理论突破机会,包括:需要超越经典的香农信息论,建立语义信息论体系;需要突破深度神经网络,建立可解释的深度神经网络理论体系;需要突破经典的排队论和优化理论体系,建立网络排队论和网络优化理论方法;需要突破功耗和复杂度的约束,建立近似计算理论体系.

Evaluation of spatial and temporal patterns of insect damage and aflatoxin level in the pre-harvest corn fields to improve management tactics

Spatial and temporal patterns of insect damage in relation to aflatoxin contamination in a corn field with plants of uniform genetic background are not well understood. After previous examination of spatial patterns of insect damage and aflatoxin in pre-harvest corn fields, we further examined both spatial and temporal patterns of cob- and kernel- feeding insect damage, and aflatoxin level with two samplings at pre-harvest in 2008 and 2009. The feeding damage by each of the ear/kernel-feeding insects （i.e., corn earworm/fall armyworm damage on the silk/cob, and discoloration of corn kernels by stink bugs） and maize weevil population were assessed at each grid point with five ears. Sampling data showed a field edge effect in both insect damage and aflatoxin contamination in both years. Maize weevils tended toward an aggregated distribution more frequently than either corn earworm or stink bug damage in both years. The frequency of detecting aggregated distribution for aflatoxin level was less than any of the insect damage assessments. Stink bug damage and maize weevil number were more closely associated with aflatoxin level than was corn earworm damage. In addition, the indices of spatial-temporal association （χ） demonstrated that the number of maize weevils was associated between the first （4 weeks pre-harvest） and second （1 week pre-harvest） samplings in both years on all fields. In contrast, corn earworm damage between the first and second samplings from the field on the Belflower Farm, and aflatoxin level and corn earworm damage from the field on the Lang Farm were dissociated in 2009.

Evaluation of fall armyworm resistance in maize germplasm lines using visual leaf injury rating and predator survey

After examining ear-colonizing pest resistance, 20 maize lines from the USDA- ARS Germplasm Enhancement of Maize （GEM） Program were evaluated for whorl-feeding fall armyworm （FAW） （Spodopterafrugiperda） resistance using 4 maize inbred lines as the resistant and susceptible controls. Both FAW injury ratings at 7- and 14-d after infestation, and predator abundance and diversity at whorl stage （V6-V8） were recorded in 2009 and 2010. The survey of the diversity and abundance of predators in each experimental plot were conducted 7 d after the FAW infestation. Of the 20 germplasm lines examined, 3 of them （i.e., entries 9, 15, and 19 that were derived from tropical maize germplasm lines were originated from Uruguay, Cuba, and Thailand, respectively） were identified as the best FAW-resistant germplasm lines using the leaf injury ratings and predator survey data. In addition, the abundance and diversity of the predators were greater in 2010 than in 2009, which might have caused the low level of the FAW injury ratings on all lines examined in 2010. The 2-year data showed that the FAW injury ratings were negatively correlated to the predator abundance and diversity, which is also influence by genotype × environment interactions. The findings suggested that tropical germplasm is an important source of native resistance to the FAW and the corn earworm. At the same time, the maize genotype x environment interaction （e.g., predator attractiveness, and varying weather conditions） should be included in the multiple-year evaluations of insect and disease resistance of maize germplasm lines under field conditions.

Synthesis and Evaluation of the Analogues of Penicillide against Cholesterol Ester Transfer Protein

A series ofpenicillide analogues, with modifications at C-3 and C-9 positions, are synthesized as potential cho-lesteryl ester transfer protein （CETP） inhibitors. The preliminary in vitro inhibition assay provided some valuable structure-activity relationship information about penicillide.

Integrated pest management is the lucrative bridge connecting the ever emerging knowledge islands of genetics and ecology

Integrated pest management （IPM） has long been considered a profit- and product （or technology）-driven multidisciplinary research field that maximizes crop yield and minimizes pest-inflicted economic losses. The introduction of transgenic crops has revolutionized crop protection and IPM by combining crop protection and genetics into one entity-the seed. Before the arrival of transgenic technology, studies of insect-plant interactions were frequently categorized under the field of ecology, and IPM programs were then the product of applied ecological research on suppressing pest populations in crop or livestock production.