检索结果-南通市图书馆

Causes of maize density loss in farmers’ fields in Northeast China

在线全文

学校读者我要写书评

暂无评论

Journal of Integrative Agriculture 2019年第8期18卷 1680-1689页

作者： ZHAO Ying-jie XING Sen ZHANG qing-song ZHANG Fu-suo ma wen-qi Key Laboratory of Plant-Soil Interactions Ministry of Education Beijing 100193 P.R.China College of Resources and Environmental Sciences China Agricultural University Beijing 100193 P.R.China College of Resources and Environmental Science Hebei Agricultural University Baoding 071001 P.R.China

Increasing plant density is an effective and important way to reduce maize yield gaps in Northeast China. However, the fact is that a significant plant density gap exists between optimum plant density and actual plant density in farmers’ *** quantify the density gap between planned planting density and final harvest plant density(HPD), we studied 60 farmers’ fields on three types of soil for three crop seasons from 2015 to 2017 by measuring their plant-plant distance, actual seedlings density(ASD), final HPD and yield. We also explored the potential causes of density loss by digging the places where the seedlings were missing for two consecutive years in 2016–2017. Results show that the three-year average HPD in farmers’ fields was 59 699 plants ha^–1, which was significantly lower than the planned density, including both the machine setting density(MSD;67 962 plants ha^–1) and theoretical plant density(TPD;67 467 plants ha^–1). No significant difference was found in HPD between years and soil types. However, for MSD and TPD, the average value in 2015 was significantly higher than that in 2016 and 2017. No significant difference between soil types was observed. Furthermore,the results from 2016 till 2017 indicated that a lack of seeds in the soil, a failure to germinate due to low-quality seeds,and a lack of seedlings breaking out of the soil due to environmental problems explained approximately 60.88, 10.33 and 28.80% of density loss, respectively. According to our survey, 63% of farmers did not know their own TPD and HPD, and 54% of farmers did not know the density loss. Therefore, we argue that farmers’ limited knowledge of density and density loss is an urgent problem that needs to be solved in maize production. These observations will be useful for determining best management practices for maize production and for providing helpful suggestions for machine improvement.

关键词： plant density maize production density loss density gap farmers’ fields

Science and Technology Backyard: A novel approach to empower smallholder farmers for sustainable intensification of agriculture in China

在线全文

学校读者我要写书评

暂无评论

Journal of Integrative Agriculture 2019年第8期18卷 1657-1666页

作者： JIAO Xiao-qiang ZHANG Hong-yan ma wen-qi WANG Chong LI Xiao-lin ZHANG Fu-suo Center for Resources Environment and Food Security Department of Plant Nutrition/Key Laboratory of Plant-Soil InteractionsMinistry of Education China Agricultural University Beijing 100193 P.R.China College of Resources and Environment Science Hebei Agricultural University Baoding 071001 P.R.China

Sustainable feeding of the growing population in China without ecological destabilization is a grand challenge. In this populous country where agriculture is dominated by smallholder farming, developing innovative technology and translating scientific knowledge into action for smallholder farmers is a crucial step in addressing this challenge. Here, we present a novel approach for technology innovation and dissemination to achieve sustainable intensification in the fields of smallholder farmers. The Science and Technology Backyard(STB) is a hub in a rural area that links knowledge with practices to promote technology innovation and exchange. In this study, the framework and functions of STB are introduced, and the key implications for sustainable intensification across millions of smallholder farmers are explicitly stated:(i) develop innovative technology based on stated demands of farmers;(ii) disseminate technology by innovative social service models though combined top-down approaches with bottom-up measures to enable smallholders in rural areas. This paper provides a perspective on transformation of small-scale agriculture toward sustainable intensification in China and useful knowledge applicable to other developing countries.

关键词： smallholder farmers sustainable intensification technology innovation technology transfer Science and Technology Backyard

Identifying the limiting factors driving the winter wheat yield gap on smallholder farms by agronomic diagnosis in North China Plain

在线全文

学校读者我要写书评

暂无评论

Journal of Integrative Agriculture 2019年第8期18卷 1701-1713页

作者： CAO Hong-zhu LI Ya-nan CHEN Guang-feng CHEN Dong-dong QU Hong-rui ma wen-qi College of Resources and Environmental Science Hebei Agricultural University Baoding 071000 P.R.China College of Resources and Environmental Sciences China Agricultural University Beijing 100193 P.R.China National Agricultural Technology Extension and Service Center Ministry of Agriculture and Rural Affairs Beijing 100125 P.R.China

North China Plain(NCP) is the primary winter wheat production region in China, characterized by smallholder farming systems. Whereas the winter wheat average yield of smallholder farmers is currently low, the yield potential and limiting factors driving the current yield gap remain unclear. Therefore, increasing the wheat yield in NCP is essential for the national food security. This study monitored wheat yield, management practices and soil nutrient data in 132 farmers’ fields of Xushui County, Baoding City, Hebei Province during 2014–2016. These data were analyzed using variance and path analysis to determine the yield gap and the contribution of yield components(i.e., spikes per hectare, grain number per spike and 1 000-grain weight) to wheat yield. Then, the limiting factors of yield components and the optimizing strategies were identified by a boundary line approach. The results showed that the attainable potential yield for winter wheat was 10 514 kg ha^–1. The yield gaps varied strongly between three yield groups(i.e., high, middle and low), which were divided by yield level and contained 44 farmers in each group, and amounted to 2 493, 1 636 and 814 kg ha^–1, respectively. For the three yield components, only spikes per hectare was significantly different(Pmanagement factors in the seeding step were the most important for affecting spikes per hectare.

关键词： yield gaps smallholder limiting factors path analysis boundary line analysis

A combined Liouville integrable hierarchy associated with a fourth-order matrix spectral problem

在线全文

学校读者我要写书评

暂无评论

Communications in Theoretical Physics 2024年第7期76卷 1-8页

作者： wen-Xiu ma Department of mathematics Zhejiang Normal UniversityJinhua 321004China Department of mathematics King Abdulaziz UniversityJeddah 21589Saudi Arabia Department of mathematics and Statistics University of South Florida TampaFL 33620-5700United States of America material Science Innovation and Modelling Department of Mathematical SciencesNorth-West UniversityMafikeng CampusMmabatho 2735South Africa

This paper aims to propose a fourth-order matrix spectral problem involving four potentials and generate an associated Liouville integrable hierarchy via the zero curvature formulation.A bi-Hamiltonian formulation is furnished by applying the trace identity and a recursion operator is explicitly worked out,which exhibits the Liouville integrability of each model in the resulting *** specific examples,consisting of novel generalized combined nonlinear Schrodinger equations and modified Korteweg-de Vries equations,are given.

关键词： integrable hierarchy Hamiltonian structure zero curvature equation Lax pair matrix spectral problem

Time-inconsistent stochastic linear-quadratic control problem with indefinite control weight costs

在线全文

学校读者我要写书评

暂无评论

Science China mathematics 2024年第1期67卷 211-236页

作者： qi Lü Bowen ma School of mathematics Sichuan UniversityChengdu 610064China

A time-inconsistent linear-quadratic optimal control problem for stochastic differential equations is *** introduce conditions where the control cost weighting matrix is possibly *** such conditions,we obtain a family of closed-loop equilibrium strategies via multi-person differential *** result extends Yong’s work(2017) in the case of stochastic differential equations,where a unique closed-loop equilibrium strategy can be derived under standard conditions(namely,the control cost weighting matrix is uniformly positive definite,and the other weighting coefficients are positive semidefinite).

关键词： linear-quadratic optimal control problem time-inconsistent cost functional generalized Riccati equation indefinite control weight cost closed-loop equilibrium strategy

Efficiently simulating the work distribution of multiple identical bosons with boson sampling

在线全文

学校读者我要写书评

暂无评论

Frontiers of physics 2024年第3期19卷 197-206页

作者： wen-qiang Liu Zhang-qi Yin Center for Quantum Technology Research and Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurements(MOE) School of PhysicsBeijing Institute of TechnologyBeijing 100081China

Boson sampling has been theoretically proposed and experimentally demonstrated to show quantum computational ***,it still lacks the deep understanding of the practical applications of boson *** we propose that boson sampling can be used to efficiently simulate the work distribution of multiple identical *** link the work distribution to boson sampling and numerically calculate the transition amplitude matrix between the single-boson eigenstates in a one-dimensional quantum piston system,and then map the matrix to a linear optical network of boson *** work distribution can be efficiently simulated by the output probabilities of boson sampling using the method of the grouped probability *** scheme requires at most a polynomial number of the samples and the optical *** work opens up a new path towards the calculation of complex quantum work distribution using only photons and linear optics.

关键词： quantum simulation quantum work distribution boson sampling linear optic

Deciphering and integrating invariants for neural operator learning with various physical mechanisms

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

National Science Review 2024年第4期11卷 111-122页

作者： Rui Zhang qi Meng Zhi-Ming ma Academy of mathematics and Systems Science Chinese Academy of Sciences(CAS) Microsoft Research

Neural operators have been explored as surrogate models for simulating physical systems to overcome the limitations of traditional partial differential equation(PDE) solvers. However, most existing operator learning methods assume that the data originate from a single physical mechanism, limiting their applicability and performance in more realistic scenarios. To this end, we propose the physical invariant attention neural operator(PIANO) to decipher and integrate the physical invariants for operator learning from the PDE series with various physical mechanisms. PIANO employs self-supervised learning to extract physical knowledge and attention mechanisms to integrate them into dynamic convolutional *** to existing techniques, PIANO can reduce the relative error by 13.6%–82.2% on PDE forecasting tasks across varying coefficients, forces or boundary conditions. Additionally, varied downstream tasks reveal that the PI embeddings deciphered by PIANO align well with the underlying invariants in the PDE systems, verifying the physical significance of PIANO.

关键词： neural operator PDE solver contrastive learning physical invariants

一类耦合非线性振子同步混沌Hopf分岔及其电路仿真

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

物理学报 2005年第3期54卷 1064-1070页

作者：马文麒杨承辉北华大学理学院物理系吉林132013

对于一类同时存在扩散耦合和梯度耦合的非线性振子系统 ,通过空间傅里叶变换 ,得到具有不同波矢的各运动模式的相互独立的运动方程 .计算各横截模的Lyapunov指数 ,可在耦合参数平面上确定同步混沌的稳定区域 .在稳定区域边界 ,一对共轭... 详细信息

对于一类同时存在扩散耦合和梯度耦合的非线性振子系统 ,通过空间傅里叶变换 ,得到具有不同波矢的各运动模式的相互独立的运动方程 .计算各横截模的Lyapunov指数 ,可在耦合参数平面上确定同步混沌的稳定区域 .在稳定区域边界 ,一对共轭横截模式失稳 ,导致同步混沌的Hopf分岔 .对耦合Lorenz振子系统进行了数值模拟 ,并设计了耦合Lorenz振子系统的电路 ,进行耦合振子系统同步混沌Hopf分岔的电路仿真实验 .计算和仿真的结果表明 ,Hopf分岔的特征频率等于失稳横截模式的振荡频率 .

关键词：振子 Hopf分岔混沌相互独立耦合稳定区域共轭同步电路仿真振荡频率

Pure-high-even-order dispersion bound solitons complexes in ultra-fast fiber lasers

在线全文

学校读者我要写书评

暂无评论

Light(Science & Applications) 2024年第5期13卷 957-972页

作者： Ying Han Bo Gao Honglin wen Chunyang ma Jiayu Huo Yingying Li Luyao Zhou qi Li Ge Wu Lie Liu College of Communication Engineering Jilin UniversityChangchun 130012China. Research Center of Circuits and Systems Peng Cheng LaboratoryShenzhen 518055China. International Collaborative Laboratory of 2D materials for Optoelectronics Science and Technology of Ministry of Education Institute of Microscale OptoelectronicsShenzhen UniversityShenzhen 518060China. College of Electronic Science and Engineering Jilin UniversityChangchun 130012China

Temporal solitons have been the focus of much research due to their fascinating physical *** solitons can form bound states,which are fundamentally crucial modes in fiber laser and present striking analogies with their matter molecules counterparts,which means they have potential applications in large-capacity transmission and alloptical information *** traditionally,second-order dispersion has been the dominant dispersion for conventional solitons,recent experimental and theoretical research has shown that pure-high-even-order dispersion(PHEOD)solitons with energy-width scaling can arise from the interaction of arbitrary negative-even-order dispersion and Kerr *** these advancements,research on the bound states of PHEOD solitons is currently *** this study,we obtained PHEOD bound solitons in a fiber laser using an intra-cavity spectral pulse shaper for high-order dispersion ***,we experimentally demonstrate the existence of PHEOD solitons and PHEOD bound solitons with pure-quartic,-sextic,-octic,and-decic *** simulations corroborate these experimental ***,vibrating phase PHEOD bound soliton pairs,sliding phase PHEOD bound soliton pairs,and hybrid phase PHEOD bound tri-soliton are discovered and *** results broaden the fundamental understanding of solitons and show the universality of multi-soliton patterns.

关键词： dispersion solitons soliton