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Performance Limits and Advancements in Single 2D Transition Metal Dichalcogenide Transistor
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作者 Jing Chen Ming-Yuan Sun +8 位作者 Zhen-Hua Wang Zheng Zhang Kai Zhang Shuai Wang Yu Zhang Xiaoming Wu Tian-Ling Ren Hong Liu Lin Han 《Nano-Micro Letters》 SCIE EI CAS CSCD 2024年第12期134-188,共55页
Two-dimensional(2D)transition metal dichalcogenides(TMDs)allow for atomic-scale manipulation,challenging the conventional limitations of semiconductor materials.This capability may overcome the short-channel effect,sp... Two-dimensional(2D)transition metal dichalcogenides(TMDs)allow for atomic-scale manipulation,challenging the conventional limitations of semiconductor materials.This capability may overcome the short-channel effect,sparking significant advancements in electronic devices that utilize 2D TMDs.Exploring the dimension and performance limits of transistors based on 2D TMDs has gained substantial importance.This review provides a comprehensive investigation into these limits of the single 2D-TMD transistor.It delves into the impacts of miniaturization,including the reduction of channel length,gate length,source/drain contact length,and dielectric thickness on transistor operation and performance.In addition,this review provides a detailed analysis of performance parameters such as source/drain contact resistance,subthreshold swing,hysteresis loop,carrier mobility,on/off ratio,and the development of p-type and single logic transistors.This review details the two logical expressions of the single 2D-TMD logic transistor,including current and voltage.It also emphasizes the role of 2D TMD-based transistors as memory devices,focusing on enhancing memory operation speed,endurance,data retention,and extinction ratio,as well as reducing energy consumption in memory devices functioning as artificial synapses.This review demonstrates the two calculating methods for dynamic energy consumption of 2D synaptic devices.This review not only summarizes the current state of the art in this field but also highlights potential future research directions and applications.It underscores the anticipated challenges,opportunities,and potential solutions in navigating the dimension and performance boundaries of 2D transistors. 展开更多
关键词 Two-dimensional transistors Dimension limits Performance limits Memory devices Artificial synapses
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Cosmology-Independent Photon Mass Limits from Localized Fast Radio Bursts by Using Artificial Neural Networks
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作者 冉景遇 王宝 魏俊杰 《Chinese Physics Letters》 SCIE EI CAS CSCD 2024年第5期177-183,共7页
A hypothetical photon mass m_(γ) can produce a frequency-dependent vacuum dispersion of light, which leads to an additional time delay between photons with different frequencies when they propagate through a fixed di... A hypothetical photon mass m_(γ) can produce a frequency-dependent vacuum dispersion of light, which leads to an additional time delay between photons with different frequencies when they propagate through a fixed distance. The dispersion measure and redshift measurements of fast radio bursts(FRBs) have been widely used to constrain the rest mass of the photon. However, all current studies analyzed the effect of the frequency-dependent dispersion for massive photons in the standard ΛCDM cosmological context. In order to alleviate the circularity problem induced by the presumption of a specific cosmological model based on the fundamental postulate of the masslessness of photons, here we employ a new model-independent smoothing technique, artificial neural network(ANN), to reconstruct the Hubble parameter H(z) function from 34 cosmic-chronometer measurements.By combining observations of 32 well-localized FRBs and the H(z) function reconstructed by ANN, we obtain an upper limit of m_(γ) ≤ 3.5 × 10^(-51)kg, or equivalently m_(γ) ≤ 2.0 × 10^(-15)eV/c^(2)(m_(γ) ≤ 6.5 × 10^(-51)kg, or equivalently m_(γ) ≤ 3.6 × 10^(-15)eV/c_(2)) at the 1σ(2σ) confidence level. This is the first cosmology-independent photon mass limit derived from extragalactic sources. 展开更多
关键词 DISPERSION LIMIT INDEPENDENT
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Molecular Dynamics Numerical Simulation of Adsorption Characteristics and Exploitation Limits in Shale Oil Microscopic Pore Spaces
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作者 Guochen Xu 《Fluid Dynamics & Materials Processing》 EI 2024年第8期1915-1924,共10页
Microscopic pore structure in continental shale oil reservoirs is characterized by small pore throats and complex micro-structures.The adsorption behavior of hydrocarbons on the pore walls exhibits unique physical and... Microscopic pore structure in continental shale oil reservoirs is characterized by small pore throats and complex micro-structures.The adsorption behavior of hydrocarbons on the pore walls exhibits unique physical and chemical properties.Therefore,studying the adsorption morphology of hydrocarbon components in nanometer-sized pores and clarifying the exploitation limits of shale oil at the microscopic level are of great practical significance for the efficient development of continental shale oil.In this study,molecular dynamics simulations were employed to investigate the adsorption characteristics of various single-component shale oils in inorganic quartz fissures,and the influence of pore size and shale oil hydrocarbon composition on the adsorption properties in the pores was analyzed.The results show that different molecules have different adsorption capacities in shale oil pores,with lighter hydrocarbon components(C6H14)exhibiting stronger adsorption abilities.For the same adsorbed molecule,the adsorption amount linearly increases with the increase in pore diameter,but larger pores contribute more to shale oil adsorption.In shale pores,the thickness of the adsorption layer formed by shale oil molecules ranges from 0.4 to 0.5 nm,which is similar to the width of alkane molecules.Shale oil in the adsorbed state that is difficult to be exploited is mainly concentrated in the first adsorption layer.Among them,the volume fraction of adsorbed shale oil in 6 nm shale pores is 40.8%,while the volume fraction of shale oil that is difficult to be exploited is 16.2%. 展开更多
关键词 Shale oil utilization limit micro adsorption molecular dynamics simulation
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Estimation of speed-related car body acceleration limits with quantile regression
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作者 Jianli Cong Hang Zhang +6 位作者 Zilong Wei Fei Yang Zaitian Ke Tao Lu, Rong Chen Ping Wang Zili Li 《Railway Sciences》 2024年第5期575-592,共18页
Purpose–This study aimed to facilitate a rapid evaluation of track service status and vehicle ride comfort based on car body acceleration.Consequently,a low-cost,data-driven approach was proposed for analyzing speed-... Purpose–This study aimed to facilitate a rapid evaluation of track service status and vehicle ride comfort based on car body acceleration.Consequently,a low-cost,data-driven approach was proposed for analyzing speed-related acceleration limits in metro systems.Design/methodology/approach–A portable sensing terminal was developed to realize easy and efficient detection of car body acceleration.Further,field measurements were performed on a 51.95-km metro line.Data from 272 metro sections were tested as a case study,and a quantile regression method was proposed to fit the control limits of the car body acceleration at different speeds using the measured data.Findings–First,the frequency statistics of the measured data in the speed-acceleration dimension indicated that the car body acceleration was primarily concentrated within the constant speed stage,particularly at speeds of 15.4,18.3,and 20.9 m/s.Second,resampling was performed according to the probability density distribution of car body acceleration for different speed domains to achieve data balance.Finally,combined with the traditional linear relationship between speed and acceleration,the statistical relationships between the speed and car body acceleration under different quantiles were determined.We concluded the lateral/vertical quantiles of 0.8989/0.9895,0.9942/0.997,and 0.9998/0.993 as being excellent,good,and qualified control limits,respectively,for the lateral and vertical acceleration of the car body.In addition,regression lines for the speedrelated acceleration limits at other quantiles(0.5,0.75,2s,and 3s)were obtained.Originality/value–The proposed method is expected to serve as a reference for further studies on speedrelated acceleration limits in rail transit systems. 展开更多
关键词 Car body acceleration Track status monitoring Speed-related acceleration limit Quantile regression Vehicle ride quality
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The Effect of Mineral Composition and Quantity of Fines on the Atterberg Limits and Compaction Characteristics of Soils
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作者 Abdalhamid Musbah Muad Mohammed Adem Alfghia 《Open Journal of Civil Engineering》 2024年第2期258-276,共19页
Because of the various elements that come into play in natural soil formation, the impact of varied proportions of mineral composition and fines amount on Atterberg limits and compaction characteristics of soils is no... Because of the various elements that come into play in natural soil formation, the impact of varied proportions of mineral composition and fines amount on Atterberg limits and compaction characteristics of soils is not well known. Three distinct soil samples were used in this investigation. The findings indicated the effect of varied mineral composition proportions and fines amount on the liquid limit, plastic limit, and plasticity index as assessed by the Casagrande test and hand-rolling method. The fluctuation of maximum dry density and optimal moisture content with these three soils has also been studied. Furthermore, correlations were established to indicate the compaction parameters and the amount of minerals and particles in the soil. The data show that the mineral content of the soil has a direct impact on the Atterberg limits and compaction characteristics. Soils containing larger percentages of expansive minerals, such as montmorillonite, have more flexibility and volume change capability. Mineral composition influences compaction parameters such as maximum dry density, ideal water content, axial strain, and axial stress. Soils with a larger proportion of fines, such as Soil 2 and Soil 3, have stronger flexibility and lower compaction qualities, with higher ideal water content and lower maximum dry density. Soil 1 has moderate flexibility and intermediate compaction qualities due to its low fines percentage. The effect of different mineral compositions and fines on the Atterberg limits and compaction characteristics of soils can be used to predict the behavior of compacted soils encountered in engineering practices, reducing the time and effort required to assess soil suitability for engineering use. 展开更多
关键词 Atterberg Limit Mineral Composition Quantity of Fines Maximum Dry Unit Weight Optimum Water Content
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Different Deficit Irrigation Lower Limits and Irrigation Quotas Affect the Yield and Water Use Efficiency of Winter Wheat by Regulating Photosynthetic Characteristics
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作者 Huiqin Li Mingzhi Zhang +1 位作者 Na Xiao Haijian Yang 《Phyton-International Journal of Experimental Botany》 SCIE 2023年第12期3211-3236,共26页
To determine suitable thresholds for deficit irrigation of winter wheat in the well-irrigated area of the Huang-Huai-Hai Plain,we investigated the effects of different deficit irrigation lower limits and quotas on the... To determine suitable thresholds for deficit irrigation of winter wheat in the well-irrigated area of the Huang-Huai-Hai Plain,we investigated the effects of different deficit irrigation lower limits and quotas on the photosynthetic characteristics and grain yield of winter wheat.Four irrigation lower limits were set for initiating irrigation(i.e.,light drought(LD,50%,55%,60%and 50%of field holding capacity(FC)at the seedling-regreening,jointing,heading and filling-ripening stages,respectively),medium drought(MD,40%,50%,55%and 45%of FC at the same stages,respectively),adequate moisture(CK1,60%,65%,70%and 60%of FC at the same stages,respectively),heavy drought(CK2,35%,40%,45%and 40%of FC at the same stages,respectively))and five irrigation quota per event(30,60,90,120 and 180 mm)were set for each lower limit.We found that the increase of drought stress is conducive to normal photosynthesis of winter wheat leaves which is supported by the following findings.First,photosynthetic rate(Pn)of LD60 treatment was higher than that of LD30,LD90,LD120,LD180,MD30,MD60,MD90,MD120 and MD180.Then,Under the 90 mm irrigation quota treatment,the yield of winter wheat basically increased with the increase of irrigation’s lower limit.Moreover,With the increase in irrigation quota,the yield of winter wheat increased,and the water use efficiency(WUE)of winter wheat increased at first and then decreased.In addition,compared with the LD30,MD30,MD60,MD90,MD120,and MD180,the yield of winter wheat in LD60 treatment increased by about 3.23%(3-year average),32.3%,19.9%,11.7%,10.1%,and 14.6%.At the same time,the WUE with LD60 treatment of winter wheat was significantly higher than LD90,LD120,LD180,MD30,MD60,MD90,MD120,MD180 treatments.There was a positive correlation between soil volumetric water content and Pn and between yield and Pn.The key period for yield formation in winter wheat is 180 days after sowing.In conclusion,to achieve the dual goals of stable winter wheat yield and efficient utilization of water resources in this region,the suitable threshold for initiating deficit irrigation of winter wheat is the LD60 treatment.This conclusion provides data support for water-saving and stable yield of winter wheat in this area. 展开更多
关键词 Irrigation lower limit irrigation quota soil volume moisture content photosynthetic rate YIELD regression analysis
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Study on wear characteristics and authorized limits of switch rails of high-speed turnout
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作者 Pu Wang Shuguo Wang +2 位作者 Jing Ge Daolin Si Dongsheng Yang 《Railway Sciences》 2023年第2期157-169,共13页
Purpose-It is quite universal for high-speed turnouts to be exposed to the wear of the stock rail of the switch rail during the service process.The wear will cause the change of railhead profile and the relative posit... Purpose-It is quite universal for high-speed turnouts to be exposed to the wear of the stock rail of the switch rail during the service process.The wear will cause the change of railhead profile and the relative positions of the switch rail and the stock rail,which will directly affect the wheel-rail contact state and wheel load transition when a train passes the turnout and will further impose serious impacts on the safety and stability of train operation.The purpose of this paper is to provide suggestions for wear management of high-speed turnout.Design/methodology/approach-The actual wear characteristics of switch rails of high-speed turnouts in different guiding directions were studied based on the monitoring results on site;the authorized wear limits for the switch rails of high-speed turnout were studied through derailment risk analysis and switch rail strength analysis.Findings-The results show that:the major factor for the service life of a curved switch rail is the lateral wear.The wear characteristics of the curved switch rail of a facing turnout are significantly different from those of a trailing turnout.To be specific,the lateral wear of the curved switch rail mainly occurs in the narrower section at its front end for a trailing turnout,but in the wider section at its rear end when for a facing turnout.The maximum lateral wear of a dismounted switch rail from a trailing turnout is found on the 15-mm wide section and is 3.9 mm,which does not reach the specified limit of 6 mm.For comparison,the lateral wear of a dismounted switch rail from a facing turnout is found from the 35-mm wide section to the full-width section and is greater than 7.5 mm,which exceeds the specified limit.Based on this,in addition to meeting the requirements of maintenance rules,the allowed wear of switch rails of high-speed turnout shall be so that the dangerous area with a tangent angle of wheel profile smaller than 43.68 will not contact the switch rail when the wheel is lifted by 2 mm.Accordingly,the lateral wear limit at the 5-mm wide section of the curved switch rail shall be reduced from 6 mm(as specified)to 3.5 mm.Originality/value-The work in this paper is of reference significance to the research on the development law of rail wear in high-speed turnout area and the formulation of relevant standards. 展开更多
关键词 High-speed turnout Switch rail Wear characteristics Authorized limit DERAILMENT STRENGTH On-site monitoring
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基于极限平衡法的危岩倾覆稳定性三维计算方法 被引量:2
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作者 彭海游 谢强 +3 位作者 陈柏林 檀康 王琦 杨文君 《岩土力学》 EI CAS CSCD 北大核心 2024年第2期552-562,共11页
目前危岩防治工作中,危岩稳定性评价主要以简化后的二维剖面作为计算模型。由于自然界中的危岩形态极不规则,采用二维剖面计算模型并不能真实反映危岩受力情况。为了研究危岩稳定性三维计算方法,在前人研究基础上,基于极限平衡理论,提... 目前危岩防治工作中,危岩稳定性评价主要以简化后的二维剖面作为计算模型。由于自然界中的危岩形态极不规则,采用二维剖面计算模型并不能真实反映危岩受力情况。为了研究危岩稳定性三维计算方法,在前人研究基础上,基于极限平衡理论,提出了由后缘裂缝抗拉强度控制的危岩倾覆稳定性三维计算公式,采用数值积分和空间几何方法给出了在危岩单体三维模型基础上求解危岩后缘岩体抗拉力、水压力及其力矩计算公式和实现流程。以三峡库区瞿塘峡吊嘴危岩为实例开展了应用,并通过数值分析进行了验证。通过不同形态危岩的三维稳定性分析,讨论了三维与二维稳定性计算结果的关系,对比发现危岩形态对稳定性计算结果有明显影响,三维计算较二维计算更准确和实用。 展开更多
关键词 危岩 倾覆稳定性 三维 极限平衡法
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文本分类算法及其应用场景研究综述 被引量:1
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作者 刘晓明 李丞正旭 +7 位作者 吴少聪 张宇辰 白红艳 程泽华 陈卓 李永峰 兰钰 沈超 《计算机学报》 EI CAS CSCD 北大核心 2024年第6期1244-1287,共44页
随着大数据时代的到来,互联网中的文本信息迎来了井喷式的增长.文本分类作为自然语言处理中最重要的技术之一,其广泛应用于多个领域,如情感分析、新闻分类、自然语言推理、主题标记、抽取式问答、虚假内容检测等.从传统机器学习分类方... 随着大数据时代的到来,互联网中的文本信息迎来了井喷式的增长.文本分类作为自然语言处理中最重要的技术之一,其广泛应用于多个领域,如情感分析、新闻分类、自然语言推理、主题标记、抽取式问答、虚假内容检测等.从传统机器学习分类方法理论的深入到深度学习分类方法探索的兴起,相关研究模型与思路也在不断演变,各类新的方法、数据集和评价指标层出不穷,丰富了文本分类领域的研究,取得了卓越的理论成就和应用效果.尽管如此,新技术不断发展和业务应用场景不断丰富,同时,也为文本分类研究带来了许多新的问题与挑战,如数据约束场景中不均衡数据的文本表征学习、小样本场景下的文本分类等.针对当前研究难题与挑战,本文对文本分类方法进行了系统性调研,并对当前方法在实际应用场景中面临的技术挑战和未来的研究方向进行了综合探讨.具体而言,本文主要综述了七部分内容,分别是:(1)对文本分类技术的相关基础知识进行了全面介绍,包括文本分类的常见符号定义、计算范式和文本预处理技术;(2)对基于传统机器学习的文本分类方法进行了详细总结;同时,为了方便读者针对不同的应用场景选择合适的分类模型,本文对不同分类器擅长处理的文本分类难题及方法优劣进行了总结;(3)对基于新兴深度学习的文本分类方法进行了周详梳理,根据领域内代表性技术的核心思想进行分类,在此基础上对不同类别下的主要方法进行描述,同时对其技术的优劣进行了总结;(4)为了方便读者对文本分类模型的有效性进行验证,针对文本分类技术应用最为广泛的七大场景,本文对相关数据集进行了系统性的总结;(5)本文对不同任务目标下的常用的模型评价方法进行详尽介绍,以便对模型性能进行合理的定量评估;(6)基于上述内容,本文对典型应用场景中不同种类文本分类算法进行了性能总结对比;(7)本文分别从数据约束与模型计算两个层面对当前文本分类技术所面临的挑战和未来的重要研究方向进行了总结.本文通过梳理文本分类研究发展脉络,对涉及的代表性技术进行了详细总结和对比分析,有效填补了文本分类领域前沿技术的应用综述空白. 展开更多
关键词 文本分类 机器学习 深度学习 评价指标 数据约束
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植物生长调节剂在花生中的应用及安全性分析 被引量:1
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作者 林秋君 吴限鑫 +3 位作者 邹询 李广 王建忠 郭春景 《农学学报》 2024年第8期24-29,共6页
为明确花生生产中植物生长调节剂的使用情况,通过查询中国农药信息网,统计汇总花生目前有效登记调节剂种类,并查询食品安全国家标准《食品中农药最大残留限量》(GB 2763—2021)中花生中调节剂的最大残留限量和检测方法,分析花生生产中... 为明确花生生产中植物生长调节剂的使用情况,通过查询中国农药信息网,统计汇总花生目前有效登记调节剂种类,并查询食品安全国家标准《食品中农药最大残留限量》(GB 2763—2021)中花生中调节剂的最大残留限量和检测方法,分析花生生产中主要使用的调节剂的毒性,为下一步相关标准的制定和修订提出意见和建议,同时也为花生产业的出口创汇及高质量发展提供参考,提升中国花生产业的国际竞争力,保障中国花生产业健康可持续发展。 展开更多
关键词 花生 植物生长调节剂 农药登记 残留限量 安全性分析
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基于轻型自限制注意力的结构光相位及深度估计混合网络 被引量:1
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作者 朱新军 赵浩淼 +2 位作者 王红一 宋丽梅 孙瑞群 《中国光学(中英文)》 EI CAS CSCD 北大核心 2024年第1期118-127,共10页
相位提取与深度估计是结构光三维测量中的重点环节,目前传统方法在结构光相位提取与深度估计方面存在效率不高、结果不够鲁棒等问题。为了提高深度学习结构光的重建效果,本文提出了一种基于轻型自限制注意力(Light Self-Limited-Attenti... 相位提取与深度估计是结构光三维测量中的重点环节,目前传统方法在结构光相位提取与深度估计方面存在效率不高、结果不够鲁棒等问题。为了提高深度学习结构光的重建效果,本文提出了一种基于轻型自限制注意力(Light Self-Limited-Attention,LSLA)的结构光相位及深度估计混合网络,即构建一种CNN-Transformer的混合模块,并将构建的混合模块放入U型架构中,实现CNN与Transformer的优势互补。将所提出的网络在结构光相位估计和结构光深度估计两个任务上进行实验,并和其他网络进行对比。实验结果表明:相比其他网络,本文所提出的网络在相位估计和深度估计的细节处理上更加精细,在结构光相位估计实验中,精度最高提升31%;在结构光深度估计实验中,精度最高提升26%。该方法提高了深度神经网络在结构光相位估计及深度估计的准确性。 展开更多
关键词 结构光 深度学习 自限制注意力 相位估计 深度估计
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平台经济领域强化反垄断的正当性与合理限度 被引量:2
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作者 王先林 《苏州大学学报(哲学社会科学版)》 北大核心 2024年第2期73-84,共12页
近些年来,国内外在平台经济领域开展了声势浩大的反垄断行动,尤其是欧盟出台的《数字市场法》和我国强调“强化反垄断和防止资本无序扩张”备受关注。基于平台经济竞争的鲜明特点和数字平台对经济社会的巨大影响,强化平台经济领域的反... 近些年来,国内外在平台经济领域开展了声势浩大的反垄断行动,尤其是欧盟出台的《数字市场法》和我国强调“强化反垄断和防止资本无序扩张”备受关注。基于平台经济竞争的鲜明特点和数字平台对经济社会的巨大影响,强化平台经济领域的反垄断有其理论上的正当性和现实的必要性。与此同时,平台经济创新发展的内在要求又决定了在平台经济领域的反垄断有其合理的边界和必要的限度。美国和欧盟等在平台经济领域反垄断上的差异性反映了国际竞争的现实情况,我国需要从国家利益最大化角度出发对平台经济领域反垄断策略做出理性选择,以促进我国平台经济规范健康持续发展。 展开更多
关键词 平台经济 反垄断 正当性 合理限度
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家蚕素斑品种菁松的茶斑限性定向转育
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作者 廖鹏飞 李琼艳 +7 位作者 罗顺高 刘敏 朱红涛 李继娅 白红英 陈海佺 范永慧 董占鹏 《浙江农业学报》 CSCD 北大核心 2024年第5期1032-1040,共9页
为在家蚕现行素斑品种菁松的幼虫发育早期进行雌雄性别鉴别,实现雌雄分养分缫差异化利用目的,用普斑限性品系云蚕7A的雌与茶斑品系Cb的雄杂交后,再分别与现行素斑品系菁松A、菁松B杂交,其后代连续数次回交素斑亲本后自交,结合分类选择... 为在家蚕现行素斑品种菁松的幼虫发育早期进行雌雄性别鉴别,实现雌雄分养分缫差异化利用目的,用普斑限性品系云蚕7A的雌与茶斑品系Cb的雄杂交后,再分别与现行素斑品系菁松A、菁松B杂交,其后代连续数次回交素斑亲本后自交,结合分类选择进行个体和蛾区选择淘汰,将云蚕7A的普斑限性基因和Cb的茶斑基因转入现行素斑品种菁松中,定向转育得到菁A茶限和菁B茶限。结果表明:转育过程中,幼虫斑纹分化成颜色与形状易于分辨的茶斑与非茶斑2种类型,转育得到的菁A茶限和菁B茶限幼虫在3龄初期就会呈现茶斑颜色深浅明显不同的分化,能准确分辨雌雄,其虫蛹率分别为96.91%和96.40%,全茧量分别为1.62 g和1.56 g,茧层率分别为23.78%和23.26%,经济性状与其轮回亲本的差异较小,表现出健康好养、茧质优良等特性。研究结果可为创建特殊性状的育种材料、差异化利用雌雄蚕,以及降低雄蚕种繁育成本奠定基础。 展开更多
关键词 家蚕品种 普斑限性 素斑 茶斑限性 定向转育
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石灰石露天矿高陡边坡稳定性计算分析 被引量:7
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作者 赵翔 朱刚 +2 位作者 温楷 王荣 廖正彪 《水泥技术》 2024年第2期34-40,共7页
以西南某石灰石矿高陡边坡为研究对象,根据矿山边坡现状、边坡岩体结构和结构面发育特征因素对“现状边坡”和“终了边坡”进行地质分区,通过岩石室内物理力学试验获得坡体岩石物理力学参数,采用GSI法计算边坡岩体内摩擦角、粘聚力、变... 以西南某石灰石矿高陡边坡为研究对象,根据矿山边坡现状、边坡岩体结构和结构面发育特征因素对“现状边坡”和“终了边坡”进行地质分区,通过岩石室内物理力学试验获得坡体岩石物理力学参数,采用GSI法计算边坡岩体内摩擦角、粘聚力、变形模量和泊松比等参数,评估边坡地质强度特性,采用Morgenstern-Price极限平衡法分三种荷载工况分别计算“现状边坡”和“终了边坡”各分区稳定性系数。经分析,该石灰石矿各地质分区“现状边坡”和“终了边坡”稳定性好,采场边坡参数设计合理,可为矿山扩产安全设施设计和安全生产提供参考。 展开更多
关键词 高陡边坡 地质强度指标 极限平衡法 安全生产
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大学生就业能力培养中高校的“有限责任” 被引量:4
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作者 周双喜 谢延浩 《黑龙江高教研究》 北大核心 2024年第1期147-153,共7页
培养大学生就业能力是高等教育的本职所在、应有之义,是高校的主责主业之一,但就业能力培养参与主体多元、影响因素众多,不能任意放大单一主体的责任,亟须在高校、政府、雇主、学生个体等利益相关者之间建立明确的责任分担机制。高校在... 培养大学生就业能力是高等教育的本职所在、应有之义,是高校的主责主业之一,但就业能力培养参与主体多元、影响因素众多,不能任意放大单一主体的责任,亟须在高校、政府、雇主、学生个体等利益相关者之间建立明确的责任分担机制。高校在大学生就业能力培养方面客观存在权力有限性、能力有限性与资源有限性,应针对性进行责任的纵向和横向配置,建立基于时间和基于范畴的有限责任,明确大学生就业能力培养中高校的责任边界,有效区分高校在大学生就业能力培养内容产品提供方面的主导责任、个人与自我方面的引导责任以及服务与机会方面的支持责任。 展开更多
关键词 大学生就业能力 高校 有限责任 高等教育 责任分担
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ChatGPT视域下的知识限度与积极物化:从庄周出发的思考 被引量:1
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作者 高奇琦 《河北学刊》 北大核心 2024年第1期10-20,共11页
ChatGPT可以被看成是一个“自本自根”的世界模型。在其内部的神经网络之中,似乎存在一个道家所强调的道。然而,从《庄子·知北游》中的两段经典对话中我们获得的新启示是,ChatGPT所表达的那些可言说的知识未必是真实可靠的知识。同... ChatGPT可以被看成是一个“自本自根”的世界模型。在其内部的神经网络之中,似乎存在一个道家所强调的道。然而,从《庄子·知北游》中的两段经典对话中我们获得的新启示是,ChatGPT所表达的那些可言说的知识未必是真实可靠的知识。同时,使用者与ChatGPT的对话往往会演变为一方对另一方的臣服或对抗,而日常生活中的多人对话往往可以提供一种对结论的开放性。大模型的无限知识同样存在进一步的进化空间。与ChatGPT相比,GPT-4明显知道了自己知识的限度。目前的大模型框架更多是一种普遍性框架,其对问题的回答往往是通用性的解释,而进化的方向恰恰是要增加向量数据库。知识限度的意义就在于要回到多样性本身。人类对大模型的有待使用,最终会产生无待焦虑。换言之,当外在依赖变成内在依赖的时候,人们就会产生无待焦虑。这种无待焦虑最终会演化为后人类焦虑。破除这些焦虑的关键,同样需要在庄周思想中挖掘。这种积极物化的关键是,放低身段,将自己置于一个与物平等的角度,向物学习,格物致知,最终达到物我两忘的真人之境。从庄周丧我的角度可以更加接近物我两忘,其最终可能会帮助人类进入人机和谐相处的两行世界。 展开更多
关键词 ChatGPT GPT 知识限度 积极物化 庄周
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基于均匀化理论与上限分析的膨胀土滑坡稳定性分析 被引量:1
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作者 杨晓华 王东清 +1 位作者 袁帅 张毅 《水文地质工程地质》 CAS CSCD 北大核心 2024年第2期172-182,共11页
在膨胀土和滑坡共同作用下,隧道洞口段施工更容易引发地表开裂甚至滑坡等工程灾害,在隧道内采用微型桩群防治滑坡比抗滑桩具有优势。本文基于均匀化理论与上限分析对某高速公路隧道洞口段膨胀土滑坡的稳定性进行计算,并评价微型桩群和... 在膨胀土和滑坡共同作用下,隧道洞口段施工更容易引发地表开裂甚至滑坡等工程灾害,在隧道内采用微型桩群防治滑坡比抗滑桩具有优势。本文基于均匀化理论与上限分析对某高速公路隧道洞口段膨胀土滑坡的稳定性进行计算,并评价微型桩群和削方卸载不同组合方式的处置效果,计算时将微型桩群及桩周土通过均匀化理论等效为符合摩尔库仑强度准则的等效加固体来,以此提高计算效率,最后通过对现场削方+微型桩群加固处置后的滑坡变形监测来验证计算的合理性,得出如下结论:相较于土的强度参数,等效加固体内摩擦角保持不变,黏聚力从26kPa提高到85.36kPa。处置前后的滑坡稳定性评价结果表明,不做处理时,滑坡滑动面从滑坡上方岩土交界面延续到隧道洞口前;仅采用微型桩群加固时,滑坡安全系数在1.17左右,滑动面从岩土交界面延续到隧道洞口后;同时采用微型桩群加固和削方卸载时,滑坡安全系数提高到1.26~1.28,滑动面上缘由土石交界面前移。现场变形监测表明地表变形与深层土体变形均不超过3mm,该措施能保障滑坡的稳定性,同时也验证了计算方法的合理性,可为同类工程提供参考。 展开更多
关键词 膨胀土滑坡 均匀化理论 极限分析 强度折减法 现场变形监测
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基于光储混合配置的级联H桥型光伏逆变器功率平衡策略 被引量:1
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作者 孙孝峰 刘鑫磊 +3 位作者 滕甲训 张㼆 赵巍 李昕 《中国电机工程学报》 EI CSCD 北大核心 2024年第5期1948-1961,I0024,共15页
级联H桥(cascade H-bridge,CHB)变换器由于其模块化结构,已成为大规模光伏(photovoltaic,PV)并网逆变器的优选方案。然而,在不同光照强度和温度下,不同区域PV组件之间发电功率不同,导致CHB变换器相间输出功率不均衡、不稳定等问题。为此... 级联H桥(cascade H-bridge,CHB)变换器由于其模块化结构,已成为大规模光伏(photovoltaic,PV)并网逆变器的优选方案。然而,在不同光照强度和温度下,不同区域PV组件之间发电功率不同,导致CHB变换器相间输出功率不均衡、不稳定等问题。为此,文中提出一种基于CHB结构的光储混合电能路由,在三相CHB光伏逆变器中配置少量的储能模块,利用光储协同控制,维持CHB内部功率稳定,消除分布式PV在相间产生的不均衡功率,且变换器输出功率能够时刻满足网侧上层功率调度,提高了光伏电站的稳定性。针对系统安全区域,在载波移相调制策略下,全桥子模块传输的功率受到约束,并对光伏和储能模块的配置作详细分析。最后,通过仿真以及实验验证所提拓扑及控制策略的正确性和有效性。 展开更多
关键词 级联H桥变换器 光伏 功率不均衡 集中式储能 功率限值
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SPS监管差异对中国果蔬类农产品出口贸易的影响——基于农药最大残留限量标准视角
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作者 董银果 吴宇森 《农林经济管理学报》 北大核心 2024年第3期299-308,共10页
利用2022年中国对157个国家(地区)出口50种果蔬类农产品贸易数据,采用Heckman两阶段模型,基于农药最大残留限量(MRLs)视角,实证分析SPS监管差异对中国果蔬类农产品出口贸易的影响。结果表明:SPS监管差异抑制中国果蔬类农产品出口的二元... 利用2022年中国对157个国家(地区)出口50种果蔬类农产品贸易数据,采用Heckman两阶段模型,基于农药最大残留限量(MRLs)视角,实证分析SPS监管差异对中国果蔬类农产品出口贸易的影响。结果表明:SPS监管差异抑制中国果蔬类农产品出口的二元边际,即贸易成本效应大于竞争优势效应,贸易成本效应抑制扩展边际和集约边际,而竞争优势效应仅促进集约边际;SPS监管差异对中国向发达国家出口以及对蔬菜农产品出口的抑制作用更大;杀菌剂监管差异对集约边际和扩展边际均具有抑制作用,而杀虫剂监管差异仅抑制集约边际。据此,提出对标国际高标准SPS措施、帮助中小型企业克服技术难关、宣传食品安全理念等政策建议。 展开更多
关键词 SPS监管差异 农药最大残留限量 果蔬类农产品 出口二元边际
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雾天桥梁可变限速值的效用评估及优化 被引量:1
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作者 张建华 赵晓华 +2 位作者 欧居尚 栾森 戴义博 《华南理工大学学报(自然科学版)》 EI CSCD 北大核心 2024年第1期127-138,共12页
为改善高速公路桥梁路段雾天环境的交通安全,文中考虑可变限速标志设置对驾驶行为的影响,从服从效应角度提出其量化评估方法,以期获得最优作用效能。文中以鄂东长江大桥为原型,选取该桥梁近年最低能见度(100 m)和自由流服务水平作为测... 为改善高速公路桥梁路段雾天环境的交通安全,文中考虑可变限速标志设置对驾驶行为的影响,从服从效应角度提出其量化评估方法,以期获得最优作用效能。文中以鄂东长江大桥为原型,选取该桥梁近年最低能见度(100 m)和自由流服务水平作为测试环境,设计3种限速策略,分别为对照组SⅠ(无限速策略)、实验组SⅡ(90~70 km/h限速策略)、实验组SⅢ(90~70~50 km/h逐级限速策略);依托驾驶模拟器,实现不同限速条件的雾天桥梁场景微观驾驶行为数据的细粒度感知,采用重复测量方差分析方法从驾驶人响应的快速性、稳定性及准确性剖析可变限速标志的作用机理及驾驶人特征表现,并通过模糊综合评价方法评估不同限速策略的有效性。研究结果表明:雾天桥梁可变限速标志能够使驾驶人更早地采取减速措施,车辆在雾区行驶过程的稳定性更好;在雾天能见度100 m情况下,90~70~50 km/h逐级限速策略的稳态频数更大,空间稳定性更好,且速度超调量和跟随比更小,响应准确性更高。模糊综合评估结果显示,90~70~50 km/h逐级限速策略作为最优方案,能够有效地提升雾区驾驶行为的调节适应能力,降低驾驶风险,提高车辆运行的稳定性。本研究成果为雾天桥梁可变限速标志的优化设置提供了解决方案,可为雾天桥梁的主动安全防控提供有效支撑。 展开更多
关键词 交通标志 可变限速标志 模糊综合评价 模拟器 重复测量方差分析
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