期刊文献+
共找到697篇文章
< 1 2 35 >
每页显示 20 50 100
The Influences of an Embedded Structure Fiber-Optic Radiation Dosimeter in Different SSD and Beam Field Size
1
作者 Yaosheng Hu Zhuang Qin +9 位作者 Yu Ma Chuntong Jiang Tianci Xie Wenhui Zhao Weimin Sun Daxin Zhang Ziyin Chen Boran Wang He Tian Elfed Lewis 《Optics and Photonics Journal》 2017年第8期75-80,共6页
With a rapidly increasing demand and widespread use of radiotherapy treatment, the subject area of in-vivo real time dose rate dosimeters has become a significant area of study. An embedded structure fiber-optic radia... With a rapidly increasing demand and widespread use of radiotherapy treatment, the subject area of in-vivo real time dose rate dosimeters has become a significant area of study. An embedded structure fiber-optic radiation dosimeter has proved to be a promising candidate to fulfil this role because of its high SNR (signal-to-noise ratio) and excellent light conversion efficiency. In this paper, the properties of this kind of dosimeter with respect to different SSD (Source to Surface Distance) and beam field size in a clinical Linac are studied. The characteristics of the dosimeter were evaluated by the sensor’s output intensity response in these conditions. 展开更多
关键词 Optical Fiber Sensing RADIATION SSD (Source to Surface Distance) BEAM field size
暂未订购
Rapid Synthesis of Submicrometer-sized Red Phosphor CaS∶Cu^+,Eu^( 2+) in a Microwave Field 被引量:7
2
作者 张迈生 《Rare Metals》 SCIE EI CAS CSCD 2000年第4期279-284,共6页
The red phosphor materials CaS∶Cu+,Eu 2+ were firstly synthesized in a microwave field, and characterized by XRD、SEM、fluorescent spectroscopy. The experimental results of XRD and SEM show that the phosphors of CaS... The red phosphor materials CaS∶Cu+,Eu 2+ were firstly synthesized in a microwave field, and characterized by XRD、SEM、fluorescent spectroscopy. The experimental results of XRD and SEM show that the phosphors of CaS∶Cu+,Eu 2+ possess a spherical crystallite structure, in the submicrometer(250~500 nm) size range. Compared to the conventional high temperature solid state reaction this new synthetic technique exhibits interesting features, such as rapid reactions without other protective atmosphere,phosphors with high purity, smaller particles,and higher efficient luminescence. 展开更多
关键词 Synthesis Microwave field Submicrometer-sized CaS∶Cu+ Eu 2+ Fluorescence
在线阅读 下载PDF
Distribution and exploration direction of medium-and large-sized marine carbonate gas fields in Sichuan Basin, SW China 被引量:20
3
作者 MA Xinhua YANG Yu +1 位作者 WEN Long LUO Bing 《Petroleum Exploration and Development》 2019年第1期1-15,共15页
Based on the analysis of the basic characteristics of medium-and large-sized marine gas fields in Sichuan Basin, combined with the division of major reservoir forming geological units in the marine craton stage and th... Based on the analysis of the basic characteristics of medium-and large-sized marine gas fields in Sichuan Basin, combined with the division of major reservoir forming geological units in the marine craton stage and their control on key hydrocarbon accumulation factors, the distribution law of medium-and large-sized marine carbonate gas fields in the basin was examined and the exploration direction was pointed out. Through the analysis of the periodic stretching-uplifting background, it is concluded that five large scale paleo-rifts, three large scale paleo-uplifts, five large scale paleo erosion surfaces were formed in the marine craton stage of Sichuan Basin, and these geological units control the key reservoir forming factors of medium and large sized gas fields:(1) Large-scale paleo-rifts control the distribution of high-quality hydrocarbon generation centers.(2) The margin of large-scale paleo-rifts, high position of paleo-uplifts and paleo erosion surfaces control the distribution of high-quality reservoirs.(3) Large-scale paleo-rifts, paleo-uplifts, paleo erosion surfaces and present tectonic setting jointly control the formation of many types of large and medium-sized traps.(4) Natural gas accumulation is controlled by the inheritance evolution of traps in large geological units. Based on the comparative analysis of the distribution characteristics of medium-and large-sized gas fields and large geological units, it is proposed that the superimposition relationship between single or multiple geological units and the present structure controls the distribution of medium-and large-sized gas fields, and the "three paleo" superimposed area is the most advantageous. According to the above rules, the main exploration fields and directions of medium-and large-sized marine carbonate gas fields in Sichuan Basin include periphery of Deyang-Anyue paleo-rift, eastern margin of Longmenshan paleo-rift, margins of Kaijiang-Liangping oceanic trough and Chengkou-western Hubei oceanic trough, the high part of the subaqueous paleo-uplifts around Central Sichuan, paleo erosion surfaces of the top boundary of Maokou Formation in eastern and southern Sichuan Basin, paleo erosion surfaces of the top boundary of the Leikoupo Formation in central and western Sichuan Basin. 展开更多
关键词 Sichuan Basin marine CARBONATES medium-and large-sized gas fields GEOLOGIC unit reservoir forming factors paleo-rifts paleo-uplifts paleo erosion surfaces
在线阅读 下载PDF
Numerical analysis on the influence of rock specimen size on crack stress field
4
作者 傅真 蔡永恩 《Acta Seismologica Sinica(English Edition)》 EI CSCD 2005年第3期322-330,379,共10页
In the simulation of rupture processes of seismic sources by using either numerical method or rock mechanics experiments, improper setting of the specimen size will influence the stress field near the faults. In this ... In the simulation of rupture processes of seismic sources by using either numerical method or rock mechanics experiments, improper setting of the specimen size will influence the stress field near the faults. In this study, 2D finite element method (FEM) was used to calculate the stress field of rock specimens in different sizes with fixed-size elliptic holes. The calculated stress field was compared with analytic solution for elliptic-hole problem in an infinite medium. Numerical results showed that boundary effect of a rock specimen with an elliptic hole on stress field under uniaxial compression cannot be neglected. Critical aspect ratio of the specimen is about 3:2, and critical ratio of distance between the tip of the hole and the border of specimen (d) to the major axis of the elliptic hole (l) is about 7.3. Numerical analysis on rock specimen size can provide theoretical reference for rock specimen experiments, and it is also helpful for setting of model sizes in numerical simulations of fault movement. 展开更多
关键词 finite element method stress field critical size of rock specimen boundary effect
在线阅读 下载PDF
Simulation of size effects by a phase field model for fracture
5
作者 Charlotte Kuhn Ralf Müller 《Theoretical & Applied Mechanics Letters》 CAS 2014年第5期50-53,共4页
In phase field fracture models the value of the order parameter distin- guishes between broken and undamaged material. At crack faces the order param- eter interpolates smoothly between these two states of the materia... In phase field fracture models the value of the order parameter distin- guishes between broken and undamaged material. At crack faces the order param- eter interpolates smoothly between these two states of the material, which can be regarded as phases. The crack evolution follows implicitly from the time inte- gration of an evolution equation of the order parameter, which is coupled to the mechanical field equations. Among other phenomena phase field fracture mod- els are able to reproduce crack nucleation in initially sound materials. For a 1D setting it has been shown that crack nucleation is triggered by the loss of stability of the unfractured, spatially homogeneous solution, and that the stability point depends on the size of the considered structure. This work numerically investi- gates to which extend size effects are reproduced by the 2D phase field model. Exemplarily, a finite element study of the hole size effect is performed and the simulation results are compared to exnerimental data. 展开更多
关键词 phase field model fracture mechanics size effects STABILITY finite elementmethod
在线阅读 下载PDF
装配式临时道路大尺寸钢筋混凝土预制板受力试验研究
6
作者 王婧 李薇 刘大鹏 《粘接》 2026年第1期196-200,共5页
为提高大尺寸钢筋混凝土预制板的周转使用次数,进行了施工车辆在荷载作用下2 m×2 m×0.2 m预制板装配式临时道路的现场试验,测试了不同工况时预制板顶面和底面受到的水平应力和竖向应力,得到了预制板的应力时程曲线特征。研究... 为提高大尺寸钢筋混凝土预制板的周转使用次数,进行了施工车辆在荷载作用下2 m×2 m×0.2 m预制板装配式临时道路的现场试验,测试了不同工况时预制板顶面和底面受到的水平应力和竖向应力,得到了预制板的应力时程曲线特征。研究了车辆速度、车辆载重、接缝宽度和基层厚度对预制板最大水平应力和最大竖向应力的影响规律。结果表明,最大水平应力和最大竖向应力随车辆速度、车辆载重及接缝宽度的增大而增大,随基层厚度的增加而减小;当接缝宽度超过5 cm时,拱效应基本消失,二者趋于最大值;当基层厚度超过20 cm后,二者变化不再显著。为延长预制板的使用寿命,建议在工程中限制临时道路的车辆速度与载重,基层厚度宜控制在20 cm以内以便于后期拆除,同时接缝宽度宜取2 cm以保证拱效应的有效发挥。 展开更多
关键词 装配式 临时道路 预制板 大尺寸 现场试验
在线阅读 下载PDF
Mode-Field-Diameter and the Coupling Loss between Inner and Outer Segment of Photoreceptors 被引量:1
7
作者 Anhui Liang Leiting Hu Zhimin Liang 《Optics and Photonics Journal》 2015年第4期151-160,共10页
The characteristics of optical waveguide of human photoreceptors play important roles in vision. The mode-field-diameter (MFD) is a very important parameter of a single-mode waveguide, and it is related to many import... The characteristics of optical waveguide of human photoreceptors play important roles in vision. The mode-field-diameter (MFD) is a very important parameter of a single-mode waveguide, and it is related to many important optical characteristics of a single-mode waveguide. Here we show that MFDs of outer segments of human foveal cones are close to the minimum values at their geometric diameter for outer segments of foveal cones. Small MFD of outer segment is important for eyes to have high spatial resolution and low interaction between neighboring cones. We propose that the ellipsoids of foveal cones act as spot size converters to reduce the coupling losses between myoids and outer segments. 展开更多
关键词 PHOTORECEPTOR Mode-field-Diameter Spot size Converter Coupling
暂未订购
Effects of different levels of compost application on amounts and distribution of organic nitrogen forms in soil particle size fractions subjected mainly to double cropping 被引量:7
8
作者 Thu Ha Nguyen Haruo Shindo 《Agricultural Sciences》 2011年第3期213-219,共7页
Effects of different levels of compost application on the amounts and percentage distribution of organic N forms in whole soils and particle size fractions were investigated. Soil samples were collected from three plo... Effects of different levels of compost application on the amounts and percentage distribution of organic N forms in whole soils and particle size fractions were investigated. Soil samples were collected from three plots: (a) F, only chemical fertilizers;(b) F+LC, chemical fertilizers plus low level of compost;(c) F+HC, chemical fertilizers plus high level of compost. Each soil sample was divided into five fractions: coarse sand-sized aggregate (CSA), medium sand-sized aggregate (MSA), fine sand-sized aggregate (FSA), silt-sized aggregate (SIA) and clay-sized aggregate (CLA) fractions. The sand fractions were subdivided into decayed plants (DP) and mineral particles (MP). The amounts of total N and different organic N forms in the whole soils as well as size fractions generally increased with increasing the amount of compost. In the whole soils, percentage distribution of non-hydrolysable-N and amino sugar-N increased by compost application while the distribution values of the hydrolysable ammonium- N and unidentified-N decreased. The application did not affect the distribution degree of amino acid-N. In the size fractions, the distribution values of most organic N forms increased in the CSA-DP, MSA-DP and FSA-DP fractions by compost application. In the CLA fractions, the amounts and percentage distribution of organic N forms were the highest, although the application caused decreases in their distribution values. These findings indicate that the CLA fraction merit close attention as an important reservoir of various organic N. 展开更多
关键词 COMPOST APPLICATION UPLAND and PADDY fields Soil Organic N FORMS size FRACTIONS
暂未订购
Investigations of the Sheath Effect on the Resultant Magnetic Field of a Cylindrical Monopole Plasma Antenna
9
作者 Moses E.EMETERE 《Plasma Science and Technology》 SCIE EI CAS CSCD 2015年第2期153-158,共6页
The functionality of the plasma antenna has been narrowed to types and brand names only. The physics of its operation has been neglected and has stagnated technological innovations. The magnetic field in the sheath an... The functionality of the plasma antenna has been narrowed to types and brand names only. The physics of its operation has been neglected and has stagnated technological innovations. The magnetic field in the sheath and plasma were investigated. Notable specifications were worked out in the proposed improved cylindrical monopole plasma antenna. The occurrence of femto spin demagnetization was discovered between the duration of switch on and switch off of the antenna. This phenomenon seems transient because magnetization is highest at the switch on/off point. 展开更多
关键词 cylindrical monopole plasma antenna magnetic field size Schr6dinger SPIN
在线阅读 下载PDF
Influence of High Magnetic Field Annealing on Aicrostructure of Pulse-Electrodeposited Nanocrystalline Co-Ni-P Films
10
作者 LI Dong-gang WU Chun +2 位作者 WANG Qiang FRANCZAK Agnieszka HE Ji-cheng 《Journal of Iron and Steel Research International》 SCIE EI CAS CSCD 2012年第S2期1085-1088,共4页
The effects of high magnetic field armealihng on the morphology and texture of pulsed-electrodeposited Co-Ni-P films were investigated by field emission scanning electronic microscopy(FE-SEM),atomic force microscopy(A... The effects of high magnetic field armealihng on the morphology and texture of pulsed-electrodeposited Co-Ni-P films were investigated by field emission scanning electronic microscopy(FE-SEM),atomic force microscopy(AFM) and X-ray diffraction(XRD).The as-deposited film with cluster structural on a rough surface changed into non-uniform and bigger nanocrystalline during the no-field annealing due to a recrystallization process.Post-deposition annealing under a magnetic field favored to form a more homogeneous surface with smaller grain size and lower roughness.The magneto-induced a mixed phase structure including fcc-Ni,hcp-Co and fcc-CoNiP appeared in the case of the films annealed at a 9T magnetic field.The possible overlapping effects such as diffusion and recrystallization obtained by the magnetic field annealing on the morphology evolution and on the phase transformation in the films were interpreted. 展开更多
关键词 ELECTRODEPOSITION CoNiP films High magnetic field annealing Grain size Phase transformation
原文传递
Microscopic Phase Field Study of the Spinodal Decomposition in Fe-Mo Alloys
11
作者 朱景川 赵荣达 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2009年第S1期9-12,共4页
The spinodal decomposition in Fe-Mo alloys is studied by microscopic phase field method based on atomic scale.The results show that critical temperature of spinodal decomposition increases with the increment of Mo con... The spinodal decomposition in Fe-Mo alloys is studied by microscopic phase field method based on atomic scale.The results show that critical temperature of spinodal decomposition increases with the increment of Mo content,up to a maximum value of 1340 K at the Mo content of 50%.The spinodal decomposition shows a maximum rate at the Mo content of 50% for different Fe-Mo alloys.Comparing with the interconnected microstructure without considering elastic strain energy,the microstructure arrayed alternatively along the elastic soft direction of [01] and [10] is obtained under the effects of elastic strain energy,which will changes into a special 'macrolattice' structure during subsequent coarsening stages.The coarsening of microstructure is restrained by elastic interaction generated by atomic-size difference,and a larger atomic-size difference induces a stronger restraining effect. 展开更多
关键词 spinodal decomposition phase field Fe-Mo alloys atomic-size difference
原文传递
Particle Size Distributions and Organic-Inorganic Compositions of Suspended Particulate Matters Around the Bohai Strait
12
作者 WANG Xiao BIAN Changwei +3 位作者 BI Rong JIANG Wensheng ZHANG Hua ZHANG Xueqing 《Journal of Ocean University of China》 SCIE CAS CSCD 2017年第1期25-34,共10页
Laser in situ scattering and transmissometry(LISST) significantly improves our ability to assess particle size distribu-tion(PSD) in seawater, while wide-ranging measurements of the organic-inorganic compositions of s... Laser in situ scattering and transmissometry(LISST) significantly improves our ability to assess particle size distribu-tion(PSD) in seawater, while wide-ranging measurements of the organic-inorganic compositions of suspended particulate matters(SPM) are still difficult by using traditional methods such as microscopy. In this study, PSD properties and SPM compositions around the Bohai Strait(China) were investigated based on the measurements by LISST in combination with hydro-biological parameters collected from a field survey in summer 2014. Four typical PSD shapes were found in the region, namely right-peak, left-peak, dou-ble-peak and negative-skew shapes. The double-peak and negative-skew shapes may interconvert into each other along with strong hydrodynamic variation. In the upper layer of the Bohai Sea, organic particles were in the majority, with inorganic particles rarely observed. In the bottom layer, SPM were the mixture of organic and inorganic matters. LISST provided valuable baseline information on size-resolved organic-inorganic compositions of SPM: the size of organic particles mainly ranged from 4 to 20 μm and 40 to 100 μm, while most SPM ranging from 20 to 40 μm were composed of inorganic sediment. 展开更多
关键词 particle size distribution PHYTOPLANKTON SEDIMENT field survey Bohai SEA
在线阅读 下载PDF
Modeling and simulation of 3D thermal stresses of large-sized castings in solidification processes 被引量:2
13
作者 J.Q.Wang D.W.Yu +2 位作者 X.Sun S.F.Su B.Z.Li 《China Foundry》 SCIE CAS 2004年第S1期20-24,共5页
When heavy machines and large scaled receiver system of communication equipment are manufactured, it always needs to produce large-sized steel castings, aluminum castings and etc. Some defects of hot cracking by therm... When heavy machines and large scaled receiver system of communication equipment are manufactured, it always needs to produce large-sized steel castings, aluminum castings and etc. Some defects of hot cracking by thermal stress often appear during solidification process as these castings are produced, which results in failure of castings. Therefore predicting the effects of technological parameters for production of castings on the thermal stress during solidification process becomes an important means. In this paper, the mathematical models have been established and numerical calculation of temperature fields by using finite difference method (FDM) and then thermal stress fields by using finite element method (FEM) during solidification process of castings have been carried out. The technological parameters of production have been optimized by the results of calculation and the defects of hot cracking have been eliminated. Modeling and simulation of 3D thermal stress during solidification processes of large-sized castings provided a scientific basis, which promoted further development of advanced manufacturing technique. 展开更多
关键词 Large-sized castings simulation of 3D temperature fields simulation of 3D thermal stress fields defect of hot cracking solidification process
在线阅读 下载PDF
A NEW EXPRESSION OF FATIGUE SIZE FACTOR
14
作者 Yao Weixing(Department of Aircraft Engineering ,NUAA 29 Yudao Street,Nanjing 210016,P.R.China) 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 1994年第2期229-233,共5页
An expression describing the size effect on fatigue strength is presented, which is deduced based on the fatigue design approach of stress field intensity. The fatigue size factors under rotating-bending or reversed t... An expression describing the size effect on fatigue strength is presented, which is deduced based on the fatigue design approach of stress field intensity. The fatigue size factors under rotating-bending or reversed torsion for smooth specimen and under rotating-bending for notched specimen are estimated, and the main effects on the fatigue size factor are discussed. Some experimental data are analysed and it is shown that the description of fatigue size factor developed in this paper is satisfactory. 展开更多
关键词 FATIGUE size FACTOR FATIGUE mechanism stress field intensity rotating-bending reversed TORSION notched SPECIMEN
在线阅读 下载PDF
Successive defects asymmetric simple exclusion processes with particles of arbitrary size
15
作者 蔡九菊 肖松 +1 位作者 王若翚 刘飞 《Chinese Physics B》 SCIE EI CAS CSCD 2009年第12期5097-5102,共6页
This paper uses various mean-field approaches and the Monte Carlo simulation to calculate asymmetric simple exclusion processes with particles of arbitrary size in the successive defects system. In this system, the ho... This paper uses various mean-field approaches and the Monte Carlo simulation to calculate asymmetric simple exclusion processes with particles of arbitrary size in the successive defects system. In this system, the hopping probability p (p 〈 1) and the size d of particles are not constant, Through theoretical calculation and computer simulation, it obtains the exact theoretical results and finds that the theoretical results are in agreement with the computer simulation. These results are helpful in analysing the effect of traffic with different hopping probabilities p and sizes d of particle. 展开更多
关键词 successive defects asymmetric simple exclusion processes arbitrary size Monte Carlo simulation mean-field theory
原文传递
The Size of a Photon
16
作者 Richard A. Hutchin 《Optics and Photonics Journal》 2021年第5期121-131,共11页
This paper begins by exploring a useful and neglected detail of a photon—its physical size perpendicular to the direction of propagation in the same way as an atom or neutron has a physical size. Such a photon size w... This paper begins by exploring a useful and neglected detail of a photon—its physical size perpendicular to the direction of propagation in the same way as an atom or neutron has a physical size. Such a photon size would be quite separate from the cross-section of a photonic interaction, which depends on the material interacting. Such a perpendicular dimension of a photon will be invariant under Lorentz transform parallel to the light propagation direction and will thus be the same for all frequencies of light. This study also leads to new details about how a photon interacts, offering an explanation for the familiar physics where light slightly above and below the mean frequency of an excited state can still excite the same state without violation of conservation of energy—a mystery explored thoroughly in a previous paper without finding the solution offered here. As usual, a better elucidation of the details of light interaction also leads to new insights—especially about the vacuum field. The <strong>Appendix </strong>summarizes some previous research relevant to this 展开更多
关键词 Photon size Photon Energy Photon Excitation Vacuum field Red Shift
在线阅读 下载PDF
井下两级串联旋流器流场特性与分离性能分析
17
作者 蒋明虎 卢忠润 +3 位作者 邢雷 赵立新 刘琳 刘佳成 《化工机械》 2025年第1期52-59,188,共9页
采用数值模拟方法,以双泵抽吸式同井注采两级串联旋流器为研究对象,对不同含油浓度、油滴粒径和压降下的分离性能与流场特性进行分析。结果表明,增加含油浓度会使分离效率降低,含油浓度小于3%时,分离效率可保持在98%以上;当油滴粒径大于... 采用数值模拟方法,以双泵抽吸式同井注采两级串联旋流器为研究对象,对不同含油浓度、油滴粒径和压降下的分离性能与流场特性进行分析。结果表明,增加含油浓度会使分离效率降低,含油浓度小于3%时,分离效率可保持在98%以上;当油滴粒径大于0.25 mm时,分离效率可达95%以上;控制入口与底流口及溢流口的压差使两级串联旋流器的分流比在42%~44%范围内时分离效率相对较高,在96.2%~98.5%范围内变化。 展开更多
关键词 旋流器 流场特性 分离性能 油滴粒径 含油浓度
在线阅读 下载PDF
脉冲持续时间对凹球面聚焦超声换能器焦点大小的影响 被引量:1
18
作者 慕芸蔚 吴先梅 +2 位作者 李子琪 安秉文 冷涛 《声学学报》 北大核心 2025年第2期423-432,共10页
为实现更好的超声治疗效果和对目标区域的精准定位,研究了换能器的聚焦声场分布特性。通过对凹球面超声换能器聚焦声场的理论计算、仿真和实验验证,分析了不同脉冲持续时间的脉冲信号和连续正弦波信号作为激励信号对换能器横向声场和纵... 为实现更好的超声治疗效果和对目标区域的精准定位,研究了换能器的聚焦声场分布特性。通过对凹球面超声换能器聚焦声场的理论计算、仿真和实验验证,分析了不同脉冲持续时间的脉冲信号和连续正弦波信号作为激励信号对换能器横向声场和纵向声场特性的影响。结果表明,脉冲持续时间对于换能器横向声场的焦点尺寸基本没有影响,但对其纵向声场的焦点尺寸影响显著,随着脉冲持续时间的增加换能器纵向声场的焦点尺寸增加,且逐渐与连续正弦波下的换能器焦点尺寸接近。 展开更多
关键词 脉冲持续时间 聚焦声场 焦点大小 聚焦超声换能器
原文传递
高性能大尺寸金属构件增材制造研究进展
19
作者 方学伟 杨健楠 +6 位作者 周健 张垚 乔润基 冯佳劲 刘畅 黄科 卢秉恒 《制造技术与机床》 北大核心 2025年第10期13-34,共22页
针对大尺寸金属构件增材制造(additive manufacturing,AM)技术的研究现状与发展趋势,综述了该技术在航空航天、能源等领域的应用及其面临的挑战。首先,阐述了增材制造的基本原理及其在大尺寸金属构件中的优势与局限。其次,分析了增材制... 针对大尺寸金属构件增材制造(additive manufacturing,AM)技术的研究现状与发展趋势,综述了该技术在航空航天、能源等领域的应用及其面临的挑战。首先,阐述了增材制造的基本原理及其在大尺寸金属构件中的优势与局限。其次,分析了增材制造过程中工艺参数优化与智能控制技术的研究进展,特别是通过外场辅助调控、实时监测与自适应控制技术的应用,提高了制造过程的精度与稳定性。此外,重点讨论了针对大尺寸金属构件的在线与后处理形性同步调控技术,结合热处理与机械加工方法,有效改善了成形质量与力学性能。最后,展望了未来增材制造技术在大尺寸金属构件中的应用前景,提出了在工艺优化、材料特性、生产效率以及可持续发展等方面亟待解决的问题。研究表明,随着技术的不断进步,增材制造将在多个领域实现更广泛的应用,并推动传统制造模式的变革。 展开更多
关键词 大尺寸 金属增材 多场耦合 组织性能 过程控制 后处理
在线阅读 下载PDF
北潦河金家水支流江西大鲵野外种群现状及栖息地评估
20
作者 易木荣 卢萍 +16 位作者 彭勇 汤勇 许久恒 尹浩萍 张路杨 翁晓东 底明晓 雷隽 卢宸祺 曹如君 戴年华 占德洋 童媚 楼智明 丁永刚 柴静 车静 《生物多样性》 北大核心 2025年第4期28-36,共9页
濒危物种的有效保护依赖于基础调查研究和评估数据,并依此制定相应的保护行动计划。受栖息地破坏和人类过度捕捞影响,大鲵(Andrias spp.)野外种群稀少,同时由于基础研究数据缺乏,濒危程度的评估失去了科学基础。本研究于2021–2023年连... 濒危物种的有效保护依赖于基础调查研究和评估数据,并依此制定相应的保护行动计划。受栖息地破坏和人类过度捕捞影响,大鲵(Andrias spp.)野外种群稀少,同时由于基础研究数据缺乏,濒危程度的评估失去了科学基础。本研究于2021–2023年连续3年在江西靖安县北潦河金家水支流开展江西大鲵(A.jiangxiensis)野外种群的标志重捕调查与监测。累计目击成体、亚成体628尾次,其中带标记个体543尾次,至少重捕一次个体230尾次。综合分析结果显示:经标志重捕Schnabel模型估算,该种群大小为474尾(95%CI:427–534),种群密度为79尾/km (95%CI:71–89)和1.31尾/100 m^(2)(95%CI:1.19–1.48)。种群结构分析显示,体长大于70 cm或小于30 cm个体的数量极少。同时调查中多次目击到幼鲵、亚成体被天敌或同类残食;连续3年在9月或10月发现其野外繁殖场,1–3月累计目击记录新孵化幼鲵738尾次,4–12月全河段再次目击幼鲵的频率则极低(0.38尾·人^(–1)·h^(–1))。此外,栖息地评估提示江西大鲵面临较大的生存威胁:下游水坝的存在导致目前物种野外种群呈现隔离状态,有限的栖息地(3.6 ha)内环境波动剧烈,春夏丰水季洪水泛滥、自然坡岸塌方,秋冬枯水季河道干涸,断流频发。综上,本研究建议将江西大鲵的濒危等级评估为极危(CR),野外种群列为国家一级重点保护野生动物,亟待实施相应保护措施。 展开更多
关键词 濒危物种保护 野外调查 种群大小 致危因素 保护计划
原文传递
上一页 1 2 35 下一页 到第
使用帮助 返回顶部