期刊文献+
共找到8,967篇文章
< 1 2 250 >
每页显示 20 50 100
Hydro-wind Optimal Operation for Joint Bidding in Day-ahead Market: Storage Efficiency and Impact of Wind Forecasting Uncertainty 认领
1
作者 António Cerejo Sílvio J.P.S.Mariano +1 位作者 Pedro M.S.Carvalho Maria R.A.Calado 《现代电力系统与清洁能源学报(英文)》 SCIE EI CSCD 2020年第1期142-149,共8页
Wind power production is uncertain.The imbalance between committed and delivered energy in pool markets leads to the increase of system costs,which must be incurred by defaulting producers,thereby decreasing their rev... Wind power production is uncertain.The imbalance between committed and delivered energy in pool markets leads to the increase of system costs,which must be incurred by defaulting producers,thereby decreasing their revenues.To avoid this situation,wind producers can submit their bids together with hydro resources.Then the mismatches between the predicted and supplied wind power can be used by hydro producers,turbining or pumping such differences when convenient.This study formulates the problem of hydro-wind production optimization in operation contexts of pool market.The problem is solved for a simple three-reservoir cascade case to discuss optimization results.The results show a depreciation in optimal revenues from hydro power when wind forecasting is uncertain.The depreciation is caused by an asymmetry in optimal revenues from positive and negative wind power mismatches.The problem of neutralizing the effect of forecasting uncertainty is subsequently formulated and solved for the three-reservoir case.The results are discussed to conclude the impacts of uncertainty on joint bidding in pool market contexts. 展开更多
关键词 Optimization HYDRO POWER WIND POWER UNCERTAINTY JOINT BIDDING pool market
一种通过卷积─池化提升SVM人脸识别率的研究 认领
2
作者 叶晓波 秦海菲 吕永林 《楚雄师范学院学报》 2020年第3期106-114,共9页
以剑桥大学计算机实验室的ORL Faces数据库作为实验数据,通过卷积神经网络中的"卷积-池化"层对实验数据进行处理,选择LIBSVM集成软件为工具,对原始数据和经"卷积-池化"处理后的数据进行了分类识别研究,SVM参数选用C... 以剑桥大学计算机实验室的ORL Faces数据库作为实验数据,通过卷积神经网络中的"卷积-池化"层对实验数据进行处理,选择LIBSVM集成软件为工具,对原始数据和经"卷积-池化"处理后的数据进行了分类识别研究,SVM参数选用C-SVC模型、nu-SVC模型与线性核函数、多项式核函数、径向基核函数、Sigmoid核函数进行组合。实验结论:增加训练数据可提高人脸识别率,卷积-池化处理可实现数据降维,"高斯平滑卷积核卷积-池化"处理可提高SVM人脸识别率,SVM在人脸识别中更适合选用C-SVC模型+线性核函数。 展开更多
关键词 人脸识别 卷积 池化 SVM(支持向量机)
在线阅读 免费下载
池塘循环水养殖黄河鲤技术研究 认领
3
作者 季索菲 赵秀侠 +3 位作者 侯冠军 方婷 高远 王芬 《水产养殖》 CAS 2020年第7期1-5,共5页
该研究选择具有经济价值的水芹、空心菜、莲藕、水稻构建循环水系统对黄河鲤养殖尾水进行处理。研究表明,经植物循环水净化的水体,氨氮、磷含量均保持在黄河鲤健康生长的范围内。相对于传统养殖模式,循环水养殖系统换水量减少8倍,经济... 该研究选择具有经济价值的水芹、空心菜、莲藕、水稻构建循环水系统对黄河鲤养殖尾水进行处理。研究表明,经植物循环水净化的水体,氨氮、磷含量均保持在黄河鲤健康生长的范围内。相对于传统养殖模式,循环水养殖系统换水量减少8倍,经济效益提高11.2%,饵料系数降低15.24%、黄河鲤鱼生长速度提高14.9%。 展开更多
关键词 黄河鲤 循环水 植物净化 池塘
在线阅读 下载PDF
幽默小故事 认领
4
作者 周硕 《中学生英语》 2020年第29期32-33,共2页
Dolphins海豚Dolphins are so smart!Do you know what they can do in few weeks in a dolphinarium~1? They can train a man to stand at the edge~2 of the pool and throw them fish three times a day!海豚真聪明!你知道它们在海... Dolphins海豚Dolphins are so smart!Do you know what they can do in few weeks in a dolphinarium~1? They can train a man to stand at the edge~2 of the pool and throw them fish three times a day!海豚真聪明!你知道它们在海豚馆里的几个星期能做什么吗?它们可以训练一个人站在游泳池边上,每天向它们扔三次鱼! 展开更多
关键词 SMART 游泳池 POOL
在线阅读 下载PDF
Linear Stability Analysis of Thermocapillary Flow in Rotating Shallow Pools Heated from Inner Wall 认领
5
作者 TIAN Zu-an ZENG Zhong +3 位作者 LIU Hao YIN Linmao ZHANG Liangqi QIAO Long 《热科学学报:英文版》 SCIE EI CAS CSCD 2020年第1期251-259,共9页
Thermocapillary flow of silicon melt(Pr=0.011) in shallow annular pool heated from inner wall was simulated at the dimensionless rotation rate ω ranging from 0 to 7000. The effect of pool rotation on the stability of... Thermocapillary flow of silicon melt(Pr=0.011) in shallow annular pool heated from inner wall was simulated at the dimensionless rotation rate ω ranging from 0 to 7000. The effect of pool rotation on the stability of the thermocapillary flow was investigated. The steady axisymmetric basic state was solved by using the spectral element method;the critical stability parameters were determined by linear stability analysis;the mechanism of the flow instability was explored by the analysis of energy balance. A stability diagram, exhibiting the variation of the critical Marangoni number versus the dimensionless rotation rate ω was presented. The results reveal that only one Hopf bifurcation point appeared in the intervals of ω<3020 and ω>3965, and the corresponding instability was caused by the shear energy, which was provided by the thermocapillary force and pool rotation, respectively. In addition, the competition between thermocapillary force and pool rotation leads to three Hopf bifurcation points in the range of 3020<ω<3965 with the increase of Marangoni number. 展开更多
关键词 ANNULAR POOL THERMOCAPILLARY flow instability spectral element method linear stability analysis
LTE-G230电力无线专网组网研究与探索 认领
6
作者 仲立军 施敏达 +2 位作者 俞涯 顾君佳 沈旻 《农村电气化》 2020年第2期47-51,共5页
为满足电力业务接入需求,提升电力系统终端通信接入网接入能力,增强泛在电力物联网建设支撑能力,有必要对电力无线专网组网进行研究。文章以LTE-G 230无线专网技术为核心,针对电力系统业务需求和特点,对电力无线专网的组网方案进行了研... 为满足电力业务接入需求,提升电力系统终端通信接入网接入能力,增强泛在电力物联网建设支撑能力,有必要对电力无线专网组网进行研究。文章以LTE-G 230无线专网技术为核心,针对电力系统业务需求和特点,对电力无线专网的组网方案进行了研究。本文根据网络层级将电力无线专网分为五层,研究了核心网层、无线接入网层和上联业务主站的组网方式,并提出可行的接入方案,为电力无线专网建设提供指导意见。 展开更多
关键词 电力无线专网 MSC POOL CSS Super VLAN EPLAN 动态路由协议 静态路由协议
在线阅读 下载PDF
Soil carbon pools of six ecological regions of the United States 认领
7
作者 Amitava Chatterjee 《林业研究:英文版》 SCIE CAS CSCD 2020年第5期1933-1938,共6页
Mineralisable soil organic carbon(SOC)pools vary with ecosystem type in response to changes in climate,vegetation and soil properties.Understanding the effect of climate and soil factors on SOC pools is critical for p... Mineralisable soil organic carbon(SOC)pools vary with ecosystem type in response to changes in climate,vegetation and soil properties.Understanding the effect of climate and soil factors on SOC pools is critical for predicting change over time.Surface soil samples from six ecoregions of the United States were analyzed for permanganate oxidizable C(KMnO4-C)and mineralizable C pools.Variations of SOC ranged from 7.9 mg g^-1(Florida site)to 325 mg g^-1(Hawaii site).Mineralisable C pools and KMnO4-C were highest in soils from the Hawaii site.Mean annual precipitation explains SOC and resistant C pool variations.Clay content was related to mineralisable active C pools and bacterial abundance.Mean annual precipitation and clay content are potential variables for predicting changes in SOC pools at large spatial scales. 展开更多
关键词 Permanganate oxidizable carbon(KMnO4-C) Resistant carbon pool Mean residence time Soil carbon pools United States
在线阅读 下载PDF
Formation conditions and exploration direction of large natural gas reservoirs in the oil-prone Bohai Bay Basin, East China 认领
8
作者 XUE Yong’an WANG Deying 《石油勘探与开发:英文版》 2020年第2期280-291,共12页
The Bohai Bay Basin is a typical oil-prone basin, in which natural gas geological reserves have a small proportion. In this basin, the gas source rock is largely medium-deep lake mudstone with oil-prone type Ⅱ2-Ⅱ1 k... The Bohai Bay Basin is a typical oil-prone basin, in which natural gas geological reserves have a small proportion. In this basin, the gas source rock is largely medium-deep lake mudstone with oil-prone type Ⅱ2-Ⅱ1 kerogens, and natural gas preservation conditions are poor due to active late tectonic movements. The formation conditions of large natural gas fields in the Bohai Bay Basin have been elusive. Based on the exploration results of Bohai Bay Basin and comparison with large gas fields in China and abroad, the formation conditions of conventional large-scale natural gas reservoirs in the Bohai Bay Basin were examined from accumulation dynamics, structure and sedimentation. The results show that the formation conditions of conventional large natural gas reservoirs in Bohai Bay Basin mainly include one core element and two key elements. The core factor is the strong sealing of Paleogene "quilt-like" overpressure mudstone. The two key factors include the rapid maturation and high-intensity gas generation of source rock in the late stage and large scale reservoir. On this basis, large-scale nature gas accumulation models in the Bohai Bay Basin have been worked out, including regional overpressure mudstone enriching model, local overpressure mudstone depleting model, sand-rich sedimentary subsag depleting model and late strongly-developed fault depleting model. It is found that Bozhong sag, northern Liaozhong sag and Banqiao sag have favorable conditions for the formation of large-scale natural gas reservoirs, and are worth exploring. The study results have important guidance for exploration of large scale natural gas reservoirs in the Bohai Bay Basin. 展开更多
关键词 Bohai Bay Basin oil type lacustrine basin large nature gas pool Bozhong 19-6 regional"quilt-like"overpressure mudstone rapid and high-intensity gas generation in late period large scale reservoir
在线阅读 免费下载
SuPoolVisor:a visual analytics system for mining pool surveillance 认领
9
作者 Jia-zhi XIA Yu-hong ZHANG +7 位作者 Hui YE Ying WANG Guang JIANG Ying ZHAO Cong XIE Xiao-yan KUI Sheng-hui LIAO Wei-ping WANG 《信息与电子工程前沿:英文版》 SCIE EI CSCD 2020年第4期507-523,共17页
Cryptocurrencies represented by Bitcoin have fully demonstrated their advantages and great potential in payment and monetary systems during the last decade.The mining pool,which is considered the source of Bitcoin,is ... Cryptocurrencies represented by Bitcoin have fully demonstrated their advantages and great potential in payment and monetary systems during the last decade.The mining pool,which is considered the source of Bitcoin,is the cornerstone of market stability.The surveillance of the mining pool can help regulators effectively assess the overall health of Bitcoin and issues.However,the anonymity of mining-pool miners and the difficulty of analyzing large numbers of transactions limit in-depth analysis.It is also a challenge to achieve intuitive and comprehensive monitoring of multi-source heterogeneous data.In this study,we present SuPoolVisor,an interactive visual analytics system that supports surveillance of the mining pool and de-anonymization by visual reasoning.SuPoolVisor is divided into pool level and address level.At the pool level,we use a sorted stream graph to illustrate the evolution of computing power of pools over time,and glyphs are designed in two other views to demonstrate the influence scope of the mining pool and the migration of pool members.At the address level,we use a force-directed graph and a massive sequence view to present the dynamic address network in the mining pool.Particularly,these two views,together with the Radviz view,support an iterative visual reasoning process for de-anonymization of pool members and provide interactions for cross-view analysis and identity marking.Effectiveness and usability of SuPoolVisor are demonstrated using three cases,in which we cooperate closely with experts in this field. 展开更多
关键词 Bitcoin MINING POOL VISUAL ANALYTICS TRANSACTION data VISUAL REASONING FinTech
Acoustic emission detection of slag performance in coal gasifiers 认领
10
作者 Zhengliang Huang Peng Zhang +5 位作者 Yao Yang Jingyuan Sun JingdaiWang Yongrong Yang Chenghao Huang Zhixiong Huang 《中国化学工程学报:英文版》 SCIE EI CAS CSCD 2020年第8期2200-2207,共8页
This work first investigated the detection of slags,slag pool liquid level,and slag accumulation height in laboratory scale based on acoustic emission(AE)detection,and further tried the feasibility of this method in a... This work first investigated the detection of slags,slag pool liquid level,and slag accumulation height in laboratory scale based on acoustic emission(AE)detection,and further tried the feasibility of this method in an industrial scale coal gasifier.Results show that the energy and variance of acoustic signals can realize the accurate detection of large slag(criterion:E>1.5 E0,S>1.2 S0),and the average relative error is only 0.28%.The acoustic energy in the frequency range of 20–40 k Hz is defined as the characteristic energy,which can realize the accurate detection of slag accumulation height and slag pool liquid level,and the average relative error is only 3.94%.Furthermore,AE detection also realize accurate detection of large slag in an industrial scale gasifier and the acoustic signals at slag screen can be used to realize the early warning of the slag collapse(5 h earlier). 展开更多
关键词 Acoustic emission(AE)detection Slag pool liquid level Slag accumulation height Early warning
在线阅读 下载PDF
海南某市79家泳池消毒状况及卫生管理调查 认领
11
作者 胡高垚 林妍 +1 位作者 吴纪贞 龙文芳 《基层医学论坛》 2020年第25期3693-3695,共3页
目的了解某市泳池场所基本情况、泳池卫生消毒及管理状况,分析存在的问题及原因,为泳池卫生管理提出改进措施。方法通过现场监督及发放调查问卷、现场面对面访谈,对某市开放的79家游泳场所进行专项调查,对问卷进行统计分析。结果各泳池... 目的了解某市泳池场所基本情况、泳池卫生消毒及管理状况,分析存在的问题及原因,为泳池卫生管理提出改进措施。方法通过现场监督及发放调查问卷、现场面对面访谈,对某市开放的79家游泳场所进行专项调查,对问卷进行统计分析。结果各泳池有效卫生许可证持有率98.7%;泳池水质人工检测法占比11.4%,自动检测法占比88.6%;各泳池使用消毒剂概率为65.82%,另外臭氧消毒占比3.80%,紫外线消毒占比30.4%;泳池水更换频次最低为1~2次/季度或1~2次/年,占比率为41.8%,最高为1~2次/d,占比11.4%;浸脚池水消毒剂投加频次最高为1次/4h,占比40.5%,最低投加频次1次/6h,占比10.1%;直接法投加药剂占比最高为60.7%,混合法最低占比2.4%;不同类型泳池专职水质化验员的配备差异有统计学意义(P<0.05);不同类别泳池使用消毒剂的差异有统计学意义(P<0.05)。结论该市仍存在少数泳池卫生证件不完善,专业人员配备不足,消毒方式的选择及消毒剂的投加不当等问题,需要进一步对卫生许可证严格把关,配备完整的自检设备及专职水质化验员,规范卫生管理,安排专业的消毒人员对泳池及时换新水且投加适量的消毒剂,并加强泳池水消毒和泳池卫生监管工作。 展开更多
关键词 游泳场所 泳池 消毒 卫生管理
在线阅读 下载PDF
The importance of grain and cut-off size in shaping tree beta diversity along an elevational gradient in the northwest of Colombia 认领
12
作者 Johanna Andrea Martínez-Villa Sebastián González-Caro álvaro Duque 《森林生态系统:英文版》 SCIE CSCD 2020年第1期14-25,共12页
Background:Species turnover(β-diversity)along elevational gradients is one of the most important concepts in plant ecology.However,there is a lack of consensus about the main driving mechanisms of treeβ-diversity at... Background:Species turnover(β-diversity)along elevational gradients is one of the most important concepts in plant ecology.However,there is a lack of consensus about the main driving mechanisms of treeβ-diversity at local scales in very diverse ecosystems(e.g.,Andean mountains),as well as how the sampling effect can alterβ-diversity estimations.Recently,it has been hypothesized that patterns of change inβ-diversity at local scales along elevational gradients are driven by sampling effects stemming from differences in the size of the species pool rather than by underlying community assembly mechanisms.Thus,we aim to evaluate the relative extent to which sampling effects,such as species pool size,grain size,and tree size cut-off,determine species sorting,and thus,the variability ofβ-diversity at local scales along elevational gradients in the northwest of Colombia.Results:Using 151-ha permanent plots spread out along a 3000m elevational gradient,we used standardizedβ-deviation to assess the extent to which either sampling effects or the community assembly mechanisms determine the changes in species composition at local scales.Standardizedβ-deviation was measured as the difference between the observed and nullβ-diversity divided by the standard deviation of the nullβ-diversity.We found that the magnitude of change in localβ-deviation along the elevational gradient was significant and dependent on the employed spatial grain size and tree size cut-off.However,β-deviation increased with elevation in all sampling designs,which suggests that underlying community assembly mechanisms play a key role in shaping localβ-diversity along the elevational gradient.Conclusions:Our findings suggest that grain size enlargement and the inclusion of trees with small diameters will improve our ability to quantify the extent to which the community assembly mechanisms shape patterns ofβ-diversity along elevational gradients.Overall,we emphasize the scale-dependent nature of the assessment ofβ-diversity.Likewise,we call for 展开更多
关键词 Andean FORESTS NULL models SPECIES POOL SPECIES SORTING Sampling effect
在线阅读 下载PDF
New Formulation for Semi-Empirical Correlations for Penetration Jets 认领
13
作者 R. R. Pacheco L. O. Freire +3 位作者 M. S. Rocha N. L. Scuro M. O. Menezes D. A. Andrade 《核科学与技术国际期刊(英文)》 2019年第2期96-111,共16页
Correlations for the extension of a water vapor jet injected in a liquid pool were historically proposed considering the mass flux (kg/m2/s) as a constant. The results were satisfactory, however adjusting the values b... Correlations for the extension of a water vapor jet injected in a liquid pool were historically proposed considering the mass flux (kg/m2/s) as a constant. The results were satisfactory, however adjusting the values by linear regression. Although, it presents the following drawbacks: 1) the formulation is only valid for the specific range of data for what it was created;2) it does not allow the analytical evaluation of the heat transfer coefficient from the extension equation. This paper proposes a new formulation for the calculation of the mass flux, in such a way to remove both of these drawbacks. 展开更多
关键词 Direct Contact CONDENSATION Vapor JET STEAM JET STEAM Mass Flux Vapor Cavity REYNOLDS Number JET Radius Rate of CONDENSATION Non-Dimensional JET Length Liquid Pool DIMENSIONLESS Transport Modulus CONDENSATION Driving Potential
在线阅读 免费下载
Riverbank Erosional Features in the Stanley Pool of the Congo River and Some Geotechnical Classifications of the Sands 认领
14
作者 Guy Dieudonne Moukandi N’Kaya Narcisse Malanda +2 位作者 Olivier Florent Essouli Bernard Mabiala Alain Laraque 《地球科学和环境保护期刊(英文)》 2019年第5期152-167,共16页
The Stanley Pool, an almost circular island about thirty kilometers in diameter, crossed by the Congo River, is subject to diversified erosion of its riverbanks. This study highlights description using geotechnical pa... The Stanley Pool, an almost circular island about thirty kilometers in diameter, crossed by the Congo River, is subject to diversified erosion of its riverbanks. This study highlights description using geotechnical particle size distribution analysis of soils of the shoreline that make up the shoreline. Three critical areas of the island were examined to characterize the origins of these erosion phenomena. The results obtained show that the soil materials are mostly sands with very fine or fine grains characteristic of very unstable soils. The morpho-sedimentological characteristics of the areas studied show that these soils are plastic (with a Plasticity Index between 15 percent and 19 percent). The presence of water, action of currents or groundwater flow easily destabilize the materials that make up the riverbank and cause the fines to creep (Collapse of sandy riverbanks, Landslide of sandy riverbanks, …). 展开更多
关键词 Erosion Riverbanks CONGO RIVER Stanley POOL GEOTECHNICAL Analysis Particle Size Distribution
在线阅读 免费下载
VoLTE网络跨Pool容灾方案研究设计与实现 认领
15
作者 刘挺昕 侯华杰 马千 《电信工程技术与标准化》 2019年第2期23-28,共6页
核心网集中化、扁平化的组网特点,在实现资源共享、业务快速部署等方面具有优势的同时,机房、电源、承载网等环节成为核心网多网元同时故障的潜在隐患,网络传统的单板级、网元级、Pool级容灾技术和机制已无法应对其带来的重大影响。为... 核心网集中化、扁平化的组网特点,在实现资源共享、业务快速部署等方面具有优势的同时,机房、电源、承载网等环节成为核心网多网元同时故障的潜在隐患,网络传统的单板级、网元级、Pool级容灾技术和机制已无法应对其带来的重大影响。为了解决上述问题,通过多维风险分析和网络能力分析,提出容灾率算法,实现VoLTE网络Pool内资源容灾能力的量化判定。基于该算法构建跨Pool容灾模型,通过四级定损、场景预置、网络资源动态调用,实现VoLTE业务跨Pool网络容灾,强化VoLTE核心网容灾体系化保障能力,实现重大网络故障下的业务快速恢复。 展开更多
关键词 VoLTE POOL 容灾
在线阅读 下载PDF
Unlocked disinfection by-product formation potential upon exposure of swimming pool water to additional stimulants 认领
16
作者 Alvyn P.Berg Ting-An Fang Hao L.Tang 《中国环境科学与工程前沿:英文版》 SCIE EI CAS CSCD 2019年第1期111-118,共8页
Anthropogenic organics are known to be responsible for the formation of harmful disinfection byproducts (DBPs) in swimming pool water (SPW). The research explored an important scenario of SPW with no additional anthro... Anthropogenic organics are known to be responsible for the formation of harmful disinfection byproducts (DBPs) in swimming pool water (SPW). The research explored an important scenario of SPW with no additional anthropogenic organic input. With stimulations by residual chlorine or additional chlorine and extended incubation, the formation of DBPs, especially chlorofonn, was significantly induced. Similar observations were found by investigating synthetic SPW made with sweat and urine. The presence of urine led to a massive fbmiation of chloroform, as noted by an approximate 19-fbld increase after 165-day incubation with a shock chlorine dose. The research suggests that consistent residual chlorine and long water retention as two typical features of SPW could unlock the DBP fbnnation potential of anthropogenic organics. Thus, limiting the introduction of anthropogenic organics may not have an immediate effect on reducing DBP levels, because their reactions with chlorine can be slow and long-lasting. Pool management should prioritize on control of urine and improving air ventilation. This work is useful to deepen understandings about DBP formation in SPW and provide implications for pool management and prospective legislation. 展开更多
关键词 TRIHALOMETHANES Haloacetic acids CHLOROFORM Residual chlorine ANTHROPOGENIC ORGANICS SWIMMING pool water
一种CSFB业务双活问题的解决方案 认领
17
作者 柏洁 《信息通信》 2019年第2期252-253,共2页
CSFB是中国移动的一种过渡语音解决方案。在日常维护中,维护人员发现了一种CSFB业务双活现象,当CSFB用户在MSC POOL内其中一个端局有垃圾数据,且HSS中登记位置错误时,称为双活用户,双活用户主叫正常,但无法正常被叫。伴随CSFB用户快速发... CSFB是中国移动的一种过渡语音解决方案。在日常维护中,维护人员发现了一种CSFB业务双活现象,当CSFB用户在MSC POOL内其中一个端局有垃圾数据,且HSS中登记位置错误时,称为双活用户,双活用户主叫正常,但无法正常被叫。伴随CSFB用户快速发展,以及网络的频繁割接扩容,这种现象出现频率越来越高,严重影响了LTE语音业务感知。基于此,文章提出了一种CSFB业务双活问题的解决方案,在解决问题的同时,有效地提升了客户感知。 展开更多
关键词 客户感知 CSFB 业务双活 MSC POOL VOLTE
在线阅读 下载PDF
Analysis of weld pool vibration characteristics in pulsed gas metal arc welding 认领
18
作者 吕小青 张鹏 沈俊 《中国焊接:英文版》 EI CAS 2019年第4期28-32,共5页
Using highspeed camera image measuring and processing,the contour of the weld pool was extracted accurately in pulsed metal inert gas(P-MIG)welding.Based on this extraction method,time and frequency domain characteris... Using highspeed camera image measuring and processing,the contour of the weld pool was extracted accurately in pulsed metal inert gas(P-MIG)welding.Based on this extraction method,time and frequency domain characteristics at different points along the contour of the weld pool were analyzed for one pulse one droplet and one pulse two droplets,respectively.The results show that,because of the wave super position that was created by the pulsed arc and droplet impacting the weld pool,the oscillation amplitude along the weld pool fluctuated and decreased with an increase in distance from the point to the arc center.The oscillation near the arc center was complex and intense for one pulse two droplets,and the amplitude were relatively small because the oscillation caused by the pulsed arc could be offset by the molten droplet impact.The weld pool oscillation that was caused by the pulsed arc was stronger than that caused by the droplet. 展开更多
关键词 PULSED metal inert welding WELD POOL OSCILLATION interference time DOMAIN CHART frequency DOMAIN CHART
在线阅读 下载PDF
Numerical Investigation of Transient Temperature Distribution during Ti-6Al-4V Selective Laser Melting 认领
19
作者 XING Xiaodong ZHOU Qiuyu +2 位作者 WANG Shiyuan WANG Liquan JIANG Fengchun 《热科学学报:英文版》 SCIE EI CAS CSCD 2019年第2期370-377,共8页
The transient temperature field in the powder bed has a crucial effect on the quality of parts fabricated using Selective Laser Melting(SLM). In this study, a finite element model is established regarding the variance... The transient temperature field in the powder bed has a crucial effect on the quality of parts fabricated using Selective Laser Melting(SLM). In this study, a finite element model is established regarding the variance of temperature-dependent thermal properties and transformation latent heat. The temperature distribution and melt pool dimensions of a laser scan track were obtained by varying multiple parameters(layer thickness, laser power and scan speed). The effects of transition of material state and heat source model are also analyzed in this paper. The finite element simulation results show that an increased laser power and/or decreased scan speed results in an elevated maximum temperature of the powder layer and a larger melt pool size. Furthermore, it is found that the maximum temperature is significantly lowered due to the heat diffusion into the previous sintered zone. The heat source model has to be selected properly according to the element size. 展开更多
关键词 Selective Laser MELTING TRANSIENT temperature field process parameters MELT POOL
Anisotropy in mechanical properties and corrosion resistance of 316L stainless steel fabricated by selective laser melting 认领
20
作者 Xiao-qing Ni De-cheng Kong +5 位作者 Ying Wen Liang Zhang Wen-heng Wu Bei-bei He Lin Lu De-xiang Zhu 《矿物冶金与材料学报:英文版》 SCIE EI CAS CSCD 2019年第3期319-328,共10页
The corrosion behavior and mechanical properties of 316L stainless steel (SS) fabricated via selective laser melting (SLM) were clarified by potentiodynamic polarization measurements, immersion tests, and tensile expe... The corrosion behavior and mechanical properties of 316L stainless steel (SS) fabricated via selective laser melting (SLM) were clarified by potentiodynamic polarization measurements, immersion tests, and tensile experiments. The microstructural anisotropy of SLMed 316L SS was also investigated by electron back-scattered diffraction and transmission electron microscopy. The grain sizes of the SLMed 316L SS in the XOZ plane were smaller than those of the SLMed 316L SS in the XOY plane, and a greater number of low-angle boundaries were present in the XOY plane, resulting in lower elongation for the XOY plane than for the XOZ plane. The SLMed 316L was expected to exhibit higher strength but lower ductility than the wrought 316L, which was attributed to the high density of dislocations. The pitting potentials of the SLMed 316L samples were universally higher than those of the wrought sample in chloride solutions because of the annihilation of MnS or (Ca,Al)-oxides during the rapid solidification. However, the molten pool boundaries preferentially dissolved in aggressive solutions and the damage of the SLMed 316L in FeCl3 solution was more serious after long-term service, indicating poor durability. 展开更多
关键词 selective laser MELTING mechanical property corrosion resistance 316L STAINLESS steel ANISOTROPY MOLTEN POOL boundary
在线阅读 下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部 意见反馈