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Ultra-deep desulfurization by reactive adsorption desulfurization on copper-based catalysts 预览
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作者 Yaqing Liu Hongying Wang +2 位作者 Jinchong Zhao Yunqi Liu Chenguang Liu 《能源化学:英文版》 SCIE EI CAS CSCD 2019年第2期8-16,共9页
In this paper,a novel copper-based catalyst for FCC gasoline improving the ability of removal the sulfur and avoiding the loss of the octane number from olefin saturation by reactive adsorption desulfurization(RADS) w... In this paper,a novel copper-based catalyst for FCC gasoline improving the ability of removal the sulfur and avoiding the loss of the octane number from olefin saturation by reactive adsorption desulfurization(RADS) was investigated.The series of Cu/Zn O-Al2 O3 catalysts were characterized by X-ray powder diffraction(XRD),N2 adsorption analysis and temperature-programmed reduction(TPR) studies,X-ray photoelectron spectroscopy(XPS),scanning electron microscope(SEM) and transmission electron microscopy(TEM).The experiment results showed that the catalysts had an optimum desulfurization ability with copper loading 6 wt%,which the sulfur contents of product decreased less than 10 μg/g and olefin contents decreased from 16.19% to 14.14% for the long period operation.The appropriate Cu loading content could lead to the high active and low apparent activation energy(Ea).Therefore,the Cu-based catalyst may become a novel catalyst for second-generation for reactive adsorption desulfurization,which achieves the high desulfurization active and low olefins saturation to satisfy the upgrading the product. 展开更多
关键词 Cu/ZnO-Al2O3 DESULFURIZATION activity OCTANE number OLEFINS SATURATION Stability
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Smart homing guidance strategy with control saturation against a cooperative target-defender team 预览
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作者 GUO Hang FU Wenxing +2 位作者 FU Bin CHEN Kang YAN Jie 《系统工程与电子技术:英文版》 SCIE EI CSCD 2019年第2期366-383,共18页
A smart homing guidance strategy with control saturation against a target-defender team is derived. It is noteworthy that a cooperative strategy of the target-defender team is applied,which has been proved more challe... A smart homing guidance strategy with control saturation against a target-defender team is derived. It is noteworthy that a cooperative strategy of the target-defender team is applied,which has been proved more challenging for the homing guidance.The defender missile is launched by the target and guided by a cooperative augmented proportional navigation(APN). At the same time, the target performs a one-switch maneuver to cooperate and minimize the defender’s acceleration requirement. The problem is analyzed for arbitrary-order linear dynamics of the agents in the linearized form but validated by the mathematical simulations by using nonlinear kinematics. The perfect information of three agents’ states is assumed. Then, a method to deal with the target-defender team is proposed. It contains a combined performance index penalizing the miss distance relative to the target and energy consumption in the whole duration. Besides, the specific miss distance related to the defender is regarded as an inequality constraint. An analytical solution for the smart guidance strategy against the APN guided defender is derived. Meanwhile, the control saturations are introduced to get more realistic and reasonable insights to this practical target-missile-defender problem. A simple but effective iterative searching technique is proposed to determine the saturation time points. The solution provides an optimal homing strategy to evade the defender with a specific miss distance and intercept the target with the minimum miss distance in the minimum energy manner. Nonlinear two-dimensional simulation results are used to validate the theoretical analysis. By comparison with the optimal differential game guidance(ODGG) and the combined minimum effort guidance(CMEG), the superiority of this smart guidance strategy is concluded. 展开更多
关键词 SMART HOMING guidance control SATURATION targetmissile-defender ITERATIVE SEARCHING technique
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自动重合闸期间电流互感器剩磁抑制研究
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作者 段建东 金转婷 +4 位作者 雷阳 张小庆 张宜阳 李云阁 左宝峰 《中国电机工程学报》 EI CSCD 北大核心 2019年第5期1498-1505,共8页
P级电流互感器广泛用于330kV及以下电力系统,由于其暂态性能差,在铁心中留存大量剩磁。随着电网短路水平增大,电流互感器更易饱和,造成与之相连的继电保护误动。为此,该文提出一种适用于自动重合闸期间的电流互感器剩磁快速抑制方法。... P级电流互感器广泛用于330kV及以下电力系统,由于其暂态性能差,在铁心中留存大量剩磁。随着电网短路水平增大,电流互感器更易饱和,造成与之相连的继电保护误动。为此,该文提出一种适用于自动重合闸期间的电流互感器剩磁快速抑制方法。该方法由连接在电流互感器二次侧的剩磁抑制电路实现,通过控制开关模块输出电压的极性来逐渐减小铁心的磁通。给出剩磁抑制电路中开关模块输出电压反转次数、直流电压值以及限流电阻的选择方法。利用典型电流互感器参数及其在自动重合闸期间的动态模拟实验数据,进行不同剩磁极性、不同短路电流情况下的测试,结果显示所提出的剩磁抑制方法及其抑制电路是可行的、快速的,并且性能优越。 展开更多
关键词 电流互感器 自动重合闸 剩磁 抑制 动态模拟 饱和
土体热传导性能及其热导率模型研究 预览
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作者 张涛 刘松玉 +2 位作者 张楠 段隆臣 蔡国军 《建筑材料学报》 EI CAS CSCD 北大核心 2019年第1期72-80,共9页
为研究不同土体的热传导特性变化规律,利用热探针测试了南京地区典型土体在不同含水量和干密度状态下的热阻系数,分析了含水量、干密度、饱和度以及矿物成分等因素对土体热阻系数的影响,研究了不同状态下土体热导率的预测模型,提出了适... 为研究不同土体的热传导特性变化规律,利用热探针测试了南京地区典型土体在不同含水量和干密度状态下的热阻系数,分析了含水量、干密度、饱和度以及矿物成分等因素对土体热阻系数的影响,研究了不同状态下土体热导率的预测模型,提出了适用于不同地区土体热阻系数估算的修正系数.结果表明:南京地区典型土体的热阻系数随含水量和干密度增加而减小,当含水量超过一定范围后,热阻系数趋于稳定;热阻系数与饱和度之间的关系表现出与其含水量之间相似的变化规律;土颗粒的热传导特性由其矿物成分决定,石英含量对土颗粒热传导特性有着显著影响;提出了可用于非饱和土热导率估算的修正归一化模型,该模型对于粗粒土具有较高的预测精度,细粒土则需考虑区域差别进行修正. 展开更多
关键词 热传导 饱和度 矿物成分 非冻土 归一化模型
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裂隙充填型天然气水合物储层的各向异性饱和度新估算及其裂隙定量评价
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作者 钱进 王秀娟 +2 位作者 董冬冬 SAINKalachand 叶月明 《地球物理学进展》 CSCD 北大核心 2019年第1期354-364,共11页
天然气水合物有时会以结核状、层状、脉状或块状等裂隙形态发育在深水盆地的细粒泥质沉积物中,该类型天然气水合物被称为裂隙充填型.与孔隙充填型不同,裂隙充填型天然气水合物储层由于裂隙的出现,在测井速度、电阻率和地震数据上会呈现... 天然气水合物有时会以结核状、层状、脉状或块状等裂隙形态发育在深水盆地的细粒泥质沉积物中,该类型天然气水合物被称为裂隙充填型.与孔隙充填型不同,裂隙充填型天然气水合物储层由于裂隙的出现,在测井速度、电阻率和地震数据上会呈现明显的各向异性特征.本文利用细层层状介质模型和有效介质理论(EMT)新估算出印度克里希纳—戈达瓦里(K-G)盆地NGHP-01-10A和10D孔裂隙充填型水合物储层的各向异性饱和度,纵波(Vp)和垂直极化横波(Vsv)测井速度估算的平均饱和约为20%,明显优于水平极化横波(Vsh)估算结果,且与压力取心估算结果更为一致.倾角随深度变化曲线和不同角度估算的水合物饱和度结果都表明10A孔浅部以高倾角裂隙为主,深部出现低倾角裂隙;10D孔以垂直裂隙为主,这说明两口相距10 m的孔中裂隙在空间上延伸长度较小;而10B-08Y岩心的X射线成像定量评价结果显示水平裂隙倾角位于0°~21°,高倾角裂隙倾角位于68°~89°,裂隙尺度为厘米级,最大高度、宽度和纵横比分别为27.66 cm、6.71 cm和170.此外,水合物饱和度估算的影响因素分析表明,地层岩性和方程计算参数对饱和度估算的准确与否至关重要,与简化三相方程相比,有效介质理论计算参数的物理意义明确,参数选择简易,因此计算也更为准确与便捷. 展开更多
关键词 裂隙充填型天然气水合物 有效介质理论 裂隙定量评价 各向异性 饱和度
Effect of retained austenite and nonmetallic inclusions on the thermal/electrical properties and resistance spot welding nuggets of Si-containing TRIP steels 预览
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作者 V.H.Vargas I.Mejía +1 位作者 V.H.Baltazar-Hernández C.Maldonado 《矿物冶金与材料学报:英文版》 SCIE EI CAS CSCD 2019年第1期52-63,共12页
Five advanced high-strength transformation-induced plasticity(TRIP)steels with different chemical compositions were studied to correlate the retained austenite and nonmetallic inclusion content with their physical pro... Five advanced high-strength transformation-induced plasticity(TRIP)steels with different chemical compositions were studied to correlate the retained austenite and nonmetallic inclusion content with their physical properties and the characteristics of the resistance spot welding nuggets.Electrical and thermal properties and equilibrium phases of TRIP steels were predicted using the JMatPro software.Retained austenite and nonmetallic inclusions were quantified by X-ray diffraction and saturation magnetization techniques.The nonmetallic inclusions were characterized by scanning electron microscopy.The results show that the contents of Si,C,Al,and Mn in TRIP steels increase both the retained austenite and the nonmetallic inclusion contents.We found that nonmetallic inclusions affect the thermal and electrical properties of the TRIP steels and that the differences between these properties tend to result in different cooling rates during the welding process.The results are discussed in terms of the electrical and thermal properties determined from the chemical composition and their impact on the resistance spot welding nuggets. 展开更多
关键词 transformation-induced plasticity steel retained austenite non-metallic inclusions magnetic saturation electrical PROPERTIES THERMAL PROPERTIES resistance spot welding NUGGET
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光纤纵联保护装置在企业配网线路的应用分析 预览
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作者 刘艳芬 《包钢科技》 2019年第1期87-90,共4页
文章介绍了三种近年来在企业中压配电系统中应用的微机型线路光纤纵联保护装置,针对企业中压配电系统的特点,分别阐述了电流互感器饱和对保护装置启动值的影响以及保护对通讯的要求,最后对企业中压配电系统设备选择以及光纤纵联保护装... 文章介绍了三种近年来在企业中压配电系统中应用的微机型线路光纤纵联保护装置,针对企业中压配电系统的特点,分别阐述了电流互感器饱和对保护装置启动值的影响以及保护对通讯的要求,最后对企业中压配电系统设备选择以及光纤纵联保护装置的通道维护给出了建议,对实际工作具有一定的指导意义。 展开更多
关键词 光纤纵联保护 启动值 电流互感器 饱和 通讯
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Controlling nested wrinkle morphology through the boundary effect on narrow-band thin films
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作者 Hanyang XU Tielin SHI +1 位作者 Guanglan LIAO Qi XIA 《机械工程前沿:英文版》 CSCD 2019年第2期235-240,共6页
We describe the formation of nested wrinkles created by the thermal mismatch between a narrow-band thin film and a compliant substrate.When a film is described as"narrow-band",it literally means that the fil... We describe the formation of nested wrinkles created by the thermal mismatch between a narrow-band thin film and a compliant substrate.When a film is described as"narrow-band",it literally means that the film band width is much shorter than its length;more precisely,it means that the width is comparable with the wavelength of the wrinkles.A silicon mask was used during film sputtering to create narrow-band films on poly(dimethylsiloxane)substrate,thus creating regular boundaries to steer local stresses and control wrinkle morphology.Disordered nano-scale wrinkles were found nested within highly ordered micro-scale sinusoidal wrinkles.The formation of nested wrinkles was explained through the amplitude and wavelength saturation of nano-scale wrinkles.The disordered morphology of nano-scale wrinkles and the highly ordered morphology of microscale wrinkles were explained by using the boundary effect. 展开更多
关键词 nested and hierarchical WRINKLES MORPHOLOGY AMPLITUDE SATURATION boundary effect
基于阻抗特征煤体中瓦斯因素对水合动力学的影响
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作者 张强 吴强 +2 位作者 张辉 张保勇 刘传海 《工程热物理学报》 EI CAS CSCD 北大核心 2019年第2期414-422,共9页
为研究不同瓦斯赋存条件下水合机理防治煤与瓦斯突出的基础规律,利用阻抗特性监测与高压瓦斯水合实验一体化装置,针对4种瓦斯气体分别在4种赋存压力(4 MPa,5 MPa,6 MPa,7 MPa)条件下开展煤体中瓦斯水合实验,根据阻抗特征获取了瓦斯水合... 为研究不同瓦斯赋存条件下水合机理防治煤与瓦斯突出的基础规律,利用阻抗特性监测与高压瓦斯水合实验一体化装置,针对4种瓦斯气体分别在4种赋存压力(4 MPa,5 MPa,6 MPa,7 MPa)条件下开展煤体中瓦斯水合实验,根据阻抗特征获取了瓦斯水合物形成诱导时间,计算了煤体中瓦斯水合物生长速率与饱和度。结果表明:煤体中瓦斯水合过程中上层位与中层位阻抗逐渐增大,下层位阻抗逐渐减小,瓦斯水合物主要分布于上层位与中层位煤体中;随初始压力变化瓦斯水合物形成诱导时间未呈现规律性变化,随着混合气中CH4浓度的下降,诱导时间先减小后增大,实验范围内平均诱导时间为41 min,分布范围为18~74 min;随初始压力与瓦斯气体组分浓度的变化煤体中瓦斯水合物平均生长速率呈振荡变化趋势,平均生长速率均值为0.58 cm3·min-1,最快为0.84 cm3·min-1;煤体中瓦斯水合物的饱和度随初始压力与瓦斯中CH4浓度的增大呈逐渐升高的变化趋势,水合物饱和度范围为17.03%~57.03%。 展开更多
关键词 瓦斯 水合物 阻抗 动力学参数 饱和度
Shear strength of extremely altered serpentinites based on degree of saturation(Ankara, Turkey)
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作者 Koray ULAMIs 《山地科学学报:英文版》 SCIE CSCD 2019年第4期944-954,共11页
The term 'mélange' has several definitions due to the origin, tectonic and petrographical features. The geotechnical engineering behaviors of mélanges are either dominated by different kinds of intac... The term 'mélange' has several definitions due to the origin, tectonic and petrographical features. The geotechnical engineering behaviors of mélanges are either dominated by different kinds of intact rock blocks or matrix material. Landslides were encountered within the serpentinite matrix of Ankara Mélange, which is a typical bimrock mass. The residual sections of the extremely altered serpentinites are sandy soils. Such soils undergo rapid change of saturation, leading to shear strength reduction. Undisturbed and disturbed samples were obtained from the outcrops for shear box tests. Geochemical and petrographical composition of the serpentinites were determined by XRF(X Ray Fluorescence), XRD(X-ray diffraction) and thin section inspections, in order to outline the alteration process. Based on field observations, physically decomposed core stones exist beneath 40-120 cm thick residual green and grey-dark grey residual sandy soil. Physical and mechanical properties of the soils were tested with particular emphasis on residual shear strength parameters. Disturbed samples were remolded by standard compaction. The field work was completed during both rainy and summer seasons. Disturbed samples were prepared using phase diagrams in order to attain varying saturation degree. Two distinct sandy soil groups were determined through classification tests. The volumetric compression and/or expansion of the loose and dense samples were also considered based on the angle of dilatancy. A series of consolidated and drained shear box tests were conducted with ascending degree of saturation. The reduction of effective apparent cohesion, internal friction angle and dilatancy angle were determined to obtain a threshold of the degree of saturation. All the sand samples had zero residual internal friction angle and/or apparent cohesion after reaching 70% degree of saturation. 展开更多
关键词 MÉLANGE SERPENTINITE Shear strength Saturation DILATANCY ANKARA
秭归地区陆源碎屑岩导热系数试验研究
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作者 乔宇 骆进 +3 位作者 项伟 黄维 郭清海 张琦 《地质科技情报》 CAS CSCD 北大核心 2019年第1期82-89,共8页
岩土体的导热系数是重要的物理参数,在岩土工程中有着广泛应用。秭归地区的黄陵背斜西翼是我国南方著名的标准地层剖面,以秭归地区黄陵背斜西翼岩层陆源碎屑岩为研究对象开展导热系数试验研究,可为我国南方地区开展地热能开发、隧道工... 岩土体的导热系数是重要的物理参数,在岩土工程中有着广泛应用。秭归地区的黄陵背斜西翼是我国南方著名的标准地层剖面,以秭归地区黄陵背斜西翼岩层陆源碎屑岩为研究对象开展导热系数试验研究,可为我国南方地区开展地热能开发、隧道工程及矿产开采等科研工作提供重要的参考依据。探究了各岩层岩石导热系数与岩石颗粒组分、胶结物之间的变化规律及差异性。试验结果表明,黄陵背斜西翼陆源碎屑岩导热系数差异较大,在0.72~4.47 W/(m·K)之间,且导热系数大小为石英砂岩>粉砂岩>泥岩。陆源碎屑岩导热系数受岩石岩性、颗粒组分、粒径、胶结类型及含水状态的影响较大。 展开更多
关键词 黄陵背斜西翼 陆源碎屑岩 导热系数 饱和度
Adaptive Backstepping Control for Hypersonic Vehicles with Actuator Amplitude and Rate Saturation 预览
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作者 XIANG Kai DU Yanli +1 位作者 ZHANG Peng LIN Haibing 《南京航空航天大学学报:英文版》 EI CSCD 2019年第2期242-252,共11页
This paper presents a constrained control strategy for the hypersonic vehicle with actuator amplitude,rate constraints and aerodynamic uncertainties.First,a vehicle-actuator control model is derived in consideration o... This paper presents a constrained control strategy for the hypersonic vehicle with actuator amplitude,rate constraints and aerodynamic uncertainties.First,a vehicle-actuator control model is derived in consideration of actuator dynamics properties explicitly.Second,a nonlinear disturbance observer is designed to estimate the aerodynamic uncertainties,and then an adaptive backstepping control technique is adopted with a modified first-order-filter to eliminate the“explosion of terms”problem.Next,for handling the actuator amplitude and rate constraints,a novel auxiliary compensation system is constructed to generate quickly compensating signals to ensure tracking performance of command signal.By the Lyapunov stability proof,the proposed control scheme can enssure that the tracking errors converge to an arbitrarily small neighborhood around zero when the actuator constraints and aerodynamic uncertainties exist.Finally,numerical simulations are implemented to illustrate the effectiveness of the proposed control method. 展开更多
关键词 HYPERSONIC vehicle AMPLITUDE and RATE SATURATION adaptive BACKSTEPPING aerodynamic uncertainty
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土石复合介质电阻率变化特性研究 预览
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作者 王日升 赵明阶 王日强 《建筑材料学报》 EI CAS CSCD 北大核心 2019年第1期94-100,共7页
在最佳含水率条件下制备了土石比(质量比)分别为9∶1,7∶3,5∶5,4∶6,压实度分别为90%,92%,95%,98%,100%的20个多相土石复合介质试件,通过测定各试件在吸水饱和过程中的电阻率变化,明确了其变化过程与土石比、压实度等物理参数间的响应... 在最佳含水率条件下制备了土石比(质量比)分别为9∶1,7∶3,5∶5,4∶6,压实度分别为90%,92%,95%,98%,100%的20个多相土石复合介质试件,通过测定各试件在吸水饱和过程中的电阻率变化,明确了其变化过程与土石比、压实度等物理参数间的响应规律及产生原因,同时将饱水过程中压实度与饱和度指标进行关联,最后采用非饱和岩石电阻率饱和度关系模型对土石复合介质电阻率随饱和度变化规律进行了拟合,拟合结果总体良好.所得结果可为利用电阻率来检测土石坝坝体材料吸水饱和形成的渗漏通道提供数据支撑. 展开更多
关键词 土石复合介质 压实度 饱和度 电阻率
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Analysis of drying and saturating natural gypsum samples for mechanical testing 预览
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作者 Mohammadhossein Sadeghiamirshahidi Stanley J.Vitton 《岩石力学与岩土工程学报:英文版》 CSCD 2019年第2期219-227,共9页
The stability of underground abandoned gypsum mines is dependent on the gypsum pillar’s strength,and most abandoned mines are in a fully saturated condition.Moisture affects the strength of gypsum and is therefore co... The stability of underground abandoned gypsum mines is dependent on the gypsum pillar’s strength,and most abandoned mines are in a fully saturated condition.Moisture affects the strength of gypsum and is therefore commonly measured when testing rock strength.For most rocks,this is a simple task of weighing the rock’s mass before and after oven-heating at a specified temperature and duration.For natural gypsum,however,this is not a straightforward process.Heating natural gypsum can result in dehydration and transformation of gypsum to hemihydrate and anhydrite,thus changing the physical characteristics of the gypsum such as its particle density which in turn affects the moisture content and strength measurements.To prevent transformation when determining the moisture content of gypsum,the American Society for Testing Materials(ASTM)recommends lowering the drying temperature from 110℃to 60℃.To investigate the temperature at which gypsum transforms to hemihydrate,we used a helium pycnometer to measure the particle densities of gypsum,hemihydrate and anhydrite.In this research,we suggest that a higher drying temperature of 80℃can be used for drying gypsum without transforming gypsum to hemihydrate.Further,preparing saturated samples for mechanical testing,which is required in stability analyses of abandoned mines,is challenging due to the dissolution of gypsum when placed in water.To address this problem,we investigated the following methods to saturate gypsum cores taking into account the solubility of gypsum:(1)water immersion,(2)vacuum saturation,and(3)improved vacuum saturation.The research indicates that all the three methods are acceptable but they should be conducted using a saturated gypsum-water solution to minimize dissolution.Further,the research found that the improved vacuum saturation method saturated the test samples within 24 h,while duration of 30 h was required for the other two methods. 展开更多
关键词 Gypsum-hemihydrate-anhydrite transformation DEHYDRATION Rock core SATURATION Moisture content HELIUM PYCNOMETER
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Absorption saturation measurement using the tapered optical nanofiber in a hot cesium vapor
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作者 宋子旋 岳星宇 +2 位作者 罗宇 李好东 赵延霆 《中国光学快报:英文版》 SCIE EI CAS CSCD 2019年第3期71-74,共4页
We report the observation of ultralow-power absorption saturation in a tapered optical fiber(TOF) mounted in a hot cesium(Cs) vapor in a vacuum chamber. The small optical mode area of TOF produces a great influence on... We report the observation of ultralow-power absorption saturation in a tapered optical fiber(TOF) mounted in a hot cesium(Cs) vapor in a vacuum chamber. The small optical mode area of TOF produces a great influence on optical properties, allowing optical interactions with nanowatt-level power. The comparison of transmission characteristics for the TOF system and free-space vapor is investigated at different input power and atomic density. The unique performance of the Cs-TOF system makes it a promising candidate in resonant nonlinear optical applications with ultralow power. 展开更多
关键词 Absorption SATURATION MEASUREMENT tapered OPTICAL NANOFIBER CESIUM vapor
长江上游典型农业源溪流溶存氧化亚氮(N2O)浓度特征及影响因素
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作者 田琳琳 王正 +2 位作者 胡磊 任光前 朱波 《环境科学》 EI CAS CSCD 北大核心 2019年第4期1939-1949,共11页
随着农业非点源氮(N)污染的加剧,农田周边溪流成为重要的活性N汇和潜在的氧化亚氮(N2O)排放源.为查明长江上游农业源溪流中溶存N2O浓度的全年动态变化特征,于2014年12月~2015年10月开展紫色土丘陵区典型农田源头溪流N2O浓度的连续采样观... 随着农业非点源氮(N)污染的加剧,农田周边溪流成为重要的活性N汇和潜在的氧化亚氮(N2O)排放源.为查明长江上游农业源溪流中溶存N2O浓度的全年动态变化特征,于2014年12月~2015年10月开展紫色土丘陵区典型农田源头溪流N2O浓度的连续采样观测,采用水-气顶空平衡-气相色谱法测定顶空气体中N2O浓度,根据相关参数计算出本研究水体中的溶存N2O浓度,并同步测定溪流水体物理化学指标,分析水中溶存N2O浓度的主要影响因素.结果表明,长江上游紫色土丘陵区的典型农业源溪流的硝态氮(NO3^--N)是最主要的活性N赋存形态(年均1.45 mg·L^-1),溪流水体溶存N2O质量浓度(以N计)全年平均为0.57μg·L^-1(范围0.26~1.28μg·L^-1),冬、春、夏和秋季的均值分别为0.63、0.45、0.53和0.64μg·L^-1,但季节间无显著差异.溪流水体溶存N2O浓度全年都处于过度饱和状态(饱和度年平均为203.9%,范围109.7%~546.5%),可见,农业源溪流全年均为潜在的N2O释放源.溪流溶存N2O浓度的变化主要由水体NO3^--N浓度决定,N2O的主要产生机制为反硝化作用;溪流季节平均N2O饱和度在夏、秋季显著高于冬、春季,水中溶存N2O饱和度的变化主要受水温和NO3^--N浓度的共同影响.研究还发现农业源溪流中溶存N2O浓度在4~10月(湿润季节)间波动明显,较强降雨可促使其水中NO3^--N浓度在雨后短期内升高,进而促进水体反硝化作用,导致雨后溪流中溶存N2O浓度的增加. 展开更多
关键词 农业源溪流 溶存氧化亚氮 饱和度 硝态氮(NO-3-N) 反硝化 温度
基于人眼视觉特性的舰船图像增强方法 预览
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作者 王罡 《舰船科学技术》 北大核心 2019年第4期175-177,共3页
传统舰船图像增强方法没有考虑人眼视觉特征,导致图像人眼视觉识别率较低,对此提出新型舰船图像增强方法。通过对舰船图像数据的标准化和白化操作,完成舰船图像人眼视觉化处理,提取处理图像数据的颜色特征和纹理特征,消除干扰项,提高图... 传统舰船图像增强方法没有考虑人眼视觉特征,导致图像人眼视觉识别率较低,对此提出新型舰船图像增强方法。通过对舰船图像数据的标准化和白化操作,完成舰船图像人眼视觉化处理,提取处理图像数据的颜色特征和纹理特征,消除干扰项,提高图像特征维,根据图像H值,将升维后的图像数据,转换到RGB色彩空间中,合成图像色度、饱和度和强度,实现图像增强。实验数据表明,与传统图像增强方式相比,利用新设计的舰船图像增强方法,图像人眼视觉识别度提高27%,具有应用优势性。 展开更多
关键词 视觉特征 图像增强 特征维 饱和度
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珠江口盆地天然气水合物储层及饱和度预测 预览
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作者 姜秀娣 朱振宇 +2 位作者 何洋洋 张金淼 李清平 《中国造船》 EI CSCD 北大核心 2019年第A01期205-211,共7页
天然气水合物为未来传统能源的替代能源,目前世界各国都对其展开了积极的研究。由于地下含水合物层往往伴生有游离气,而对于水合物的不同开采方式,游离气的存在可能起到正向作用或者造成生产事故,且会对环境造成污染,因此准确预测水合... 天然气水合物为未来传统能源的替代能源,目前世界各国都对其展开了积极的研究。由于地下含水合物层往往伴生有游离气,而对于水合物的不同开采方式,游离气的存在可能起到正向作用或者造成生产事故,且会对环境造成污染,因此准确预测水合物分布的同时,也准确预测游离气的分布情况对水合物的安全开采意义十分重大。通常含水合物层具有明显的高纵波阻抗特征,而游离气具有低纵波阻抗特征,地震反演是最适合预测水合物和游离气的技术,但由于测井先验信息不足,造成地震反演方法预测水合物和游离气的可靠性较差。论文分别采用RGB融合、吸收分析等方法,对地震反演的结果加以验证和补充,准确预测了水合物和游离气的分布范围。 展开更多
关键词 水合物 游离气 RGB分频融合 阻抗反演 饱和度
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Prescribed Performance Control of One-DOF Link Manipulator With Uncertainties and Input Saturation Constraint 预览
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作者 Yang Yang Jie Tan Dong Yue 《自动化学报:英文版》 CSCD 2019年第1期148-157,共10页
In this paper, we mainly address the position control problem for one-degree of freedom(DOF) link manipulator despite uncertainties and the input saturation via the backstepping technique, active disturbance rejection... In this paper, we mainly address the position control problem for one-degree of freedom(DOF) link manipulator despite uncertainties and the input saturation via the backstepping technique, active disturbance rejection control(ADRC) as well as predefined tracking performance functions. The extended state observer(ESO) is employed to compensate uncertain dynamics and disturbances, and it does not rely on the accurate model of systems. The tracking differentiator(TD) is utilized to substitute the derivative of the virtual control signals, and the explosion of complexity caused by repeated differentiations of nonlinear functions is removed. The auxiliary system is used to deal with the control input limitation, and the tracking accuracy and speed are improved by predefined tracking performance functions.With the help of the input-to-state stability(ISS) and Lyapunov stability theories, it is proven that the tracking error can be gradually converged into arbitrarily small neighborhood of the origin, and the tracking error is adjusted by suitable choice of control parameters. The simulation results are presented for the verification of the theoretical claims. 展开更多
关键词 Active disturbance REJECTION control (ADRC) auxiliary system backstepping technique input SATURATION predefined tracking performance function
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Data-driven model-free adaptive attitude control of partially constrained combined spacecraft with external disturbances and input saturation
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作者 Han GAO Guangfu MA +1 位作者 Yueyong LYU Yanning GUO 《中国航空学报:英文版》 SCIE EI CAS CSCD 2019年第5期1281-1293,共13页
This study presents an improved data-driven Model-Free Adaptive Control(MFAC)strategy for attitude stabilization of a partially constrained combined spacecraft with external disturbances and input saturation. First, a... This study presents an improved data-driven Model-Free Adaptive Control(MFAC)strategy for attitude stabilization of a partially constrained combined spacecraft with external disturbances and input saturation. First, a novel dynamic linearization data model for the partially constrained combined spacecraft with external disturbances is established. The generalized disturbances composed of external disturbances and dynamic linearization errors are then reconstructed by a Discrete Extended State Observer(DESO). With the dynamic linearization data model and reconstructed information, a DESO-MFAC strategy for the combined spacecraft is proposed based only on input and output data. Next, the input saturation is overcome by introducing an antiwindup compensator. Finally, numerical simulations are carried out to demonstrate the effectiveness and feasibility of the proposed controller when the dynamic properties of the partially constrained combined spacecraft are completely unknown. 展开更多
关键词 Attitude CONTROL COMBINED SPACECRAFT DATA-DRIVEN CONTROL Discrete Extended State Observer(DESO) Input SATURATION
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