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Entropy-Based Global and Local Weight Adaptive Image Segmentation Models
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作者 Gang Li Yi Zhao +3 位作者 Ling Zhang Xingwei Wang Yueqin Zhang Fayun Guo 《清华大学学报自然科学版(英文版)》 EI CAS CSCD 2020年第1期149-160,共12页
This paper proposes a parameter adaptive hybrid model for image segmentation. The hybrid model combines the global and local information in an image, and provides an automated solution for adjusting the selection of t... This paper proposes a parameter adaptive hybrid model for image segmentation. The hybrid model combines the global and local information in an image, and provides an automated solution for adjusting the selection of the two weight parameters. Firstly, it combines an improved local model with the global Chan-Vese(CV) model, while the image’s local entropy is used to establish the index for measuring the image’s gray-level information. Parameter adjustment is then performed by the real-time acquisition of the ratio of the different functional energy in a self-adapting model responsive to gray-scale distribution in the image segmentation process.Compared with the traditional linear adjustment model, which is based on trial-and-error, this paper presents a more quantitative and intelligent method for achieving the dynamic nonlinear adjustment of global and local terms.Experiments show that the proposed model achieves fast and accurate segmentation for different types of noisy and non-uniform grayscale images and noise images. Moreover, the method demonstrates high stability and is insensitive to the position of the initial contour. 展开更多
关键词 IMAGE local ENTROPY PARAMETER ADAPTION IMAGE SEGMENTATION active CONTOUR
Protective effects of organic extracts of Alpinia oxyphylla against hydrogen peroxide-induced cytotoxicity in PC12 cells 预览
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作者 Li-Hong Duan Meng Li +10 位作者 Chun-Bao Wang Qing-Mei Wang Quan-Quan Liu Wan-Feng Shang Ya-Jin Shen Zhuo-Hua Lin Tong-Yang Sun Zheng-Zhi Wu Ying-Hong Li Yu-Long Wang Xun Luo 《中国神经再生研究:英文版》 SCIE CAS CSCD 2020年第4期682-689,共8页
Alpinia oxyphylla,a traditional herb,is widely used for its neuroprotective,antioxidant and memory-improving effects.However,the neuroprotective mechanisms of action of its active ingredients are unclear.In this study... Alpinia oxyphylla,a traditional herb,is widely used for its neuroprotective,antioxidant and memory-improving effects.However,the neuroprotective mechanisms of action of its active ingredients are unclear.In this study,we investigated the neuroprotective effects of various organic extracts of Alpinia oxyphylla on PC12 cells exposed to hydrogen peroxide-induced oxidative injury in vitro.Alpinia oxyphylla was extracted three times with 95%ethanol(representing extracts 1–3).The third 95%ethanol extract was dried and resuspended in water,and then extracted successively with petroleum ether,ethyl acetate and n-butanol(representing extracts 4–6).The cell counting kit-8 assay and microscopy were used to evaluate cell viability and observe the morphology of PC12 cells.The protective effect of the three ethanol extracts(at tested concentrations of 50,100 and 200μg/mL)against cytotoxicity to PC12 cells increased in a concentration-dependent manner.The ethyl acetate,petroleum ether and n-butanol extracts(each tested at 100,150 and 200μg/mL)had neuroprotective effects as well.The optimum effective concentration ranged from 50–200μg/mL,and the protective effect of the ethyl acetate extract was comparatively robust.These results demonstrate that organic extracts of Alpinia oxyphylla protect PC12 cells against apoptosis induced by hydrogen peroxide.Our findings should help identify the bioactive neuroprotective components in Alpinia oxyphylla. 展开更多
关键词 active INGREDIENTS ALPINIA oxyphylla apoptosis ethanol crude extract fraction hydrogen PEROXIDE nerve regeneration NEUROPROTECTIVE agent NEUROPROTECTIVE effects PC12 cells traditional HERB
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An active damping vibration control system for wind tunnel models
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作者 Wei LIU Mengde ZHOU +7 位作者 Zhengquan WEN Zhuang YAO Yu LIU Shihong WANG Xiaochun CUI Xiao LI Bing LIANG Zhenyuan JIA 《中国航空学报:英文版》 CSCD 2019年第9期2109-2120,共12页
In wind tunnels, long cantilever sting support systems with low structural damping encounter flow separation and turbulence during wind tunnel tests, which results in destructive low-frequency and big-amplitude resona... In wind tunnels, long cantilever sting support systems with low structural damping encounter flow separation and turbulence during wind tunnel tests, which results in destructive low-frequency and big-amplitude resonance, leading to data quality degradation and test envelope limitation. To ensure planed test envelope and obtain high-quality data, an active damping vibration control system independent of balance signal based on stackable piezoelectric actuators and velocity feedback using accelerometer, is proposed to improve the support stability and wind tunnel testing safety in transonic wind tunnel. Meanwhile, a design of powerful sting-root embedded active damping device is given and an active vibration control method is presented based on the mechanism analysis of aircraft model vibration. Furthermore, a self-adaptive fuzzy Proportion Differentiation(PD) control model is proposed to realize control parameters adjustment automatically for various testing conditions. Besides, verification tests are performed in laboratory and a continuous transonic wind tunnel. Experimental results indicate that the aircraft model does not vibrate obviously from -4° to 11° at Ma = 0.6, the number of useable angle-of-attack has increased by 7° at Ma = 0.6 and 5° at Ma = 0.7 respectively, satisfying the requirements of practical wind tunnel tests. 展开更多
关键词 ACCELEROMETER ACTIVE DAMPING STING VIBRATION TRANSONIC wind tunnel VIBRATION ACTIVE control
高校易班建设思路方法的探究
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作者 庞海全 强静雨 张齐东 《中国多媒体与网络教学学报(电子版)》 2019年第9期1-2,共2页
易班作为新时代背景下的思想政治教育推广平台,要在网络阵地占据主动权,发挥引领作用。但在探索易班建设过程中,出现诸多问题,这就要求我们要主动利用新技术,不断地进行思想和方法的创新,积极寻找解决问题的关键之处。本文从探索易班建... 易班作为新时代背景下的思想政治教育推广平台,要在网络阵地占据主动权,发挥引领作用。但在探索易班建设过程中,出现诸多问题,这就要求我们要主动利用新技术,不断地进行思想和方法的创新,积极寻找解决问题的关键之处。本文从探索易班建设出发,挖掘出目前易班建设存在的困境,并提出相关的解决思路,为易班建设提供借鉴,实现思想政治教育,教育教学,文化娱乐以及生活服务等方面在易班平台上的综合发展。 展开更多
关键词 易班建设 思想政治教育 黏度 活跃度
Tectonic implication of geomorphometric analyses along the Saravan Fault: evidence of a difference in tectonic movements between the Sistan Suture Zone and Makran Mountain Belt
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作者 Roghayeh KASHANI Abdolreza PARTABIAN Ahmad NOURBAKHSH 《山地科学学报:英文版》 SCIE CSCD 2019年第5期1023-1034,共12页
In this paper, remote sensing techniques,as well as field studies, have been used to investigate the geomorphological processes and landscape evolution along the Saravan Fault, SE Iran to highlight how topographic fea... In this paper, remote sensing techniques,as well as field studies, have been used to investigate the geomorphological processes and landscape evolution along the Saravan Fault, SE Iran to highlight how topographic features were influenced by active tectonics. Quantitative geomorphic analysis was carried out using mountain-front sinuosity(Smf),valley floor width-valley height ratio(Vf), drainage basin asymmetry factor(Af), Hypsometric integral(Hi), drainage basin shape index(Bs), mean axial slope of channel(MASC), standard deviation of topography(STD) and index of active tectonic(Iat).Remote sensing techniques, as well as field studies revealed that the Saravan Fault have three parts trending N-S, NW-SE, and E-W. Obtained results show that basins with high Iat index are located at where the strike of the Saravan Faults changes and where several strike-slip faults are crossed the Saravan fault. 展开更多
关键词 Active TECTONIC Sistan SUTURE Zone MAKRAN MOUNTAIN Belt Saravan FAULT Iran DEM
Essay on Indifference:Affect and Thinking From Spinoza to Freud and Deleuze 预览
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作者 Szymon Wróbel 《哲学研究:英文版》 2019年第2期65-73,共9页
In this paper,the author is questioning the very concept of“indifference of thinking”.The author also asks:In what sense,thinking leads to“overall indifference”?What,indeed,is indifference?Reading carefully,the ph... In this paper,the author is questioning the very concept of“indifference of thinking”.The author also asks:In what sense,thinking leads to“overall indifference”?What,indeed,is indifference?Reading carefully,the philosophical texts on affects,mainly Spinoza,Freud,Bergson,and Deleuze,author argues that indifference is not a kind of non-affection,beside-affection,post-affection,but rather,it is a trace of affect―just as cinders are remnants of fire.Indifference is neither abnegation which is a kind of statement that we could not care less.On the contrary,it is in indifference where we find profound commitment to bringing back things of this world to their natural position. 展开更多
关键词 active state conatus contrary affect death drive FACADE formations general INDIFFERENCE MADNESS resolution sustainability
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太阳能辅助供暖技术综述 预览
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作者 韦笑 《节能与环保》 2019年第10期60-62,共3页
我国北方集中供暖对空气环境造成很大影响,利用太阳能辅助供暖技术能有效改善北方供暖问题。介绍太阳能辅助供暖技术发展现状,分别介绍了被动式太阳能辅助供暖技术及主动式太阳能辅助供暖技术在当下的应用实践,太阳能辅助供暖技术具有... 我国北方集中供暖对空气环境造成很大影响,利用太阳能辅助供暖技术能有效改善北方供暖问题。介绍太阳能辅助供暖技术发展现状,分别介绍了被动式太阳能辅助供暖技术及主动式太阳能辅助供暖技术在当下的应用实践,太阳能辅助供暖技术具有良好的设备工况和节能效果,该技术具有良好的发展前景和研究意义。 展开更多
关键词 太阳能辅助供暖技术 被动式 主动式
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Thermal dynamics of the permafrost active layer under increased precipitation at the Qinghai-Tibet Plateau
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作者 LI De-sheng WEN Zhi +3 位作者 CHENG Qian-gong XING Ai-guo ZHANG Ming-li LI An-yuan 《山地科学学报:英文版》 SCIE CSCD 2019年第2期309-322,共14页
Precipitation has a significant influence on the hydro-thermal state of the active layer in permafrost regions, which disturbs the surface energy balance, carbon flux, ecosystem, hydrological cycles and landscape proc... Precipitation has a significant influence on the hydro-thermal state of the active layer in permafrost regions, which disturbs the surface energy balance, carbon flux, ecosystem, hydrological cycles and landscape processes. To better understand the hydro-thermal dynamics of active layer and the interactions between rainfall and permafrost, we applied the coupled heat and mass transfer model for soil-plant-atmosphere system into high-altitude permafrost regions in this study. Meteorological data, soil temperature, heat flux and moisture content from different depths within the active layer were used to calibrate and validate this model. Thereafter, the precipitation was increased to explore the effect of recent climatic wetting on the thermal state of the active layer. The primary results demonstrate that the variation of active layer thickness under the effect of short-term increased precipitation is not obvious, while soil surface heat flux can show the changing trends of thermal state in active layer, which should not be negligible. An increment in year-round precipitation leads to a cooling effect on active layers in the frozen season, i.e. verifying the insulating effect of 'snow cover'. However, in the thawed season, the increased precipitation created a heating effect on active layers, i.e. facilitating the degradation of permafrost. The soil thermal dynamic in single precipitation event reveals that the precipitation event seems to cool the active layer, while compared with the results under increased precipitation, climatic wetting trend has a different influence on the permafrost evolution. 展开更多
关键词 Active layer PRECIPITATION Qinghai-Tibet PLATEAU Hydro-thermal dynamic
主动式与注气式鼻肠管置管法在ICU重型颅脑损伤患者的效果观察 预览
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作者 周逸 莫红平 +5 位作者 黄春荣 李慧玲 邹子俊 娄红羽 李玲娣 肖燕婷 《中国卫生标准管理》 2019年第5期147-149,共3页
目的探讨两种不同鼻肠管置管方法对ICU重症颅脑损伤患者肠内营养护理的效果。方法选取2018年1—7月某院ICU重型颅脑损伤患者174例,随机分为对照组和观察组,每组87例。对照组为主动式鼻肠管置管法,观察组为注气式鼻肠管置管法,比较两组... 目的探讨两种不同鼻肠管置管方法对ICU重症颅脑损伤患者肠内营养护理的效果。方法选取2018年1—7月某院ICU重型颅脑损伤患者174例,随机分为对照组和观察组,每组87例。对照组为主动式鼻肠管置管法,观察组为注气式鼻肠管置管法,比较两组插管成功率。结果观察组置管成功率95.40%(83/87)高于对照组置管成功率80.46%(70/87),两组比较差异有统计意义(P <0.05)。结论注气式鼻肠管置管法能提高置管成功率。 展开更多
关键词 主动式 注气式 鼻肠管置管 重型颅脑损伤 ICU 护理
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Boosting photocatalytic degradation of RhB via interfacial electronic effects between Fe-based ionic liquid and g-C3N4 预览
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作者 Xiaowei Li Bin Wang +4 位作者 Yuhong Huang Jun Di Jiexiang Xia Wenshuai Zhu Huaming Li 《绿色能源与环境:英文版》 CSCD 2019年第2期198-206,共9页
The Fe-based ionic liquid doped g-C3N4(FeeCN)photocatalyst was firstly prepared base on ultrathin g-C3N4 obtained by multiple calcination method with a metal-based reactive ionic liquid[Omim]FeCl4 for the degradation ... The Fe-based ionic liquid doped g-C3N4(FeeCN)photocatalyst was firstly prepared base on ultrathin g-C3N4 obtained by multiple calcination method with a metal-based reactive ionic liquid[Omim]FeCl4 for the degradation of Rhodamine B(RhB).Experimental results revealed that Fe^3+species were doped into the framework of g-C3N4.The effect of the amount of Fe-doping on the catalytic activity was performed.The result showed that the FeeCN could effectively degrade RhB under the condition of visible light irradiation.The photocurrent analysis showed that the incorporation of Fe^3+into g-C3N4 material could accelerate the separation of the photogenerated carriers significantly.At the same time,the reactive species generated during the photodegradation process were tested by radicals trapping experiments and electron spin resonance(ESR).It was proposed that the synergistic effect of O^-2 and·OH contributed to degrade RhB efficiently. 展开更多
关键词 g-C3N4 [Omim]FeCl4 Photocatalytic Visible light Active species
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Design and Development of a Wheel-less Snake Robot with Active Stiffness Control for Adaptive Pedal Wave Locomotion
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作者 Mohammadali Javaheri Koopaee Sander Bal +1 位作者 Christopher Pretty Xiaoqi Chen 《仿生工程学报:英文版》 SCIE EI CSCD 2019年第4期593-607,共15页
This paper presents the design and manufacture process of a wheel-less,modular snake robot with series elastic actuators to reliably measure motor torque signal and investigate the effectiveness of active stiffness co... This paper presents the design and manufacture process of a wheel-less,modular snake robot with series elastic actuators to reliably measure motor torque signal and investigate the effectiveness of active stiffness control for achieving adaptive snake-like locomotion.A polyurethane based elastic element to be attached between the motor and the links at each joint was designed and manufactured using water jet cutter,which makes the final design easier to develop and more cost-effective,compared to existing snake robots with torque measurement capabilities.The reliability of such torque measurement mechanism was examined using simulated dynamical model of pedal wave motion,which proves the efficacy of the design.A distributed control system was also designed,which with the help of an admittance controller,enables active control of the joint stiffness to achieve adaptive snake robot pedal wave locomotion to climb over obstacles,which unlike existing methods does not require prior information about the location of the obstacle.The effectiveness of the proposed controller in comparison to open-loop control strategy was verified by the number of experiments.The results show the capability of the robot to successfully climb over obstacles with the height of more than 55%of the diameter of the snake robot modules. 展开更多
关键词 modular SNAKE robot series elastic ACTUATOR ACTIVE stiffness control PEDAL WAVE locomotion ADAPTIVE locomotion
Weak Seismic Signal Extraction Based on the Curvelet Transform 预览
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作者 TAN Junqing YANG Runhai +1 位作者 WANG Bin XIANG Ya 《中国地震研究:英文版》 CSCD 2019年第2期220-234,共15页
Seismic signal denoising is a key step in seismic data processing.Airgun signals are easy to be interfered with by noise when it travels a long distance due to the weak energy of active source signal of the airgun.Aim... Seismic signal denoising is a key step in seismic data processing.Airgun signals are easy to be interfered with by noise when it travels a long distance due to the weak energy of active source signal of the airgun.Aiming to solve this problem,and considering that the conventional Curvelet transform threshold processing method does not use the seismic spectrum information,we independently process the Curvelet scale layer corresponding to valid data based on the characteristics of the Curvelet transform of multi-scale,multi-direction and capable of expressing the sparse seismic signals in order to fully excavate the information features.Combined with the Curvelet adaptive threshold denoising the algorithm,we apply the Curvelet transform to denoising seismic signals while retaining the weak information in the signal as much as possible.The simulation experiments show that the improved threshold denoising method based on Curvelet transform is superior to the frequency domain filtering,wavelet denoising and traditional Curvelet denoising method in detailed information extraction and signal denoising of low SNR signals.The calculation accuracy of the relative wave velocity variation of underground medium is improved. 展开更多
关键词 Seismic SIGNAL DENOISING Airgun active source SIGNAL CURVELET TRANSFORM The velocity of the UNDERGROUND medium
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Recent advances in active sites identification and regulation of M-N/C electro-catalysts towards ORR
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作者 Jie Liu Zhao Jin +3 位作者 Xian Wang Junjie Ge Changpeng Liu Wei Xing 《中国科学:化学英文版》 SCIE EI CAS CSCD 2019年第6期669-683,共15页
Transition metal and nitrogen co-doped carbon(M–N/C) catalysts are recognized as the most prospective alternatives for platinum-based electro-catalysts towards oxygen reduction reaction(ORR) in polymer electrolyte fu... Transition metal and nitrogen co-doped carbon(M–N/C) catalysts are recognized as the most prospective alternatives for platinum-based electro-catalysts towards oxygen reduction reaction(ORR) in polymer electrolyte fuel cells. Recently, significant progress has been achieved in the identification and regulation of active sites of this kind of catalysts. In this mini review,we summarize the techniques and strategies to identify active sites in M–N/C catalysts, the main debates on active sites types, the measurement method for active site density, the reactivity descriptors for M–N/C catalysts, and directions to the design of ORR M–N/C catalysts. 展开更多
关键词 ORR electro-catalysts M–N/C active SITES
Monitoring gas-and particulate-phase short-chain polychlorinated paraffins in the urban air of Dalian by a self-developed passive sampler
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作者 Yifan Wang Xiuhua Zhu +7 位作者 ,Yuan Gao Hao Bai Pengyuan Wang Jiping Chen ,Heping Yuan Longxing Wang Xiaoxiao Li Wei Wang 《环境科学学报:英文版》 SCIE EI CAS CSCD 2019年第6期287-295,共9页
The concentration of short-chain polychlorinated paraffins(SCCPs) in the urban air of Dalian,China was monitored from September 2016 to August 2017 with a self-developed passive sampler(PAS1) and an active high-volume... The concentration of short-chain polychlorinated paraffins(SCCPs) in the urban air of Dalian,China was monitored from September 2016 to August 2017 with a self-developed passive sampler(PAS1) and an active high-volume sampler, simultaneously. PAS1 successfully collected the entire target SCCPs in the ambient air. Air SCCPs sampled by PAS1 were found be in the linear uptake stage during 181 days of sampling. Passive and active samples showed comparable congener profiles, and the dominant contributors of SCCPs in the two kinds of samples were similar. A significant linear correlation was observed between the total concentration of SCCPs sampled by PAS1 and active sampler in the four seasons. The passive sampling rates of the PAS1 for the gas and particulate phases of SCCPs were measured. The quantitative structure–property relationship of the sampling rate of PAS1(Rair) for gas-phase SCCPs was studied. From the molecular point of view, Rairwas mainly affected by the molecular weight and sub-cooled liquid vapor pressure of SCCPs. In general, SCCPs in the urban air of Dalian mainly existed in gas phase,lower molecular weight SCCPs primarily occurred in the gas phase, whereas higher molecular weight SCCPs were predominately adsorbed or absorbed on airborne particles. The air concentration of SCCPs in the four seasons were different, the correlation of the concentration of SCCPs in the air with the meteorology parameters was conducted. The exposure risk by intake air SCCPs of the residents around the sampling sites was evaluated according to the European risk assessment standards. 展开更多
关键词 Ambient air Short-chain POLYCHLORINATED paraf FINS PASSIVE SAMPLER Active sampling PASSIVE sampling
Active Source Seismic Identification and Automatic Picking of the P-wave First Arrival Using a Convolutional Neural Network 预览
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作者 XU Zhen WANG Tao +4 位作者 XU Shanhui WANG Baoshan FENG Xuping SHI Jing YANG Minghan 《中国地震研究:英文版》 CSCD 2019年第2期288-304,共17页
In seismic data processing,picking of the P-wave first arrivals takes up plenty of time and labor,and its accuracy plays a key role in imaging seismic structures.Based on the convolution neural network(CNN),we propose... In seismic data processing,picking of the P-wave first arrivals takes up plenty of time and labor,and its accuracy plays a key role in imaging seismic structures.Based on the convolution neural network(CNN),we propose a new method to pick up the P-wave first arrivals automatically.Emitted from MINI28 vibroseis in the Jingdezhen seismic experiment,the vertical component of seismic waveforms recorded by EPS 32-bit portable seismometers are used for manually picking up the first arrivals(a total of 7242).Based on these arrivals,we establish the training and testing sets,including 25,290 event samples and 710,616 noise samples(length of each sample:2 s).After 3,000 steps of training,we obtain a convergent CNN model,which can automatically classify seismic events and noise samples with high accuracy(>99%).With the trained CNN model,we scan continuous seismic records and take the maximum output(probability of a seismic event)as the P-wave first arrival time.Compared with STA/LTA(short time average/long time average),our method shows higher precision and stronger anti-noise ability,especially with the low SNR seismic data.This CNN method is of great significance for promoting the intellectualization of seismic data processing,improving the resolution of seismic imaging,and promoting the joint inversion of active and passive sources. 展开更多
关键词 CNN Active source SEISMIC identification FIRST ARRIVAL PICKING ANTI-NOISE ability
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A-π-D-π-A small-molecule donors with different end alkyl chains obtain different morphologies in organic solar cells
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作者 Yanan Shi Chen Yang +9 位作者 Huan Li Lixuan Liu Ruimin Zhou Wenjun Zou Zhen Wang Qiong Wu Dan Deng Jianqi Zhang Kun Lu Zhixiang Wei 《中国化学快报:英文版》 SCIE CAS CSCD 2019年第4期906-910,共5页
For bulk-heterojunction organic solar cells, the morphology of the blend films highly influence the exciton dissociation and charge transport process. In this work, two novel A-π-D-π-A (A represents the acceptor uni... For bulk-heterojunction organic solar cells, the morphology of the blend films highly influence the exciton dissociation and charge transport process. In this work, two novel A-π-D-π-A (A represents the acceptor unit and D represents the donor unit) backbone structure small molecular electron donors based on two dimensional conjugated naphtho[1,2-b:5,6-b']dithiophene (NDT) with different end alkyl chains, named as NDT-3T-EH and NDT-3T-O, have been designed and synthesized. The photovoltaic property of NDT-3T-O-based device is better than that of the NDT-3T-EH and the best efficiency reaches 7.06%, and the photovoltaic property of NDT-3T-EH reaches 6.11%. The difference in the performance should be attributed to the different morphology and phase separation resulted from the different crystallinity and aggregation ability of two donors. The results demonstrate that the optimized end alkyl chains can be used to design A-π-D-π-A backbone structure small molecular electron donors for smallmolecule organic solar cells. 展开更多
关键词 Organic solar cells All-small-molecule A-π-D-π-A small molecular donor END ALKYL chain Morphology of active layer
Different vertical distribution of zooplankton community between North Pacific Subtropical Gyre and Western Pacific Warm Pool: its implication to carbon flux 预览
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作者 Dong Sun Dongsheng Zhang +1 位作者 Ruiyan Zhang Chunsheng Wang 《海洋学报:英文版》 SCIE CAS CSCD 2019年第6期32-45,共14页
The mesozooplankton in both epipelagic and mesopelagic zones is essentially important for the study of ecosystem and biological carbon pump. Previous studies showed that the diel vertical migration (DVM) pattern of me... The mesozooplankton in both epipelagic and mesopelagic zones is essentially important for the study of ecosystem and biological carbon pump. Previous studies showed that the diel vertical migration (DVM) pattern of mesozooplankton varied among ecosystems. However, that pattern was largely unknown in the Western Pacific Warm Pool (WPWP). The vertical distribution, DVM and community structure of mesozooplankton from the surface to 1 000 m were compared at Stas JL7K (WPWP) and MA (North Pacific Subtropical Gyre, NPSG). Two sites showed similarly low biomass in both epipelagic and mesopelagic zones, which were in accordance with oligotrophic conditions of these two ecosystems. Stronger DVM (night/day ratio) was found at JL7K (1.31) than that at MA (1.09) on surface 0–100 m, and an obvious night increase of mesopelagic biomass was observed at JL7K, which was probably due to migrators from bathypelagic zone. Active carbon flux by DVM of zooplankton was estimated to be 0.23 mmol/(m2·d) at JL7K and 0.16 mmol/(m2·d) at MA. The community structure analysis showed that calanoid copepods, cnidarians and appendicularians were the main contributors to DVM of mesozooplankton at both sites. We also compared the present result with previous studies of the two ecosystems, and suggested that the DVM of mesozooplankton was more homogeneous within the WPWP and more variable within the NPSG, though both ecosystems showed typically extremely oligotrophic conditions. The different diel vertical migration strength of mesozooplankton between NPSG and WPWP implied different efficiency of carbon pump in these two ecosystems. 展开更多
关键词 mesopelagic zone DIEL VERTICAL MIGRATION biological PUMP VERTICAL distribution active carbon FLUX
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Characteristics of the Seismic Waves from a New Active Source Based on Methane Gaseous Detonation 预览
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作者 WANG Weitao WANG Xiang +7 位作者 MENG Chuanmin DONG Shi WANG Zhigang XIE Junju WANG Baoshan YANG Wei XU Shanhui WANG Tao 《中国地震研究:英文版》 CSCD 2019年第2期354-366,共13页
Active seismic sources are critical for obtaining high resolution images of the subsurface.For active imaging in urban areas,environment friendly and green seismic sources are required.In present work,we introduce a n... Active seismic sources are critical for obtaining high resolution images of the subsurface.For active imaging in urban areas,environment friendly and green seismic sources are required.In present work,we introduce a new type of green active source based on the gaseous detonation of methane and oxygen.When fired in a closed container,the chemical reaction,i.e.gaseous detonation,will produce high pressure air over 150 MPa.Seismic waves are produced when high pressure air is quickly released to impact the surroundings.The first field experiment of this active source was carried out in December,2017 in Jingdezhen,Jiangxi Province,where a series of active sources were excited to explore their potential in mine exploration.In current work,we analyzed the seismic waves recorded by near-field accelerators and a dense short-period seismic array and compared them with those from a mobile airgun source,another kind of active source by releasing high pressure air into water.The results demonstrate that it can be used for high resolution near surface imaging.Firstly,the gaseous detonation productions are harmless CO2 and water,making it a green explosive source.Secondly,the dominant seismic frequencies are 10-80 Hz and a single shot can be recorded up to 15 km,making it suitable for local structure investigations.Thirdly,it can be excited in vertical wells,similar to traditional powder explosive sources.It can also act as an additional on-land active source to airgun sources,which requires a suitable water body as intermediate media to generate repeating signals.Moreover,the short duration and high frequency signature of the source signals make it safe with no damage to nearby buildings.These make it convenient to excite in urban areas.As a new explosive source,the excitation equipment and conditions,such as gas ratio,sink depth and air-releasing directions,need further investigation to improve seismic wave generation efficiency. 展开更多
关键词 ACTIVE SOURCE SEISMIC WAVES METHANE DETONATION SOURCE Green SEISMIC SOURCE
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Topology optimization of piezoelectric bi-material actuators with velocity feedback control
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作者 Mariana MORETTI Emilio C.N.SILVA 《机械工程前沿:英文版》 CSCD 2019年第2期190-200,共11页
In recent years,the new technologies and discoveries on manufacturing materials have encouraged researchers to investigate the appearance of material properties that are not naturally available.Materials featuring a s... In recent years,the new technologies and discoveries on manufacturing materials have encouraged researchers to investigate the appearance of material properties that are not naturally available.Materials featuring a specific stiffness,or structures that combine non-structural and stmctural functions are applied in the aerospace,electronics and medical industry fields.Particularly,structures designed for dynamic actuation with reduced vibration response are the focus of this work.The bi-material and multifunctional concepts are considered for the design of a controlled piezoelectric actuator with vibration suppression by means of the topology optimization method(TOM).The bi-material piezoelectric actuator(BPEA)has its metallic host layer designed by the TOM,which defines the structural function,and the electric function is given by two piezo-ceramic layers that act as a sensor and an actuator coupled with a constant gain active velocity feedback control(AVFC).The AVFC,provided by the piezoelectric layers,affects the structural damping of the system through the velocity state variables readings in time domain.The dynamic equation analyzed throughout the optimization procedure is fully elaborated and implemented.The dynamic response for the rectangular fbur-noded finite element analysis is obtained by the Newmark's time-integration method,which is applied to the physical and the adjoint systems,given that the adjoint formulation is needed for the sensitivity analysis.A gradient-based optimization method is applied to minimize the displacement energy output measured at a predefined degree-of-freedom of the BPEA when a transient mechanical load is applied.Results are obtained for different control gain values to evaluate their influence on the final topology. 展开更多
关键词 TOPOLOGY optimization method BI-MATERIAL piezoactuator active VELOCITY feedback control timedomain transient analysis HOST structure design vibration suppression
Active control of friction by transverse oscillations
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作者 J.BENAD K.NAKANO +1 位作者 V.L.POPOV M.POPOV 《摩擦(英文版)》 CSCD 2019年第1期74-85,共12页
The present paper is devoted to a theoretical analysis of sliding friction under the influence of in-plane oscillations perpendicular to the sliding direction.Contrary to previous studies of this mode of active contro... The present paper is devoted to a theoretical analysis of sliding friction under the influence of in-plane oscillations perpendicular to the sliding direction.Contrary to previous studies of this mode of active control of friction,we consider the influence of the stiffness of the tribological contact in detail and show that the contact stiffness plays a central role for small oscillation amplitudes.In the present paper we consider the case of a displacement-controlled system,where the contact stiffness is small compared to the stiffness of the measuring system.It is shown that in this case the macroscopic coefficient of friction is a function of two dimensionless parameters a dimensionless sliding velocity and dimensionless oscillation amplitude.In the limit of very large oscillation amplitudes,known solutions previously reported in the literature are reproduced.The region of small amplitudes is described for the first time in this paper. 展开更多
关键词 SLIDING FRICTION IN-PLANE OSCILLATION contact STIFFNESS COEFFICIENT of FRICTION active control of FRICTION
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