检索结果-南通市图书馆

Quantizing Euclidean Motions via Double-Coset Decomposition

Research 2019年第1期2019卷 525-540页

作者： christian wülker Sipu Ruan Gregory S.Chirikjian Johns Hopkins University BaltimoreMDUSA Department of Mechanical Engineering National University of SingaporeSingapore

Concepts from mathematical crystallography and group theory are used here to quantize the group of rigid-body motions,resulting in a“motion alphabet”with which robot motion primitives are *** these primitives it is possible to develop a dictionary of physical *** with an alphabet of the sort developed here,intelligent actions of robots in the world can be approximated with fnite sequences of characters,thereby forming the foundation of a language in which robot motion is *** particular,we use the discrete handedness-preserving symmetries of macromolecular crystals(known in mathematical crystallography as Sohncke space groups)to form a coarse discretization of the space SE(3)of rigid-body *** discretization is made fner by subdividing using the concept of double-coset *** specifcally,a very efcient,equivolumetric quantization of spatial motion can be defned using the group-theoretic concept of a double-coset decomposition of the formΓ\SE(3)/Δ,whereΓis a Sohncke space group andΔis a fnite group of rotational symmetries such as those of the *** resulting discrete alphabet is based on a very uniform sampling of SE(3)and is a tool for describing the continuous trajectories of robots and *** efcient coarse-to-fne search algorithm is presented to round of any motion sampled from the continuous group of motions to the nearest element of our *** is shown that our alphabet and this efcient rounding algorithm can be used as a geometric data structure to accelerate the performance of other sampling schemes designed for desirable dispersion or discrepancy ***,the general“signals to symbols”problem in artifcial intelligence is cast in this framework for robots moving continuously in the world.

关键词： robot primitive thereby

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Volume and surface effects on two-photonic and three-photonic processes in dry co-doped upconversion nanocrystals

引用

Nano Research 2022年第3期15卷 2362-2373页

作者： Bettina Grauel christian würth christian Homann Lisa Krukewitt Elina Andresen Janina Roik Sebastian Recknagel Markus Haase Ute Resch-Genger Federal Institute for Materials Research and Testing(BAM) Division 1.2 BiophotonicsRichard-Willstaetter-Str.1112489 BerlinGermany Federal Institute for Materials Research and Testing(BAM) Division 1.6 Inorganic Reference MaterialsRichard-Willstaetter-Str.1112489 BerlinGermany Institute of Chemistry of New Materials Department Biology/ChemistryUniversity OsnabrueckBarbarastr.749076 OsnabrueckGermany Department of Anesthesiology and Intensive Care Medicine University Medical Center RostockSchillingallee 3518057 RostockGermany

Despite considerable advances in synthesizing high-quality core/shell upconversion(UC)nanocrystals(NC;UCNC)and UCNC photophysics,the application of near-infrared(NIR)-excitable lanthanide-doped UCNC in the life and material sciences is still hampered by the relatively low upconversion luminescence(UCL)of UCNC of small size or thin protecting *** obtain deeper insights into energy transfer and surface quenching processes involving Yb^(3+) and Er^(3+) ions,we examined energy loss processes in differently sized solid core NaYF_(4) nanocrystals doped with either Yb^(3+)(YbNC;20%Yb^(3+))or Er^(3+)(ErNC;2%Er^(3+))and co-doped with Yb^(3+) and Er^(3+)(YbErNC;20%Yb^(3+) and 2%Er^(3+))without a surface protection shell and coated with a thin and a thick NaYF_(4) shell in comparison to single and co-doped bulk *** studies at 375 nm excitation demonstrate back-energy transfer(BET)from the ^(4)G_(11/2) state of Er^(3+) to the ^(2)F_(5/2) state of Yb^(3+),through which the red Er^(3+) ^(4)F_(9/2) state is efficiently *** power density(P)-dependent steady state and time-resolved photoluminescence measurements at different excitation and emission wavelengths enable to separate surface-related and volume-related effects for two-photonic and three-photonic processes involved in UCL and indicate a different influence of surface passivation on the green and red Er3+*** intensity and lifetime of the latter respond particularly to an increase in volume of the active UCNC *** provide a three-dimensional random walk model to describe these effects that can be used in the future to predict the UCL behavior of UCNC.

关键词： upconversion luminescence core/shell nanoparticles dopant concentration lifetime volume effect surface quenching

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Particle-size-dependent upconversion luminescence of NaYF4:Yb,Er nanoparticles in organic solvents and water at different excitation power densities

引用

Nano Research 2018年第12期11卷 6360-6374页

作者： Marco Kraft christian würth Verena Muhr Thomas Hirsch Ute Resch-Genger Federal Institute for Matefiab Research and Testing (BAM) Division1.2BiophotonicsRichard-Willstaetter-Str.1112489BerlinGermany Institute of Analytical Chemistry Chemo-and BiosensorsUniversity of Regensburg93040RegensburgGermany

A systematic study of the luminescence properties of monodisperse β-NaYF4: 20% Yb3+, 2% Er3+ upconversion nanoparticles (UCNPs) with sizes ranging from 12-43 nm is presented utilizing steady-state and time-resolved fluorometry. Special emphasis was dedicated to the absolute quantification of size- and environment-induced quenching of upconversion luminescence (UCL) by high-energy O-H and C-H vibrations from solvent and ligand molecules at different excitation power densities (P). In this context, the still-debated population pathways of the 4F9/2 energy level of Er3+ were examined. Our results highlight the potential of particle size and P value for color tuning based on the pronounced near-infrared emission of 12 nm UCNPs, which outweighs the red Er3+ emission under “strongly quenched” conditions and accounts for over 50% of total UCL in water. Because current rate equation models do not include such emissions, the suitability of these models for accurately simulating all (de)population pathways of small UCNPs must be critically assessed. Furthermore, we postulate population pathways for the 4F9/2 energy level of Er3+, which correlate with the size-, environment-, and P-dependent quenching states of the higher Er3+ energy levels.

关键词： upconversion nanoparticle quenching diameter water cyclohexane

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Elective thoracotomy for pedicle screw removal to prevent severe aortic bleeding

引用

world Journal of Clinical Cases 2014年第4期2卷 100-103页

作者： Sebastian Decker Mohamed Omar christian Krettek christian w Müller Trauma Department Hannover Medical School30625 Hannover Germany

we present a case of a 33-year-old female who sustained multiple injuries of her spine, including spinous process fractures of C5 to C7 and a lamina fracture of C6 and C7. Her thoracic spine showed transverse process fractures of T4 to T10, a compression fracture and lamina fracture of T3, spinous process and transverse process fractures of T4 and T5, a rotation injury of T6, as well as a compression fracture of L1. Thirteen months after posterior thoracic spinal instrumentation, a pedicle screw was suspected to be in contact with the aorta, which was proved by computed tomography angiograms. Consequently, implant removal was planned with direct exposure of the aorta in order to allow for immediate repair if needed. So far, studies that compare different techniques to remove pedicle screws that are suspected to penetrate the aorta are missing. However, different techniques have been described in case reports, mainly minimally invasive endovascular techniques vs open techniques such as thoracotomy.

关键词： Spine Pedicle screw Aorta Bleeding Implant removal Hemorrhage

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

相变中的界面(英文)

引用

金属学报 1997年第2期33卷 150-156页

作者： J.w.christian DepartmentofMaterials OxfordUniversityParksRoadOxfordOX13PHUK

讨论了各类相变中的界面分类．重构型相变没有共格界面，相变产物形状也无系统性变化．位移型相变有完全共格或部份共格的界面，有可见的相变产物形状变化．完全共格界面出现在无成分变化的马氏体型相变以及有成分变化的扩散位移型相变... 详细信息

讨论了各类相变中的界面分类．重构型相变没有共格界面，相变产物形状也无系统性变化．位移型相变有完全共格或部份共格的界面，有可见的相变产物形状变化．完全共格界面出现在无成分变化的马氏体型相变以及有成分变化的扩散位移型相变中．这二种类型界面的迁移依靠台阶（马氏体相变中称之谓相变位错）的运动完成．部分共格界面也可能出现在马氏体型或较为少见的扩散型相变中．

关键词：界面马氏体相变贝氏体

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

LiYF_(4):Yb/LiYF_(4) and LiYF_(4):Yb,Er/LiYF_(4) core/shell nanocrystals with luminescence decay times similar to YLF laser crystals and the upconversion quantum yield of the Yb,Er doped nanocrystals

引用

Nano Research 2021年第3期14卷 797-806页

作者： Frederike Carl Leonie Birk Bettina Grauel Monica Pons christian würth Ute Resch-Genger Markus Haase Institute of Chemistry of New Materials Department Biology/ChemistryUniversity OsnabrueckBarbarastr.749076OsnabrueckGermany Division 1.2 Biophotonics Federal Institute for Materials Research and Testing(BAM)Richard-Willstaetter-Str.1112489BerlinGermany

we developed a procedure to prepare luminescent LiYF_(4):Yb/LiYF_(4) and LiYF_(4):Yb,Er/LiYF_(4) core/shell nanocrystals with a size of approximately 40 nm revealing luminescence decay times of the dopant ions that approach those of high-quality laser crystals of LiYF_(4):Yb(Yb:YLF)and LiYF_(4):Yb,Er(Yb,Er:YLF)with identical doping *** the luminescence decay times of Yb^(3+)and Er^(3+)are known to be very sensitive to the presence of quenchers,the long decay times of the core/shell nanocrystals indicate a very low number of defects in the core particles and at the core/shell *** improvement in the performance was achieved by introducing two important modifications in the commonly used oleic acid based ***,the shell was prepared via a newly developed method characterized by a very low nucleation rate for particles of pure LiYF_(4) shell ***,anhydrous acetates were used as precursors and additional drying steps were applied to reduce the incorporation of OH−in the crystal lattice,known to quench the emission of Yb^(3+)*** power density(P)-dependent absolute measurements of the upconversion luminescence quantum yield(ΦUC)of LiYF_(4):Yb,Er/LiYF_(4) core/shell particles reveal a maximum value of 1.25%at P of 180 w·cm^(−2).Although lower than the values reported for NaYF4:18%Yb,2%Er core/shell nanocrystals with comparable sizes,theseΦUC values are the highest reported so far for LiYF_(4):18%Yb,2%Er/LiYF_(4) nanocrystals without additional *** improvements may nevertheless be possible by optimizing the dopant concentrations in the LiYF_(4) nanocrystals.

关键词： nanocrystal decay time luminescence LiYF_(4) quantum yield upconversion

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Yb-and Er concentration dependence of the upconversion luminescence of highly doped NaYF_(4):Yb,Er/NaYF_(4):Lu core/shell nanocrystals prepared by a water-free synthesis

引用

Nano Research 2022年第10期15卷 9639-9646页

作者： christian würth Bettina Grauel Monika Pons Florian Frenzel Philipp Rissiek Kerstin Rücker Markus Haase Ute Resch-Genger Federal Institute for Materials Research and Testing(BAM) Division BiophotonicsRichard-Willstaetter-Str.1112489 BerlinGermany Institut für Chemie Neuer Materialien Fachbereich Biologie/ChemieUniversität OsnabrückBarbarastraße 749076 OsnabrückGermany

High sensitizer and activator concentrations have been increasingly examined to improve the performance of multi-color emissive upconversion(UC)nanocrystals(UCNC)like NaYF_(4):Yb,Er and first strategies were reported to reduce concentration quenching in highly doped *** luminescence(UCL)is,however,controlled not only by dopant concentration,yet by an interplay of different parameters including size,crystal and shell quality,and excitation power density(P).Thus,identifying optimum dopant concentrations requires systematic studies of UCNC designed to minimize additional quenching pathways and quantitative ***,we quantify the dopant concentration dependence of the UCL quantum yield(ΦUC)of solid NaYF_(4):Yb,Er/NaYF_(4):Lu upconversion core/shell nanocrystals of varying Yb3+and Er3+concentrations(Yb3+series:20%‒98%Yb3+;2%Er3+;Er3+series:60%Yb3+;2%‒40%Er3+).To circumvent other luminescence quenching processes,an elaborate synthesis yielding OH-free UCNC with recordΦUC of~9%and~25 nm core particles with a thick surface shell were *** Yb3+concentrations barely reduceΦUC from~9%(20%Yb3+)to~7%(98%Yb3+)for an Er3+concentration of 2%,thereby allowing to strongly increase the particle absorption cross section and UCNC *** an increased Er3+concentration reducesΦUC from~7%(2%Er3+)to 1%(40%)for 60%Yb3+.Nevertheless,at very high P(>1 Mw/cm^(2))used for microscopic studies,highly Er3+-doped UCNC display a high brightness because of reduced *** findings underline the importance of synthesis control and will pave the road to many fundamental studies of UC materials.

关键词： highly doped upconversion nanocrystals core/shell nanoparticles upconversion luminescence efficiency NaYF_(4):Yb Er concentration quenching

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Combination of OCT and Raman spectroscopy for improved characterization of atherosclerotic plaque depositions

引用

Chinese Optics Letters 2017年第9期15卷 31-35页

作者： Kokila Egodage christian Matthaus Sebastian Dochow Iwan w.Schie Carmen Hardtner Ingo Hilgendorf Jürgen Popp Leibniz Institute of Photonic Technology Albert Einstein Straβe 9Jena 07745Germany Institute of Physical Chemistry and Abbe Center of Photonics Friedrich-Schiller-UniversityJena 07743Germany University Heart Center Freiburg Department of Cardiology and Angiology IFaculty of MedicineUniversity of FreiburgGermany

The biochemical composition of atherosclerotic plaques is closely related to plaque stability and, therefore, to the associated risk of plaque evolution and rupture. Combinations of current imaging modalities, such as optical coherence tomography（OCT） with spectroscopic methods, therefore offer the possibility of concurrently obtaining morphological as well as chemical information. Raman spectroscopy is one of the most promising techniques that can be combined with intravascular imaging modalities. A microscopy setup merging both techniques has been applied to characterize plaque depositions of a human aorta affected by the disease. Calcified depositions were clearly identified and subsequently confirmed by histopathology.

关键词： Combination of OCT and Raman spectroscopy for improved characterization of atherosclerotic plaque depositions

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Predicting the inhibition efficiencies of magnesium dissolution modulators using sparse machine learning models

引用

npj Computational Materials 2021年第1期7卷 1783-1791页

作者： Elisabeth J.Schiessler Tim würger Sviatlana V.Lamaka Robert H.Meißner christian J.Cyron Mikhail L.Zheludkevich christian Feiler Roland C.Aydin Institute of Material Systems Modeling Helmholtz-Zentrum HereonGeesthachtGermany Institute of Surface Science Helmholtz-Zentrum HereonGeesthachtGermany Institute of Polymers and Composites Hamburg University of TechnologyHamburgGermany Institute for Continuum and Material Mechanics Hamburg University of TechnologyHamburgGermany Institute for Materials Science Faculty of EngineeringKiel UniversityKielGermany

The degradation behaviour of magnesium and its alloys can be tuned by small organic ***,an automatic identification of effective organic additives within the vast chemical space of potential compounds needs sophisticated ***,we propose two systematic approaches of sparse feature selection for identifying molecular descriptors that are most relevant for the corrosion inhibition efficiency of chemical *** is based on the classical statistical tool of analysis of variance,the other one based on random *** demonstrate how both can—when combined with deep neural networks—help to predict the corrosion inhibition efficiencies of chemical compounds for the magnesium alloy *** particular,we demonstrate that this framework outperforms predictions relying on a random selection of molecular ***,we point out how autoencoders could be used in the future to enable even more accurate automated predictions of corrosion inhibition efficiencies.

关键词： corrosion alloy magnesium

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Existence of global solutions to isentropic gas dynamics equations with a source term

引用

Science China Mathematics 2010年第1期53卷 115-124页

作者： KLINGENBERG christian Institut fr angewandte Mathematik Universitt WrzburgAm Hubland97074 WrzburgGermany

In this paper we prove existence of isentropic gas dynamic equations with a source term (1.2). To this end we construct a sequence of regular hyperbolic systems (1.1) to approximate the inhomogeneous system of isentropic gas dynamics (1.2). First,for each fixed approximation parameter δ and very general condition on P (ρ),we establish the existence of entropy solutions for the Cauchy problem (1.1) with bounded initial date (1.4). Second,letting=o(δ),we obtain a complete proof of the H-1loc compactness of weak entropy pairs of system (1.2) in the form η(ρ,u) =ρH(ρ,u) given in Chen-LeFloch (2003). Finally,for the conditions of P(ρ) given in Chen-LeFloch (2003),applied to the results in Theorems 1 and 2,we obtain the global existence of entropy solutions for the Cauchy problem (1.2) with bounded initial date (1.4).

关键词： isentropic gas dynamics system global entropy solution compactness in H-loc1 compensated compactness method

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：