检索结果-南通市图书馆

Saturn＇s gravitational field induced by its equatorially antisymmetric zonal winds

Research in Astronomy and Astrophysics 2018年第5期18卷 29-36页

作者： dali Kong Keke Zhang Gerald Schubert john d.Anderson Key Laboratory of Planetary Sciences Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai 200030 China College of Engineering Mathematics and Physical Sciences University of Exeter Exeter EX4 4QF UK Lunar and Planetary Science Laboratory Macao University of Science and Technology Macao China department of Earth Planetary and Space Sciences University of California Los Angeles CA 90095-1567 USA Jet Propulsion Laboratory 4800 Oak Grove Drive Pasadena CA 91109 USA

The cloud-level zonal winds of Saturn are marked by a substantial equatorially antisymmetric component with a speed of about 50 m s^-1 which, if they are sufficiently deep, can produce measurable odd zonal gravitational coefficients △J2 k＋1, k = 1, 2, 3, 4. This study, based on solutions of the thermal-gravitational wind equation, provides a theoretical basis for interpreting the odd gravitational coefficients of Saturn in terms of its equatorially antisymmetric zonal flow. We adopt a Saturnian model comprising an ice-rock core, a metallic dynamo region and an outer molecular envelope. We use an equatorially antisymmetric zonal flow that is parameterized, confined in the molecular envelope and satisfies the solvability condition required for the thermal-gravitational wind equation. The structure and amplitude of the zonal flow at the cloud level are chosen to be consistent with observations of *** calculate the odd zonal gravitational coefficients △J2k＋1, k = 1, 2, 3, 4 by regarding the depth of the equatorially antisymmetric winds as a parameter. It is found that △J3 is-4.197 × 10^-8 if the zonal winds extend about 13 000 km downward from the cloud tops while it is-0.765 × 10^-8 if the depth is about 4000 km. The depth/profile of the equatorially antisymmetric zonal winds can eventually be estimated when the high-precision measurements of the Cassini Grand Finale become available.

关键词： gravitation - planets and satellites individual (Saturn) - planets and satellites interiors

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

Investigation of active vibration drilling using acoustic emission and cutting size analysis

引用

Journal of Rock Mechanics and Geotechnical Engineering 2018年第2期10卷 390-401页

作者： Yingjian Xiao Charles Hurich john Molgaard Stephen d.Butt Faculty of Engineering and Applied Science Memorial University of Newfoundland department of Earth Sciences Memorial University of Newfoundland

This paper describes an investigation of active bit vibration on the penetration mechanisms and bit-rock interaction for drilling with a diamond impregnated coring bit. A series of drill-off tests(dOTs) were conducted where the drilling rate-of-penetration(ROP) was measured at a series of step-wise increasing static bit thrusts or weight-on-bits(WOBs). Two active dOTs were conducted by applying 60 Hz axial vibration at the bit-rock interface using an electromagnetic vibrating table mounted underneath the drilling samples, and a passive dOT was conducted where the bit was allowed to vibrate naturally with lower amplitude due to the compliance of the drilling sample mountings. during drilling, an acoustic emission(AE) system was used to record the AE signals generated by the diamond cutter penetration and the cuttings were collected for grain size analysis. The instrumented drilling system recorded the dynamic motions of the bit-rock interface using a laser displacement sensor, a load cell, and an LVdT(linear variable differential transformer) recorded the dynamic WOB and the ROP, respectively. Calibration with the drilling system showed that rotary speed was approximately the same at any given WOB, facilitating comparison of the results at the same WOB. Analysis of the experimental results shows that the ROP of the bit at any given WOB increased with higher amplitude of axial bit-rock vibration, and the drill cuttings increased in size with a higher ROP. Spectral analysis of the AEs indicated that the higher ROP and larger cutting size were correlated with a higher AE energy and a lower AE frequency. This indicated that larger fractures were being created to generate larger cutting size. Overall, these results indicate that a greater magnitude of axial bit-rock vibration produces larger fractures and generates larger cuttings which, at the same rotary speed, results in a higher ROP.

关键词： Active bit vibration diamond coring drilling drill-off tests(dOTs) Acoustic emission(AE) drilling performance Penetration mechanism Cutting size analysis

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

A model of Saturn inferred from its measured gravitational field

引用

Research in Astronomy and Astrophysics 2018年第4期18卷 7-14页

We present an interior model of Saturn with an ice-rock core,a metallic region,an outer molecular envelope and a thin transition layer between the metallic and molecular *** shape of Saturn’s 1 bar surface is irregular and determined fully self-consistently by the required equilibrium *** the ice-rock core is assumed to have a uniform density,three different equations of state are adopted for the metallic,molecular and transition *** Saturnian model is constrained by its known mass,its known equatorial and polar radii,and its known zonal gravitational coefficients,J_（2n）,n=1,2,*** model produces an ice-rock core with equatorial radius 0.203 R_S,where R_S is the equatorial radius of Saturn at the 1-bar pressure surface;the core densityρ_c=10388.1 kgm^（3）corresponding to 13.06 Earth masses;and an analytical expression describing the Saturnian irregular shape of the 1-bar pressure *** model also predicts the values of the higher-order gravitational coefficients,J_8,J_10 and J_12,for the hydrostatic Saturn and suggests that Saturn’s convective dynamo operates in the metallic region approximately defined by 0.2 R_S

关键词： gravitation — planets and satellites individual(Saturn) — planets and satellites interiors

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

高、低核酸含量原核生物应对资源可利用性降低和原生动物选择性摄食的适应性策略

引用

中国科学：地球科学 2024年第6期54卷 1901-1913页

作者：胡晨余柳倩陈晓炜刘纪化张瑶 john BATT 肖喜林石蔷张锐骆庭伟焦念志徐大鹏厦门大学环境与生态学院厦门361102 近海海洋环境科学国家重点实验室厦门大学海洋与地球学院福建省海洋碳汇重点实验室厦门361102 Joint Lab for Ocean Research and Education(LORE)of dalhousie University Canadaand Shandong University and Xiamen UniversityXiamen 361102China 香港科技大学(广州)地球与海洋大气科学学域广州510000 山东大学海洋研究院青岛266237 department of Oceanography Dalhousie UniversityHalifaxNova Scotia B3H 4R2Canada 深圳大学高等研究院深圳518060 厦门大学碳中和创新研究中心厦门361102

原核生物在全球海洋生物地球化学循环中发挥重要作用,然而对它们不同生态亚群(即:高核酸(HNA)和低核酸(LNA)含量亚群)的丰度和代谢活性,以及它们的调控因素如何随着海洋环境条件的变化而变化,仍知之甚少.我们在117,000升的大体积培养体... 详细信息

原核生物在全球海洋生物地球化学循环中发挥重要作用,然而对它们不同生态亚群(即:高核酸(HNA)和低核酸(LNA)含量亚群)的丰度和代谢活性,以及它们的调控因素如何随着海洋环境条件的变化而变化,仍知之甚少.我们在117,000升的大体积培养体系中进行了73天的培养实验,深入研究HNA和LNA亚群对资源可利用性降低和原生动物选择性摄食随时间变化的动态响应.研究结果显示,当培养环境资源充足时, HNA亚群的代谢活性高于LNA亚群,但随着资源日益稀缺, HNA亚群代谢下降速度比LNA亚群快,从而使LNA亚群对原核生物活性的贡献稳步增加.与此同时,随着培养体系资源可利用性逐步降低,原生动物的摄食偏好从HNA亚群转向LNA亚群,使得LNA亚群对培养体系的碳流贡献增加.这些结果突显了LNA亚群在资源有限环境中的韧性,阐明了原生动物选择性摄食在资源条件变化时平衡不同亚群中的关键作用,并展示了在不同环境背景下原生动物和原核生物之间复杂的相互适应性.

关键词：微生物环大体积培养实验原核生物自上而下和自下而上调控作用碳流

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

Evolution-aided engineering of plant specialized metabolism

引用

aBIOTECH 2021年第3期2卷 240-263页

作者： Mohammad Irfan Benjamin Chavez Paride Rizzo john C.d'Auria Gaurav d.Moghe Plant Biology Section School of Integrative Plant ScienceCornell UniversityIthacaNYUSA Metabolic diversity Group Leibniz Institute of Plant Genetics and Crop Plant Research(IPK)06466 SeelandGermany

The evolution of new traits in living organisms occurs via the processes of mutation,recombination,genetic drift,and *** processes that have resulted in the immense biol ogical diversity on our planet are also being employed in metabolic engineering to optimize enzymes and pathways,create new-to-nature reactions,and synthesize complex natural products in heterologous *** this review,we discuss two evolution-aided strategies for metabolic engineering-directed evolution,which improves upon existing genetic templates using the evolutionary process,and combinatorial pathway reconstruction,which brings together genes evolved in different organisms into a single heterol ogous *** discuss the general principles of these strategies,describe the technologies involved and the molecular traits they influence,provide examples of their use,and discuss the roadblocks that need to be addressed for their wider adoption.A better understanding of these strategies can provide an impetus to research on gene function discovery and biochemical evolution,which is foundational for improved metabolic *** evolution-aided approaches thus have a substantial potential for improving our understanding of plant metabolism in general,for enhancing the production of plant metabolites,and in sustainable agriculture.

关键词： Evolution Metabolic engineering Plant biotechnology Synthetic biology

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

Structural health monitoring of bridges in the State of Connecticut

引用

Earthquake Engineering and Engineering Vibration 2008年第4期7卷 427-437页

作者： Chengyin Liu Joshua Olund Alan Cardini Paul d＇Attilio Eric Feldblum john deWolf SP-SELLS Inc. Briarcliff Manor NY 10510 USA department of Civil and Environmental Engineering University of Connecticut 261 Glenbrook Rd Unit 2037 Storrs CT06269 USA dMJM Harris Boston MA 02110 USA Connecticut department of Transportation 280 West Street Rocky Hill CT 06067 USA

A joint effort between the Connecticut department of Transportation and the University of Connecticut has been underway for more than 20 years to utilize various structural monitoring approaches to assess different bridges in Connecticut. This has been done to determine the performance of existing bridges, refine techniques needed to evaluate different bridge components, and develop approaches that can be used to provide a continuous status of a bridge＇s structural integrity. This paper briefly introduces the background of these studies, with emphasis on recent research and the development of structural health monitoring concepts. This paper presents the results from three different bridge types： a post-tensioned curved concrete box girder bridge, a curved steel box-girder bridge, and a steel multi-girder bridge. The structural health monitoring approaches to be discussed have been successfully tested using field data collected during multi-year monitoring periods, and are based on vibrations, rotations and strains. The goal has been to develop cost-effective strategies to provide critical information needed to manage the State of Connecticut＇s bridge infrastructure.

关键词： structural integrity structural health monitoring field data vibrations

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

Quantifying spatiotemporal variability in occupant exposure to an indoor airborne contaminant with an uncertain source location

引用

Building Simulation 2023年第6期16卷 889-913页

作者： john E.Castellini Jr Cary A.Faulkner Wangda Zuo Michael d.Sohn department of Mechanical Engineering University of Colorado BoulderUCB 427BoulderCO80309USA department Architectural Engineering The Pennsylvania State UniversityUniversity ParkPA16802USA National Renewable Energy National Laboratory GoldenCO80401USA Energy Analysis and Environmental Impacts division Lawrence Berkeley National Laboratory1 Cyclotron RoadBerkeleyCA94720USA

Well-mixed zone models are often employed to compute indoor air quality and occupant *** effective,a potential downside to assuming instantaneous,perfect mixing is underpredicting exposures to high intermittent concentrations within a *** such cases are of concern,more spatially resolved models,like computational-fluid dynamics methods,are used for some or all of the ***,these models have higher computational costs and require more input information.A preferred compromise would be to continue with a multi-zone modeling approach for all rooms,but with a better assessment of the spatial variability within a *** do so,we present a quantitative method for estimating a room’s spatiotemporal variability,based on influential room *** proposed method disaggregates variability into the variability in a room’s average concentration,and the spatial variability within the room relative to that *** enables a detailed assessment of how variability in particular room parameters impacts the uncertain occupant *** demonstrate the utility of this method,we simulate contaminant dispersion for a variety of possible source *** compute breathing-zone exposure during the releasing(source is active)and decaying(source is removed)*** CFd methods,we found after a 30 minutes release the average standard deviation in the spatial distribution of exposure was approximately 28%of the source average exposure,whereas variability in the different average exposures was lower,only 10%of the total *** also find that although uncertainty in the source location leads to variability in the average magnitude of transient exposure,it does not have a particularly large influence on the spatial distribution during the decaying period,or on the average contaminant removal *** systematically characterizing a room’s average concentration,its variability,and the spatial variability within the room important insights can be gain

关键词： uncertainty variability airborne contaminant spatiotemporal variability well-mixed heterogeneity

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

Regression of recurrent granulosa cell tumor liver metastases following selective internal radiation therapy

引用

Hepatobiliary & Pancreatic diseases International 2023年第4期22卷 406-408页

作者： Omar A Mownah john d Leahy Jeffrey Summers Stephen M Gregory Nigel d Heaton Institute of Liver Studies King’s Healthcare PartnersKing’s College Hospital NHS Foundation TrustDenmark HillLondon SE59RSUK department of Oncology Maidstone and Tunbridge Wells NHS TrustMaidstone ME169QQUK

Granulosa cell tumor(GCT)is the most common sex cordstromal tumor,comprising 5%of all ovarian malignancies[1].The disease course is indolent,and the majority of cases present at stage ***,metastases may develop with potential sites being peritoneum,lung,brain,liver and bone[2].due to the rarity of the disease,published evidence for management of granulosa cell tumor liver metastases(GCTLM)is *** resection is the optimal treatment in instances where there is a high chance of achieving complete resection[3].With regards to unresectable GCTLM there is a paucity of evidence to guide treatment strategy.

关键词： metastases liver lung

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

Wafer-scale quasi-layered tungstate-doped polypyrrole film with high volumetric capacitance

引用

Nano Research 2023年第4期16卷 4895-4900页

作者： Huabo Liu Jiaxing Liang john Watt Richard d.Tilley Rose Amal da-Wei Wang School of Chemical Engineering University of New South WalesSydneyNSW 2052Australia 2 Center for Integrated NanotechnologiesLos Alamos National LaboratoryLos AlamosNW 87545USA 3 School of ChemistryUniversity of New South WalesSydneyNSW 2052Australia

Layered materials are particularly attractive for supercapacitors because of their unique physical,electrical and chemical ***,we demonstrate a facile and scalable electrochemical deposition method for wafer-scale synthesis of quasilayered tungstate-doped polypyrrole films(named TALPy)with controllable thickness and *** as-prepared TALPy film exhibits a high gravimetric density and excellent volumetric capacitance,exceeding many high-performing carbon-and polymerbased film *** on combined results of ex-situ X-ray diffraction(XRd),Raman and X-ray photoelectron spectroscopy(XPS),it is determined that TALPy stores charge through an ion intercalation process accompanied by change in oxidation states of polypyrrole backbone,which is referred as intercalation *** these results suggest the great promise of electrochemical deposition as a scalable and controllable bottom-up approach for synthesizing quasi-layered conductive organic-inorganic hybrid films for electrochemical energy storage applications with high volumetric performance.

关键词： electrochemical deposition conductive polymer polypyrrole organic-inorganic hybrid supercapacitor intercalation pseudocapacitance

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

Calculation and interpretation of classical turning surfaces in solids

引用

npj Computational Materials 2021年第1期7卷 229-238页

作者： Aaron d.Kaplan Stewart J.Clark Kieron Burke john P.Perdew department of Physics Temple UniversityPhiladelphiaPA 19122USA Centre for Materials Physics Durham UniversityDurham DH13LEUK departments of Chemistry and Physics University of CaliforniaIrvineCA 92697USA departments of Physics and Chemistry Temple UniversityPhiladelphiaPA 19122USA

Classical turning surfaces of Kohn–Sham potentials separate classically allowed regions(CARs)from classically forbidden regions(CFRs).They are useful for understanding many chemical properties of molecules but need not exist in solids,where the density never decays to *** equilibrium geometries,we find that CFRs are absent in perfect metals,rare in covalent semiconductors at equilibrium,but common in ionic and molecular *** all materials,CFRs appear or grow as the internuclear distances are uniformly *** can also appear at a monovacancy in a *** with several approximate density functionals and codes confirm these behaviors.A classical picture of conduction suggests that CARs should be connected in metals,and disconnected in wide-gap insulators,and is confirmed in the limits of extreme compression and ***,many semiconductors have no CFR at equilibrium,a key finding for density functional ***,a strong correlation with insulating behavior can still be ***,equilibrium bond lengths for all cases can be estimated from the bond type and the sum of the classical turning radii of the free atoms or ions.

关键词： turning solids expanded

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

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：