检索结果-南通市图书馆

Research progress on geosynchronous synthetic aperture radar

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Fundamental Research 2021年第3期1卷 346-363页

作者： Cheng Hu Zhiyang Chen Yuanhao Li Xichao Dong stephen hobbs The School of Information and Electronics Beijing Institute of TechnologyBeijing 100081China Advanced Technology Research Institute Beijing Institute of TechnologyJinan 250300China The Key Laboratory of Electronic and Information Technology in Satellite Navigation(Beijing Institute of Technology) Ministry of EducationBeijing 100081China Department of Geoscience and Remote Sensing Delft University of Technology2628 Delftthe Netherlands Beijing Institute of Technology Chongqing Innovation Center Chongqing 401120China The School of Aerospace Transport&Manufacturing Cranfield UniversityUK

Based on its ability to obtain two-dimensional(2D)high-resolution images in all-time and all-weather conditions,spaceborne synthetic aperture radar(SAR)has become an important remote sensing technique and the study of such systems has entered a period of vigorous *** imaging modes such as radar interferometry,tomography,and multi-static imaging,have been ***,current in-orbit spaceborne SARs,which all operate in low Earth orbits,have relatively long revisit times ranging from several days to dozens of days,restricting their temporal sampling *** SAR(GEO SAR)is an active research area because it provides significant new capability,especially its much-improved temporal *** paper reviews the research progress of GEO SAR technologies in *** typical orbit schemes are presented,followed by the corresponding key issues,including system design,echo focusing,main disturbance factors,repeat-track interferometry,etc,inherent to these *** analysis and solution research of the above key issues are *** SAR concepts involving multiple platforms are described,including the GEO SAR constellation,GEO-LEO/airborne/unmanned aerial vehicle bistatic SAR,and formation flying GEO SAR(FF-GEO SAR).Due to the high potential of FF-GEO SAR for three-dimensional(3D)deformation retrieval and coherence-based SAR tomography(TomoSAR),we have recently carried out some research related to FF-GEO *** research,which is also discussed in this paper,includes developing a formation design method and an improved TomoSAR processing *** is found that GEO SAR will continue to be an active topic in the aspect of data processing and multi-platform concept in the near future.

关键词： Geosynchronous synthetic aperture radar(GEO SAR) Orbit scheme Disturbance factors Echo focusing Formation flying

The GABA Antagonist Picrotoxin Attenuates an Ethanol-Induced Taste Aversion in Taste Aversion-Prone Rats

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

Neuroscience & Medicine 2011年第4期2卷 363-369页

作者： Joseph Tkacz stephen hobbs Ralph Elkins 不详

The aversive properties of alcohol can be examined by using ethanol as a conditioning agent in a taste aversion (TA) paradigm. However, there is often variability in how organisms respond to the aversive properties of alcohol. Using a selectively bred line of TA-prone (TAP) rats, the present study sought to determine if antagonizing the GABA receptor complex with picrotoxin could block the acquisition of an ethanol-based conditioned aversion to a normally preferred fluid. Fifty TAP rats were randomly divided into 5 groups. In the two experimental groups, rats were pretreated with i.p. injections of low or high doses of the GABA Aantagonist picrotoxin prior to undergoing taste aversion conditioning —wherein consumption of a novel saccharin solution (0.1%) was followed by an i.p. injection of ethanol (1.5 mg/kg). In the primary control group, rats were treated identically, except that isotonic saline was substituted for picrotoxin. In the non-conditioning and pseudo-conditioning control groups, rats did not receive an ethanol-saccharin pairing but did receive a picrotoxin injection. Repeated measures ANOVA revealed that animals in the picrotoxin groups displayed significantly weaker TAs than the primary control group (p 0.05) as measured by post-conditioning, two-bottle saccharin preference scores. Picrotoxin hinders the acquisition of an ethanol-induced TA, thereby supporting the hypothesis that the GABA system plays a central role in ethanol’s motivational effects. Possible mechanisms include 1) picrotoxin attenuates negative effects of ethanol, 2) picrotoxin interferes with the central associative processes that promote TA conditioning or 3) some combination of 1 and 2.

关键词： Conditioned Taste Aversion Ethanol GABA Picrotoxin Rats

Transient-state instability analysis of dissolution-timescale reactive infiltration in fluid-saturated porous rocks: Purely mathematical approach

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

Science China(Technological Sciences) 2020年第2期63卷 319-328页

作者： ZHAO ChongBin hobbs Bruce ORD Alison Computational Geosciences Research Centre Central South UniversityChangsha 410083China Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring Ministry of EducationCentral South UniversityChangsha 410083China School of Earth and Environment The University of Western AustraliaCrawleyWA 6009Australia

This paper deals with how the purely mathematical approach can be used to solve transient-state instability problems of dissolution-timescale reactive infiltration(DTRI) in fluid-saturated porous rocks. Three key steps involved in such an approach are:(1) to mathematically derive an analytical solution(known as the base solution or conventional solution) for a quasi-steady state problem of the dissolution timescale, which is viewed as a frozen state of the original transient-state instability problem;(2)to mathematically deduce a group of first-order perturbation partial-differential equations(PDEs) for the quasi-steady state problem;(3) to mathematically derive an analytical solution(known as the perturbation solution or unconventional solution) for this group of first-order perturbation PDEs. Because of difficulty in mathematically solving a transient-state instability problem of DTRI in general cases, only a special case, in which some nonlinear coupling between governing PDEs of the problem can be decoupled, is considered to illustrate these three key steps in this study. The related theoretical results demonstrated that the transient chemical dissolution front can become unstable in the DTRI system of large Zh numbers when the long wavelength perturbations are applied to the system. This new finding may lay the theoretical foundation for developing innovative technique to exploit shale gas resources in the deep Earth.

关键词： mathematical study dissolution timescale reactive infiltration instability chemical dissolution perturbation solution porous rocks

Near-field performance of chemical dissolution-front instability around a circular acid-injection-well in fluid-saturated porous media

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2023年第7期66卷 2025-2035页

作者： ZHAO ChongBin hobbs Bruce ORD Alison Computational Geosciences Research Centre Central South UniversityChangsha 410083China Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring Ministry of EducationCentral South UniversityChangsha 410083China School of Earth and Environment University of Western AustraliaCrawleyWA 6009Australia

This paper investigates the near-field performance of chemical dissolution-front instability(CDFI) around a circular acidinjection-well in fluid-saturated porous media(FSPM) through using purely mathematical *** the mathematical governing equations of the CDFI problem involving radially divergent flow are briefly described,both analytical base solutions and perturbation solutions for the considered problem are mathematically *** analytical solutions lead to the theoretical expression of the perturbation induced dimensionless growth-rate and the following two new *** first new finding is that the critical Peclet number of a chemical dissolution system(CDS) associated with radially divergent flow in FSPM is not only a function of the permeability ratio between the undissolved and dissolved regions as well as the dimensionless wavenumber,but also a function of the circular chemical dissolution-front location relative to the circular acid-injection-well in *** second new finding is that as the direct result of considering a nonzero radius of the circular acid-injection-well,there exits a critical closeness number,which may be used to assess where the circular chemical dissolution-front starts becoming unstable in the CDS associated with radially divergent *** on these two new findings,a theoretical criterion of two parts has been *** first part of the established theoretical criterion answers the scientific question when a circular chemical dissolution-front can become unstable,while the second part of the established theoretical criterion answers the scientific question where a circular chemical dissolution-front can become *** applying the established theoretical criterion,a long-term existing mystery why the wormhole pattern of fractal nature and the compact pattern of fingering nature are formed at different locations away from the circular acid-injection-well circumference in fluid-saturated carbo

关键词： near-field performance circular injection well radially divergent flow analytical solutions dissolution-front instability porous media

Two different mathematical schemes for solving chemical dissolution-front instability problems in fluid-saturated rocks

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2022年第1期65卷 147-156页

Chemical dissolution-front instability(CDFI)problems usually involve multiple temporal and spatial scales,as well as multiple processes.A key issue associated with solving a CDFI problem in a fluid-saturated rock is to mathematically establish a theoretical criterion,which can be used to judge the instability of a chemical dissolution-front(CDF)propagating in the fluidsaturated *** theoretical paper deals with how two different mathematical schemes can be used to precisely establish such a theoretical criterion in a purely mathematical manner,rather than in a numerical simulation *** main distinguishment between these two different mathematical schemes is that in the first mathematical scheme,a curved surface coordinate system is used,while in the second mathematical scheme,a planar surface coordinate system is *** particular,all the key mathematical deduction steps associated with using these two different mathematical schemes are described and discussed in great *** main theoretical outcomes of this study have demonstrated that(1)two different mathematical schemes under consideration can produce exactly the same theoretical criterion;(2)the main advantage of using the first mathematical scheme is that the interface conditions at the curved interface between the downstream and upstream regions can be easily described mathematically;(3)the main advantage of using the second mathematical scheme is that the first-order perturbation equations of the CDFI problem can be easily described in a purely mathematical manner.

关键词： chemical dissolution theoretical analysis mathematical scheme front instability fluid-saturated rocks

Gravitational wave research using pulsar timing arrays

在线全文

学校读者我要写书评

暂无评论

National Science Review 2017年第5期4卷 707-717页

作者： George hobbs Shi Dai Australia Telescope National Facility CSIRO

A pulsar timing array(PTA) refers to a program of regular, high-precision timing observations of a widely distributed array of millisecond pulsars. Here we review the status of the three primary PTA projects and the joint International Pulsar Timing Array project. We discuss current results related to ultra-low-frequency gravitational wave searches and highlight opportunities for the near future.

关键词： pulsars gravitational waves radio astronomy

A unified theory for sharp dissolution front propagation inchemical dissolution of fluid-saturated porous rocks

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2019年第1期62卷 163-174页

作者： ZHAO ChongBin hobbs Bruce ORD Alison Computational Geosciences Research Centre Central South University School of Earth and Environment The University of Western Australia

This paper presents a unified theory to deal with when, why and how a sharp acidization dissolution front(ADF), which is represented by the porosity distribution curve, can take place in an acidization dissolution system composed of fluid-saturated porous rocks. The theory contains the following main points:(1) A reaction rate of infinity alone can lead to a sharp ADF of the Stefan-type in the acidization dissolution system. This sharp front is unstable when permeability in the downstream region is smaller than that in the upstream region.(2) For a finite reaction rate, when the acid dissolution capacity number approaches zero,the ADF can have a sharp profile of the Stefan-type either on a much smaller time scale or on a much larger time scale than the dissolution time scale. In the former case, the ADF may become unstable on a much larger time scale than the transport time scale, while in the latter case, it may become unstable if the growth rate of a small perturbation is greater than zero.(3) On the dissolution time scale, even if both the reaction rate is finite and the acid dissolution capacity number approaches zero, the profile of an ADF may not be sharp because it is in a transient state. In this case, not only can an ADF change its profile with time, but also its morphology can grow if the growth rate of a small perturbation is greater than zero. Due to the involvement of both the change rate and the growth rate of the ADF profile, it is necessary to conduct a transient linear stability analysis for determining whether or not a time-dependent ADF is stable in the acidization dissolution system.

关键词： sharp dissolution front stationary/steady state transient state acid dissolution capacity acidization dissolution porous rocks

Effects of porosity heterogeneity on chemical dissolution-front instability in fluid-saturated rocks

在线全文

学校读者我要写书评

暂无评论

Journal of Central South University 2017年第3期24卷 720-725页

作者： ZHAO Chong-bin Peter SCHAUBS Bruce hobbs Computational Geosciences Research Centre Central South University Changsha 410083 China CSIRO Mineral Resource National Research Flagship R O. Box 1130 Bentley WA 6102 Australia School of Earth and Environment The University of Western Australia Crawley WA 6009 Australia

Homogeneity and heterogeneity are two totally different concepts in *** the particle length scale,rocks exhibit strong heterogeneity in their constituents and *** the heterogeneity of porosity obeys the random uniform distribution,both the mean value and the variance of porosities in the heterogeneous porosity field can be used to reflect the overall heterogeneous characteristics of the porosity *** main purpose of this work is to investigate the effects of porosity heterogeneity on chemical dissolution front instability in fluid-saturated rocks by the computational simulation *** related computational simulation results have demonstrated that:1) since the propagation speed of a chemical dissolution front is inversely proportional to the difference between the final porosity and the mean value of porosities in the initial porosity field,an increase in the extent of the porosity heterogeneity can cause an increase in the mean value of porosities in the initial porosity field and an increase in the propagation speed of the chemical dissolution front.2) An increase in the variance of porosities in the initial porosity field can cause an increase in the instability probability of the chemical dissolution front in the fluid-saturated rock.3) The greater the mean value of porosities in the initial porosity field,the quicker the irregular morphology of the chemical dissolution front changes in the supercritical chemical dissolution *** means that the irregular morphology of a chemical dissolution front grows quicker in a porosity field of heterogeneity than it does in that of homogeneity when the chemical dissolution system is at a supercritical stage.

关键词： porosity heterogeneity chemical dissolution front instability computational simulation porous rocks

A new alternative approach for investigating acidization dissolution front propagation in fluid-saturated carbonate rocks

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2017年第8期60卷 1197-1210页

作者： ZHAO ChongBin hobbs Bruce ORD Alison Computational Geosciences Research Centre Central South University School of Earth and Environment The University of Western Australia

The natural phenomenon associated with the chemical dissolution of dissolvable minerals of rocks can be employed to develop innovative technology in mining and oil extracting engineering. This paper presents a new alternative approach for theoretically dealing with chemical dissolution front （CDF） propagation in fluid-saturated carbonate rocks. Note that the CDF is represented by the porosity front in this study. In this new approach, the porosity, pore-fluid velocity and acid concentration are directly used as independent variables. To illustrate how to use the present new approach, an aeidization dissolution system （ADS） consisting of carbonate rocks, which belongs to one of the many general chemical dissolution systems （CDSs）, is taken as an application example. When the acid dissolution capacity （ADC） number （that is defined as the ratio of the volume of the carbonate rock dissolved by an acid to that of the acid） approaches zero, the present new approach can be used to obtain analytical solutions for the stable ADS. However, if the ADC number is a nonzero finite number, then numerical solutions can be only obtained for the ADS, especially when the ADS is in an unstable state. The related theoretical results have demonstrated that：（1） When the ADS is in a stable state and in the case of the ADC number approaching zero, the present new approach is mathematically equivalent to the previous approach, in which the porosity, pore-fluid pressure and acid concentration are used as independent variables. However, when the ADS is in an unstable state, the use of the present new approach leads to a free parameter that needs to be determined by some other ways. （2） The existence of a non-step-type dissolution front within a transient region should at least satisfy that none of the ADC number, injected acid velocity and reciprocal of the dissolution reaction rate is equal to zero in the stable ADS.

关键词： acidization dissolution front propagation critical length alternative approach critical time carbonate rocks