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Sol-gel derived nanocrystalline and mesoporous barium strontium titanate prepared at room temperature

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Particuology 2011年第3期9卷 235-242页

作者： Mohammad Reza Mohammadi derek j.Fray Department of Materials Science & Engineering Sharif University of Technology Department of Materials Science & Metallurgy University of Cambridge

Perovskite-type barium strontium titanate （BST） thin films and powders with nanocrystalline and mesoporous structure were prepared by a straightforward particulate sol-gel route at room temperature. The prepared sol had a narrow particle size distribution of about 20 nm. X-ray diffraction （XRD） revealed that phase composition and preferable orientation growth of BST depended upon the annealing temperature. Transmission electron microscope （TEM） images showed that the crystallite size of the powders decreased with increasing annealing temperature from 8 nm at 25 ℃ down to 5 nm at 800 ℃. Field emission scanning electron microscope （FE-SEM） analysis and atomic force microscope （AFM） images revealed that BST thin films had mesoporous and nanocrystafiine structure with average grain size of 3Onm at 600 ℃. Based on Brunauer-Emmett-Teller （BET） analysis, the synthesized BST showed mesoporous structure containing nnres with needle, and nlate shanes and BET surface area in the range of 49-32 m^2/g at 500-800℃

关键词： Barium strontium titanate Room temperature Sol-gel chemistry Nanostructure

Template-based growth of titanium dioxide nanorods by a particulate sol-electrophoretic deposition process

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Particuology 2011年第2期9卷 161-169页

作者： Mohammad Reza Mohammadi Farideh Ordikhani derek j.Fray Farzad Khomamizadeh Department of Materials Science & Engineering Sharif University of Technology Department of Materials Science & Metallurgy University of Cambridge

TiO2 nanorods have been successfully grown into a track-etched polycarbonate （PC） membrane by a particulate sol-electrophoretic deposition from an aqueous medium. The prepared sols had a narrow particle size distribution around 17 nm and excellent stability against aging, with zeta potentials in the range of 47-50 mV at pH 2. It was found that TiO2 nanorods were grown from dilute aqueous sol with a low, 0.1-M concentration. Fourier transform infrared spectroscopy （FT-IR） analysis confirmed that a full conversion of titanium isopropoxide was obtained by hydrolysis, resulting in the formation of TiO2 particles. X-ray diffraction （XRD） results revealed that TiO2 nanorods dried at 100℃ were a mixture of anatase and brookite phases, whereas they were a mixture of anatase and futile structures at 500℃. Moreover, the rutile content of the TiO2 nanorods was higher than that of TiO2 powders. Transmission electron microscope （TEM） images confirmed that TiO2 nanorods had a smooth morphology and longi- tudinal uniformity in diameter. Field emission scanning electron microscope （FE-SEM） images showed that TiO2 nanorods grown by sol-electrophoresis from the dilute aqueous sol had a dense structure with a uniform diameter of 200 rim, containing small particles with an average size of 15 nm. Simultaneous differential thermal （SDT） analysis verified that individual TiO2 nanorods, grown into a PC template, were obtained after annealing at 500℃. Based on kinetic studies, it was found that uniform TiO2 nanorods with high-quality morphology were obtained under optimum conditions at an applied potential of 0.3 V/cm and a deposition time of 60 min.

关键词： Nanorod Crystal morphology Electrophoretic deposition Sol-electrophoresisTitanium dioxide

Bank erosion in an Andean páramo river system: Implications for hydro-development and carbon dynamics in the neotropical Andes

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journal of Mountain Science 2019年第2期16卷 243-255页

作者： derek j.MARTIN Christopher ELY Beverley C.WEMPLE Department of Geography and Planning Appalachian State University Department of Geography University of Vermont

The páramo of the Northern Andes provide critically important ecosystem services to the Northern Andean region in the form of water provisioning and carbon sequestration, both of which are a result of the páramo?s organic-rich soils. Little is known, however, about the hydro-geomorphic characteristics of the rivers that drain these ecosystems. With impending plans for widespread hydro-development and increasing implementation of carbon-sequestering compensation for ecosystem services programs in the region it is imperative that we develop a thorough understanding of the hydrogeomorphic role that rivers play in this unique ecosystem. The objective of this study was to quantify bank erosion along an Amazonian headwater stream draining a small, relatively undisturbed páramo catchment to gain a better understanding of the natural erosion regime and the resulting sediment contributions from this unique ecosystem. This study implemented a combination of field, laboratory, and Geographic Information Systems techniques to quantify bank erosion rates and determine a bank erosion sediment yield from the Ningar River, a small páramo catchment(22.7 km^2) located in the eastern Andean cordillera of Ecuador. Results show that bank erosion rates range from 3.0 to ≥ 390.0 mm/yr, are highly episodic, and yield at least 487 tons of sediment annually to the Ningar River. These results imply that 1) páramo ecosystems substantially contribute to the sediment load of the Amazon River basin; 2) bank erosion is a potentially significant flux component of basin-scale carbon cycles in páramo ecosystems; and 3) hydrologic alteration campaigns(dam building) will likely critically alter these contributions and concomitantly disconnect a critical source of sediment and nutrients to downstream ecosystems.

关键词： Bank erosion Páramo Fluvial geomorphology Andes

Generalized Baumslag-Solitar Graphs with Soluble Fundamental Groups

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Algebra Colloquium 2014年第1期21卷 53-58页

作者： Alberto L. Delgado derek j.S. Robinson Mathew Timm vDepartment of Mathematics illinois State University Normal IL 61790 USA Department of Mathematics University of Illinois at Urbana-Champaign Urbana IL 61801 USA Department of Mathematics Bradley University Peoria IL 61625 USA

It is shown that the generalized Baumslag-Solitar graphs which have soluble fundamental groups can be constructed from four simple types of graph by a process of decoration. The method of proof is elementary and emplo... 详细信息

关键词： generalized Baumslag-Solitar graph soluble fundamental group

The use of electro-deoxidation in molten salts to reduce the energy consumption of solar grade silicon and increase the output of PV solar cells

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Progress in Natural Science:Materials International 2015年第6期25卷 583-590页

作者： Paul R.Coxon Michael Coto Eimutis juzeliunas derek j.Fray Department of Materials Science & Metallurgy University of Cambridge Institute of Chemistry Centre for Physical Sciences & Technology 3. Klaip?da University

Solar photovoltaics,based upon silicon,are the most popular form of solar cell with efficiencies around 20%.These efficiencies can be further increased by employing light trapping schemes to minimise optical losses through scattering and reflection which enhances the amount of light absorbed and number of photo-carriers *** approaches employ antireflection coatings（ARCs） or texturise the surface of the silicon disks,so that the structure consists of an array of needles which can absorb most of the ***,these structures are created by leaching the silicon with hydrofluoric-based acids or by reactive ion etching（RIE） *** paper reviews some of the methods for improving the energy efficiency of silicon production,and describes the use of electro-deoxidation of SiO;layers,on silicon,in molten calcium chloride to form nanoporous black silicon（b-Si） *** coating b-Si surface with TiO;,a common ARC,extremely black surfaces with negligible reflectance of about 0.1%,are produced,which can have applications for low-cost high efficiency solar cells.

关键词： Black silicon Solar cell photovoltaics Silicon molten salt Electrochemistry

Biopsy of solid liver tumors:adverse consequences

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Hepatobiliary & Pancreatic Diseases International 2008年第3期7卷 325-327页

作者： Dhya Al-Leswas derek A O'Reilly Graeme j Poston Department of Surgery University Hospital Aintree Lower LaneLiverpoolL9 7ALUK

BACKGROUND:Percutaneous radiologically-guided liver biopsy is used routinely worldwide in all secondary- level hospital *** it has an undoubted role in the investigation and management of acute and chronic inflammatory conditions of the liver,its role in hepatic oncology is doubtful and probably dangerous. METHOD:We report on two patients who underwent preoperative biopsy of potentially resectable liver tumors. RESULTS:At the time of surgery,there was evidence of seeding at the biopsy site in both *** case 1,potentially curative liver resection was rendered incurable because of gross peritoneal carcinomatosis lying adjacent to the site of liver *** case 2,the patient underwent curative liver resection,but there was histopathological evidence of peritoneal disease beyond the liver capsule along the falciform ligament at the site of the previous biopsy. CONCLUSIONS:No patient with a suspicious liver tumor which is thought to be malignant and has any possibility of being a potential candidate for liver surgery,should be subjected to pre-operative diagnostic biopsy in a non- specialist center.

关键词： liver biopsy colorectal liver metastases hepatocellular carcinoma

A historical review of the development of verification and validation theories for simulation models

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International journal of Modeling, Simulation, and Scientific Computing 2017年第2期8卷 1-24页

作者： Phillip j.Durst derek T.Anderson Cindy L.Bethel U.S.Army Engineer Research and Development Center 3909 Halls Ferry Road Vicksburg MS 39180USA Mississippi State University Department of Electrical and Computer Engineering Mississippi StateMS 39759USA Mississippi State University Department of Computer Science and Engineering Mississippi StateMS 39759USA

Modeling and simulation(M&S)play a critical role in both engineering and basic research ***-based models have existed since the 1950s,and those early models have given way to the more complex computational and physics-based simula-tions used *** such,a great deal of research has been done to establish what level of trust should be given to simulation outputs and how to verify and validate the mod-els used in these *** paper presents an overview of the theoretical work done to date defining formal definitions for,and methods of,verification and validation(V&V)of computer *** models are broken down into three broad cate-gories:analytical and simulation models,computational and physics-based models,and simulations of autonomous systems,and the unique theories and methods developed to address V&V of these models are *** paper also presents the current prob-lems in the theoretical field of V&V for models as simulations move from single system models and simulations to more complex simulation *** particular,this paper high-lights the lack of agreed-upon methods for V&V of simulations of autonomous systems,such as an autonomous unmanned vehicles,and proposes some next steps needed to address this problem.

关键词： Verification and validation simulation models computational models physics-based simulations autonomous systems.

Core needle biopsy and embolization of fat-poor renal tumors in children with tuberous sclerosis complex

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World journal of Pediatrics 2023年第6期19卷 614-618页

作者： derek j.Roebuck Samantha Chippington Bligh D.Berry Craig Gibson Department of Medical Imaging Perth Children's Hospital15 Hospital AvenueNedlands 6009Australia Division of Paediatrics Medical SchoolUniversity ofWestern AustraliaCrawley 6009Australia Department of Radiology Great Ormond Street Hospital for ChildrenLondon WCIN 3JHUK PathWest Laboratory Medicine WA Murdoch 6150Australia

Tuberous sclerosis complex(TSC)is an autosomal dominant disease caused by inactivating germline mutations in TSC1 or *** genes code for hamartin and tuberin,proteins that normally form a complex that down-regulates the mechanistic(or mammalian)target of rapamycin(mTOR)pathway,which is crucial to cell growth,proliferation and survival.

关键词： needle sclerosis biopsy

Kinematic calibration of a class of parallel kinematic machines(PKM) with fewer than six degrees of freedom

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Science China(Technological Sciences) 2003年第5期46卷 515-526页

作者：黄田唐国宝李思维李亚 G.derek Chetwynd j.David Whitehouse School of Mechanical Engineering Tianjin University Tianjin 300072 China School of Engineering The University of Warwick Coventry CV4 7AL UK

By taking a 3-DOF translational milling machine as an example, this paper investigates the kinematic calibration of PKM systems with fewer than 6-DOF. The error mapping function is formulated in such a way that the geometric errors affecting the compensatable and uncompensatable pose errors can be separated. Based upon the previous investigation, a hierarchical approach to the geometric error identification is proposed. The compensation strategy is developed which is particularly suitable for the PKM systems with translational moving capability. The experiment has been carried out to verify the effectiveness of the proposed approach and the results show that the accuracy can be significantly improved.

关键词： parallel kinematic machines, kinematic calibration, degrees of freedom.