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In situ observation of sublimation-enhanced magnesium oxidation at elevated temperature

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Nano Research 2016年第9期9卷 2796-2802页

作者： Zijiao Zhang Xiaoqian Fu Minmin Mao Qian Yu Scott X.Mao Jixue Li Ze Zhang Center of Electron Microscopy and State Key Laboratory of Silicon Materials Department of Materials Science & EngineeringZhejiang UniversityHangzhou 310027China Department of Mechanical Engineering & Materials Science University of PittsburghPittsburghPA 15261USA

Oxidation plays a tremendous role in the long-term performance of metals. As an important lightweight metal for industrial applications, magnesium suffers from its high reactivity with oxygen and increased evaporation at high temperatures. To understand the oxidation mechanism of magnesium at elevated temperatures, in situ environmental transmission electron microscopy (E-TEM) was performed on magnesium nanoparticles. At a relatively low temperature, the growth of a MgO lamellae via the outward diffusion of bulk magnesium atoms dominated the oxidation process. In contrast, a sublimation-enhanced oxidation via gas phase reaction occurred at 200 °C, leading to the growth of MgO dendrites over the particle that finally leads to the degradation of the magnesium structure. This study provides a direct observation and model of the oxidation mechanism of a direct gas–gas reaction that improves our understanding of the oxidation mechanism at elevated temperatures. [Figure not available: see fulltext.] © 2016, Tsinghua University Press and Springer-Verlag Berlin Heidelberg.

关键词： oxidation magnesium sublimation nanoparticle

The sensitivity of snowpack sublimation estimates to instrument and measurement uncertainty perturbed in a Monte Carlo framework

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Frontiers of Earth Science 2018年第4期12卷 728-738页

作者： D.M.HULTSTRAND S.R.FASSNACHT EASC-Watershed Science Colorado State UniversityFort CollinsCO 80523-1482USA ESS-Watershed Science Colorado State UniversityFort CollinsCO 80523-1476USA Cooperative Institute for Research in the Atmosphere Fort CollinsCO 80523-1375USA Geographisches Institut Abt.KartographieGIS &FemerkundungGeorg-August-Universitat Gottingen37077GottingenGermany Natural Resources Ecology Laboratory Fort CollinsCO 80523-1499USA

The bulk aerodynamic flux equation is often used to estimate snowpack sublimation since it requires meteorological measurements at only one height above the snow surface. However, to date the uncertainty of these estimates and the individual input variables and input parameters uncertainty have not been quantified. We modeled sublimation for three (average snowpack in 2005, deep snowpack in 2011, and shallow snowpack in 2012) different water years (October 1 to September 30) at West Glacier Lake watershed within the Glacier Lakes Ecosystem Experiments Site in *** performed a Monte Carlo analysis to evaluate the sensitivity of modeled sublimation to uncertainties of the input variables and parameters from the bulk aerodynamic flux equation. Input variable time series were uniformly adjusted by a normally distributed random variable with a standard deviation given as follows: 1) the manufacturer’s stated instrument accuracy of 0.3°C for temperature (T), 0.3 m/s for wind speed (Uz), 2% for relative humidity (RH), and 1 mb for pressure (P); 2) 0.0093 m for the aerodynamic roughness length (z0) based on z0 profiles calculations from multiple heights; and 3) 0.08 m for measurement height (z). Often z is held constant; here we used a constant z compared to the ground surface, and subsequently altered z to account for the change in snow depth (ds). The most important source of uncertainty was z0, then RH. Accounting for measurement height as it changed due to snowpack accumulation/ablation was also relevant for deeper snow. Snow surface sublimation uncertainties, from this study, are in the range of 1% to 29% for individual input parameter perturbations. The mean cumulative uncertainty was 41% for the three water years with 55%, 37%, and 32% occurring for the wet, average, and low water years. The top three variables (z varying with ds, z0, and RH) accounted for 74% to 84% of the cumulative sublimation uncertainty.

关键词： snow sublimation uncertainty aerodynamic methods

Low-Angle Grain Boundaries in sublimation Grown 6H-SiC Crystals

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Journal of Rare Earths 2006年第Z1期24卷 8-10页

作者： Jiang Shouzhen Li Xianxiang Dong Jie Chen Xiufang Xu Xiangang Hu Xiaobo State Key Laboratory of Crystal Materials Shandong UniversityJinan 250100China

High-resolution X-ray diffractometry(HRXRD)was used to assess the quality of 6H-SiC crystals grown by sublimation *** results show the occurrence of low-angle grain boundaries(LB)is close relative to the inclination of the crystal *** the central faceted region with 0°inclination the crystal is of high structural ***,at the region close to the facet with less than 5°inclination LB occurs slightly and at the region close to the peripheral polytype ring with more than 5°inclination LB defect occurs *** density of LB can be drastically reduced by decreasing radial temperature gradient that determines the shape of the crystal growth interface.

关键词： low-angle grain boundaries sublimation 6H-SiC radial temperature gradient

In Situ Imaging of Layer-by-Layer sublimation of Suspended Graphene

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Nano Research 2010年第1期3卷 43-50页

作者： Jian Yu Huang Liang Qi Ju Li Center for Integrated Nanotechnologies(CINT) Sandia National LaboratoriesAlbuquerqueNew Mexico 87185USA Department of Materials Science and Engineering University of PennsylvaniaPhiladelphiaPennsylvania 19104USA

An individual suspended graphene sheet was connected to a scanning tunneling microscopy probe inside a transmission electron microscope,and Joule heated to high *** high temperatures and under electron beam irradiation,the few-layer graphene sheets were removed layer-by-layer in the viewing area until a monolayer graphene was *** layer-by-layer peeling was initiated at vacancies in individual graphene *** vacancies expanded to form nanometer-sized holes,which then grew along the perimeter and propagated to both the top and bottom layers of a bilayer graphene joined by a bilayer *** layer-by-layer peeling was induced by atom sublimation caused by Joule heating and facilitated by atom displacement caused by high-energy electron irradiation,and may be harnessed to control the layer thickness of graphene for device applications.

关键词： Graphene sublimation in situ electron microscopy vacancy hole bilayer edge

Deposition and characterization of Pd-Ti thin film by sublimation

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Radiation Detection Technology and Methods 2020年第4期4卷 465-471页

作者： Zhang Zhiwei Yang Yuchen Ma Yongsheng Wang Xujian Liu Baiqi He Ping Institute of High Energy Physics Chinese Academy of SciencesBeijing 100049China University of Chinese Academy of Sciences Beijing 100049China

Introduction Pd/Ti double-layer thin film as non-evaporable getter(NEG)was deposited by sublimation,and its activation temperature was as low as 100℃.The Pd film was deposited in situ after Ti deposition to ensure no oxidization on Ti *** speed test and characterization method The pumping speed of the coated pipe was measured by a pumping speed test *** sticking factor was calculated by *** surface morphology was observed by a scanning electron microscope(SEM).The chemical composition of the film was measured by an energy-dispersive spectrum inbuilt with the *** crystalline structure of the film was measured using grazing incidence X-ray *** It was found that the pumping performance of the Pd/Ti film still remained high after 15 times of *** maximum pumping speed after heating at 100℃for 24 h was 1.1 L/s cm^(2)and 0.49 L/s cm^(2)for H_(2)and CO,*** can be concluded that the key to reducing the activation temperature of NEG materials is to enhance the oxidation resistance of the surface of NEG.

关键词： Pd/Ti film Low activation temperature sublimation Non-evaporable getter Ultra-high vacuum

Physical Properties in Drying of Food Products with Combined sublimation and Evaporation

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Chinese Journal of Chemical Engineering 2004年第6期12卷 814-817页

作者： Ingvald Strфmmen Odilio Alves-Filho Trygve M.Eikevik Ingrid C.Claussen Department of Refrigeration and Air Conditioning The Norwegian University of Science and Technology (NTNU) Trondheim NorwaySINTEF Energy Research Department of Refrigeration and Air Conditioning Trondheim NorwaySINTEF Energy Research Department of Refrigeration and Air Conditioning Trondheim NorwayDepartment of Refrigeration and Air Conditioning The Norwegian University of Science and Technology (NTNU) Trondheim Norway

Drying is an important unit operation in processing of biological resources. The drying process may influence the product properties and quality, which may shrink, break or undergo rheological, physical and biochemical changes. The important parameters responsible for such changes are drying conditions, type of drying technology and residence drying time. Thermal conductivity, thermal-mass diffusivity, enthalpy, porosity and density are the main material property and heat-mass transfer parameters, which are essential for understanding the changes in product quality and for designing and dimensioning the drying processes. In this paper physical properties of food products undergoing a combined sublimation and evaporation were studied. Pieces of vegetables and potatoes were dried in a heat pump fluidized bed dryer at combined modes with temperatures below the freezing point in the beginning and a final drying step at temperatures above the freezing point. Samples of products were tested at different moisture contents with respect to physical properties. Physical properties of leek and potato samples were measured and mass diffusivities were determined from drying kinetic data. Based on bulk density and rehydration measurements it was clearly observed that drying temperature and modes influenced the final product physical properties. The potato cube run dried with initial atmospheric freeze-drying step had rehydration ability 430%above a run dried only above the freezing point. The average effective mass diffusivity for 5 mm slabs of leek was 0.5 x 10-11m2·s-1 for the sublimation stage and 2.2 x 10-11m2·s-1 for the evaporation stage.

关键词： physical properties dying food products sublimation evaporation

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A Preliminary Study of Yeats' Lyrics of sublimation

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英语广场（学术研究） 2012年第2期 9-12页

作者：刘智娟邓国清重庆理工大学

Yeats' lyrics of sublimation is one of his major concerns in his later years. sublimation for Yeats is essentially the transmutation and elevation of bitterness and tragic facts of being into happiness, into tranquility of mind, then into the emotionless emotion, as Yeats names it as "innocence". The process of sublimation enriches the creativity of Yeats as artist when he is confronted with severity of aging spiritually and physically.

关键词： Yeats Lyrics sublimation

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Moliere's sublimation of the Three Unities

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校园英语 2018年第22期 252-253页

作者：牛璟祎北京师范大学

The Three Unities is one of the most significant concept in western literary criticism, which has a lasting influence on the development of drama. In the Art of Poetry, Boileau synthetically explains the theory of Three Unities. However, many scholars didn’t approve of this, such as Moliere. In his comedy, Tartuffe, Moliere sublimated rules of the Three Unities, contributing to the creation of dramas all over the world.

关键词： the Three Unities Moliere sublimation Tartuffe

Continual Process of Self-Making： Hester Prynne＇s Life Is an Instance of sublimation

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Journal of Literature and Art Studies 2012年第4期2卷 471-475页

作者： U. H. Ruhina Jesmin Gono University Dhaka Bangladesh

This paper attempts to demonstrate Hester Prynne＇s, in Nathaniel Hawthorne＇s romantic work of fiction The Scarlet Letter （1994）, sublimation of her sexual impulses into identifying with the socially acceptable humanitarian actions, and societal demands in order to avoid the confrontation with the scorn of the people of Boston, her sexual urge, and with her weakness. Hester＇s libidinal energy was channeled into socially approved activities in her self-devoted years that made up her identity and reality. The scarlet letter ceased to be a stigma which once attracted the world＇s scorn and bitterness, later looked upon with reverence, and transformed into a thing to be sorrowed over. She had not ignored a large part of reality of her life （the past and present）. If she ignored her past she would entirely detach it from the present. She integrated her stigma into her life in the continual process of self-making, and thereby projecting herself into the future

关键词： adultery reality defense mechanism sublimation meaning