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Development of a seven-cell S-band standing-wave RF-deflecting cavity for Tsinghua Thomson scattering X-ray source

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Nuclear Science and Techniques 2021年第4期32卷 20-29页

作者： Xian-Cai Lin Hao Zha Jia-Ru Shi Liu-Yuan Zhou Shuang Liu Jian Gao Huai-Bi Chen department of engineering Physics Tsinghua UniversityBeijing 100084China Key Laboratory of Particle and Radiation Imaging(Tsinghua University) Ministry of EducationBeijing 100084China

A 2856-MHz,π-mode,seven-cell standingwave deflecting cavity was designed and fabricated for bunch length measurement in Tsinghua Thomson scattering X-ray source(TTX)*** cavity was installed in the TTX and provided a deflecting voltage of 4.2 Mv with an input power of 2.5 *** length diagnoses of electron beams with energies up to 39 Mev have been *** this article,the RF design of the cavity using HFSS,fabrication,and RF test processes are ***-power operation with accelerated beams and calibration of the deflecting voltage are also presented.

关键词： Deflecting RF cavity Standing wave Bunchlength measurement Thomson X-ray source

A Three-dimensional Organic-inorganic Hybrid Material Supported by Decavanadate Clusters and Na-O Chains: Synthesis and Crystal Structure of [Na_6(H_2O)_(16)(dod)_4v_(10)O_(28)]

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Chinese Journal of Structural Chemistry 2004年第4期23卷 407-412页

作者：张献明武海顺陈小明 department of Chemistry Shanxi Normal UniversityLinfenShanxi 041004China School of Chemistry and Chemical engineering Sun Yat-Sen UniversityGuangzhou 510275China

A new organic-inorganic hybrid material [Na6(H2O)16(dod)2v10O28] (dod = 1,4- diazoniabicyclo[2,2,2]octane-1,4-diacetate) has been synthesized and X-ray single-crystal structural analysis reveals it crystallizes in triclinic, space group P with a = 11.533(7), b = 12.031(7), c = 12.187(4) ? a = 72.47(1), b = 73.16(1), g = 68.21(1)o, C20H64N4Na6O52v10, v = 1467(1) ?, Z = 1, Mr = 1840.1, Dc = 2.083 g/cm3, MoKa, l = 0.71073 ? m = 1.686, F(000) = 924, S = 1.027, the final R = 0.0538 and wR = 0.1272 for 4398 observed reflections. The compound has a three-dimensional frame- work constructed from decavanadate clusters, NaO chains and dod ligands. A variety of OH…O and CH…O hydrogen bonds play an important role in stabilizing the framework.

关键词： organic-inorganic hybrid decavanadate Na-O chain hydrogen bond

Stress corrosion cracking behaviour of 7xxx aluminum alloys: A literature review

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Transactions of Nonferrous Metals Society of China 2016年第6期26卷 1447-1471页

作者： A.C.UMAMAHESHWER RAO v.vASU M.GOvINDARAJU K.v.SAI SRINADH department of Mechanical engineering National Institute of Technology WarangalWarangal 506004India Nonferrous Materials Technology Development Centre Hyderabad-500058500005India

Stress corrosion cracking （SCC） is degradation of mechanical properties under the combined action of stress and corrosive environment of the susceptible material. Out of eight series of aluminium alloys, 2xxx, 5xxx and 7xxx aluminium alloys are susceptible to SCC. Among them, 7xxx series aluminium alloys have specific application in aerospace, military and structural industries due to superior mechanical properties. In these high strength 7xxx aluminium alloys, SCC plays a vital factor of consideration, as these failures are catastrophic during the service. The understanding of SCC behaviour possesses critical challenge for this alloy. The main aim of this review paper is to understand the effect of constituent alloying elements on the response of microstructural variation in various heat-treated conditions on SCC behavior. Further, review was made for improving the SCC resistance using thermomechanical treatments and by surface modifications of 7xxx alloys. Apart from a brief review on SCC of 7xxx alloys, this paper presents the effect of stress and pre-strain, effect of constituent alloying elements in the alloy, and the effect of environments on SCC behaviour. In addition, the SCC behaviours of weldments, 7xxx metal matrix composites and also laser surface modifications were also reviewed.

关键词： 7xxx aluminum alloy stress corrosion cracking heat treatment microstructure corrosive environment thermomechanical treatment

Reaction between Ti–6Al–4v and Y_2O_3–SiO_2 based face shell for investment casting

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Rare Metals 2016年第12期35卷 901-908页

作者： Ya-Meng Wei Zhi-Gang Lu Guang-Peng Wu Xing-Quan Long department of Mechanical engineering Tsinghua University State Key Laboratory of Tribology Tsinghua University Guizhou Anji Aviation Investment Casting Co. Ltd.

The pH value and viscosity of Y2O3-SiO2 （Y-Si） slurry made by Y2O3 powders and silica sol for the face coat of Ti-6Al-4v investment casting were measured. The thermal behavior of the shell made by the Y-Si face coat system was investigated by differential scanning calorimeter （DSC）, thermal gravimetric （TG） analysis combined with mass spectrometry （MS）, and the phase transformations were determined by X-ray diffraction （XRD）. Hot strength, residual strength, linear expansion coefficient, and wearing resistance performance of the shell were also tested. The microstructure and elements distri- bution of the interaction layer were studied by scanning electron microscope （SEM） and energy-dispersive spectrometer （EDS）, respectively. The microhardness tester was applied for the microhardness. The results showed that the slurry was stable for at least 60 h. A very small amount of YZrO3 was formed below 1050℃ and Y2SiO5 was formed around 1450℃. The shell made by Y-Si system had good mechanical property which could reduce cracks during the procedure of dewaxing and inclusions during pouring. Some Al volatilized from the melt, permeated the surface of the face coat shell, and formed the black reaction layer, which blocked the permeation of O so that O penetration was limited to 5μm. The depth of Si penetration was about 60 μm. The hard layer was also around 60 μm.

关键词： Investment casting Titanium alloy Silica sol Yttrium oxide Interface reaction

Synthesis, Crystal Structure and Thermal Behavior of GZTO·H2O

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Chinese Journal of Chemistry 2011年第8期29卷 1672-1676页

作者：钟益堂黄洁宋纪蓉徐抗震赵丹王立勤张新瑜 department of Chemical engineering/Shaanxi Key Laboratory of Physico-lnorganic Chemistry Northwest University Xi'an Shaanxi 710069 China Conservation Technology department the Palace Museum BeOing 100009 China

Guanidimium-4,4-azo-l-hydro-1,2,4-triazol-5-one （GZTO·H2O） was synthesized from 4-amino-1,2,4-triazol- 5-one as a starting material by two-step including oxidation coupling using acid KMnO4 and reaction with （NH2）2C=NHoHNO3 （GN） in KOH solution. The single crystal of the title compound was obtained by slow evapo- ration method at room temperature, and its structure was firstly determined with X-ray single-crystal diffractometer. It is a orthorhombic crystal, space group Pbca with cell dimensions of a = 1.0459（2） nm, b =- 1.3584（3） nm, c= 1.6103（3） nm, a= 90.00（10）°, β=90.00（11）°,γ=90.00（11）°, v=2.2878（8） nm3, Z=8, De= 1.587 gocm-3, F（000） = 1136,/l = 0.132 mm- 1, R1 = 0.0455, wR2 = 0. 1397. The thermal behavior of GZTO·H2O was studied under a non-isothermal condition by DSC-TGA method, and its thermal decomposition process can be divided into three stages, and the first stage is an intense exothermic decomposition process. The second stage and the third stage are slow exothermic decomposition processes. The critical temperature of thermal explosion is 237.74℃.

关键词： X-ray diffraction high-nitrogen energetic materials 4-amino-1,2,4-triazol-5-one (ATO) crystal struc-ture azo-compound thermochemistry

Utilizing the dropped packets for data delivery in vANETs

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The Journal of China Universities of Posts and Telecommunications 2013年第3期20卷 48-52页

作者： SONG Chao LIU Ming GONG Hai-gang CHEN Gui-hai CAO Jian-nong School of Computer Science and engineering University of Electronic Science and Technology of China School of Computer Science and engineering Shanghai Jiao Tong University Internet and Mobile Computing Laboratory Department of Computing Hong Kong Polytechnic University

Timely and cost-efficient multi-hop data delivery among vehicles is essential for vehicular ad-hoc networks （vANETs）, and various routing protocols are envisioned for infrastructure-less vehicle-to-vehicle （v2v） communications. Generally, when a packet （or a duplicate） is delivered out of the routing path, it will be dropped. However, we observe that these packets （or duplicates） may also be delivered much faster than the packets delivered along the original routing path. In this paper, we propose a novel tree based routing scheme （TBRS） for ultilizing the dropped packets in vANETs. In TBRS, the packet is delivered along a routing tree with the destination as its root. And when the packet is delivered out its routing tree, it won＇t be dropt immediately and will be delivered for a while if it can arrive at another branch of the tree. We conduct the extensive simulations to evaluate the performance of TBRS based on the road map of a real city collected from Google Earth. The simulation results show that TBRS can outperform the existing protocols, especially when the network resources are limited.

关键词： routing vanet opportunistic forwarding

Nanoscale deformation of multiaxially forged ultrafine-grained Mg-2Zn-2Gd alloy with high strength-high ductility combination and comparison with the coarse-grained counterpart

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Journal of Materials Science & Technology 2018年第2期34卷 311-316页

作者： K. Li v.S.Y.Injeti P. Trivedi L.E. Murr R.D.K. Misra department of Metallurgical Materials and Biomedical Engineering University of Texas at El Paso 500 W. University Avenue El Paso TX 79968-0521 USA

Cold processing of magnesium （Mg） alloys is a challenge because Mg has a hexagonal close-packed （HCP） lattice with limited slip systems, which makes it difficult to plastically deform at low temperature. To address this challenge, a combination of annealing of as-cast alloy and multi-axial forging was adopted ro obtain isotropic ultrafine-grained （UFG） structure in a lean Mg-2Zn-2Gd alloy with high strength （yield strength： ~227 MPa）-high ductility （% elongation：～30%） combination. This combination of strength and ductility is excellent for the lean alloy, enabling an understanding of deformation processes in a formable high strength Mg-rare earth alloy. The nanoscale deformation behavior was studied via nanoindentation and electron microscopy, and the behavior was compared with its low strength （yield strength：～46 MPa） - low ductility （% elongation：～7%） coarse-grained （CG） counterpart. In the UFG alloy, extensive dislocation slip was an active deformation mechanism, while in the CG alloy, mechanical twinning occurred. The differences in the deformation mechanisms of UFG and CG alloys were reflected in the discrete burst in the load-displacement plots. The deformation of Mg-2Zn-2Gd alloys was significantly influenced by the grain structure, such that there was change in the deformation mechanism from dislocation slip （non-basal slip） to nanoscale twins in the CG structure. The high plasticity ofUFG Mg alloy involved high dislocation activity and change in activation volume.

关键词： Magnesium alloy Ultrafine-grained Nanoscale deformation

Anisotropic iron-doping patterns in two-dimensional cobalt oxide nanoislands on Au(111)

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Nano Research 2019年第9期12卷 2364-2372页

作者： Anthony Curto Zhaozong Sun Jonathan Rodriguez-Fernandez Liang Zhang Ayush Parikh Ting Tan Jeppe v. Lauritsen Aleksandra vojvodic department of Chemical and Biomolecular engineering University of PennsylvaniaPhiladelphiaPA 19104USA Interdisciplinary Nanoscience Center (iNANO) Aarhus University8000 Aarhus CDenmark

An in teg rated approach combi ning den sity functional theory(DFT)calculati ons and atomic resol utio n sea nning tun neling microscopy(STM)is used to study well-defined iron-doped cobalt oxide nanoislands supported on Au(111).The focus is on the structure and distribution of Fe dopants within these nanoislands of CoO as a function of Fe to Co *** DFT and STM results agree strongly and complement each other to allow for a more complete un dersta nding of the dopa nt structure trends on the nano *** Fe as a marker,we first find that the stacki ng seque nee of the moire structure of the host cobalt oxide nano islands can be ide ntified un ambiguously through a combinati on of DFT and *** the distinct con trast of the embedded Fe dopa nt atoms as observed with atom-resolved STM,we find correlatio ns betwee n Fe dopa nt positi on and the CoO/Au(111)moire patter n at varyi ng Fe dopa nt den *** n of Fe-dopa nt clusters within the nano islands is investigated in detail through DFT and found to agree with the dopant patter ns observed in *** find that the structural effects of Fe dopants throughout the nanoislands with the basal planes and the two types of edges—the oxygen and metal edges—have different *** DFT calculations and STM images show a strong preferenee for Fe dopants to be located directly on or near the oxygen edge of the nanoislands as opposed to being directly on or n ear the metal *** n together,our results illustrate that Fe dopa nt incorporati on and distributi on within CoO nanoislands are highly an isotropic and gover ned by both the moire structure of the basal planes as well as nano-size effects present at the under-coordinated edges of different local geometry and chemistries.

关键词： seanning tunneling microscopy(STM) density functional theory(DFT) cobalt oxide transition metal oxides mixed transition metal oxides

Fabrication and characterization of a GaN/(4H)SiC vertical pn power diode using direct and interfaced epitaxial-growth approaches

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Journal of Semiconductors 2013年第4期34卷 20-23页

作者： Bose Srikanta Mazumder S K Laboratory for Energy and Switching-Electronics Systems Department of Electrical and Computer EngineeringUniversity of Illinois at ChicagoChicagoIL:60607USA

We report the fabrication and characterization of a vertical pn power diode which is realized using two separate epitaxial-growth mechanisms：（a） p-GaN over p-（4H）SiC, and （b） p-GaN over n-（4H）SiC with A1N as the interface layer. In all of the cases, n＋-doped （4H）SiC serves as the cathode substrate. Pd（200 A）/Au（10000 A） is used for the anode contact while Ni（1000A） is used for the bottom cathode contact. The measured forward drop of the pn diode with A1N as the interface material is found to be around 5.1 v; whereas, it is 3 v for the other sample structure. The measured reverse-blocking voltage is found to be greater than 200 v.

关键词： GaN (4H)SiC vertical pn power diode power electronics