检索结果-南通市图书馆

Kinetics and mechanism of the low-energy b-a phase transition of the second kind in 2,4-dinitroanisole

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2024年第10期40卷 210-224页

作者： aleksandr V.Stankevich Nikolay A.Rasputin Anisa KhRudina Gennady L.Rusinov Vera I.Filyakova Valery N.Charushin y1.postovsky institute of organic synthesis ural branch of the russian academy of sciencesekaterinburg 620108russia russian federal nuclear center e zababakhin all-russia research institute of technical physics snezhinsk 456770russia kazan national research technological university kazan 420015russia

In this work,comprehensive studies of 2,4-dinitroanisole(2,4DNAN)were carried out using powder thermorentgenography of the internal *** time of the complete polymorphic transition in the solid phase b/a in 2,4DNAN under various combinations of conditions has been *** has been established that,regardless of the season of manufacture of the substance,when it is stored for 8e9 months,with a change in ambient temperature from minus 30℃ to plus 30℃,a complete polymorphic transition b/a *** stored in conditions below minus 5℃,polymorphic transition does not *** stored in conditions above plus 30℃ in a closed container,polymorphic transition occurs within 3 *** polymorphic transition is accompanied by a decrease in density by 1.3%e1.5%and an increase in melting temperature by 10-12℃,depending on the degree of purity of the starting *** activation energy of the molecular rearrangement was 68e70 kJ/mol(16.5±3 kcal/mol).The mechanism of polymorphic transition has been evaluated,which is presumably based on internal homodiffusion and energy transfer to the surface of the mass of powder particles and the *** average activation energy of the polymorphic transition process was 110±6.2 kJ/mol(26.2 kcal/mol).In an open container,reactions proceed by a homogeneous mechanism,and in a closed container by a heterogeneous mechanism involving the gas phase.

关键词： energetic materials Melt-castable 2,4-Dinitroanisole Polymorphic transition Kinetics Mechanism Homodiffusion Sublimation

Impact of doping profiles on the formation of laser-active centers in bismuth-doped GeO_(2)–SiO_(2)glass fibers

在线全文

学校读者我要写书评

暂无评论

Photonics Research 2024年第2期12卷 260-270页

作者： SeRGeY ALYSHeV ALeXANDeR VAKHRUSHeV aleksandr KHeGAI eLeNA FIRSTOVA KONSTANTIN RIUMKIN MIKHAIL MeLKUMOV LYUDMILA ISKHAKOVA ANDReY UMNIKOV SeRGeI FIRSTOV Prokhorov General Physics Institute of the Russian Academy of Sciences Dianov Fiber Optics Research Center119333 MoscowRussia Devyatykh Institute of Chemistry of High-Purity Substances of the Russian Academy of Sciences 603951 Nizhny NovgorodRussia

Multi-wavelength-band transmission technology based on the exploitation of the extended spectral region is considered as a potential approach to increase the transmission capacity in the deployed fiber-optic communication *** development of optical amplifiers operating in the O-,e-,S-,and U-telecom bands is an extremely important challenge for the successful implementation of this ***-doped fibers are of increasing interest as gain materials,which can be used to provide broadband amplification in the mentioned telecom *** is due to the ability of Bi ions incorporated into glass network to form bismuth active centers(BACs)with specific optical properties,which are primarily determined by the glass *** this work,the impact of the doping profiles of both Ge atoms as glass modifiers and Bi ions on the BACs formation is studied using a series of bismuth-doped fibers fabricated by the modified chemical vapor deposition(MCVD)*** Bi-to-BACs conversion efficiency in various spatial regions of the studied samples is *** is turned out that for high-Bi concentration regions,the conversion efficiency is very low(less than 10%).In addition,the relationship of the conversion efficiency to the distribution of Bi ions and/or Ge atoms is ***,a continuous-wave laser at 1.46μm with a record slope efficiency of 80%is demonstrated using a Bi-doped fiber with confined doping profile,where the Bi-to-BACs conversion efficiency is 35%.This paper provides new information which might help to facilitate understanding of the features of Bi-doped fibers and their potentially achievable characteristics.

关键词： fiber fibers bismuth

Pulsed THz radiation under ultrafast optical discharge of vacuum photodiode

在线全文

学校读者我要写书评

暂无评论

Frontiers of Optoelectronics 2024年第2期 100-113页

作者： aleksandr A.Ushakov Kseniia A.Mamaeva Leonid V.Seleznev Georgy e.Rizaev Vladimir Bukin Timophey V.Dolmatov Pavel A.Chizhov Vladimir Bagdasarov Sergey V.Garnov Prokhorov General Physics Institute of the Russian Academy of Sciences Physical Institute Russian Academy of Sciences Moscow Institute of Physics and Technology Russian Institute for Scientific and Technical Information

In this paper, we first present an experimental demonstration of terahertz radiation pulse generation with energy up to 5 pJ under the electron emission during ultrafast optical discharge of a vacuum photodiode. We use a femtosecond optical excitation of metallic copper photocathode for the generation of ultrashort electron bunch and up to 45 kV/cm external electric field for the photo-emitted electron acceleration. Measurements of terahertz pulses energy as a function of emitted charge density, incidence angle of optical radiation and applied electric field have been provided. Spectral and polarization characteristics of generated terahertz pulses have also been studied. The proposed semi-analytical model and simulations in COMSOL Multiphysics prove the experimental data and allow for the optimization of experimental conditions aimed at flexible control of radiation parameters.

关键词：

Variable retention forestry in european boreal forests in Russia

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

ecological Processes 2019年第1期8卷 424-434页

作者： ekaterina Shorohova Sergey Sinkevich aleksandr Kryshen Ilkka Vanha-Majamaa Forest Research Institute of the Karelian Research Centre of the Russian Academy of Sciences Pushkinskaya str.11Petrozavodsk 185910Russia Saint-Petersburg State Forest Technical University Institutsky str.5Saint Petersburg 194021Russia Natural Resources Institute Finland(Luke)Latokartanonkaari 9FI-00790 HelsinkiFinland

We explored whether,and to what extent,variable retention(VR)forestry has been applied in european boreal forests in northwestern *** survey revealed VR since *** 1910 and the 1960s,the statistics showing how much was retained are largely ***,for example,in the 1950s,on a large scale in the Republic of Karelia,up to 200-ha-sized harvesting areas,18–33%,were retention patches with a mean growing stock of 30–40m3 ha−*** the fellings defined as“incomplete clear fellings,”which were the most common final felling type at that time,11–40%of the growing stock was *** the 1960s and the early 1990s,with more efficient harvesting and skidding techniques,conventional clear fellings with a much lower amount of retention were *** about the regeneration of harvested areas gradually led to smaller(maximum 50 ha)harvesting areas and the increase of silvicultural *** now,to ensure natural regeneration,patches of understory and 20–25 seed trees(i.e.,ca.15–25m3)per ha have been left permanently in harvesting ***-scale retention for protecting ecosystem functions and biodiversity was legislated in 1978 by preserving key biotopes up to 1000 ha in *** 2001,promoted by forest certification,the key biotopes,such as paludified forest patches,buffers around water bodies,and habitats of red-listed species,have also been retained in harvesting areas,together with a dispersed retention of different *** estimates of the amount of key biotopes are largely ***,estimates of 1–13%in harvesting areas and 23%in whole managed landscapes have been *** applied during the last century has emulated natural disturbances and created diverse uneven-aged forest structures with high amounts of diverse coarse woody *** conclude that an analysis of past and current retention practices is essential for estimating the global role of Russian *** decisions on the general direction

关键词： Biological legacies Nature conservation Biodiversity Clear felling Key biotopes Coarse woody debris,Silviculture Dispersed and aggregated retention

energy efficiencies and CO_(2)emissions associated with lowtemperature separation technologies for the processing of formation fluid from the Achimov deposits

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Petroleum Research 2023年第3期8卷 413-423页

作者： Alexandra Saitova Sergey Strokin Falk Ahnert aleksandr Chepurnov Peter the Great St Petersburg Polytechnic University Politechnicheskaya str.29Saint Petersburg195251Russian Federation Wintershall Dea AG Friedrich-Ebert-Straße 160Kassel34119Germany Wintershall Dea Russia GmbH Reshetnikova str.14ASaint Petersburg196105Russian Federation

Three different technologies for the low-temperature separation(LTS)of gas condensate from the Achimov deposits in the Russian Urengoyskoe gas and condensate field were assessed using exergy *** options examined included turbo-expansion and *** exergy values were calculated for material streams and exergy losses and efficiencies were estimated for dedicated equipment used in the *** lowest exergy loss of 4221.2 kW was obtained using turboexpansion and electricity *** carbon release associated with each scenario was calculated while considering different production rates,technological parameters and natural decreases in wellhead *** integral carbon footprint after 40 years of LTS operation was estimated for all cases.A classical ejector-based LTS scheme was shown to produce 1200 t of CO_(2)emissions over 40 years of *** same scheme combined with a turboexpander and electricity generator produced 59%less CO_(2)in the same *** expansion-cogeneration LTS scheme was found to be the most effective and ecologically friendly among the various options based on this analysis.

关键词： Oil and gas field Gas condensate Carbon emission Carbon footprint Complex gas treatment unit

Methodologies for preparation of prokaryotic extracts for cell-free expression systems

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Synthetic and Systems Biotechnology 2020年第4期5卷 252-267页

作者： Stephanie D.Cole aleksandr e.Miklos Abel C.Chiao Zachary Z.Sun Matthew W.Lux US Army Combat Capabilities Development Command Chemical Biological Center 8567 Ricketts Point RoadAberdeen Proving GroundMD21010USA Division of Biology and Biological engineering California Institute of TechnologyPasadenaCAUSA Synvitrobio Inc. San FranciscoCAUSA 8567 Ricketts Point Road Bldg E3549 Room B140APGMD21010USA

Cell-free systems that mimic essential cell functions,such as gene expression,have dramatically expanded in recent years,both in terms of applications and widespread *** we provide a review of cell-extract methods,with a specific focus on prokaryotic ***,we describe the diversity of escherichia coli genetic strains available and their corresponding *** then trace the history of cell-extract methodology over the past 20 years,showing key improvements that lower the entry level for new ***,we survey the rise of new prokaryotic cell-free systems,with associated methods,and the opportunities ***,we use this historical perspective to comment on the role of methodology improvements and highlight where further improvements may be possible.

关键词： Cell-free systems Cell-free expression Cell-free extract Synthetic biology Methods

Negative thermal expansion in one-dimension of a new double sulfate AgHo(SO_(4))_(2)with isolated SO_4 tetrahedra

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2021年第17期76卷 111-121页

作者： Yuriy G.Denisenko Victor V.Atuchin Maxim S.Molokeev Naizheng Wang Xingxing Jiang aleksandr S.aleksandrovsky Alexander S.Krylov aleksandr S.Oreshonkov Alexander e.Sedykh Svetlana S.Volkova Zheshuai Lin Oleg V.Andreev Klaus Müller-Buschbaum Institute of Chemistry Tyumen State University.Tyumen625003Russia Institute of Inorganic and Analytical Chemistry Justus-Liebig-University of Giessen35392Giessen.Germany Department of General and Special Chemistry Industrial University of TyumenTyumen625000Russia Laboratory of Optical Materials and Structures Institute of Semiconductor PhysicsSB RASNovosibirsk630090Russia Laboratory of Semiconductor and Dielectric Materials Novosibirsk State UniversityNovosibirsk630090Russia Research and Development Department.Kemerovo State University Kemerovo650000Russia Laboratory of Crystal Physics Kirensky Institute of PhysicsFederal Research Center KSC SB RASKrasnoyarsk660036Russia Siberian Federal University Krasnoyarsk660041Russia Department of Physics Far Eastern State Transport UniversityKhabarovsk680021Russia Technical Institute of Physics and Chemistry Chinese Academy of SciencesBeijing100190China Laboratory of Coherent Optics Kirensky Institute of Physics.Federal Research Center KSC SB RASKrasnoyarsk660036Russia Institute of Nanotechnology Spectroscopy and Quantum ChemistrySiberian Federal UniversityKrasnoyarsk660041Russia Laboratory of Molecular Spectroscopy Kirensky Institute of PhysicsFederal Research Center KSC SB RASKrasnoyarsk660036Russia Center for Materials Research(LaMa) Justus-Liebig-University GiessenGiessen35392Germany University of the Chinese Academy of Sciences Beijing100049China Laboratory of the Chemistry of Rare earth Compounds Institute of Solid State ChemistryUB RASEkaterinburg620137Russia

A double holmium-silver sulfate was obtained for the first *** temperature intervals for the formation and stability of the compound were determined by differential scanning *** crystal structure of AgHo(SO_(4))_(2)was determined by Rietveld *** X-ray diffraction(XRD)analysis showed that the compound crystallizes in the monoclinic syngony,space group P2_1/m,with the unit cell parameters a=4.71751(4)A,b=6.84940(6)A and c=9.89528(9)A,β=95.1466(4)·,V=318.448(5)A^(3),Z=2,R_B=1.55%,T=303 *** types of sulfate tetrahedra were found in the structure,which significantly affected the spectral properties in the infrared *** the temperature range of 143-703 K,a negative thermal expansion along the b direction accompanied by a positive thermal expansion along the a and c directions was *** was established that negative thermal expansion is the result of the deformation of sulfate tetrahedra,which is affected by the movement of holmium and silver *** excitation in the blue spectral range(457.9 nm)produces a luminescence in light blue(489 nm),green(545 nm)and red(654 nm)spectral ranges,and the latter two were of comparable intensity that is favorable for WLeD *** observed luminescent band distribution is ascribed to the specific crystal field at Ho^(3+)ion sites rather than a variation of radiationless probability.

关键词： Sulfate Crystal structure Thermal expansion Raman Photoluminescence Band structure

Size-dependent structural and magnetic properties of chemically synthesized Co-Ni-Ga nanoparticles

在线全文

学校读者我要写书评

暂无评论

Nano Research 2017年第10期10卷 3421-3433页

作者： Changhai Wang aleksandr A. Levin Julie Karel Simone Fabbrici Jinfeng Qian Carlos e. ViolBarbosa Siham Ouardi Franca Albertini Walter Schnelle Jan Rohlicek Gerhard H. Fecher Claudia Felser Max Planck Institute for Chemical Physics of Solids D-01187 Dresden Germany Institute of Materials for electronics and Magnetism IMEM-CNRI-43124 Parma Italy MIST e-R Laboratory Via Gobetti 101 I-40129 Bologna Italy

Phase transitions and magnetic properties of shape-memory materials can be tailored by tuning the size of the constituent materials, such as nanoparticles. However, owing to the lack of suitable synthetic methods for size-controlled Heusler nanoparticles, there is no report on the size dependence of their properties and functionalities. In this contribution, we present the first chemical synthesis of size-selected Co-Ni-Ga Heusler nanoparticles. We also report the structure and magnetic properties of the biphasic Co-Ni-Ga nanoparticles with sizes in the range of 30-84 nm, prepared by a SBA-15 nanoporous silica- templated approach. The particle sizes could be readily tuned by controlling the loading and concentration of the precursors. The fractions and crystallite sizes of each phase of the Co-Ni-Ga nanoparticles are closely related to their particle size. enhanced magnetization and decreased coercivity are observed with increasing particle size. The Curie temperature （To） of the Co-Ni-Ga nanoparticles also depends on their size. The 84 nm-sized particles exhibit the highest Tc （≈ 1,174 K） among all known Heusler compounds. The very high Curie temperatures of the Co-Ni-Ga nanoparticles render them promising candidates for application in high-temperature shape memory alloy-based devices.

关键词： Co-Ni-Ga nanoparticles chemical synthesis size magnetic properties

Carbon–Iron Microfibrous Material Produced by Thermal Treatment of Self-rolled Poly(4-vinyl pyridine) Films Loaded by Fe_2O_3 Particles

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2015年第9期31卷 881-887页

作者： Camelia Matei Ghimbeu aleksandr I.egunov Andrey S.Ryzhikov Valeriy A.Luchnikov Institut de Science des Matériaux de Mulhouse

ensembles of freeze-dried self-rolled polymer micro-scrolls are explored as template media for produc- ing carbon-iron based composites with fibrous morphology. Polymer fibres impregnated with furfuryl alcohol and loaded with Fe2O3 particles, were thermally treated under inert atmosphere at 700 ℃ and subsequently analysed by scanning and transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, and nitrogen adsorption. The resulting material has a micro-fibrous mor- phology and is basically composed of metallic Fe^0 and FeO particles, i.e., more than 98 wt% of the carbon/ iron-based composite mass. These particles are held together by amorphous porous carbon foam obtained by in-situ carbonization of the polymer/Fe2O3 composite with evacuation of carbon from the system via COx gases released by carbo-reduction of Fe2O3. The material has significant activity in the reaction of catalytic decomposition of hydrogen peroxide in water solutions.

关键词： Composite materialsPorous carbonPolymersIron particles