检索结果-南通市图书馆

Characteristics of shell thickness in a slab continuous casting mold

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2009年第1期16卷 25-31页

作者： Di-feng Wu Shu-sen cheng Zi-jian cheng School of Metallurgical and Ecological Engineering University of Science and Technology Beijing Beijing 100083 China Steelmaking Plant Jiuquan Iron and Steel Co. Ltd. Jiayuguan 735100 China

The key to reduce shell breakout in the continuous casting process is to control shell thickness in the mold. A numerical simulation on the turbulent flow and heat transfer coupled with solidification in the slab mold using the volume of fluid （VOF） model and the enthalpy-porosity scheme was conducted and the emphasis was put upon the flow effect on the shell thickness profiles in longitudinal and transverse directions. The results show that the jet acts a stronger impingement on the shell of narrow face, which causes a zero-increase of shell thickness in a certain range near the impingement point. The thinnest shell on the slab cross-section locates primarily in the center of the narrow face, and secondly near the comer of the wide face. Nozzle optimization can obviously increase the shell thickness and make it more uniform.

关键词： continuous casting slab mold shell thickness nozzle optimization

Recent Progress on COS-derived Polymers

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2019年第10期37卷 951-958,I0002页

作者： cheng-jian Zhang Xing-Hong Zhang Key Laboratory of Macromolecular Synthesis and Functionalization (Ministry of Education) Department of Polymer Science & Engineering Zhejiang University

The synthesis of sulfur-containing polymer, a very promising functional material, has made a great progress in the past several years. This review is focused on the very recent advances in poly(monothiocarbonate)s derived from carbonyl sulfide(COS) and epoxides including biomass-derived epoxides. Of significance, metal-free catalyst systems, including triethyl borane/Lewis base pair and thiourea/Lewis base pair are developed for the alternating copolymerization of COS with epoxides. Thereof, the thiourea/Lewis base pair is highly active to the copolymerization of COS with epoxide in a living manner. Moreover, a series of crystalline poly(monothiocarbonate)s are presented, including the copolymers derived from COS with oxetane, ethylene oxide, enantiopure epichlorohydrin, and achiral mesoepoxides via enantioselective copolymerization. Based on these COS/epoxide copolymerization process, a variety of COS-based block copolymers with well-defined structure are presented.

关键词： Carbonyl sulfide Epoxide Copolymerization Poly(monothiocarbonate)

Composite disturbance attenuation based saturated control for maintenance of low Earth orbit (LEO) formations

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science C(Computers and Electronics) 2012年第5期13卷 328-338页

作者： jian-cheng FAN Ke SUN National Key Laboratory of Inertial Technology Beihang University Beijing 100191 China Novel Inertial Instrument & Navigation System Technology Key Laboratory of Fundamental Science for National Defense Beihang University Beijing 100191 China

Maintenance of high performance formation control is important for low Earth orbit (LEO) formation missions of small *** this paper,a model of nonlinear relative motion dynamics is built,and then nonlinear and important perturbations affecting the formation configuration,such as J 2 and atmospheric drag,are analyzed as *** navigation satellite system based relative positioning with nonlinear filtering is adopted to provide state information associated with the *** combining disturbance observer based control with H ∞ state feedback,a composite disturbance attenuation controller is proposed for maintenance of continuous and accurate *** consideration of precise control relying on micro thrusters,a composite disturbance attenuation based saturated controller is designed and its stability is ***,through numerical simulations,we demonstrate that control accuracy is improved after effectively avoiding perturbations and that stabilization can be satisfied using this method.

关键词： Formation maintenance Perturbation Disturbance attenuation H ∞ state feedback Saturated control

Transcriptome analysis in the beet webworm, Spoladea recurvalis （Lepidoptera： Crambidae）

在线全文

学校读者我要写书评

暂无评论

Insect Science 2018年第1期25卷 33-44页

作者： jian-cheng Chang Srinivasan Ramasamy A VRDC - The World Vegetable Center Shanhua Tainan Taiwan China

The beet webworm, Spoladea recurvalis Fabricius, is a destructive pest on vegetable crops in tropics and subtropics; its main host plant is amaranth. It has become imperative to develop non-chemical methods to control S. recurvalis on amaranth. However, the lack of molecular information about this species has hindered the development of novel pest management strategies. In this study, high-throughput RNA sequencing covering de novo sequence assemblies, functional annotation of transcripts, gene function classification and enrichment was performed on S. recurvalis. Illumina sequencing generated a total of 120 435 transcript contigs ranging from 201 to 22 729 bases with a mean length of 688 bases. The assembled transcripts were subjected to Basic Local Alignment Search Tool- X （BLASTX） to obtain the annotations against non-redundant, Swiss-Prot, Clusters of Orthologous Groups （COG） and Kyoto Encyclopedia of Genes and Genomes （KEGG） protein databases. A subset of 58 225 transcript sequences returned hits from known proteins in the National Center for Biotechnology Information database, and the majority of the transcript sequences had the highest number of hits for Danausplexippus （50.43%）. A total of 1217 Gene Ontology-level 3 annotations were assigned to 51 805 transcripts, while 39 650 transcripts were predicted as functional protein-coding genes in the COG database and 20 037 transcripts were enriched to KEGG pathways. We identified 40 putative genes related to pheromone production and reception in S. recurvalis, with the expression of one gene between 0.29 and 1141.79 fragments per kilo base per million （FPKM） reads. The transcriptome sequence of S. recurvalis is a first step toward offering a comprehensive genomic resource which would enable better understanding of molecular mechanisms to enable development of effective pest management practices for this species.

关键词： pheromone protein-coding genes putative genes Spoladea recurvalis transcriptome

Hyperbolic structure and stickiness effect: A case of a 2D area-preserving twist mapping

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(Physics,Mechanics & Astronomy) 2014年第9期57卷 1737-1750页

作者： ZHOU LiYong LI jian cheng jian SUN YiSui School of Astronomy and Space Sciences Nanjing University Key Laboratory of Modern Astronomy and Astrophysics in Ministry of Education Nanjing University Department of Mathematics Nanjing University

The stickiness effect suffered by chaotic orbits diffusing in the phase space of a dynamical system is studied in this *** works have shown that the hyperbolic structures in the phase space play an essential role in causing the stickiness *** present in this paper the relationship between the stickiness effect and the geometric property of hyperbolic *** a two-dimensional area-preserving twist mapping as the model,we develop the numerical algorithms for computing the positions of the hyperbolic periodic orbits and for calculating the angle between the stable and unstable manifolds of the hyperbolic periodic *** show how the stickiness effect and the orbital diffusion speed are related to the angle.

关键词： stickiness effect hyperbolic structure stable and unstable manifolds

Characteristics of Deoxidation and Desulfurization during LF Refining Al-killed Steel by Highly Basic and Low Oxidizing Slag

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2014年第2期21卷 166-173页

作者： Jing GUO Shu-sen cheng Zi-jian cheng State Key Laboratory of Advanced Metallurgy School of Metallurgical and Ecological EngineeringUniversity of Science and Technology of Beijing Jiuquan Iron and Steel (Group) Co. Ltd.

Steel and slag samples were taken at the start and the end of LF refining for steel plate cold common （SPCC）, in the compact strip production （CSP） process, and at the same time, the temperature and oxygen activity a[o] were measured by using an oxygen sensor. Furthermore, inclusions in steel samples were monitored by scanning electron microscopy （SEM） combined with energy dispersive spectroscopy （EDS）. It was confirmed that a [o] in liq- uid steel was in equilibrium with inclusion rather than with top slag during LF refining. Desulfurization was related to deoxidation since a[o] at slag-steel interface was clarified to be very close to that in liquid steel under the specific con- dition in LF with intense stirring by argon blowing and refined by highly basic low oxidizing slag for Al-killed steel. Sulfur partition ratio （Ls） was very sensitive to a[o]. Since a[o] increased rapidly with temperature rise, it not only offset promotion to desulfurization reaction with temperature rise but decreased Ls. For Al-killed steel, ***- tion of Al2O3 for lowering the activity of Al2O3 in inclusion was believed to be favorable for both deoxidation and desulfurization during LF refining.

关键词： deoxidation desulfurization inclusion sulfur partition ratio LF refining

The Origin of The Soft X-Ray Excess in the Seyfert 1.5 Galaxy ESO 362-G18

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2022年第3期22卷 10-32页

作者： Xiao-Gu Zhong jian-cheng Wang Yunnan Observatories Chinese Academy of SciencesKunming 650216China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China University of Chinese Academy of Sciences Beijing 100049China

We review the Seyfert 1.5 Galaxy ESO 362-G18 for exploring the origin of the soft X-ray *** Warm Corona and Relativistic Reflection models are two main scenarios to interpret the soft X-ray excess in active galactic nuclei at *** use the simultaneous X-ray observation data of XMM-Newton and Nu STAR on2016 September 24 to perform spectral analysis in two ***,we analyze the time-average spectra by using Warm Corona and Relativistic Reflection ***,we also explore the Hybrid model,Double Reflection model and Double Warm Corona *** find that both the Warm Corona and Relativistic Reflection models can interpret the time-average spectra well but cannot be distinguished easily based on the time-averaged spectra fit ***,we add the rms and covariance spectra to perform the spectral analysis with time-average *** result shows that the warm corona could reproduce all of these spectra *** hot,optical thin corona and neutral distant reflection will increase their contribution with the temporal frequency,meaning that the corona responsible for X-ray continuum comes from the inner compact X-ray region and the neutral distant reflection is made of some moderate scale neutral clumps.

关键词： galaxies:active galaxies:individual(ESO 362-G18) galaxies:Seyfert

Organocatalytic polymerization

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 2019年第9期62卷 1087-1089页

作者： cheng-jian Zhang Xing-Hong Zhang Key Laboratory of Macromolecular Synthesis and Functionalization (Ministry of Education) Department of Polymer Science and EngineeringZhejiang University

Organocatalysis, defined as the use of small organic molecules for catalyzing chemical transformations, can be traced back more than a century and has become a thriving area over the past 20 years.

关键词： Organocatalytic polymerization organic molecules catalyzing chemical transformations

Lie transformation on shortcut to adiabaticity in parametric driving quantum systems

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2021年第6期30卷 111-115页

作者： jian-jian cheng Yao Du Lin Zhang School of Physics and Information Technology Shaanxi Normal UniversityXi'an 710119China

Shortcut to adiabaticity(STA) is a speedway to produce the same final state that would result in an adiabatic, infinitely slow process. Two typical techniques to engineer STA are developed by either introducing auxiliary counterdiabatic fields or finding new Hamiltonians that own dynamical invariants to constraint the system into the adiabatic paths. In this paper,an efficient method is introduced to naturally cover the above two techniques with a unified Lie algebraic framework and neatly remove the design difficulties and loose assumptions in the two techniques. A general STA scheme for different potential expansions concisely achieves with the aid of squeezing transformations.

关键词： shortcut to adiabaticity parametric driving Lewis–Riesenfeld invariants