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Effect of Free-cutting Additives on Machining Characteristics of Austenitic Stainless Steels

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Journal of Materials Science & Technology 2010年第9期26卷 839-844页

作者： Zhuang Li di Wu School of Materials Science and Engineering Shenyang University of Aeronautics and Astronautics Shenyang 110136 China State Key Laboratory of Rolling and Automation Northeastern University Shenyang 110004 China

The machinability tests were conducted by using a YD-21 dynamometer on a CA6161A *** experiments were conducted to determine the effect of free-cutting additives on machining characteristics of austenitic stainless *** conventional austenitic stainless steel 1Cr18Ni9Ti（steel A） and the free cutting austenitic stainless steel（steel B） were *** results have shown that machinable inclusions were composed of MnS and CuO,and they might be also *** presence of Bi in the inclusion was detected by the atom map and electro-probe microanalysis（EPMA）,which might be one of the most important factors to improve the machinability of austenitic stainless *** cutting forces for steel B were lower than those of steel A at various cutting speeds;the abrasion depth of the flank of the tool for steel B was less than that of the steel A under the same cutting *** machinability of austenitic stainless steel was visibly improved by adding free-cutting additives,such as S,Cu and *** tensile,yield strength,and total elongation values of the free cutting austenitic stainless steel were improved due to the addition of these free-cutting additives.

关键词： Austenitic stainless steel Free-cutting additives Bismuth Machining characteristics Mechanical properties

Research on the Performance of Supercritical CO_2 Dry Gas Seal with different Deep Spiral Groove

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Journal of Thermal Science 2019年第3期28卷 547-558页

作者： DU Qiuwan ZHANG di MOE Key Laboratory of Thermo-Fluid Science and Engineering Xi'an Jiaotong University

The performance of supercritical CO_2(SCO_2) dry gas seal(DGS) with different deep spiral groove is investigated with the thermal-fluid-solid coupling method. The performance parameters of DGSs with five different kinds of grooves are obtained. The influence of inlet temperature, inlet pressure, velocity and film thickness on performance is analyzed compared with air DGS. The average film pressure, open force and leakage decrease while the average face temperature and flow velocity increase as the spiral groove number increases. The average film pressure, average face temperature, open force and leakage of DGS with radial different deep groove are higher than those of DGS with circumferential different deep groove respectively under the same spiral groove number while the average flow velocity is the opposite. SCO_2 DGS can generate larger average film pressure, open force and leakage with lower average face temperature than air DGS. SCO_2 DGS could maintain better sealing performance despite larger leakage with the variations of inlet temperature, inlet pressure, velocity and film thickness. The variables hold a more remarkable influence on SCO_2 DGS compared with air DGS.

关键词： supercritical carbon dioxide different deep spiral groove dry gas seal thermal-fluid-solid coupling method

Regioselectivity Study on Propylene Polymerization Catalyzed by Neutral Salicyladiminato Pd(ii) Model Complex with DFT Method

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Chinese Journal of Structural Chemistry 2005年第6期24卷 723-728页

作者： YANGZhao-di LiUYue LiUYing ChemicalandEnvironmentalEngineeringCollege HarbinUniversityofScienceandTechnology Harbin150080 China SchoolofChemicalEngineeringandTechnology ChinaUniversityofMiningandTechnologyXuzhou221008China

Many attempts have been made to control the regioselectivity for olefin poly- merization by varying the structures of ligands in catalysts. The regioselectivity of propylene polymerization was investigated by replacing a nitrogen atom in the Pd(ii) diimine catalyst with an oxygen atom from density functional theory method at the B3LYP/LANL2DZ level. The results show that the 1,2-insertion becomes a rival mechanism to the 2,1-insertion when the nitrogen atom is replaced by the oxygen atom leading to an asymmetric environment in the catalyst, and that the steric effect in the asymmetrical catalyst plays an important part in the polymerization. The insertion barrier from 2-O is much higher than that from 2-N. A pyramid transition state was characterized for the catalyst to convert 2-O back to 2-N through internal rotation. The propylene prefers to coordinate at the opposite side of O in the catalyst. This is the driving force for the internal rotation. The results are significant for isotactic and syndiotactic polymerization.

关键词： regioselectivity salicyladiminato-Pd(ii) catalyst propylene polymerization density functional theory method (DFT)

Mechanism of Variance of Moment of inertia in Fermion Dynamical Symmetry Model

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Chinese Physics Letters 1995年第12期12卷 709-712页

作者： di Yaomin Department of Physics Xuzhou Teachers’CollegeXuzhou 221009

The mechanism of variance of moment of inertia in the fermion dynamical symmetry model is *** is shown that the heritage mixing is indeed the major factor causing the variance of moment of inertia in well-deformed nuclei,but the scheme of the mixing and the form of heritage mixing interaction are important to describing the phenomenon.

关键词： mixing inertia variance

Austempering of hot rolled transformation-induced plasticity steels

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Journal of University of Science and Technology Beijing 2008年第2期15卷 143-149页

作者： Zhuang Li di Wu Department of Materials Engineering Institute of Shenyang Aeronautical Engineering Shenyang 110034 China State Key Lab of Rolling and Automation Northeastern University Shenyang 110004 China

Thermomechanical controlled processing （TMCP） was conducted by using a laboratory hot rolling mill. Austempering in the salt bath after hot rolling was investigated. The effect of isothermal holding time on mechanical properties was studied through examining of the microstructure and mechanical properties of the specimens. The mechanism of transformation-induced plasticity （TRiP） was discussed. The results show that the microstructure of these steels consists of polygonal ferrite, granular bainite, and a significant amount of stable retained austenite. Strain-induced transformation to martensite of retained austenite and TRiP occur in the hot rolled Si-Mn TRiP steels. Excellent mechanical properties were obtained for various durations at 400℃. Prolonged holding led to cementite precipitation, which destabilized the austenite. The mechanical properties were optimal when the specimen was held for 25 min, and the tensile strength, total elongation, and strength ductility balance reached the maximum values of 776 MPa, 33%, and 25608 MPa.%, respectively.

关键词： austempering hot rolling transformation induced plasticity mechanical properties

Cephalic anatomy highlights morphological adaptation to underground habitats in a minute lacewing larva of dilar (dilaridae) and conflicting phylogenetic signal in Neuroptera

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insect Science 2023年第5期30卷 1445-1463页

作者： di Li Kenny Jandausch Hans Pohl Margarita i.Yavorskaya Xingyue Liu Rolf G.Beutel Department of Entomology College of Plant ProtectionChina Agricultural UniversityBeijingChina institut für Zoologie und Evolutionsforschung Friedrich-Schiller-Universität JenaJenaGermany Department of Evolutionary Biology and Ecology Albert Ludwig University FreiburgFreiburgGermany institute of Evolution and Ecology University of TübingenTübingenGermany

dilaridae are a distinctive and phylogenetically ambiguous neuropteran *** far,the anatomy of the immature stages remains largely *** examined the 1st instar larvae of dilar montanus in detail and present results of live observations for the first *** minute,cryptic larvae display features correlated with their underground lifestyle:for instance,a strongly flattened head,stout antennae,eyelessness,and burrowing *** contrast to molecular data,several characters suggest a‘dilarid clade’combining dilaridae with Mantispoidea,for instance a very thin and curved or reduced tentorial bridge,and an elongated *** found intrinsic antennal muscles and Johnston's organ,the first record of these structures in holometabolous *** proves that the first 2 larval antennomeres are homologous with the scapus and *** described characters are discussed and analyzed with an updated matrix of neuropteran larval *** scenarios of character evolution are ***,we show how the 1st-instar larvae move and feed in the substrate,and also provide a high-resolution video recording of the function of the elongate tubular ovipositor and the egg-laying behavior in an adult female under natural conditions.

关键词： anatomy biology first instar Neuropterida phylogeny

Nonlinear autopilot design for interceptors with tail fins and pulse thrusters via θ–D approach

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Journal of Systems Engineering and Electronics 2014年第2期25卷 273-280页

作者： Quan Li di Zhou School of Astronautics Harbin Institute of Technology

The missile autopilot for an interceptor with tail fins and pulse thrusters is designed via the θ-D approach. The nonlin- ear dynamic model of the pitch and yaw motion of the missile is transformed into a linear-like structure with state-dependent coef- ficient （SDC） matrices. Based on the linear-like structure, a θ-D feedback controller is designed to steer the missile to track refer- ence acceleration commands. A sufficient condition that ensures the asymptotic stability of the tracking system is given based on Lyapunov＇s theorem. Numerical results show that the proposed autopilot achieves good tracking performance and the closed-loop tracking system is asymptotically stable.

关键词： blended control nonlinear control suboptimal control,θ-D approach.

investigation of the porous drag and permeability at the porous-fluid interface: influence of the filtering parameters on Darcy closure

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Particuology 2023年第7期78卷 122-135页

作者： Wojciech Sadowski Francesca di Mare Chair of Thermal Turbomachines and Aeroengines Department of Mechanical EngineeringRuhr University BochumUniversitatsstr.15044801Germany

The porous-fluid interface encompasses a region bridging the flow inside a porous medium and a free-flowing *** the context of volume-averaged simulations,it can be described by a set of gradually changing parameters defining the porous medium,mainly porosity and *** this paper,both the permeability and the porous-induced drag force are evaluated a-priori,by explicitly filtering a set of Particle-Resolved Simulations(PRS)of the flow in the channel partially occupied by the porous *** porous matrices are considered and the influence of the geometry and filtering parameters on the macroscopic quantities is ***,the focus is placed on the requirements for the kernel type and size to perform filtering accurately,and their impact on the distribution of permeability at the *** performance of the typically used models for the permeability is compared to the explicitly filtered ***,a new model for permeability and the drag force is introduced,taking into account the information about the fltering size and non-uniformity of the velocity *** model greatly improves the prediction of velocity at the porous-fluid interface and serves as a proof of concept that a successful porous drag model should strive to include information about both parameters.

关键词： Porous-fluid interface Explicit filtering Permeability Porous drag

Nonlinear Out-of-Plane Mechanical Behaviours of Rectangular Woven Composite Flexible Skin Under Uniform Normal Pressure

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Acta Mechanica Solida Sinica 2023年第5期36卷 672-684页

作者： di Chen Jun-Jiang Xiong School of Mechanical Engineering and Automation Beihang UniversityBeijing 100191China School of Transportation Science and Engineering Beihang UniversityBeijing 102206China

This paper seeks to investigate nonlinear out-of-plane mechanical behaviours of woven composite flexible skin(WCFS)through experimental and theoretical ***,quasi-static experiments are carried out on rectangular WCFSs with different aspect ratios under uniform normal pressure to measure out-of-plane deformation and failure ***,a new three-parameter geometric model is presented to describe 3D geometry of pressurized WCFS,and thus,a nonlinear mechanical model is deduced for depicting the relationship between pressure and out-of-plane *** application of the aforementioned models for experimental results shows that the new models have adequately and logically depicted deformation geometry and nonlinear mechanical characteristics.

关键词： Woven compositeﬂexible skin Nonlinear performance Uniform normal pressure Geometric model Mechanical model Aspect ratio