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Tribological Properties of CrN Coated H13 Grade Tool Steel

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Journal of Iron and Steel Research(International) 2014年第2期21卷 240-245页

作者： Erdem Atar zgür Alpaslan zgür elik Hüseyin imenoglu Department of Materials Science and Engineering Gebze Institute of Technology Small and Medium Sized Enterprises Development Organization Metallurgical and Materials Engineering Department Istanbul Technical University

The characteristics of CrN coated martensitic H13 grade tool steels were studied. CrN coatings were depos- ited by the arc physical vapor deposition （PVD） before and after the pulse plasma nitriding of the samples. The PVD and plasma nitriding techniques were applied in relevant workshops by following the commercial practice parameters. Experimental results showed that CrN coating deposited on the nitrided surfaces exhibited superior scratch and wear resistances as compared to that deposited on the original martensitic surface.

关键词： CrN coating nitriding PVD tool steel wear

Magneto-rheological elastomer (MRE) based composite structures for micro-vibration control

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Earthquake Engineering and Engineering Vibration 2010年第3期9卷 345-356页

作者： YQ Ni zg Ying ZH Chen Department of Civil and Structural Engineering The Hong Kong Polytechnic University Hung Horn Kowloon Hong Kong China Department of Mechanics Zhejiang University Hangzhou 310027 China

Magneto-rheological elastomers （MILEs） are used to construct composite structures for micro-vibration control of equipment under stochastic support-motion excitations. The dynamic behavior of MREs as a smart viscoelastic material is characterized by a complex modulus dependent on vibration frequency and controllable by external magnetic fields. Frequency-domain solution methods for stochastic micro-vibration response analysis of the MRE-based structural systems are developed to derive the system frequency-response function matrices and the expressions of the velocity response spectrum. With these equations, the root-mean-square （RMS） velocity responses in terms of the one-third octave frequency band spectrum can be calculated. Further, the optimization problem of the complex moduli of the MRE cores is defined by minimizing the velocity response spectra and the RMS velocity responses through altering the applied magnetic fields. Simulation results illustrate the influences of MRE parameters on the RMS velocity responses and the high response reduction capacities of the MRE-based structures. In addition, the developed frequency-domain analysis methods are applicable to sandwich beam structures with arbitrary cores characterized by complex shear moduli under stochastic excitations described by power spectral density functions, and are valid for a wide frequency range.

关键词： magneto-rheological elastomer (MRE) micro-vibration control equipment composite structure sandwich beam stochastic excitation

A remark on "an approximation condition and extremal quasiconformal extension

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Chinese Science Bulletin 1997年第21期42卷 1765-1767页

作者： Chen, JX Chen, zg Fudan Univ Dept Math Shanghai 200433 Peoples R China

LET D be the unit disk in the complex plane C and f be a sense preserving quasisymmetrichomeomorphism of D onto itself. Denote by Q a quadrilateral D （z1, z2, z3, z4 ） with do-main D and vertices z1, z2, z3, z4 ∈D,... 详细信息

关键词： quasisymmetric function extremal quasiconformal mapping Teichmüller mapping.

Forecasting volatility in oil prices with a class of nonlinear volatility models:smooth transition RBF and MLP neural networks augmented GARCH approach

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Petroleum Science 2015年第3期12卷 534-552页

作者： Melike Bildirici zgÖrü Ersin Department of Economics Yildiz Technical University Department of Economics Beykent University

In this study, the forecasting capabilities of a new class of nonlinear econometric models, namely, the LSTAR-LST-GARCH-RBF and MLP models are evalu- ated. The models are utilized to model and to forecast the daily returns of crude oil prices. Many financial time series are subjected to leptokurtic distribution, heavy tails, and nonlinear conditional volatility. This characteristic feature leads to deterioration in the forecast capabilities of tradi- tional models such as the ARCH and GARCH models. According to the empirical findings, the oil prices and their daily returns could be classified as possessing nonlinearity in the conditional mean and conditional variance processes. Several model groups are evaluated：（i） the models pro- posed in the first group are the LSTAR-LST-GARCH models that are augmented with fractional integration and asymmetric power terms （FIGARCH, APGARCH, and FIAPGARCH）; （ii） the models proposed in the second group are the LSTAR-LST-GARCH models further aug- mented with MLP and RBF type neural networks. The models are compared in terms of MSE, RMSE, and MAE criteria for in-sample and out-of-sample forecast capabili- ties. The results show that the LSTAR based and neural network augmented models provide important gains over the single-regime baseline GARCH models, followed by the LSTAR-LST-GARCH type models in terms of mod- eling and forecasting volatility in crude oil prices.

关键词： Volatility Petrol prices ARCH STAR Neural networks LSTAR-LST-GARCH family

In vitro antitumor activity of titanocene alanine complex and its interaction with nucleic acids

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Chinese Journal of Chemistry 1997年第3期15卷 225-233页

作者： Zhang, zg Jin, L Yang, P SHANXI UNIV INST MOL SCITAIYUAN 030006SHANXIPEOPLES R CHINA

Titanocene alanine complex, Cp2Ti(O2CCH(CH3)NH3+Cl-)(2), has been found to have in vitro antitumor activity against Ehrlich ascites tumor cells. Study of the interaction between Cp2Ti(O2CCH(CH3)NH3+Cl-)(2) and DNA by UV-VIS spectra, fluorescence spectra, agarose gel electrophoresis reveals that Cp2Ti(O2CCH(CH3)NH3+Cl-)(2) forms a stable compound with DNA in molar ratio 1:1 and reduces the migration rate of ccc-DNA band and oc-DNA band. However, unlike cisplatin, the complex does not induce nicking of DNA even after a long incubation at a high ratio of the complex to DNA. The results suggest that titanocene-based antitumor agents have different mechanism of action from cisplatin-like antitumor agents.

关键词： titanocene alanine complex DNA antitumor

Effects of different growing media on the cut flower performances of oriental two Lilium varieties

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International Journal of Agricultural and Biological Engineering 2020年第5期13卷 85-92页

作者： Özgül Karagüzel Bati Akdeniz Agricultural Research Institute Vegetables and Ornamental Plants DepartmentMinistry of Agriculture and ForestryAntalya 07100Turkey

In this study,six different growing media(peat+pumice:1:1,v/v;peat+perlite:1:1,v/v;rice hull+pumice:1:2,v/v;coarse sand+peat:2:1,v/v;soil;and cocopeat)were evaluated for their effects on the plant growth and flower quality of the oriental‘Siberia’and‘Vespucci’lily *** hundred and twenty bulbs were planted in perforated plastic crates and placed in an unheated *** physical and chemical properties of the growing media were *** number of days to flowering,plant height,the number of flowers,fresh stem weight,the number of leaves and vase life were investigated in the *** results indicated that the use of soilless growing media significantly affected plant growth and flower quality when compared with *** obtained values varied by substrate *** earliest flowering time(154.78 d)and the longest plant height(120.82 cm in the‘Siberia’variety)were determined in peat+pumice,whereas the largest number of flowers(7 flowers in Siberia;5.67 flowers in Vespucci)and the highest stem weight(266.13 g in Vespucci;353.91 g in Siberia)were recorded in *** vase life of the plants grown in soil was longer than that of the plants grown in the soilless *** the number of leaves,rice hull+pumice(57.42 leaves)and sand+peat(54.46 leaves)gave the best results.

关键词： Lilium varieties growing media plant growth flower quality

Protein adsorption, cell viability and corrosion properties of Ti6Al4V alloy treated by plasma oxidation and anodic oxidation

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International Journal of Minerals,Metallurgy and Materials 2020年第9期27卷 1269-1280页

作者： ÖzgüBayrak Hojjat Ghahramanzadeh Asl Ayşe Ak Department of Mechanical Engineering Erzincan Binali Yıldırım UniversityErzincan 24100Turkey Department of Mechanical Engineering Karadeniz Technical UniversityTrabzon 61080Turkey Vocational School of Health Services Medical Imaging Techniques ProgrammeKocaeli UniversityKocaeli 41001Turkey

The hardness,wettability,and electrochemical properties of Ti6Al4V alloy surfaces treated with anodic oxidation and plasma oxidation as well as the viabilities of the different cell lines on the obtained surfaces were *** anodic oxidation was performed for 10 min under 100 V potential,and it resulted in a 0.95μm thick nanoporous anatase-TiO2 *** the other hand,plasma oxidation was carried out at 650℃ for 1 h and resulted in a dense rutile-TiO2 structure with a thickness of 1.2μ*** a hardness of HV0.025823 and roughness of^220 nm were obtained by plasma oxidation,those obtained by anodic oxidation were HV0.025512 and^130 nm,*** anodic oxidation process created a more hydrophilic surface with a contact angle of 87.2°.Both oxidation processes produced similar properties in terms of corrosion behavior and showed better resistance than the as-received state in a certain range of ***,the surface treatments led to no significant change in the protein adsorption levels,which indicates that the difference in viability between the osteoblast and fibroblast cells was not due to the difference in surface protein *** all the factors,the surfaces obtained by anodic oxidation treatment revealed higher cell viability than those obtained by plasma oxidation(p=0.05).

关键词： Ti6Al4V oxidation corrosion cell viability protein adsorption

Microstructure and hardness of Mg-based composites reinforced with Mg_2Si particles

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Rare Metals 2009年第4期28卷 396-400页

作者： Mustafa Aydin Cem zgür Osman San Mechanical Engineering Department Dumlupinar University Ceramic Engineering Department Dumlupinar University

Magnesium powders were mechanically alloyed with SiO2 powder particles having different particle sizes using nigh-energy ball milling techniques under Ar atmosphere for 1 h. The powders were consolidated with cold pressing under 560 MPa. They were then sintered at 550℃ for 45 min under Ar atmosphere. The composites obtained on the Mg-SiO2 system were investigated using the Archimedes principle, a differential scanning calorimeter, X-ray diffraction, optic microscopy, and scanning electron microscopy. For the mechanically alloyed powders, the solid-state reaction of the synthesis of Mg2Si and MgO progressed further during sintering of the materials. The results showed that the strengthening mechanisms were dependent on dispersion hardening of fine Mg2Si and MgO particulates dispersed homogeneously in the matrix. Mg-

关键词： based composites SiO2 mechanical alloying strengthening mechanism

Investigation on Hygrothermal Effect of Hybrid Composites

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Journal of Materials Science & Technology 1996年第3期12卷 209-214页

作者： Zhang, zg Zhong, WH Liang, ZY BEIJING UNIV AERONAUT & ASTRONAUT DEPT MAT SCI & ENGNBEIJING 100083PEOPLES R CHINA

In this paper, moisture absorption characteristics of Carbon/Glass and Carbon/Aramid hybrid composites with two types of matrices are investigated. The weight gain of the specimens are tested at 80 degrees C. It is found that the water diffusion in hybrid composites can be described by Fickian process. The step-by-step model and new thermal model are developed to estimate the equilibrium moisture content (M(m)) and water diffusion coefficient (D) in hybrid composites using the hybrid structure parameters (hybrid ratio and hybrid interface number). The estimated values are in good agreement with the experimental results.

关键词： Investigation on Hygrothermal Effect of Hybrid Composites