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81.
To describe the yield-point phenomena of steels, an extended version of the first author’s model (Yoshida, F., 2000. A constitutive model of cyclic plasticity. International Journal of Plasticity 16, 359–380) is proposed on the premise that the material behavior of sharp yield point and the subsequent abrupt yield drop result from a rapid dislocation multiplication and the stress-dependence of dislocation velocity. A specific feature of this model is that it describes well a high upper yield point, the rate-dependent Lüders strain at the yield plateau and the subsequent workhardening, as well as cyclic plasticity characteristics, such as the Bauschinger effect and rate-dependent ratcheting. Using this model, an FE simulation of temper rolling process is conducted in order to clarify its role for the elimination of the yield point of steel sheets. Particularly, the effect of upper yield point on the deformation characteristics in the process is discussed. 相似文献
82.
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84.
Killgore JP Yablon DG Tsou AH Gannepalli A Yuya PA Turner JA Proksch R Hurley DC 《Langmuir : the ACS journal of surfaces and colloids》2011,27(23):13983-13987
We demonstrate the accurate nanoscale mapping of near-surface loss and storage moduli on a polystyrene-polypropylene blend with contact resonance force microscopy (CR-FM). These viscoelastic properties are extracted from spatially resolved maps of the contact resonance frequency and quality factor of the AFM cantilever. We consider two methods of data acquisition: (i) discrete stepping between mapping points and (ii) continuous scanning. For point mapping and low-speed scanning, the values of the relative loss and storage modulus are in good agreement with the time-temperature superposition of low-frequency dynamic mechanical analysis measurements to the high frequencies probed by CR-FM. 相似文献
85.
Depending on protein environment, a single photofunctional chromophore shows a wide variation of photoabsorption/emission energies. This photobiological phenomenon, known as color tuning, is observed in human visual cone pigments, firefly luciferase, and red fluorescent protein. We investigate the origin of color tuning by quantum chemical calculations on the excited states: symmetry-adapted cluster-configuration interaction (SAC-CI) method for excited states and a combined quantum mechanical (QM)/molecular mechanical (MM) method for protein environments. This Minireview summarizes our theoretical studies on the above three systems and explains a common feature of their color-tuning mechanisms. It also discuss the possibility of artificial color tuning toward a rational design of photoabsorption/emission properties. 相似文献
86.
Yasukazu Sugiyama Kento Yamada Daiki Kaneko Yuya Kusagawa Dr. Toshitaka Okamura Prof. Dr. Takaaki Sato 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(6):e202317290
A reductive (3+2) annulation of lactams through iridium-catalyzed hydrosilylation and photoredox coupling with α-bromoacetic acid was developed. The iridium-catalyzed hydrosilylation of the lactam carbonyl group and subsequent elimination provide a transient cyclic enamine, which undergoes iridium-catalyzed photoredox coupling with α-bromoacetic acid in a one-pot process. The developed conditions show high functional-group tolerance and provide cyclic N,O-acetals containing a quaternary carbon center. The resulting N,O-acetals undergo a variety of acid-mediated nucleophilic addition reactions via iminium ions to give substituted cyclic amines. The developed sequence including reductive (3+2) annulation and acid-mediated nucleophilic addition was successfully applied to the four-step total synthesis of (±)-eburnamonine. 相似文献
87.
Taiki Nakatomi Shoichi Koido Yuya Watabe Toshiyuki Takayanagi 《International journal of quantum chemistry》2019,119(11):e25908
The mechanisms including spin-inversion have been systematically studied for the M+ + OCS → MS+ + CO/MO+ + CS (M denotes a transition metal from Sc to Cu) ion-molecule reactions using the automated reaction path search method. We used the lowest mixed-spin potential energy surface obtained from the diagonalization of the spin-coupled Hamiltonian matrix, whose diagonal elements are taken to be the lowest two spin states. This scheme can effectively locate approximate minimum energy crossing points between the two potential energy surfaces with different spin multiplicities. The spin-orbit couplings at spin-inversion points have been calculated to understand the efficiencies of nonadiabatic transitions. The obtained reaction pathways and the calculated spin-orbit couplings are employed to interpret previous experimental studies. 相似文献
88.
Hiroaki Nitani Masato Yuya Takahiro Ono Takashi Nakagawa Satoshi Seino Kenji Okitsu Yoshiteru Mizukoshi Shuichi Emura Takao A. Yamamoto 《Journal of nanoparticle research》2006,8(6):951-958
A sample of Au–Pd bimetallic nanoparticles supported on γ-Fe2O3 was synthesized in a sonochemically one-pot process. The structural analyses of the synthesized sample were performed by the techniques of X-ray Absorption Fine Structure (XAFS), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and UV–vis spectrometry. Results indicated that the synthesized sample formed a core-shell structure in which a gold core was surrounded by a thin palladium shell. The reaction rate constant for the hydrogenation of cyclohexene of the present sample showed higher value than that of Pd nanoparticles supported on γ-Fe2O3 and core-shell structured Au–Pd nanoparticles supported on SiO2. The present sample is a promising catalyst material which has a high catalytic activity. 相似文献
89.
Shouji Iwatsuki Tsuneyoshi Okada Yuya Yamashita 《Journal of polymer science. Part A, Polymer chemistry》1968,6(9):2451-2460
The alternating copolymerization of cyclopentene and sulfur dioxide was studied. It takes place spontaneously at ?15°C. The rate of copolymerization in toluene was found to be proportional to [CPT]3 and [SO2]2 with the overall activation energy of 16.5 kcal/mole. Terpolymerizations with eight different third monomers were carried out to examine the character and behavior of the copolymerization system of CPT and SO2. However, the polymerizations with styrene and methyl methacrylate as the third monomers were found to be extraordinary, in that all the three components are not incorporated into the polymer chain. 相似文献
90.
Yohji Nakatsuji Toshinori Inoue Masato Wada Mitsuo Okahara 《Journal of inclusion phenomena and macrocyclic chemistry》1991,10(3):379-386
A new type of 18-crown-6 derivative having two carboxylic acids on the side arms transported calcium and potassium ions in opposite directions across a dichloromethane membrane by pH control. Calcium and potassium ions were concentrated in the acidic and the basic phases, respectively. The presence of picrate ion in the acidic phase plays an important role in the transport of potassium ion from the acidic to the basic phase. 相似文献