First synthesis of 1-(indo1-2-yl)azulenes by the Vilsmeier-Haack type arylation with triflic anhydride as an activating reagent

Azulene derivatives reacted with 2-indolinones in the presence of triflic anhydride (Tf2O) to afford 1-(indo1-2-yl)azulenes in good yields. In the cases of the reaction of 6-tert-butyl-1-(methylthio)azulene (11) and 1-(1,4-dihydropyridin-4-yl)azulene 14, 1,1'-biazulene derivative 24 and 1-(indo1-2-yl)azulene (2) were obtained under the similar reaction conditions, respectively, instead of the presumed electrophilic substitution products.ArticleTETRAHEDRON LETTERS. 53(12):1493-1496 (2012)journal articl

Effects of Aspect Ratio and Distance between Two Square Cylinders in a Tandem Arrangement on In-Line Oscillation Characteristics

When multiple structures, such as the main towers for a bridge, heat exchangers and offshore structures, are placed adjacently in fluid, structures placed in the downstream side are exposed to complicated flow regions, because the separated shear layer reattaches to the downstream structures or interferes with the flow. For this reason, the distance between structures greatly influences changes in flow patterns around the downstream cylinder structures, so that the response characteristics of structures can be altered correspondingly. The purpose of this study is to identify the basic in-line oscillation characteristics of two square cylinders in a tandem arrangement. Based on the supposition of actual structures, spring-supported tests, with both square cylinders elastically suspended, were conducted. Not only the distance between the two cylinders but also the aspect ratio, was also chosen as the parameters. Because it was found by past researches that the in-line oscillation characteristics of single cylinder depends on the aspect ratio, it was thought to be important to confirm it by two cylinders. Furthermore, flow visualization tests were performed by forced-oscillating two cylinders for consideration from the results of the spring-supported test.9th International Symposium on Fluid-Structure Interactions, Flow-Sound Interactions, Flow-Induced Vibration & Noise (FIV2018: FSI2 & FIV+N.), July 8-11, 2018, Toronto, Ontario, Canad

A fast and accurate per-cell dynamic IR-drop estimation method for at-speed scan test pattern validation

ITC : 2012 IEEE International Test Conference , 5-8 Nov. 2012 , Anaheim, CA, USAIn return for increased operating frequency and reduced supply voltage in nano-scale designs, their vulnerability to IR-drop-induced yield loss grew increasingly apparent. Therefore, it is necessary to consider delay increase effect due to IR-drop during at-speed scan testing. However, it consumes significant amounts of time for precise IR-drop analysis. This paper addresses this issue with a novel per-cell dynamic IR-drop estimation method. Instead of performing time-consuming IR-drop analysis for each pattern one by one, the proposed method uses global cycle average power profile for each pattern and dynamic IR-drop profiles for a few representative patterns, thus total computation time is effectively reduced. Experimental results on benchmark circuits demonstrate that the proposed method achieves both high accuracy and high time-efficiency

Acceleration of Seed Ordering and Selection For High Quality VLSI Delay Test

Seed ordering and selection is a key technique to provide high-test quality with limited resources in Built-In Self Test (BIST) environment. We present a hard-to-detect delay fault selection method to optimize the computation time in seed ordering and selection processes. This selection method can be used to select faults for test generation when it is impractical to target all delay faults resulting large test pattern count and long Computation time. Three types of selection categories are considered, ranged in the number of seeds it produced, which is useful when we consider computing resources, such as memory and storage. We also evaluate the impact of the selection method in mixed-mode BIST when seed are expanded to more patterns, and evaluate the statistical delay quality level (SDQL) with the original work. Experimental results show that our proposed method can significantly reduce computation time while slightly sacrificing test quality

Modeling of Thermal Emission from ULX Pulsar Swift J0243.6+6124 with General Relativistic Radiation MHD simulations

We perform general relativistic radiation magnetohydrodynamics (MHD) simulations of super-Eddington accretion flows around a neutron star with a dipole magnetic field for modeling the galactic ultra-luminous X-ray source (ULX) exhibiting X-ray pulsations, Swift J0243.6+6124. Our simulations show the accretion columns near the magnetic poles, the accretion disk outside the magnetosphere, and the outflows from the disk. It is revealed that the effectively optically thick outflows, consistent with the observed thermal emission at $\sim10^7$ K, are generated if the mass accretion rate is much higher than the Eddington rate $\dot{M}_{\rm Edd}$ and the magnetospheric radius is smaller than the spherization radius. In order to explain the blackbody radius ($\sim 100-500$ km) without contradicting the reported spin period ($9.8~{\rm s}$) and spin-up rate ($\dot{P}=-2.22\times10^{-8}~{\rm s~s^{-1}}$), the mass accretion rate of $(200-1200)\dot{M}_{\rm Edd}$ is required. Since the thermal emission was detected in two observations with $\dot{P}$ of $-2.22\times10^{-8}~{\rm s~s^{-1}}$ and $-1.75\times10^{-8}~{\rm s~s^{-1}}$ but not in another with $\dot{P}=-6.8 \times10^{-9}~{\rm s~s^{-1}}$, the surface magnetic field strength of the neutron star in Swift J0243.6+6124 is estimated to be between $3\times10^{11}~{\rm G}$ and $4\times10^{12}~{\rm G}$. From this restricted range of magnetic field strength, the accretion rate would be $(200-500)\dot{M}_{\rm Edd}$ when the thermal emission appears and $(60-100)\dot{M}_{\rm Edd}$ when it is not detected. Our results support the hypothesis that the super-Eddington phase in the 2017-2018 giant outburst of Swift J0243.6+6124 is powered by highly super-Eddington accretion flows onto a magnetized neutron star.Comment: 24 pages, 9 figures, 2 tables, accepted for publication in Ap

Stacking order reduction in multilayer graphene by inserting nanospacers

Toward macroscopic applications of graphene, it is desirable to preserve the superior properties of single-layer graphene in bulk scale. However, the AB-stacking structure is thermodynamically favored for multilayer graphene and causes strong interlayer interactions, resulting in property degradation. A promising approach to prevent the strong interlayer interaction is the staking order reduction of graphene, where the graphene layers are rotated in-plane to form a randomly stacking structure. In this study, we propose a strategy to effectively decrease the stacking order of multilayer graphene by incorporating nanospacers, cellulose nanofibers, or nano-diamonds (NDs) in the formation process of porous graphene sponges. We conducted an ultrahigh temperature treatment at 1500 °C with ethanol vapor for the reduction and structural repair of graphene oxide sponges with different concentrations of the nanospacers. Raman spectroscopy indicated an obvious increase in the random-stacking fraction of graphene by adding the nanospacers. The x-ray diffraction (XRD) analysis revealed that a small amount of the nanospacers induced a remarkable decrease in ordered graphene crystalline size in the stacking direction. It was also confirmed that a layer-number increase during the thermal treatment was suppressed by the nanospacers. The increase in the random-stacking fraction is attributed to the efficient formation of randomly rotated graphene through the ethanol-mediated structural restoration of relatively thin layers induced by the nanospacers. This stacking-order-reduced graphene with bulk scale is expected to be used in macroscopic applications, such as electrode materials and wearable devices.Zizhao Xu, Taiki Inoue, Yuta Nishina, and Yoshihiro Kobayashi, "Stacking order reduction in multilayer graphene by inserting nanospacers", Journal of Applied Physics 132, 174305 (2022) https://doi.org/10.1063/5.010382