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排序方式: 共有171条查询结果,搜索用时 234 毫秒
61.
Tae Ho Yeom 《Journal of Physics and Chemistry of Solids》2011,72(1):56-59
The variations with temperature of the relaxation mechanisms of the 9Be, 27Al, and 29Si nuclei in emerald (Be3Al2Si6O18:Cr3+) single crystals were investigated by using a pulse NMR spectrometer. The values of the spin-lattice relaxation rates for the three nuclei are different, and these differences are attributed to the differences between their Larmor frequencies and their local nuclear environments. The relaxation rates of the 9Be and 27Al nuclei undergo no abrupt changes within the temperature range 180-400 K, which indicates that there are no phase transitions within this temperature range. The spin-lattice relaxation rates of 9Be and 27Al were found to be proportional to temperature. Therefore, the nuclear spin-lattice relaxation processes of these two nuclei proceed via single-phonon processes. 相似文献
62.
63.
Cho WB Kim JW Lee HW Bae S Hong BH Choi SY Baek IH Kim K Yeom DI Rotermund F 《Optics letters》2011,36(20):4089-4091
High-quality monolayer graphene as large as 1.2×1.2?cm2 was synthesized by chemical vapor deposition and used as a transmitting saturable absorber for efficient passive mode-locking of a femtosecond bulk solid-state laser. The monolayer graphene mode-locked Cr:forsterite laser was tunable around 1.25?μm and delivered sub-100?fs pulses with output powers up to 230?mW. The nonlinear optical characteristics of the monolayer graphene saturable absorber and the mode-locked operation were then compared with the case of the bilayer graphene saturable absorber. 相似文献
64.
Kittiwat Tangmongkollert Sujin Suwanna 《The European Physical Journal B - Condensed Matter and Complex Systems》2016,89(6):146
We study the behaviors of magnetization, price, and profit profiles in ring networks inthe presence of the external magnetic field. The Ising model is used to determine thestate of each node, which is mapped to the buy-or-sell state in a financial market, where+1 is identified as the buying state, and ?1 as the selling state. Price and profit mechanisms are modeled basedon the assumption that price should increase if demand is larger than supply, and itshould decrease otherwise. We find that the magnetization can be induced between two ringsvia coupling links, where the induced magnetization strength depends on the number of thecoupling links. Consequently, the price behaves linearly with time, where its rate ofchange depends on the magnetization. The profit grows like a quadratic polynomial withcoefficients dependent on the magnetization. If two rings have opposite direction of netspins, the price flows in the direction of the majority spins, and the network with theminority spins gets a loss in profit. 相似文献
65.
CuSbS2‐Sensitized Inorganic–Organic Heterojunction Solar Cells Fabricated Using a Metal–Thiourea Complex Solution 下载免费PDF全文
Dr. Yong Chan Choi Eun Joo Yeom Prof. Tae Kyu Ahn Prof. Sang Il Seok 《Angewandte Chemie (International ed. in English)》2015,54(13):4005-4009
The device performance of sensitizer‐architecture solar cells based on a CuSbS2 light sensitizer is presented. The device consists of F‐doped SnO2 substrate/TiO2 blocking layer/mesoporous TiO2/CuSbS2/hole‐transporting material/Au electrode. The CuSbS2 was deposited by repeated cycles of spin coating of a Cu‐Sb‐thiourea complex solution and thermal decomposition, followed by annealing in Ar at 500 °C. Poly(2,6‐(4,4‐bis‐(2‐ethylhexyl)‐4H‐cyclopenta[2,1‐b;3,4‐b′]dithiophene)‐alt‐4,7(2,1,3‐benzothiadiazole)) (PCPDTBT) was used as the hole‐transporting material. The best‐performing cell exhibited a 3.1 % device efficiency, with a short‐circuit current density of 21.5 mA cm?2, an open‐circuit voltage of 304 mV, and a fill factor of 46.8 %. 相似文献
66.
M.H. Jeon A.K. Mishra S.-K. Kang K.N. Kim I.J. Kim S.B. Lee T.H. Sin G.Y. Yeom 《Current Applied Physics》2013,13(8):1830-1836
60 MHz pulsed radio frequency (rf) source power and 2 MHz continuous wave rf bias power, were used for SiO2 etching masked with an amorphous carbon layer (ACL) in an Ar/C4F8/O2 gas mixture, and the effects of the frequency and duty ratio of the 60 MHz pulse rf power on the SiO2 etch characteristics were investigated. With decreasing duty ratio of the 60 MHz pulse rf power, not only the etch rate of SiO2 but also the etch rate of ACL was decreased, however, the etch selectivity of SiO2 over ACL was improved with decreasing the duty ratio. On the other hand, when the pulse frequency was varied at a constant duty ratio, no significant change in the etch rate and etch selectivity of both materials could be observed. The variation of the etch characteristics was believed to be related to the change in the gas dissociation characteristics caused by the change in the average electron temperature for different pulsing conditions. The improvement in the etch selectivity with the decrease of duty ratio, therefore, was related to the decreased gas dissociation of C4F8 by the decrease of average electron temperature and, which resulted in a change in composition of the fluorocarbon polymer on the etched materials surface from C–C rich to CF2 rich. With decreasing the duty ratio, not only the etch selectivity but also the improvement in the SiO2 etch profile could be observed. 相似文献
67.
The first total synthesis of 6-hydroxy-7-(hydroxymethyl)-4-methylenehexahydrocyclopenta[c]pyran-1(3H)-one has been accomplished. A key feature of the synthesis includes facile construction of the bicyclic lactone intermediate via intramolecular Pd(0)-catalyzed allylic alkylation and the efficient transformation of this intermediate into the iridoid skeleton employing silicon tethered radical cyclization. 相似文献
68.
69.
We report >13 MHz/mW pump power efficiency in increasing the repetition rate of passive harmonic mode-locking by engineering the soliton pulse energy in Er fiber lasers incorporating carbon nanotube saturable absorber. Stable pulses with a ~5 GHz repetition rate and 40 dB of super-mode suppression are demonstrated with only ~400 mW pump power in a single-clad fiber laser. 相似文献
70.
Tae Ho Yeom Ae Ran Lim 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2009,200(2):261-266
Nuclear magnetic resonance (NMR) data and the spin–lattice relaxation times, T1, of 69Ga and 71Ga nuclei in a β-Ga2O3:Cr3+ single crystal were obtained using FT NMR spectrometry. Four sets of NMR spectra for 69Ga (I = 3/2) and 71Ga (I = 3/2) were obtained in the crystallographic planes. The 69Ga and 71Ga nuclei each had two chemically inequivalent GaI and GaII centers. Each of the 69Ga and 71Ga isotopes yielded two different central NMR resonance lines originating from GaI and GaII sites. The nuclear quadrupole coupling constants and asymmetry parameters of 69GaI, 69GaII, 71GaI, and 71GaII centers in a β-Ga2O3:Cr3+ crystal were obtained. Analysis of the EFG tensor principal axes (PAs) for Ga nuclei and the ZFS tensor PAs for the Cr3+ ion confirmed that the Cr3+ paramagnetic impurity ion substitutes for the Ga3+ ion in the oxygen octahedron. In addition, the temperature dependencies of the 69Ga and 71Ga relaxation rates were consistent with Raman processes, as T1−1 ∝ T2. Even though the Cr3+ impurities are paramagnetic, the relaxations were dominated by electric quadrupole interactions of the nuclear spins in the temperature range investigated. 相似文献