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151.
X-ray absorption investigation of the site occupancies of the copper element in nominal Cu_3Zn(OH)_6FBr 下载免费PDF全文
Ruitang Wang Xiaoting Li Xin Han Jiaqi Lin Yong Wang Tian Qian Hong Ding Youguo Shi Xuerong Liu 《中国物理 B》2021,(4):440-445
With Zn substitution to the three-dimensional antiferromagnetically ordered barlowite Cu_4(OH)_6 FBr,Cu_3 Zn(OH)_6 FBr shows no magnetic phase transition down to 50 mK,and the system is suggested to be a two-dimensional kagome quantum spin liquid [Chin.Phys.Lett.34 077502(2017)].A key issue to identify such phase diagram is the exact chemical formula of the substituted compound.With Cu L-edge x-ray absorption spectrum(XAS) combined with the MultiX XAS calculations,we evaluate the Cu concentration in a nominal Cu_3 Zn(OH)_6 FBr sample.Our results show that although the Cu concentration is 2.80,close to the expected value,there is 34% residual Cu occupation in intersite layers between kagome layers.Thus the Zn substitution of the intersite layers is not complete,and likely it intrudes the kagome layers. 相似文献
152.
Hong Shi Qianwei Zhang Wenbing Xu Meinan Liu Jiashuang Pan Jie Yuan Kaijie Yang 《Entropy (Basel, Switzerland)》2022,24(8)
Polar cruise ships are exposed to extreme external conditions during voyages, resulting in cockpit windscreens that are prone to fogging and frosting, seriously affecting the driver’s vision and even threatening navigation safety. However, the current research mainly focuses on cabin comfort, ignoring the coupling of defogging and comfort. Accordingly, this paper combines cockpit-windshield-defogging design and cockpit comfort considerations, and proposes 108 orthogonal-ventilation design parameters based on the four basic ventilation methods. The effects of different air supply parameters on comfort and anti-fog characteristics are investigated by using fluid dynamics simulation methods. The entropy weight–TOPSIS algorithm is employed to find the optimal ventilation parameters. The results show that the “Down-supply up-return type vertical jet” air supply method corresponding to an air supply velocity of 1 m/s, an air supply temperature of 297 K, and an air supply relative humidity of 30% has the smallest Euclidean distance from the positive ideal solution, and the largest Euclidean distance from the negative ideal solution; thus, it obtains a higher and the highest priority. This air supply method provides the best thermal comfort for the drivers, as well as the best anti-fogging and defogging effect. The results can be useful to provide suggestions for the future design of the air-conditioning systems in polar cruise ships. 相似文献
153.
本文根据有限区间上Riemann积分的Arzela控制收敛定理[1],给出无穷限积分的控制收敛定理,并做了相应的推广。 相似文献
154.
Lushan Yang & Deming Shi 《偏微分方程(英文版)》1995,8(3):233-241
In this paper, a class of evolution equations which have special boundary conditions is discussed. The spectrum properties of an operator which is associated with this class of equations arc provided, and the existence and uniqueness of solutions of this class of equations is proved by the theory of pertu rbation of C_0-semigroups. In the last part of this paper, a condition which ensures the solutions to be non-negative is given. Some results of the time-independent population systems in [1-5] are our examples. 相似文献
155.
为了研究硬质合金表面激光微织构对其表面润湿性的影响,利用光纤激光不同功率(3,5,7,9,10 W)及不同加工次数(1,2,3,4,5)加工微凹坑,采用VHX1000c超景深三维显微镜、光学显微镜分析微凹坑形貌,利用CAM 200光学接触角仪测量表面微织构(微凹坑直径、深度和织构密度)与润湿性之间的关系。结果表明:随着激光功率的增大,微凹坑深度增加,直径变化不明显;硬质合金表面的亲水性能随着微凹坑深度的增加而减小;随着微凹坑直径的增大,亲水性增强;随着微织构密度的增加,亲水性出现极值。 相似文献
156.
Jianhua Yan Lida Xu Decai Fang Shi‐Zhong Luo 《Journal of Physical Organic Chemistry》2014,27(12):981-985
Photolabile protecting groups have been extensively studied and applied for protection of small biological molecules, which make it convenient to detect the biological processes of the caged compounds. In this study, a series of 8‐nitroquinoline‐based photolabile caging groups for carboxylic acid were synthesized with improved photolysis efficiency. Among them, 6‐bromo‐8‐nitro‐1, 2‐dihydroquinolinyl chromophore was proven the best derivative on account of its longest absorption wavelength (345 nm), highest caging ability, and quantum yield (Φ = 0.003). Moreover, density functional theory calculations were performed in order to study the photolysis mechanisms. Theoretical calculations revealed that the reaction was kinetically inert under general mild condition with the high barrier height of 34.3 kcal/mol at carbonyl migration step, while under the photolysis condition, because of the large energy gap (64.5 kcal/mol) between S0 and S1 states, the reaction should be accessible in the triplet ground state (T1) through successive excitation of S0 → S1 states, subsequent intersystem crossing of S1 → T1 states, and finally returned to the stable S0 state for product via potential energy surface crossing between T1 and S0 states. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
157.
158.
为实现25 GW级双路输出超宽谱高功率微波驱动源的小型化,选择研制了一种与双筒脉冲形成线(Blumlein线)相配一体化的带有开路磁芯的Tesla变压器,作为初级脉冲功率源。进行了Tesla变压器的理论分析,利用简化的磁路模型研究了Tesla变压器初次级线圈电感等电参数的估算方法,给出了Tesla变压器磁芯截面的估算和磁芯制作方法。该Tesla变压器最大输出电压880 kV,充电时间约20 s,耦合系数约0.95,实验结果与理论设计相符。 相似文献
159.
T.F. Zheng Y.G. Shi C.C. Hu J.Y. Fan D.N. Shi S.L. Tang Y.W. Du 《Journal of magnetism and magnetic materials》2012
Single phase Mn5Ge3 ribbons were successfully synthesized by single roller melt-spinning method followed by an annealing procedure at 800 °C for 1 h. The magnetocaloric effect and transition order were investigated by dc magnetization measurement. A maximum entropy change of 4.92 J/kg K and a refrigerant capacity of 201.3 J/kg were observed at an external field change of 30 kOe. The Banerjee criterion was adopted to discriminate the order of the transition, indicating a second order transition. The calculated entropy changes were also obtained by Landau theory, which are in agreement with the experimental values at the temperature region above the Curie temperature. This phenomena implies a potential transition of the magnetic interaction in the vicinity of the Curie temperature. Universal behavior was also indicated in that all of the experimental entropy change curves collapse into one universal curve, which is consistent with the Banerjee criterion. 相似文献
160.
Yuntao Wu Dongzhou Ding Shangke Pan Fan Yang Junyan Shi Guohao Ren 《Journal of luminescence》2012,132(2):251-255
Lu0.8Sc0.2BO3 crystals doped with 1 at%Ce3+ and co-doped 0.1 at% and 0.5 at%Pr3+ were grown by the Czochralski method. The concentrations of Pr3+ and Ce3+ in crystals were measured by the ICP-AES method. Absorption spectra, VUV–UV spectra, fluorescence decay time and X-ray excitation luminescence spectra were investigated at room temperature. The excitation luminescence spectra of Ce3+ emission and decay curves from the lower excited state levels of the 4f15d1 and 5d1 electronic configurations of the Pr3+ and Ce3+ conspicuously indicated the non-radiative energy transfer from Pr3+ to Ce3+. The detailed pathways were shown in the energy level diagram of the respective Ce3+ and Pr3+ in Lu0.8Sc0.2BO3 host. In addition, the scintillation efficiency data indicated that the energy transfer effect is directly associated with the Pr3+ concentration. 相似文献