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41.
Let G be a connected graph and D(G) be its distance matrix. In this article, the Smith normal forms of the integer matrices D(G) are determined for trees, wheels, cycles, complements of cycles and are reduced for complete multipartite graphs. 相似文献
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《Discrete Mathematics》2019,342(10):2834-2842
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《Discrete Mathematics》2022,345(10):112999
Ryser proved that any two tournaments with the same score sequence are -equivalent while Beineke and Moon proved the -equivalence for any two bipartite tournaments with the same score lists. In this paper, we extend these results to orientations of G vertex-multiplications. We focus on two main areas, namely orientations with the same score list and with score-list parity. Our main tools are extensions of the refinement technique, directed difference graph and a reduction lemma. 相似文献
46.
The looming global energy crisis and ever-increasing energy demands have catalyzed the development of renewable energy storage systems. In this regard, supercapacitors (SCs) have attracted widespread attention because of their advantageous attributes such as high power density, excellent cycle stability, and environmental friendliness. However, SCs exhibit low energy density and it is important to optimize electrode materials to improve the overall performance of these devices. Among the various electrode materials available, spinel nickel cobaltate (NiCo2O4) is particularly interesting because of its excellent theoretical capacitance. Based on the understanding that the performances of the electrode materials strongly depend on their morphologies and structures, in this study, we successfully synthesized NiCo2O4 nanosheets on Ni foam via a simple hydrothermal route followed by calcination. The structures and morphologies of the as-synthesized products were characterized by X-ray diffraction, scanning electron microscopy, and Brunauer-Emmett-Teller (BET) surface area analysis, and the results showed that they were uniformly distributed on the Ni foam support. The surface chemical states of the elements in the samples were identified by X-ray photoelectron spectroscopy. The as-synthesized NiCo2O4 products were then tested as cathode materials for supercapacitors in a traditional three-electrode system. The electrochemical performances of the NiCo2O4 electrode materials were studied and the area capacitance was found to be 1.26 C·cm-2 at a current density of 1 mA·cm-2. Furthermore, outstanding cycling stability with 97.6% retention of the initial discharge capacitance after 10000 cycles and excellent rate performance (67.5% capacitance retention with the current density from 1 to 14 mA·cm-2) were achieved. It was found that the Ni foam supporting the NiCo2O4 nanosheets increased the conductivity of the electrode materials. However, it is worth noting that the contribution of nickel foam to the areal capacitance of the electrode materials was almost zero during the charge and discharge processes. To further investigate the practical application of the as-synthesized NiCo2O4 nanosheets-based electrode, a device was assembled with the as-prepared samples as the positive electrode and active carbon (AC) as the negative electrode. The assembled supercapacitor showed energy densities of 0.14 and 0.09 Wh·cm-3 at 1.56 and 4.5 W·cm-3, respectively. Furthermore, it was able to maintain 95% of its initial specific capacitance after 10000 cycles. The excellent electrochemical performance of the NiCo2O4 nanosheets could be ascribed to their unique spatial structure composed of interconnected ultrathin nanosheets, which facilitated electron transportation and ion penetration, suggesting their potential applications as electrode materials for high performance supercapacitors. The present synthetic route can be extended to other ternary transition metal oxides/sulfides for future energy storage devices and systems. 相似文献
47.
Wei Liu Chao-Nan Yang Zhong-Lin Yang Ru-Jia Yu Prof. Yi-Tao Long Prof. Yi-Lun Ying 《Angewandte Chemie (International ed. in English)》2023,62(27):e202304023
Disulfide bonds play an important role in thiol-based redox regulation. However, owing to the lack of analytical tools, little is known about how local O2 mediates the reversible thiol/disulfide cycle under protein confinement. In this study, a protein-nanopore inside a glove box is used to control local O2 for single-molecule reaction, as well as a single-molecule sensor for real-time monitoring of the reversible thiol/disulfide cycle. The results demonstrate that the local O2 molecules in protein nanopores could facilitate the redox cycle of disulfide formation and cleavage by promoting a higher fraction of effective reactant collisions owing to nanoconfinement. Further kinetic calculations indicate that the negatively charged residues near reactive sites facilitate proton-involved oxygen-induced disulfide cleavage under protein confinement. The unexpectedly strong oxidation ability of confined local O2 may play an essential role in cellular redox signaling and enzyme reactions. 相似文献
48.
This paper determines lower bounds on the number of different cycle lengths in a graph of given minimum degree k and girth g. The most general result gives a lower bound of ckg/8. 相似文献
49.
新一代核能布雷顿闭式循环热力学分析研究 总被引:3,自引:2,他引:1
核能利用是20世纪最激动人心的科学成就之一。核能和平利用的重点在核能发电,至今核电站反应堆多为低温水冷堆,采用水或重水作为冷却剂和慢化剂,堆出口载热工质温度较低(280“C~340“q,因而多应用常规的Rankine蒸汽热力循环,热转功的效率较低(28%~33%)。90年代以来,随着工业和航空燃气轮机技术长足进步和高温核反应堆的进展,核能布雷顿闭式循环(NEBCC)展现出提高性能的潜力和发展前景,受到普遍关注。近期提出的模块化高温气冷堆氦气轮机(MHR--GT)[‘-‘]就是应用NEBCC的典型… 相似文献
50.
《Particuology》2023
Cycle Time Distribution (CTD) plays a critical role for determining uniformity of particle coating in spray fluidized beds. However, the CTD is influenced by both geometrical structure and operating conditions of fluidized bed. In this study, a spray fluidized bed of coating process is simulated by a comprehensive Computational Fluid Dynamics-Discrete Element Model (CFD-DEM). To achieve different behaviors of CTD, some modifications are designed on a pseudo-2D internally circulating fluidized bed, which traditionally composes of a high-velocity upward bed and low-velocity downward bed. These modifications include making the air distributor slope and/or laying a baffle in the downward bed. First, the CTD and evolution of particle size distribution under different bed structures are compared. The CTD directly influences the coating uniformity. By making the particles flowing along a parallel direction in the downward bed through the geometrical modifications, the CTD becomes narrower and the coating uniformity is significantly improved. Second, under the optimized bed structure, the influence of operating conditions on the coating uniformity is studied. Properly increasing the fluidization gas velocity and the fluidization gas temperature and reducing the liquid spray rate can improve the coating uniformity. 相似文献