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981.
In this paper, we study reflected BSDE’s with one continuous barrier, under monotonicity and general increasing conditions in y and non-Lipschitz conditions in z. We prove the existence and uniqueness of a solution by an approximation method. 相似文献
982.
Given a fixed multigraph H with V(H) = {h1,…, hm}, we say that a graph G is H‐linked if for every choice of m vertices v1, …, vm in G, there exists a subdivision of H in G such that for every i, vi is the branch vertex representing hi. This generalizes the notion of k‐linked graphs (as well as some other notions). For a family of graphs, a graph G is ‐linked if G is H‐linked for every . In this article, we estimate the minimum integer r = r(n, k, d) such that each n‐vertex graph with is ‐linked, where is the family of simple graphs with k edges and minimum degree at least . © 2008 Wiley Periodicals, Inc. J Graph Theory 58: 14–26, 2008 相似文献
983.
Polymer materials used in railway field are degraded by environmental factors such as thermal, oxidative, photolytic, hydrolytic, and mechanical. The expected service life of the polymer materials used in railway field is approximately 20 years that is relatively long period for the polymer material; therefore, respective degradation factors should be well considered. Some of the degradation conditions indicate similar mechanism. The oxidative reaction was seen in every degradation conditions under air atmosphere. The hydrolytic reaction was mainly observed in chemical and biological degradations. The degradation behavior of the polymer material was analyzed by various methods. FTIR, thermal analysis (TG, DSC), and molecular weight determination were mainly applied for its purpose. However, the degradation mechanism of practical products made of polymer material was insufficiently studied and the exchange criteria of the products depended on the visual inspection without the suitable degradation analysis not only in the railway field but also in other commercial and industrial fields. In addition, most of the methods to analyze degradation of polymer material are performed on the standard specimen forms. For the installed product, some kinds of damage are generated through the sample collection process; therefore, the damaged products have to be exchanged for brand new ones or repaired totally to be used for more period. Moreover, it is hard to suspend the railway service for the degradation analysis of polymer products. From these backgrounds, the prospect of degradation analysis related to polymer materials used in railway field was proposed. 相似文献
984.
Polyelectrolytes are widely used in capillary electrophoresis as coating agents of silica capillaries to prevent adsorption phenomena and improve the repeatability of peptide and protein analysis. A systematic study of the coating experimental conditions has been carried out to optimize coating stability and performance. The main experimental parameters studied were the type and concentration of polyelectrolytes used in several monolayer and multilayer coatings, the ionic strength of coating and stabilizing solutions, and the procedures used for coating and capillary storage. Electroosmotic flow magnitude, direction and repeatability were used to monitor coating stability. Coating ability to limit adsorption was investigated by monitoring variations of migration times, time-corrected peak areas and separation efficiency of test peptides. Capillary-to-capillary and batch-to-batch reproducibility was also studied. In addition, the separation performance of polyelectrolyte coatings were compared to those obtained with bare silica capillaries. 相似文献
985.
Ramon Carbó-Dorca 《Journal of mathematical chemistry》2008,44(1):228-234
An Aufbau recursive algorithm, leading to the construction of molecular Quantum similarity matrices (QSM) with positive definite
structure is described. As a consequence, Molecular Quantum Similarity measures optimization has to be restricted by a recursive
constraint, related to the Euclidian norm of the QSM column elements in Quantum Object density tag reciprocal space. 相似文献
986.
Xiao-Sen Li Yu Zhang Gang Li Zhao-Yang Chen Ke-Feng Yan Qing-Ping Li 《The Journal of chemical thermodynamics》2008,40(9):1464-1474
We employ two thermodynamic approaches, based on the equal fugacities and the equal activities, to predict the gas hydrate equilibrium dissociation conditions in the porous media. The predictions are made for the hydrate systems, CH4/H2O, C2H6/H2O, C3H8/H2O, CO2/H2O, CH4/CO2/H2O, C3H8/CH4/C2H6/H2O, and CH4/CH3OH/H2O. For the non-hydrate phase, we used the Trebble–Bishnoi equation in the fugacity approach and the Soave–Redlich–Kwong equation in the activity approach. For the hydrate phase, the van der Waals–Platteeuw model incorporated with the capillary model of Llamedo et al. [M. Llamedo, R. Anderson, B. Tohidi, Am. Mineral. 89 (2004) 1264–1270] was used in the two approaches. The predictions are found to be in satisfactory to good agreement with the experimental data. The predictive ability of the fugacity approach is better than that of the activity approach. 相似文献
987.
Ali Azmy Shunran Li Giasemi K. Angeli Claire Welton Parth Raval Min Li Nourdine Zibouche Lukasz Wojtas G. N. Manjunatha Reddy Peijun Guo Pantelis N. Trikalitis Ioannis Spanopoulos 《Angewandte Chemie (International ed. in English)》2023,62(12):e202218429
In this work we report a strategy for generating porosity in hybrid metal halide materials using molecular cages that serve as both structure-directing agents and counter-cations. Reaction of the [2.2.2] cryptand (DHS) linker with PbII in acidic media gave rise to the first porous and water-stable 2D metal halide semiconductor (DHS)2Pb5Br14. The corresponding material is stable in water for a year, while gas and vapor-sorption studies revealed that it can selectively and reversibly adsorb H2O and D2O at room temperature (RT). Solid-state NMR measurements and DFT calculations verified the incorporation of H2O and D2O in the organic linker cavities and shed light on their molecular configuration. In addition to porosity, the material exhibits broad light emission centered at 617 nm with a full width at half-maximum (FWHM) of 284 nm (0.96 eV). The recorded water stability is unparalleled for hybrid metal halide and perovskite materials, while the generation of porosity opens new pathways towards unexplored applications (e.g. solid-state batteries) for this class of hybrid semiconductors. 相似文献
988.
Di Liu Jiyan Pei Prof. Xu Zhang Xiao-Wen Gu Prof. Hui-Min Wen Prof. Banglin Chen Prof. Guodong Qian Prof. Bin Li 《Angewandte Chemie (International ed. in English)》2023,62(12):e202218590
Developing porous materials for C3H6/C3H8 separation faces the challenge of merging excellent separation performance with high stability and easy scalability of synthesis. Herein, we report a robust Hofmann clathrate material (ZJU-75a), featuring high-density strong binding sites to achieve all the above requirements. ZJU-75a adsorbs large amount of C3H6 with a record high storage density of 0.818 g mL−1, and concurrently shows high C3H6/C3H8 selectivity (54.2) at 296 K and 1 bar. Single-crystal structure analysis unveil that the high-density binding sites in ZJU-75a not only provide much stronger interactions with C3H6 but also enable the dense packing of C3H6. Breakthrough experiments on gas mixtures afford both high separation factor of 14.7 and large C3H6 uptake (2.79 mmol g−1). This material is highly stable and can be easily produced at kilogram-scale using a green synthesis method, making it as a benchmark material to address major challenges for industrial C3H6/C3H8 separation. 相似文献
989.
Lu Wang Wenjuan Xue Hejin Zhu Xiangyu Guo Hongliang Huang Prof. Chongli Zhong 《Angewandte Chemie (International ed. in English)》2023,62(11):e202218596
The separation of isomeric C4 paraffins is an important task in the petrochemical industry, while current adsorbents undergo a trade-off relationship between selectivity and adsorption capacity. In this work, the pore aperture of a cage-like Zn-bzc (bzc=pyrazole-4-carboxylic acid) is tuned by the stepwise installation methyl groups on its narrow aperture to achieve both molecular-sieving separation and high n-C4H10 uptake. Notably, the resulting Zn-bzc-2CH3 (bzc-2CH3=3,5-dimethylpyrazole-4-carboxylic acid) can sensitively capture n-C4H10 and exclude iso-C4H10, affording molecular-sieving for n-C4H10/iso-C4H10 separation and high n-C4H10 adsorption capacity (54.3 cm3 g−1). Breakthrough tests prove n-C4H10/iso-C4H10 can be efficiently separated and high-purity iso-C4H10 (99.99 %) can be collected. Importantly, the hydrophobic microenvironment created by the introduced methyl groups greatly improves the stability of Zn-bzc and significantly eliminates the negative effect of water vapor on gas separation under humid conditions, indicating Zn-bzc-2CH3 is a new benchmark adsorbent for n-C4H10/iso-C4H10 separation. 相似文献
990.
Cong Yu Zhengdong Guo Lifeng Yang Jiyu Cui Sen Chen Yawen Bo Xian Suo Qihan Gong Shang Zhang Prof. Xili Cui Shengbao He Prof. Huabin Xing 《Angewandte Chemie (International ed. in English)》2023,62(16):e202218027
Adsorptive separation is an energy-efficient alternative, but its advancement has been hindered by the challenge of industrially potential adsorbents development. Herein, a novel ultra-microporous metal-organic framework ZU-901 is designed that satisfies the basic criteria raised by ethylene/ethane (C2H4/C2H6) pressure swing adsorption (PSA). ZU-901 exhibits an “S” shaped C2H4 curve with high sorbent selection parameter (65) and could be mildly regenerated. Through green aqueous-phase synthesis, ZU-901 is easily scalable with 99 % yield, and it is stable in water, acid, basic solutions and cycling breakthrough experiments. Polymer-grade C2H4 (99.51 %) could be obtained via a simulating two-bed PSA process, and the corresponding energy consumption is only 1/10 of that of simulating cryogenic distillation. Our work has demonstrated the great potential of pore engineering in designing porous materials with desired adsorption and desorption behavior to implement an efficient PSA process. 相似文献