| 1281. |
- Zhang, Shidong, et al.
(författare)
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Simple and complex polymer electrolyte fuel cell stack models : A comparison
- 2018. - 13
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Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-6737 .- 1938-5862. - 9781607685395 ; 86, s. 287-300
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Konferensbidrag (refereegranskat)abstract
- In this paper, two distinct polymer electrolyte fuel cell stack models are constructed: a detailed numerical model (DNM) employing a fine-scale computational mesh and a coarse-mesh approach based on a distributed resistance analogy (DRA) where diffusion terms in the transport equations are replaced by rate terms. Both methods are applied to a 5-cell, high-temperature polymer electrolyte fuel cell stack with an active area of 200 cm2 per cell. The polarization curve and local current density distributions from both the DRA and DNM are compared with experimental data, finding good agreement. Temperature, pressure, Nernst potential, and species distributions are also exhibited. The DNM displays details of fine-scale local extrema not captured by the DRA; however, the latter requires orders of magnitude less computer processor power and memory for execution. Both methods provide much finer-scale results than present experimental techniques.
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| 1282. |
- Zhang, Shuo, et al.
(författare)
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Thermodynamics and crystallization of a theophylline-salicylic acid cocrystal
- 2015
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Ingår i: CrystEngComm. - : Royal Society of Chemistry (RSC). - 1466-8033. ; 17:22, s. 4125-4135
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Tidskriftsartikel (refereegranskat)abstract
- A 1: 1 theophylline-salicylic acid cocrystal has been successfully prepared by slurry conversion crystallization in a 1 : 1 molar ratio slurry of theophylline and salicylic acid in chloroform. The cocrystal powder was analysed by XRD and DSC, and the cocrystal structure was determined by single crystal XRD. The cocrystal melts at 188.5 degrees C, which is between the melting points of the pure cocrystal components. Microscopy and SEM images have been taken for the cocrystals prepared by slow evaporation from ethanol, ethyl acetate, or acetonitrile. The cocrystal dissolves congruently in chloroform and the solubility is determined. Based on the solubility data for the cocrystal and the pure components, the Gibbs free energy of cocrystal formation is calculated to be -4.92 kJ mol(-1) at 30 degrees C. The cocrystal dissolves incongruently in methanol, ethanol, and acetonitrile. The ternary phase diagram of the cocrystal in acetonitrile has been determined and compared with those of theophylline-oxalic acid and theophylline-glutaric acid cocrystal systems. By proper operation of the process in the phase diagram, the theophylline-salicylic acid cocrystal can be produced by slurry conversion crystallization in acetonitrile.
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| 1283. |
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| 1284. |
- Zhang, Teng, et al.
(författare)
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Conclusively Addressing the CoPc Electronic Structure : A Joint Gas-Phase and Solid-State Photoemission and Absorption Spectroscopy Study
- 2017
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 121:47, s. 26372-26378
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Tidskriftsartikel (refereegranskat)abstract
- The occupied and empty densities of states of cobalt phthalocyanine (CoPc) were investigated by photoelectron and X-ray absorption spectroscopies in the gas phase and in thin films deposited on a Au(111) surface. The comparison between the gas-phase results and density functional theory single-molecule simulations confirmed that the CoPc ground state is correctly described by the (2)A(1g) electronic configuration. Moreover, photon-energy-dependent valence photoemission spectra of both the gas phase and thin film confirmed the atomic character of the highest occupied molecular orbital as being derived from the organic ligand, with dominant contributions from the carbon atoms. Multiplet ligand-field theory was employed to simulate the Co L-edge X-ray absorption spectroscopy results.
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| 1285. |
- Zhang, Teng, 1988-, et al.
(författare)
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Electronic structure modifications induced by increased molecular complexity : from triphenylamine to m-MTDATA
- 2019
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : ROYAL SOC CHEMISTRY. - 1463-9076 .- 1463-9084. ; 21:32, s. 17959-17970
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Tidskriftsartikel (refereegranskat)abstract
- The starburst pi-conjugated molecule 4,4 ',4 ''-tris(N-3-methylphenyl-N-phenyl-amino)triphenylamine (C57H48N4, m-MTDATA), based on triphenylamine (TPA) building blocks, is widely used in optoelectronic devices due to its good electron-donor characteristics. The electronic structure of m-MTDATA was investigated for the first time in the gas phase by means of PhotoElectron Spectroscopy (PES) and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy. The combination of Density Functional Theory (DFT) calculations with the experimental spectra provides a comprehensive description of the molecular electronic structure. Moreover, by comparing the results with previous TPA measurements, we could shed light on how the electronic structure evolves when the molecular size is increased. We found that the C 1s photoelectron spectra of m-MTDATA and TPA are similar, due to the balance of the counter-acting effects of the electronegativity of the N atoms and the delocalization of the amine lone-pair electrons. In contrast, the increased number of N atoms (i.e. N lone pairs) in m-MTDATA determines a three-peak feature in the outermost valence binding energy region with strong contributions by the N 2p(z) orbitals. We also obtained a decrease of the HOMO-LUMO gap for m-MTDATA, which points to improved electron donating properties of m-MTDATA with respect to TPA.
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| 1286. |
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| 1287. |
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| 1288. |
- Zhang, XL, et al.
(författare)
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CUTseq is a versatile method for preparing multiplexed DNA sequencing libraries from low-input samples
- 2019
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Ingår i: Nature communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 10:1, s. 4732-
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Tidskriftsartikel (refereegranskat)abstract
- Current multiplexing strategies for massively parallel sequencing of genomic DNA mainly rely on library indexing in the final steps of library preparation. This procedure is costly and time-consuming, because a library must be generated separately for each sample. Furthermore, library preparation is challenging in the case of fixed samples, such as DNA extracted from formalin-fixed paraffin-embedded (FFPE) tissues. Here we describe CUTseq, a method that uses restriction enzymes and in vitro transcription to barcode and amplify genomic DNA prior to library construction. We thoroughly assess the sensitivity and reproducibility of CUTseq in both cell lines and FFPE samples, and demonstrate an application of CUTseq for multi-region DNA copy number profiling within single FFPE tumor sections, to assess intratumor genetic heterogeneity at high spatial resolution. In conclusion, CUTseq is a versatile and cost-effective method for library preparation for reduced representation genome sequencing, which can find numerous applications in research and diagnostics.
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| 1289. |
- Zhang, X. G., et al.
(författare)
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The Study on Cracking Strength of AIJs to Release the Early-Age Stress of Mass Concrete
- 2015
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Ingår i: Advances in Materials Science and Engineering. - : Hindawi Limited. - 1687-8442 .- 1687-8434. ; 2015
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Tidskriftsartikel (refereegranskat)abstract
- This paper aims to theoretically and numerically assess the effect of setting artificial-induced joints (AIJs) during construction period of amass concrete structure to release the early-stage thermal stress. With respect to the coupling influences of various factors such as size and boundary of AIJs, an analytical model for its cracking strength on the setting section of mass concrete is proposed based on double-parameter fracture theory. A kind of hyper-finite element analysis (FEA) for many array AIJs in simplified plane pate is also presented by using bilinear cohesive force distribution. The results from the present model and numerical simulation were compared to those of experimental data to prove the efficiency and accuracy of the analytical model and FEA. The model presented in this study for the cracking strength of AIJs provides a simple useful tool to accurately evaluate how many early stress AIJs reduced. The theoretical solution and FEA results could also be significantly contributed to find the "just" and "perfect" release of the temperature stress and to improve the design level of AIJs in mass concrete structure.
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| 1290. |
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