204,249 research outputs found
Continuum free-energy formulation for a class of lattice Boltzmann multiphase models
No full textWe characterize theoretically the free energy of the so called 'Shan-Chen' model for non ideal fluid flows
INNOVATIVE PILLAR[6]ARENE-BASED STATIONARY PHASES FOR HIGH-RESOLUTION GAS CHROMATOGRAPHIC ANALYSES
No full textIn this work, the synthesis, fabrication, and characterization of new stationary phases based on pillar[6]arene derivative modified by long alkyl chains (P6A-C10) for high-resolution gas chromatographic (GC) analyses are reported. Pillar[n]arenes are a new class of macrocyclic hosts that can accommodate specific guests due to their highly symmetrical and rigid pillar architectures with π-electron rich cavities. Quantum chemistry calculations have been performed, showing a difference in non-covalent interactions with the P6A-C10 pillar framework, which leads to specific selectivity for aromatic compounds. The GC columns prepared with these innovative stationary phases exhibited a medium polarity, and good reproducibility for run-to-run, day-to-day, and column-to-column analyses [1], demonstrating great potential as new stationary phases in separation science. Furthermore, peculiar advantages are achieved if compared with the commercial HP-5, HP-35, DB-17, and PEG-20M columns, showing unmatched resolving capabilities toward chloroaniline, bromoaniline, iodoaniline, toluidine, and xylene isomers [2].
References:
1. Sun, T., Chen, R., Huang, Q., Ba, M., Cai, Z., Hu, S., Liu, X., Nardiello, D., & Quinto, M., ACS Appl. Mater. Interfaces 14 (2022) 56132−56142.
2. Sun, T., Chen, R., Huang, Q., Ba, M., Cai, Z., Chen, H., Qi, Y., Chen, H., Liu, X., Nardiello, D., & Quinto, M., Anal. Chim. Acta 1251 (2023) 340979
Colloquium: Role of the H theorem in lattice Boltzmann hydrodynamic simulations
No full textIn the last decade, minimal kinetic models, and primarily the lattice Boltzmann equation, have met with significant success in the simulation of complex hydrodynamic phenomena, ranging from slow flows in grossly irregular geometries to fully developed turbulence, to flows with dynamic phase transitions. Besides their practical value as efficient computational tools for the dynamics of complex systems, these minimal models may also represent a new conceptual paradigm in modern computational statistical mechanics: instead of proceeding bottom-up from the underlying microdynamic systems, these minimal kinetic models are built top-down starting from the macroscopic target equations. This procedure can provide dramatic advantages, provided the essential physics is not lost along the way. For dissipative systems, one essential requirement is compliance with the second law of thermodynamics. In this Colloquium, the authors present a chronological survey of the main ideas behind the lattice Boltzmann method, with special focus on the role played by the H theorem in enforcing compliance of the method with macroscopic evolutionary constraints (the second law) as well as in serving as a numerically stable computational tool for fluid flows and other dissipative systems out of equilibrium
Transforming Guanxi networks: Taiwanese entrepreneurs’ production networks in Thailand and Vietnam
No full textSaussurea bhutanensis Y. S. Chen 2014, sp. nov.
No full text5. Saussurea bhutanensis Y. S. Chen, sp. nov. (Fig. 5, 9A & 9B) Type:— CHINA. Xizang: Yadong, Pagri, mountains between border of China and Bhutan, 27°37’ N, 89°07’ E, sandy meadows, 4870 m, 25 August 2013, FLPH Tibet Exped.13-2131 (holotype PE; isotypes PE). Herbs 1–4 cm tall, perennial, stemless, caespitose. Caudex 2–3 cm in diam., usually much branched. Rosette leaves sessile, linear, 10–25 × 1–1.5 mm, abaxially greyish white and densely tomentose-sericeous, adaxially green, shiny, and glabrous, base enlarged, sheathing, and white villous, margin entire and revolute, apex acute. Uppermost leaves merging into phyllaries, supporting capitula. Capitula solitary, in center of leaf rosette or terminal on stem, sessile, concealed by villous hairs. Involucre campanulate, 1–1.6 cm in diam. Phyllaries in ca. 6 rows, apex acuminate to caudate; outer phyllaries narrowly ovate-triangular, 14–16 × 3–4 mm, basal part dark green, apical part greenish, sparsely villous, and reflexed; middle and inner phyllaries narrowly ovate-triangular to narrowly elliptic-linear, 11–13 × ca. 2 mm, basal part pale yellow, apical part blackish purple, villous, and reflexed. Receptacle bristles very few, 1–2 mm long. Corolla purplish, 1.3–1.5 cm long, tube 7–8 mm long, limb 6.5–8 mm long, lobes 3.5–4 mm long. Achene dark brown, conic, ca. 3 mm long, glabrous. Pappus in 2 rows; outer bristles white, 2–3 mm long, scabrid; inner bristles pale brown, 9–10 mm long, plumose. Distribution and habitat: — Saussurea bhutanensis occurs in northern Bhutan and adjacent border of Yadong, Xizang, China. It grows on alpine sandy meadows (including Saussurea, Aster, Primula, Arenaria, Gentiana, Swertia, Cyananthus, Saxifraga and Delphinium species), alpine scree or limestones at altitudes of 4500–4900 m. Phenology:—Flowering and fruiting from August to October. Etymology: —The specific epithet is derived from its main distribution area, Bhutan. Additional specimens examined (paratypes): — BHUTAN. [Bumthang district]: Tolegang, Tsampa, steep open hillside, 4720 m, 2 October 1949, F . Ludlow, G. Sherriff & J. H. Hicks 19784 (BM, E); [Wangdi district]: Wangdue-Phodrang, Thampe La, limestone, 27°43’ N, 90°18’ E, 4500–4600 m, 28 September 2000, G. & S . Miehe 00-421-01 (E). Discussion:— Saussurea bhutanensis belongs to S. subgen. Saussurea sect. Lagurostemon on account of its leaf blade being linear, entire, grasslike, and the capitula solitary, 1–1.6 cm in diameter. Grierson & Springate (2001) reported one specimen from Bhutan (F. Ludlow, G. Sherriff & J. H. Hicks 19784) that is related to Saussurea columnaris Handel-Mazzetti (1937: 652), but they noted this specimen is different from the typical S. columnaris in its receptacle naked, achene glandular-stipitate above and habit usually stemless. This kind of specimen was also found from the Tibetean border with Bhutan (FLPH Tibet Exped.13-2131) by the present author in 2013. But the present author found its receptacle is not entirely naked but with few short bristles 1–2 mm long, achenes glabrous, leaves 1–2.5 cm long, phyllaries usually narrower and apex acuminate, capitula concealed by dense villous hairs. Typical specimens of S. columnaris from Yunnan are different in the receptacle bristles ca. 7 mm long and plants usually stemmed, leaves 2–7 cm long, phyllaries usually broader and apex acute, capitula not concealed by villous hairs. Saussurea bhutanensis is also similar to S. durgae Jeffrey & Srivastava (1997: 235) in its caespitose habit and linear grassy leaves, but S. bhutanensis differs in its leaves adaxially green, shiny, and glabrous, capitula concealed by villous hairs, and corolla purplish, whereas S. durgae differs in its leaves densely clothed with greyish white wooly hairs on both surfaces, capitula not concealed by villous hairs, and corolla pink. A comparison of S. bhutanensis, S. columnaris and S. durgae is given in Table 5.Published as part of Chen, You-Sheng, 2014, Six new species of Saussurea (Asteraceae) from eastern Himalaya, pp. 191-206 in Phytotaxa 177 (4) on page 199, DOI: 10.11646/phytotaxa.177.4.1, http://zenodo.org/record/514474
A molecular dynamics study of N-A-S-H gel with various Si/Al ratios
No full textThe understanding of sodium aluminosilicate hydrate (N-A-S-H) gel is still limited due to its complex and amorphous structure. Recently, molecular dynamics simulation has provided a unique opportunity to better understand the structure of N-A-S-H gel from nanoscale. In this work, the N-A-S-H gel structure was obtained by simulating the polymerization of Si and Al monomers by molecular dynamics. The simulated polymerization process is in good agreement with the experimental results especially in terms of the reaction rate of Si and Al species. The atomic structural features of the N-A-S-H gel were analyzed in terms of bond length and bond angle information, simulated X-ray diffraction (XRD) and Qn distribution. A significant finding is the existence of pentacoordinate Al in all simulated N-A-S-H structures, indicating that pentacoordinate Al in geopolymer does not only come from raw material. Besides, the results show that a smaller Si/Al ratio led to a more crosslinked and compacted structure of N-A-S-H gel
Research on preparation and properties of C-S-H /PEG1000 phase change composite
No full textIn this paper, composite material C-S-H/PEG1000 was prepared by multi-scale porous material C-S-H as support and phase change material (PCM) PEG1000 by melt blending, so that it can reduce hydration heat of cementitious system utilizing the characteristics of releasing and storing energy of PCM. TEM, IR, DSC-Tg, BET, MIP and various other characterization methods were used to discuss the feasibility of C-S-H as carrier and investigate the morphology, pore structure and stability of the C-S-H/PEG1000 composite. The change of hydration heat and feathers of pore structure as while as its effect on compressive strength were also tested when the composite was added into the cementitious system. Study shows that the PEG1000 can be well embedded into the hollow inside space of C-S-H to form dense blocks in the form of physical adsorption, with good bonding state and thermal stability, which can decrease heat releasing rate and total heat of the hydration process in cementitious system. The early strength was pretty influenced with different addition of C-S-H/PEG1000, however, the later strength was improved
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