71 research outputs found
Synthesis of Nano/Micro Scale ZSM-5 from Kaolin and Its Catalytic Performance
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Nano/micro scale ZSM-5 zeolites were synthesized by using natural kaolin as raw material. The effect of particle size on the catalytic performance of ZSM-5 zeolite for the methanol to olefins conversion was evaluated in a fixed-bed reactor. The results indicated the crystal size had a significant effect on the catalytic stability and the products distribution. ZSM-5 with nanosize showed better tolerance to coke formation, longer catalytic lifetime, and higher selectivity to propylene. The selectivity to propylene on nanosized ZSM-5 was on average 4.5% higher than on the submicron sample and 10% higher than on microsized ZSM-5. After the reaction was conducted for 20 h the ZSM-5 catalyst synthesized from kaolin showed longer lifetime and higher propylene selectivity than the sample synthesized with chemical materials The reason can be explained by the occurence of such elements as Fe, P, and especially Ti.</p
Preparation and Characterization of Poly(methyl methacrylate)/Reactive Montmorillonite Nanocomposites
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The poly(methyl methacrylate) (PMMA)/reactive montmorillonite nanocomposites were prepared by emulsion polymerization. The double bonds were introduced to both the surfaces and interlayers of the montmorillonites to obtain the reactive montmorillonites. The structure of the nanocomposites measured by wide angle X-ray diffraction (WAXD) indicated that the montmorillonites were exfoliated. The average molecular weight of the nanocomposites revealed by gel permeation chromatography (GPC) was larger than that of pure PMMA. The results of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) indicated that the thermal properties of the nanocomposites were enhanced and could be affected by the amount of the reactive montmorillonites. In addition, the tensile properties of the nanocomposites measured by an Instron testing machine improved and the nanocomposites including 3 wt% reactive montmorillonites showed the best tensile strength. The Young's modulus increased with the addition of the reactive montmorillonites. The aging properties of the nanocomposites had an improvement compared with pure PMMA. The optical properties assessed by UV-Visible spectroscopy revealed that the transmittance decreased as the amount of the reactive montmorillonites increased. Finally, the mechanism to prepare PMMA/reactive montmorillonite nanocomposites was proposed. (C) 2015 Society of Plastics Engineers</p
J. Mater. Chem. A
No full textNano-sized ZSM-5 aggregates have been rapidly synthesized from leached metakaolin by solid-like state conversion. The influence of synthesis conditions such as TPA(+)/SiO2, NaOH/SiO2 and SiO2/Al2O3 molar ratios on the final products was investigated. The properties of nano-sized ZSM-5 aggregates were characterized by XRD, SEM, HRTEM, Si-29 and Al-27 MAS NMR, NH3-TPD, TG, N-2 adsorption-desorption and particle size analysis. The results clearly showed that nano-sized ZSM-5 aggregates could be obtained within 2 h via solid-like state conversion. SEM revealed that the obtained ZSM-5 aggregates were irregular spheres that consisted of nano-sized crystallites with 30-50 nm. The crystallization process indicated that the size of flaky raw materials gradually decreased and formed nano-sized particles as time prolonged. Therefore, the transformation mechanism followed the solution mediated mechanism, though only a little water was contained in the system. Compared with the conventional hydrothermal route, the solid-like state conversion not only significantly shortened the crystallization time, but also totally avoided the emission of waste liquids. In addition, for the methanol dehydration reaction, the nano-sized ZSM-5 aggregates obtained by this method showed much better catalytic performance, C2-C4 olefin selectivity and longer lifetime to endure coke deposition than the sample obtained by the hydrothermal route.Nano-sized ZSM-5 aggregates have been rapidly synthesized from leached metakaolin by solid-like state conversion. The influence of synthesis conditions such as TPA(+)/SiO2, NaOH/SiO2 and SiO2/Al2O3 molar ratios on the final products was investigated. The properties of nano-sized ZSM-5 aggregates were characterized by XRD, SEM, HRTEM, Si-29 and Al-27 MAS NMR, NH3-TPD, TG, N-2 adsorption-desorption and particle size analysis. The results clearly showed that nano-sized ZSM-5 aggregates could be obtained within 2 h via solid-like state conversion. SEM revealed that the obtained ZSM-5 aggregates were irregular spheres that consisted of nano-sized crystallites with 30-50 nm. The crystallization process indicated that the size of flaky raw materials gradually decreased and formed nano-sized particles as time prolonged. Therefore, the transformation mechanism followed the solution mediated mechanism, though only a little water was contained in the system. Compared with the conventional hydrothermal route, the solid-like state conversion not only significantly shortened the crystallization time, but also totally avoided the emission of waste liquids. In addition, for the methanol dehydration reaction, the nano-sized ZSM-5 aggregates obtained by this method showed much better catalytic performance, C2-C4 olefin selectivity and longer lifetime to endure coke deposition than the sample obtained by the hydrothermal route
Effect of Reactive Nanoclays on Performances of PMMA/Reactive Nanoclay Nanocomposites
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PMMA/reactive nanoclay nanocomposites were prepared by emulsion polymerization using two different reactive nanoclays. X-ray diffraction (XRD) and thermogravimetric analysis (TGA) results confirmed that the reactive nanoclays, kaolinite and montmorillonite, were obtained by the silylation reaction and the double bonds were grafted onto the edges and surfaces of the nanoclays. The presence of reactive nanoclays could increase the average molecular weights, the glass transition temperatures (T-g) and improve the thermal properties of nanocomposite. The tensile properties, Young's modulus, and the aging properties of the nanocomposite films were also enhanced while the light transmittance decreased. Furthermore, the nanocomposites with the reactive kaolinite presented better performances than that with the reactive montmorillonite. Finally, the action mechanism of the reactive nanoclays to the performances of PMMA/reactive nanoclay nanocomposites was proposed.</p
Shaping the Securities Industry Spatial Pattern by Institutional Arrangements in China: An Analysis Based on Headquarters Location of Securities Companies
No full textAs a crucial capital intermediary, the securities industry has gradually become an integral part of financial markets and plays a vital role in shaping financial center cities. Although the securities industry of China has a relatively short history of development, its spatial structure has undergone a substantial transformation. Nevertheless, the existing research has yet to thoroughly investigate the spatial evolution of the securities industry, especially in terms of how institutional arrangements impact its spatial organization. This study systematically analyzes the establishment, exit, and headquarters relocation of securities companies across China from 1992 to 2022 and investigates the role of institutional arrangements in shaping the spatial configuration of the securities sector. The main findings reveal three critical insights. (1) The spatial distribution of securities company headquarters in China has evolved from a dispersed to a highly concentrated layout. During the formative years of the industry, most provincial capital cities in China established local securities companies, resulting in a relatively scattered distribution of headquarters across the country. However, as the industry expanded and matured, securities companies in smaller cities gradually relocated or shut down, and new establishments or relocations of securities companies became predominantly concentrated in Beijing, Shanghai, and Shenzhen, causing these three cities to gradually become the central hubs of the industry. (2) Institutional arrangements concentrated on key securities resources in a few selected cities, forming the foundational spatial structure of China's securities industry. From the early days of the industry, central government policies have played a decisive role in shaping the spatial organization of the securities sector. Shanghai and Shenzhen were designated the only cities legally permitted to host stock exchanges, granting them a unique infrastructural advantage that naturally fostered the growth and concentration of the securities industry. Beijing, the location of the China Securities Regulatory Commission, has been pivotal in shaping the spatial structure of the industry. The centralized regulatory and financial infrastructure, combined with preferential policies for key cities, has created a distinct pattern of spatial concentration, with Beijing, Shanghai, and Shenzhen forming the core centers of China's securities industry. (3) Institutional factors consistently influence the spatial dynamics of the securities industry across its developmental stages. From the early government-directed capital deployment to establish local securities companies to state-owned enterprises' involvement in managing high-risk securities companies during industry cleanups, institutional factors have been crucial in shaping the evolution of the industry's spatial distribution. Recently, regulatory interventions for foreign-invested securities firms, including policy-driven decisions regarding the location of their headquarters, have played a significant role in consolidating the industry within major financial hubs. These interventions, including preferential policies, mergers and acquisitions, and support for foreign investments, significantly altered the distribution of securities companies across China. The evolving regulatory landscape, along with China's unique institutional characteristics, has ensured that the country's securities industry remains highly centralized, with significant financial resources concentrated in key cities. This study theoretically addresses the gap in Western-focused perspectives by highlighting how institutional factors shape the spatial structure of China's securities industry. While the clustering of securities firms in financial centers may align with market trends, China's distinctive institutional framework has acted as a powerful force driving the spatial evolution of the industry. Thus, this study provides valuable insights into the dynamic spatial patterns of the financial sector within China's regulatory environment, contributing essential perspectives on the development of financial center cities and deepening our understanding of the mechanisms shaping financial center cities under China's unique institutional conditions
EE-LLM: Large-Scale Training and Inference of Early-Exit Large Language Models with 3D Parallelism
No full textWe present EE-LLM, a framework for large-scale training and inference of
early-exit large language models (LLMs). While recent works have shown
preliminary evidence for the efficacy of early exiting in accelerating LLM
inference, EE-LLM makes a foundational step towards scaling up early-exit LLMs
by supporting their training and inference with massive 3D parallelism. Built
upon Megatron-LM, EE-LLM implements a variety of algorithmic innovations and
performance optimizations tailored to early exiting, including a lightweight
method that facilitates backpropagation for the early-exit training objective
with pipeline parallelism, techniques of leveraging idle resources in the
original pipeline schedule for computation related to early-exit layers, and
two approaches of early-exit inference that are compatible with KV caching for
autoregressive generation. Our analytical and empirical study shows that EE-LLM
achieves great training efficiency with negligible computational overhead
compared to standard LLM training, as well as outstanding inference speedup
without compromising output quality. To facilitate further research and
adoption, we release EE-LLM at https://github.com/pan-x-c/EE-LLM.Comment: ICML 2024 camera-ready versio
Pan-cancer analysis identifies olfactory receptor family 7 subfamily A member 5 as a potential biomarker for glioma
No full textBackground Human olfactory receptors (ORs) account for approximately 60% of all human G protein-coupled receptors. The functions of ORs extend beyond olfactory perception and have garnered significant attention in tumor biology. However, a comprehensive pan-cancer analysis of ORs in human cancers is lacking. Methods Using data from public databases, such as HPA, TCGA, GEO, GTEx, TIMER2, TISDB, UALCAN, GEPIA2, and GSCA, this study investigated the role of olfactory receptor family 7 subfamily A member 5 (OR7A5) in various cancers. Functional analysis of OR7A5 in LGG and GBM was performed using the CGGA database. Molecular and cellular experiments were performed to validate the expression and biological function of OR7A5 in gliomas. Results The results revealed heightened OR7A5 expression in certain tumors, correlating with the expression levels of immune checkpoints and immune infiltration. In patients with gliomas, the expression levels of OR7A5 were closely associated with adverse prognosis, 1p/19p co-deletion status, and wild-type IDH status. Finally, in vitro experiments confirmed the inhibitory effect of OR7A5 knockdown on the proliferative capacity of glioma cells and on the expression levels of proteins related to lipid metabolism. Conclusion This study establishes OR7A5 as a novel biomarker, potentially offering a novel therapeutic target for gliomas
Submicron ZSM-5 synthesized by green and fast route
No full textSubmicron ZSM-5 was fast synthesized from coal series kaolin without organic templates with the assistance of crystal seeds. The crystallization conditions (seeds amount and SiO2/Al2O3 molar ratio), the crystallization processes and the mechanism were investigated. The results clearly indicated that the crystallization time could be shortened to 6 h by adding crystal seeds, and the crystal size was effectively reduced to submicron grade. Crystallization process demonstrated that hexa-coordinated Al of leached metakaolin was totally converted to tetra-coordinated Al, involved in the formation of ZSM-5 skeleton with Si species in the form of Si (1Al) and Si (2Al). The crystallization process of sub-micron ZSM-5 synthesized from coal series kaolin also abode by the solution-mediated transport mechanism. (C) 2017 Elsevier B. V. All rights reserved.</p
Determination and application of the reaction between REOCl (RE = Y, Gd and Sm) and H2O
No full textThe reaction between rare earth oxychloride (REOCl) and water was investigated. X-ray diffractometer, volumetric titrations, FTIR spectrograph and scanning electron microscope were used to determine the reaction process and the reaction products. It was found that the reaction could be concluded as follows: 5REOCl(s) + 5H(2)O(l) = 2RE(2)(OH)(5)Cl(s) + RE3+(aq) + 3Cl(-)(aq). Based on this reaction, a new method for determining the purity of anhydrous rare earth chloride was proposed. Compared with the conventional method, the maximum absolute error decreased from 22 to < 1% and the maximum relative error decreased from 111 to < 4% under the experimental conditions.
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