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  • Author or Editor: T. Zhang x
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The relationship between plant communities and elevation in the Guandi mountainous area was studied. Data from 89 sampling units, each of 10 m x 20 m size, taken along an elevation gradient were analyzed by TWINSPAN, DECORANA and diversity and evenness indices. The samples were clustered into 23 groups by TWINSPAN, representing 23 vegetation types. The composition and distribution of communities varied greatly along the altitude gradient, suggesting that community diversity is closely related to elevation in the Guandi Mountains. This is due to the change of temperature and water-conditions along the elevation gradient. Species heterogeneity and evenness were significantly correlated with elevation along the entire gradient, but showing first a trend of increases and then decreases, corresponding to the hypothesis of maximum diversity at medium elevation. Species richness varied greatly in the study area, and was not significantly correlated with elevation.

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The incorporation mechanism of Cs+ ions from CsNO3 into NH4Zr2(PO4)3 was studied on a mixture of CsNO3 and NH4Zr2(PO4)3 by powder X-ray diffraction analysis and by monitoring off-gases released from the mixture upon heating with a thermogravimetry analyzer connected to an infrared spectrometer. With increasing temperature, the decomposition of CsNO3 first started, followed by the conversion of NH4Zr2(PO4)3 to HZr2(PO4)3 with the release of NH3. At around 500°C, the Cs Zr2(PO4)3 phase started to appear as a result of the H+/Cs+ ion exchange. No Cs+ ion loss was observed at thermal treatment temperatures of 900°C and lower.

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The simultaneous DSC-FTIR was used for the observation of crystallization and melting of poly(vinylidene fluoride) (PVDF) and its blends with poly(methyl methacrylate) (PMMA) and poly(ethyl methacrylate) (PEMA). The isothermal crystallization was carried out under the condition of both α-form and γ-form crystallized competitively. The crystal growth rate of α -form and γ -form were evaluated from the absorbance changes at 795 cm-1 (α -form, CH2 rocking) and 810 cm-1 (γ -form, CH2 rocking) obtained by the DSC-FTIR. The crystal growth rate of γ -form decreased at the same crystallization temperature in the order of PVDF/syn-PMMA, PVDF/PEMA and PVDF/at-PMMA, which was corresponding to the order of interaction parameter. The mechanism of α -g transition of PVDF in the miscible blends with at-PMMA, syn-PMMA and PEMA was evaluated from the relationship between the decrease of α -form and the increase of γ -form. The critical crystallization temperature, at which the transformation from α -form to γ -form proceeded only in the solid state, shifted to higher temperature side in the order of interaction parameter.

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The miscibility of crystalline syndiotactic polystyrene (SPS)/non-crystalline atactic polystyrene (APS) blend was estimated by the crystallization dynamics method, which evaluated the nucleation rate, the crystal growth rate and the surface free energy parameter. The melting temperature depression suggested that SPS/APS blends were the miscible system but not in molecular level. The relationship between the blend content and the chemical potential difference evaluated at a constant crystal growth rate showed a good linear relationship. These facts suggested that SPS/APS blends contained the concentration fluctuation with the size between few nm to less than 80 nm.

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Thermal bridging caused by exposed concrete balcony slab is a major source of heat loss through energy efficient building envelopes. Moreover, thermal bridging can also create moisture management and indoor comfort challenges. Numerous investigations have been carried out to reduce heat transmittance through exterior building envelopes and minimize the energy use in buildings. The most effective way to minimize heat transmittance of exposed concrete balcony slabs is to thermally separate the exterior structure from the interior structure using thermal breaks. To enhance thermal separation, this paper investigates the effects of replacing high conductive materials such as reinforced concrete or structural steel with a multilayer composition of high-performance hybrid insulating systems. Reinforcing bars, such as fiber reinforced plastics (FRPs), having lower thermal conductivity than steel are used to connect interior to exterior and transfer loads. Numerical simulation tool THERM is used to study the effects of thermal breaks on energy performance of the concrete slab balcony joints. Simulation results indicate significant thermal performance improvement while high-performance hybrid insulating systems were used for exposed concrete balcony slab constructions, compared to traditional insulating systems used in similar constructions

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The mixing state of poly(vinylidene fluoride) (PVDF) and two amorphous polymers,poly(methyl methacrylate) (PMMA) and poly(isopropyl methacrylate) (PiPMA) were investigated from the viewpoint of crystallization dynamics using simultaneous DSC-FTIR method. The crystallization rate (R *) and the growth rate of trans-gauche-trans-gauche’ (TGTG’) conformation (Rc *) depended on both the blend content (ϕ) and the crystallization temperature for PVDF/PMMA. The temperature and ϕ dependency of R * and Rc * were almost the same for PVDF/PMMA. However, R * and Rc * depended scarcely on f for PVDF/PiPMA, and the temperature dependency of R * differed from that of Rc * for PVDF/PiPMA. These results showed that PVDF and PMMA were miscible on molecular level, and that PVDF/PiPMA was immiscible and the concentration fluctuation existed in the PVDF-rich phase.

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In this paper, organic phase change materials (PCM)/Ag nanoparticles composite materials were prepared and characterized for the first time. The effect of Ag nanoparticles on the thermal conductivity of PCM was investigated. 1-tetradecanol (TD) was selected as a PCM. A series of nano-Ag-TD composite materials in aqueous solution were in-situ synthesized and characterized by means of thermal conductivity evaluation method, TG-DSC, IR, XRD and TEM. The results showed that the thermal conductivity of the composite material was enhanced as the loading of Ag nanoparticles increased. The composite materials still had relatively large phase change enthalpy. Their phase change enthalpy could be correlated linearly with the loading of TD, but their phase change temperature was a little bite lower than that of pure TD. The thermal stability of the composite materials was close to that of pure TD. It appeared that there was no strong interaction between the Ag nanoparticles and the TD. Furthermore, the experiment results indicated that the Ag nanoparticles dispersed uniformly in the materials, occurred in the forms of pure metal.

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As one 3-D coordination polymer, lead formate was synthesized; calorimetric study and thermal analysis for this compound were performed. The low-temperature heat capacity of lead formate was measured by a precise automated adiabatic calorimeter over the temperature range from 80 to 380 K. No thermal anomaly or phase transition was observed in this temperature range. A four-step sequential thermal decomposition mechanism for the lead formate was found through the DSC and TG-DTG techniques at the temperature range from 500 to 635 K.

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Adsorption microcalorimetry has been employed to study the interaction of ethylene with the reduced and oxidized Pt-Ag/SiO2catalysts with different Ag contents to elucidate the modified effect of Ag towards the hydrocarbon processing on platinum catalysts. In addition, microcalorimetric adsorption of H2, O2, CO and FTIR of CO adsorption were conducted to investigate the influence of Ag on the surface structure of Pt catalyst. It is found from the microcalorimetric results of H2and O2adsorption that the addition of Ag to Pt/SiO2leads to the enrichment of Ag on the catalyst surface which decreases the size of Pt surface ensembles of Pt-Ag/SiO2catalysts. The microcalorimetry and FTIR of CO adsorption indicates that there still exist sites for linear and bridged CO adsorption on the surface of platinum catalysts simultaneously although Ag was incorporated into Pt/SiO2. The ethylene microcalorimetric results show that the decrease of ensemble size of Pt surface sites suppresses the formation of dissociative species (ethylidyne) upon the chemisorption of C2H4on Pt-Ag/SiO2. The differential heat vs. uptake plots for C2H4adsorption on the oxygen-preadsorbed Pt/SiO2and Pt-Ag/SiO2catalysts suggest that the incorporation of Ag to Pt/SiO2could decrease the ability for the oxidation of C2H4.

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