Liu Z.,Beijing Forestry UniversityBeijing |
Zhang Y.,Beijing Forestry UniversityBeijing |
Fa K.,Beijing Forestry UniversityBeijing |
Qin S.,Beijing Forestry UniversityBeijing |
She W.,Beijing Forestry UniversityBeijing
Catena | Year: 2017
Modifications of rainfall patterns are expected to accompany global climate changes. It has been suggested that in dry regions changes in soil carbon emission induced by precipitation will affect soil carbon storage and atmospheric CO2concentration. However, our understanding of the responses of soil carbon emission [often as soil respiration (RS)] to rainfall pulses is still limited regarding changes in soil respiration components [heterotrophic respiration (RH) and autotrophic respiration (RA)] and under different precipitation patterns in arid and semiarid ecosystems. To evaluate the variations in soil carbon emission in response to rainfall pulses, we measured RSand its components in situ before/after precipitation in the Mu Us Desert, China. Rates of RSand its components were significantly enhanced by rainfall pulses, but gradually reverted thereafter. Moreover, the magnitudes of diel hysteresis for RS, RH, and RAwith respect to soil temperature (TS) were modified by precipitation, and the effects of rainfall pulses on RSwere influenced by antecedent soil water availability. In addition, the ratio of respiration components was changed by individual precipitation events, with an increase in the amount of each rainfall pulse causing a decrease in the proportion of RHto RS. Our results indicate that rainfall pulses in desert ecosystems have a major impact on soil carbon emission via changes in the magnitude and ratio of respiration components. We accordingly suggest that greater carbon emission and alterations in respiration components may occur with more extreme precipitation in desert ecosystems. © 2017 Elsevier B.V.
Jiang D.,North University of China |
Jiang D.,Beijing Materials University |
Cui S.,Beijing Materials University |
Xu F.,Beijing Forestry UniversityBeijing |
Tuo T.,North University of China
Construction and Building Materials | Year: 2015
Abstract To make effective use of plant leaves as an environment-friendly heat-insulating building material, our research group has tested five poplar leaf modification methods to improve compatibility between leaf fibres and cement-based materials. The work involved testing water absorption of before and after modification of leaf fibres, the setting time and hydration heat of the fibre-cement paste, and analysed the mechanisms and effect of fibre modification methods on compatibility between fibres and cement-based materials. The results show that processing of fibres with surface coating and dipping methods improved compatibility between fibres and cement-based materials to some extent and in different aspects. Overall, the following three methods gave superior performance: pure acrylic polymer emulsion spraying, sodium silicate solution spraying and water dipping. © 2015 Elsevier Ltd.
Wang K.,Tsinghua University |
Ma L.,Tsinghua University |
Xu X.,Beijing Forestry UniversityBeijing |
Wen S.,Tsinghua University |
Zhang Y.,Tsinghua University
Langmuir | Year: 2015
Triboluminescence (TL) has gained increasing attention in the past two decades due to its potential for many applications such as an in situ damage sensor, X-ray source, spectroscopic probe, and optical switch. So far the mechanisms by which TL is excited are not well understood. We have investigated the TL emitted during the sliding contact between silica wafer and YSZ (yttria-stabilized zirconia) wafers in CO2 gas, ambient air, and vacuum. We discovered that the mean intensity of photons emitted in CO2 gas is nearly a hundred times stronger than that in air. TL induced in the sliding experiment is proposed to be due to a combination of chemical luminescence, impurities and vacancies luminescence. In addition, the intensity of the light emission of YSZ may be controlled by changing the concentration of CO2 gas. © 2015 American Chemical Society.
Xia C.,University of North Texas |
Wang L.,Beijing Forestry UniversityBeijing |
Dong Y.,Beijing Forestry UniversityBeijing |
Zhang S.,Beijing Forestry UniversityBeijing |
And 3 more authors.
RSC Advances | Year: 2015
Epoxidized soybean oil (ESO) is an environmentally friendly cross-linking agent derived from soybean, having multiple epoxy groups in its molecules. It can effectively improve tensile strength and water resistance of soy protein isolate (SPI)-based films. The properties of the SPI-based films were characterized by X-ray diffraction and attenuated total reflectance Fourier transform infrared spectroscopy. The best performance of the SPI-based films was achieved when the ESO addition was 2.5%, for which tensile modulus, tensile strength and 10% offset yield strength were increased to 265.0 MPa, 9.8 MPa and 6.8 MPa, respectively. Compared to untreated SPI-based films, these were increases of 695.6%, 139.8%, and 246.6%, respectively. However, the elongation at break was decreased by 67.6% due to the cross-linking between SPI and ESO. The SPI-based film modified by 5% ESO had the best water-resistance property and reduced the 24 hour water absorption from 209.1% to 45.9%, which was a significant decrease of 78.1%. © The Royal Society of Chemistry.
Wang X.,Tsinghua University |
Wang X.,Beijing Forestry UniversityBeijing |
Shi G.,Tsinghua University
Physical Chemistry Chemical Physics | Year: 2015
Pristine graphene and chemically modified graphenes (CMGs, e.g., graphene oxide, reduced graphene oxide and their derivatives) can react with a variety of chemical substances. These reactions have been applied to modulate the structures and properties of graphene materials, and to extend their functions and practical applications. This perspective outlines the chemistry of graphene, including functionalization, doping, photochemistry, catalytic chemistry, and supramolecular chemistry. The mechanisms of graphene related reactions will be introduced, and the challenges in controlling the chemical reactions of graphene will be discussed. This journal is © the Owner Societies.
Xue Z.,Beijing Forestry UniversityBeijing |
Sun X.,Renmin University of China |
Li Z.,Shandong University |
Mu T.,Renmin University of China
Chemical Communications | Year: 2015
A controllable synthetic route has been developed for the preparation of chitosan supported Pd catalysts in an ionic liquid, 1-butyl-3-methylimidazolium acetate ([Bmim]OAc), by using compressed CO2 as the anti-solvent and regulator. It was found that the dispersion of Pd particles on chitosan and the catalytic activity of the as-prepared catalysts for the hydrogenation of styrene could be tuned by changing the pressure of CO2. This journal is © The Royal Society of Chemistry.
PubMed | Pennsylvania State University, Beijing Forestry University and Beijing Forestry UniversityBeijing
Type: | Journal: Frontiers in microbiology | Year: 2017
PubMed | Beijing Forestry University and Beijing Forestry UniversityBeijing
Type: | Journal: Frontiers in plant science | Year: 2017
Shrublands are one of the major types of ecosystems in the desert regions of northern China, which is expected to be substantially more sensitive to global environmental changes, such as widespread nitrogen enrichment and precipitation changes, than other ecosystem types. However, the interactive effects of nitrogen and precipitation on them remain poorly understood. We conducted a fully factorial field experiment simulating three levels of precipitation (ambient, +20%, +40%) and with two levels of nitrogen deposition (ambient, 60 kg N ha
Yan H.,Beijing Forestry UniversityBeijing |
Yan H.,Zhejiang Agriculture And forestry University |
Dong L.,Beijing Forestry UniversityBeijing
Journal of Environmental Health Science and Engineering | Year: 2015
Abstract Background: This study investigated the microclimatic behavior of different land cover types in urban parks and, the correlation between air temperature and land cover composition to understand how land cover affects outdoor thermal environment during hot summer. Methods: To address this issue, air temperatures were measured on four different land cover types at four observation sites inside an urban park in Beijing, China, meanwhile, the land cover composition of each site was quantified with CAD, by drawing corresponding areas on the aerial photographs. Results: The results showed that the average air temperature difference among four land cover types was large during the day and small during the night. At noon, the average air temperature differed significantly among four land cover types, whereas on night, there was no significant difference among different land cover types. Results of the linear regression indicated that during daytime, there was a strong negative correlation between air temperature and percent tree cover; while at nighttime, a significant negative correlation was observed between air temperature and percent lawn cover. It was shown that as the percent tree cover increased by 10 %, the air temperature decreased by 0.26 °C during daytime, while as the percent lawn cover increased by 10 %, the air temperature decreased by 0.56 °C during nighttime. Conclusions: Results of this study help to clarify the effects of land cover on urban outdoor thermal environment, and can provide assistance to urban planner and designer for improving green space planning and design in the future. © 2015 Yan and Dong; licensee BioMed Central.
Yang J.,Beijing Forestry UniversityBeijing |
Zhang X.,Beijing Forestry UniversityBeijing |
Ma M.,Beijing Forestry UniversityBeijing |
Xu F.,Beijing Forestry UniversityBeijing
ACS Macro Letters | Year: 2015
The biologically inspired dynamic materials offer principles for designing man-made systems by using assembly approach. In this work, the hybrid hydrogels consist of cellulose nanofibrils (CNFs) that combine a mechanically strong skeleton with flexible PEG chains. The distinct gel state is observed at room temperature with G′ > G″ and an order of magnitude higher G′ values from 0.08 to 0.93 kPa upon increasing CNF concentration from 0.2 to 2 wt % at constant 2 wt % PEG. Combined with mechanically strong CNFs and dynamic ionic bridges through amine-terminated tetra-arm PEG adsorption to TEMPO-oxidized colloidal nanofibrils surface, the assembled colloidal hydrogels show high modulus, reversible gel-sol transition, and rapid self-recovery properties. It is envisioned that simply mixing hard CNF and soft polymeric matrix would lead to a facile method to bridge reversible dynamic bonds in a cellulose-based hybrid network and broad cellulose applications in the preparation of high performance supramolecular systems. © 2015 American Chemical Society.