Cement-bonded particleboards of 6 mm in thickness were manufactured using maize stalk （Zea mays） particles of uniform sizes at three levels of board density and additive concentrations respectively. The bending stre...Cement-bonded particleboards of 6 mm in thickness were manufactured using maize stalk （Zea mays） particles of uniform sizes at three levels of board density and additive concentrations respectively. The bending strength and dimensional properties were assessed. Increase in board density and additive concentration caused increase in Modulus of rupture （MOR）, Modulus of elasticity （MOE）, and decrease in Thickness swelling （TS） and Water absorption （WA）. The MOR, MOE and TS of the boards were significantly affected by board density except for WA, but additive concentration affected all the boards＇ properties examined at p ≥ 0.05. Strong and dimensional stable cement-bonded boards could be manufactured from maize stalk particles with Portland cement as the binder after hot water treatment. Although the dimensional stability and mechanical strength properties of the boards were affected by the board density and additive concentration, the study revealed that cement-bonded particleboards could be manufactured from maize stalk （Zea mays） particles. However, the increase in board density and additive concentration could cause the increase in MOR and MOE, and cause the decrease in TS and WA of boards.展开更多
In order to control the quality of spline shaft in rolling process, an efficient measurement method for rolling performance evaluation is essential. Here, a newly developed on-machine non-contact measurement prototype...In order to control the quality of spline shaft in rolling process, an efficient measurement method for rolling performance evaluation is essential. Here, a newly developed on-machine non-contact measurement prototype based on laser displacement sensor and rotary encoder is proposed. The prototype is intended for the automated evaluation of the spline shaft rolling performance by measuring the dimensional change of tooth root, which is correlated with the surface residual stress and micro-hardness. Laser displacement sensor and rotary encoder are used to record the polar radius and polar angle of each point on measuring section. Data are displayed in a polar coordinate system and fitted in a gear. Through multipoint curvature method, the roots of spline shaft are recognized automatically. Then, the dimensional change can be calculated by fitting the radius of the tooth root circle before and after rolling. Systematic error covering offset error is also analyzed and calibrated. At last, measurement test results show that the system has advantages of simple structure, high measurement precision(radius error < 0.6 μm), high measurement efficiency(measuring time < 2 s) and automatic control ability, providing a new opportunity for the efficient evaluation of various spline shafts in high-precision mechanical processing.展开更多
This review focuses on a new alternative approach towards MOF preparation through the transformation of known MOF structures into other novel,more active MOFs that,in most cases,could not be obtained by conventional s...This review focuses on a new alternative approach towards MOF preparation through the transformation of known MOF structures into other novel,more active MOFs that,in most cases,could not be obtained by conventional synthetic methods.These transformations are usually of the single-crystal-to-singlecrystal type,usually accompanied by a modification of the dimensionality of the MOFs:e.g.,1D→2D,2D→3D,1D→3D or even 3D→3D’(concerning modification of the connectivity of the primary building units).The literature contains several reports concerning MOF-to-MOF transformations but only in a handful of cases the authors aimed to design new functional compounds,pointing towards applications or the modification(or improvement)of the properties of the materials.This review aims to concisely describe the most significant reports concerning the transformation of MOFs into other more functional and active MOFs.Several types of transformations are possible including solvent removal or insertion,modification of the pH,metal exchange,release of active molecules,among others.These transformations can lead to significant improvements of the properties of MOFs,for example:increase of adsorption of different gases,such as nitrogen and carbon dioxide;creation of sensing centers for different chemical species;pH sensing with,in some cases,a concomitant change in crystal color;improvement of the luminescence properties by the removal of solvent molecules.Other transformations could lead instead to a complete modification of the properties of MOFs such as the appearance of magnetic properties,the creation of storage devices,the design of releasing materials by the incorporation of active molecules or water scavengers.展开更多
文摘Cement-bonded particleboards of 6 mm in thickness were manufactured using maize stalk （Zea mays） particles of uniform sizes at three levels of board density and additive concentrations respectively. The bending strength and dimensional properties were assessed. Increase in board density and additive concentration caused increase in Modulus of rupture （MOR）, Modulus of elasticity （MOE）, and decrease in Thickness swelling （TS） and Water absorption （WA）. The MOR, MOE and TS of the boards were significantly affected by board density except for WA, but additive concentration affected all the boards＇ properties examined at p ≥ 0.05. Strong and dimensional stable cement-bonded boards could be manufactured from maize stalk particles with Portland cement as the binder after hot water treatment. Although the dimensional stability and mechanical strength properties of the boards were affected by the board density and additive concentration, the study revealed that cement-bonded particleboards could be manufactured from maize stalk （Zea mays） particles. However, the increase in board density and additive concentration could cause the increase in MOR and MOE, and cause the decrease in TS and WA of boards.
基金Supported by Industrial Technology Development Program of China(Grant Nos.JCKY2017208C005,A0920132008)National Natural Science Foundation of China(Grant No.51575049)
文摘In order to control the quality of spline shaft in rolling process, an efficient measurement method for rolling performance evaluation is essential. Here, a newly developed on-machine non-contact measurement prototype based on laser displacement sensor and rotary encoder is proposed. The prototype is intended for the automated evaluation of the spline shaft rolling performance by measuring the dimensional change of tooth root, which is correlated with the surface residual stress and micro-hardness. Laser displacement sensor and rotary encoder are used to record the polar radius and polar angle of each point on measuring section. Data are displayed in a polar coordinate system and fitted in a gear. Through multipoint curvature method, the roots of spline shaft are recognized automatically. Then, the dimensional change can be calculated by fitting the radius of the tooth root circle before and after rolling. Systematic error covering offset error is also analyzed and calibrated. At last, measurement test results show that the system has advantages of simple structure, high measurement precision(radius error < 0.6 μm), high measurement efficiency(measuring time < 2 s) and automatic control ability, providing a new opportunity for the efficient evaluation of various spline shafts in high-precision mechanical processing.
基金Fundação para a Ciência e a Tecnologia(FCT,Portugal),the European Union,QREN,and FEDER through Programa Operacional Factores de Competitividade(COMPETE)the scope of the project CICECO-Aveiro Institute of Materials(Ref.FCT UID/CTM/50011/2013),financed by national funds through the FCT/MEC and when applicable co-financed by FEDER under the PT2020 Partnership Agreement+1 种基金FCT for funding the R&D project FCOMP-01-0124-FEDER-041282(Ref.FCT EXPL/CTM-NAN/0013/2013)the Ph.D.scholarship no.SFRH/BD/84231/2012(to RFM).
文摘This review focuses on a new alternative approach towards MOF preparation through the transformation of known MOF structures into other novel,more active MOFs that,in most cases,could not be obtained by conventional synthetic methods.These transformations are usually of the single-crystal-to-singlecrystal type,usually accompanied by a modification of the dimensionality of the MOFs:e.g.,1D→2D,2D→3D,1D→3D or even 3D→3D’(concerning modification of the connectivity of the primary building units).The literature contains several reports concerning MOF-to-MOF transformations but only in a handful of cases the authors aimed to design new functional compounds,pointing towards applications or the modification(or improvement)of the properties of the materials.This review aims to concisely describe the most significant reports concerning the transformation of MOFs into other more functional and active MOFs.Several types of transformations are possible including solvent removal or insertion,modification of the pH,metal exchange,release of active molecules,among others.These transformations can lead to significant improvements of the properties of MOFs,for example:increase of adsorption of different gases,such as nitrogen and carbon dioxide;creation of sensing centers for different chemical species;pH sensing with,in some cases,a concomitant change in crystal color;improvement of the luminescence properties by the removal of solvent molecules.Other transformations could lead instead to a complete modification of the properties of MOFs such as the appearance of magnetic properties,the creation of storage devices,the design of releasing materials by the incorporation of active molecules or water scavengers.
