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Taking advantage of heat absorbing and releasing capability of phase change material (PCM),Paraffin wax-based concrete was prepared to assess its automatic temperature control performance.The mechanical properties of PCM concrete with eight different Paraffin wax contents were tested by the cube compression test and four-point bending test.The more Paraffin wax incorporated,the greater loss of the compressive strength and bending strength.Based on the mechanical results,four contents of Paraffin wax were chosen for studying PCM concrete's thermal properties,including thermal conductivity,thermal diffusivity,specific heat capacity,thermal expansion coefficient and adiabatic temperature rise.When the Paraffin wax content increases from 10% to 20%,the thermal conductivity and the thermal diffusivity decrease from 7.31 kJ/(m·h·℃) to 7.10 kJ/(m·h·℃) and from 3.03×10~(-3)m~2/h to 2.44×10~(-3)m~2/h,respectively.Meanwhile the spe‐cific heat capacity and thermal expansion coefficient rise from 5.38×10~(-1)kJ/(kg·℃) to 5.76×10~(-1)kJ/(kg·℃) and from9.63×10~(-6)/℃ to 14.02×10~(-6)/℃,respectively.The adiabatic temperature rise is found to decrease with an increasing Paraffin wax content.Considering both the mechanical and thermal properties,15%of Paraffin wax was elected for the mass con‐crete model test,and the model test results confirm the effect of Paraffin wax in automatic mass concrete temperature control. 相似文献
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Kerosene, a grade mineral oil, is commonly used to extract beetles from sediment. Here, the use of kerosene to extract chironomid
head capsules was tested on 10 samples from sediment of different lakes, with different organic matter content as measured
by loss on ignition, and estimated ages. Our results revealed that this flotation tool is very effective in extracting either
full or half chironomid head capsules. The mean extraction efficiency was 89.3 ± 8.0% with an estimated relative abundance
error ranging from −1% to 1% for 46 of the 57 identified taxa. Larger chironomids (400–500 μm width), which are often full
of sediment particles, have the highest relative abundance error, with a maximum of 4.3% for Corynocera oliveri-type. A canonical correspondence analysis showed that, despite this small bias, samples retrieved with the kerosene flotation
do not differ from the whole sample assemblages. These results give us confidence in the use of this flotation technique for
chironomid sample preparation. 相似文献
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