排序方式: 共有43条查询结果,搜索用时 15 毫秒
21.
22.
This paper simulated the ultraviolet aging process of asphalt and used dynamic mechanic analysis (DMA) method to evaluate the effect of ultraviolet aging on the asphalt theological properties. After having experienced ultravio- let aging, the low temperature performance of asphalt binder decreased significantly, with its complex modulus increased and phase angle decreased along with changing rheological properties as compared to the performance of original asphalt binder. The ultraviolet aging process would make asphalt binder more sensitive to brittle and fatigue failure. On the basis of the time-temperature superposition principle (TTSP), the viscoelastic transition frequency (coT) is proposed to evaluate the effect of ultraviolet aging. It is found that with the increase in ultraviolet aging time, the cox moves to the lower frequency range gradually. Since the viscoelastic transition frequency is sensitive to the effect of aging, it can be used as an indicator of ultraviolet aging. 相似文献
23.
含磷废水的排放会导致水体富营养化,对生态环境安全造成威胁。本文通过正交试验,制备了一种镍镁铝类水滑石(NiMgAl-HTLC),用于吸附去除废水中的磷元素,并采用SEM、EDS、TEM、XPS及BET等手段对材料进行了表征。为揭示NiMgAl-HTLC吸附磷的机理,对吸附过程的热力学、动力学和影响因素进行了研究。采用吸附除磷后的废水培养浮萍,评价了NiMgAl-HTLC对水体富营养化的抑制能力。结果表明:NiMgAl-HTLC的最佳制备条件为n(Ni)∶n(Mg)∶n(Al)=3∶1∶3,尿素溶液用量为20 mL,反应时间为10 h,反应温度为150℃。制得的NiMgAl-HTLC纳米片厚度约10 nm,比表面积为84.98 m2·g-1;NiMgAl-HTLC对磷的最大吸附量为61.162 1 mg·g-1,吸附过程更符合二级动力学和Langumir热力学模型;在吸附除磷后的废水中,浮萍繁殖速度明显更慢,NiMgAl-HTLC对水体富营养化具有明显的抑制作用。 相似文献
24.
25.
介绍自保温混凝土空心砌块传热过程数值计算的基本原理与具体方法,给出混凝土空心砌块计算实例,并与实验结果进行对比。对混凝土空心砌块在不同孔洞率、考虑与不考虑孔壁表面辐射、浇筑测试实际砌块性能参数等情况下的热工性能进行了分析和探讨。 相似文献
26.
27.
28.
提出了一种新型低功耗、高稳态电平位移电路。该电路能将5 V输入电压转换为10 V输出电压,在电路的初态和电平转换过程中均保持高稳态。采用瞬态增强结构,能加速电平信号之间的转换,有效地减小了传输延迟,提高了电路稳定性。瞬态增强结构在稳定状态时不发挥作用,减小了静态功耗,获得了低功耗。基于标准0.35 μm BCD工艺和多5 V LDMOS耐压器件,对该电平位移电路在5 MHz频率下进行验证。结果表明,动态功耗仅为24.8 μA,上升沿响应速度仅为12.7 ns,下降沿响应速度仅为22.8 ns。该电路具有可靠性高、功耗低的优点。 相似文献
29.
30.