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In this review, some established concepts from Colloidal Science and their application to graphene and carbon nanotubes dispersions in organic or aqueous media are highlighted to rationalize alternatives for some issues in terms of colloidal properties. Recent applications for carbon-based dispersions are presented, as well as van der Waals interactions in carbon materials and strategies to overcome these interactions, such as increasing electrostatic repulsion between dispersed particles, surface functionalization, or adsorption of passivation agents such as macromolecules, which are the basis of many dispersion and exfoliation procedures. The demonstration of how knowledge and fine control of colloidal interactions have been used to overcome several limitations, such as the preparation of stable and concentrated dispersions of carbon materials and keeping appreciable electrical conductivity, is presented. It is also showed that the same knowledge can help the development of more environmentally friendly carbon-based colloids as well as the improvement of similar systems as dispersions of two-dimensional materials. 相似文献
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本文研究了运用单相流量计组合进行液液两相流参数测量的方法.该方法首先通过静态混合器将液液两相流混合成为均相流,然后利用文丘里管获得两相流差压,利用涡轮流量计获得两相流总体积流量,最后通过液液两相流测量模型获得液液两相流总体积流量、总质量流量、混合密度以及分相流量.初步实验结果表明该方法是可行的,在总体积流量1~6 m3/h,油含率15%~85%的范围内,可有效地测量液液两相流的总体积流量、总质量流量和两相流混合密度,测量相对误差在5%以内,但液液两相流分相流量测量相对误差较大,仍需进一步研究. 相似文献
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针对潜在视功能检测仪临床使用中量程有限和对高度屈光不正患者检测结果有一定误差的现象,研究了其光学系统成像特性,建立了系统对视力板成像的视觉放大率公式,分析了准直透镜、成像透镜焦距变化对视觉放大率的影响。系统中视力板移动检测时,准直透镜焦距影响视觉放大率变化快慢,决定视觉放大率曲线的平缓程度;成像透镜焦距对视觉放大率产生整体影响,使视觉放大率曲线产生整体平移。找出了系统的理想参数,能使视觉放大率在整个视力板移动范围内保持不变,消除了检测过程中视力板放大率不同带来的检测误差。通过对各参数的数值分析,得到最优参数,系统检测量程从原来的-7D~+12D扩大为-11D~+15D。 相似文献
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Maximum sound pressure levels are commonly used for environmental noise and building acoustics measurements. This paper investigates the signal processing errors due to Fast or Slow time-weighting detectors when combined with octave band filters, one-third octave band filters or an A-weighting filter. For 6th order Butterworth CPB filters the inherent time delay caused by the phase response of filters is quantified using three different approaches to establish the following rules-of-thumb: (1) time-to-gradient/amplitude matching occurs when Bt ≈ 1, (2) time-to-peak matching occurs when Bt ≈ 2 and (3) time-to-settle matching occurs when Bt ≈ 4 for octave band filters, and when Bt ≈ 3 for one-third octave band filters. Four different commercially-available sound level meters are used to quantify the variation in measured maximum levels using tone bursts, half-sine pulses, ramped noise and recorded transients. Tone bursts indicate that Slow time-weighting is inappropriate for maximum level measurements due to the large bias error. The results also show that there is more variation between sound level meters when considering Fast time-weighted maximum levels in octave bands or one-third octave bands than with A-weighted levels. To reduce the variation between measurements with different sound level meters, it is proposed that limits could be prescribed on the phase response for CPB filters and A-weighting filters. 相似文献