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251.
为满足5G电子封装材料的性能需求,将一定量的改性中空玻璃微珠(f-HGM)和氮化硼(f-BN)添加进加成型液体硅橡胶中制备了低介电、高导热且阻燃的硅橡胶复合材料。测试结果表明,添加了10份f-HGM和15份f-BN的复合材料的介电常数为2.68,介电损耗为0.008 16,显著低于纯硅橡胶,热导率为0.518 W/m·K,是纯硅橡胶的2.25倍。此外,复合材料的热稳定性得到了提升,pHRR和THR分别下降了55.3%和37.7%。通过气相和凝聚相分析发现,复合材料的气相热解产物浓度大幅降低,残炭的致密性和连续性得到显著提升。 相似文献
252.
对电导率法测定平流沉淀池的停留时间进行研究并进行了实际应用,与传统的Cl-浓度测定法相比,电导率法简便易行,准确度也较高。 相似文献
253.
This paper describes a mathematical model for the pyrolysis of a small dry pine wood cylinder. The computational domain is axisymmetric and involves the heating chamber, with the wood cylinder vertically situated in the centre of the chamber. The model simulates the laminar flow around the particle and the laminar flow inside the wood/char matrix by applying a two-phase transport model where the solid wood/char matrix acts as one phase and the various gases produced from the pyrolysis process is assembled in the other phase. Convective, conductive and thermal radiation transfer modes are included in the model. A two-step pyrolysis reaction scheme is used for the modelling of the conversion from wood to tar and gas. Both the thermal conductivity and the permeability of the wood/char matrix are modelled anisotropically in order to capture the directional differences in heat and mass transport, existing in real wood. Results from simulations are compared with measurements from literature for the centre core solid temperature and the conversion from wood to char, tar and pyrolysis gas in the particle during heating. The results show very good agreement with the measured temperature profile. The simulated conversion profile shows an overall good agreement with the measurements, however with discrepancies in the early stage of the process. Besides the successful validation with the experimental data, it provides us with all the details of the distribution of the migrating pyrolysis gas and tar, the temperature, the velocity flow field and pressure in the wood/char cylinder. 相似文献
254.
为了改善静电除尘器极板防腐性能、增加极板的抗污性能和提高极板清灰效果,用导电防腐涂料涂敷电除尘器极板.提出了涂层比电阻特性数学模型并用实验加以验证.推导了极板沉积粉尘层积累电荷量公式,表明电荷量多少与粉尘层放电时间常数成正比.理论研究结果表明,涂加涂层后,极板上低比电阻粉尘层放电时间常数增大,粉尘层积累电荷量增多,粉尘层与极板问静电附着力增大,有效减弱了粉尘的二次飞扬现象;通过降低涂层的比电阻和涂层厚度,使中高比电阻粉尘层的积累电荷量增加不大.实验测试了涂层对不同比电阻粉尘收尘效率的影响及涂层对极板粉尘剥离率的改善.实验结果显示,涂加涂层后,低比电阻粉尘的收集效率有显著提高,中高比电阻粉尘的收集效率变化不大;极板粉尘剥离率较不加涂层时有很大提高.极板涂敷技术有效延长了极板的使用寿命,在保证除尘效率的前提下提高了极板的清灰效果,是电除尘领域中的一项创新. 相似文献
255.
256.
轨道清扫器是起重机械上重要的安全防护装置之一。对于桥、门式起重机而言,因其轨道附近堆积物料复杂,轨道清扫器的设置与工作状况往往直接影响整机的安全。本文笔者探讨了传统轨遒清扫器形式及其失效模式,自主研发的新型起重机械轨道清扫器能够很好的起到轨道清扫和避免运行车轮脱轨等危险事故地发生,保证了起重机械使用过程中运行的可靠性和安全性,一定程度地减少事故发生。 相似文献
257.
为了寻找快速、简便、精确地测量液体蛋鸡粪便中总氮(TN)、总磷(TP)、有机物(OM)、铵态氮(AN)和总钾(TK)含量的方法,研究了采样前将样品搅拌或静置对所取样品代表性的影响,并用75份生长期为4~6月龄蛋鸡的液体粪便样本建立了密度(SG)与TN、TP、OM,电导率(EC)与AN和TK的一元线性回归模型以及SG、EC、pH与TN、TP、OM、AN和TK的多元线性回归模型.结果表明,对于TN、TP、OM、AN,采样前将样品充分搅拌是获得代表性样本的前提条件,而搅拌与否并不影响TK代表性样本的获得.SG与TN、TP、OM,EC与AN和TK均存在显著的线性相关性(P<0.001),模型的决定系数(R2)均较高,分别为0.94,0.94,0.95,0.94和0.94,多元线性模型的决定系数高于一元线性模型的决定系数.用另外15份样本对5个一元线性回归模型进行验证,并对模型系数b和常数项a进行t检验,得出在显著水平α=0.05上,假设Ha0:(a)=0和Hb0:(b)=1全部接受.由此认为,SG与TN、TP和OM,EC与AN和TK所建立的一元线性回归模型均具有较好的预测效果. 相似文献
258.
259.
Data from 90 tracer experiments performed in low-permeability fractured media have been studied to explore correlations among parameters controlling flow and transport. The original data had been interpreted by different authors using different models, which prevents direct comparison of their estimated parameters. In order to produce comparable parameters, the data have been reexamined using simple models (homogeneous domain, steady-state flow regime, single porosity). Specifically, hydraulic conductivity has been derived as the ratio of water flux to head gradient and apparent porosity as the ratio of water velocity to water flux; the former estimated from both first and peak arrival times. Hydraulic conductivity and porosity correlate along a straight line of slope 1:3 in log scale. While the regression is too noisy to be of predictive use, it lends some support to the use of a generalized cubic law. The fact that correlation for first arrival time porosity (0.77) is larger than for peak arrival porosity (0.62) suggests that first arrival is controlled by the same flow paths as hydraulic conductivity. Apparent porosity derived from peak arrival time is found to grow with travel time along a line of 0.55 slope (again log scale). The correlation coefficient ranges between 0.73 and 0.80 (depending on the data set) for hard rocks. The fact that this correlation is maintained when varying the flow rate at a given site leads us to suggest that it is caused by diffusion mechanisms. This conclusion is further supported by the increase of apparent porosity with the matrix porosity of the rock on which the experiments were performed. 相似文献
260.
Christina N. Kranz Richard A. McLaughlin Aziz Amoozegar Joshua L. Heitman 《Journal of the American Water Resources Association》2023,59(5):1115-1127
There has been widespread interest in using compost to improve the hydrologic functions of degraded soils at construction sites for reducing runoff and increasing infiltration. The objective of this study was to determine the effects of compost amendment rate on saturated hydraulic conductivity (Ks) and water retention in order to identify target compost rates for enhancing soil hydrologic functions. Samples were prepared with three soil textures (sandy loam, silt loam, and sandy clay loam), amended with compost at 0%, 10%, 20%, 30%, 40%, and 50%. All soils were tested at a porosity of 0.5 m3/m3, and the sandy loam was further tested at high (0.55 m3/m3) and low (0.4 m3/m3) porosities. The Ks and water retention data were then used to model infiltration with HYDRUS-1D. With increasing compost amendment rate, Ks and water retention of the mixtures generally increased at the medium porosity level, with more compost needed in heavier soils. As porosity decreased in the sandy loam soil, the amount of compost needed to improve Ks rose from 20% to 50%. Water distribution in pore fractions (gravitational, plant-available, and unavailable water) depended on texture, with only the highest compost rates increasing plant-available water in one soil. Results suggest soil texture should be taken into consideration when choosing a compost rate in order to achieve soil improvement goals. Hydrologic benefits may be limited even at a high rate of compost amendment if soil is compacted. 相似文献