共查询到20条相似文献，搜索用时 265 毫秒
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水泥生料中碳酸钙滴定值的测定,化学分析采用酸碱中和法,它是一项控制分析。而计算简便,是控制分析中要求之一。本文提出一种使酸碱浓度值的控制更简便的方法,进行探讨。一、公式推导生料CaCO3滴定值的计算公式如下: 相似文献
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王小妍 《内蒙古科技与经济》2011,(9):57-58
分析了恶臭物质的来源和危害,针对臭气的治理方法,介绍了物理脱臭法、化学脱臭法、生物脱臭法的技术原理,并以污水处理厂为例,简要介绍了生物滴滤法的运行情况。 相似文献
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文章通过对磷钼酸喹啉重量法、离子交换柱色谱法和钼蓝分光光度法等三种磷含量测定方法的比较,说明了各种方法在实际测定中的操作方法、原理及优缺点。 相似文献
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氟作为煤中的有害元素之一,因其对生态危害性得到很多关注。目前的测定方法主要有水解法、氧弹法或半熔法熔样,用氟离子选择性电极测定。三种方法比对研究,探讨了三种方法的优劣及其机理,结果表明水解法熔样有最好的准确度和精密度。 相似文献
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针对工业中广泛应用的管壳式换热器,比较了几种壳侧流动的分析方法,并在此基础上提出了适宜于单相和气液两相流路分析法的壳侧单元流动模型。以主流、旁路流和泄漏流等各分流路的气液流量分布在稳态下应使壳侧流动的能量损耗达到最小的原则为基础,建立了壳侧气液两相流路分析法,给出了各流路的气液流量比例及错流区、窗口区压降的预测步骤,也给出了壳侧总压降计算式。建立的两相流路分析法预测结果与试验结果符合较好。 相似文献
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并联管组模型流动压损分析（一） 总被引：1，自引：0，他引：1
流体在并联管组模型中流动的均匀性问题具有非常广泛的应用背景。U型分布的是循环电液电堆中经常使用的模型。通过Fluent软件对其进行数值模拟,试图探讨单体个数和电堆压损之间的关系。经计算发现,在流量一定的前提下,随单体数量的增加,电堆压损递减,但不是单调递减,而是存在一个关键的拐点,当单体数超过拐点值后,压损基本恒定。另通过模拟计算发现,在单体数一定的情况下,电堆压损与流量对应关系。 相似文献
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Frank F Yun Zhenwei Yu Yahua He Lei Jiang Zhao Wang Haoshuang Gu Xiaolin Wang 《国家科学评论(英文版)》2020,7(2):366
Room-temperature liquid metal is discovered to be capable of penetrating through macro- and microporous materials by applying a voltage. The liquid metal penetration effects are demonstrated in various porous materials such as tissue paper, thick and fine sponges, fabrics, and meshes. The underlying mechanism is that the high surface tension of liquid metal can be significantly reduced to near-zero due to the voltage-induced oxidation of the liquid metal surface in a solution. It is the extremely low surface tension and gravity that cause the liquid metal to superwet the solid surface, leading to the penetration phenomena. These findings offer new opportunities for novel microfluidic applications and could promote further discovery of more exotic fluid states of liquid metals. 相似文献
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Liquid filling in microfluidic channels is a complex process that depends on a variety of geometric, operating, and material parameters such as microchannel geometry, flow velocity∕pressure, liquid surface tension, and contact angle of channel surface. Accurate analysis of the filling process can provide key insights into the filling time, air bubble trapping, and dead zone formation, and help evaluate trade-offs among the various design parameters and lead to optimal chip design. However, efficient modeling of liquid filling in complex microfluidic networks continues to be a significant challenge. High-fidelity computational methods, such as the volume of fluid method, are prohibitively expensive from a computational standpoint. Analytical models, on the other hand, are primarily applicable to idealized geometries and, hence, are unable to accurately capture chip level behavior of complex microfluidic systems. This paper presents a parametrized dynamic model for the system-level analysis of liquid filling in three-dimensional (3D) microfluidic networks. In our approach, a complex microfluidic network is deconstructed into a set of commonly used components, such as reservoirs, microchannels, and junctions. The components are then assembled according to their spatial layout and operating rationale to achieve a rapid system-level model. A dynamic model based on the transient momentum equation is developed to track the liquid front in the microchannels. The principle of mass conservation at the junction is used to link the fluidic parameters in the microchannels emanating from the junction. Assembly of these component models yields a set of differential and algebraic equations, which upon integration provides temporal information of the liquid filling process, particularly liquid front propagation (i.e., the arrival time). The models are used to simulate the transient liquid filling process in a variety of microfluidic constructs and in a multiplexer, representing a complex microfluidic network. The accuracy (relative error less than 7%) and orders-of-magnitude speedup (30 000X–4 000 000X) of our system-level models are verified by comparison against 3D high-fidelity numerical studies. Our findings clearly establish the utility of our models and simulation methodology for fast, reliable analysis of liquid filling to guide the design optimization of complex microfluidic networks. 相似文献
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Ultrafast microfluidics using surface acoustic waves 总被引：2，自引：0，他引：2
We demonstrate that surface acoustic waves (SAWs), nanometer amplitude Rayleigh waves driven at megahertz order frequencies propagating on the surface of a piezoelectric substrate, offer a powerful method for driving a host of extremely fast microfluidic actuation and micro∕bioparticle manipulation schemes. We show that sessile drops can be translated rapidly on planar substrates or fluid can be pumped through microchannels at 1–10 cm∕s velocities, which are typically one to two orders quicker than that afforded by current microfluidic technologies. Through symmetry-breaking, azimuthal recirculation can be induced within the drop to drive strong inertial microcentrifugation for micromixing and particle concentration or separation. Similar micromixing strategies can be induced in the same microchannel in which fluid is pumped with the SAW by merely changing the SAW frequency to rapidly switch the uniform through-flow into a chaotic oscillatory flow by exploiting superpositioning of the irradiated sound waves from the sidewalls of the microchannel. If the flow is sufficiently quiescent, the nodes of the transverse standing wave that arises across the microchannel also allow for particle aggregation, and hence, sorting on nodal lines. In addition, the SAW also facilitates other microfluidic capabilities. For example, capillary waves excited at the free surface of a sessile drop by the SAW underneath it can be exploited for micro∕nanoparticle collection and sorting at nodal points or lines at low powers. At higher powers, the large accelerations off the substrate surface as the SAW propagates across drives rapid destabilization of the drop free surface giving rise to inertial liquid jets that persist over 1–2 cm in length or atomization of the entire drop to produce 1–10 μm monodispersed aerosol droplets, which can be exploited for ink-jet printing, mass spectrometry interfacing, or pulmonary drug delivery. The atomization of polymer∕protein solutions can also be used for the rapid synthesis of 150–200 nm polymer∕protein particles or biodegradable polymeric shells in which proteins, peptides, and other therapeutic molecules are encapsulated within for controlled release drug delivery. The atomization of thin films behind a translating drop containing polymer solutions also gives rise to long-range spatial ordering of regular polymer spots whose size and spacing are dependent on the SAW frequency, thus offering a simple and powerful method for polymer patterning without requiring surface treatment or physical∕chemical templating. 相似文献
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气象要素空间化方法精度的比较研究——以平均气温为例 总被引：29，自引：0，他引：29
以国家气象局1971年～2000年30年整编资料中的东北、华中地区1978年、1984年、1990年、1996年4年的1月份、7月份及年平均气温数据为数据源,采用直接插值法(反距离权重法和普通克里格法)、趋势面模拟 残差内插法、空间化气候值 年际距平空间插值方法、空间化气候值 年际距平趋势面模拟 残差内插等4种方法,进行了空间化精度的比较研究.通过平均绝对误差(MAE)、平均相对误差(MRE)以及交叉验证等几种评估标准的比较,认定在具有30年月平均气温栅格数据库作为背景的前提下,采用空间化气候值 年际距平值IDW内插的方法在东北、华中两个地区空间化的误差相对较小,并且其操作方便,是一种对平均气温这一要素的短时间序列空间化而言既方便,插值效果又相对较好的空间化方法. 相似文献
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Charles S. Peskin 《Journal of The Franklin Institute》1974,297(5):335-343
Heart valves when closed consist of membranes under tension bearing a pressure load. Along the lines where the leaflets meet, special support structures under tension are needed (a fibrous ridge for the arterial valves and a network of cords for the atrioventricular valves). The equilibrium of these supports requires that the valve leaflets form cusps along each line of closure. In the aortic and pulmonary valves there is evidence that the stress in the leaflet is borne by a single family of load-bearing fibers covering the surface. Under this hypothesis, we derive a differential equation for the leaflet and show that the fibers are geodetic lines under constant tension. During the large motions of valve opening and closure certain constraints are imposed on the surface metric by the presence of (almost) inextensible fibers in the surface. The severity of the constraints depends on the number of independent families of fibers. 相似文献