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序。水文流量是江河整治工程施工、设计的重要要素，是研究、规划、治理江河重要依据。本文就在航道测量工作中流量测验的基本内容和方法谈谈个人经验。 相似文献
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本文主要是从席位间的工作分工来探讨流控席的制度问题.众所周知,空中交通管制的目的是:防止机动飞行区内飞机与飞机、飞机与障碍物之间发生碰撞,加速空中交通流量,维持空中交通秩序.因此,在目前可以保证飞机之间存在足够安全间隔的前提下,加速空中流量,提高航班正点率就成了目前空管行业所面临的一个难题.虽然已经有许多专家学者提出了关于流量管理的数量模型,但并未考虑到实际工作中遇到的各种复杂条件,所以个人认为还存在理论上的局限性,下面从管制员在实际工作的角度来控讨下一下加速空中流量中的一个重要问题,即流量控制席(简称流控席)的运用. 相似文献
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工业生产中储罐中的液位非接触式隔离检测是实现精确工业控制的关键。传统的罐体液位检测方法采主要采用红外和声脉冲等探测算法,信号处理精度不高,抗干扰能力差,无法有效实现隔离远程非接触式检测。提出一种基于分离主频发射技术的罐体隐形液位非接触式隔离检测方法,并进行电路设计。设计液位检测超声信号发射机和接收机电路,基于ADP3339来变换DC-DC输出,去除检测仪电路中耦合噪声。实验表明,采用该设计进行冶金高炉钢水液位非接触式隔离检测,共模抑制比高达93dB,有效消除零点漂移现象,提高了液位检测精度。 相似文献
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在石油化工行业中,液位测量对于储运自动化和罐区管理有十分重要的意义。浮球液位检测系统通过在现河采油厂的试验及应用中发现这种测量方式安全可靠,操作简单,能够直吨反映大罐液位,具有双重高度计量,误差实时可校正,具有很好的实用性,是值得推广的一种大罐液位计量方式。 相似文献
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在流量测量中，为精确测量流量应进行温度、压力补偿修正，本文重点介绍应用计算机建立温度、压力补偿数学模型。 相似文献
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1、引言在化学工业生产中,进行流量测量时,被测介质含有杂质是很常见的,由于杂质流速低于主体流速而靠近管壁流动,若使用标准孔板测量其流量,当流体流过测量管时,杂质有可能粘附在流量管和孔板上,不但影响了流体通过孔板时的流速分布,在很大程度上影响了测量精度,而且堵塞处于滞留区的取压孔,影响正常工作。根据资料介绍,煤气管道中的孔板表面上积垢每月约为0.5～0.62mm,主要杂质为萘及焦油。另外,由于企业生产周期长,工作又是连续的,生产一时停不下来,孔板的清扫工作常常无法进 相似文献
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在火力发电厂电和热的生产过程中,为了及时了解设备的生产能力,控制运行工况以及计算热效率与成本核算的数据,必须准确检测生产过程给水流量,主蒸汽流量,供热流量,燃油流量等。流量是保证火电场安全,经济运行的重要参数。差压式流量测量作为流量测量最广泛使用的一种方法。主要介绍了差压变送器的工作原理、常用的测量方式、主要安装方法及注意事项,使用调查法、直观法、检测法诊断差压变送器测量回路的应用故障,并重点对导压管堵塞、泄漏,平衡泄漏、气体流量测量导压管积液等问题引起的故障现象进行了重点分析。 相似文献
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现如今,经济绿色的人工湿地污水处理系统以其独特地魅力吸引着越来越多从事污水处理的学者们。对于目前高效率、快节奏的时代现状,解决如何提高人工湿地污水处理系统的效率问题刻不容缓。通过对当前形式的了解,我们可以明显的看出唯独环保经济、高效率的污水处理系统才能更好的在这个时代传承和发展下去。本实验通过对人工湿地稳定污泥中渗滤液的流量比较,总结出影响渗滤液流量变化的几个重要因素及变化规律。为芦苇床技术作出科学依据。通过试验及对试验数据的分析比较,得出加大渗滤液流量的最佳条件是：芦苇生长数量多、长势茂盛,设置通风管,气温较高且地表湿度较低时,渗滤液流量在本系统中最大。 相似文献
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知识流动效率对创新绩效有着重要影响,在协同创新领域更是如此。为有效测度协同创新知识网络的知识流动效率,本文提出一种基于无向加权网络（Undirected Weighted Network, UWN）的知识流动效率测度模型。首先,基于协同创新知识网络的节点特性、节点间关系特性,构建协同创新知识网络的UWN模型;综合考虑协同创新知识网络中知识流动效率的多重影响因素,提出一个新的知识流动效率测度模型,并进一步提出该模型在成员管理中的延伸应用;最后,通过某智能手机开发企业的应用案例验证本文所提模型与方法的可行性与有效性。 相似文献
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The objective of perforating the petroleum wells is to maximize well productivity. A good connectivity between the wellbore and formation can lead up to achieve that goal. However, the conventional method of perforation, which basically involves the use of explosive charges, rarely meets the expected well productivity. It is mainly because of the formation of a region of reduced permeability around the perforation tunnel. To offset such and several other shortcomings of present practices, a new technique is required, the highlight of this paper. Described as the ‘perforation by drilling’ (PD), this new technique is examined and compared for its performance with that of another technique, ‘Perforation by Shooting’ (PS). For this, the experimental and numerical results of the PS technique on cylindrical sand samples of varying amounts of strength and porosity are studied. Moreover, in order to achieve a so-called ‘perfect perforation’, results are compared with the ‘Casting technique’. Three different samples were selected for the measurement of fluid flow rate and differential pressure across the perforation using a ‘geotechnical digital system’ (GDS), which is a triaxial testing device. Profiles such as fluid flow rate with a change in differential pressure and pressure build-up data with time, signify that the PD technique can achieve maximum wellbore productivity when compared to the PS technique. Results also indicate that at a 100 kPa differential pressure, the PS, PD and Casting techniques can achieve 0.20, 0.65 and 1.00 mL/s fluid flow rates respectively across a sample. The paper also implements a 1-D time dependent porous media flow model to simulate flow across the perforated cylindrical samples created by the PS, PD and Casting techniques. Results show a good consistency between the experimental and numerical approaches. 相似文献
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Dielectrophoretic capture voltage spectrum for measurement of dielectric properties and separation of cancer cells 总被引：1，自引：0，他引：1
In this paper, a new dielectrophoresis (DEP) method based on capture voltage spectrum is proposed for measuring dielectric properties of biological cells. The capture voltage spectrum can be obtained from the balance of dielectrophoretic force and Stokes drag force acting on the cell in a microfluidic device with fluid flow and strip electrodes. The method was demonstrated with the measurement of dielectric properties of human colon cancer cells (HT-29 cells). From the capture voltage spectrum, the real part of Clausius-Mossotti factor of HT-29 cells for different frequencies of applied electric field was obtained. The dielectric properties of cell interior and plasma membrane were then estimated by using single-shell dielectric model. The cell interior permittivity and conductivity were found to be insensitive to changes in the conductivity of the medium in which the cells are suspended, but the measured permittivity and conductivity of cell membrane were found to increase with the increase of medium conductivity. In addition, the measurement of capture voltage spectrum was found to be useful in providing the optimum operating conditions for separating HT-29 cells from other cells (such as red blood cells) using dielectrophoresis. 相似文献
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This paper studies the consensus problem of the multi-agent systems with parallel Luenberger observers. First, the structure of the cooperative system is established, where the output of the built-in Luenberger observer for each agent is used as its local control input and the cooperative control input combining with the cooperative measurement output is utilized as the input of the observers. Based on the structure of the closed-loop system, the consensus problem is then analyzed. In addition, two methods for designing the controller gains are provided. By virtue of the proposed structure, it is pointed out that the design of the controller gains and the observer parameters can be carried out separately. Finally, by resorting to the gradient flow method, an optimization algorithm is proposed to reduce the influence of the environmental noises. The effectiveness of the obtained results is shown through a numerical example. 相似文献
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This paper reports a method to control the fluid flow in paper-based microfluidic devices simply by pressing over the channel surface of paper, thereby decreasing the pore size and permeability of a non-woven polypropylene sheet. As a result, fluid resistance is increased in the pressed region and causes flow rate to decrease. We characterize the decrease of flow rate with respect to different amounts of pressure applied, and up to 740% decrease in flow velocity was achieved. In addition, we demonstrate flow rate control in a Y-shaped merging paper and sequential delivery of multiple color dyes in a three-branched paper. Furthermore, sequential delivery of multiple fluid samples is performed to demonstrate its application in multi-step colorimetric immunoassay, which shows a 4.3-fold signal increase via enhancement step. 相似文献
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In this work, we conduct a computational study on the loading of cryoprotective agents into cells in preparation for cryopreservation. The advantages of microfluidics in cryopreserving cells include control of fluid flow parameters for reliable cryoprotectant loading and reproducible streamlined processing of samples. A 0.25 m long, three inlet T-junction microchannel serves as an idealized environment for this process. The flow field and concentration distribution are determined from a computational fluid dynamics study and cells are tracked as inert particles in a Lagrangian frame. These particles are not confined to streamlines but can migrate laterally due to the Segre-Sildeberg effect for particles in a shear flow. During this tracking, the local concentration field surrounding the cell is monitored. This data are used as input into the Kedem-Katchalsky equations to numerically study passive solute transport across the cell membrane. As a result of the laminar flow, each cell has a unique pathline in the flow field resulting in different residence times and a unique external concentration field along its path. However, in most previous studies, the effect of a spatially varying concentration field on the transport across the cell membrane is ignored. The dynamics of this process are investigated for a population of cells released from the inlet. Using dimensional analysis, we find a governing parameter α, which is the ratio of the time scale for membrane transport to the average residence time in the channel. For α < = 0.224, cryoprotectant loading is completed to within 5% of the target concentration for all of the cells. However, for α > 0.224, we find the population of cells does not achieve complete loading and there is a distribution of intracellular cryoprotective agent concentration amongst the population. Further increasing α beyond a value of 2 leads to negligible cryoprotectant loading. These simulations on populations of cells may lead to improved microfluidic cryopreservation protocols where more consistent cryoprotective agent loading and freezing can be achieved, thus increasing cell survival. 相似文献
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Blood viscosity has been considered as one of important biophysical parameters for effectively monitoring variations in physiological and pathological conditions of circulatory disorders. Standard previous methods make it difficult to evaluate variations of blood viscosity under cardiopulmonary bypass procedures or hemodialysis. In this study, we proposed a unique microfluidic device for simultaneously measuring viscosity and flow rate of whole blood circulating in a complex fluidic network including a rat, a reservoir, a pinch valve, and a peristaltic pump. To demonstrate the proposed method, a twin-shaped microfluidic device, which is composed of two half-circular chambers, two side channels with multiple indicating channels, and one bridge channel, was carefully designed. Based on the microfluidic device, three sequential flow controls were applied to identify viscosity and flow rate of blood, with label-free and sensorless detection. The half-circular chamber was employed to achieve mechanical membrane compliance for flow stabilization in the microfluidic device. To quantify the effect of flow stabilization on flow fluctuations, a formula of pulsation index (PI) was analytically derived using a discrete fluidic circuit model. Using the PI formula, the time constant contributed by the half-circular chamber is estimated to be 8 s. Furthermore, flow fluctuations resulting from the peristaltic pumps are completely removed, especially under periodic flow conditions within short periods (T < 10 s). For performance demonstrations, the proposed method was applied to evaluate blood viscosity with respect to varying flow rate conditions [(a) known blood flow rate via a syringe pump, (b) unknown blood flow rate via a peristaltic pump]. As a result, the flow rate and viscosity of blood can be simultaneously measured with satisfactory accuracy. In addition, the proposed method was successfully applied to identify the viscosity of rat blood, which circulates in a complex fluidic network. These observations confirm that the proposed method can be used for simultaneous measurement of viscosity and flow rate of whole blood circulating in the complex fluid network, with sensorless and label-free detection. Furthermore, the proposed method will be used in evaluating variations in the viscosity of human blood during cardiopulmonary bypass procedures or hemodialysis. 相似文献
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The accurate viscosity measurement of complex fluids is essential for characterizing fluidic behaviors in blood vessels and in microfluidic channels of lab-on-a-chip devices. A microfluidic platform that accurately identifies biophysical properties of blood can be used as a promising tool for the early detections of cardiovascular and microcirculation diseases. In this study, a flow-switching phenomenon depending on hydrodynamic balancing in a microfluidic channel was adopted to conduct viscosity measurement of complex fluids with label-free operation. A microfluidic device for demonstrating this proposed method was designed to have two inlets for supplying the test and reference fluids, two side channels in parallel, and a junction channel connected to the midpoint of the two side channels. According to this proposed method, viscosities of various fluids with different phases (aqueous, oil, and blood) in relation to that of reference fluid were accurately determined by measuring the switching flow-rate ratio between the test and reference fluids, when a reverse flow of the test or reference fluid occurs in the junction channel. An analytical viscosity formula was derived to measure the viscosity of a test fluid in relation to that of the corresponding reference fluid using a discrete circuit model for the microfluidic device. The experimental analysis for evaluating the effects of various parameters on the performance of the proposed method revealed that the fluidic resistance ratio (RJL/RL, fluidic resistance in the junction channel (RJL) to fluidic resistance in the side channel (RL)) strongly affects the measurement accuracy. The microfluidic device with smaller RJL/RL values is helpful to measure accurately the viscosity of the test fluid. The proposed method accurately measured the viscosities of various fluids, including single-phase (Glycerin and plasma) and oil-water phase (oil vs. deionized water) fluids, compared with conventional methods. The proposed method was also successfully applied to measure viscosities of blood with varying hematocrits, chemically fixed RBCS, and channel sizes. Based on these experimental results, the proposed method can be effectively used to measure the viscosities of various fluids easily, without any fluorescent labeling and tedious calibration procedures. 相似文献
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Integration of microfluidic devices with pressure-driven, self-powered fluid flow propulsion methods has provided a very effective solution for on-chip, droplet blood testing applications. However, precise understanding of the physical process governing fluid dynamics in polydimethylsiloxane (PDMS)-based microfluidic devices remains unclear. Here, we propose a pressure-driven diffusion model using Fick''s law and the ideal gas law, the results of which agree well with the experimental fluid dynamics observed in our vacuum pocket-assisted, self-powered microfluidic devices. Notably, this model enables us to precisely tune the flow rate by adjusting two geometrical parameters of the vacuum pocket. By linking the self-powered fluid flow propulsion method to the sedimentation, we also show that direct plasma separation from a drop of whole blood can be achieved using only a simple construction without the need for external power sources, connectors, or a complex operational procedure. Finally, the potential of the vacuum pocket, along with a removable vacuum battery to be integrated with non-PDMS microfluidic devices to drive and control the fluid flow, is demonstrated. 相似文献