Justification of Non-Dimensional Schemes and Identification of Parameters on Modelling Electrokinetic Transport Phenomena in Microchannels

2010 ◽  
Author(s):  
Zhanjie Shao ◽  
Gerry Schneider ◽  
Carolyn Ren
Keyword(s):  
Initial Conditions ◽  
Transport Phenomena ◽  
Concentration Field ◽  
Electrokinetic Transport ◽  
Dimensional Model ◽  
Applied Potential ◽  
Governing Equations ◽  
Numerical Studies ◽  
Electrokinetic Flows ◽  
On Chip

The electrokinetic transport phenomena are to be numerically studied based on cross-linked microchannel networks, which have been commonly employed for on-chip capillary electrophoresis applications. Applied potential field, flow field and concentration field should be solved to predict the species transport process under electrokinetic flows. Together with the well-designed channel geometry, a detailed physical model was firstly formulated through a series of governing equations and corresponding boundary/initial conditions, which was briefly re-presented from our previous publications. The emphasis of current work was to justify the simplest non-dimensional scheme and identify the most beneficial parameters so that an effective and simplified non-dimensional model was developed for numerical studies.

Numerical Studies of Injection Process Control With Spatial Gradients of Electrical Conductivity

2003 ◽  
Author(s):  
Liqing Ren ◽  
Dongqing Li
Keyword(s):  
Transport Phenomena ◽  
Glass Plate ◽  
Concentration Field ◽  
Lab On A Chip ◽  
Theoretical Models ◽  
Spatial Gradient ◽  
Precise Control ◽  
Spatial Gradients ◽  
Injection Process ◽  
Numerical Studies

The systematic design and precise control of the microfluidic dispenser (crossing microchannels etched into a plastic or glass plate) is key to the performance of many lab-on-a-chip devices. The fundamental understanding of the complicated electrokinetic phenomena in microfluidic dispensers therefore is necessary. In the literature, a few theoretical models studying the transport phenomena in similar crossing microchannels didn’t consider the spatial gradients of conductivity due to its complexity. A new theoretical model was developed in this paper to simulate the transport phenomena in a microfluidic dispenser with the consideration of a large range of spatial gradient of electric conductivity. This developed model was used to simulate the potential field, flow field, and concentration field of the injection processes where the conductivity of the sample-carrying buffer differs significantly from that of the driving buffer. The transport phenomena are found to be very sensitive to the conductivity difference between the sample-carrying buffer and the driving buffer. The developed model can be employed to find the optimal voltages for controlling the dispensed sample size and to provide guidance for designing such a microfluidic dispenser in lab-on-a-chip devices.

Numerical Simulation of On-Chip Injection Process With Spatial Gradients of Electrical Conductivity

2003 ◽  
Author(s):  
Liqing Ren ◽  
Dongqing Li
Keyword(s):  
Transport Phenomena ◽  
Glass Plate ◽  
Concentration Field ◽  
Lab On A Chip ◽  
Theoretical Models ◽  
Spatial Gradient ◽  
Precise Control ◽  
Spatial Gradients ◽  
Injection Process ◽  
On Chip

The systematic design and precise control of the microfluidic dispenser (crossing microchannels etched into a plastic of glass plate) is key to the performance of many lab-on-a-chip devices. The fundamental understanding of the complicated electrokinetic phenomena in microfluidic dispensers therefore is necessary. In the literature, a few theoretical models studying the transport phenomena in similar crossing microchannels didn’t consider the spatial gradients of conductivity due to its complexity. A new theoretical model was developed in this paper to simulate the transport phenomena in a microfluidic dispenser with the consideration of a large range of spatial gradient of electric conductivity. This developed model was used to simulate the potential field, flow field, and concentration field of the injection processes where the conductivity of the sample-carrying buffer differs significantly from that of the driving buffer. The transport phenomena are found to be very sensitive to the conductivity difference between the sample-carrying buffer and the driving buffer. The developed model can be employed to find the optimal voltages for controlling the dispensed sample size and to provide guidance for designing such a microfluidic dispenser in lab-on-a-chip devices.

scholarly journals EXACT SOLUTION OF AN IRREVERSIBLE ONE-DIMENSIONAL MODEL WITH FULLY BIASED SPIN EXCHANGES

1996 ◽  
Vol 10 (25) ◽  
pp. 3451-3459 ◽  
Author(s):  
ANTÓNIO M.R. CADILHE ◽  
VLADIMIR PRIVMAN
Keyword(s):  
Exact Solution ◽  
Domain Wall ◽  
Nearest Neighbor ◽  
Spin Exchange ◽  
Initial Conditions ◽  
Strong Dependence ◽  
Zero Temperature ◽  
Dimensional Model ◽  
One Dimensional ◽  
Temperature Dynamics

We introduce a model with conserved dynamics, where nearest neighbor pairs of spins ↑↓ (↓↑) can exchange to assume the configuration ↓↑ (↑↓), with rate β(α), through energy decreasing moves only. We report exact solution for the case when one of the rates, α or β, is zero. The irreversibility of such zero-temperature dynamics results in strong dependence on the initial conditions. Domain wall arguments suggest that for more general, finite-temperature models with steady states the dynamical critical exponent for the anisotropic spin exchange is different from the isotropic value.

Predictive Modeling of Nonlinear Regenerative Chatter via Measurement, Analysis, and Simulation

1999 ◽  
Author(s):  
J. R. Pratt ◽  
M. A. Davies ◽  
M. D. Kennedy ◽  
T. Kalmár-Nagy
Keyword(s):  
Cutting Force ◽  
Initial Conditions ◽  
Stability Boundary ◽  
Chip Thickness ◽  
Cutting Parameters ◽  
Computational Techniques ◽  
Regenerative Chatter ◽  
Stability Lobe ◽  
Measurement Analysis ◽  
On Chip

Abstract A single-degree-of-freedom active cutting fixture is employed to reveal and analyse the hysteretic nature of the lobed stability boundary in a simple machining experiment. Specifically, the seventh stability lobe of a regenerative cutting process is mapped using experimental, analytical, and computational techniques. Then, taking width of cut as a control parameter, the transition from stable cutting to chatter is observed experimentally. The cutting stability is found to possess a substantial hysteresis so that either stable or chattering tool motions can exist at the same nominal cutting parameters, depending on initial conditions. This behavior is predicted by applying nonlinear regenerative chatter theory to an empirical characterization of the cutting force dependence on chip thickness. Time-domain simulations that incorporate both the nonlinear cutting force dependence on chip thickness and the multiple-regenerative effect due to the tool leaving the cut are shown to agree both qualitatively and quantitatively with experiment.

scholarly journals Analysis of Total Column CO<sub>2</sub> and CH<sub>4</sub> Measurements in Berlin with WRF-GHG

2019 ◽  
Author(s):  
Xinxu Zhao ◽  
Julia Marshall ◽  
Stephan Hachinger ◽  
Christoph Gerbig ◽  
Jia Chen
Keyword(s):  
Urban Areas ◽  
Initial Conditions ◽  
Ghg Emissions ◽  
Concentration Field ◽  
Weather Research And Forecasting ◽  
Background Concentration ◽  
Wind Fields ◽  
Simulated Wind ◽  
Global Population ◽  
Good Agreement

Abstract. Though they cover less than 3 % of the global land area, urban areas are responsible for over 70 % of the global greenhouse gas (GHG) emissions and contain 55 % of the global population. A quantitative tracking of GHG emissions in urban areas is therefore of great importance, with the aim of accurately assessing the amount of emissions and identifying the emission sources. The Weather Research and Forecasting model (WRF) coupled with GHG modules (WRF-GHG) developed for mesoscale atmospheric GHG transport, can predict column-averaged abundances of CO2 and CH4 (XCO2 and XCH4). In this study, we use WRF-GHG to model the Berlin area at a high spatial resolution of 1 km. The simulated wind and concentration fields were compared with the measurements from a campaign performed around Berlin in 2014 (Hase et al., 2015). The measured and simulated wind fields mostly demonstrate good agreement and the simulated XCO2 agrees well with the measurement. In contrast, a bias in the simulated XCH4 of around 2.7 % is found, caused by relatively high initialization values for the background concentration field. We find that an analysis using differential column methodology (DCM) works well for the XCH4 comparison, as corresponding background biases then cancel out. From the tracer analysis, we find that the enhancement of XCH4 is highly dependent on human activities. The XCO2 signal in the vicinity of Berlin is dominated by anthropogenic behavior rather than biogenic activities. We conclude that DCM is an effective method for comparing models to observations independently of biases caused, e.g., by initial conditions. It allows us to use our high resolution WRF-GHG model to detect and understand sources of GHG emissions quantitatively in urban areas.

Transport Mechanisms in Electrokinetic Nanoscale Channels

2004 ◽  
Author(s):  
Sumita Pennathur ◽  
Juan G. Santiago
Keyword(s):  
Field Theory ◽  
Parametric Study ◽  
Nanometer Scale ◽  
Transport Mechanisms ◽  
Electrokinetic Transport ◽  
Zeta Potentials ◽  
Numerical Studies ◽  
Debye Layer ◽  
Model Predictions ◽  
Shape And Size

We investigate electrokinetic transport in nanometer-scale fluidic channels. Our study includes numerical studies of nanofluidic transport of both charged and uncharged analytes in conditions of finite Debye layer thickness and high zeta potentials. The models are based on continuum mass transport and field theory. We also perform an experimental parametric study using etched nanoscale channels. Experimental results agree with model predictions and show that bulk electrokinetic transport in nanoscale channels depends strongly on the shape and size of the EDL and on the effects of transverse electrophoretic migration.

A Data-Driven Exploratory Approach for Level Curve Estimation With Autonomous Underwater Agents

2017 ◽  
Author(s):  
Hsien-Chung Lin ◽  
Eugen Solowjow ◽  
Masayoshi Tomizuka ◽  
Edwin Kreuzer
Keyword(s):  
Concentration Field ◽  
Real Data ◽  
Support Vector ◽  
Level Curve ◽  
Data Set ◽  
Curve Estimation ◽  
Numerical Studies ◽  
Exploratory Approach ◽  
Vector Machines ◽  
Myopic Strategy

This contribution presents a method to estimate environmental boundaries with mobile agents. The agents sample a concentration field of interest at their respective positions and infer a level curve of the unknown field. The presented method is based on support vector machines (SVMs), whereby the concentration level of interest serves as the decision boundary. The field itself does not have to be estimated in order to obtain the level curve which makes the method computationally very appealing. A myopic strategy is developed to pick locations that yield most informative concentration measurements. Cooperative operations of multiple agents are demonstrated by dividing the domain in Voronoi tessellations. Numerical studies demonstrate the feasibility of the method on a real data set of the California coastal area. The exploration strategy is benchmarked against random walk which it clearly outperforms.

PCB Effects on On-chip Capacitor Requirements and an Efficient Resonance-Prevention ASIC Methodology

2010 ◽  
Vol 2010 (1) ◽  
pp. 000392-000399
Author(s):  
Timothy Budell ◽  
Eric Tremble
Keyword(s):  
Design Methodology ◽  
Current Flow ◽  
Power Delivery ◽  
Switching Activity ◽  
Dimensional Model ◽  
Power Delivery Network ◽  
Model Component ◽  
The Subject ◽  
On Chip ◽  
The Relationship

A method for determining adequate quantities and locations of on-chip capacitors to maintain supply voltages at all locations on a chip within pre-specified limits given the switching activity of on-chip circuits was presented in [3]. In this paper, we extend the method to include current flow from the package and PCB. The effects of on-chip capacitance and other system parasitics on the time it takes for additional supply current to flow into a chip are discussed. The relationship between switching current, capacitance, system parasitic inductances, and on-chip noise is presented. These concepts are then applied to the subject of power delivery network (PDN) resonance. A 1-dimensional model for simulating PDN resonance is presented. The model includes chip, package, and PCB components, along with explicit networks for each chip power supply and their interactions. The topology of the model and the contributions of each model component are described. A design methodology for avoiding PDN resonance, presently in use on all IBM ASIC modules, is presented.

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