Step-based tutoring system for introductory linear circuit analysis

338 Provider Opinions of Emergency Department HIV Testing Before and After Program Implementation

Linear circuit analysis is a foundational course for electrical engineers. Instructors of linear circuit analysis courses have traditionally relied on print textbooks for student learning materials. With the rise of student use of computers and the internet, materials like lecture slides and online videos have also been used for learning materials. Increasingly, traditional textbooks (including online formats) are experiencing a decline, while interactive textbooks are growing in popularity. This paper describes auto-graded learning tools, called challenged activities, from various topics in an online linear circuit analysis textbook. Instructors often assign challenge activities as homework. Each challenge activity has 3-5 levels of increasingly difficult problems. Each level randomly generates a question from a large set of questions of similar difficulty. Students must correctly answer a question in a level to progress to the next level. This paper describes the student usage of 4 challenge activities in an online circuit analysis textbook. The average time spent per activity was under 10 minutes and the vast majority of students who started a level ended up completing that level, indicating little attrition. In fact, most levels had 0% of students give up and the highest was only 8%, which is remarkably low based compared to more traditional paper-and-pencil activities based on the teaching experience of the authors.

The risk of sand production must be evaluated from very early stages of field development planning to select the optimum well completion, and if required, identify the appropriate sand control options. However, during the appraisal or early development stages, sand production predictions often cannot be verified against field data because the lack of sanding observations. The analysis of predicting the onset and severity of sand production generally consists of using analytical or numerical rock mechanical models and ideally calibration with field sand production data. In this paper we show how in the absence of field sanding data, reliable sanding predictions can still be achieved by combining commonly used analytical and numerical prediction methods. This approach has been validated using a brown field dataset from South East Asia with several sand producing wells and multiple pressure depleted reservoirs. The analytical method uses a poro-elastic model and core-calibrated log-derived rock strength profiles with an empirical effective rock strength factor (ESF). The ESF should be calibrated against documented field sanding observations from wells with credible formation and drawdown pressures. The numerical method uses a poro-elasto-plastic model defined from triaxial core tests. The rock failure criterion in the numerical method is based on a critical strain limit (CSL) corresponding to the failure of the inner wall of thick-walled cylinder core tests or if existing field sanding data. In the brown oil field example, both analytical and numerical methods accurately predict the onset of sanding in the sand-prone wells. The core-based CSL defined by the numerical method match very well with the field sanding data with a very small margin of error. In contrast, the default and non-calibrated ESF values commonly used in the analytical method required considerable tuning to match with the field sanding data. This suggests that the core-based CSL can be used with a reasonable confidence for sand production prediction purposes in the field and the prediction can be as reliable as field-calibrated models. After the field validation, the predictions for planned infill wells by both analytical and numerical methods were consistent and similar. The paper will show how this approach is used in two other fields from the Asia Pacific region both at appraisal stages and with no field sanding data. Both cases show that different ESF values are required to match with the numerical simulations. In the absence of field sanding observation, particularly in the early stages of field development, the use of non-calibrated default ESF values in the analytical method could lead to erroneous sanding assessment and poor sand management decisions. Application of a combined analytical and numerical sanding evaluation enhances the reliability of sand production predictions. After a calibration is obtained, either with field sanding data or calibration against numerical simulation and core-based CSL criteria, the analytical method can be used with confidence and has the added benefits of simplicity and quick realizations of various scenarios and output plotting capabilities and inputs for sand control and well completion decisions.

Technical note: Measuring separation efficiency of flotation circuits using linear circuit analysis

Computational costs limit large scale reservoir simulations to coarse grid systems. Determination of an effective permeability for a simulation grid block requires a proper scale-up of small scale permeability heterogeneities within that grid block. Conventional scale-up techniques are limited to a diagonal tensor representation of effective permeability. Therefore, such techniques cannot handle general permeability anisotropy (full tensor) exemplified by cross-bedded permeability structures that may be present on a smaller scale. An analytical method is developed to calculate an effective permeability tensor for a grid block by accounting for small scale heterogeneities within the grid block. The method honors both the location and the orientation of the small scale heterogeneities. Effective permeability tensors calculated using the analytical method and a numerical method show excellent agreement. Miscible displacement simulations show that the effective permeability tensor method outperforms conventional scale-up techniques in predicting flood front locations in cases of general permeability anisotropy.

Objectives: To generalize the conventional delta–wye and wye–delta conversions. Methods/Statistical Analysis: The delta–wye and wye–delta conversions have been used to simplify complex electric circuits (networks) consisting of resistors. Three terminal networks consisting of resistors and voltage sources in a wye configuration and in a delta configuration are compared. Findings: In this paper we obtained the conversion relations for emfs from the delta configuation to the wye configuration and vice versa. As an example of the generalization, the conversions are applied to a Wheatstone-bridge type circuit of five batteries and five resistors to obtain its Thevenin’s equivalent. The conversions are applicable to ac as well as dc circuits. As an example of ac circuits the currents through unbalanced loads in a wye configuration connected to a three-phase generator in a delta configuration are calculated. Application/Improvements: The generalized conversions allow to simplify dc and ac circuits.

<div class="section abstract"><div class="htmlview paragraph">In the electrification of automotive and commercial vehicles, batteries are replacing internal combustion engines (ICE) with a battery only power system. The current process uses Linear Circuit Analysis (LCA) and assumes a passive load. The electronics are also assumed to have a constant input voltage from the source. A battery is not capable of providing constant input voltage under automotive use cases resulting in LCA not be applicable for all cases. The non-constant battery voltage will also influence the way electronics are modelled. One specific instance is an EV especially with the traction drive motors where the power demands are considered non-passive.</div><div class="htmlview paragraph">The research will show the discharge behavior of batteries and the results of each of these discharge modes. The research will classify loads as either passive loads or non-passive loads and use the conservation of energy to model non-passive loads with a battery.</div></div>

This chapter introduces the analysis and design of linear circuits. It reviews basic direct‐current (DC) analysis using traditional circuits theorems with application to circuit analysis and design. Using node voltage instead of element voltages as circuit variables can greatly reduce the number of equations that must be treated simultaneously. The chapter treats the analysis and design of circuits containing active devices such as transistors or operational amplifiers (op amps). It also discusses alternating current (AC) circuits. Those ac circuits that are excited by a single frequency, for example, power systems, can be easily and effectively analyzed using sinusoidal steady‐state techniques. Linear circuits are often characterized by their behavior to sinusoids, in particular, how they process signals versus frequency. Audio, communication, instrumentation, and control systems all require signal processing that depends at least in part on their frequency response.

The void fraction of two-phase flow can be measured by conductivity probe due to the difference of conductivity between air and water. It’s difficult to detect the conductivity of the probe directly so transducer circuits should be used to transfer the conductivity to voltage, and the voltage can be sampled by DAQ device. Two transducer circuits are designed for two-phase flow double sensor conductivity probe. One is a simple DC circuit, it’s made up of a constant DC voltage and a resistance, and the resistance is cascaded with the probe. Voltage drop across the resistance is depend on conductivity of surrounding media of probe tip. The other is AC circuit that utilizes a DDS (Direct Digital Synthesizer) as an excitation power supply which links to a transimpedance amplifier through the probe. The current that flow to the amplifier would change according to the surrounding’s medium of the probe. The transimpedance amplifier transfers the current to voltage. Then we use AD8302, an amplitude detection chip, to detect the amplitude of the s output. The experiments show that the DC circuit has a higher SNC (signal to noise ratio) and shorter responding time. However, the needle of probe is covered with electrochemical corrosion products and its performance degrades significantly when DC circuit is used and the probe is immersed in 80°C hot water for 8 hours. This kind of phenomenon is not appeared on the probe when DDS-based circuit is used. The result of the experiment verifies the SNC and responding time of DDS-based circuit is approximately equal to that of the DC circuit.

After completing this chapter, you will be able to: understand concepts and characteristics of the impedance and admittance of AC circuits; define the impedance and admittance of resistor R, inductor L and capacitor C; determine the impedance and admittance of series and parallel AC circuits; apply the voltage divider and current divider rules to AC circuits; apply KCL and KVL to AC circuits understand the concepts of instantaneous power, active power, reactive power, apparent power, power triangle and power factor; and apply the mesh analysis, node voltage analysis, superposition theorem and Thevinin's and Norton's theorems, etc. to analyse AC circuits.

PLMAP — A piecewise linear MOS circuit analysis program

Introduction to Linear Circuit Analysis and Modelling

Analyzing the stability of many control systems required solving a couple of crisp Sylvester matrix equations (CSMEs) simultaneously. However, there are some situations in which the crisp Sylvester matrix equations are not well equipped to deal with the uncertainty problem during the stability analysis of control systems. This paper constructs analytical and numerical methods for solving a couple of trapezoidal fully fuzzy Sylvester matrix equations (CTrFFSMEs) to overcome the drawbacks of the existing crisp methods. In developing these new methods, fuzzy arithmetic multiplication is applied on the CTrFFSME to transform it into an equivalent system of four CSMEs. Then, the fuzzy solution is obtained analytically by the fuzzy matrix vectorization method and numerically by gradient and least square methods. The analytical method can obtain the exact solution; however, it is limited to small-sized systems while the numerical methods can approximate the solution for large dimensional systems up to 100 × 100 with a very small error bound for any initial value. In addition, the proposed methods are applied to other fuzzy systems such as Sylvester and Lyapunov matrix equations. The proposed methods are illustrated by solving numerical examples with different size systems.

Calculation of radial and axial forces and leakage reactance of transformer coils is performed in many papers using different analytical and numerical methods. But most of the analytical methods are extended only for transformers with uniform equal-height windings and then are not very accurate for transformer with no uniform winding arrangement. In this paper, some simple techniques for calculating leakage reactance and forces acting on the transformer coils are presented. This study is accomplished by using 2-1) planar models utilizing the finite element and Roth methods. Just by modeling the transformer and using FEM, the magnetic vector potential is calculated over each node of model and then using several post-processing procedures, the transformer leakage reactance is calculated. Also, this reactance is obtained by analytical method (Roth method) and then results are verified by experiments. The short circuit current and hence the radial and axial forces on the transformer coils during short circuit condition are calculated. Considering some especial cases, the impact of the windings arrangement on the axial force is analyzed and net axial force acting against the yoke are calculated

This paper addresses the problem of worst-case tolerance analysis of steady states in linear DC and AC electric circuits. The statement of the problem considered is in the form of linear algebraic equations whose elements are, in the general case, nonlinear functions of a given set of independent interval parameters. Three kinds of solutions are considered: 1) outer solution; 2) inner solution and 3) exact solution. A direct method for computing an outer solution and an iterative method for finding an inner solution are suggested. The inner and outer solutions thus found provide a tight two-sided bound on the exact solution of the tolerance problem investigated. The exact solution can be determined if certain monotonicity conditions are fulfilled. The verification of the conditions involves solving several associated outer solution problems. The computational efficiency of the methods suggested is demonstrated by a numerical example.