Spring Meeting of the Illinois Section of the AAPT
March 28-29, 2014 - Illinois Wesleyan University, Bloomington, Illinois

Last update:  March 21, 2014

This file is updated within a day or two after anyone submits a Call for Contributed Presentations.

Active Learning

Rebecca Vieyra,
Active Learning, Saturday morning
Equipment needs: LCD Projector, Internet Access

Free Mobile Device Apps for Data Collection and Analysis. Rebecca E. Vieyra, Chrystian Vieyra, Cary-Grove High School, Cary, IL 60013. Mobile devices are loaded with sensors that can be accessed to collect data using free apps, and data can be easily imported into analysis software. Benefits of using apps for data collection include that students often have access to their own devices, and can use them in the classroom, at home, or even on field trips. Physics Toolbox apps ( - created for the science classroom for use with introductory physics students - will specifically be demonstrated to show how students can use their mobile devices to collect data. Physics Toolbox apps are currently available include: Accelerometer, Magnetometer, Light Sensor, Gyroscope, Sound Meter, Proximity Sensor, Barometer, Hygrometer, and Thermometer, among others. See "Analyzing Forces on Amusement Park Rides with Mobile Devices" (March 2014) in The Physics Teacher. Participants will have the opportunity to speak with the app designer and request new apps and modifications to existing apps.

  Andrew Morrison,
Active Learning, Either day

Moving Towards Standards Based Grading in College Physics. Andrew Morrison, Joliet Junior College, Joliet, IL 60540. A growing number of teachers are moving away from traditional methods of assigning grades and using a standards based grading (SBG) approach. This year, I have implemented some SBG principles in an introductory astronomy course for general education credit in college. The strengths and challenges of moving towards SBG will be discussed.

Teaching Methods

Thomas Foster,
Teaching Methods, Either day

A Blended Laboratory. Tom Foster, Southern Illinois University Edwardsville, Edwardsville, IL 62026-1654. At Southern Illinois University Edwardsville, Department of Physics, we have been investigating the use of simulations to support the laboratory experience. Six different labs have been written using the 5E inquiry guide to learning for both the in-class and simulation laboratories. We also have a performance evaluation to gauge student learning of the processes of science. We will share what we have learned from two implementations to small classes.

  Carl Wenning,
Teaching Methods, Either day
Equipment needs: video projector
Comments: will use PowerPoint presentation; will bring own laptop

A Simple Car Crash Reconstruction Project. Carl J. Wenning, Illinois State University, Normal, IL 61790-4560. The speaker will describe a simple car crash reconstruction project that he has used successfully with algebra-based and general education physics courses at ISU. The project provides an excellent opportunity for students to apply what they know about kinematics, dynamics, and conservation principles to a real-world situation. Students can either work in teams or individually to solve the question about who was at fault – if anyone – for a car crash that took three young lives. 

Noella Dcruz, ndcruz@jj.cedu
Teaching Methods, Either day
Equipment needs: Projector and Computer with PowerPoint.

Essays in the Non-science Major Astrobiology Course. Noella Dcruz, Joliet Junior College, Joliet, IL 60431. Joliet Junior College offers a "Life in the Universe" course for non-science majors. The breadth of astrobiology topics covers in this course allows for some topics to be explored through projects. Instead of offering one or two large projects, we ask students to submit three short essays on topics such as "A Manned Mission to Mars?," "Talking Back: Responding to an Extraterrestrial Intelligence Signal," "Which jovian would you explore?," etc. We will present our essay topics and our Fall 2013 students' feedback on these essays.

  Emily Roth,>
Teaching Methods, Either day
Equipment needs: Powerpoint

A Study of the Effects of Homework Delivery Methods on Exam Performance. Emily Roth, Jose Lozano, Kevin Kimberlin, Bradley University, Peoria, IL 61625. Is electronic homework more effective than written homework on student exam performance? For the past 18 months we have studied 5 sections of algebra-based introductory mechanics at Bradley University. The factors we analyzed were electronic homework completion time, written and electronic homework scores, average exam scores, and FCI scores. All sections were taught in the traditional format and with very similar pedagogy. The results of this study will be discussed, specifically the effects of homework completion time on exam performance and the correlation between homework scores and exam performance.

Bill Hogan,
Teaching Methods, Saturday morning
Equipment needs: Chalkboard and chalk or whiteboard and marker

To Tilt or Not to Tilt.... Bill Hogan, Joliet Junior College, Joliet, IL 60431. The classic introductory physics of a car on a banked road with friction can be solved with either horizontal and vertical axes or axes that are parallel and perpendicular to the road surface. I recently stumbled into an interesting classroom discussion with my students about the advantages, disadvantages, and difficulties of each choice and I will share some of that discussion during my presentation.

  Narendra Jaggi,
Teaching Methods, Either day
Equipment needs: Power-point presentation

A Report on the 2014 National Conference on Introductory Physics for the Life Sciences (IPLS). Narendra K. Jaggi, Illinois Wesleyan University, Bloomington, IL 61702. At the most recent national AAPT conference on Introductory Physics for the Life Sciences (IPLS), held in Arlington, VA, March 14-16, 2014, a number of panels discussed a number of potentially very significant changes to the MCAT exam, the guidelines from A.M.A. concerning science preparation of physicians, and the changing landscape of expectations from IPLS courses and laboratories. A number of universities have already implemented large scale changes in their IPLS courses. I attended all of these panel discussions, and presentations.  I will try to summarize key issues, and draw attention to resources that are available for adapting our curricula.


Don Reid,
Demonstrations, Either day

Waves and Sound Demonstrations. Don Reid, Lincolnwood High School, Raymond, IL 62560. This session will include a collection of demonstrations designed to illustrate wave and sound phenomenon in a easily visible (and in some cases audible) way.



Hans Muehsler,
Research, Friday afternoon
Equipment needs: PowerPoint, projector

The DuPage County Regional Office of Education Physics Exam: An overview and psychometric assessment. Hans Muehsler, Naperville Central High School, Naperville, IL 60540. In 2009, the DuPage County Regional Office of Education (ROE) tasked volunteer physics teachers with creating a basic skills physics exam reflecting what the participants valued and shared in common across curricula. Mechanics, electricity & magnetism (E&M), and wave phenomena emerged as the primary constructs. The resulting exam was intended for first-exposure physics students. The most recently completed version was psychometrically assessed for unidimensionality within the constructs using a robust WLS structural equation model and for reliability. An item analysis using a 3-PL IRT model was performed on the mechanics items and a 2-PL IRT model was performed on the E&M and waves items; a distractor analysis was also performed on all items. Lastly, differential item functioning (DIF) and differential test functioning (DTF) analyses, using the Mantel-Haenszel procedure, were performed using gender, ethnicity, year in school, ELL, physics level, and math level as groupings.

  Pengqian Wang,
Research, Friday afternoon
Equipment needs: PowerPoint
Comments: I arrive at about 3:00 pm. Thanks.

Observing Crystals in Plants by a Polarizing Microscope. Pengqian Wang, Western Illinois University, Macomb, IL 61455. The Department of Physics at Western Illinois University recently acquired a polarizing microscope to support student labs and faculty research. This microscope is mainly used in studying the optical properties of crystals and other optically anisotropic materials. Compared to a normal optical microscope, a polarizing microscope has many additional features. It has a rotatable polarizer and analyzer. A Bertrend lens can be inserted to observe conoscopic interference patterns from the specimen. In this talk I present our observation of the calcium oxalate crystals in onion and garlic skins. The crystals have a prismatic shape, with a size ranging from several to a few tens of micrometers. The shapes, sizes and numbers of the crystals vary with the species of the plants and the layers of the skins. They are mostly inside the cells. Preliminary study shows that these crystals are optically birefringent, and some of them appear to be strongly dichroic.

Curtis Shoaf,
Research, Saturday morning
Equipment needs: Projector, Yes I plan on using powerpoint.
Comments: Can I connect my iPad to computer?

Do Labs Need to be Done in a Laboratory?. Curtis M. Shoaf, Parkland College, Champaign, IL 61822. The Department of Natural Sciences at Parkland College designed a cross-disciplinary research study involving Astronomy, Biology, Chemistry, Earth Science and Physics courses to determine if achievement of student learning outcomes were equal across multiple methods of lab delivery formats including traditional labs, virtual simulations and the use of at-home lab kits. The study also contained instruments designed around three key theoretical frameworks which have been shown to impact student learning: self-efficacy, teacher immediacy and satisfaction. The study was controlled, in part, by having the three experimental labs delivered via all three formats simultaneously with one third of each section's students in each delivery method. Students were then rotated so that every student completed a lab using each of the three delivery methods. Results of the study may challenge traditional viewpoints concerning the delivery of labs. Data from the study will equip instructors to address the concerns of students in non-traditional labs.



Morten Lundsgaard,
Other, Either day
Comments: I will use a PowerPoint presentation

Teacher Centered Professional Development - creating and testing IOLab lessons. Morten Lundsgaard and Christopher P. Cunnings, University of Illinois Urbana-Champaign, Urbana, IL 61801. In this presentation, we describe a lesson-study inspired approach to professional development (PD) program that focuses on the development of laboratory centered lessons. The PD-program consists of a two-week long summer session and three study group sessions held during the school year. In the summer session, teachers are developing IOLab-based lessons that they implement in their classroom in the fall semester. The PD providers document the implementation of the lessons by videotaping the classroom instructions. Following each implementation, teachers and PD providers meet to discuss how the lessons played out. At these study group sessions, video clips of instruction serve as starting points for the discussion. By studying teacher collaboration and the teacher discussions, we obtain information on how teachers connect different instructional activities, and on the importance of teachers' autonomy and sharing of classroom experiences for changes in teachers' attitude toward instruction.


Student Research Symposium

Huy Do,
Student Research Symposium, Saturday morning
Equipment needs: Power Point Presentation

Development of a Rotational Stage for Operation at 4K Temperature. Huy Do, Illinois Wesleyan University, Bloomington, IL 61701. A simple mechanical device, such as a clock, will not function properly when placed in a low temperature environment such as outer space. While designing and building the mechanical apparatus for low temperatures, we have to consider (1) special lubricants for ball bearings (standard lubricants will freeze at low temperature, thus stalling the rotation) and (2) strict requirements for the materials we can use. High precision is also important in the machining process. To solve these problems we have investigated the performance of hybrid ball bearings that are dry lubricated with tungsten disulfide (WS2). We use aluminum and G10 because of its machinability and low thermal conductivity. Early test results indicate that the design works well enough. At a temperature of 77 K, the minimum torque needed to rotate the wheel is about 3.33 Nm, which is not prohibitive for our application.

  Kinnary Patel,
Student Research Symposium, Friday afternoon
Equipment needs: Power point file

Spectroscopic and Radiative Properties of Nd3+ ions Doped Lead Boro-Tellurite Glasses. Kinnary Patel, P.K. Babu, Saisudha B. Mallur, Western Illinois University, Macomb, IL 61455. Lead boro-tellurite glasses with composition (x-y) PbO – 20 TeO2 – (80-x) B2O3 – y Nd2O3, y = 0.5, x=20, 30, 40, 50, 60, 70 mol% were prepared by the melt-quench technique. Optical absorption experiments were carried out as a function of glass composition. The optical absorption spectra were analyzed using the Judd-Ofelt theory and the intensity parameters Ωt (t=2,4,6) were determined. Using the intensity parameters, we calculated the radiative transition probability (ARad), radiative lifetime, and branching ratios (βR) for different states. The compositional dependence of Ωt (t=2,4,6) has been attributed to the changes in the asymmetry of the ligand field at the rare-earth (R) site (due to the structural changes) and to changes in R-O covalency. The variation of Ωt (t=2,4,6) with PbO content indicates an increasing order around the R ion at ~25-30 mol% PbO. Large radiative transition probabilities are observed for these glasses.

Ashish Adhikari,
Student Research Symposium, Friday afternoon
Equipment needs: Power point file

Compositional Dependence of Refractive Index and Optical Band Gap in Lead Borate and Samarium doped Lead Borate Glasses. Ashish Adhikari, P.K. Babu, Saisudha B. Mallur, Western Illinois University, Macomb, IL 61455. Variation of refractive index and optical band gap of lead borate glasses of composition x PbO – (100-x) B2O3, (series A) and (x-0.5) PbO – (100-x) B2O3 – 0.5 Sm2O3, (series B), 30 mol% ≤ x ≤ 70 mol% were investigated. The refractive index (n) was measured experimentally using the Brewster's angle method and then compared with theoretically calculated values using the Lorentz-Lorenz equation and Effective Medium Theory. The optical band gap (Eopt) was obtained from the analysis of the optical absorption spectra using the David and Mott relation. The refractive index increased with PbO concentration whereas the optical band gap decreased. The increase in refractive index can be attributed to the increased polarizability as a result of addition of highly polarizable ions to the glass network and the decrease in optical gap is believed to be due to an increase in the covalency of PbO bonds.

  Aisha Farag,
Student Research Symposium, Friday afternoon
Equipment needs: Power point file

Variation of Optical Band Gap with Composition in Nd3+ Doped Lead Boro-Tellurite Glasses. Aisha Farag, P.K. Babu, Saisudha B. Mallur, Western Illinois University, Macomb, IL 61455. Study of optical absorption near the fundamental absorption edge is a useful method for the investigation of optically-induced transitions, band structure and the optical band gap in glasses. For the present work, glasses (x-0.5) PbO – 20 TeO2 – (80-x) B2O3 – 0.5 Nd2O3 where x = 20, 30, 40, 50, 60, 70 mol%, have been prepared by the melt quenching technique. Optical absorption spectra obtained for these glasses show that the fundamental absorption edge lies in the wavelength range 350-500 nm. The edge shows a shift towards longer wavelengths (lower energy) with increasing PbO content. The absorption spectra were analyzed using the Mott-Davis model to determine optical energy gaps of these glasses. The optical band gap of these glasses decreases from 2.98 to 2.69 eV with increasing PbO content from 19.5 to 69.5 mol% and it is due to the structural modifications and alterations in the covalency of the Pb-O bond.

Tommy Esposito,
Student Research Symposium, Friday afternoon
Equipment needs: a powerpoint presentation will be used

Orientation Effects in Excitation-Ionization of Helium. Tommy Esposito, Dr. Allison Harris, Illinois State University, Normal, IL 61790. Atomic collisions provide key insights into one of the most fundamental forces of nature – the Coulomb force. The study of atomic collisions is primarily used to understand the dynamics of charged particle interactions, but is vital to other areas of physics, such as plasma physics, astrophysics, and biophysics. Traditionally, only geometries where all particles were found in a single plane have been studied, but experimental advancements now allow for the study of full 3-dimensional collision geometries. In this work, we study out-of-plane scattering for electron-impact excitation-ionization of helium through computational modeling. Preliminary results show interesting out-of-plane structure, and we examine several possible causes for this structure.

  Wallace Santos Teixeira,
Student Research Symposium, Friday afternoon

Towards Quantum Dynamical Decoupling with Trapped Ions. Wallace Santos Teixeira and Kishor T. Kapale, Western Illinois University, Macomb, IL 61455. Quantum decoherence is the main obstacle for devising quantum information systems in large scale. However, some alternatives have been employed in order to face this problem, such as quantum error correction, quantum control, and dynamical decoupling. We are interested in checking and finding methods to suppress the decoherence on a qubit, in particular using the Uhrig dynamical decoupling (UDD) with trapped ions.

Timothy Woodworth,
Student Research Symposium, Friday afternoon
Comments: Will use PowerPoint

Quantum Error Correction. Timothy Woodworth, Kishor Kapale, Western Illinois University, Canton, IL 61520. In 1981 Feynman spoke at MIT about how to simulate physical systems with computers. He conjectured that the binary nature of computers make them unsuitable to show real life situations in an efficient manner. He suggested that the continuous nature of superposition offered by quantum mechanical systems could lead to very powerful computers. There has been a significant hurdle in making this quantum computer a reality, mainly decoherence. Decoherence results when there exists an unwanted interaction between the quantum system of interest interacts and its environment causing errors in the results of the computation. Quantum Error Correction (QEC) is the field that involves search for specific encoding of the quantum information that will allows for detection and corrections of computational errors. In my talk I will discuss some of these codes and analyze the process of designing the codes and how they function to eliminate some common errors.

  Daniel DeYoung,
Student Research Symposium, Friday afternoon
Equipment needs: Powerpoint

Generation of Asymmetric Dicke States. Daniel DeYoung, Western Illinois University, Macomb, IL 61455. Dicke class states are maximally entangled states of atoms or atom-like two-state entities involving a small number of excitations (much less that the total number of atoms). It has been shown in the literature [Z.H. Peng, J. Zou, X.J. Liu, Eur. Phys. J. D 58, 403-407 (2010)] that the so-called asymmetric Dicke states, which carry different relative phases for different permutations corresponding to different atomic entity being in the excited state, are more useful for quantum information processing tasks than the symmetric Dicke states. We have devised a practical conceptual proposal for generation of asymmetric Dicke states based on a proposal to generate symmetric Dicke states [Thiel et al. Phys. Rev. Lett. 99, 193602 (2007)]. We shot that the asymmetric Dicke-class states can be used for perfect teleportation [Agrawal and Pati, Phys. Rev. A 74 062320 (2006)] and dense coding. 

Christopher Legner,
Student Research Symposium, Friday afternoon
Equipment needs: PowerPoint

Chaotic Systems and Phase Synchrony: An Experimental Study of Coupled Oscillators. Christopher Legner and Epaminondas Rosa, Illinois State University, Normal, IL 61790. Chaotic systems are interesting because they underlay many processes in physics, chemistry, economics, and biology. A better understanding of these systems provides insight into the mechanisms dictating the dynamics of these processes. This study employs a relatively well known complex chaotic circuit, the Chua circuit. We experimentally want to determine the synchronous effects different coupling strengths have on two Chua circuits. An interpretation of this coupling is performed by determining the overall effect on the phase of the systems in terms of the "phase synchrony" of the two circuits. Phase synchrony takes place when the phases of two the signals align over a given time period. The detection of phase synchronous states is done with the help of a computer program written specifically for analyzing the collected data.

  Quinton Skilling,
Student Research Symposium, Friday afternoon
Equipment needs: PDF presentation
Comments: Please schedule between 2:00 - 3:00 P.M. on Friday afternoon

Nonlinear Dynamic Properties of the Huber-Braun Model Equations Applied to Simulate Gastric Mill Rhythms in Crustaceans. Quinton Skilling, Epaminondas Rosa and Wolfgang Stein, Illinois State University, Normal, IL 61790. Neural systems are present in many living organisms, varying both in size and functionality. The application of computational physics to these systems can provide fruitful insights into processes sometimes not accessible experimentally. By constructing and implementing mathematical neuron models, for example, it is possible to both reproduce biological system behavior and provide an explanation for poorly understood mechanisms. Here, we examine the nonlinear properties of the conductance-based Huber-Braun neuron model, extended to include synaptic input variables, and how these properties can be translated to biophysical processes that cause stable rhythms in neural systems. The model itself showcases a rich dynamic behavior of membrane potentials in neurons which, when coupled to other neurons, can produce highly nontrivial system behavior. Particular interest is paid to the gastric mill Central Pattern Generator in the stomatogastric ganglion of the crab Cancer borealis, which is responsible for driving mastication and therefore is vital to survival.

Andrew Steinacher,
Student Research Symposium, Saturday morning
Comments: preferred order 1 of 6 (Steinacher, Maggio, Vikartofsky, Betke, Su, Norris)

Impact of Interfermionic Forces on the Pair Creation Process. Andrew Steinacher, Intense Laser Physics Theory Unit and Department of Physics, Illinois State University, Normal, IL 61790-4560. Using a simplistic model in one-spatial dimension, we estimate the impact of the electron-electron, positron-positron and electron-positron forces on the yield of the pair creation process triggered by an external superstrong force. We separate the potentials in the Dirac equation into external and internal parts, where the dynamics of the internal potential is governed by the Maxwell equations with the Dirac charge and current density as sources terms. We show that once the particle pair is created, the mutual attraction keeps the particles from being accelerated out of the interaction zone. As the result a charge cloud can accumulate that can seriously suppress the pair creation process due to the resulting Pauli-suppression in the interaction zone. [1] [1] A. Steinacher, R.E. Wagner, Q. Su and R. Grobe, Phys. Rev. A (in press).

  Miles Maggio,
Student Research Symposium, Saturday morning
Comments: preferred order 2 of 6 (Steinacher, Maggio, Vikartofsky, Betke, Su, Norris)

2-D is not 1-D plus one 1-D. Miles Maggio, Intense Laser Physics Theory Unit and Department of Physics, Illinois State University, Normal, IL 61790-4560. The creation of electron-positron pairs is a process where the vacuum state breaks down due to a supercritical external field. Numerical algorithm has been devised to calculate the number of created pairs. In order to consider the interaction between created particles the intermediating electromagnetic field needs to be introduced. However in one-spatial dimension the force field between the created particles do not fall off with the inter-particle separation. To study this inter-charge interaction it is essential to extend these studies to at least two spatial dimensions. We discuss how to extend our pair creation formulation from 1D to 2D. We will show that it is not obvious that the physics of 2D pair creation is simply the "sum" of two independent one-dimensional creations, as the underlying motions in the two dimensions are coupled due to relativity.

Andrew Vikartofsky ,
Student Research Symposium, Saturday morning
Comments: preferred order 3 of 6 (Steinacher, Maggio, Vikartofsky, Betke, Su, Norris)

The Physical Vacuum and the Approximation of Photons by Maxwell Fields. Andrew Vikartofsky, Intense Laser Physics Theory Unit and Department of Physics, Illinois State University, Normal, IL 61790-4560. We discuss the role of virtual particles in the description of the physical vacuum. Through simple one-dimensional model systems we have demonstrated how the physical vacuum can be decomposed into the bare vacuum and virtual particles [1]. We analyze the momentum distribution of the vacuum virtual pairs as well as the spatial and temporal correlations between virtual particles for both systems. The application of a supercritical field can cause the vacuum breakdown to produce electron-positron pairs. An analysis of the interacting electron-positron-photon system is currently not feasible due to memory and cpu time constraints even for the most advanced supercomputers. We discuss the pros and cons of a theory where the photon is approximated by a classical Maxwell field. [1] R.E. Wagner, M.R. Ware, A.M. Vikartofsky, Q. Su and R. Grobe, Int. J. Theor. Phys. 51, 3787-3804 (2012).

  Jarrett Betke,
Student Research Symposium, Saturday morning
Comments: preferred order 4 of 6 (Steinacher, Maggio, Vikartofsky, Betke, Su, Norris)

Space-time Dynamics of the Vacuum's Polarization Charge Density. Jarrett Betke, Intense Laser Physics Theory Unit and Department of Physics, Illinois State University, Normal, IL 61790-4560. Using numerical solutions to the quantum field theoretical Dirac equation, we study the space-time evolution of the vacuum's polarization charge and current densities induced by an external electric force in one spatial dimension. We discuss a remarkably simple analytical model that can predict the dynamics of the polarization dynamics for arbitrary external force configurations. We then study the corrections to these predictions when the external force becomes supercritical and real electron-positron pairs can be created. By coupling the Dirac equation to the Maxwell equations we examine how the dynamics of the polarization density is affected, if we allow the corresponding virtual charges to interact with each other [1] J. Betke, A.T. Steinacher, S. Ahrens, Q. Su and R. Grobe, Phys. Rev. A (submitted).

Alexander Su,
Student Research Symposium, Saturday morning
Comments: preferred order 5 of 6 (Steinacher, Maggio, Vikartofsky, Betke, Su, Norris)

Enhancement of Boson Pairs Created by Electromagnetic Fields. Alexander Su, Intense Laser Physics Theory Unit and Department of Physics, Illinois State University, Normal, IL 61790-4560. By solving the quantum field theoretical version of the Klein-Gordon equation numerically, we study the creation process for charged boson/antiboson pairs in static electric and magnetic fields. The fields are perpendicular to each other and spatially localized along the same direction, which permits us to study the crucial impact of the magnetic field's spatial extension on dynamics. If its width is comparable to that of the electric field, we find a magnetically-induced Lorentz suppression of the pair creation process. When the width is increased such that the created bosons can revisit the interaction region, we find a region of exponential self-amplification that can be attributed to a spontaneous emission-like enhancement. If the width is increased further, this trend is reversed and the magnetic field can even shut off the particle production completely [1]. [1] Q. Lv, A.C. Su, M. Jiang, Y. Li, R. Grobe, Q. Su, PRA 87, 023416 (2013).

  Samantha Norris,
Student Research Symposium, Saturday morning
Comments: preferred order 6 of 6 (Steinacher, Maggio, Vikartofsky, Betke, Su, Norris)

Instantaneous Rest Frame Transformation Method for Temporally Induced Pair Creation. Samantha Norris, Intense Laser Physics Theory Unit and Department of Physics, Illinois State University, Normal, IL 61790-4560. We introduce a computational method to determine the rate of the electron-positron pair creation triggered by a time-dependent subcritical external field [1]. It is based on constructing a Lorentz transformation to an instantaneous rest frame, for which the pair creation rate can be determined by standard techniques. We will discuss the accuracy and efficiency of this method by comparing its predictions with exact time-dependent quantum field theoretical solutions to the Dirac and Klein-Gordon equation for various space-time dependent external fields. [1] Q.Z. Lv, A. Vikartofsky, S. Norris, Y.J. Li, R. Wagner, R. Grobe and Q. Su, Phys. Rev. A (submitted).