arXiv subjects

H. J. Lewandowski

Publications and source records attributed to H. J. Lewandowski.

At least 91 records · Page 5Linked to original sources

arXiv2016

Investigating the role of model-based reasoning while troubleshooting an electric circuit

We explore the overlap of two nationally-recognized learning outcomes for physics lab courses, namely, the ability to model experimental systems and the ability to troubleshoot a malfunctioning apparatus. Modeling and troubleshooting are both nonlinear, recursive processes that involve using models to inform revisions to an apparatus. To probe the overlap of modeling and troubleshooting, we collected audiovisual data from think-aloud activities in which eight pairs of students from two institutions attempted to diagnose and repair a malfunctioning electrical circuit. We characterize the cognitive tasks and model-based reasoning that students employed during this activity. In doing so, we demonstrate that troubleshooting engages students in the core scientific practice of modeling.

physics.ed-ph↗

arXiv2015

Persistence of a Non-Equilibrium State: Observation of a Boltzmannian Special Case

Well before the atomistic nature of matter was experimentally established, Ludwig Boltzmann's audacious effort to explain the macroscopic world of human experience in terms of the workings of an unseen microscopic world met with vigorous opposition. A contentious point was the problem of irreversibility: the microscopic equations of motion are reversible, yet friction and viscosity cause things always to slow down and warm up, never to speed up and cool down. What was worse, Boltzmann himself discovered that his transport equation predicts special cases in which gases never come to thermal equilibrium, a particular example being that the monopole "breathe" mode of gas will never damp if it is confined in 3D to a perfectly isotropic harmonic potential. Such absences of damping were not observed in nature. Nondamping of a monopole mode in lower dimensional systems has only very recently been observed, using cold atoms. Kinoshita et al. and Chevy et al. have experimentally observed suppressed relaxation in highly elongated geometries. The difficulty in generating sufficiently spherical harmonic confinement for ultracold atoms, however, has meant that Boltzmann's fully 3D, isotropic case has never been observed. With the development of a new magnetic trap capable of producing near-spherical harmonic confinement for ultracold atoms, we have been able to make the first observation of this historically significant oddity. We observe a monopole mode for which the collisional contribution to damping vanishes, a long-delayed vindication for Boltzmann's microscopic theory.

cond-mat.quant-gas↗

arXiv2015

Redesigning a junior-level electronics course to support engagement in scientific practices

Building on successful work on studying and transforming our senior-level Advanced Lab course, we have transformed our junior-level Electronics course to engage students in a variety of authentic scientific practices, including constructing, testing, and refining models of canonical measurement tools and analog circuits. We describe our approach to the transformation, provide a framework for incorporating authentic scientific practices, and present initial outcomes from the project. As part of the broader assessment of these course transformations, we examine one course learning outcome: development of the ability to model measurement systems. We demonstrate that in the transformed course students demonstrate greater likelihood of identifying discrepancies between the measurement and the model and significantly greater tendencies to refine their models to reconcile with the measurement.

physics.ed-ph↗

arXiv2015

Correlating students' beliefs about experimental physics with lab course success

Student learning in instructional physics labs is a growing area of research that includes studies exploring students' beliefs and expectations about experimental physics. To directly probe students' epistemologies about experimental physics and support broader lab transformation efforts both at the University of Colorado Boulder (CU) and nationally, we developed the Colorado Learning Attitudes about Science Survey for Experimental Physics (E-CLASS). Previous work focused on establishing the accuracy and clarity of the instrument through student interviews and preliminary testing. Ongoing validation efforts include establishing the extent to which student epistemologies as measured by E-CLASS align with other measures of student learning outcomes (e.g., course grades). Here, we report on correlations between final course grades and E-CLASS scores from two semesters of introductory and upper-division lab courses at CU and discuss implications of our findings for the validity of the E-CLASS instrument.

physics.ed-ph↗

arXiv2015

The role of modeling in troubleshooting: an example from electronics

Troubleshooting systems is integral to experimental physics in both research and instructional laboratory settings. The recently adopted AAPT Lab Guidelines identify troubleshooting as an important learning outcome of the undergraduate laboratory curriculum. We investigate students' model-based reasoning on a troubleshooting task using data collected in think-aloud interviews during which pairs of students attempted to diagnose and repair a malfunctioning circuit. Our analysis scheme is informed by the Experimental Modeling Framework, which describes physicists' use of mathematical and conceptual models when reasoning about experimental systems. We show that this framework is a useful lens through which to characterize the troubleshooting process.

physics.ed-ph↗

arXiv2015

Access to undergraduate research experiences at a large research university

The American Physical Society recently released a statement calling on all university physics departments to provide or facilitate access to research experiences for all undergraduate students. In response, we investigated the current status of access to undergraduate research at University of Colorado Boulder (CU), a large research institution where the number of undergraduate physics majors outnumber faculty by roughly ten to one. We created and administered two surveys within CU's Physics Department: one probed undergraduate students' familiarity with, and participation in, research; the other probed faculty members' experiences as research mentors to undergraduates. We describe the development of these instruments, our results, and our corresponding evidence-based recommendations for improving local access to undergraduate research experiences. Reflecting on our work, we make several connections to an institutional change framework and note how other universities and colleges might adapt our process.

physics.ed-ph↗

arXiv2015

The role of metacognition in troubleshooting: an example from electronics

Students in physics laboratory courses, particularly at the upper division, are often expected to engage in troubleshooting. Although there are numerous ways in which students may proceed when diagnosing a problem, not all approaches are equivalent in terms of providing meaningful insight. It is reasonable to believe that metacognition, by assisting students in making informed decisions, is an integral component of effective troubleshooting. We report on an investigation of authentic student troubleshooting in the context of junior-level electronics courses at two institutions. Think-aloud interviews were conducted with pairs of students as they attempted to repair a malfunctioning operational-amplifier circuit. Video data from the interviews have been analyzed to examine the relationship between each group's troubleshooting activities and instances of socially mediated metacognition. We present an analysis of a short episode from one interview.

physics.ed-ph↗

arXiv2015

Investigating student ownership of projects in an upper-division physics lab course

In undergraduate research experiences, student development of an identity as a scientist is coupled to their sense of ownership of their research projects. As a a first step towards studying similar connections in physics laboratory courses, we investigate student ownership of projects in a lasers-based upper-division course. Students spent the final seven weeks of the semester working in groups on final projects of their choosing. Using data from the Project Ownership Survey and weekly student reflections, we investigate student ownership as it relates to students' personal agency, self-efficacy, peer interactions, and complex affective responses to challenges and successes. We present evidence of students' project ownership in an upper-division physics lab. Additionally, we find that there is a complex relationship between student affect and their sense of ownership.

physics.ed-ph↗

arXiv2015

Model-Based Reasoning in the Upper-Division Physics Laboratory: Framework and Initial Results

We review and extend existing frameworks on modeling to develop a new framework that describes model-based reasoning in upper-division physics labs. Constructing and using models are core scientific practices that have gained significant attention within K-12 and higher education. Although modeling is a broadly applicable process, within physics education, it has been preferentially applied to the iterative development of broadly applicable principles (e.g., Newton's laws of motion in introductory mechanics). A significant feature of the new framework is that measurement tools (in addition to the physical system being studied) are subjected to the process of modeling. Think-aloud interviews were used to refine the framework and demonstrate its utility by documenting examples of model-based reasoning in the laboratory. When applied to the think-aloud interviews, the framework captures and differentiates students' model-based reasoning and helps identify areas of future research. The interviews showed how students productively applied similar facets of modeling to the physical system and measurement tools: construction, prediction, interpretation of data, identification of model limitations, and revision. Finally, we document students' challenges in explicitly articulating assumptions when constructing models of experimental systems and further challenges in model construction due to students' insufficient prior conceptual understanding. A modeling perspective reframes many of the seemingly arbitrary technical details of measurement tools and apparatus as an opportunity for authentic and engaging scientific sense-making.

physics.ed-ph↗

arXiv2014

Studying Expert Practices to Create Learning Goals for Electronics Labs

Laboratory courses for upper-division undergraduates often involve sophisticated equipment, relatively small class sizes, and extended hands-on projects. These courses present distinct challenges and opportunities for the physics education research community as these features are not often present in other undergraduate courses. Here, we focus on an upper-division lab-based electronics course. As a first step in establishing learning goals for upper-division electronics, we interviewed graduate students and faculty at the University of Colorado Boulder about the use of electronics in their own research labs. The content-specific nature of electronics courses parallels the hands-on experience of graduate student researchers, so focusing on the experiences of graduate students is ideal for informing lab course reform. From their interview responses, we developed a framework for classifying applications of electronics. We identify five types of use and four forms of interaction with electronics content that are consistently identified by faculty and graduate students. However, we see variations between faculty and graduate students regarding how electronics is learned.

physics.ed-ph↗

arXiv2014

An epistemology and expectations survey about experimental physics: Development and initial results

In response to national calls to better align physics laboratory courses with the way physicists engage in research, we have developed an epistemology and expectations survey to assess how students perceive the nature of physics experiments in the contexts of laboratory courses and the professional research laboratory. The Colorado Learning Attitudes about Science Survey for Experimental Physics (E-CLASS) evaluates students' epistemology at the beginning and end of a semester. Students respond to paired questions about how they personally perceive doing experiments in laboratory courses and how they perceive an experimental physicist might respond regarding their research. Also, at the end of the semester, the E-CLASS assesses a third dimension of laboratory instruction, students' reflections on their course's expectations for earning a good grade. By basing survey statements on widely embraced learning goals and common critiques of teaching labs, the E-CLASS serves as an assessment tool for lab courses across the undergraduate curriculum and as a tool for physics education research. We present the development, evidence of validation, and initial formative assessment results from a sample that includes 45 classes at 20 institutions. We also discuss feedback from instructors and reflect on the challenges of large-scale online administration and distribution of results.

physics.ed-ph↗

arXiv2013

Method for traveling-wave deceleration of buffer-gas beams of CH

Cryogenic buffer-gas beams are a promising method for producing bright sources of cold molecular radicals for cold collision and chemical reaction experiments. In order to use these beams in studies of reactions with controlled collision energies, or in trapping experiments, one needs a method of controlling the forward velocity of the beam. A Stark decelerator can be an effective tool for controlling the mean speed of molecules produced by supersonic jets, but efficient deceleration of buffer-gas beams presents new challenges due to longer pulse lengths. Traveling-wave decelerators are uniquely suited to meet these challenges because of their ability to confine molecules in three dimensions during deceleration and the versatility afforded by the analog control of the electrodes. We have created ground state CH($X^2Π$) radicals in a cryogenic buffer-gas cell with the potential to produce a cold molecular beam of $10^{11}$ mol./pulse. We present a general protocol for Stark deceleration of beams with large position and velocity spreads for use with a traveling-wave decelerator. Our method involves confining molecules transversely with a hexapole for an optimized distance before deceleration. This rotates the phase-space distribution of the molecular packet so that the packet is matched to the time varying phase-space acceptance of the decelerator. We demonstrate with simulations that this method can decelerate a significant fraction of the molecules in successive wells of a traveling-wave decelerator to produce energy-tuned beams for cold and controlled molecule experiments.

physics.chem-ph↗

arXiv2013

Incorporating learning goals about modeling into an upper-division physics laboratory experiment

Implementing a laboratory activity involves a complex interplay among learning goals, available resources, feedback about the existing course, best practices for teaching, and an overall philosophy about teaching labs. Building on our previous work, which described a process of transforming an entire lab course, we now turn our attention to how an individual lab activity on the polarization of light was redesigned to include a renewed emphasis on one broad learning goal: modeling. By using this common optics lab as a concrete case study of a broadly applicable approach, we highlight many aspects of the activity development and show how modeling was used to integrate sophisticated conceptual and quantitative reasoning into the experimental process through the various aspects of modeling: constructing models, making predictions, interpreting data, comparing measurements with predictions, and refining models. One significant outcome is a natural way to integrate an analysis and discussion of systematic error into a lab activity.

physics.ed-ph↗

arXiv2013

A search for varying fundamental constants using Hz-level frequency measurements of cold CH molecules

Many modern theories predict that the fundamental constants depend on time, position, or the local density of matter. We develop a spectroscopic method for pulsed beams of cold molecules, and use it to measure the frequencies of microwave transitions in CH with accuracy down to 3 Hz. By comparing these frequencies with those measured from sources of CH in the Milky Way, we test the hypothesis that fundamental constants may differ between the high and low density environments of the Earth and the interstellar medium. For the fine structure constant we find Δα/α= (0.3 +/- 1.1)*10^{-7}, the strongest limit to date on such a variation of α. For the electron-to-proton mass ratio we find Δμ/μ= (-0.7 +/- 2.2) * 10^{-7}. We suggest how dedicated astrophysical measurements can improve these constraints further and can also constrain temporal variation of the constants.

physics.atom-ph↗

arXiv2013

Development and results from a survey on students views of experiments in lab classes and research

The Colorado Learning Attitudes about Science Survey for Experimental Physics (E-CLASS) was developed as a broadly applicable assessment tool for undergraduate physics lab courses. At the beginning and end of the semester, the E-CLASS assesses students views about their strategies, habits of mind, and attitudes when doing experiments in lab classes. Students also reflect on how those same strategies, habits-of-mind, and attitudes are practiced by professional researchers. Finally, at the end of the semester, students reflect on how their own course valued those practices in terms of earning a good grade. In response to frequent calls to transform laboratory curricula to more closely align it with the skills and abilities needed for professional research, the E-CLASS is a tool to assess students' perceptions of the gap between classroom laboratory instruction and professional research. The E-CLASS has been validated and administered in all levels of undergraduate physics classes. To aid in its use as a formative assessment tool, E-CLASS provides all participating instructors with a detailed feedback report. Example figures and analysis from the report are presented to demonstrate the capabilities of the E-CLASS. The E-CLASS is actively administered through an online interface and all interested instructors are invited to administer the E-CLASS their own classes and will be provided with a summary of results at the end of the semester.

physics.ed-ph↗

arXiv2012

Development and Validation of the Colorado Learning Attitudes about Science Survey for Experimental Physics

As part of a comprehensive effort to transform our undergraduate physics laboratories and evaluate the impacts of these efforts, we have developed the Colorado Learning Attitudes about Science Survey for Experimental Physics (E-CLASS). The E-CLASS assesses the changes in students' attitudes about a variety of scientific laboratory practices before and after a lab course and compares attitudes with perceptions of the course grading requirements and laboratory practices. The E-CLASS is designed to give researchers insight into students' attitudes and also to provide actionable evidence to instructors looking for feedback on their courses. We present the development, validation, and preliminary results from the initial implementation of the survey in three undergraduate physics lab courses.

physics.ed-ph↗

arXiv2012

The Process of Transforming an Advanced Lab Course: Goals, Curriculum, and Assessments

A thoughtful approach to designing and improving labs, particularly at the advanced level, is critical for the effective preparation of physics majors for professional work in industry or graduate school. With that in mind, physics education researchers in partnership with the physics faculty at the University of Colorado Boulder have overhauled the senior-level Advanced Physics Lab course. The transformation followed a three part process of establishing learning goals, designing curricula that align with the goals, and assessment. Similar efforts have been carried out in physics lecture courses at the University of Colorado Boulder, but this is the first systematic research-based revision of one of our laboratory courses. The outcomes of this effort include a set of learning goals, a suite of new lab-skill activities and transformed optics labs, and a set of assessments specifically tailored for a laboratory environment. While the particular selection of advanced lab experiments varies widely between institutions, the overall transformation process, the learning goals, and the assessments are broadly applicable to the instructional lab community.

physics.ed-ph↗

arXiv2011

Rotational-state purity of Stark-decelerated molecular beams

Cold, velocity-controlled molecular beams consisting of a single quantum state promise to be a powerful tool for exploring molecular scattering interactions. In recent years, Stark deceleration has emerged as one of the main methods for producing velocity-controlled molecular beams. However, Stark deceleration is shown not to be effective at producing a molecular beam consisting of a single quantum state in many circumstances. Therefore, quantum state purity must be carefully considered when using Stark decelerated beams, particularly in collision experiments where contributions from all quantum states must be addressed.

physics.atom-ph↗