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Radiation of the electromagnetic field beyond the dipole approximation
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| Pengarang | : | - |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 86 (No. 10) |
| Halaman | : | 727–732 |
| Abstrak | : | An expression for the intensity of electromagnetic radiation is derived up to the order after the dipole approximation. Our approach is based on the fundamental equations taught in an introductory course in classical electrodynamics, and the derivation is carried out using straightforward mathematical transformations. |
Kepler's equation and some of its pearls
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 86 (No. 11) |
| Halaman | : | 849–858 |
| Abstrak | : | Kepler's equation, rarely discussed in undergraduate textbooks, was enunciated by Johannes Kepler in his Astonomia Nova, published in 1609, much before the advent of the integral and differential calculus. The search for its solutions challenged the minds of brilliant researchers like Newton, Lagrange, Cauchy, and Bessel, among others. In this work, we start with a standard derivation of Kepler's equation and emphasize how it gave rise to new mathematics, like approximation methods, Bessel functions, and complex analysis. Then we apply it in two non-trivial examples. In the first one, we compute the distance reached by a projectile launched from a point at the equator of the rotating Earth. This result could be used to prove the rotation of the Earth without the need of a Foucault pendulum. In the second example, we show how two astronauts moving around the Earth along the same circular orbit could exchange a sandwich. These two apparently innocent problems are quite involved because their solutions demand the calculations of the time of flight. |
"It's Not Easy, But It Needs to Be Done": Educators' Perceptions of Preparedness to Teach Students With Internalizing Mental Health Needs
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | Journal of Teacher Education |
| Volume / Edisi | : | 74 (No. 3) |
| Halaman | : | 245-259 |
| Abstrak | : | This mixed methods study surveyed 209 K-12 special education teachers about their perceptions of preparedness to teach students with mental health needs that manifest internally (e.g., quiet distress, withdrawal, excessive worry). We used a construct-modeling approach to develop the survey instrument and establish evidence of validity, reliability, and fairness, and it included both multiple-choice questions, used for descriptive and regression analyses, and open-ended items, coded to identify key themes. Results indicated that special educators generally had low perceptions of preparedness to support students with internalizing needs. In addition, we found that participants possessed critical misconceptions about research based practices for supporting students with these needs in the school context, and that differences in perceptions of preparedness were associated with teachers' race and the grade level at which they taught. |
Self-torque and angular momentum balance for a spinning charged sphere
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 86 (No. 11) |
| Halaman | : | 839–848 |
| Abstrak | : | Angular momentum balance is examined in the context of the electrodynamics of a spinning charged sphere, which is allowed to possess any variable angular velocity. We calculate the electric and magnetic fields of the (hollow) sphere, and express them as expansions in powers of τ/tc ? 1, the ratio of the light-travel time τ across the sphere and the characteristic time scale tc of variation of the angular velocity. From the fields we compute the self-torque exerted by the fields on the sphere, and argue that only a piece of this self-torque can be associated with radiation reaction. Then we obtain the rate at which angular momentum is radiated away by the shell, and the total angular momentum contained in the electromagnetic field. With these results we demonstrate explicitly that the field angular momentum is lost in part to radiation and in part to the self-torque; angular momentum balance is thereby established. Finally, we examine the angular motion of the sphere under the combined action of the self-torque and an additional torque supplied by an external agent. |
ARSIP SEBAGAI SALAH SATU ALAT PENDUKUNG PENGAMBILAN KEPUTUSAN SUATU ORGANISASI
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | Berita Arsip Nasional RI |
| Volume / Edisi | : | -/25, MARET (No. 25) |
| Halaman | : | 13-18 |
| Abstrak | : | - |
Challenges and Tradeoffs of "Good" Teaching: The Pursuit of Multiple Educational Outcomes
| Pengarang | : | Budi Wihandono |
| Nama Majalah/Jurnal | : | Journal of Teacher Education |
| Volume / Edisi | : | 74 (No. 3) |
| Halaman | : | 229-244 |
| Abstrak | : | The pursuit of multiple educational outcomes makes teaching a complex craft subject to potential conflicts and competing commitments. Using a data set in which teachers were randomly assigned to classes paired with videotaped lessons, we both document and unpack such a tradeoff. Upper-elementary teachers who excel at raising students' math test scores often are less successful at improving student-reported engagement in class (and vice versa). Furthermore, teaching practices that improve test scores (e.g., cognitively demanding content) can simultaneously decrease engagement. At the same time, paired quantitative and qualitative analyses reveal two areas of practice that support both outcomes: active mathematics with opportunities for hands-on participation, physical movement, and peer interaction; and established routines and procedures to proactively organize the classroom. In addition to guiding practice-based teacher education, our sequential, explanatory mixed-methods analysis can serve as a model for rigorously studying and identifying dimensions of "good" teaching that promote multidimensional student development. |
PROBLEM PENERTIBAN ARSIP: PENGALAMAN BNI 1946
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | Berita Arsip Nasional RI |
| Volume / Edisi | : | -/25, MARET (No. 25) |
| Halaman | : | 9-12 |
| Abstrak | : | - |
A hybrid approach for using programming exercises in introductory physics
| Pengarang | : | C. M. Orban |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 86 (No. 11) |
| Halaman | : | 831–838 |
| Abstrak | : | Incorporating computer programming exercises into introductory physics is a delicate task that involves a number of choices that may have an effect on student learning. We present a “hybrid” approach that speaks to a number of common concerns regarding cognitive load which arise when using programming exercises in introductory physics classes where many students are absolute beginner programmers. This “hybrid” approach provides the student with a highly interactive web-based visualization, not unlike a PhET or Physlet interactive, but importantly the student is shown only the subset of the code where the initial conditions are set and the system variables are evolved. We highlight results from a coding activity that resembles the classic game Asteroids. The goals of this activity are to show how a simple 1D code can be modified into a 2D code, and to reinforce ideas about the relationship between force, velocity, and acceleration vectors. Survey results from four semesters of introductory physics classes at the Ohio State University's Marion campus, in which a high percentage of the students are weak or absolute beginner programmers, provide evidence that most students can complete coding tasks without severe difficulty. |
Teacher Professional Development and Student Reading in Middle and High School: A Systematic Review and Meta-Analysis
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | Journal of Teacher Education |
| Volume / Edisi | : | 74 (No. 3) |
| Halaman | : | 214-228 |
| Abstrak | : | This systematic review investigates the effect of teacher professional development (TPD) on adolescent students' reading achievement in middle and high school, A systematic search of TPD and student reading achievement studies ( 1975-2020) identified 15 medium-quality articles meeting this study's inclusion criteria. A meta-analysis of 14 of these studies corrected by Hedges' g showed that TPD on student reading was associated with a small overall effect of g = 0.062, p < .05 on student reading outcomes. However, the effect size was moderated by delivery of the TPD, TPD hours, student population, and assessment. None of the 14 studies reported TPD theory-driven quality indicators for TPD delivery ( e.g., school support, use of technology, and promotion of self-reflection or reported measures of teacher change). Conclusion of findings in literacy TPD includes the need for TPD theory-driven studies. |
Relativistic description of the photoelectric effect
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 86 (No. 11) |
| Halaman | : | 825–830 |
| Abstrak | : | Einstein's famous explanation of the photoelectric effect is addressed using the Minkowski four-vector formalism. This formalism deals with energy and linear momentum simultaneously and it is Lorentz covariant. The energy and momentum equations for both electron emission and electron braking are obtained in the lab frame S. It is then shown that the energy and momentum equations for electron emission and electron braking in a second inertial frame ?′ are linear combinations of the corresponding equations in the original frame S, according to the principle of relativity. Although the photoelectric effect is basically a non-relativistic phenomenon, the approach presented here may provide new insights for both instructors and students. |