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A simpler graphical solution and an approximate formula for energy eigenvalues in finite square quantum wells
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| Pengarang | : | - |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 88 (No. 11) |
| Halaman | : | 1019-1022 |
| Abstrak | : | The computation of allowed energy levels for a particle bounded to a finite square well potential is ubiquitous in modern physics and introductory quantum mechanics textbooks. For stationary bound states, the matching conditions for the wave functions lead to a pair of transcendental equations whose roots correspond to the energy eigenvalues. However, the graphical solutions available do not make clear the dependence of the energies on the well potential parameters. In this note, I present a simpler graphical solution involving only one dimensionless parameter that determines a straight-line crossing identical sinusoidal curves. I then reduce this solution to a single cosine curve, and from a three-point interpolation, I derive an approximate formula for all energy levels valid for any square quantum well and that demands only a pocket calculator. |
PENGELOLAAN ARSIP VITAL: SUATU PENDEKATAN
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | Berita Arsip Nasional RI |
| Volume / Edisi | : | -/36, JUNI (No. 36) |
| Halaman | : | 13-22 |
| Abstrak | : | - |
Fluorescence lifetime measurements with simple correction for instrument temporal response in the advanced undergraduate laboratory
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 88 (No. 11) |
| Halaman | : | 1012-1018 |
| Abstrak | : | Observation of time-dependent luminescence from excited states with a wide range of lifetimes allows students to explore the connection between selection rules and transition rates. It is fairly simple to measure microsecond and longer lifetimes with equipment common to undergraduate programs, because the instrument response time of even modest bandwidth systems is insignificant on microsecond and longer time scales. The measurement of nanosecond lifetimes, however, is more challenging, because the instrument response time is comparable to the lifetimes being measured. In this case, the instrument temporal response must be deconvolved from the observed luminescence signals in order to extract the actual excited state lifetime. We describe a method for measuring nanosecond fluorescence lifetimes in the advanced undergraduate laboratory that uses real-time analog luminescence signals instead of traditional photon counting techniques. The detection electronics of this method are fairly simple, consisting of an oscilloscope monitoring the time-dependent output of an inexpensive silicon photomultiplier. We introduce a simple and transparent method for students to characterize the instrument response and deconvolve it from the observed luminescence signals, yielding measured nanosecond fluorescence lifetimes in good agreement with the corresponding literature values obtained by time-correlated single photon counting. The limitations of silicon photomultipliers for this method of measuring nanosecond lifetimes are discussed in detail. Application of this treatment to decay processes that are not single exponential is also discussed. |
MANAJEMEN ARSIP PERUSAHAAN SEBUAH PENDEKATAN SISTEM (II)
| Pengarang | : | Sauki Hadiwardoyo |
| Nama Majalah/Jurnal | : | Berita Arsip Nasional RI |
| Volume / Edisi | : | -/36, JUNI (No. 36) |
| Halaman | : | 1-12 |
| Abstrak | : | - |
Exploring delay dynamics with a programmable electronic delay circuit
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 88 (No. 11) |
| Halaman | : | 1006-1011 |
| Abstrak | : | Delay dynamics occur in a wide variety of natural and man-made systems. Even simple delay systems can generate complex dynamics whose exploration is rewarding. To allow such exploration as part of advanced undergraduate laboratory courses and be able to utilize systems that operate at convenient timescales, it is necessary to delay analog signals by several milliseconds. In this paper, we describe an implementation of a programmable digital circuit capable of delaying DC-coupled analog signals up to 262 ms at a 1 MHz sampling rate. The initial history of the system may also be arbitrarily programmed, enabling the study of transient behavior. As an application, we discuss the use of this programmable delay in a feedback circuit that produces period-four triangular solutions, in complete agreement with theoretical predictions. |
Landau levels, edge states, and gauge choice in 2D quantum dots
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 88 (No. 11) |
| Halaman | : | 986-1005 |
| Abstrak | : | We examine the behavior of a charged particle in a two dimensional quantum dot in the presence of a magnetic field. Emphasis is placed on the high magnetic field regime. Compared to free space geometry, confinement in a dot geometry provides a more realistic system where edge effects arise naturally. It also serves to remove the otherwise infinite degeneracy due to the magnetic field; nonetheless, as described in this paper, additional ingredients are required to produce sensible results. We treat both circular and square geometries, and in the latter, we explicitly demonstrate the gauge invariance of the energy levels and wave function amplitudes. The characteristics of bulk states closely resemble those of free space states. For edge states, with sufficiently high quantum numbers, we achieve significant differences in the square and circular geometries. Both circular and square geometries are shown to exhibit level crossing phenomena, similar to parabolic dots, where the confining potential is a parabolic trap. Confinement effects on the probability current are also analyzed; it is the edge states that contribute non-zero current to the system. The results are achieved using straightforward matrix mechanics, in a manner that is accessible to novices in the field. On a more pedagogical note, we also provide a thorough review of the theory of single electron Landau levels in free space and illustrate how the introduction of surfaces naturally leads to a more physically transparent description of a charged particle in a magnetic field. |
A completely algebraic solution of the simple harmonic oscillator
| Pengarang | : | M. Rushka |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 88 (No. 11) |
| Halaman | : | 976-985 |
| Abstrak | : | We present a full algebraic derivation of the wavefunctions of a simple harmonic oscillator. This derivation illustrates the abstract approach to the simple harmonic oscillator by completing the derivation of the coordinate-space or momentum-space wavefunctions from the energy eigenvectors. It is simple to incorporate into the undergraduate and graduate curricula. We provide a summary of the history of operator-based methods as they are applied to the simple harmonic oscillator. We present the derivation of the energy eigenvectors along the lines of the standard approach that was first presented by Dirac in 1947 (and is modified slightly here in the spirit of the Schrödinger factorization method). We supplement it by employing the appropriate translation operator to determine the coordinate-space and momentum-space wavefunctions algebraically, without any derivatives. |
PERKEMBANGAN KEARSIPAN DI JAWA TENGAH
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | Berita Arsip Nasional RI |
| Volume / Edisi | : | -/34, DESEMBER-MARET (No. 34) |
| Halaman | : | 55-63 |
| Abstrak | : | - |
MANAJEMEN ARSIP PEMERINTAH DAERAH (SUATU TINJAUAN APRESIASI KEARSIPAN PADA PEMERINTAH DAERAH TINGKAT I NUSA TENGGARA TIMUR)
| Pengarang | : | Kantus Sabinus |
| Nama Majalah/Jurnal | : | Berita Arsip Nasional RI |
| Volume / Edisi | : | -/34, DESEMBER-MARET (No. 34) |
| Halaman | : | 48-54 |
| Abstrak | : | - |
Physical pendulum model: Fractional differential equation and memory effects
| Pengarang | : | L. N. Gonçalves |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 88 (No. 11) |
| Halaman | : | 962-975 |
| Abstrak | : | A detailed analysis of pendular motion is presented. Inertial effects, self-oscillation, and memory, together with non-constant moment of inertia, hysteresis, and negative damping are shown to be required for the comprehensive description of the free pendulum oscillatory regime. The effects of very high initial amplitudes, friction in the roller bearing axle, drag, and pendulum geometry are also analyzed and discussed. A model consisting of a fractional differential equation fits and explains high resolution and long-time experimental data gathered from standard action-camera videos. |