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Classical Doppler Effect in Some Accelerated Systems
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| Pengarang | : | - |
| Nama Majalah/Jurnal | : | The Physics Teacher |
| Volume / Edisi | : | 59 (No. 4) |
| Halaman | : | 239-242 |
| Abstrak | : | In this note, the classical Doppler shift for some accelerated mechanical systems is considered under a common graphical approach. In one dimension, we study uniform accelerated motion and simple harmonic motion. In two dimensions, uniform circular motion and pendular motion are considered. In each case, an elementary treatment shows that the period (and frequency) measured by an observer at rest depends on the straight paths of two consecutive signals between source and observer, with due consideration of the acceleration. |
Vector Symbolic Architectures as a Computing Framework for Emerging Hardware
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | Proceedings of the IEEE |
| Volume / Edisi | : | 110 (No. 10) |
| Halaman | : | 1538-1571 |
| Abstrak | : | This article reviews recent progress in the development of the computing framework vector symbolic architectures (VSA) (also known as hyperdimensional computing). This framework is well suited for implementation in stochastic, emerging hardware, and it naturally expresses the types of cognitive operations required for artificial intelligence (AI). We demonstrate in this article that the field-like algebraic structure of VSA offers simple but powerful operations on high-dimensional vectors that can support all data structures and manipulations relevant to modern computing. In addition, we illustrate the distinguishing feature of VSA, “computing in superposition,” which sets it apart from conventional computing. It also opens the door to efficient solutions to the difficult combinatorial search problems inherent in AI applications. We sketch ways of demonstrating that VSA are computationally universal. We see them acting as a framework for computing with distributed representations that can play a role of an abstraction layer for emerging computing hardware. This article serves as a reference for computer architects by illustrating the philosophy behind VSA, techniques of distributed computing with them, and their relevance to emerging computing hardware, such as neuromorphic computing. |
Apparatus Named After Our Academic Ancestors – V
| Pengarang | : | Thomas B. Greenslade, Jr. |
| Nama Majalah/Jurnal | : | The Physics Teacher |
| Volume / Edisi | : | 59 (No. 4) |
| Halaman | : | 236-238 |
| Abstrak | : | In the museum wing of the Greenslade house is a clock with a two-second pendulum about one meter long (Fig. 1). This ticks once per second, and every time it passes through dead center it completes an electrical circuit. When I came to Kenyon in 1964, this system was used to send signals to a series of telegraph relays, which ticked once per second. Students in the first-year laboratory used beats between the ticking sec-onds and the oscillation of the pendula they were studying in an era when stopwatches were expensive. This clock inspired me to write this article about physicists who have pendula named after them: Christiaan Huygens, Lionel Wilberforce, Henry Kater, Benjamin Robins, Leon Foucault, and Hugh Blackburn. |
A Foucault Pendulum Pilgrimage in Paris
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | The Physics Teacher |
| Volume / Edisi | : | 59 (No. 4) |
| Halaman | : | 232-235 |
| Abstrak | : | Most physics teachers have observed the majestic swings of a monumental pendulum at a science museum and have watched long enough to see the plane of oscillation slowly changing direction as Earth turns. The purpose of this article is to describe visits to Paris sites related to Jean Bernard Léon Foucault (1819-1868), with a special focus on the locations where he first developed and then demonstrated the apparatus now known as the Foucault pendulum. |
Stop-Motion Animation to Model the Analemma
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | The Physics Teacher |
| Volume / Edisi | : | 59 (No. 4) |
| Halaman | : | 230-231 |
| Abstrak | : | The Sun does not return to the same position in the sky every 24 hours. At local noon, for example, the Sun will appear higher in the sky as we move from winter to summer solstice. In addition, and perhaps more surprisingly, solar days (the roughly 24 hours between subsequent local noons) vary in length, causing the Sun to be east or west of its location 24 hours prior. Over a year, this variation traces out a figure 8, known as an analemma, as shown in Fig.1. It can also be seen in the sundial in Fig. 2, where the gnomon incorporates the analemma to produce an accurate reading of local time. |
Next-Gen Intelligent Situational Awareness Systems for Maritime Surveillance and Autonomous Navigation
| Pengarang | : | Nicola Forti |
| Nama Majalah/Jurnal | : | Proceedings of the IEEE |
| Volume / Edisi | : | 110 (No. 10) |
| Halaman | : | 1532-1537 |
| Abstrak | : | Today, the maritime domain is at the cusp of a new era, driven by technological advances in automation, robotics, multisensor perception, and artificial intelligence (AI), together with digitalization and connectivity. Smart ship infrastructure and technology, remotely controlled and autonomous ship operation to improve safety, security, cost efficiency, and sustainability are the future of maritime transportation [1], representing now the engine of 90% of global trade [2]. Ships will soon benefit from recent developments in sensors, telecommunications, and computing technologies to turn the smart shipping revolution into reality [3] and [4], as it has already happened for autonomous vehicles such as driverless cars, aerial drones, unmanned (or remotely piloted) aircraft, and underwater vehicles. |
Using Global Existing Fiber Networks for Environmental Sensing
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | Proceedings of the IEEE |
| Volume / Edisi | : | 110 (No. 11) |
| Halaman | : | 1853-1888 |
| Abstrak | : | We review recent advances in distributed fiber optic sensing (DFOS) and their applications. The scattering mechanisms in glass, which are exploited for reflectometry-based DFOS, are Rayleigh, Brillouin, and Raman scatterings. These are sensitive to either strain and/or temperature, allowing optical fiber cables to monitor their ambient environment in addition to their conventional role as a medium for telecommunications. Recently, DFOS leveraged technologies developed for telecommunications, such as coherent detection, digital signal processing, coding, and spatial/frequency diversity, to achieve improved performance in terms of measurand resolution, reach, spatial resolution, and bandwidth. We review the theory and architecture of commonly used DFOS methods. We provide recent experimental and field trial results where DFOS was used in wide-ranging applications, such as geohazard monitoring, seismic monitoring, traffic monitoring, and infrastructure health monitoring. Events of interest often have unique signatures either in the spatial, temporal, frequency, or wavenumber domains. Based on the temperature and strain raw data obtained from DFOS, downstream postprocessing allows the detection, classification, and localization of events. Combining DFOS with machine learning methods, it is possible to realize complete sensor systems that are compact, low cost, and can operate in harsh environments and difficult-to-access locations, facilitating increased public safety and smarter cities. |
Optical Switching in Future Fiber-Optic Networks Utilizing Spectral and Spatial Degrees of Freedom
| Pengarang | : | Agus Suwignyo |
| Nama Majalah/Jurnal | : | Proceedings of the IEEE |
| Volume / Edisi | : | 110 (No. 11) |
| Halaman | : | 1835-1852 |
| Abstrak | : | Forthcoming capacity scaling requirements of optical networks and advances in optical fiber communications beyond the omnipresent single-mode fiber operating over the conventional band introduces new opportunities and challenges for exploiting the expanded spectral and spatial resources available for fiber-optic network designs. The spectral and spatial degrees of freedom introduce utilization tradeoffs that can be leveraged under different applications. After briefly reviewing the supporting network building elements (emerging fiber types, multiplexers, optical switches, and amplifiers), we consider networking scenarios such as intra/inter datacenter, terrestrial, undersea, and wireless 5G/6G hauling networks and identify the best utilization plan and key attributes that can be harnessed by the offered spectral and spatial degrees of freedom for each scenario and how optical switching can be employed therein for traffic management. Networks supporting these scenarios are experiencing tremendous traffic growth pushing their existing implementations to their physical capacity-distance limits. New network builds must offer significant capacity multipliers in an efficient and cost-effective manner, requiring new switching solutions for supporting the unabated traffic growths foreseen in the years to come. We discuss how space-division multiplexed networks can help address this challenge in key communication scenarios. |
Photonic Lanterns, 3 D Waveguides, Multiplane Light Conversion, and Other Components That Enable Space-Division Multiplexing
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | Proceedings of the IEEE |
| Volume / Edisi | : | 110 (No. 11) |
| Halaman | : | 1821-1834 |
| Abstrak | : | Four-mode multiplexing and manipulation technologies are reviewed in the context of space-division multiplexing (SDM) optical communication systems. These are multiplane light conversion (MPLC), fused fiber devices, such as photonic lanterns and tapered fiber bundles, 3-D waveguides fabricated using ultrafast laser inscription, and free-space imaging systems. Each device has its unique strengths and use cases. MPLC can create very complex transformations between two arbitrary sets of spatial modes and leverages mature gray-scale lithographic techniques. Photonic lanterns and tapered fiber bundles are all-fiber devices that can convert beams on single-mode fiber inputs into spatial modes. The all-fiber construction leads to very low losses and high-power handling. 3-D waveguides are inscribed into a glass block using ultrashort lasers and can arbitrarily route light in 3-D. Finally, free-space systems using lenses can also relay many multicore and multimode beams through a single free-space device, such as a thin film filter or an optical isolator. These four technologies have enabled hero transmission experiments in the multimode, multicore, and multimode fiber. |
Using Reflection from a Pane of Glass to Copy a Drawing
| Pengarang | : | Zhang, Zhengjun,Cui, Qiurong |
| Nama Majalah/Jurnal | : | The Physics Teacher |
| Volume / Edisi | : | 59 (No. 5) |
| Halaman | : | 374-375 |
| Abstrak | : | The woodcut in Fig. 1 comes from a late 19th-century French book on the wonders of science. In it a girl is using the reflection from a transparent glass surface to copy a picture. |