PENGGUNAAN MEDIA JARUM BERGOYANG DALAM MATERI MEDAN MAGNET UNTUK MENINGKATKAN PEMAHAMAN KONSEP PESERTA DIDIK

The purpose of this paper is to further improve students' understanding of the concept of magnetic fields, by creating media that can show the characteristics of magnetic fields, which are abstract quantities and vector quantities. This media is designed in addition to being able to prove the existence of an abstract magnetic field, it can also show the direction of the magnetic lines of force, show the shape of the curved trajectory of the magnetic lines of force, and can directly determine the magnetic poles if the magnet is made by electromagnetic means. While the media that is often used so far can only prove its existence. The process of making this media through three stages, namely; design, assemble and test. This media is designed by using a needle that is placed above the water and brought close to a magnet with the media term "Jarum Bergoyang". The assembly process uses simple tools and easily available materials. The testing process was carried out on magnetic practicum activities by class IX-C students of SMP Negeri 2 Saketi 2015. The results of the practicum can be concluded that swaying needle media can be used to prove the existence of a magnetic field, can determine the direction of magnetic force lines, can show the shape of the line trajectory. magnetic lines of force and can directly show the magnetic poles of the coil. ABSTRAKTujuan dari penulisan ini adalah untuk lebih meningkatkan pemahaman siswa terhadap konsep medan magnet, dengan membuat media yang dapat menunjukan karakteristik medan magnet, yang merupakan besaran yang bersifat abstrak dan besaran vektor. Media ini dirancang selain bisa membuktikan keberadaan medan magnet yang bersifat abstrak, juga dapat menunjukan arah garis-garis gaya magnet, menunjukan bentuk lintasan lengkung garis-garis gaya magnet, dan bisa secara langsung menentukan kutub-kutub magnet apabila magnetnya itu dibuat dengan cara elektromagnetik. Sementara media yang sering dipakai selama ini hanya dapat membuktikan keberadaannya saja. Proses pembuatan media ini melalui tiga tahapan yaitu ; merancang, merakit dan menguji. Media ini dirancang dengan menggunakan jarum yang ditempatkan di atas air dan didekatkan dengan magnet dengan istilah media jarum bergoyang. Proses perakitan menggunakan alat yang sederhana dan bahan yang mudah didapat. Proses pengujian dilakukan pada kegiatan praktikum kemagnetan oleh siswa kelas IX-C SMP Negeri 2 Saketi Tahun 2015. Hasil praktikum dapat disimpulkan bahwa media jarum bergoyang dapat digunakan untuk membuktikan adanya medan magnet, dapat menentukan arah garis-garis gaya magnet, dapat menunjukan bentuk lintasan garis-garis gaya magnet dan dapat secara langsung menunjukan kutub-kutub magnet kumparan.

Design and Performance Evaluation of a Single-Phase Driven Ultrasonic Motor Using Bending-Bending Vibrations

An ultrasonic motor as a kind of smart material drive actuator has potential in robots, aerocraft, medical operations, etc. The size of the ultrasonic motor and complex circuit limits the further application of ultrasonic motors. In this paper, a single-phase driven ultrasonic motor using Bending-Bending vibrations is proposed, which has advantages in structure miniaturization and circuit simplification. Hybrid bending vibration modes were used, which were excited by only single-phase voltage. The working principle based on an oblique line trajectory is illustrated. The working bending vibration modes and resonance frequencies of the bending vibration modes were calculated by the finite element method to verify the feasibility of the proposed ultrasonic motor. Additionally, the output performance was evaluated by experiment. This paper provides a single-phase driven ultrasonic motor using Bending-Bending vibrations, which has advantages in structure miniaturization and circuit simplification.

A novel method for dendrochronology of large historical wooden objects using line trajectory X-ray tomography

Dendrochronology is an essential tool to determine the date and provenance of wood from historical art objects. As standard methods to access the tree rings are invasive, X-ray computed tomography (CT) has been proposed for non-invasive dendrochronological investigation. While traditional CT can provide clear images of the inner structure of wooden objects, it requires their full rotation, imposing strong limitations on the size of the object. These limitations have previously encouraged investigations into alternative acquisition trajectories, including trajectories with only linear movement. In this paper, we use such a line-trajectory (LT) X-ray tomography technique to retrieve tree-ring patterns from large wooden objects. We demonstrate that by moving a wooden artifact sideways between the static X-ray source and the detector during acquisition, sharp reconstruction images of the tree rings can be produced. We validate this technique using computer simulations and two wooden test planks, and demonstrate it on a large iconic chest from the Rijksmuseum collection (Amsterdam, The Netherlands). The LT scanning method can be easily implemented in standard X-ray imaging units available at museum research facilities. Therefore, this scanning technique represents a major step towards the standard implementation of non-invasive dendrochronology on large wooden cultural heritage objects.

Effect of vibrating feeder pan geometry on radiometric separator performance

The article offers justifies the optimized shape for the vibrating feeder pan of a radiometric separator, which ensures the maximum travelling speed and uniform flow of ore material in the zone of radiation and recording. Three shapes of pans are discussed: rectangular, parabolic and triangular. It is found that motion of ore material along an inclined rectangular-shape pan is straight-linear. Distribution of ore particles along the width of the channel, which governs the scatter of the motion trajectories relative to the central axis of the channel, depends on the runoff point of particles from the outlet feeder. Proposed for the description of the motion trajectory of ore particles along an inclined channel of parabolic shape, the mathematical model demonstrates the curved and pendulum-wise motion of an ore particle with the attenuating amplitude. The motion of an ore particle in an inclined pan with the triangular-shape channel features the minimized scatter of motion trajectories relative to the central axis of the channel. The analysis of ore motion along vibrating feeder pans with different shape channels is carried out in Rocky DEM environment with regard to interaction of ore particles with the pan surface and with each other. The simulation modeling has proved the conclusions on the efficiency of the triangularshape profile of the vibrating feeder pan as it ensures uniform single-row flow of ore particles along the straight-line trajectory. The triangular shape of the pan contributes to the increased travelling speed of ore particles and, accordingly, to the enhanced capacity of the separator. The radiometric separator efficiency can be increased 1.5 times by changing from the parabolicshape channels to the triangular-shape profiles of vibrating feeder pans at the other operating conditions of radiometric separators being equal.

Optical wave-packet with nearly-programmable group velocities

During the process of Bessel beam generation in free space, spatiotemporal optical wave-packets with tunable group velocities and accelerations can be created by deforming pulse-fronts of injected pulsed beams. So far, only one determined motion form (superluminal or luminal or subluminal for the case of group velocity; and accelerating or uniform-motion or decelerating for the case of acceleration) could be achieved in a single propagation path. Here we show that deformed pulse-fronts with well-designed axisymmetric distributions (unlike conical and spherical pulse-fronts used in previous studies) allow us to obtain nearly-programmable group velocities with several different motion forms in a single propagation path. Our simulation shows that this unusual optical wave-packet can propagate at alternating superluminal and subluminal group velocities along a straight-line trajectory with corresponding instantaneous accelerations that vary periodically between positive (acceleration) and negative (deceleration) values, almost encompassing all motion forms of the group velocity in a single propagation path. Such unusual optical wave-packets with nearly-programmable group velocities may offer new opportunities for optical and physical applications.

Fabrication of High-Quality Polymer Composite Frame by a New Method of Fiber Winding Process

Polymer composite frame has been frequently used in the main structural body of vehicles in aerospace, automotive, etc., applications. Manufacturing of complex curved composite frame suffer from the lack of accurate and optimum method of winding process that lead to preparation of uniform fiber arrangement in critical location of the curved frame. This article deals with the fabrication of high-quality polymer composite frame through an optimal winding of textile fibers onto a non-bearing core frame using a fiber-processing head and an industrial robot. The number of winding layers of fibers and their winding angles are determined based on the operational load on the composite structure. Ensuring the correct winding angles and thus also the homogeneity of fibers in each winding layer can be achieved by using an industrial robot and by definition of its suitable off-line trajectory for the production cycle. Determination of an optimal off-line trajectory of the end-effector of a robot (robot-end-effector (REE)) is important especially in the case of complicated 3D shaped frames. The authors developed their own calculation procedure to determine the optimal REE trajectory in the composite manufacturing process. A mathematical model of the winding process, matrix calculus (particularly matrices of rotations and translations) and an optimization differential evolution algorithm are used during calculation of the optimal REE trajectory. Polymer composites with greater resistance to failure damage (especially against physical destruction) can be produced using the above mentioned procedure. The procedure was successfully tested in an experimental composite laboratory. Two practical examples of optimal trajectory calculation are included in the article. The described optimization algorithm of REE trajectory is completely independent of the industrial robot type and robot software tools used and can also be used in other composite manufacturing technologies.