An Annular Array MPT for Enhanced Generation of Omnidirectional SH Waves in a Plate

If guided wave transducers are fabricated in an annular array type, the excitation and measurement of target guided wave modes could be considerably enhanced (see, e.g., [1]). Accordingly, various annular array transducers have been developed, including those generating omnidirectional Lamb waves in a plate. Here, we newly consider an annular array type MPT (magnetostrictive patch transducer) to generate enhanced SH (shear-horizontal) waves in a plate. This annular array MPT is based on our earlier development of an omnidirectional SH wave MPT [2]. For wave field analysis by the annular array SH wave MPT, the strain response in a plate due to wave excitation by the MPT is calculated by using the Green’s function approach [3]. Using the analysis, an optimal configuration of the annular array MPT which can maximize the transducer output at the given frequency is determined. For the validation of numerical predictions, a series of experiments with varying frequencies were carried out and the numerical results were found to be in good agreement with the experimental results

Torsional Vibration Transduction in a Solid Shaft by MPTs

In this study, we aim to investigate the feasibility to use MPTs (Magnetostrictive Patch Transducers) for torsional vibration measurement in solid ferromagnetic cylinders. MPTs consisting of thin magnetostrictive patches, permanent magnets and a solenoid coil have been widely used for elastic wave transduction in the ultrasound frequency range [1] but they have been seldom used for sonic-frequency range vibration measurement, in spite of their unique wireless transduction characteristics. While a MPT was used in Ref. [2] to perform torsional modal testing in a hollow cylinder or a pipe having relatively small torsional rigidity, no investigation has been reported yet on the use of MPTs in “solid” “ferromagnetic” shafts, common torsional power carrying elements in machines.While we will be mainly focused here on the torsional wave measurement in stationary shafts, the MPT-based torsional measurement can be also applied to rotating shafts. Because the torsional rigidities of solid shafts are much larger than those of hollow cylinders of the same radii, it is important to find optimal MPT configurations, such as the optimal number of rectangular patches to be installed around the surface of a solid shaft. Thereby, we performed numerical investigations and accordingly designed a series of experiments for torsional vibration testing in steel shafts. The actual modal testing experiments with the designed MPTs were found to predict the torsional Eigen-frequencies and Eigen-modes that agree well with the theoretical predictions. Also the relation between the measured vibration signals from MPTs and those from strain gages was checked experimentally and in fact, the experimental result favorably agreed with the theoretical prediction. Potential applications of the MPT-based torsional vibration measurement technique in rotating solid shafts for structural health monitoring are also briefly discussed

Nasal Chondromesenchymal Hamartoma: CT and MR Imaging Findings

We report CT and MR imaging findings for a case of nasal chondromesenchymal hamartoma occurring in a 19-month-old boy. A nasal chondromesenchymal hamartoma is a rare benign pediatric hamartoma that can simulate malignancy. Although rare, knowledge of this entity is essential to avoid potentially harmful therapies

KMT-2016-BLG-1107: A New Hollywood-Planet Close/Wide Degeneracy

We show that microlensing event KMT-2016-BLG-1107 displays a new type of degeneracy between wide-binary and close-binary Hollywood events in which a giant-star source envelops the planetary caustic. The planetary anomaly takes the form of a smooth, two-day "bump" far out on the falling wing of the light curve, which can be interpreted either as the source completely enveloping a minor-image caustic due to a close companion with mass ratio $q=0.036$, or partially enveloping a major-image caustic due to a wide companion with $q=0.004$. The best estimates of the companion masses are both in the planetary regime ($3.3^{+3.5}_{-1.8}\,M_{\rm jup}$ and $0.090^{+0.096}_{-0.037}\,M_{\rm jup}$) but differ by an even larger factor than the mass ratios due to different inferred host masses. We show that the two solutions can be distinguished by high-resolution imaging at first light on next-generation ("30m") telescopes. We provide analytic guidance to understand the conditions under which this new type of degeneracy can appear.Comment: 23 pages, 7 figures, accepted for publication in A

KMT-2018-BLG-1990Lb: A Nearby Jovian Planet From A Low-Cadence Microlensing Field

We report the discovery and characterization of KMT-2018-BLG-1990Lb, a Jovian planet $(m_p=0.57_{-0.25}^{+0.79}\,M_J)$ orbiting a late M dwarf $(M=0.14_{-0.06}^{+0.20}\,M_\odot)$, at a distance (D_L=1.23_{-0.43}^{+1.06}\,\kpc), and projected at $2.6\pm 0.6$ times the snow line distance, i.e., a_{\rm snow}\equiv 2.7\,\au (M/M_\odot), This is the second Jovian planet discovered by KMTNet in its low cadence ($0.4\,{\rm hr}^{-1}$) fields, demonstrating that this population will be well characterized based on survey-only microlensing data.Comment: 24 pages, 7 figures, 4 table