Inductive measurements of third-harmonic voltage and critical current density in bulk superconductors

We propose an inductive method to measure critical current density $J_c$ in bulk superconductors. In this method, an ac magnetic field is generated by a drive current $I_0$ flowing in a small coil mounted just above the flat surface of superconductors, and the third-harmonic voltage $V_3$ induced in the coil is detected. We present theoretical calculation based on the critical state model for the ac response of bulk superconductors, and we show that the third-harmonic voltage detected in the inductive measurements is expressed as $V_3= G_3\omega I_0^2/J_c$, where $\omega/2\pi$ is the frequency of the drive current, and $G_3$ is a factor determined by the configuration of the coil. We measured the $I_0$-$V_3$ curves of a melt-textured $\rm YBa_2Cu_3O_{7-\delta}$ bulk sample, and evaluated the $J_c$ by using the theoretical results.Comment: 3 pages, 1 figure, submitted to Appl. Phys. Let

A hybrid active filter for damping of harmonic resonance in industrial power systems

This paper proposes a hybrid active filter for damping of harmonic resonance in industrial power systems. The hybrid filter consists of a small-rated active filter and a 5th tuned passive filter. The active filter is characterized by detecting the 5th harmonic current flowing into the passive filter. It is controlled in such a way as to behave as a negative or positive resistor by adjusting a feedback gain from a negative to positive value, and vice versa. The negative resistor presented by the active filter cancels a positive resistor inherent in the passive filter, so that the hybrid filter acts as an ideal passive filter with infinite quality factor. This significantly improves damping the harmonic resonance, compared with the passive filter used alone. Moreover, the active filter acts as a positive resistor to prevent an excessive harmonic current from flowing into the passive filter. Experimental results obtained from a 20 kW laboratory model verify the viability and effectiveness of the hybrid active filter proposed in this paper </p

An active learning program of earth science study using observation of sediments and flume experiments in the laboratory: an example in a refresher course for teacher’s license renewal

Two hours laboratory program including flume experiments and an observation activity of strata in the laboratory was done as a refresher course for teacher’s license. The aim of the course is to gain the knowledge of sedimentation and to improve experimental technique. Understanding the transportation and sedimentation of sediments through experiments and observation of recent deposits enable teachers who take the course to understand that geological phenomena are ongoing process and to get the actualistic thinking skill.本講習内容の事前の検討に際して，科学研究費補助金基盤研究（課題番号25242015, 26350235）を使用した

Geoscience Teaching Using Local Geological Materials (8): Features of composition, shape, and size of river bed gravels of the Ashida-gawa River in Hiroshima prefecture from the aspect of terrain property in the southern part of Chugoku district

The significance of conservation of geodiversity in global environmental conservation has found attention in Japan in recent years. The water and rock cycles, as a part of the supracrustal cycle of materials, have a crucial role in the formation and conservation of geodiversity. The 5th grade science curriculum includes a description of an ideal model on the function of running water in rivers, where it is theorized that gravel in the river become smaller and rounder as they travel farther from the river head. However, the situation of many rivers in this respect do not fit well into the ideal model. Therefore, in the light of the need to acquaint students with actual conditions in rivers, it is necessary to collect actual data on the effect of running river water on gravel, for inclusion in these curriculums. In this study, we determined the compositions, grain sizes, and shapes of river gravels at seven localities along the Ashidagawa River in the eastern part of Hiroshima Prefecture. We explored the relationship between the features of the gravels and the geology and geomorphology of the river basin. The results indicate the following: 1) Channel morphology can affect gravel composition; 2) the size and roundness of gravel varies as a function of channel slope; and 3) it is necessary to consider that huge boulders are transported by running water only with difficulty and are, thus, rounded on site by sediment particles suspended in the running water. The topography of the southern part of the Chugoku region, through which the Ashida-gawa River runs, is characterized by a stepped terrain, unlike that in an ideal model. Therefore, the features of the gravel in the Ashida-gawa River are typical examples of those of bed sediments of a river running through a stepped terrain.本研究の一部は日本学術振興会科研費JP16K00966，JP17H00820の助成を受けて行われた

Salivary Mucocele in a Laboratory Beagle

The histologic characteristics of a salivary mucocele in a beagle used in a toxicity study are described in this report. A pale yellowish cyst under the mandibular skin containing frothy mucus was observed at necropsy. Microscopically, numerous villous projections arose from the internal surface of the cyst and were lined by stratified epithelial-like macrophages, which were immunopositive for macrophage scavenger receptor A. A ruptured sublingual interlobar duct connected to the lumen was observed near the cyst. Luminal amorphous material showed a positive reaction with Alcian blue and periodic acid-Schiff staining as did mucin in the sublingual gland. Ultrastructurally, the epithelial-like macrophages had numerous vacuoles containing electron-lucent material, which was presumed to be lysosomal in origin, and had pseudopods on their cell surfaces interdigitating with those on the adjacent cells. This case report helps to understand the diversity of the background findings in beagles used in toxicity studies

A learning program to promote understanding of the spatial arrangement of strata: A preliminary study of the use of learning materials at different spatial scales

The purpose of this study is to develop a learning program for estimating the spatial arrangement of the strata based on the measurement of strike and dip by using a desk scale geological block model as an adjunct to field observation practice. In order to estimate the extent of the strata at two outcrops of an isolated small island-like landscape in Fujie, Fukuyama, we devised a learning activity to compare the boundaries of the strata with the actual extent of the strata by drawing the boundaries on the surface of a small square sponge as a model of the island-like landscape. The students' impressions of this method were positive.本研究の一部はJSPS科研費19K03144,19K02708および17H01980の助成を受けて行われた

Implementation of a new specific program for training curators at Hiroshima University

博物館法施行規則の改正に伴い，2012年4月から学芸員資格取得のために修得すべき科目が大幅に変更となった。学芸員資格取得の歴史においてはきわめて大きな変更である。本学では，これに対応するため，各学部の学芸員資格取得特定プログラムを統合し，全学の学生を対象とする新課程に移行した。本稿では，本学が新たに採用した4学期制（ターム制）を含め，今回の変更が受講や資格取得にどのような影響を及ぼしたのか，統計データの分析を通じて考察した。新課程移行の前後で，プログラム登録者数，資格取得者数は大幅に減少し，取得率も大きく低下した。こうした現象は特定の学部，分野の変化に基づくものではなく，旧課程においてプログラム登録の主体となってきた全ての学部に共通する。分析を通じて，大幅な必要単位数の増加，全学を対象としたプログラムへの変更，2学期制から4学期制（ターム制）への変更など，複数の要因が関連して，各学部における専門の修得と学芸員資格取得を両立させることが困難な状況が生じていることが推定された。As a result of the revision of Museum Law Enforcement Rules, the subjects that must be completed to acquire the curator qualification have changed significantly since April 2012, which constitutes a major change in the history of this qualification. To cope with this change, we integrated the curator qualification specific programs of each faculty into a new course for students of all universities. In this paper, through statistical data analysis, we examined the impact of this change on attendance trends, including the term system newly adopted by Hiroshima University. Before and after the transition to the new course, the number of program registrants and qualifications greatly decreased, and the acquisition rate has also declined significantly. These phenomena were not based on changes in specific faculties or fields, but are common to all faculties subject to program registration during the old course. Through this analysis, we presumed that several factors, such as the great increase in the required number of credits, the change to the program for the whole school, and the change from a two-semester system to the four-semester system, were all interrelated to each other, which make it difficult to achieve both specialized and curator qualifications.本稿は，2018年6月22日に香川大学で開催された第13回日本博物科学会で口頭発表した藤野次史・青木孝夫・清水則雄・菅村 亨・本多博之・山口富美夫・山崎博史・吉田将之「広島大学における新課程実施後の学芸員資格取得状況について」を元に，新たなデータを加えて考察したものである

Newly Identified Oligocene Formation in the Sera Plateau, Hiroshima, SW Japan

This study aimed to show the presence of an Oligocene formation in the Sera Plateau, located in the eastern part of Hiroshima Prefecture, SW Japan, using field surveys, a petrological study, and fission-track dating. According to field surveys conducted between 1996 and 2002, and supplementally in 2017, rhyolitic pyroclastic rocks and conglomerate beds unconformably covered by the Quaternary sediments were identified along the bank of Mihara-gawa River at Kurohada in Sera Town. The rhyolitic pyroclastic rocks, tentatively called Kurohada Ryolite, were composed of welded tuff, coarse tuff, and tuff breccia, and were intercalated with conglomerate beds lithologically similar to the mountain gravels. The Kurohada Rhyolite and the conglomerate beds were either horizontal or dipped gently to the northwest, with a total thickness of about 5 m. Based on whole-rock chemical composition analysis by X-ray fluorescence (SiO2: 72.39-75.82 wt % , K2O+Na2O: 5.78-7.80 wt % ) the welded tuff was classified into rhyolite of sub-alkalic series. Under the microscope, the pyroclastic rocks were composed of crystal fragments of plagioclase and quartz, and lithic fragments in glassy matrix, and signs of thermal alteration could not be confirmed. On the other hand, one of the lithic fragments of rhyolite contained biotite fine crystals as thermal metamorphic products. Thus, the Kurohada Rhyolite was distinguished from the Mesozoic Takada Rhyolites distributed widely in Hiroshima Prefecture depending on the presence of thermal metamorphism. Fission track ages of zircons from the welded tuff were 30.4 ± 1.6 Ma and 30.9 ± 1.5 Ma. This result shows that the geologic age of Kurohada Rhyolite and associated conglomerate beds in the study area is constrained to the early Oligocene and suggests the possibility that the mountain gravels distributed in the eastern part of Hiroshima Prefecture are Paleogenic.This study was partly supported by JSPS KAKENHI Grant Number JP16K00966

An improved and simple experimental technique for modeling thermal convection in science class using frozen starch syrup and localized heating

Plate tectonics is one of the most important and basic concepts required for understanding volcanic activity, seismicity, and various geological phenomena occurring within the framework of the rock cycle. Mantle convection, which refers to the thermal convection in the mantle, is the driving force for plate tectonics. Therefore, a heat convection modeling experiment was proposed for secondary school-level science students so that they can visualize and comprehend mantle convection. In this article, to improve operability and repeatability, we proposed a technique for conducting a simple experiment to model thermal convection using frozen starch syrup and localized heating; the use of starch syrup was suggested in a previous study.本研究の一部はJSPS科研費26350235，16K00966，17H00820の助成を受けて行われた