645 research outputs found
Defect imaging with guided waves propagating in a long range
No full textTakahiro HAYASHI, Masahiro NAGAO, Morimasa MURASE, Defect imaging with guided waves propagating in a long range, Journal of Solid Mechanics and Materials Engineering, 2008, 2(7), pp. 888-899, https://doi.org/10.1299/jmmp.2.888.Pipe inspection with guided waves is expected to provide an efficient screening technique that will enable the inspection of lengths of pipe of up to a few dozen meters. In contrast with conventional inspection equipment widely used in practical inspection that employ easy-to-use axisymmetric modes, the present authors have developed a defect imaging technique that uses non-axisymmetric modes. In a previous paper, defect images were only available over a short range of 1.2 meters from the transducers. Therefore, in the present study, the effects of long propagation on defect images are discussed. Long-range imaging was performed experimentally using source signals and their multiple reflections between both edges of a four-meter-long pipe, rather than the reflected waves from defects. In the experimental investigation, large degradation of images was found in the far field. A computer simulation of the guided wave propagation reveals that a major reason for the degradation is the difference between dispersion curves for an actual pipe and the theoretical dispersion curves. In order to reduce the degradation, images were obtained by neglecting higher modes with larger differences in phase velocity. As a result, images were obtained at correct locations at distances of up to approximately 20 meters from the transducers
THE METAMORPHOSIS OF THE ANTHOMEDUSA, POLYORCHIS KARAFUTOENSIS KISHINOUYE
No full textOne of the highest Anthomedusa, Polyorchis karafutoensis was first described by KISHINOUYE (1910) from Sakhalin. Since then the medusa was sometimes reported from the southern coast and the eastern lagoon of Sakhalin and the eastern part of Hokkaido, Japan by UCHIDA (1925, 1927, 1940). However, its life history remains mostly unknown, as also in other members of the genus Polyorchis except for the fragmental records of the medusan development in P. penicillatus by FEWKES ( 1889) and FOERSTER (1923), in P. karafutoensis by UCHIDA (1927) and in P. montereyensis by SKOGSBERG ( 948). In Akkeshi Bay Polyorchis karafutoensis is commonly found from middle April to late July. The early development of this species was previously reported by the author (NAGAO, 1963). In the present paper the metamorphosis and the growth in the medusan stage are dealt with. The medusae were collected in Akkeshi Bay and in Akkeshi Lake which is a lagoon and is directly connected with the bay ( cf. UCHIDA et al., 1963). The medusae were collected by surface tow every week on the average during April - July in 1963 and 1965. In the later season when the medusae grow larger they were scooped with a net. Umbrellar form, ocelli, size and other living characters of the medusae were recorded before preservation. Before proceeding further the author wishes to express his sincere thanks to Prof. Emer. Tohru UCHIDA and Prof. Mayumi YAMADA, Hokkaido University, for their kind guidance and encouragement
THE LIFE HISTORY OF EPERETMUS TYPUS BIGELOW AND THE SYSTEMATICS OF THE FAMILY OLINDIADIDAE (LIMNOMEDUSAE)
No full textThe olindiadiid medusa, Eperetmus typus was first described by BIGELOW (1915) as a new species of a new genus from Alaska based on a single medusa. Since then this species has sometimes been reported from the northern Pacific; two specimens from Alaska (BIGELOW, 1920), several specimens from Vancouver (FORSTER, 1923), three and many specimens from Hokkaido, northern Japan (UCHIDA, 1929, 1940), one specimen from Friday Harbor (MACKIE and MACKIE, 1963). All of them are the records of the medusan stage. Recently, the author found the hydroid colonies of this species from Akkeshi Bay, Hokkaido, and successfully reared the medusae liberated from these hydroids till matured (NAGAO, 1969a). On the one hand, from May to November in 1966 and 1967, many medusae of Eperetmus typus in various developmental stages were obtained by surface tows in the bay. The young medusae obtained by the surface tows coincided with the young medusae reared in the laboratory. The present paper deals mostly with the development of the medusan stage and the systematic considerations of the family Olindiadidae
Raw data for Pb2CoOsO6
No full textThe data are from an investigation carried out between 2013 and 2015 on a newly synthesized compound Pb2CoOsO6. The archive contains raw data from experimental measurements and electronic structure calculations. The data are provided in text files combined into a zip archive
Optical phase change in bismuth through structural distortions induced by laser irradiation
No full textSemimetal bismuth (Bi) is known to possess a wide range of peculiar properties, owing to its unique electronic band structure. Its electronic band can easily be distorted by structural changes, and thereby undergo transitions between semimetal to either semiconductor or metal states. Utilising a focused laser beam, one can easily introduce structural defects, along with phase changes, oxidation, and morphological modifications. Confocal Raman microscopy indicated that the as-fabricated Bi droplets inhibit the Raman signal from the underlying silicon (Si) substrate. After a laser flash heating step, the intensity of Si optical phonons was strongly enhanced at the positions of Bi droplets, and exceeding the intensity from the bare Si substrate. Thus, such laser irradiating step on the Bi droplets induces an optical phase change. The optical phase change was detected as going from inhibition to strong enhancement of the underlying Si substrate Raman signal. From the observed Bi optical phonon modes (E-g and A(1g)), alterations in the Raman peaks due to laser exposure indicated that the ordered crystallinity in pristine Bi droplets became deteriorated. The effects of atomic displacements and loss of structural order in Bi droplets impacts its dielectric response. The observed Si Raman signal enhancement is similar to the surface-enhanced Raman scattering effect typically known for noble metals
Laser-induced structural disordering and optical phase change in semimetal bismuth observed by Raman microscopy
No full textWe observed strong enhancement of the Raman signal from a silicon (Si) substrate hidden beneath nano/microdroplets of bismuth (Bi) after exposing them to a high-power laser beam (785 nm). Confocal Raman microscopy indicated that the as-fabricated Bi droplets inhibit the Raman signal from the underlying Si substrate. After the laser flash heating step, the intensity of Si optical phonons was strongly enhanced at the positions of Bi droplets, becoming even more intense than that of the bare Si substrate. Analyses of the Bi optical phonon modes, E-g and A(1g), confirmed a loss of long-range ordered crystallinity in the laser exposed droplets. Such lattice disordering can increase the available free carrier density in semimetal Bi, as occurs in the case of its amorphous and liquid states. And this can induce an optical phase change, which causes a marked enhancement of Si Raman signals through an effect similar to surface-enhanced Raman scattering (SERS)
Data-Driven Reservoir Modeling using Recurrent Neural Network and Physics-Based Network Model
No full textWe present efficient data-driven reservoir model workflows for a mature oil field involving large-scale CO2 Water Alternating Gas (WAG) injection. The CO2 WAG injection is conducted in more than two hundred wells in the entire field, and the operation area is spread throughout the field. Therefore, it is computationally prohibitive to implement history matching or optimization using full-field reservoir models. The objective of this study is to develop efficient data-driven approaches to optimize the CO2 WAG operation and maximize oil recovery from the reservoir. The proposed workflows are useful for predicting future production rates and understanding the reservoir connectivity between producers and injectors.
We propose two different types of approaches. First, deep learning algorithms are utilized to develop efficient data-driven reservoir models. Long Short-Term Memory (LSTM) is a special kind of neural network architecture and has been successfully applied to many sequential and time series problems. We formulate time series problems of the production and injection histories, and the LSTM algorithm is used to forecast the future production rate and to estimate the reservoir connectivity. Second, we utilize a physics-based data-driven reservoir model, the 1D network model. The 1D network model characterizes a reservoir by a network grid system, which connects each producer injector pair via a series of 1D grid cells. Numerical reservoir simulators compute the solution of the network grid system. History matching is implemented by Ensemble Smoother with Multiple Data Assimilation (ESMDA), and a streamline-based rate allocation optimization is implemented based on the calibrated network model.
The LSTM reservoir modeling workflow was validated using synthetic reservoir cases. It showed reasonable performance on production rates forecasting and reservoir connectivity estimation. Then, we successfully implemented this approach for a real field application. The 1D network model provided suitable history matching results for the entire field application of the mature oil reservoir. Moreover, a streamline-based rate allocation optimization was implemented, and it provided improved oil recovery from the reservoir
Studies on the Relation between Alkylating Agent‐Induced Chromosomal Aberrations and Embryotoxicity in Mice. II. The Potentiation of Teratogenicity and Clastogenicity of Isopropyl Methanesulfonate, N‐Methyl‐N‐Nitrosourea and Dimethyl Sulfate by Caffeine
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