Effectiveness for Determination of Depositional Age by Detrital Zircon U–Pb Age in the Cretaceous Shimanto Accretionary Complex of Japan

Detrital zircon U–Pb ages indicate the crystallization age. Therefore, it is necessary to evaluate the effectiveness of determining the age of deposition using zircon age data. We carried out U–Pb dating of detrital zircons from sandstone at eight sites in the Cretaceous Shimanto accretionary complex on Kii Peninsula, Japan, with the aim of evaluating the accuracy of U–Pb zircon ages as indicators of the depositional age of sedimentary rocks by comparing zircon ages with radiolarian ages. Our results reveal zircons of late Cretaceous age, and the youngest peak ages are in good agreement with depositional ages inferred from radiolarian fossils. In addition, the youngest peak ages become younger as tectono-structurally downwards, and this tendency is clearer for the zircon ages than for the radiolarian ages. These results indicate that newly crystalized zircons were continuously supplied to the sediment by constant igneous activity during the late Cretaceous and that zircon ages provide remarkably useful information for determining the age of deposition in the Cretaceous Shimanto accretionary complex

Insight into enhanced field-effect mobility of 4H-SiC MOSFET with Ba incorporation studied by Hall effect measurements

Improved performance in 4H-SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) by incorporating Ba into insulator/SiC interfaces was investigated by using a combination of the Hall effect and split capacitance-voltage measurements. It was found that a moderate annealing temperature causes negligible metal-enhanced oxidation, which is rather beneficial for increments in field-effect mobility (μFE) of the FETs together with suppressed surface roughness of the gate oxides. The combined method revealed that, while severe μFE degradation in SiC-MOSFETs is caused by a reduction of effective mobile carriers due to carrier trapping at the SiO2/SiC interfaces, Ba incorporation into the interface significantly increases mobile carrier density with greater impact than the widely-used nitrided interfaces

At-sea experiment of adaptive time-reversal multiuser communication in the deep ocean

An at-sea experiment of multiuser communication in deep water using adaptive time reversal was carried out. In the experiment, two sources and a 20-channel receiver array were deployed at the range of 30 km in an area of 1500-2000 m water depth. One of the sources was moored and the other was suspended at various depths. For processing signals actually transmitted from two sources, it was demonstrated that adaptive time reversal could cancel multiuser interference independently of relative source positions. Additionally, for a more detailed investigation, the analysis of multiuser test signals by synthesizing signals from different depths was performed. As a result, especially in the case of adjacent sources, adaptive time reversal significantly suppressed crosstalk.http://www.godac.jamstec.go.jp/darwin/cruise/kaiyo/ky15-01/

Experimental study on multiple-input/multiple-output communication with time reversal in deep ocean

Multiple-input/multiple-output (MIMO) communication using adaptive time reversal is discussed comparing with orthogonal frequency division multiplexing (OFDM) with simulated MIMO test signals by synthesizing experimental data in deep ocean. The experiment was executed in 1,100-m-depth area at the range of 10 km with the bandwidth of 500 +/- 50 Hz. Although time variance is not included in analysis of OFDM, it is impossible to increase MIMO channels with OFDM. In the meantime, with adaptive time reversal, it is possible to achieve 8 x 20 and 6 x 20 MIMO communication with binary phase shift keying (BPSK) and quadrature phase shift keying (QPSK), respectively, in spite of time variance and input SNRs degradation due to synthesizing signals. Thus, it is demonstrated that adaptive time reversal has much better performance than OFDM in MIMO underwater acoustic communication.http://www.godac.jamstec.go.jp/darwin/cruise/kaiyo/ky15-15/