Search

Considering that Von Neumann architecture has bottlenecks in both speed and power consumption, in-memory computation is a promising solution. The in-memory computation needs to be carried out in an array composed of storage units, which can be resistive random access memory (RRAM). When using RRAMs, the data storage density can be increased by taking advantage of their multiresistive state characteristics. However, the lack of reliability is a common problem of RRAM, and it is difficult to realize high long range cyclic characteristics purely from the principle. In this work, a new 3-D device based on RRAM is proposed, which is able to realize 2-bit vector multiplication and multibit storage. Analysis and SPICE simulation are conducted to validate the feasibility. The proposed device does not need to join the write-checking process and can greatly promote the improvement of area, storage density, and operation speed, providing a new route for the future in-memory computing. Compared to traditional CMOS circuits used for vector multiplication, our proposed device can achieve 93.75% reduction in terms of number of devices.

The unsustainable downscaling of Si transistor run counter to the rapid development of big data. Further geometric sizing needs industrial strategies and promotion. The two-dimensional materials emerge as excellent choice, allowing potential realization of area-efficient electronic circuit. Moreover, some novel architectures different from CMOS technology have also been reported. Based on that, we propose RRAM mirrored and RRAM-transistor hybrid single transistor logic gates that can realize non-volatile and switchable function. The internal equivalent circuits and corresponding operation scheme have been analyzed and illustrated. SPICE simulations have also been conducted to theoretically validate the feasibility of the devices. The benchmarked area reduction in standard cell can reach to 33% compared to conventional CMOS circuits, which show great protentional to enable next generation electronics. Moreover, the non-volatile devices proposed in this work can enable the logic-in-memory calculation for the next generation calculations.

When measuring the geomagnetic declination, the azimuth of the reference mark must be measured. This paper briefly describes the principle of measuring the azimuth by the differential GPS (Global Positioning System), several test observations of GPS and the results. In geomagnetic survey in China during 2002~2003, GPS was used in measuring the azimuth. Field observations by GPS were carried out during the period that satellite signals were better received. The statistical results of the GPS data at 135 stations in China show that the difference of the azimuths between 2 GPS measurements at various stations is 0.0″~5.9″ and the average is 1.6″. The azimuthal accuracy measured by GPS in this paper is 0.1′, and it is much better than the azimuthal accuracy 1.0′ given by Newitt et al.(1996). The observation results show that the azimuths measured by GPS are accurate and reliable; they are not related to the time-space changes. The geomagnetic declinations Dat various stations were obtained based on the azimuths measured by GPS, and the standard deviation of the reduced value of Dwas < 0.4′. Using the reduced values, the 8-order spherical cap harmonic model and the 5-order Taylor polynomial model in China for Dwere obtained. In geomagnetic survey, GPS is also used in measuring the longitude, the latitude and the elevation at various stations.

The geomagnetic survey at 135 stations in China were carried out in 2003. These stations are with better environmental condition and small magnetic field gradient (<5 nT/m). In the field survey, the geomagnetic declination D, the inclination Iand the total intensity Fwere measured. Ashtech ProMark2 differential GPS (Global Positioning System) was used in measuring the azimuth, the longitude, the latitude and the elevation at these stations. The accuracy of the azimuth is 0.1′. The geomagnetic survey data were reduced using the data at geomagnetic observatories in China. The mean standard deviations of the geomagnetic reduced values are: <1.5 nT for F, <0.5′ for Dand I. Using the geomagnetic data which include the data at 135 stations and 35 observatories in China, and the data at 38 IGRF (International Geomagnetic Reference Field) calculation points in China’s adjacent regions, the Taylor polynomial model and the spherical cap harmonic model were calculated for the geomagnetic field in China. The truncation order of the Taylor polynomial model is 5, and its original point is at 36.0°N and 104.5°E. Based on the geomagnetic anomalous values and using the method of spherical cap harmonic (SCH) analysis, the SCH model of the geomagnetic anomalous field was derived. In the SCH model, the pole of the spherical cap is at 36.0°N and 104.5°E, and the half-angle is 30°, the truncation order K=8 is determined according to the mean square deviation between the model calculation value and the observation value, the AIC (Akaike Information Criterion) and the distribution of geomagnetic field.

Abstract: Using observational data of geomagnetic total intensity from 13 stations in the Beijing-Tianjin region, 3 stations in the western Yunnan region of China, and 6 stations in California of U. S. A., the daily variations and their spectra of geomagnetic total intensity were analyzed and compared. The results show that the morphology, the range and spectrum of daily variations in geomagnetic total intensity are basically the same within the local extent of 100–200 km and are different in the large extent of 500 km. The latitude factor of the daily variation range of geomagnetic total intensity is about 1–2 nT/degree within the latitude extent of 25�–40�.