NEC

About: NEC is a company organization based out in Tokyo, Japan. It is known for research contribution in the topics: Signal & Layer (electronics). The organization has 33269 authors who have published 57670 publications receiving 835952 citations. The organization is also known as: NEC Corporation & NEC Electronics Corporation.

Variable modulation communication method and system

Abstract: In a variable modulation communication method, the transmission quality of a transmission path is monitored. If the transmission quality is good, communication is performed while the transmission time is shortened by using a multilevel modulation scheme. If the transmission quality is bad, communication is performed while the transmission time is prolonged by using a modulation scheme having a smaller number of levels than the multilevel modulation scheme. A variable modulation communication apparatus is also disclosed.

SOI IGFETs having raised integration level

Abstract: A semiconductor integrated circuit device with the SOI structure is provided, which decreases the chip area of wiring lines interconnecting p- and n-channel IGFETs, raising their integration level. This device is comprised of a semiconductor layer formed on an insulating substrate. The semiconductor layer has a first area extending along a first direction and a second area extending along the first direction. The first and second areas are adjacent to one another. A first IGFET of a first conductivity type is formed in the first area of the semiconductor layer. A second IGFET of a second conductivity type opposite to the first conductivity type is formed in the first area of the semiconductor layer. One of a pair of source/drain regions of the second IGFET is electrically connected to one of a pair of source/drain regions of the first IGFET by a first interconnection diffusion region. A third IGFET of the first conductivity type is formed in the second area of the semiconductor layer. One of a pair of source/drain regions of the third IGFET is electrically connected to one of the pair of source/drain regions of the second IGFET by a second interconnection diffusion region.

Transport and magnetic properties of Tl 2 Ba 2 CuO 6+δ showing a δ-dependent gradual transition from an 85-K superconductor to a nonsuperconducting metal

Abstract: Transport and magnetic properties are investigated for ${\mathrm{Tl}}_{2}$${\mathrm{Ba}}_{2}$${\mathrm{CuO}}_{6+\mathrm{\ensuremath{\delta}}}$, which shows a gradual transition from an 85-K superconductor to a nonsuperconducting normal metal, as the excess oxygen content \ensuremath{\delta} is increased from \ensuremath{\sim}0 to \ensuremath{\sim}0.1. Hall measurements demonstrate that this transition arises from an overdoping of the hole carriers by excess oxygen. The temperature dependence of the resistivity is well fitted to a power-law dependence for all \ensuremath{\delta}'s, while the exponent shows a systematic change from linear (\ensuremath{\delta}\ensuremath{\sim}0) to quadratic (\ensuremath{\delta}\ensuremath{\sim}0.1) dependence. No significant changes of the Hall coefficient nor spin susceptibility are observed at the superconductor-metal phase boundary, suggesting a similarity and continuity between both the electronic structures. This is in sharp contrast to the previous observations for ${\mathrm{La}}_{2\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{CuO}}_{4}$.

Nonvolatile Magnetic Flip-Flop for Standby-Power-Free SoCs

Abstract: This paper presents a new nonvolatile magnetic flip-flop (MFF) for standby-power-critical applications. An MFF primitive cell for design libraries has been developed using 150 nm, 1.5 V CMOS and 240 nm MRAM processes. It has advantages over other nonvolatile flip-flops in high-speed store operations without endurance limitations. It also has high design compatibility with conventional CMOS LSI designs because it does not include any additional power lines and special transistors. A toggle frequency of 3.5 GHz was achieved by a SPICE simulation, which is comparable to that of a normal CMOS DFF in the same generation. The maximum frequency in a store operation was also estimated to be 500 MHz with 1-ns current width for the data backup. An MFF test chip, which includes 16-stage 8-bit shift register using MFFs, was fabricated with these processes. A 333 MHz store operation was measured without failed bits. The functional performance was sufficiently high to demonstrate the potential of MFFs, which helps to reduce the power dissipation of systems on chips (SoCs) dramatically.

Density-functional approach to electron dynamics: Stable simulation under a self-consistent field

Abstract: We propose efficient and stable numerical methods for simulating the electron dynamics within the time-dependent density-functional theory and the nonlocal pseudopotential. In this scheme, time evolution of the wave function is followed by self-consistently solving the time-dependent Kohn-Sham equation using the higher-order Suzuki-Trotter type split-operator method. To eliminate the numerical instability problem and increase the time step for the integration, we introduce the railway curve scheme to interpolate the self-consistent potential and the cutoff schemes to smooth the kinetic energy operator and the charge density. Applying these techniques to the electron dynamics of an Al cluster and the electron-ion dynamics of an excited K cluster, we found that they significantly improve the stability and efficiency. This opens the possibility of performing subpicosecond-long simulations of the transient dynamics of electrons and ions for a number of materials.