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Institution

NEC

CompanyTokyo, Japan
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.


Papers
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Patent
31 Aug 2000
TL;DR: In this paper, a content delivery services provider is disclosed for directing the at least one proxy server to pre-fetch content from the content provider original site using an optimum prefetch bandwidth allocation value.
Abstract: A content delivery services provider is disclosed for directing the at least one proxy server to pre-fetch content from the at least one content provider original site using an optimum pre-fetch bandwidth allocation value. The content delivery services provider is part of a system for storing and delivering content, which includes a plurality of end user browsers for requesting content, at least one content provider original site for delivering the content, and at least one proxy server for storing the content. These elements are coupled over a network for communicating with each other. The content delivery services provider programmed for: (1) modeling a retrieval time of content o of size size(o) using b units of bandwidth as ret(o)=congestion×size(o)×d(b), wherein d(b) is a unit delay observed when b units of bandwidth is used for pre-fetching the content, and congestion(Util) can be represented as congestion ( Util ) = β Util θ + α + φ or congestion(Util)=β×(1.0−Util) α +φ; (2) modeling an amount of delay observed by the at least one proxy server for the content fetched from the at least one content provider original site at time t 0 as ret  ( P ) = congestion ( P + r  ( t 0 ) B ) × r  ( t 0 ) × d , wherein P is a pre-fetch bandwidth size, B is a total bandwidth available to the system, r(t)=(1−σ(P))×u(t) is an amount of bandwidth the system uses for retrieving end user browser requests for content that is not stored in the at least one proxy server, σ(P) is a cache freshness and availability value given a bandwidth P, and u(t) is a user access rate; (3) calculating the optimum pre-fetch bandwidth allocation value P by solving δ   ret  ( P ) δ   P = 0 ; and (4) communicating the optimum pre-fetch bandwidth allocation value P to the at least one proxy server.

111 citations

Journal ArticleDOI
TL;DR: In this paper, the authors measured the electrical resistivities, Hall coefficients and thermoelectric powers of undoped, Si-doped and Mn-modified CrSi 2 crystals over the temperature range from 90°K to 1100°K.
Abstract: The electrical resistivities, Hall coefficients and thermoelectric powers of undoped, Si-doped and Mn-modified CrSi 2 crystals have been measured over the temperature range from 90°K to 1100°K. The undoped crystal is a p -type semiconductor with the hole concentration of about 4×10 20 /cm 3 . The hole concentration is decreased by doping silicon or manganese. Manganese atoms act as donors. Specimens heavily doped with manganese are n -type at low temperatures and change to p -type at high temperatures. Analysis of the experimental results leads to the following conclusions: (1) the forbidden energy gap=0.35 eV, (2) the ratio of the electron mobility to the hole mobility≃0.01 and (3) the density of state effective mass of electrons≃7 m 0 and that of holes≃5 m 0 . Assuming that the effective masses and the mobility ratio do not vary with temperature, the temperature dependence of the thermoelectric powers of the undoped and doped crystals can be explained satisfactorily.

111 citations

Journal ArticleDOI
18 Feb 1994-Science
TL;DR: The modified structure and intermolecular potential provide an additional dimension to the behavior of superconducting fullerides and should sensitively affect their electronic and conducting properties.
Abstract: The crystal structure of superconducting Na2CsC60 was studied by high-resolution powder neutron diffraction between 1.6 and 425 K. Contrary to the literature, the structure at low temperatures is primitive cubic [See equation in the PDF file], isostructural with pristine C60. Anticlockwise rotation of the C60 units by 98° about [111] allows simultaneous optimization of C60-C60 and alkali-fulleride interactions. Optimal Na+-C603- coordination is achieved with each sodium ion located above one hexagon face and three hexagon-hexagon fusions of neighboring fulleride ions (coordination number 12). Reduction of the C60 molecule lengthens the hexagon-hexagon fusions and shortens the pentagon-hexagon fusions (to ∼1.43 angstroms). On heating, Na2CsC60 undergoes a phase transition to a face-centered-cubic [See equation in the PDF file] phase, best modeled as containing quasi-spherical C603- ions. The modified structure and intermolecular potential provide an additional dimension to the behavior of superconducting fullerides and should sensitively affect their electronic and conducting properties.

111 citations

Journal ArticleDOI
TL;DR: The thermal conversion of one-dimensional (1D) fullerene (C60) single-crystal nanorods and nanotubes to nanoporous carbon materials with retention of the initial 1D morphology yields a new family of nanoporous carbons having π-electron conjugation within the sp(2)-carbon robust frameworks.
Abstract: Here we report the thermal conversion of one-dimensional (1D) fullerene (C-60) single-crystal nanorods and nanotubes to nanoporous carbon materials with retention of the initial 1D morphology The 1D C-60 crystals are heated directly at very high temperature (up to 2000 degrees C) in vacuum, yielding a new family of nanoporous carbons having pi-electron conjugation within the sp(2)-carbon robust frameworks These new nanoporous carbon materials show excellent electrochemical capacitance and superior sensing properties for aromatic compounds compared to commercial activated carbons

111 citations

Proceedings ArticleDOI
Kazutoshi Wakabayashi1, T. Yoshimura1
05 Nov 1989
TL;DR: A scheduling/allocation and control synthesis algorithm that can achieve good resource sharing and synthesize an efficient control sequence for nested conditional branches as well as for straight-line codes is presented.
Abstract: A scheduling/allocation and control synthesis algorithm is presented. The proposed algorithm can achieve good resource sharing and synthesize an efficient control sequence for nested conditional branches as well as for straight-line codes. The condition vector concept is introduced to allow mutual exclusion to be detected among operators, and is used to produce more efficient control sequences. The condition vector concept is concerned with the handling of nested condition branches and can be used for other scheduling methods. Results obtained from several experiments indicate that the proposed algorithms are efficient and effective. >

111 citations


Authors

Showing all 33297 results

NameH-indexPapersCitations
Pulickel M. Ajayan1761223136241
Xiaodong Wang1351573117552
S. Shankar Sastry12285886155
Sumio Iijima106633101834
Thomas W. Ebbesen9930570789
Kishor S. Trivedi9569836816
Sharad Malik9561537258
Shigeo Ohno9130328104
Adrian Perrig8937453367
Jan M. Rabaey8152536523
C. Lee Giles8053625636
Edward A. Lee7846234620
Otto Zhou7432218968
Katsumi Kaneko7458128619
Guido Groeseneken73107426977
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
20238
202220
2021234
2020518
2019952
20181,088