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.

A Short History of Computational Complexity

Abstract: It all started with a machine. In 1936, Turing developed his theoretical computational model. He based his model on how he perceived mathematicians think. As digital computers were developed in the 40’s and 50’s, the Turing machine proved itself as the right theoretical model for computation. Quickly though we discovered that the basic Turing machine model fails to account for the amount of time or memory needed by a computer, a critical issue today but even more so in those early days of computing. The key idea to measure time and space as a function of the length of the input came in the early 1960’s by Hartmanis and Stearns. And thus computational complexity was born. In the early days of complexity, researchers just tried understanding these new measures and how they related to each other. We saw the first notion of efficient computation by using time polynomial in the input size. This led to complexity’s most important concept, NP-completeness, and its most fundamental question, whether P = NP. The work of Cook and Karp in the early 70’s showed a large number of combinatorial and logical problems were NP-complete, i.e., as hard as any problem computable in nondeterministic polynomial time. The P = NP question is equivalent to an efficient solution of any of these problems. In the thirty years hence this problem has become one of the outstanding open questions in computer science and indeed all of mathematics. In the 70’s we saw the growth of complexity classes as researchers tried to encompass different models of computations. One of those models, probabilistic computation, started with a probabilistic test for primality, led to probabilistic complexity classes and a new kind of interactive proof system that itself led to hardness results for approximating certain NP-complete problems. We have also seen strong evidence that we can remove the randomness from computations and most recently a deterministic algorithm for the original primality problem. In the 80’s we saw the rise of finite models like circuits that capture computation in an inherently different way. A new approach to problems like P = NP arose from these circuits and though they have had limited success in separating complexity classes, this approach brought combinatorial techniques into the area and led to a much better understanding of the limits of these devices. ∗URL: http://www.neci.nj.nec.com/homepages/fortnow. Email: fortnow@research.nj.nec.com. †URL: http://www.cs.bu.edu/faculty/homer. Email: homer@cs.bu.edu. Supported in part by the NSF under grant NSF-CCR-998310 and by the ARO under grant DAAD19-02-1-0058.

Personalized navigation trees

Abstract: A method for constructing and maintaining a navigation tree based on external document classifiers is provided. In one embodiment, based on the returned category labels from the classifiers, a navigation tree is constructed by taking usability and user preferences into consideration. Control parameters and algorithms are provided for inserting into and deleting documents from the navigation tree, and for splitting and merging nodes of the navigation tree, are provided.

Room-Temperature Continuous-Wave Operation of InGaN Multi-Quantum-Well Laser Diodes Grown on an n-GaN Substrate with a Backside n-Contact

Abstract: Continuous-wave operation at room-temperature has been demonstrated for InGaN multi-quantum-well (MQW) laser diodes (LDs) grown on low-dislocation-density n-GaN substrates with a backside n-contact. The current, current density and voltage at the lasing threshold were 144 mA, 10.9 kA/cm2 and 10.5 V, respectively, for a 3 µm wide ridge-geometry diode with high-reflection dielectric coated mirrors. Single-transverse-mode emission was observed in the far-field pattern of the LDs and the beam full width at half power in the parallel and perpendicular directions was 6° and 25°, respectively.

Information processing device, display control method, and recording medium

Abstract: An information processing terminal (100) includes: a plurality of display parts (10, 20); a display control part (41) controlling the display operation of the display parts (10, 20); and an operation reception part (42) receiving an operation on display data displayed on the display parts (10, 20) The operation reception part (42) receives the entry of selection of a given area within the display data displayed on one (first) of the display parts The display control part (41) displays data associated in advance with the data within the selected area indicated by the entry of selection received by the operation reception part (42) on the other (second) display part that is different from the first display part

Packet size control technique

Abstract: A packet size control method allowing reduction in the period of time during which transmission is in a blocked state is disclosed. The size of a packet to be sent is determined depending on a measured round trip time (RTT), a current bandwidth of the data link layer, and a current congestion window size. First, a maximum segment size (MSS) is obtained based on the measured RTT and the current bandwidth of the data link layer using a table obtained by data transfer simulation. Thereafter, the obtained MSS is corrected using the current congestion window size. And the correct MSS is used to determine the final segment of data to be sent.