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.

Document clustering with cluster refinement and model selection capabilities

Abstract: In this paper, we propose a document clustering method that strives to achieve: (1) a high accuracy of document clustering, and (2) the capability of estimating the number of clusters in the document corpus (i.e. the model selection capability). To accurately cluster the given document corpus, we employ a richer feature set to represent each document, and use the Gaussian Mixture Model (GMM) together with the Expectation-Maximization (EM) algorithm to conduct an initial document clustering. From this initial result, we identify a set of discriminative featuresfor each cluster, and refine the initially obtained document clusters by voting on the cluster label of each document using this discriminative feature set. This self-refinement process of discriminative feature identification and cluster label voting is iteratively applied until the convergence of document clusters. On the other hand, the model selection capability is achieved by introducing randomness in the cluster initialization stage, and then discovering a value C for the number of clusters N by which running the document clustering process for a fixed number of times yields sufficiently similar results. Performance evaluations exhibit clear superiority of the proposed method with its improved document clustering and model selection accuracies. The evaluations also demonstrate how each feature as well as the cluster refinement process contribute to the document clustering accuracy.

Signaling network having common signaling node for protocol conversion

Abstract: A common channel signaling network comprises a first and a second subnetwork each being composed of interconnected signaling nodes having a service entity. The first and second subnetworks employ different versions of protocol for message transmission. A common signaling node is provided for protocol conversion. As the common signaling node receives a message from a service entity of each subnetwork, it converts the message format to the protocol of the other subnetwork, and transmits it to a service entity of the other subnetwork.

Channel engineering for the reduction of random-dopant-placement-induced threshold voltage fluctuation

Abstract: A simple model is proposed, which is able to calculate V/sub TH/ standard deviation due to random dopant placement in the channel, for arbitrary vertical impurity distributions. Substantial decrease in V/sub TH/ fluctuation, while keeping V/sub TH/ the same, is confirmed for low surface impurity channel MOSFETs, in agreement with the model prediction.

Adjacent cursor system with tactile feedback for the blind

Abstract: In a pointing system for use in notifying an operator of a cursor position on a display without relying on a sense of sight, information is derived in relation to an interactive item from a plurality of positions which are adjacent to the cursor position. A tactile sense or an inner force sense is determined by a relationship of the interactive items between the cursor position and the adjacent positions. The tactile sense may be displayed by a tactile display while the inner force sense, by a movable stage controllable by braking units. An absolute coordinate system may be used to indicate a position of the tactile display or the movable stage and is in one-to-one correspondence to a coordinate system of the display.

A framework for delivering multicast message in networks with mobile hosts

Abstract: To accommodate mobile hosts (MHs) within existing data networks, the static network is augmented with “mobile support stations” (MSSs) that communicate directly with MHs, usually via wireless links. Connectivity of the overall network changes dynamically as MHs connect to the static network fromdifferent “locations” (MSSs) at different times. Compared to their desktop counterparts, mobile hosts face a new set of constraints namely, low bandwidth of the wireless links, tight constraints on power consumption and a significantly lower computing capability. Thus, even without considering failures, integration of mobile computers within existing networks pose a new set of problems. In this paper, we look at the problems associated with delivering multicast messages to mobile hosts. First, we identify how a mobile host's ability to connect to different MSSs at different times, affects delivery of multicast messages and present schemes to deliver multicast messages to MHs from atleast-one location, from atmost-one location, and from exactly-one location. Next, we introduce ``multicast groups'' of mobile hosts wherein each multicast group is associated with a ``host view'', a set of MSSs representing the aggregate location information of the group. A host-view membership algorithmis then presented and combined with the multicast scheme for exactly-once delivery. As a result, to deliver a multicast message to a specified group, copies of the message need be propagated only to the MSSs in the group's host-view.