This letter investigates the peak-to-average power ratio (PAR) reduction scheme employing a simple symbol transform in OFDM-CDMA systems. This approach is very simple because of no additional complexity and works with arbitrary numbers of subcarriers and without restriction on the allocation of spreading code, maintaining an original transmission efficiency. Simulation results show that the investigated scheme gives the PAR reduction gain of 2-3 dB compared to the original OFDM and OFDM-CDMA signals, and can provide the further PAR reduction by combing the partial transmit sequence (PTS) scheme, which is less complex compared to the ordinary PTS approach.

A nonlinear circuit described by the forced Duffing's equation is known to display a rich variety of dynamical behavior. Coupling two Duffing's circuits by a linear resistor, we conclude that combinatorial resonances occur on weak coupling condition. In a coupled system, although symmetrical properties are usually observed, breaking of symmetry can lead to much more complex nonlinear resonant phenomena. In this paper, we discuss asymmetry in four cases of perturbation on parameters. Many bifurcation diagrams are presented. Comparing with symmetrical cases, we analyze the combinatorial resonances in coupled Duffing's circuit completely.

In this paper our recently introduced method called output distributional influence function (ODIF) is used for the evaluation of the robustness properties of the nonlinear filter class of morphological filters. Several examples of the ODIFs for the dilation, closing and clos-opening are given and explained carefully. For each of these morphological filters the effect of filter length is examined by using the ODIFs for the expectation and variance. The robustness properties of the filters are also compared to each other and the effect of the distribution of the contamination is investigated for the closing as an example of realistic filtering conditions.

We consider the problem of constructing nonlinear dynamical systems that realize an arbitrary prescribed tree sources. We give a construction of dynamical systems by using piecewise-linear maps. Furthermore, we examine the obtained dynamical system to show that the structure of the memory of tree sources is characterized with some geometrical property of the constructed dynamical systems. Using a similar method, we also construct a dynamical system generating an arbitrary prescribed reverse tree source and show that the obtained dynamical system has some interesting geometrical property explicitly reflecting the tree structure of the memory of the reverse tree source.

A brain-computer interface using an electroencephalogram as input into an artificial neural network is investigated as a potentially general control system applicable to all subjects and time frames. Using the intent and imagination of bending the left or right elbow, the left and right desired movements are successfully distinguished using event-related desynchronization resolved by fast Fourier transformation of the electroencephalogram and analysis of the power spectrum using the artificial neural network. The influence of age was identified and eliminated through the use of a frequency distribution in the α band, and the recognition rate was further improved by confirmation based on forced excitement of the β band in the case of an error. The proposed system was effectively trained for general use by using the combined data of a cross-section of subjects.

Multicasting is an efficient communication tool for use in multi-point applications such as conferencing and information distribution. In ad hoc networks, node mobility causes frequent changes of network topology, and re-construction of the multicast tree in an efficient and effective manner becomes a critical issues. In case of link breakage, most of the multicast tree construction protocols available presently require either a total re-build of the tree or to reconnect a disjoined node back to the multicast tree via the shortest path which may disrupt the optimising factors, such as energy consumption, delay or cost, used in the building of the original tree. In this paper, we introduce a computationally efficient recovery algorithm which will also minimise the power consumption on the tree.

This very useful optical sampling system uses a passively mode-locked fiber laser as an optical sampling pulse source and is based on sum-frequency generation. The optical pulse had a sufficiently short pulse width, and its peak power was very high. In addition, it had a very low timing jitter. We could observe optical signals that were jitter-free in terms of single scanning. The sum-frequency generation conversion efficiency was 1.0 10-4 W-1, and the temporal resolution was 700 fs, when we used a 5-mm-thick KTP crystal. A 320-Gbit/s optical signal could be clearly observed. We have also developed a polarization-insensitive optical sampling system with a two-path configuration based on sum-frequency generation using the type-II phase matching condition in a KTP crystal. The polarization dependency was less than 3.5% (0.15 dB) in the wavelength range from 1520 to 1620 nm.

We investigate the statistical features of both random- and chaos-based FM timing signals to ascertain their applicability to digital circuits and systems. To achieve such a goal, we consider both the case of single- and two-phase logic and characterize the random variable representing, respectively, the time lag between two subsequent rising edges or between two consecutive zero-crossing points of the modulated timing signal. In particular, we determine its probability density and compute its mean value and variance for cases which are relevant for reducing Electromagnetic emissions. Finally, we address the possible problems of performance degradation in a digital system driven by a modulated timing signal and to cope with this we give some guidelines for the proper choice of the statistical properties of the modulating signals.

Analog Hopfield neural networks (HNNs) have so far been used to solve many kinds of optimization problems, in particular, combinatorial problems such as the TSP, which can be described by an objective function and some equality constraints. When we solve a minimization problem with equality constraints by using HNNs, however, the constraints are satisfied only approximately. In this paper we propose a circuit which rigorously realizes the equality constraints and whose energy function corresponds to the prescribed objective function. We use the SPICE program to solve circuit equations corresponding to the above circuits. The proposed method is applied to several kinds of optimization problems and the results are very satisfactory.

This paper proposes an analytical expression for the maximum operating frequency of an emitter-coupled-logic master-slave toggle flip-flop (ECL MS TFF) based on an impulse response method. The analytical expression was in good agreement with not only SPICE simulations, but also experimental values. The analytical expression also indicated that state-of-the-art InP-based heterojunction bipolar transistors have potential to achieve over 100-GHz operation in ECL MS TFFs. Also, the proposed method was applied to the maximum operating frequency of a source-coupled FET logic (SCFL) MS TFF.

In this paper, we consider the all-to-all broadcast problem in optical broadcast star networks using Wavelength Division Multiplexing. Our network model assumes that receivers are fixed-tuned and transmitters are tunable such that optical lasers assigned to transmitters have limited access to the network bandwidth; hence, each node must be equipped with multiple optical lasers and/or multiple optical filters in order to maintain a single-hop network. This paper is primarily concerned with single-hop networks, in which each node is assigned a single optical filter. Lower bounds are first established on the number of lasers per each node and the minimum schedule length, and a schedule achieving the minimum schedule length is presented. The results are applicable to arbitrary tuning delays, arbitrary numbers of wavelength channels, and optical lasers' arbitrary tuning ranges. Network models with optical devices having limited tuning ranges have not yet been considered in connection with transmission schedules, and this is the first work in this new direction.

With the aim of applying a MISS tunnel-diode cell to a high-density RAM, we studied its problems and developed three circuit technologies to solve them. The first, a standby-voltage control scheme, reduces standby currents and increases the signal current by 3.4 times compared to the conventional one. The second, a hierarchical bit-line structure, reduces the number of memory cells in a bit-line without increasing the number of sense amplifiers. The third, a twin-dummy-cell technique, generates a proper reference signal to discriminate read currents. These technologies enable a capacitorless MISS diode cell with an effective cell area of 6F 2 (F: minimum feature size) to be applied to a high-density RAM.

The segregation of non-magnetic phases such as borosilicate and Cr was investigated by crystallization behavior during the surface and bulk crystallization of Co-based amorphous alloys. The concentration of metalloids (B and Si) determined the extent of grain boundary segregation of borosilicate glass during surface crystallization. During the bulk crystallization of (Co75Cr25)0.8Si5B15 amorphous alloy, solute rejection of Cr resulted in the nucleation of Cr-deficient ferromagnetic crystals and non-magnetic σ-phase was subsequently precipitated along the grain boundary. These results show that crystallization process, i.e. nucleation and growth can be controlled to optimize the microstructure to reduce media noises in Co-based recording media.

The efficient distribution of stored information has become a major concern in the Internet. Since the web workload characteristics show that more than 60% of network traffic is caused by image documents, how to efficiently distribute image documents from servers to end clients is an important issue. Proxy cache is an efficient solution to reduce network traffic. And it has been shown that an image caching method (Graceful Caching) based on hierarchical coding format performs better than conventional caching schemes in recent years. However, as the capacity of the cache is limited, how to efficiently allocate the cache memory to achieve a minimum expected delay time is still a problem to be resolved. This paper presents an integrated caching algorithm to deal with the above problem for image databases, web browsers, proxies and other similar applications in the Internet. By analyzing the web request distribution of the Graceful Caching, both replacing and pre-fetching algorithms are proposed. We also show that our proposal can be carried out based on information readily available in the proxy server; it flexibly adapts its parameters to the hit rates and access pattern of users' requesting documents in the Graceful Caching. Finally we verify the performance of this algorithm by simulations.

Competition of two-photon and one-photon absorption in Si-APD was studied. Device should be cooled down in order to clearly observe two-photon absorption at low illumination intensity. Passive Geiger mode operation was studied to sensitively detect small number of carriers generated by two-photon absorption. The illumination intensity dependence of the photocurrent pulse count number is well explained by taking into account the two absorption mechanisms and a dead time period that depends on bias voltage.

We show that the necessary and sufficient condition for the existence of a balanced bowtie decomposition of the complete multigraph λKn is n 5 and λ(n-1) 0 (mod 12). Decomposition algorithms are also given.

Nominalization is a linguistic phenomenon in which events usually described in terms of clauses are expressed in the form of noun phrases. Extracting event structures is an important task in text mining applications. To achieve this goal, clauses are parsed and the argument structure of main verbs are extracted from the parsed results. This kind of preprocessing has been commonly done in the past research. In order to extract event structure from nominalized phrases as well, we need to establish a technique to transform nominalized phrases into clauses. In this paper, we propose a method to transform nominalized phrases into clauses by using corpus-based approach. The proposed method first enumerates possible predicate/argument structures by referring to a nominalized phrase (noun phrase) and makes their ranking based on the frequency of each argument in the corpus. The algorithm based on this method was evaluated using a corpus consisting of 24,626 aviation safety reports in English and it achieved a 78% accuracy in transformation. The algorithm was also evaluated by applying a text mining application to extract events and their cause-effect relations from the texts. This application produced an improvement in the text mining application's performance.

Self-organizing map is a widely used tool in high-dimensional data visualization. However, despite its benefits of plotting very high-dimensional data on a low-dimensional grid, browsing and understanding the meaning of a trained map turn to be a difficult task -- specially when number of nodes or the size of data increases. Though there are some well-known techniques to visualize SOMs, they mainly deals with cluster boundaries and they fail to consider raw information available in original data in browsing SOMs. In this paper, we propose our Factor controlled Hierarchical SOM that enables us select number of data to train and label a particular map based on a pre-defined factor and provides consistent hierarchical SOM browsing.

Due to the explosive growth of the network technologies, 3D models and animations have led to a great interest in various media. Especially 3D mesh models (3D meshes), which approximate surfaces by polygonal meshes are widely used to model 3D objects. In 1D and 2D signals such as speech, audio, images, video, etc., the signal values are located on "grids", for example the signals of images are defined on pixels. Thus, the errors of such signals can be explicitly defined by differences of the values on the "grids". However since in the 3D meshes, vertices are located on arbitrary positions in a 3D space and are triangulated in arbitrary ways, the grids cannot be defined. This makes it difficult to measure error on the 3D meshes. In this paper, we propose a new numerical method to measure the errors between two different 3D meshes.

This paper describes how four-wave mixing (FWM) noise within multifiber linear-lightwave WDM ring networks is reduced due to their thin wavelength density. Preliminary numerical analysis for a full-mesh connection pattern shows that a simple wavelength insertion technique can improve FWM noise performance as high as about 10 dB.