We extend the framework of cost-sensitive classification to mitigate risks of huge costs occurring with low probabilities, and propose an algorithm that achieves this goal. Instead of minimizing the expected cost commonly used in cost-sensitive learning, our algorithm minimizes conditional value-at-risk, also known as expected shortfall, which is considered a good risk metric in the area of financial engineering. The proposed algorithm is a general meta-learning algorithm that can exploit existing example-dependent cost-sensitive learning algorithms, and is capable of dealing with not only alternative actions in ordinary classification tasks, but also allocative actions in resource-allocation type tasks. Experiments on tasks with example-dependent costs show promising results.

Comb capacitors suitable for use in advanced complementary metal-oxide semiconductor (CMOS) technology nodes are frequently constructed from low metal layers located closely above the conductive silicon substrate. This results in high parasitic capacitances across the thin dielectric between the two layers. Therefore, a shield for reducing this parasitic capacitance is proposed in order to use the comb capacitor at high frequency. From electromagnetic (EM) simulation results using a 3D EM simulator, the quality factor (Q-factor) of the proposed shielded comb capacitor for the differential signal improved by 20% at 30-110 GHz compared to the unshielded capacitor. Consequently, a scalable model is proposed, which operates up to millimeter-wave frequencies. The results are verified by experimental data using fabricated comb capacitors from a 90 nm 1P9M CMOS process. Compared with the experimental results, the simulated common-mode and differential-mode S parameters of the model has a root-mean-square (r.m.s.) error of under 2.1%.

This paper addresses the ambiguity of radar altimetry related to the statistical nature of the Earth's surface roughness. A hypothetic altimetry method, which provides a simple way to quantify the measures of ambiguity, is proposed. Cramer-Rao lower bounds on the variances of estimates for the mean altitude and root-mean-square height of the sea surface are suggested as such quantitative measures. The accuracy of some types of air- and spaceborne radar altimeters is numerically analyzed against the derived lower bounds.

In a frequency-selective multiple-input multiple-output (MIMO) channel, the optimum transmission is achieved by beamforming with eigenvectors obtained at each discrete frequency point, i.e., an extension of eigenbeam-space division multiplexing (E-SDM). However, the calculation load of eigenvalue decomposition at the transmitter increases in proportion to the number of frequency points. In addition, frequency-independent eigenvectors increase the delay spread of the effective channel observed at the receiver. In this paper, we propose a pseudo eigenvector scheme for the purpose of mitigating the calculation load and maintaining frequency continuity (or decreasing the delay spread). First, we demonstrate that pseudo eigenvectors reduce the delay spread of the effective channels with low computational complexity. Next, the practical performance of the pseudo E-SDM (PE-SDM) transmission is evaluated. The simulation results show that PE-SDM provides almost the same or better performance compared with E-SDM when the receiver employs a time-windowing-based channel estimation available in the low delay spread cases.

This paper presents a new strategy to detect and diagnose fault of a manipulator based on the expression with a Probabilistic Production Rule (PPR). Production Rule (PR) is widely used in the field of computer science as a tool of formal verification. In this work, first of all, PR is used to represent the mapping between highly quantized input and output signals of the dynamical system. By using PR expression, the fault detection and diagnosis algorithm can be implemented with less computational effort. In addition, we introduce a new system description with Probabilistic PR (PPR) wherein the occurrence probability of PRs is assigned to them to improve the robustness with small computational burden. The probability is derived from the statistic characteristics of the observed input and output signals. Then, the fault detection and diagnosis algorithm is developed based on calculating the log-likelihood of the measured data for the designed PPR. Finally, some experiments on a controlled manipulator are demonstrated to confirm the usefulness of the proposed method.

In this letter, we propose a new approach to incremental coding of the subfield codes for plasma display panels (PDPs). The proposed approach suppresses the halftone noise of the PDPs, while completely eliminating false contour noise, as do existing incremental subfield codes, by selecting an optimal incremental subfield code adaptively for a given input image. The proposed method maps the problem of selecting the optimal incremental subfield code onto a special-case shortest path problem. Results of experiment using 109 sample images illustrated that the proposed method improved the average peak signal-to-noise ratio by 4.4-6.2 dB in halftone noise compared with existing incremental subfield coding methods.

We explain how network failures were caused by a natural disaster, describe the restoration steps that were taken, and present lessons learned from the recovery. At 21:26 on December 26th (UTC+9), 2006, there was a serious undersea earthquake off the coast of Taiwan, which measured 7.1 on the Richter scale. This earthquake caused significant damage to submarine cable systems. The resulting fiber cable failures shut down communications in several countries in the Asia Pacific networks. In the first post-earthquake recovery step, BGP routers detoured traffic along redundant backup paths, which provided poor quality connection. Subsequently, operators engineered traffic to improve the quality of recovered communication. To avoid filling narrow-bandwidth links with detoured traffic, the operators had to change the BGP routing policy. Despite the routing-level first aid, a few institutions could not be directly connected to the R&E network community because they had only a single link to the network. For these single-link networks, the commodity link was temporarily used for connectivity. Then, cable connection configurations at the switches were changed to provide high bandwidth and next-generation Internet service. From the whole restoration procedure, we learned that redundant BGP routing information is useful for recovering connectivity but not for providing available bandwidth for the re-routed traffic load and that collaboration between operators is valuable in solving traffic engineering issues such as poor-quality re-routing and lost connections of single-link networks.

This letter proposes a new weighted fair queueing algorithm, which adjusts dynamically each flow's service probability according to its weight and average packet length and then uses the service probability parameters to implement fair queueing. This solves the main drawback of traditional weighted fair queueing algorithms--the packet-based tracing of weight parameters. In addition, this letter proposes a novel service probability calculation method which solves the unfairness problem induced by the variable packet length.

In this paper, we present a new fast Fourier transform (FFT) algorithm to reduce the table size of twiddle factors required in pipelined FFT processing. The table size is large enough to occupy significant area and power consumption in long-point FFT processing. The proposed algorithm can reduce the table size to half, compared to the radix-22 algorithm, while retaining the simple structure. To verify the proposed algorithm, a 2048-point pipelined FFT processor is designed using a 0.18 µm CMOS process. By combining the proposed algorithm and the radix-22 algorithm, the table size is reduced to 34% and 51% compared to the radix-2 and radix-22 algorithms, respectively. The FFT processor occupies 1.28 mm2 and achieves a signal-to-quantization-noise ratio (SQNR) of more than 50 dB.

The objective of this paper is to analyze a pull type multi-product, multi-line and multi-stage flexible manufacturing system whose resources are subject to planned and unplanned breakdown conditions. To ensure a continual supply of the finished products, under breakdown conditions, parts/materials flow through alternate routes exhibiting routing flexibility. The machine resources are flexible in this study and are capable of producing more than one item. Every machining and assembly station has been equipped with automated inspection units to ensure the quality of the products. The system is modelled through coloured Petri net methodology and the impact of input factors have been shown on the performance of the system. The study has been extended to explore near-optimal conditions of the system using design of experiment and response surface methods.

It is well known that Pisarenko's frequency estimate for a single real tone can be computed easily using the sample covariance with lags 1 and 2. In this Letter, we propose to use alternative covariance expressions, which are inspired from the modified covariance (MC) frequency estimator, in Pisarenko's algorithm. Computer simulations are included to corroborate the theoretical development of the variant and to demonstrate its superiority over the MC and Pisarenko's methods.

For simulating i.i.d. time-varying MIMO channels using multiple Jakes' rings, it is desirable to generate channels having stable statistics with fewer scatterers. The statistical property of the conventional Jakes' model may depend on the initial phase set assigned to scattering points. In this letter, we present simple and effective conditions on arrangement of scattering points to achieve stable fading properties. The results show that the proposed arrangement provides higher statistical stability in generating time-varying channels.

This paper presents a mathematically simple method of maximum SINR (Signal to Interference plus Noise Ratio) design of broadband MIMO (Multiple Input Multiple Output) communication systems adopting TDL (Tapped Delay Line) structure for spatio-temporal processing in both transmitter and receiver sides. The weight vectors in both ends are determined alternately, optimizing one side by fixing the other, and this operation is repeated until the SINR converges. The performance of MIMO systems using the proposed approach is investigated through computer simulations, and it is demonstrated that, though it requires high computational cost, the TDL structure brings high ability to mitigate the influence of frequency selective fading, particularly when the duration of the delay profile is long. Moreover, experimental results show that the equable distribution of the resources (weights and delay units) to both arrays is better choice than the concentration of them to one side of the transmitter or receiver.

This paper discusses an on-line Tasks Assignment and Routing Problem (TARP) for Autonomous Transportation Systems (ATSs) in manufacturing systems. The TARP results in a constrained version of the Pickup and Delivery Problem with Time Windows (PDPTW). As an approach to this problem, a cooperative algorithm with autonomous distributed agents has been proposed. The algorithm is able to plan deadlock-free routes even though the buffer capacity is less, but includes reformability at the point that computation time of that case increases drastically. This paper proposes an initial task assignment method to reduce computation time on planning routes. Results of computational experiments show effectiveness of the proposed method.

In this letter, we propose a novel signal detection method that matches maximum likelihood (ML) performance but requires much less computational complexity than ML detection. When the well-known linear decoding method is used for space-time block coded (STBC) OFDM systems in fast-fading channels, co-channel interference (CCI) as well as inter-carrier interference (ICI) occurs. A maximum likelihood (ML) method can be employed to deal with the CCI; however, its computational complexity is very high. In this letter, we propose a signal detection method for orthogonal space-time coded OFDM systems that achieves the identical error performance as the ML method, but requires much less computational complexity.

In the acquisition of projection data of X-ray CT, logarithm operation is indispensable. But noise distribution is nonlinearly projected by the logarithm operation, and this deteriorates the precision of CT number. This influence becomes particularly remarkable when only a few photons are caught with a detector. It generates a strong streak artifact (SA) in a reconstructed image. Previously we have clarified the influence of the nonlinearity by statistical analysis and proposed a correction method for such nonlinearity. However, there is a problem that the compensation for clamp processing cannot be performed and that the suppression of SA is not enough in photon shortage state. In this paper, we propose a new technique for correcting the nonlinearity due to logarithm operation for noisy data by combining the previously presented method and an adaptive filtering method. The technique performs an adaptive filtering only when the number of captured photons is very few. Moreover we quantitatively evaluate the influence of noise on the reconstructed image in the proposed method by the experiment using numerical phantoms. The experimental results show that there is less influence on spatial resolution despite suppressing SA effectively and that CT number are hardly dependent on the number of the incident photons.

This paper proposes to use eye movements to characterize the performance of individuals in reviewing software documents. We design and implement a system called DRESREM, which measures and records eye movements of document reviewers. Based on the eye movements captured by eye tracking device, the system computes the line number of the document that the reviewer is currently looking at. The system can also record and play back how the eyes moved during the review process. To evaluate the effectiveness of the system we conducted an experiment to analyze 30 processes of source code review (6 programs, 5 subjects) using the system. As a result, we have identified a particular pattern, called scan, in the subject's eye movements. Quantitative analysis showed that reviewers who did not spend enough time on the scan took more time to find defects on average.

This paper presents interference suppression using a subband adaptive array (SBAA) for uplink space-time block coding (STBC) code division multiple access (CDMA) under a frequency selective fading (FSF) channel. The proposed scheme utilizes CDMA with STBC and a receive array antenna with SBAA processing at the receiver. The received signal is converted into the frequency domain before despreading and adaptive processing is performed for each subband. A novel SBAA construction is introduced to process CDMA signals based on STBC. To improve the performance of the proposed scheme, we evaluate STBC-SBAA using spreading codes cyclic prefix (CP). Simulation results demonstrate an improved performance of the proposed system for single and multiuser environments compared to competing related techniques.

A passive optical network (PON) that provides fiber to the home (FTTH) services is a fundamental access network topology in Japan. An optical fiber line monitoring and testing system is essential if we are to improve service reliability and reduce the maintenance costs of optical access networks. PONs have optical splitters in their optical fiber lines. It is difficult to find a fault in an optical fiber line equipped with an optical splitter by using a conventional optical fiber line testing system, which uses optical time-domain reflectometer (OTDR) in a central office (CO), because Rayleigh backscattering from the branched fibers accumulates in the OTDR trace. This paper describes a newly developed optical fiber line testing method that employs bi-directional OTDRs with two wavelengths at branched fiber regions in a PON to locate a fault precisely. Optical fiber line testing is conducted by two OTDRs that are installed in a CO and on a customer's premises, respectively. The OTDR in the CO has a U-band maintenance wavelength. We present two kinds of maintenance wavelength allocation for OTDRs on a customer's premises, which are in the U-band and C-band respectively. An OTDR whose maintenance wavelength is in the U-band enables us to test in-service PON lines simply by filtering the U-band wavelength. For the maintenance wavelengths in the C-band, we can use a cost-effective conventional OTDR to test the PON from the customer's premises on condition that we clarify the peak pulse power limit and dynamic range. We describe the test procedures for both cases. We also clarify the insertion loss design for an optical filter in the CO when using the U-band to provide the maintenance wavelength and the criteria for in-service line testing when the using C-band to provide the maintenance wavelength. To confirm the feasibility of our approach, we demonstrate a bi-directional OTDR method using the U-band and the C-band, and the test procedure, which successfully detected fault locations in branched fiber regions. We also describe the use of packet loss measurements to investigate the effect of in-service line testing with an OTDR in the C-band on data communication quality.

A new scheme for reducing optical beat interference noise in a reflective semiconductor optical amplifier based wavelength division multiplexed/subcarrier multiplexing -- passive optical network is proposed. This method uses an Fabry Perot laser locked by modulated lights from optical network units in a central office. As an experimental verification, it is reported that carrier to noise ratio is enhanced by 10 dB and power penalty is improved by 16 dB.