This paper provides a novel signal processing for detecting defects based on the spatio-temporal gradient analysis over the Lamb-wave field. The proposed processing classifies the wave field through the rank of the covariance matrix which is defined by the four-dimensional vector with following components: a vertical displacement, its vertical velocity, and a pair of out-of-plane shearing strains. The covariance matrix provides the information about defects. Its determinant, therefore, is proposed as the inhomogeneity-index of the object surface. In this study, the physical meanings of the proposed index are shown, the computational process in the Lamb-wave field near the defects is discussed and their behaviors are investigated through FDTD-simulations and acoustic experiments.

For detecting the anomalous behavior of a user effectively, most researches have concentrated on statistical techniques. However, since statistical techniques mainly analyze the average behavior of a user's activities, some anomalies can be detected inaccurately. In addition, it is difficult to model intermittent activities performed periodically. In order to model the normal behavior of a user closely, a set of various features can be employed. Given an activity of a user, the values of those features that are related to the activity represent the behavior of the activity. Furthermore, activities performed in a session of a user can be regarded as a semantically atomic transaction. Although it is possible to apply clustering technique to these values to extract the normal behavior of a user, most of conventional clustering algorithms do not consider any transactional boundary in a data set. In this paper, a transaction-based clustering algorithm for modeling the normal behavior of a user is proposed. Based on the activities of the past transactions, a set of clusters for each feature can be found to represent the normal behavior of a user as a concise profile. As a result, any anomalous behavior in an online transaction of the user can be effectively detected based on the profile of the user.

This paper describes a real-time blind source separation (BSS) method for moving speech signals in a room. Our method employs frequency domain independent component analysis (ICA) using a blockwise batch algorithm in the first stage, and the separated signals are refined by postprocessing using crosstalk component estimation and non-stationary spectral subtraction in the second stage. The blockwise batch algorithm achieves better performance than an online algorithm when sources are fixed, and the postprocessing compensates for performance degradation caused by source movement. Experimental results using speech signals recorded in a real room show that the proposed method realizes robust real-time separation for moving sources. Our method is implemented on a standard PC and works in realtime.

In this letter, adaptive multi-stage parallel interference cancellation (PIC) receiver is considered for multi-rate DS-CDMA system. In each stage of the adaptive multi-stage PIC receiver, multiple access interference (MAI) estimates are obtained by the sub-bit estimates from the previous stage and the adaptive weights for the sub-bit estimates. The adaptive weights are obtained by minimizing the mean squared error between the received signal and its estimate through normalized least mean square (LMS) algorithm. It is shown that the adaptive multi-stage PIC receiver achieves smaller BER than the matched filter receiver, multi-stage PIC receiver, and multi-stage partial PIC receiver for the multi-rate DS-CDMA system in a Rayleigh fading channel.

At current interruption by electric contact, a repetition phenomenon of arc extinction and re-ignition is often observed before complete extinction of arc discharge, in some cases for a long time and in other cases for a short time. Occasionally, no re-ignition is observed. From a viewpoint of arc duration, the period of this repeating arc is also an important factor, if it is very long. However, the conventional explanation about the contact arc duration excludes this repeating arc phenomenon so that it fails to explain the reason and the duration of this phenomenon. For the purpose of investigating why this phenomenon occurs and how long it lasts, the arc extinction current and the arc re-ignition voltage have been measured for tungsten electrode, palladium electrode, copper electrode, and silver electrode. The circuit is, for simplicity, resistive with a capacitor source voltage and a fixed short arc gap of 0.5 mm. Taking newly into account the idea of unstable arc region by the measured results, the conventional explanation was improved. As a result, the reason and the duration of arc extinction and re-ignition phenomenon have become understandable. For simplification, the main description is based on the results by tungsten electrode. The results by other electrodes are summarized in appendix.

We report a flexible and lightweight wearable microstrip antenna that can be sewn into clothing and hats. This antenna is composed of felt and a conductive woven fabric. Experimental results clearly show that this antenna operates normally as a conventional microstrip antenna, and is practical and feasible for personal satellite communications.

In this proposed method, CRC coding is only applied to data unit, not to padded zeros that are to fill up the fixed length of data unit. So improved frame error rate and protocol efficiency are possible instead of increment of receiver complexity.

Recently, Yeh, Shen, and Hwang proposed a smartcard-based one-time password authentication scheme as an improved version of S/KEY, and claimed that their scheme is superior to other similar schemes in security and efficiency. In this letter, we show that Yeh-Shen-Hwang's scheme is still vulnerable to a stolen-verifier attack that may cause serious security problems.

This paper presents a novel blind multiple access interference (MAI) suppression filter in DS/CDMA systems. The filter is adaptively updated by parallel projections onto a series of convex sets. These sets are defined based on the received signal as well as a priori knowledge about the desired user's signature. In order to achieve fast convergence and good performance at steady state, the adaptive projected subgradient method (Yamada et al., 2003) is applied. The proposed scheme also jointly estimates the desired signal amplitude and the filter coefficients based on an approximation of an EM type algorithm, following the original idea proposed by Park and Doherty, 1997. Simulation results highlight the fast convergence behavior and good performance at steady state of the proposed scheme.

In this paper, we propose a design method of filters by successive projection (SP) method using multiple extreme frequency points based on Fritz John's theorem. In conventional SP method, only one extreme frequency point at which the deviation from the given specification is maximized is used in the update of the filter coefficients. Therefore, enormous amount of iteration numbers are necessary for research the solution which satisfies the given specification. In the proposed method, the updating coefficient using multiple extreme frequency points is possible by Fritz John's theorem. As a result, the solution converges less iteration number than the conventional SP method.

Low Earth Orbit (LEO) satellite constellations have been proposed in recent years to provide broadband network access. This research focuses on Walker Delta type constellation. Walker Delta has overlapping ascending and descending orbits. Although Inter Satellite Links (ISLs) can be utilized between satellites orbiting in the same direction, ISLs cannot be utilized between satellites orbiting in opposite directions. As a result, a Walker Delta Constellation with ISLs has two locally separate overlapping meshes, an ascending and a descending mesh. To reach from one local mesh to the other, the traffic has to pass through the highest latitude intra-plane ISLs. Therefore the propagation delay between terminals connected to different meshes is greater than between terminals connected to the same mesh. Due to characteristic handover of LEO satellites, terminals can connect to a satellite in the other mesh during communication, causing drastic variation of propagation delay which results in degradation of communication quality. These issues can be solved by continuously connecting the communication terminals to the same mesh. In this paper, a satellite selection method for Walker Delta Constellations with double mesh coverage is proposed. It employs geographical location information of the communicating terminals, to connect them to the same mesh. In addition, the proposed method selects the mesh that minimize propagation delay for that communication session. It is shown through simulation that the proposed method is effective in reducing delay and jitter for a connection while improving overall communication quality of the network.

The conventional algorithms in the echo canceling system have drawback when they are faced with double-talk condition in noisy environment. Since the double-talk and noise signal are exist, then the error signal is contaminated to estimate the gradient correctly. In this paper, we define a new class of adaptive algorithm for tap adaptations, based on the correlation function processing. The computer simulation results show that the Correlation LMS (CLMS) and the Extended CLMS (ECLMS) algorithms have better performance than conventional LMS algorithm. In order to implement the ECLMS algorithm, the Frequency domain Extended CLMS (FECLMS) algorithm is proposed to reduce the computational complexity. However the convergence speed is not sufficient. In order to improve the convergence speed, the Wavelet domain Extended CLMS (WECLMS) algorithm is proposed. The computer simulation results support the theoretical findings and verify the robustness of the proposed WECLMS algorithm in the double-talk situation.

Novel contact materials such as extrinsic conducting polymers can improve contact performance and enable device miniaturisation. This paper presents an investigation of conducting polymer materials used to minimise the effect of fretting slip at the contact interface of connector terminals. Initial experimental studies are presented and a mechanical model is used to describe the polymer interface slip and stick characteristics. For fretting to be minimised the polymer must be sufficiently elastic, with a high coefficient of friction with the contacting terminal, and a sufficient normal force to ensure no slip. Experimental studies of a polymer-tin interface are conducted to characterise contact resistance performance under fretting conditions. A resistance model of the polymer interface is developed.

In this letter, Multicarrier Code Division Multiple Access (MC-CDMA) technique combined with Space Time Block Code (STBC) is analyzed in the case of two transmit antennas. A multicarrier transmit diversity scheme with antenna selection is proposed. The transmission power is allocated onto the antenna which has larger channel gain instead of the two antennas uniformly. Simulation results show that the new scheme has considerable performance gain compared to the Alamouti's scheme.

The enlargement of the left lobe of the liver and the shrinkage of the right lobe are helpful signs at MR imaging in diagnosis of cirrhosis of the liver. To investigate whether the volume ratio of left-to-whole (LTW) is effective to differentiate cirrhosis from a normal liver, we developed an automatic algorithm for three-dimensional (3D) segmentation and volume calculation of the liver region in multi-detector row CT scans and MR imaging. From one manually selected slice that contains a large liver area, two edge operators are applied to obtain the initial liver area, from which the mean gray value is calculated as threshold value in order to eliminate the connected organs or tissues. The final contour is re-confirmed by using thresholding technique. The liver region in the next slice is generated by referring to the result from the last slice. After continuous procedure of this segmentation on each slice, the 3D liver is reconstructed from all the extracted slices and the surface image can be displayed from different view points by using the volume rendering technique. The liver is then separated into the left and the right lobe by drawing an inter-segmental plane manually, and the volume in each part is calculated slice by slice. The degree of cirrhosis can be defined as the ratio of volume in these two lobes. Four cases including normal and cirrhotic liver with MR and CT slices are used for 3D segmentation and visualization. The volume ratio of LTW was relatively higher in cirrhosis than in the normal cases in both MR and CT cases. The average error rate on liver segmentation was within 5.6% after employing in 30 MR cases. These results demonstrate that the performance in our 3D segmentation was satisfied and the LTW ratio may be effective to differentiate cirrhosis.

A new algorithm, termed reduced-order Root-MUSIC, for high resolution direction finding is proposed. It requires finding all the roots of a polynomial with an order equaling twice the number of propagating signals. Some Monte Carlo simulations are used to test the effectiveness of the proposed algorithm.

Plastic ferrules for single-mode (SM) MU-type simplified receptacles are fabricated with a precise injection-molding technique using a liquid crystalline polymer (LCP). The fabricated plastic ferrules exhibit an eccentricity of < 0.6 µm and outer diameter variation of 1 µm. MU-type simplified plugs incorporating the plastic ferrules have an average insertion loss of 0.13 dB and a return loss of > 46 dB. The plastic ferrules exhibit good resistance in 500-cycle mating tests, and in vibration and impact tests as well. The initial optical characteristics are maintained during a temperature and humidity cycling test and a heat-cycling test.

In this presentation the authors consider in detail the problems relating to parameters like contact normal force, the effective contact areas and the surface plating, which have significant influence onto the surge current strength of electrical power contacts. Obtaining the behaviour of machine turned pin and socket contacts with different pin diameters the parameters of the active contact area radius, the constriction resistance and the constriction temperature are calculated by using FEM for elastic/plastic surface deformation. With the knowledge of the constriction radius the temperature curve of the contact area was determined by coupled electrical/thermal FE calculation. Laboratory tests were carried out in order to verify the FE-calculation.

Inside a connector an interface with low insertion force and contact resistance is required, utilizing low cost materials such as copper alloys surrounded by tin coating. Relating to the application, the operating parameters have a wide range of values of currents, forces and materials. In this paper, we present a new experimental method based on non-intrusive probing of the deflection of the spring terminal with a laser technique. The main feature is that the reflection of the Laser beam onto the spring allows the determination of the contact force of the lamella-spring inside the female part. The technique requires the following insertion parameters during the insertion stroke: contact deflection δ, which allows contact force Fc, insertion force Fi and contact resistance Rc. It was found that the insertion force has a maximum value which decreases to the stable value, and depends on the size and the material of the pin. However contact resistance decreases sharply when first inserting, and tends to stable values on completing the insertion process, which is less sensitive to the pin diameter. Furthermore the final value which is important for the connector characterization is related and discussed. Finally, discrepancies were observed between the experimental and calculated data with simple numerical models. More complex models are in progress, which should improve the convergence of the theoretical approach to experimental results and proceed to the optimization of the connector parameters.

This paper proposes a new on-chip linearizer self-adapting to the input power and its implementation to high linear monolithic microwave integrated circuit (MMIC) power amplifier for 1.95 GHz wide-band code division multiple-access (W-CDMA) system. The linearizer consists of InGaP/GaAs heterojunction bipolar transistor (HBT) active bias circuit and reverse biased junction diode of which dynamic admittance to input power level functions adaptively to control the bias to the amplifier. The proposed linearizer has little insertion power loss, and more importantly, it consumes no additional die area and DC power. The HBT MMIC power amplifier with the integrated linearizer exhibits a maximum output power of 30.3 dBm, a power gain of 27.5 dB, a power added efficiency of 42% at the maximum output power under an operation voltage of 3.4 V, and adjacent channel leakage power ratio of -38 dBc at 27 dBm of output power.