A hot clutter mitigation algorithm based on Subbanding and Space Fast-time Adaptive Processing (Fast-time STAP) for Multi-channel Synthetic Aperture Radar (MSAR) is analyzed, and is compared with the method based on just fast-time STAP. Simulation results demonstrate that the method based on subbanding and fast-time STAP performs better than the method based on just fast-time STAP in hot clutter mitigation for MSAR.

An alternative design for constructing multilevel space-time codes is proposed. For a given space-time block code, we combine several component codes in conjunction with set partitioning of the expanded signal constellation according to the coding gain distance criterion. The error performance of an example code is compared with a traditional multilevel space-time code in computer simulation.

This paper proposes a novel metamaterial structure, which equivalently indicates negative permittivity, for the purpose of applying it to a near-field imaging and/or diagnostics of electromagnetic properties by using a surface plasmon in microwave frequency range. The proposed structure consists of a conducting wire lattice with conducting spheres embedded at the mid-point of the wire. It is shown that a spatial dispersion of the wire lattice can be reduced significantly by the sphere. It is also shown that this structure can successfully be applied to an excitation of the surface plasmon in the microwave frequency range by adequately cutting into a thin slab.

The aim of this research is to study the power energy cost reduction of the mobile telecom industry through the supervisor control and data acquisition (SCADA) system application during globalization and liberalization competition. Yet this management system can be proposed functions: operating monitors, the analysis on load characteristics and dropping the cost of management.

This paper proposes multipoint-to-multipoint (MPtoMP) real-time broadcast transmission using network coding for ad-hoc networks like video game networks. We aim to achieve highly reliable MPtoMP broadcasting using IEEE 802.11 media access control (MAC) that does not include a retransmission mechanism. When each node detects packets from the other nodes in a sequence, the correctly detected packets are network-encoded, and the encoded packet is broadcasted in the next sequence as a piggy-back for its native packet. To prevent increase of overhead in each packet due to piggy-back packet transmission, network coding vector for each node is exchanged between all nodes in the negotiation phase. Each user keeps using the same coding vector generated in the negotiation phase, and only coding information that represents which user signal is included in the network coding process is transmitted along with the piggy-back packet. Our simulation results show that the proposed method can provide higher reliability than other schemes using multi point relay (MPR) or redundant transmissions such as forward error correction (FEC). We also implement the proposed method in a wireless testbed, and show that the proposed method achieves high reliability in a real-world environment with a practical degree of complexity when installed on current wireless devices.

Usually the contact voltage drop or contact resistance of electromagnetic relays is observed only to identify if the contacts are failure or not on the manufactures' life tests. However, it is difficult to reveal the contact performance degradation because the variation of contact resistance may not be obvious. In this paper, a new life test technology was investigated to analyze the contact failure mechanisms and degenerative processes of electromagnetic relays by measuring their time parameters including closing time, opening time, over-travel time, rebound duration and gap time during each operation. Moreover, for the purpose of verifying the time parameters, the contact motion and contact morphology during life test were record by using a high speed camera. Both the variations of time parameters and information obtained from photos taken by high speed camera show that it involves three different degenerative phases during the whole life of a relay. The results also indicate this method is an effective technology to discriminate and diagnose the failure mechanisms for electromagnetic relays.

Time synchronization is an essential service for wireless sensor networks (WSNs). However, fixed-period time synchronization can not serve multiple users efficiently in terms of energy consumption. This paper proposes a lightweight precision-adaptive protocol for cluster-based multi-user networks. It consists of a basic average time synchronization algorithm and an adaptive control loop. The basic average time synchronization algorithm achieves 1 µs instantaneous synchronization error performance. It also prolongs re-synchronization period by taking the average of two specified nodes' local time to be cluster global time. The adaptive control loop realizes diverse levels of synchronization precision based on the proportional relationship between sync error and re-synchronization period. Experimental results show that the proposed precision-adaptive protocol can respond to the sync error bound change within 2 steps. It is faster than the exponential convergence of the adaptive protocols based on multiplicative iterations.

The dynamic characteristics are the key issues in the optimum design of a permanent magnetic actuator (PMA). A new approach to forecast the dynamic characteristics of the multilink PMA is proposed. By carrying out further developments of ADAMS and ANSOFT, a mathematic calculation model describing the coupling of mechanical movement, electric circuit and magnetic field considering eddy current effect, is constructed. With this model, the dynamic characteristics of the multilink PMA are calculated and compared with the experimental results. Factors that affect the opening time of the multilink PMA are analyzed with the model as well. The method is capable of providing a reference for the design of the PMA.

This letter deals with mobile location estimation based on a minimax mean-squared error (MSE) algorithm using time-of-arrival (TOA) measurements for mitigating the nonline-of-sight (NLOS) effects in cellular systems. Simulation results are provided for illustrating the minimax MSE estimator yields good performance than the other least squares and weighted least squares estimators under relatively low signal-to-noise ratio and moderately NLOS conditions.

We theoretically study the performance limits of current-gain cutoff frequency, fT, for the HEMTs with InAs or In0.70Ga0.30As middle layers in the multi-quantum-well (MQW) channels by means of the quantum-corrected Monte Carlo (MC) method. We calculate the distribution of the delay time along the channel, τ(x), and define the effective gate length, Lg,eff, as the corresponding length to τ(x). By extrapolating Lg,eff to Lg = 0 nm, we estimate the lower limit of Lg,eff, Lg(0),eff. Then we estimate the performance limit of fT, fT(0), by extrapolating fT to Lg,eff(0). The estimated fT(0) are about 3.6 and 3.7 THz for the HEMTs with InAs middle layers of 5 and 8 nm in thickness, and about 3.0 THz for the HEMT with In0.70Ga0.30As middle layer of 8 nm in thickness, respectively. The higher fT(0) in the HEMTs with InAs middle layers are attributed to the increased average electron velocity, υd, in the channel. These results indicate the superior potential of the HEMTs using InAs in the channels. The HEMT with InAs middle layer of 8 nm in thickness shows the highest fT on condition of the same Lg because of its highest υd. However, the increased total channel thickness results in the longer Lg,eff(0), which leads to the restriction of fT(0). Therefore, in order to increase fT(0), it is essential to make Lg,eff short in addition to making υd high. Our results strongly encourage in making an effort to develop the HEMTs that operate in the terahertz region.

This paper presents an asynchronous FPGA that combines 4-phase dual-rail encoding and LEDR (Level-Encoded Dual-Rail) encoding. 4-phase dual-rail encoding is employed to achieve small area and low power for function units, while LEDR encoding is employed to achieve high throughput and low power for the data transfer using programmable interconnection resources. Area-efficient protocol converters and their control circuits are also proposed in transistor-level implementation. The proposed FPGA is designed using the e-Shuttle 65nm CMOS process. Compared to the 4-phase-dual-rail-based FPGA, the throughput is increased by 69% with almost the same transistor count. Compared to the LEDR-based FPGA, the transistor count is reduced by 47% with almost the same throughput. In terms of power consumption, the proposed FPGA achieves the lowest power compared to the 4-phase-dual-rail-based and the LEDR-based FPGAs. Compared to the synchronous FPGA, the proposed FPGA has lower power consumption when the workload is below 35%.

In this paper, we propose a novel filtering method for processing continuous skyline queries in wireless sensor network environments. The existing filtering methods on such environments use filters that are based on router paths. However, these methods do not have a major effect on reducing data for sensor nodes to transmit to the base station, because the filters are applied to not the whole area but a partial area. Therefore, we propose a novel and efficient method to dramatically reduce the data transmissions of sensors through applying an effective filter with low costs to all sensor nodes. The proposed effective filter is generated by using characteristics such as the data locality and the clustering of sensors. An extensive performance study verifies the merits of our new method.

The robust reduced order observer for a class of discrete-time Lipschitz nonlinear systems with external disturbance is proposed. It is shown that the proposed observer design can suppress the effect on the estimation error of external disturbance up to the prescribed level. Also, linear matrix inequalities are used to represent sufficient conditions on the existence of the proposed observer. Moreover, the maximum admissible Lipschitz constant of the proposed design is obtained for a given disturbance attenuation level. Finally, an illustrative example is given to verify the effectiveness of the proposed design.

A high-throughput on-chip monitoring circuit with a digital output is proposed for the variations of the NMOS and PMOS threshold voltages. A voltage-controlled delay line (VCDL) and a time-to-digital converter (TDC) are used to convert a small difference in analog voltage into a large difference in time delay. This circuit was applied to the transistors of W = 10 µm and L = 0.18 µm in a 1616 array matrix fabricated with a 0.18-µm process. The measurement of the threshold voltage shows that the maximum peak-to-peak intra-chip variation of NMOS and PMOS transistors are about 31.7 mV and 32.2 mV, respectively, for the temperature range from -25 to 75. The voltage resolutions of NMOS and PMOS transistors are measured to be 1.10 mV/bit and 3.53 mV/bit at 25, respectively. The 8-bit digital code is generated for the threshold voltage of a transistor in every 125 ns, which corresponds to the 8-MHz throughput.

Motivated by the needs of modern agriculture, in this paper we present CropNET, a wireless multimedia sensor network system for agriculture monitoring. Both hardware and software designs of CropNET are tailored for sensing in wide farmland without human supervision. We have carried out multiple rounds of deployments. The evaluation results show that CropNET performs well and facilitates modern agriculture.

User privacy preservation is critical to prevent many sophisticated attacks that are based on the user's server access patterns and ID-related information. We propose a password-based user authentication scheme that provides strong privacy protection using one-time credentials. It eliminates the possibility of tracing a user's authentication history and hides the user's ID and password even from servers. In addition, it is resistant against user impersonation even if both a server's verification database and a user's smart card storage are disclosed. We also provide a revocation scheme for a user to promptly invalidate the user's credentials on a server when the user's smart card is compromised. The schemes use lightweight operations only such as computing hashes and bitwise XORs.

The purpose of this study is to estimate the possible effect of cellular radio on implantable cardiac pacemakers in elevators. We previously investigated pacemaker EMI in elevator by examining the E-field distribution of horizontal plane at the height of expected for implanted pacemakers inside elevators. In this paper, we introduce our method for estimating EMI impact to implantable cardiac pacemakers using EMF distributions inside the region of the human body in which pacemakers are implanted. Simulations of a human phantom in an elevator are performed and histograms are derived from the resulting EMF distributions. The computed results of field strengths are compared with a certain reference level determined from experimentally obtained maximum interference distance of implantable cardiac pacemakers. This enables us to carry out a quantitative evaluation of the EMI impact to pacemakers by cellular radio transmission. This paper uses a numerical phantom model developed based on an European adult male. The simulations evaluate EMI on implantable cardiac pacemakers in three frequency bands. As a result, calculated E-field strengths are sufficiently low to cause the pacemaker to malfunction in the region examined.

In this letter, delay-dependent stability criterion for linear time-delay systems with multiple time varying delays is proposed by employing the Lyapunov-Krasovskii functional approach and integral inequality. By the N-segmentation of delay length, we obtain less conservative results on the delay bounds which guarantee the asymptotic stability of the linear time-delay systems with multiple time varying delays. Simulation results show that the proposed stability criteria are less conservative than several other existing criteria.

In this research, we focus on how to track a target region that lies next to similar regions (e.g. a forearm and an upper arm) in zoom-in images. Many previous tracking methods express the target region (i.e. a part in a human body) with a single model such as an ellipse, a rectangle, and a deformable closed region. With the single model, however, it is difficult to track the target region in zoom-in images without confusing it and its neighboring similar regions (e.g. "a forearm and an upper arm" and "a small region in a torso and its neighboring regions") because they might have the same texture patterns and do not have the detectable border between them. In our method, a group of feature points in a target region is extracted and tracked as the model of the target. Small differences between the neighboring regions can be verified by focusing only on the feature points. In addition, (1) the stability of tracking is improved using particle filtering and (2) tracking robust to occlusions is realized by removing unreliable points using random sampling. Experimental results demonstrate the effectiveness of our method even when occlusions occur.

In order to determine exposure compliance with the electromagnetic fields from a base station's antenna in the far-field region, we should calculate the spatially averaged field value in a defined space. This value is calculated based on the measured value obtained at several points within the restricted space. According to the ICNIRP guidelines, at each point in the space, the reference levels are averaged over any 6 min (from 100 kHz to 10 GHz) for the general public. Therefore, the more points we use, the longer the measurement time becomes. For practical application, it is very advantageous to spend less time for measurement. In this paper, we analyzed the difference of average values between 6 min and lesser periods and compared it with the standard uncertainty for measurement drift. Based on the standard deviation from the 6 min averaging value, the proposed minimum averaging time is 1 min.