In this letter, a novel design of a switchable microstrip antenna is proposed for circular polarization diversity. The proposed antenna has a simple construction of inner and outer corner-truncated radiating circular patches for switchable circular polarization. By controlling the state of two PIN diodes, left- and right-hand circular polarizations are easily alternated. The results of experiments show excellent switching radiation performances at the resonant frequency and good agreements with the simulated ones.

In this paper, we propose an Estimation of Signal Parameter via Rotational Invariance Techniques (ESPRIT) based algorithm for estimating the two-dimensional-direction-of-arrivals (2D-DOA) of signals impinging on a uniform rectangular array (URA). The basic idea of the proposed algorithm is to successively apply two rounds of one-dimensional ESPRIT (1D-ESPRIT) algorithm for 2D-DOA estimation. The first round 1D-ESPRIT is applied on columns of the URA whereas the other round 1D-ESPRIT is on the rows of the URA. In between, a grouping technique is developed to produces signal groups each containing signals with distinguishable spatial signatures. The grouping technique is performed by using the subspace projection method where the needed spatial information is provided by the first round 1D-ESPRIT algorithm. Computer simulations show that, in addition to having significantly reduced computational complexity, the proposed algorithm possesses better estimation accuracy as compared to the conventional 2D-ESPRIT algorithm.

Silver electrical contacts are separated to generate break arcs in a DC48 V/6-24 A resistive circuit. The transverse magnetic field formed by a permanent magnet is applied to the break arcs. A series of experiments are carried out for two different experimental conditions. One condition is a constant contact separating speed while the magnetic flux density is changed to investigate the shortening effect of the arc duration. Another condition is a constant magnetic flux density while the contact separating speed is changed to investigate the changes in the arc duration and the contact gap when the break arc is extinguished. As a result, with constant separating speed, it is confirmed that the duration of break arcs is shortened by the transverse magnetic field and the break arcs are extinguished when the arc length reaches a certain value L. Under the condition of constant transverse magnetic field, (i) the arc duration is shortened by increasing the separation speed; (ii) the contact gap when the break arc is extinguished is almost constant when the separating speed v is sufficiently faster than 5 mm/s.

Many malicious programs we encounter these days are armed with their own custom encoding methods (i.e., they are packed) to deter static binary analysis. Thus, the initial step to deal with unknown (possibly malicious) binary samples obtained from malware collecting systems ordinarily involves the unpacking step. In this paper, we focus on empirical experimental evaluations on a generic unpacking method built on a dynamic binary instrumentation (DBI) framework to figure out the applicability of the DBI-based approach. First, we present yet another method of generic binary unpacking extending a conventional unpacking heuristic. Our architecture includes managing shadow states to measure code exposure according to a simple byte state model. Among available platforms, we built an unpacking implementation on PIN DBI framework. Second, we describe evaluation experiments, conducted on wild malware collections, to discuss workability as well as limitations of our tool. Without the prior knowledge of 6029 samples in the collections, we have identified at around 64% of those were analyzable with our DBI-based generic unpacking tool which is configured to operate in fully automatic batch processing. Purging corrupted and unworkable samples in native systems, it was 72%.

In this paper, a novel algorithm, Cross Low-dimension Pursuit, based on a new structured sparse matrix, Permuted Block Diagonal (PBD) matrix, is proposed in order to recover sparse signals from incomplete linear measurements. The main idea of the proposed method is using the PBD matrix to convert a high-dimension sparse recovery problem into two (or more) groups of highly low-dimension problems and crossly recover the entries of the original signal from them in an iterative way. By sampling a sufficiently sparse signal with a PBD matrix, the proposed algorithm can recover it efficiently. It has the following advantages over conventional algorithms: (1) low complexity, i.e., the algorithm has linear complexity, which is much lower than that of existing algorithms including greedy algorithms such as Orthogonal Matching Pursuit and (2) high recovery ability, i.e., the proposed algorithm can recover much less sparse signals than even 1-norm minimization algorithms. Moreover, we demonstrate both theoretically and empirically that the proposed algorithm can reliably recover a sparse signal from highly incomplete measurements.

In the received signal strength-based ranging algorithms, distance is estimated from a path loss model, in which the path loss exponent is considered a key parameter. The conventional RSS-based algorithms generally assume that the path loss exponent is known a priori. However, this assumption is not acceptable in the real world because the channel condition depends on the current wireless environment. In this paper, we propose an accurate estimation method of the path loss exponent that results in minimizing distance estimation errors in varying environments. Each anchor node estimates the path loss exponent for its transmission coverage by the sequential rearrangement of the received signal strengths of all sensor nodes within its coverage. Simulation results show that the proposed method can accurately estimate the actual path loss exponent without any prior knowledge and provides low distance estimation error.

Location of a source is of considerable interest in wireless sensor networks, and it can be estimated from passive measurements of the arrival times. A novel algorithm for source location by utilizing the time of arrival (TOA) measurements of a signal received at spatially separated sensors is proposed. The algorithm is based on total least-squares (TLS) method, which is a generalized least-squares method to solve an overdetermined set of equations whose coefficients are noisy, and gives an explicit solution. Comparisons of performance with standard least-squares method are made, and Monte Carlo simulations are performed. Simulation results indicate that the proposed TLS algorithm gives better results than LS algorithm.

As a global feature of fingerprint patterns, the Orientation Field (OF) plays an important role in fingerprint recognition systems. This paper proposes a fast binary pattern based orientation estimation with nearest-neighbor search, which can reduce the computational complexity greatly. We also propose a classified post processing with adaptive averaging strategy to increase the accuracy of the estimated OF. Experimental results confirm that the proposed method can satisfy the strict requirements of the embedded applications over the conventional approaches.

A hybrid overlay/underlay spectrum sharing method for cognitive radio networks based on user classification and convex optimization is proposed. Interference radii are configured for the primary receiver and each cognitive receiver. Cognitive users are divided into four groups and allocated different spectrum sharing patterns according to their distance from the primary transmitter and receiver. An optimal power allocation scheme that achieves the maximum sum rate of cognitive radio system on the premise of satisfying the interference constraint of primary receiver is acquired through the convex optimization method. Performance analysis and simulation results show that, compared with existing methods, our method leads to improved performance of achievable sum rate of cognitive users while guarantees the transmission of primary users.

In this brief paper, both static and dynamic behaviors of an electrostatic-actuated MEMS mirror are modeled and studied. To overcome the intrinsic pull-in problem and the dynamic disadvantages in the open-loop controlled actuation, a novel closed-loop feedback control method is proposed assuming the mirror tilt angle can be measured. First, a fixed voltage slightly higher than the pull-in voltage is applied when the mirror tilt angle is small. Then Proportional-Derivative (PD) control is used when the mirror is approaching the target position. Simulink simulation results show that this combined PD closed-loop control can overcome the pull-in problem and improve the dynamic behavior; furthermore, it can also enhance the robustness of the mirror actuation system to overcome environmental disturbances.

The dynamic encoding algorithm for searches (DEAS) is a recently developed algorithm that comprises a series of global optimization methods based on variable-length binary strings that represent real variables. It has been successfully applied to various optimization problems, exhibiting outstanding search efficiency and accuracy. Because DEAS manages binary strings or matrices, the decoding rules applied to the binary strings and the algorithm's structure determine the aspects of local search. The decoding rules used thus far in DEAS have some drawbacks in terms of efficiency and mathematical analysis. This paper proposes a new decoding rule and applies it to univariate DEAS (uDEAS), validating its performance against several benchmark functions. The overall optimization results of the modified uDEAS indicate that it outperforms other metaheuristic methods and obviously improves upon older versions of DEAS series.

To clarify how the occurrence of contact welding is related to the series of arc duration characteristics in consecutive make and break operations, electrical endurance tests were conducted on commercially available automotive relays, and the voltage waveforms of make and break arcs between the electrodes were recorded with LabVIEW. Experimental results indicate that welding may occur suddenly or randomly with increasing number of operations. A single arc or a group of make or break arcs with a long arc duration does not necessarily result in contact welding, but a group of longer make or break arcs within a narrow range of operation numbers can cause imminent contact welding (such an effect can be called the “group of longer arcing duration effect”). It is confirmed that contact welding may occur in both make and break operations, but the welding probability during make operations is much higher than that during break operations.

In this paper, the joint optimization issue of the cooperative precoder design is investigated for the transmission from the cooperative multi-point system to one mobile terminal. Based on the mean squared error minimization criterion, the problem is established for the cooperative precoder design. Unfortunately, this problem cannot be solved due to the block diagonal structure of the whole precoding matrix resulting from the fact that there is no data exchange among multiple base stations. In order to tackle this difficulty, the original problem is converted into an equivalent problem by stacking all of the nonzero entries in the block diagonal matrix into a long column vector. With the equivalent problem, the optimum solution is obtained in a closed-form expression by using the Lagrangian multiplier method. Numerical simulations illustrate the effectiveness of the proposed scheme in terms of bit error rate and spectral efficiency.

This paper presents pulse-coupled piecewise constant spiking oscillators (PWCSOs) consisting of two PWCSOs and a coupling method is master-slave coupling. The slave PWCSO exhibits chaos because of chaotic response of the master one. However, if the parameter varies, the slave PWCSO can exhibit the phenomena as a periodicity in the phase plane. We focus on such phenomena and corresponding bifurcation. Using the 2-D return map, we clarify its mechanism.

Temporal and spatial (geographical) fluctuations, which are present in the traffic of wireless sensor networks (WSNs), have a significant affect on the transmission performance and power consumption of WSNs. Several medium access control (MAC) mechanisms have been proposed for IEEE802.15.4 cluster-based WSNs to counter the temporal and spatial traffic fluctuations. However, these mechanisms cannot always achieve simultaneous improvement in both transmission performance and power consumption. In this paper, we propose two enhanced 2-level active period control mechanisms, BI&CAP control and BI&SD&CAP control, to achieve higher system performance than conventional control mechanisms. Various computer simulation results demonstrate the effectiveness of the proposed mechanisms for WSNs with various traffic fluctuations.

A spectrum sensing scheme for cognitive radio that includes coarse and fine sensing stages based on cyclostationarity is proposed in this paper. The cyclostationary feature detection (CFD) based on a single cyclic frequency (SCF) is used in the coarse sensing stage and that based on multiple cyclic frequencies (MCF) is employed in the fine sensing stage. Whether the fine sensing stage is performed or not is decided by comparing the statistic constructed in the coarse sensing stage with two thresholds. Theoretical analyses and simulation results show that the proposed sensing scheme has superior sensing performance and needs shorter sensing time.

In this paper, we present a sequentially rotated array antenna with a rectangular patch MSA fed by an L-probe. Since it's important to decrease couplings between patch elements in order to suppress the cross-polarization level, rectangular patches with aspect ratio of k are adopted. We investigate the cross-polarization level of the sequential array and discuss the relationship between the cross-polarization level and the mutual coupling. As a result, the bandwdith of the antenna element is obtained 14.6% when its VSWR is less than 1.5, and the directivity and cross-polarization level of a 4-patch sequential array are 10.8 dBic and 1.7 dBic, respectively, where k=0.6 and the patch spacing of d=0.5 wave length. These characteristics are 5.6 dB and 5.8 dB better than the corresponding values of a square patch sequential array antenna.

The induced voltage at the terminals of an implantable cardiac pacemaker of unipolar type was investigated by numerical calculations. Operating frequency was assumed 5 MHz according to a recent product. The dependencies of the induced voltage on various conditions were investigated including those on the locations of the transmitter and the pacemaker, and on the electric properties and the size of the phantom. The results showed that they were reasonably explained by considerations of quasi-static coupling of the electric field between the device and the pacemaker. Regarding the effect of electrical properties of the phantom a conservative result was obtained by using a phantom of homogeneous material with electric constants of fat. With regard to the phantom size the phantom used in previous studies provided more conservative results than that of larger size. The results suggested that the electric near-field intra-body communication devices are not likely to interfere with implantable cardiac pacemakers as far as the situation assumed in this study.

A novel algorithm is presented for near-field source localization with a symmetric uniform linear array (ULA) consisting of an even number of sensors. Based on element reordering of a symmetric ULA, the steering vector is factorised with respect to the range-independent bearing parameters and range-relevant 2-D location parameters, which allows the range-independent bearing estimation with rank-reduction idea. With the estimated bearing, the range estimation for each source is then obtained by defining the 1-D MUSIC spectrum. Simulation results are presented to validate the performance of the proposed algorithm.

Recently, Yu, Gong and Tang found new constructions of binary sequences of period 4N with optimal autocorrelation magnitude by different interleaved structure of sequences and sequences which had special correlation property, respectively. In this paper, we derive more results on binary sequences of period 4N which also have optimal autocorrelation.