In this letter, we consider a class of approximately feedback linearized systems that contain both triangular and feedforward forms. With a utilization of the transformation scaling factor, we analytically show that the considered system can be globally exponentially stabilized, globally bounded, or locally stabilized depending on the shapes of triangular and feedforward forms. Our new method broadens a class of nonlinear systems under consideration over the existing results.

This paper deals with stability analysis of hybrid systems. Such systems are characterized by a combination of continuous dynamics and logic based switching between discrete modes. Lyapunov theory is a well known methodology for the stability analysis of linear and nonlinear systems in control system literature. Construction of Lyapunov functions for hybrid systems is generally a difficult task, but once these functions are defined, stabilization of the system is straight-forward. The sum of squares (SOS) decomposition and semidefinite programming has also provided an efficient methodology for analysis of nonlinear systems. The computational method used in this paper relies on the SOS decomposition of multivariate polynomials. By using SOS, we construct a (some) Lyapunov function(s) for the hybrid system. The reduction techniques provide numerical solution of large-scale instances; otherwise they will be practically unsolvable. The introduced method can be used for hybrid systems with linear or nonlinear vector fields. Some examples are given to demonstrate the capabilities of the proposed approach.

In mobile ad hoc networks, as the communications have to be achieved autonomously and via third parties, a variety of risks against stable communication and session completion can be predicted. Many researchers have been studying these issues, i.e., mobility, broadcast storm, selfish behavior on data forwarding, security, and so forth. However, availability of routes against selfish power off is still to be addressed. This paper defines a new, realistic and practical problem beyond the scope of malicious program modification, called selfish power off, and evaluates the influence of it. Here, a selfish user turns his terminal on only when it has some data to send or receive and decline to work as an intermediate user by turning its terminal power off. In addition, this paper proposes a solution, called Proactive COoperation Mechanism (PCOM) against selfish power off in order to eliminate the influence of selfish power off. In PCOM, each user holds the cooperation records of its adjacent users, and forwards only those packets that are generated by users with good cooperation records. PCOM thus prevents SUs from joining the network. Extensive simulation shows the efficiency of our proposal in maintaining network connectivity and fairness in resource consumption.

For the closed loop multiple-input-multiple-output (MIMO) systems, Fisher's adaptive bit loading algorithm gives the best error performance by jointly optimizing the transmit powers, rates, and number of streams. However, its good performance comes at the cost of high and variable computational complexity for the joint optimization. In this letter, we propose an efficient multi-mode precoding algorithm using a simplified mode table. Numerical results show that the proposed algorithm provides almost the same performance as Fischer's with much less computational complexity.

Monotonic condition, a well-known sufficient condition for Schur stability of real polynomials, is relaxed. The condition reads that a series of strictly and monotonically decreasing positive coefficients of the polynomials yields Schur stability. It is shown by inspecting the original proof that equalities are allowed in all the inequalities but two which are located at appropriate positions.

Note taking is a fundamental activity for learning, and many software tools which enable students to take digitized notes have been proposed. Digitized notes are advantageous because they can be easily edited, rearranged, and shared. Although many note-taking tools have been proposed, there has been little research to examine the effect of note annotation and rearrangement with a digitized tool in terms of knowledge acquisition. Therefore, we have investigated the effect of note annotation and rearrangement on how well lecture content is remembered by learners. By annotation, we mean adding both handwritten and typed text, and rearrangement includes moving and deleting handwritten notes. We developed a simple note-taking application specialized for explanation, and evaluated it through a laboratory experiment with eight participants. The results show that note annotation and rearrangement significantly improved how well the participants remembered lecture content. Thus, the effect of annotation and rearrangement on remembrance was confirmed with respect to digitized notes.

In this paper, we consider a simple nonlinear system which consists of a chaotic system and multirate sample-hold controllers. The proposed system exhibits some stabilized Unstable Periodic Orbits which are embedded on the chaos attractor of the original chaotic system. We provide a condition to stabilize Unstable Periodic Orbits and its domain of attraction. Some theoretical results are verified in the experimental circuit.

In this paper, a simple piezoelectric floating mass transducer (PFMT) for implantable middle ear hearing devices (IMEHDs) is proposed and its modeling and designing are studied. The transducer which can be implanted in the meddle ear consists of a PMN-PT multi-layered piezoelectric actuator, an elastic material, and a metal case. The proposed transducer has a simple structure and the force generated from the piezoelectric actuator is efficiently transferred to the ossicles of the middle ear. For the analysis of the vibration characteristics, the transducer attached on the ossicle is simplified into a simple mechanical model considering the mass of an incus. And the vibration displacement of the model is calculated using computer simulation and verified by the experimental results. It is shown that the designed PFMT can allow implantation in the middle ear cavity and provide a sufficiently high output of more than 100 nm of vibration displacement. Plus, it is verified that the vibration characteristics of PFMT can be controlled through adjustment of the metal case size and the elastic material of the transducer.

In this paper, we discuss the relationship between the test generation complexity for path delay faults (PDFs) and that for stuck-at faults (SAFs) in combinational and sequential circuits using the recently introduced τk-notation. On the other hand, we also introduce a class of cyclic sequential circuits that are easily testable, namely two-column distributive state-shiftable finite state machine realizations (2CD-SSFSM). Then, we discuss the relevant conjectures and unsolved problems related to the test generation for sequential circuits with PDFs under different clock schemes and test generation models.

Non-malleability is an important security property of commitment schemes. The property means security against the man-in-the-middle attack, and it is defined and proved in the simulation paradigm using the corresponding simulator. Many known non-malleable commitment schemes have the common drawback that their corresponding simulators do not work in a straight-line manner, requires rewinding of the adversary. Due to this fact, such schemes are proved non-malleable only in the stand-alone cases. In the multiple-instances setting, i.e., when the scheme is performed concurrently with many instances of itself, such schemes cannot be proved non-malleable. The paper shows an efficient commitment scheme proven to be non-malleable even in the multiple-instances setting, based on the KEA1 and DDH assumptions. Our scheme has a simulator that works in a straight-line manner by using the KEA1-extractor instead of the rewinding strategy.

The traditional feedback linearization method often requires the full system parameter and state information. In this paper, we consider an asymptotic stabilization problem of a class of feedback linearizable nonlinear systems by using less than the full parameter/state information. First, our approach is to classify system parameters into two categories--'directly used parameters' and 'indirectly used parameters.' Then, a feedback linearizing controller is designed by using only the 'directly used parameters' and the observer is utilized to estimate the transformed states (diffeomorphism) which includes 'indirectly used parameters.' Thus, in our control approach, we use only a partial set of system parameters and partial state information for asymptotic stability. The useful aspects of the proposed scheme are illustrated through an example.

In this paper, we present a novel method to incorporate metadata into data mining. The method has many advantages. It can be completed automatically and is independent of a specific database. Firstly, we convert metadata into ontology. Then input a rule set to a reasoner, which supports rule-based inference over the ontology model. The outputs of the reasoner describe the prior knowledge in metadata. Finally, incorporate the prior knowledge into data mining.

Recently low-voltage and low-noise analog circuits with sub 100-nm CMOS devices are strongly demanded for implementing mobile digital multimedia and wireless systems. Reduction of supply voltage makes it difficult to attain a signal voltage swing, and device deviation causes large DC offset voltage and 1/f noise. This paper describes noise reduction technique for CMOS analog and RF circuits operated at a low supply voltage below 1 V. First, autozeroing and chopper stabilization techniques without floating analog switches are introduced. The amplifier test chip with a 0.18-µm CMOS was measured at a 0.6-V supply, and achieved 89-nV/ input referred noise (at 100 Hz). Secondly, in RF frequency range, to improve a phase noise of voltage controlled oscillator (VCO), two 1/f-noise reduction techniques are described. The ring VCO test chip achieves 1-GHz oscillation, -68 dBc/Hz at 100-kHz offset, 710-µW power dissipation at 1-V power supply.

This paper proposes a Mel-Wiener filter to enhance Mel-LPC spectra in the presence of additive noise. The transfer function of the proposed filter is defined by using a first-order all-pass filter instead of unit delay. The filter coefficients are estimated based on minimization of the sum of the square error on the linear frequency scale without applying the bilinear transformation and efficiently implemented in the autocorrelation domain. The proposed filter does not require any time-frequency conversion, which saves a large amount of computational load. The performance of the proposed system is comparable to that of ETSI AFE. The optimum filter order is found to be 3, and thus filtering is computationally inexpensive. The computational cost of the proposed system except VAD is 53% of ETSI AFE.

We experimentally investigated terahertz photomixing operation at room temperature in an InGaP/InGaAs/ GaAs two-dimensional plasmon-resonant photomixer incorporating grating-bicoupled dual-gate structure. Photoelectrons drifting into a high-density plasmon cavity grating from an adjacent low-density one extensively excite the plasmon resonance, resulting in emission of terahertz radiation. A vertical cavity formed between the two-dimensional plasmon grating plane and an indium-tin-oxide mirror at the back surface gains the radiation. Self-oscillation initially at around 4.5 THz excited by a dc-photo carrier component was reinforced by the photomixed differential-frequency excitation at 4.0 and 5.0 THz. This indicates a possibility of injection-locked oscillation of the photomixer in the terahertz frequency band.

We propose a new tableau construction which builds an FSM, instead of a Kripke structure, from a formula in a class of temporal logic named ASTL. This FSM is a maximal model of the formula under the preorder derived from simulation relations. Additionally, we propose a method using the tableaus to build controllers in a certain topology of interconnected FSMs. We can use ASTL to describe the desired behaviors of the control system. This method is applicable to generating digital circuits. Moreover, this method accepts a wider range of specifications than conventional methods.

In this paper, we show that speed and yield of reconfigurable devices can be enhanced by utilizing within-die (WID) delay variations. An LUT Array LSI is fabricated to confirm whether FPGAs have clear WID variations to be utilized. We can measure delay variations by counting the number of LUTs a signal propagates within a certain time. Clear die-to-die (D2D) and WID variations are observed. We propose a variation model from the measurement results. Adequacy of the model is discussed from randomness of the random component. Effect of the speed and yield enhancement is confirmed using the proposed model. Yield increases from 80.0% to 100.0% by optimizing configurations.

In this paper, we derive state equations for linearized discrete-time models of forth-order charge-pump phase-locked loops. We solve the differential equations of the loop filter by using the initial conditions and the boundary conditions in a period. The solved equations are linearized and rearranged as discrete-time state equations for checking stability conditions. Some behavioral simulations are performed to verify the proposed method. By examining the stability of loops with different conditions, we also propose an expression between the lower bound of the reference frequency, the open loop unit gain bandwidth, and the phase margin.

The 2-dimensional (2-D) Hilbert curve is a one-to-one mapping between 2-D space and one-dimensional (1-D) space. It is studied actively in the area of digital image processing as a scan technique (Hilbert scan) because of its property of preserving the spacial relationship of the 2-D patterns. Currently there exist several Hilbert scan algorithms. However, these algorithms have two strict restrictions in implementation. First, recursive functions are used to generate a Hilbert curve, which makes the algorithms complex and computationally expensive. Second, both sides of the scanned rectangle must have same size and each size must be a power of two, which limits the application of the Hilbert scan greatly. In this paper, a Pseudo-Hilbert scan algorithm based on two look-up tables is proposed. The proposed method improves the Hilbert scan to be suitable for real-time processing and general application. The simulation indicates that the Pseudo-Hilbert scan can preserve point neighborhoods as much as possible and take advantage of the high correlation between neighboring lattice points. It also shows competitive performance of the Pseudo-Hilbert scan in comparison with other scan techniques.

Iterative receivers, which perform MMSE detection and decoding iteratively, can provide significant performance improvement compared with noniterative method. However, due to the high computational cost and numerical instability, conventional MMSE detection using a priori information can not be implemented in hardware. In this letter, we propose a newly-built iterative receiver which is division-free and numerically stable, and then we analyze the results of a fixed-point simulation and present the hardware implementation architecture.