Organic light emitting diodes (OLEDs) containing nanostructured cathode buffer layers were fabricated, and their electrical and emitting properties were investigated. The OLEDs have an ITO anode/CuPc/TPD/Alq3/buffer layer/Al cathode structure with the buffer layers made from nanostructured alternating layers Alq3 and Al. The driving voltage and the efficiency of the devices were improved by insertion of the buffer layer. It was estimated that some modulations of the Schottky barrier at the Alq3 and the Al cathode interface were induced due to the insertion of the buffer layer and it caused an enhancement of electron injection from the Al cathode.

An LMS adaptive digital filter using distributed arithmetic (DA-ADF) has been proposed. Cowan and others proposed the DA adaptive algorithm with offset binary coding for the simple derivation of an algorithm and the use of an odd-symmetry property of adaptive function space (AFS). However, we indicated that a convergence speed of this DA adaptive algorithm degraded extremely by our computer simulations. To overcome these problems, we have proposed the DA adaptive algorithm generalized with two's complement representation and effective architectures. Our DA-ADF has performances of a high speed, small output latency, a good convergence speed, small-scale hardware and lower power dissipation for higher order, simultaneously. In this paper, we analyze a convergence condition of DA adaptive algorithm that has never been considered theoretically. From this analysis, we indicate that the convergence speed is depended on a distribution of eigenvalues of an auto-correlation matrix of an extended input signal vector . Furthermore, we obtain the eigenvalues theoretically. As a result, we clearly show that our DA-ADF has an advantage of the conventional DA-ADF in the convergence speed.

The threshold voltage of Coulomb staircase using organic molecules was analyzed by extending our previous model with only consideration of the metal/organic film interfacial space charge to the generalized one. The generalized model is helpful to examine coupling capacitance in organic double barrier tunneling junction (DBTJ). The current-voltage (I-V) characteristic of metal/polyimide (PI)/rhodamine-dendrimer (Rh-G2)/PI/metal junction was analyzed using this generalized model. The calculation results were in good agreement with our experimental data.

This paper presents a formal verification method based on logic simulation. In our method, some restricted class of circuits which include data paths can be verified without abstraction of data paths by using symbolic values. Our verifier extracts a transition relation from the state graph (given as a specification) which is expressed using symbolic values, and verifies based on simulation using those symbolic values if the circuit behaves correctly with respect to each transition of the specification. If the verifier terminates with "correct," then it can be guaranteed that for any applicable input vector sequence, the circuit and the specification behaves identically. We have implemented the proposed method on a Unix workstation and verified some FIFO and LIFO circuits by using it.

The surface potential built across vacuum deposited phthalocyanine (Pc) films on aluminum electrode was investigated by means of electro-modulation spectroscopy. The sandwich-type cells with thin air gap, which becomes a good insulator were used in order to avoid the influence of charge injection. The existence of the surface potential at the metal/organic-material interface induced 1f referenced electro-reflectance (ER) signals. As a result, the surface potential built across vacuum deposited Pc films on aluminum electrode was estimated to be 1.25 V.

The radix-64 encoding scheme was used to reduce the number of partial products in the 5454 CMOS parallel multiplier. The transistor counts, the chip area and the power-delay product were reduced by 28%, 22%, and 17%, respectively, compared to any of the published 5454 CMOS parallel multipliers. A redundant binary (RB) number system was used to represent any of the 65 multiplying coefficients as a RB number which consists of two of 9 fundamental multiplying coefficients and their complements. The resultant RB partial products were added by using optimized RB adders. The total transistor count of the proposed multiplier was 43,579. The chip area in 0.25 µm CMOS process with 5 metal layers was 0.99 mm2. The power consumption and the multiplication time were 111 mW and 6.9 ns, respectively.

A new four-quadrant (4Q) Multiplier complementally using linear and saturation regions of MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is proposed for the wide dynamic range and superior flexibility of the input range. This multiplier operates in the region except for the threshold voltage VT to zero. The validity of the proposed circuit is confirmed through HSPICE simulation.

We investigated the electrical properties of hole transport materials such as TPD, α-NPD and m-MTDATA using in-situ field effect measurement. TPD, α-NPD and m-MTDATA films showed p-type semiconducting properties, and their electrical parameters such as conductivity, carrier mobility and carrier concentration were obtained. We also examined the effect of the substrate temperature during vacuum deposition and the thermal treatment after deposition, on the electrical parameters of the films. Experimental results showed that conductivity and carrier mobility decreased as the substrate temperature increased over the glass transition temperature. These decreases in conductivity and carrier mobility as a result of thermal treatment appear to be strongly related to the degradation mechanism of organic electroluminescent devices.

This paper proposes a fast method for the calculation of exponential B-splines sampled at regular intervals. This algorithm is based on a combination of FIR and IIR filters which enables a fast decomposition and reconstruction of a signal. When complex values are selected for the parameters of the exponentials, complex trigonometric functions are obtained. Only the real part of these functions are used for the interpolation of real signals, leading less bandlimited signals when they are compared with the polynomial B-spline counterparts. These characteristics were verified with 1-D and 2-D examples. This paper also discusses the effectiveness of exponential B-splines, when they are applied to image processing.

This paper presents a new DSP-oriented code optimization method to enhance performance by exploiting the specific architectural features of digital signal processors. In the proposed method, a source code is translated into the static single assignment form while preserving the high-level information related to loops and the address computation of array accesses. The information is used in generating hardware loop instructions and parallel instructions provided by most digital signal processors. In addition to the conventional control-data flow graph, a new graph is employed to make it easy to find auto-modification addressing modes efficiently. Experimental results on benchmark programs show that the proposed method is effective in improving performance.

The optical pulses of 50 MHz has been obtained from an organic light emitting diode (OLED) based on the Alq3 emissive layer with the active area of 0.01 mm2. We demonstrate that the OLEDs can be applied to fields of optical communication as the electro-optical conversion device for transmitting the signals of moving picture.

Tracking mobile users in cellular wireless networks involves two basic functions: location update and paging. Location update refers to the process of tracking the location of mobile users that are not in conversation. Three basic algorithms have been proposed in the literature, namely the distance-based, time-based, and movement-based algorithms. The problem of minimizing the location update and paging costs has been solved in the literature by considering exponentially distributed Cell Residence Times (CRT) and Inter-Call Time (ICT), which is the time interval between two consecutive phone calls. In this paper we select the movement-based scheme since it is effective and easy to implement. Applying the theory of the delayed renewal process, we find the distribution of the number of cell crossings when the ICT is a mixture of exponentially distributed random variables and the CRT comes from any distribution with Laplace transform. In particular, we consider the case in which the first CRT may have a different distribution from the remaining CRT's, which includes the case of circular cells. We aim at the total cost minimization in this case.

The technique of the digital watermarking is one of the ways to resolve copyright ownership and verify originality of digital contents (e.g. text documents, audio, still images, video, etc.). In this paper, we obtained global robustness and minimal error through using frame based watermarking and including DC and AC coefficients of DCT transform, which extended conventional watermarking method having local robustness and error through using block based and/or AC coefficients only. As a result, the high robustness and quality of our method were proved by several attacks such as lossy image compression, linear filtering, additive noise, scaling, cropping and so on. Watermarks embedded by our method are survived most of JPEG compressions.

In this paper, the efficient signal enhancement scheme for an adaptive antenna array under the Nakagami fading channel is proposed. The proposed signal enhancement scheme is the modified linear signal estimator with Toeplitz Matrix Approximation (TMA) method. The underlying principle of the proposed signal enhancement scheme is to reduce a noise component using not only the Lagrangian method of the constrained minimization but also a signal-plus-noise subspace method. TMA is also used to have the theoretical property of noise-free signal. These functions greatly enhance the performance of an adaptive antenna array by removing the all undesired noise effects from the post-correlation received signal. The proposed signal enhancement scheme is applied at the Wiener Maximal Ratio Combining (MRC) method which has been widely used as the conventional adaptive antenna array. Also, we investigated the effect of the power control error (PCE) for the proposed scheme over the Nakagami multipath fading channel. Several computer simulation examples are provided for illustrating the effectiveness of the proposed scheme.

The adsorption behavior of cytochrome c was investigated using slab optical waveguide (SOWG) absorption spectroscopy at the near ultraviolet region utilizing thin quartz plates as planar waveguides. SOWG absorption spectra of cytochrome c measured at constant time intervals showed significant influence of surface hydrophilicity and solution chemistry on the adsorption of this important heme protein in quartz surface. Being polar and typically amphoteric, the protein preferred adsorption on hydrophilic surface than on hydrophobic surface as implied by the lower absorbance data obtained in the latter than in the former. At lower ionic strength and in the absence of buffer, the protein molecules tend to adsorb on the quartz surface. Plots of near steady-state absorbance versus protein concentration follow hyperbolic pattern in the absence of buffer or at low ionic strength and become more linear as the buffer concentration is increased. The results presented here are explained in terms of the general qualitative understanding of protein adsorption at solid-aqueous interfaces and further aids in elucidating the properties of protein monolayers and films.

The understanding of instruction set usage in typical DOS/Windows applications plays a very important role in designing high performance x86 compatible microprocessors. This paper presents the tools to such analysis, the analysis results, and their implications on the design of a RISC-based superscalar processor for efficient x86 instruction execution. The analyzed results are used to optimize the execution of frequently executed instructions and micro operations.

Nonlinear feedback shift registers (NFSRs), which can generate maximal-period sequences called de Bruijn sequences, are regarded as one-dimensional maps with finite bits by observing states of the registers at each time. Such one-dimensional maps are similar to the Bernoulli map which is a famous chaotic map. This implies that an NFSR is one of finite-word-length approximations to the Bernoulli map. Inversely, constructing such one-dimensional maps with finite bits based on other chaotic maps, we can design new types of NFSRs, called extended NFSRs, which can generate new maximal-period sequences. We design such extended NFSRs based on some well-known chaotic maps, which gives a new concept in sequence design. Some properties of maximal-period sequences generated by such NFSRs are investigated and discussed.

The IETF Mobile IP defines two multicast options: remote subscription (RS) and bi-direction tunneling (BT). In order to synthesize the strong points of these two IETF multicast options, we propose a hybrid approach, mMOM, which selectively uses two IETF multicast options based on the mobility of mobile hosts. Whenever a mobile host requests its first registration to a certain foreign agent, the corresponding foreign agent starts the service using the BT option. Afterwards, if it requests re-registration to the same foreign agent, the foreign agent considers it to be relatively immobile and continues services using the RS option. We propose a new metric to compare heterogeneous algorithms. Simulation results show that our approach outperforms all others.

This letter presents the empirical error performance of combining method of a binary numerical code and a single error correcting code on Gaussian channel by belief propagation (BP) decoding algorithm. The numerical codes mentioned here are constructed with any symbol value and have the parity check matrices in reduced-echelon form whose elements are binary (0 and 1). The simulation results show that the method yields good decoding error performance for medium code lengths.

This letter treats computational complexity of bounded asymmetric choice (AC) net. AC net is a subclass of Petri net that properly includes the class of well-known extended free choice net. It is shown that satisfiability problem of Boolean expressions is polynomial time reducible to liveness problem of bounded AC nets. This implies that the problem is NP-hard.