The most important function of a router is to perform IP lookup that determines the output ports of incoming IP packets by their destination addresses. Hence, IP lookup is one of the main issues in implementing high-speed routers. The IP lookup algorithm implemented in IQ2200 Chipset with two-level table architecture can efficiently use memory. However, it wastes processor resource for full re-construction of the forwarding tables whenever every route insertion/deletion is requested. In order to improve the utilization of processor resource, we propose an IP lookup algorithm with three-level table architecture for high-speed routers. We evaluate the performance of the proposed algorithm in terms of the memory size required for storing lookup information and the number of memory access in constructing forwarding tables. Being compared with the IQ2200 scheme, the proposed scheme can reduce the number of memory access up to 99% even though it needs about 16% more memory.

In this paper, a novel type of the step-up high frequency transformer linked full-bridge soft-switching phase-shift PWM DC-DC power converter with ZVS and ZCS bridge legs is proposed for small scale fuel cell power generation systems, automotive AC power supplies. A tapped inductor filter with a freewheeling diode is implemented in the proposed soft-switching DC-DC power converter to minimize the circulating current in the high-frequency step-up transformer primary side and high-frequency inverter stage. Using a tapped inductor filter with a freewheeling diode makes possible to reduce the circulating current without any active switches and theirs gate-drive circuits. The operating principle of the proposed DC-DC power converter with each operation mode during a half cycle of the steady state operation is explained. The optimum design of the tapped inductor turns ratio is described on the basis of the circuit simulation results. Developing 1 kW 100 kHz prototype with power MOSFETs and 36 V DC source verifies the practical effectiveness of the proposed soft-switching DC-DC power converter. The actual efficiency of the proposed DC-DC power converter is obtained 94% for the wide load and output voltage variation ranges.

Radio frequency (RF) microwave can be used to predict glucose concentration in a sample. This paper presents preliminary results in determining the concentration by measuring relative permittivity in the solutions of distilled water, saline, human serum, and human blood containing glucose. In the experiments, sensitivity for detecting glucose concentration in blood solutions was almost 57 mg/dl at the frequency of approximately 5.8 GHz.

Checking the equivalence of two Boolean functions under permutation of the variables is an important problem in the synthesis of multiplexer-based field-programmable gate arrays (FPGAs), and the problem is known as Boolean matching. This paper presents an efficient breadth-first search technique for computing a canonical form--namely P-representative--of Boolean functions under permutation of the variables. Two functions match if they have the same P-representative. On an ordinary workstation, on the average, the method requires several microseconds to check the Boolean matching of functions with up to eight variables against a library with tens of thousands of cells.

A stability of the cascade two-stage Power-Factor-Correction converter is investigated. The first stage is boost PFC converter to achieve a near unity power factor and the second stage is forward converter to regulate the output voltage. Previous researches studied the system using linear analysis. However, PFC boost converter is a nonlinear circuit due to the existence of the multiplier and the large variation of the duty cycle. Moreover, the effect of the second stage DC/DC converter on the first stage PFC converter adds more complexity to the nonlinear circuit. In this issue, low-frequency instability has been detected in the two-stage PFC converter assuring the limitation of the prior linear models. Therefore, nonlinear model is proposed to detected and explain these instabilities. The borderlines between stable and unstable operation has been made clear. It is cleared that feedback gains of the first stage PFC and the second stage DC/DC converters are the main affected parts to the total system stability. Then, a simplified nonlinear model is provided. Experiment confirm the two models with a good agreement. These nonlinear models have introduced new PFC design scheme by choosing the minimum required output capacitor and the feedback loop design.

Borrowing the notion of instantaneous frequency that was developed in the context of time-frequency signal analysis, an instantaneous frequency amplitude spectrum (IFAS) is introduced for estimating fundamental frequency of speech signal in both noiseless and adverse environments. We define harmonicity measure as a quantity that indicates degree of periodical regularity in the IFAS and that shows substantial difference between periodic signal and noise-like waveform. The harmonicity measure is applied to estimate the existence of fundamental frequency. We provide experimental examples to demonstrate the general applicability of the harmonicity measure and apply the proposed procedure to Japanese continuous speech signals. The results show that the proposed method outperforms the conventional methods with or without the presence of noise.

Thin film of polyurethane having metal complex was prepared by vapor deposition polymerization of bis (5,8-dihydroxyquinoline) zinc (ZnHq2) and 4, 4'-diphenylmethane diisocyanate monomers. The film was applied for the electron-transporting emissive layer of the organic light emitting diode. The deposition-polymerized film was found to give higher quantum efficiency of luminescence than the ZnHq2 monomer film.

Loss compensation in a RF CMOS active inductor with using a capacitor is proposed. This simple compensation technique yields a negative conductance characteristic that can compensate for the constant internal loss of active devices. Simulation results show that the inductor obtains a maximum Q-value of 1.2E8, an inductance value in the range of 50 nH to 450 nH, and a 1.4E-6 Ω of minimum total equivalent loss in the range of 0.6 GHz to 1.3 GHz.

A smell reproduction technique is useful in the field of virtual reality. We have developed the system called an odor recorder for reproducing the smell recorded using the odor sensing technique. We proposed the new type of the odor recorder using the inkjet devices together with a mesh heater. Droplets with tiny volume were forcibly evaporated to generate smell rapidly and reproducibly. Moreover, the mesh heater was directly connected to the sensors without plumbing tubes and the sensors were placed away from the wall of sensor cell. The recording time of the odor with high odor intensity became much shorter than that of the previous system. Then, the recipe of jasmine scent composed of benzyl acetate and Ylang Ylang was successfully determined using the proposed system.

The methodologies of product-line engineering emphasize proactive reuse to construct high-quality products more quickly that are less costly. Requirement engineering for software product families differs significantly from requirement engineering for single software products. The requirements for a product line are written for the group of systems as a whole, with requirements for individual systems specified by a delta or an increment to the generic set. Therefore, it is necessary to identify and explicitly denote the regions of commonality and points of variation at the requirement level. In this paper, we suggest a method of producing requirements that will be a core asset in the product line. Briefly, requirements for families of similar systems (i.e. domain) are collected and generalized which are then analyzed and modeled. The domain requirement as a core asset explicitly manages the commonality and variability. Through this method, the reuse of domain requirements can be enhanced. As a result, the cost and time of software development can be reduced and the productivity increased while significantly reducing error in the requirements.

To implement a fast and reliable question-answering system in Korean, we propose a two-pass answer indexer using co-occurrence information between answer candidates and adjacent content words. The two-pass indexer scans documents twice for obtaining local scores and global scores. Then, the two-pass indexer calculates the degrees of association between answer candidates and co-occurring content words. Using this technique, the proposed QA system shortens the response time and enhances the precision.

A new analytical approach which reveals relationships between resonator parameters (unloaded Q-factor, coupling coefficient, and loaded Q-factor) and phase noise in microwave negative-resistance oscillators is presented. On the basis of Kurokawa's theory, this approach derives analytical expressions for the phase noise as a function of the resonator parameters (with particular emphasis on the coupling coefficient). Two types of negative-resistance oscillators--classified according to the manner in which the resonator is used in a circuit--are analyzed. These analyses use realistic circuit configurations and design procedures. The passive network connecting the active device and the resonator, which is shown to have important effects on the above-mentioned relationship, is taken into account. Validity of the new approach is verified through harmonic-balance simulations. The presented analytical approach can provide useful guidelines for choosing the resonator parameters, especially the value of the coupling coefficient, when designing microwave negative-resistance oscillators.

It is important to predict serious deterioration of telecommunication quality. This paper investigates predicting such serious events by analyzing only a "short" period (i.e., a "small" amount) of teletraffic data. To achieve this end, this paper presents a method for analyzing the tail distributions of teletraffic state variables, because tail distributions are suitable for representing serious events. This method is based on Extreme Value Theory (EVT), which provides a firm theoretical foundation for the analysis. To be more precise, in this paper, we use throughput data measured on an actual network during daily busy hours for 15 minutes, and use its first 10 seconds (known data) to analyze the tail distribution. Then, we evaluate how well the obtained tail distribution can predict the tail distribution of the remaining 890 seconds (unknown data). The results indicate that the obtained tail distribution based on EVT by analyzing the small amount of known data can predict the tail distribution of unknown data much better than methods based on empirical or log-normal distributions. Furthermore, we apply the obtained tail distribution to predict the peak throughput in unknown data. The results of this paper enable us to predict serious deterioration events with lower measurement cost.

In this paper we present the exact expressions for the bit error probability over a Gaussian noise channel of coded QAM using single error correcting integer codes. It is shown that the proposed integer codes have a better performance with respect to the lower on the bit error probability for trellis coded modulation.

Liquid-crystal devices with in-plane switching electrodes (IPS-LCD) are superior to twisted nematic ones in their wider range of viewing angle, but show serious color shift with viewing angle. The color shift is a phenomenon governed by the three-dimensional orientation of liquid-crystal molecules. In order to evaluate such effects numerically, light wave propagation in the IPS-LCD is studied using a two-dimensional finite-difference time-domain method, where all six components of electromagnetic field are analysed and the three-dimensional properties of liquid-crystal materials are taken into account through the dielectric tensor. The computational space termination is provided by a combination of the uniaxial perfectly matched layer and periodic boundary conditions. It is found for the first time numerically that the color shift effects strongly depend on the asymmetrical profile of liquid-crystal orientation, which is originated from the small pretilt angle.

AF service class in Diffserv by realizes minimum bandwidth guarantee with the use of differentiated drop precedence property marked on each packet. In the context of a multiple domains environment, however, QoS of individual flow is not always preserved due to the re-marking behavior forced at the domain boundaries. Focusing on this point, this paper proposes new packet re-marking schemes that can improve the per-flow QoS of AF service traversing multiple domains. The basic concept of the schemes distinguishes packets re-marked to out-of-profile at the domain boundaries from those already marked as out-of-profile at the time of entering the network, and allows the re-marked packet to recover back to in-of-profile, thus regaining its rightful QoS within the networks. The performance of the proposed schemes is evaluated through simulation. The results on UDP flows show the effectiveness of the proposed schemes for reducing packet losses on the flow through multiple domains and preserving fairness between flows. Simulations on TCP flows show that the proposed schemes improve the throughput of the flows through multiple domains. The proposed scheme is especially effective on the transfer time of short TCP flows such as Web traffic, whose throughput is affected more seriously by a single packet loss due to its flow control mechanisms.

FEC (Forward Error Correction) is widely used to recover packet loss over the Internet since it does not involve additional network delay. However, FEC still needs much additional network bandwidth for redundancy, and does not consider the priority or the importance of video frames to generate redundant data. In this paper, we present Periodic FEC (PFEC) to make up for the shortcomings of FEC. PFEC divides frames into high-priority frames and low-priority frames, and gives redundancy only to high-priority frames. As specific examples, we describe two types of PFEC: Media-Independent PFEC and Media-Dependant PFEC. Moreover, based on the two-state continuous time Markov chain, we propose redundancy control algorithms of the PFEC schemes that can adjust the amount of redundancy to optimal levels depending on network loss conditions. For better performance, we also consider UEP (Unequal Error Protection) based on PFEC that gives redundancy to low-priority frames as well as high-priority frames. Experimental results show that compared with FEC, PFEC reduces the amount of redundancy considerably but degrades PSNR slightly, and UEP based on PFEC economizes redundancy without the degradation of the PSNR.

In wide-area wireless access systems such as satellite communications systems and stratospheric platform systems, electric power supplies for radio communications are realized using solar photovoltaic cells and/or fuel cells. However, the on-board weight limits restrict the number of cells that can be equipped. In addition, the transmission power of such systems is limited taking account of issues and regulations on sharing the same frequency band with other systems. Hence, both the frequency band and electric power is limited, which are crucial radio resources for those systems. Although radio channel allocation methods taking account of the frequency constraint only or the power constraint only have been proposed, radio channel allocation methods taking account of both constraints simultaneously have been insufficiently studied. This paper proposes a radio channel allocation method that provides global optimum allocation results by utilizing the linear programming method. The proposed method has features such that the method first allocates radio channels in proportion to the traffic demand distributed over the service coverage area and then maximizes the total radio channels allocated to systems. Numerical results are presented for a stratospheric platform system that covers an area of Japan, as an example, to demonstrate that the proposed method optimally allocates radio channels taking account of both constraints while efficiently allocating excess resources. In addition, whether a system reaches either the frequency or power limit can be estimated, by investigating the radio channel allocation results. Furthermore, enhanced linear programming models based on a method aiming at practical use of the radio channel allocation results in operation are also introduced. The enhanced model is demonstrated to work effectively to avoid unbalanced radio channel allocations over geographical areas. The proposed method and linear programming models are useful not only for making pre-plans but also for determining the amount of necessary frequency and power resources in designing systems.

Quantum dots are one of the possible building blocks for the quantum computing device. We discuss on use of carbon nanotubes for fabrication of the quantum dot, in terms of their unique physical properties and energy scales which might be advantageous for functionalities of the quantum computing device. Simple schemes of a charge qubit and a spin qubit are described, followed by the current status of the fabrication and transport measurements of the nanotube quantum dot. Based on the basic properties and the estimated energy scales of the dot, we discuss advantages and problems of the carbon nanotube for the quantum computing device. The nanotube quantum dot may have a great advantage for the spin qubit.

A new approach for ultra-low-power LSIs based on quantum devices is presented and its present status and critical issues are discussed with a brief background review on the semiconductor nanotechnology. It is a hexagonal binary decision diagram (BDD) quantum logic circuit approach suitable for realization of ultra-low-power logic/memory circuits to be used in new applications such as intelligent quantum (IQ) chips embedded in the ubiquitous network environment. The basic concept of the approach, circuit examples showing its feasibility, growth of high density nanostructure networks by molecular beam epitaxy (MBE) for future LSI implementation, and the key processing issues including the device isolation issue are addressed.