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.

Compared with much research in the spatial-domain and transform-domain watermarking techniques, VQ-based watermarking technique has not been fully treated. A digital image watermarking scheme based on vector quantisation (VQ) is proposed to improve the degree of spreading watermark information. By partitioning the codebook into 3 groups, the scheme tries to embed one binary information for each block. The scheme spreads the watermark information almost evenly over the image with little extra distortion. The experimental results prove the efficiency and effectiveness of the scheme.

Transmit beamforming is a promising way to increase the downlink capacity of wireless networks. Since all users are coupled via their radiation patterns, the beamforming vectors must be optimized along with power control. It is necessary to balance the signal-to-interference levels according to individual QoS requirements. This problem leads back to the minimization of the infinity-norm of a certain vector and has first been studied by Gerlach and Paulraj in [1]. It has been assumed that the optimum solution can be obtained by minimizing the 1-norm instead, thereby leading to a new problem, which is generally easier to handle. The analytical and numerical results in this paper, however, indicate that this conjecture is generally not valid. We characterize the case where the 1-norm solution also solves the infinity-norm problem. In particular, it is shown that for the special case of a 2-user scenario, both optimization problems are indeed equivalent and a closed-form solution can be given. The analytical results provide new insights into the problem of coupled downlink beamforming and offer a useful approach to the design of efficient and reliable algorithms.

A new type of electromagnetic vibration transducer for use in an IME (implantable middle ear) system is presented and evaluated by in-vitro experiment. Because the new designed transducer includes two magnets glued together with the same pole facing inside the coil, it can reduce the interference from an environmental magnetic field. And the proposed transducer exhibits a high vibration efficiency and wide frequency response. Using dead human's temporal bone, in-vitro experiments were carried out and the results showed that the proposed vibration transducer will be properly used to implantable middle ear for mild to severe hearing loss patients.

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.

A drain avalanche hot carrier lifetime model including a body effect caused by secondary hot electrons has been developed. It has been confirmed that the proposed model fits a wide range of experimental data using a small number of parameters. The model provides a practical modeling methodology for reliability simulation based on parameter extraction at maximum substrate current conditions alone. Simulation accuracy produced by the methodology has been experimentally verified using ring oscillators including NAND gates. It has been demonstrated that simulation accuracy of degradations has become by 0.34 decade better using the new methodology than using that based on the conventional τId/W-Isub/Id model.

A generic multilevel quality-of-service (QoS) model for distributed multimedia applications is presented. QoS mapping mechanisms are required to translate the QoS parameters among the hierarchical levels. One QoS mapping mechanism based on the spline functions is proposed, hence two splines are compared. One is natural splines and the other is B-splines. QoS measurement experiments were conducted, and it is found that the B-splines give more accurate mapping results than the natural splines once the knots for the splines are selected appropriately.

Wavelength division multiplexed (WDM) routed optical networks represent the direction towards future high-capacity wide-area network applications. A serious issue in WDM-routed networks, though, is light-path allocation which requires a combination of optical routing and wavelength assignment. While near-optimal-routing and wavelength-assignment algorithms aimed at minimizing network wavelength requirements have been reported, the practicability of wavelength-routed optical networks depends on the number of wavelengths required to satisfy a given traffic demand. In this paper, we proposed two symmetrical routing and wavelength-assignment methods for optical networks with a Grid or ShuffleNet physical topology. Here, we consider the case of non-adaptive wavelength routing systems, where the operations performed in nodes are independent of the network traffic load. In this case, the routing differs somewhat from that in adaptive routing networks where the routing function may produce different results at different times. The path followed by a wavelength never changes in non-adaptive wavelength-routing networks. When all N(N-1) node-pairs are to be connected, our methods lower the wavelength requirement to (or close to) its calculated minimum. Symmetry is a basic feature of both these regular topologies, but there are differences in the features within the topologies. Our goal has been to try to make use of the symmetry, and the differences in the native symmetry features, of these regular topologies to yield a lower wavelength requirement.

This paper proposes a new blocking artifact reduction algorithm using an adaptive filter based on classifying the block boundary area. Generally, block-based coding, such as JPEG and MPEG, introduces blocking and ringing artifacts to an image, where the blocking artifact consists of grid noise, staircase noise, and corner outliers. In the proposed method, staircase noise and corner outliers are reduced by a 1D low-pass filter. Next, the block boundaries are divided into two classes based on the gradient of the pixel intensity in the boundary region. For each class, an adaptive filter is applied so that the grid noise is reduced in the block boundary regions. Thereafter, for those blocks with an edge component, the ringing artifact is removed by applying an adaptive filter around the edge. Finally, high frequency components are added to those block boundaries where the natural characteristics have been lost due to the adaptive filter. The computer simulation results confirmed a better performance by the proposed method in both the subjective and objective image qualities.

Metal nanostructure of organic/metal interface showing photocurrent multiplication phenomenon more than 105-fold was investigated. Au films deposited on organic films were revealed to be a gathering of nanoparticles and the multiplication rate can be tuned by the particle size. Spatial gaps formed between Au sphere and organic surface, which provide the hole accumulation sites (structural trap), was concluded to be indispensable for the photocurrent multiplication.

We have developed a 22 digital optical switch (DOS) composed of four 12 DOS elements and a thermo-optic wavelength tunable filter using silicone resin waveguides. The 22 DOS operated with a switching power of 380 mW, a very low crosstalk of less than -60 dB, and a low insertion loss of less than 2.5 dB at 1.55 µm. We have also developed two types of polymer thermo-optic wavelength tunable filter with a pair of triangular phase shifters. One filter is designed for a large-scale WDM system (32 channels, 0.8 nm spacing) and the other for a small-scale WDM system (10 channels, 0.8 nm spacing). We optimized the arrayed waveguide number, reducing the operating power required by these filters. Moreover, they both operated with a low crosstalk of < -25 dB.

Angle-multiplexed holography using four-wave mixing (4WM) was demonstrated with a monolithic photorefractive carbazole trimer. We measured the diffraction efficiency as a function of incident angle of the read beam. The cross-talk was almost negligible at the Bragg angle mismatch of 1. Two figure images were recorded with the different incident angle of the reference beam in the photorefractive carbazole trimer film, and were read out independently by illuminating with the read beam which counter-propagated to the corresponding reference beam.

Organic nonlinear optical crystal 4-(p-dimethylaminostyryl)-1-methylpridinium tosylate (DAST) has a larger electro-optic (EO) coefficient than that of LiNbO3 crystal. Thus, DAST is a promising material for EO switching device. To use its large EO coefficient effectively, a waveguide structure is desirable. We have successfully fabricated two types of DAST crystal optical channel waveguide. One is a serially grafted waveguide combining a DAST and a transparent polymer by using the combination of standard photo-process and reactive ion-etching (RIE). Because DAST has large optical loss, parts of the waveguide should be composed of transparent polymer with a serially grafted structure with DAST. This structure reduced not only a propagation loss but also input/output losses. This serially graft waveguide fabrication technique for active organic crystal is available to many types of crystals with device function. The other is a channel waveguide made by a photo-bleaching technique. The cladding part of DAST waveguide was photo-bleached by irradiation of UV light. Under and over cladding layer were composed with UV-cured resin that did not dissolve the DAST crystal. This technique is very convenient for making DAST waveguide because of its simple procedure to make core-cladding structure of DAST compared to standard photo-process and RIE.

Polyurea thin films containing azo-based nonlinear optical (NLO) chromophore were prepared by co-deposition of 4,4'-diphenylmethane diisocyanate and 2,4-diamino-4'-nitroazobenzene monomers using the ionization-assisted method. The co-deposited film reacted to form polyurea after annealing in the air. The dichroic optical absorption spectra indicated the preferential orientation of dipole moments in the as-deposited film. The substrate bias voltage influenced the optical anisotropy. Maker fringe measurement showed that the films have NLO activity without the poling process.

We propose a new effective method of managing flash memory space for flash memory-specific file systems based on a log-structured file system. Flash memory has attractive features such as non-volatility and fast I/O speed, but it also suffers from inability to update in situ and from limited usage (erase) cycles. These drawbacks necessitate a number of changes to conventional storage (file) management techniques. Our focus is on lowering cleaning cost and evenly utilizing flash memory cells while maintaining a balance between these two often-conflicting goals. The proposed cleaning method performs well especially when storage utilization and the degree of locality are high. The cleaning efficiency is enhanced by dynamically separating cold data and non-cold data, which is called 'collection operation.' The second goal, that of cycle-leveling, is achieved to the degree that the maximum difference between erase cycles is below the error range of the hardware. Experimental results show that the proposed technique provides sufficient performance for reliable flash storage systems.

Semistructured data comprises irregular structure and has no a-priori database schema, therefore we encounter several problems such as inefficient data retrieval and wasteful data storage. To cope with such problems, some schema extraction algorithms over semistructured data have been proposed, in which data is modeled as an unordered tree. However, the order of elements is indispensable for document data, therefore we consider extracting an optimal database schema over an ordered tree. We consider an optimization problem to extract a smallest database schema such that the density of each class is no less than a given threshold, where the density of a class represents a similarity between the type of the class and those of the objects in the class. We first prove that the corresponding decision problem is strongly NP-complete, and show that another version of the problem is strongly NP-hard and belongs to Δ2 P. Then we show that for any r < 3/2, there is no polynomial-time r-approximation algorithm that solves the optimization problem unless P = NP. Finally, we propose a kind of class called bounded class that can be constructed efficiently, then show a polynomial-time algorithm for constructing a database schema by using bounded classes.

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.

An efficient algorithm is proposed for the adaptive sizing of a tracking window in correlation-based video tracking. Since a tracking window specifies a support region when estimating a target displacement, the ability to adapt the window size relative to a moving target significantly influences the performance of video tracking. The basic strategy of the proposed algorithm is to maintain the occupancy rate of the target in the tracking window within a specified range. As such, the proposed algorithm measures the occupancy rate using the ratio of the power of the spatial gradients in the edge subwindows, which edge the tracking window, to that in the tracking window. In addition, the level of any complex background and additive white noise is also evaluated to reduce their effect on the gradients. Experimental results using various artificial and real sequences confirm that the proposed algorithm can effectively adjust a tracking window to a moving target and is robust to a complex background and noise.

This paper discusses a new type of semi-supervised document clustering that uses partial supervision to partition a large set of documents. Most clustering methods organizes documents into groups based only on similarity measures. In this paper, we attempt to isolate more semantically coherent clusters by employing the domain-specific knowledge provided by a document analyst. By using external human knowledge to guide the clustering mechanism with some flexibility when creating the clusters, clustering efficiency can be considerably enhanced. Experimental results show that the use of only a little external knowledge can considerably enhance the quality of clustering results that satisfy users' constraint.

Timed token protocols inadequately provide periodic communication service, although this is crucial for hard real time systems. We propose an algorithm to guaranteeing periodic communication service on a timed token protocol network. In this approach, we allocate bandwidth to each node so that the summation of bandwidth allocations is Target Token Rotation Time (TTRT). If a node cannot consume the allocated time, the residual time is made concession to other nodes for non-periodic service using a timer which contains the unused time value and is appended to the token. This algorithm can always guarantee transmission of real-time messages before their deadlines when the network utilization is less than 50%.